Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparis...Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparison between direct heat exchange(DHE)and open-cycle mechanical heat pump(MHP)under various operating conditions is carried out in this work.The price ratios R_(ES)(electricity to steam)and R_(HS)(hot water to steam)are introduced to quantify regional impacts and conduct quantitative analysis.A semi-empirical formula is obtained to explore the exergoeconomic performance of the two systems.For waste heat within 373.15-423.15 K,the exergy efficiency of the DHE with a temperature difference of 10-90 K is always lower than that of the MHP with a temperature lift of 10-50 K.The economic performance of the two systems has a break-even point,depending on the operating parameters and relative prices of electricity,steam,and hot water.Under the average R_(ES)(3.8)in China,if R_(HS)is higher than 0.748,the annual revenue of the DHE is always higher,whereas the MHP is more economical when R_(HS)is lower than 0.110.In regions where R_(ES)is higher than 4.353,the annual revenue of the MHP will be negative in some cases.展开更多
The COVID-19 pandemic has stalled and rolled back progress on Sustainable Development Goals(SDGs).Ecosys-tem services(ESs),defined as the contributions of ecosystems to human well-being,underpin the achievement of SDG...The COVID-19 pandemic has stalled and rolled back progress on Sustainable Development Goals(SDGs).Ecosys-tem services(ESs),defined as the contributions of ecosystems to human well-being,underpin the achievement of SDGs.To promote SDG achievement in post-pandemic era,we teased out the links between ESs and SDGs while examining the impact of COVID-19.We found that ESs benefited all SDGs,yet man-made pressures led to degra-dation of ecosystems and their services.There is broad consensus that the virus lurks in degraded ecosystems and generates spillover due to human interference.The pandemic and global lockdown/restriction disrupted the flow of ESs and altered human ESs demand,threatening the efforts for the SDGs.We suggested:1)to study the association and traceability of ESs-SDGs under the pandemic;2)to prioritize pressing issues such as health care,livelihood,and resource security and in the long run,we should promote human-nature harmony to achieve the SDGs;and 3)to enhance ESs and to promote the SDGs through local community efforts,ESs accounting,and ecosystem restoration.This paper provides insights into the importance of ESs to the SDGs and the ways to integrate ESs into socio-economic development to promote the SDG achievement after the pandemic.展开更多
The trade-offs and supply-demand relations of ecosystem services(ES)are at the frontier of geographical and ecological studies.However,previous studies have focused on either trade-offs or the supply-demand aspects,wh...The trade-offs and supply-demand relations of ecosystem services(ES)are at the frontier of geographical and ecological studies.However,previous studies have focused on either trade-offs or the supply-demand aspects,while ES conflicts and supply/demand contradictions have not been comprehensively examined.The relation-ship between ES trade-offs and supply-demand is logically valid and studying the coupling of both can provide approaches for simultaneously alleviating ES conflicts and supply-demand contradictions.This study,based on a review of previous analyses of ES trade-offs and supply-demand dynamics,proposes a new analytic framework to couple them.First,we define two types of trade-offs based on the directions of growth or decline of the two ser-vices.We also define the supply-demand balance area and the supply-demand risk area according to the ES flow characteristics.Second,the mechanisms driving ES trade-offs are clarified,and land-use scenarios are set based on the mechanisms.Third,the supply-demand spatial characteristics of ES are analyzed,and supply-demand risk areas are identified.Finally,scenario iterations are performed to minimize the supply-demand risk area at an acceptable trade-offintensity to identify an optimal land use plan,which simultaneously alleviates ES conflicts and supply-demand contradictions.This analytic framework offers new opportunities for improving sustainable ecosystem management.展开更多
Particle based methods can be used for both the simulations of solid and fluid phases in multiphase medium, such as the discrete-element method for solid phase and the smoothed particle hydrodynamics for fluid phase. ...Particle based methods can be used for both the simulations of solid and fluid phases in multiphase medium, such as the discrete-element method for solid phase and the smoothed particle hydrodynamics for fluid phase. This paper presents a computational method combining these two methods for solid-liquid medium. The two phases are coupled by using an improved model from a reported Lagrangian-Eulerian method. The technique is verified by simulating liquid-solid flows in a two-dimensional lid-driven cavity.展开更多
Mapping spatiotemporal land cover changes offers opportunities to better understand trends and drivers of envi-ronmental change and helps to identify more sustainable land management strategies.This study investigates...Mapping spatiotemporal land cover changes offers opportunities to better understand trends and drivers of envi-ronmental change and helps to identify more sustainable land management strategies.This study investigates the spatiotemporal patterns of changes in land covers,forest harvest areas and soil erosion rates in Nordic countries,namely Norway,Sweden,Finland,and Denmark.This region is highly sensitive to environmental changes,as it is experiencing high levels of human pressure and among the highest rates of global warming.An analysis that uses consistent land cover dataset to quantify and compares the recent spatiotemporal changes in land cover in the Nordic countries is missing.The recent products issued by the European Space Agency and the Copernicus Climate Change Service framework provide the possibility to investigate the historical land cover changes from 1992 to 2018 at 300 m resolution.These maps are then integrated with time series of forest harvest areas be-tween 2004 and 2018 to study if and how forest management is represented in land cover products,and with soil erosion data to explore status and recent trends in agricultural land.Land cover changes typically involved from 4%to 9%of the total area in each country.Wetland showed the strongest reduction(11,003 km^(2),−11%of the wetland area in 1992),followed by forest(8,607 km^(2),−1%)and sparse vegetation(5,695 km^(2),−7%),while agriculture(15,884 km^(2),16%)and settlement(3,582 km^(2),84%)showed net increases.Wetland shrinkage dominated land cover changes in Norway(5,870 km^(2),−18%),followed by forest and grassland with a net gain of 3,441 km^(2)(3%)and 3,435 km^(2)(10%),respectively.In Sweden,forest areas decreased 13,008 km^(2)(−4%),mainly due to agriculture expansion(9,211 km^(2),29%).In Finland,agricultural areas increased by 5,982 km^(2)(24%),and wetland decreased by 6,698 km^(2)(−22%).Settlement had the largest net growth in Denmark(717 km^(2),70%),mainly from conversion of agriculture land.Soil erosion rates in Nordic countries are lower than the global average,but they are exacerbating in several locations(especially western Norway).The integration of the land cover datasets with maps of forest harvest areas shows that the majority of the losses in forest cover due to forestry operations are largely undetected,but a non-negligible share of the forest-to-agriculture(up to 19%)or forest-to-grassland(up to 51%)transitions overlap with the harvested sites.Forestry activity in the study region primarily involves small-scale harvest events that are difficult to be detected at the 300 m resolution of the land cover dataset.An accurate representation of forest management remains a challenge for global datasets of land cover time series,and more interdisciplinary international efforts are needed to address this gap.Overall,this analysis provides a detailed overview of recent changes in land cover and forest management in Nordic countries as represented by state-of-the-art global datasets,and offers insights to future studies aiming to improve these data or apply them in land surface models,climate models,landscape ecology,or other applications.展开更多
An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when th...An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when the sampling is stopped. CFD simulations using the commercial software Ansys CFX were carried out for single phase gas flow to analyze the non-standard design. Pitot tube velocity calculations and isokinetic sampling conditions were studied. The predicted results were compared against theoretical velocity profiles from the literature and with gas single phase experimental data acquired in a horizontal 49 m long steel pipeline with an internal diameter of 69 mm. The experiments were done by using a dense gas (SF6) at 7 bara. An asymmetry of the experimental velocity profiles reproduced with the numerical simulations. The CFD simulations made it possible to verify the design and predict and correct an installation problem.展开更多
Revegetation of former agricultural land is a key option for climate change mitigation and nature conservation.Expansion and abandonment of agricultural land is typically influenced by trends in diets and agricultural...Revegetation of former agricultural land is a key option for climate change mitigation and nature conservation.Expansion and abandonment of agricultural land is typically influenced by trends in diets and agricultural inten-sification,which are two key parameters in the Shared Socioeconomic Pathways(SSPs).Datasets mapping future land dynamics under different SSPs and climate change mitigation targets stem from different scenario assump-tions,land data and modelling frameworks.This study aims to determine the role that these three factors play in the estimates of the evolution of cropland and pastureland in future SSPs under different climate scenarios from four main datasets largely used in the climate and land surface studies.The datasets largely agree with the rep-resentation of cropland at present-day conditions,but the identification of pastureland is ambiguous and shows large discrepancies due to the lack of a unique land-use category.Differences occur with future projections,even for the same SSP and climate target.Accounting for CO_(2)sequestration from revegetation of abandoned agri-cultural land and CO_(2)emissions from forest clearance due to agricultural expansion shows a net reduction in vegetation carbon stock for most SSPs considered,except SSP1.However,different datasets give differences in estimates,even when representative of the same scenario.With SSP1,the cumulative increase in carbon stock until 2050 is 3.3 GtC for one dataset,and more than double for another.Our study calls for a common classifica-tion system with improved detection of pastureland to harmonize projections and reduce variability of outcomes in environmental studies.展开更多
Using biomass from dedicated crops for energy production and natural vegetation regrowth are key elements in future climate change mitigation scenarios.However,there are still uncertainties about the mitigation potent...Using biomass from dedicated crops for energy production and natural vegetation regrowth are key elements in future climate change mitigation scenarios.However,there are still uncertainties about the mitigation potentials that can be achieved by the different land-based systems and how they perform relative to each other.In this study,we use harmonized future land use datasets to identify global land areas dedicated to second generation bioenergy crop production in 2050 under different climate scenarios.We then assess the global climate change mitigation potentials of using biomass for producing bioethanol with(BECCS)or without carbon capture and storage,biochar,or a synthetic fuel(e-methanol).For the latter,the electricity required to produce hydrogen for e-methanol synthesis is sourced from either wind power or the projected average electricity mix in 2050.Mitigation potential from natural regrowth on the identified land is also quantified.For all the cases,we modelled emissions of greenhouse gases from the life-cycle stages and use parameterized models to estimate local biomass growth rates.The identified land areas range from 1.95 to 13.8 million hectares and can provide from 30 to 178 mega ton(Mt)dry biomass annually from dedicated crops.Climate change mitigation potentials range from 11 to 257 MtCO_(2)-eq.yr^(−1),depending on technological option and land availability.The largest mitigation is delivered by BECCS,but e-methanol can achieve similar findings when hydrogen is sourced from wind power.If hydrogen is produced from grid electricity,e-methanol can result in net positive emissions.E-methanol can also deliver more final energy than bioethanol(4.04 vs.1.27 EJ yr^(−1)).Natural vegetation regrowth can generally achieve higher mitigation than bioethanol,but less than biochar.An optimal combination of BECCS and natural vegetation regrowth can achieve a larger mitigation,up to 281 MtCO_(2)-eq.yr^(−1),indicating that integrated solutions can help to achieve successful land management strategies for climate change mitigation.展开更多
The development and deployment of Carbon dioxide Capture and Storage （CCS） technology is a cornerstone of the Norwegian government＇s climate strategy. A number of projects are currently evaluated/planned along the ...The development and deployment of Carbon dioxide Capture and Storage （CCS） technology is a cornerstone of the Norwegian government＇s climate strategy. A number of projects are currently evaluated/planned along the Norwegian West Coast, one at Tjeldbergodden. COe from this project will be utilized in part for enhanced oil recovery in the Halten oil field, in the Norwegian Sea. We study a potential design of such a system. A combined cycle power plant with a gross power output of 832 MW is combined with CO2 capture plant based on a post-combustion capture using amines as a solvent. The captured CO2 is used for enhanced oil recovery （EOR）. We employ a hybrid life-cycle assessment （LCA） method to assess the environmental impacts of the system. The study focuses on the modifications and operations of the platform during EOR. We allocate the impacts connected to the capture of CO2 to electricity production, and the impacts connected to the transport and storage of CO2 to the oil produced. Our study shows a substantial reduction of the greenhouse gas emissions from power production by 80% to 75 g·（kW·h）^-1. It also indicates a reduction of the emissions associated with oil production per unit oil produced, mostly due to the increased oil production. Reductions are especially significant if the additional power demand due to EOR leads to power supply from the land.展开更多
The implementation of strategies to achieve the Sustainable Development Goals(SDGs)is frequently hindered by potential trade-offs between priorities for either environmental protection or human well-being.However,ecos...The implementation of strategies to achieve the Sustainable Development Goals(SDGs)is frequently hindered by potential trade-offs between priorities for either environmental protection or human well-being.However,ecosystem services(ES)-based solutions can offer possible co-benefits for SDGs implementation that are often overlooked or underexploited.In this study,we cover this gap and investigate how experts from different countries value the SDGs and relate them with ES.A total of 66 countries participated to the survey,and answers were grouped into three macro-regions:Asia;Europe,North America,and Oceania(ENO);Latin America,Caribbean and Africa(LA).Results show that the most prioritized SDGs in the three macro-regions are usually those related to essential material needs and environmental conditions,such as SDG2(Zero Hunger),SDG1(No Poverty),and SDG6(Clean Water).At a global scale,the number of prioritized synergies between SDGs and ES largely exceeded trade-offs.The highest amount of synergies was observed for SDG1(No Poverty),mainly with SDG2,SDG3(Good Health),SDG5(Gender Equality),and SDG8(Economic Growth).Other major synergies among SDGs include SDG14-15(Life below water-Life on land),SDG5-10(Gender Equity-Reduced Inequality),and SDG1-2(No poverty-Zero Hunger).At a global scale,SDG15,SDG13,SDG14,and SDG6 were closely related to ES like climate regulation,freshwater,food,water purification,biodiversity,and education.SDG11(Sustainable Cities)and SDG3 were also relevant in Asia and in LA,respectively.Overall,this study shows the potential to couple future policies that can implement SDGs’strategies while adopting ES-based solutions in different regions of the world.展开更多
Axis-symmetric spheroids, such as rod-like and disk-like particles, have been found to orient preferentially in near-wall turbulence by both experiment and numerical simulation. In current work we examined the orienta...Axis-symmetric spheroids, such as rod-like and disk-like particles, have been found to orient preferentially in near-wall turbulence by both experiment and numerical simulation. In current work we examined the orientation of inertialess spheroids in a turbulent channel flow at medium friction Reynolds number Reτ=100 given based on the half of channel height. Both elongated prolate spheroid and flat oblate spheroid are considered and further compared with the reference case of spherical particle. The statistical results show that in near wall region the prolate spheroids tend to align in the streamwise direction while the oblate spheroids prefer to orient in the wallnormal direction, which are consistent with earlier observation in low Reynolds number (Reτ=180)wall turbulence. Around the channel center we found that the orientation of spheroids is not fully isotropic, even though the fluid vorticity are almost isotropic. The mechanism that gives rise to such particle orientations in wall-turbulence has been found to be related to fluid Lagrangian stretching and compression (Zhao and Andersson 2016). Therefore, we computed the left Cauchy-Green strain tensor along Lagrangian trajectories of tracer spheroids in current flow field and analyzed the fluid Lagrangian stretching and compression. The results indicated that, similar to the earlier observations, the directions of the Lagrangian stretching and compression in near-wall region are in the streamwise and wall-normal directions, respectively. Furthermore, cross over the channel the prolate spheroids aligned with the direction of Lagrangian stretching but oblate spheroids oriented with the direction of Lagrangian compression. The weak anisotropy of orientations of fluid Lagrangian stretching and compression observed at the channel center could be the reason for the aforementioned modest anisotropic orientation of spheroids in channel central region.展开更多
The transition to a non-emitting energy mix for power generation will take decades. This transition will need to be sustainable, e.g.economically affordable. Fossil fuels which are abundant have an important role to p...The transition to a non-emitting energy mix for power generation will take decades. This transition will need to be sustainable, e.g.economically affordable. Fossil fuels which are abundant have an important role to play in this respect, provided that Carbon Capture and Storage(CCS) is progressively implemented. CCS is the only way to reduce emissions from energy intensive industries.Thus, the need for upgraded and new CCS research facilities is widely recognised among stakeholders across Europe, as emphasised by the Zero Emissions Platform(ZEP) [1] and the European Energy Research Alliance on CCS(EERA-CCS) [2].The European Carbon Dioxide Capture and Storage Laboratory Infrastructure, ECCSEL, provides funders, operators and researchers with significant benefits by offering access to world-class research facilities that, in many cases, are unlikely for a single nation to support in isolation.This implies creation of synergy and the avoidance of duplication as well as streamlining of funding for research facilities.ECCSEL offers open access to its advanced laboratories for talented scientists and visiting researchers to conduct cutting-edge research.In the planning of ECCSEL, gap analyses were performed and CCS technologies have been reviewed to underpin and envisage the future experimental setup; 1) Making use of readily available facilities, 2) Modifying existing facilities, and 3) Planning and building entirely new advanced facilities.The investments required for the first ten years(2015-2025) are expected to be in the range of €80-120 miilion. These investments show the current level of ambition, as proposed during the preparatory phase(2011-2014).Entering the implementation phase in 2015, 9 European countries signed Letter of Intent(LoI) to join a ECCSEL legal entity: France, United Kingdom, Netherlands, Italy, Spain, Poland, Greece, Norway and Switzerland(active observer). As the EU ERIC-regulation [3] would offer the most suitable legal framework for ECCSEL, the host country, Norway, will apply for establishing ERIC as the ECCSEL Research Infrastructure(RI)legal entity in 2017. Until the ECCSEL ERIC is approved by the European Commission(probably by summer 2017), an interim MoU agreement for the implementation phase of ECCSEL RI has been signed by 13 research institutions and universities representing the 9 countries. A consortium of these partners were granted 3 million EURO from Horizon 2020 to boost implementation of ECCSEL from September 2015 and two years onwards.?2016, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).展开更多
Load forecasting can increase the efficiency of modern energy systems with built-in measuring systerms by providing a more accurate peak power shaving performance and thus more reliable control.An analysis of an integ...Load forecasting can increase the efficiency of modern energy systems with built-in measuring systerms by providing a more accurate peak power shaving performance and thus more reliable control.An analysis of an integrated CO2 heat pump and chiller system with a hot water storage system is presented in this paper.Drastic power fluctuations,which can be reduced with load forecasting,are found in historical operation records.A model that aims to forecast the ventilation system heating demand is thus established on the basis of a long short-term memory(LSTM)network.The model can successfully forecast the one hour ahead power using records of the past 48h of the system operation data and the ambient temperature.The mean absolute percentage error(MAPE)of the forecast results of the LSTM-based model is 10.70%,which is respectively 2.2%and 7.25%better than the MAPEs of the forecast results of the support vector regression based and persistence method based models.展开更多
The demand for fuel for utilisation of machinery and transport has culminated in large amounts of fossil fuel usage in the last century. The environmental dangers attached with the usage of fossil fuels have created a...The demand for fuel for utilisation of machinery and transport has culminated in large amounts of fossil fuel usage in the last century. The environmental dangers attached with the usage of fossil fuels have created a large demand for alternative sources of fuels. There is an array of polysaccharides contained within macroalgae, such as mannitol, cellulose and laminarin. These polysaccharides have potential for production of alternative biofuels;however, they are not easily accessible for biological digestion. By pretreatment of macroalgae with enzymes, these polysaccharides may be easier to access by microbes, allowing effective utilization in anaerobic digestion. Saccharina latissima, available in abundance on the Norwegian coast line, is a brown macroalgae with a high level of carbohydrates. This study assesses the ability for utilisation of enzymatically pre-treated Saccharina latissima for production of biogas through anaerobic digestion. The harvested Saccharina latissima was analysed to contain 30.11 ± 2.30 g of reducing sugars per 100 g of dry sample upon enzymatic hydrolysis. This was able to yield 459 ± 30 mL per gVS of biogas through anaerobic digestion, with a methane content of 56%. This suggests a biomethane potential of 1760 m3 per ha of productive sea floor growing Saccharina latissima. An evaluation of this process has been performed to demonstrate the industrial potential of Saccharina latissima in biogas production.展开更多
A numerical method for predicting fiber orientation is presented to explore the flow properties of turbulent fiber suspension flowing through a stock pump impeller. The Fokker-Planck equation is used to describe the d...A numerical method for predicting fiber orientation is presented to explore the flow properties of turbulent fiber suspension flowing through a stock pump impeller. The Fokker-Planck equation is used to describe the distribution of fiber orientation. The effect of flow-fiber coupling is considered by modifying the constitutive mode.The three-dimensional orientation distribution function is formulated and the corresponding equations are solved in terms of second-order and fourth-order orientation tensors. The evolution of fiber orientation, flow velocity and pressure, additional shear stress and normal stress difference are presented. The results show that the evolutions of fiber orientation are different along different streamlines. The velocity and its gradient are large in the concave wall region, while they are very small in the convex wall region. The additional shear stress and normal stress difference are large in the inlet and concave wall regions, and moderate in the mid-region, while they are almost zero in most downstream regions. The non-equilibrium fiber orientation distribution is dominant at the inlet and the concave wall regions. The flow will consume more energy to overcome the additional shearing losses due to fibers at the inlet and the concave wall regions. The change of flow rates has effect on the distribution of additional shear stress and normal stress difference. The flow structure in the inlet and concave wall regions is essential in the resultant rheological properties of the fiber suspension through the stock pump impeller, which will directly affect the flow efficiency of the fiber suspension through the impeller.展开更多
Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engine...Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load （T5.4-control）, hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field＇s production and economy. The performance and operational experience with on-line wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line wash are given. This work is based on long-term operation with on-line wash, where operational data are collected and performance analyzed, over a 4-5 year period. All engines are operated with four-month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load （i.e., normal operating load for the subject engine）. To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line wash. It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine＇s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed. Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.展开更多
Penetration of the power generated using wind and solar energy to electrical grid network causing several incidents of the grid tripping, power outage, and frequency drooping. This has increased restart （star-stop） ...Penetration of the power generated using wind and solar energy to electrical grid network causing several incidents of the grid tripping, power outage, and frequency drooping. This has increased restart （star-stop） cycles of the hydroelectric turbines significantly since grid connected hydroelectric turbines are widely used to manage critical conditions of the grid. Each cycle induces significant stresses due to unsteady pressure loading on the runner blades. The presented work investigates the pressure loading to a high head （ He = 377 m, De = 1.78 m） Francis turbine during start-stop. The measurements were carried out on a scaled model turbine （HM = 12.5 m, DM = 0.349 m）. Total four operating points were considered. At each operating point, three schemes of guide vanes opening and three schemes of guide vanes closing were investigated. The results show that total head variation is up to 9% during start-stop of the turbine. On the runner blade, the maximum pressure amplitudes are about 14 kPa and 16 kPa from the instantaneous mean value of 121 kPa during rapid start-up and shutdown, respectively, which are about 1.5 times larger than that of the slow start-up and shutdown. Moreover, the maximum pressure fluctuations are given at the blade trailing edge.展开更多
Three floating liquefaction concepts aiming at offshore natural gas recovery,Liquefied Natural Gas(LNG),Heavy Liquefied Gas(HLG)or another similar concept Pressurized Liquid Natural Gas(PLNG)and Liquefied Unprocessed ...Three floating liquefaction concepts aiming at offshore natural gas recovery,Liquefied Natural Gas(LNG),Heavy Liquefied Gas(HLG)or another similar concept Pressurized Liquid Natural Gas(PLNG)and Liquefied Unprocessed Well Stream(LUWS)have gained interest in the past decade,control or prevention of solid formation is crucial for all these processes.In this work,the solubility of carbon dioxide and heavy hydrocarbons in the gas mixture at low temperature is simulated and compared with literature data.Using Soave-Redlich-Kwong(SRK)equation of state(EOS)for the fluid phase and a fugacity model for the solid phase,the simulation of carbon dioxide solid behavior agrees with experimental data.The phenomenon of carbon dioxide and benzene solids existing together in gas mixture is analyzed,the result shows the difference in dealing with the potential solid formation components in the offshore liquefaction concepts.展开更多
Guide vane cascade of a low speed number Francis turbine is developed for the experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference pr...Guide vane cascade of a low speed number Francis turbine is developed for the experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference prototype turbine. Standard analytical methods are used to design the reference turbine. Periodic walls of flow channel between guide vanes are identified as the starting profile for the boundary of the cascade. Two alternative designs with three guide vanes and two guide vanes, without runner, are studied. A new approach, for the hydraulic design and optimization of the cascade test setup layout, is proposed and investigated in details. CFD based optimization methods are used to define the final layout of the test setup. The optimum design is developed as a test setup and experimental validation is done with PIV methods. The optimized design of cascade with one guide vane between two flow channels is found to produce similar flow conditions to that in the runner inlet of a low speed number Francis turbine.展开更多
The industrial sector is vital to economic progress,yet industrial pollution poses environmental and economic concerns.The purpose of the study was to investigate the influence of green industrial transformation in re...The industrial sector is vital to economic progress,yet industrial pollution poses environmental and economic concerns.The purpose of the study was to investigate the influence of green industrial transformation in re-ducing Pakistan’s carbon intensity between 1975 and 2020.Carbon emissions are considered an endogenous construct,while foreign direct investment(FDI)inflows,technological innovation,green industrial transforma-tion,environmental legislation,and research and development(R&D)investment are possible mediators.The association between variables is assessed using the robust least-squares approach.Green industrial transforma-tion is connected with lower carbon emissions,yet technical innovation,R&D investment,and inbound FDI raise a country’s carbon emissions.The findings support the pollution haven hypothesis in a country.The causality esti-mates indicate that inward FDI contributes to environmental regulations;green industrial transformation directly relates to inbound FDI and R&D expenditures;and technological innovations correspond to inbound FDI,R&D ex-penditures,industrial ecofriendly progression,and environmental standards.According to the impulse response function,environmental policies are anticipated to have a differential effect on carbon emissions in 2023,2024,2028-2030,while they are likely to decrease in the years 2025-2027 and 2031 forward.Additionally,inward FDI and technology advancements would almost certainly result in a rise in carbon emissions over time.Green industrial transitions are projected to result in a ten-year reduction in carbon emissions.The variance decomposi-tion analysis indicates that eco-friendly industrial adaptations would likely have the largest variance error shock on carbon emissions(11.747%),followed by inbound FDI,technological advancements,and regulatory changes,with R&D spending having a minimal impact over time.Pakistan’s economy should foster a green industrial revolution to avoid pollution and increase environmental sustainability to meet its environmental goals.展开更多
基金Financial support from the National Natural Science Foundation of China(21736008)。
文摘Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparison between direct heat exchange(DHE)and open-cycle mechanical heat pump(MHP)under various operating conditions is carried out in this work.The price ratios R_(ES)(electricity to steam)and R_(HS)(hot water to steam)are introduced to quantify regional impacts and conduct quantitative analysis.A semi-empirical formula is obtained to explore the exergoeconomic performance of the two systems.For waste heat within 373.15-423.15 K,the exergy efficiency of the DHE with a temperature difference of 10-90 K is always lower than that of the MHP with a temperature lift of 10-50 K.The economic performance of the two systems has a break-even point,depending on the operating parameters and relative prices of electricity,steam,and hot water.Under the average R_(ES)(3.8)in China,if R_(HS)is higher than 0.748,the annual revenue of the DHE is always higher,whereas the MHP is more economical when R_(HS)is lower than 0.110.In regions where R_(ES)is higher than 4.353,the annual revenue of the MHP will be negative in some cases.
基金funded by the National Natural Science Foundation of China(Grant No.41861134038,Grant No.41771197)Norwegian Research Council(Grant No.286773)the Fundamental Research Funds for the Central Universities.
文摘The COVID-19 pandemic has stalled and rolled back progress on Sustainable Development Goals(SDGs).Ecosys-tem services(ESs),defined as the contributions of ecosystems to human well-being,underpin the achievement of SDGs.To promote SDG achievement in post-pandemic era,we teased out the links between ESs and SDGs while examining the impact of COVID-19.We found that ESs benefited all SDGs,yet man-made pressures led to degra-dation of ecosystems and their services.There is broad consensus that the virus lurks in degraded ecosystems and generates spillover due to human interference.The pandemic and global lockdown/restriction disrupted the flow of ESs and altered human ESs demand,threatening the efforts for the SDGs.We suggested:1)to study the association and traceability of ESs-SDGs under the pandemic;2)to prioritize pressing issues such as health care,livelihood,and resource security and in the long run,we should promote human-nature harmony to achieve the SDGs;and 3)to enhance ESs and to promote the SDGs through local community efforts,ESs accounting,and ecosystem restoration.This paper provides insights into the importance of ESs to the SDGs and the ways to integrate ESs into socio-economic development to promote the SDG achievement after the pandemic.
基金This research was funded by the National Natural Science Foun-dation of China(Grant No.41861134038,41771197)Norwegian Re-search Council(Grant No.286773)the Fundamental Research Funds for the Central Universities,and Fundamental Research Program of Shanxi Province(Grant No.20210302123481).
文摘The trade-offs and supply-demand relations of ecosystem services(ES)are at the frontier of geographical and ecological studies.However,previous studies have focused on either trade-offs or the supply-demand aspects,while ES conflicts and supply/demand contradictions have not been comprehensively examined.The relation-ship between ES trade-offs and supply-demand is logically valid and studying the coupling of both can provide approaches for simultaneously alleviating ES conflicts and supply-demand contradictions.This study,based on a review of previous analyses of ES trade-offs and supply-demand dynamics,proposes a new analytic framework to couple them.First,we define two types of trade-offs based on the directions of growth or decline of the two ser-vices.We also define the supply-demand balance area and the supply-demand risk area according to the ES flow characteristics.Second,the mechanisms driving ES trade-offs are clarified,and land-use scenarios are set based on the mechanisms.Third,the supply-demand spatial characteristics of ES are analyzed,and supply-demand risk areas are identified.Finally,scenario iterations are performed to minimize the supply-demand risk area at an acceptable trade-offintensity to identify an optimal land use plan,which simultaneously alleviates ES conflicts and supply-demand contradictions.This analytic framework offers new opportunities for improving sustainable ecosystem management.
基金supported by Department of Energy and Process Engineering,Norwegian University of Science and TechnologyInstitute for Energy Technology and SINTEF through the FACE(Multiphase Flow Assurance Innovation Center) Project
文摘Particle based methods can be used for both the simulations of solid and fluid phases in multiphase medium, such as the discrete-element method for solid phase and the smoothed particle hydrodynamics for fluid phase. This paper presents a computational method combining these two methods for solid-liquid medium. The two phases are coupled by using an improved model from a reported Lagrangian-Eulerian method. The technique is verified by simulating liquid-solid flows in a two-dimensional lid-driven cavity.
基金This research was funded by the Norwegian Research Council(Grant No.286773)the National Natural Science Foundation of China(Grant No.41861134038)through the CHINOR bilateral research project Mi-tiStress,China Scholarship Council(Grant No.201906410051)the Fundamental Research Funds for National Universities,China University of Geosciences(Wuhan)(Grant No.2201710266).Hu acknowledges the help from Dr.Ceccherini for the forest harvested maps.
文摘Mapping spatiotemporal land cover changes offers opportunities to better understand trends and drivers of envi-ronmental change and helps to identify more sustainable land management strategies.This study investigates the spatiotemporal patterns of changes in land covers,forest harvest areas and soil erosion rates in Nordic countries,namely Norway,Sweden,Finland,and Denmark.This region is highly sensitive to environmental changes,as it is experiencing high levels of human pressure and among the highest rates of global warming.An analysis that uses consistent land cover dataset to quantify and compares the recent spatiotemporal changes in land cover in the Nordic countries is missing.The recent products issued by the European Space Agency and the Copernicus Climate Change Service framework provide the possibility to investigate the historical land cover changes from 1992 to 2018 at 300 m resolution.These maps are then integrated with time series of forest harvest areas be-tween 2004 and 2018 to study if and how forest management is represented in land cover products,and with soil erosion data to explore status and recent trends in agricultural land.Land cover changes typically involved from 4%to 9%of the total area in each country.Wetland showed the strongest reduction(11,003 km^(2),−11%of the wetland area in 1992),followed by forest(8,607 km^(2),−1%)and sparse vegetation(5,695 km^(2),−7%),while agriculture(15,884 km^(2),16%)and settlement(3,582 km^(2),84%)showed net increases.Wetland shrinkage dominated land cover changes in Norway(5,870 km^(2),−18%),followed by forest and grassland with a net gain of 3,441 km^(2)(3%)and 3,435 km^(2)(10%),respectively.In Sweden,forest areas decreased 13,008 km^(2)(−4%),mainly due to agriculture expansion(9,211 km^(2),29%).In Finland,agricultural areas increased by 5,982 km^(2)(24%),and wetland decreased by 6,698 km^(2)(−22%).Settlement had the largest net growth in Denmark(717 km^(2),70%),mainly from conversion of agriculture land.Soil erosion rates in Nordic countries are lower than the global average,but they are exacerbating in several locations(especially western Norway).The integration of the land cover datasets with maps of forest harvest areas shows that the majority of the losses in forest cover due to forestry operations are largely undetected,but a non-negligible share of the forest-to-agriculture(up to 19%)or forest-to-grassland(up to 51%)transitions overlap with the harvested sites.Forestry activity in the study region primarily involves small-scale harvest events that are difficult to be detected at the 300 m resolution of the land cover dataset.An accurate representation of forest management remains a challenge for global datasets of land cover time series,and more interdisciplinary international efforts are needed to address this gap.Overall,this analysis provides a detailed overview of recent changes in land cover and forest management in Nordic countries as represented by state-of-the-art global datasets,and offers insights to future studies aiming to improve these data or apply them in land surface models,climate models,landscape ecology,or other applications.
文摘An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when the sampling is stopped. CFD simulations using the commercial software Ansys CFX were carried out for single phase gas flow to analyze the non-standard design. Pitot tube velocity calculations and isokinetic sampling conditions were studied. The predicted results were compared against theoretical velocity profiles from the literature and with gas single phase experimental data acquired in a horizontal 49 m long steel pipeline with an internal diameter of 69 mm. The experiments were done by using a dense gas (SF6) at 7 bara. An asymmetry of the experimental velocity profiles reproduced with the numerical simulations. The CFD simulations made it possible to verify the design and predict and correct an installation problem.
基金funded by the Norwegian Research Council through the project MitiStress(Grant No.286773).
文摘Revegetation of former agricultural land is a key option for climate change mitigation and nature conservation.Expansion and abandonment of agricultural land is typically influenced by trends in diets and agricultural inten-sification,which are two key parameters in the Shared Socioeconomic Pathways(SSPs).Datasets mapping future land dynamics under different SSPs and climate change mitigation targets stem from different scenario assump-tions,land data and modelling frameworks.This study aims to determine the role that these three factors play in the estimates of the evolution of cropland and pastureland in future SSPs under different climate scenarios from four main datasets largely used in the climate and land surface studies.The datasets largely agree with the rep-resentation of cropland at present-day conditions,but the identification of pastureland is ambiguous and shows large discrepancies due to the lack of a unique land-use category.Differences occur with future projections,even for the same SSP and climate target.Accounting for CO_(2)sequestration from revegetation of abandoned agri-cultural land and CO_(2)emissions from forest clearance due to agricultural expansion shows a net reduction in vegetation carbon stock for most SSPs considered,except SSP1.However,different datasets give differences in estimates,even when representative of the same scenario.With SSP1,the cumulative increase in carbon stock until 2050 is 3.3 GtC for one dataset,and more than double for another.Our study calls for a common classifica-tion system with improved detection of pastureland to harmonize projections and reduce variability of outcomes in environmental studies.
基金X.H.and F.C.thank the support of the Norwegian Research Council through the projects Mitistress(Grant No.286773)BEST(Grant No.288047)+1 种基金W.Z.of the National Natural Science Foundation of China(Grant No.42271292)State Key Laboratory of Earth Surface Processes and Resource Ecology(Grant No.2022-ZD-08).
文摘Using biomass from dedicated crops for energy production and natural vegetation regrowth are key elements in future climate change mitigation scenarios.However,there are still uncertainties about the mitigation potentials that can be achieved by the different land-based systems and how they perform relative to each other.In this study,we use harmonized future land use datasets to identify global land areas dedicated to second generation bioenergy crop production in 2050 under different climate scenarios.We then assess the global climate change mitigation potentials of using biomass for producing bioethanol with(BECCS)or without carbon capture and storage,biochar,or a synthetic fuel(e-methanol).For the latter,the electricity required to produce hydrogen for e-methanol synthesis is sourced from either wind power or the projected average electricity mix in 2050.Mitigation potential from natural regrowth on the identified land is also quantified.For all the cases,we modelled emissions of greenhouse gases from the life-cycle stages and use parameterized models to estimate local biomass growth rates.The identified land areas range from 1.95 to 13.8 million hectares and can provide from 30 to 178 mega ton(Mt)dry biomass annually from dedicated crops.Climate change mitigation potentials range from 11 to 257 MtCO_(2)-eq.yr^(−1),depending on technological option and land availability.The largest mitigation is delivered by BECCS,but e-methanol can achieve similar findings when hydrogen is sourced from wind power.If hydrogen is produced from grid electricity,e-methanol can result in net positive emissions.E-methanol can also deliver more final energy than bioethanol(4.04 vs.1.27 EJ yr^(−1)).Natural vegetation regrowth can generally achieve higher mitigation than bioethanol,but less than biochar.An optimal combination of BECCS and natural vegetation regrowth can achieve a larger mitigation,up to 281 MtCO_(2)-eq.yr^(−1),indicating that integrated solutions can help to achieve successful land management strategies for climate change mitigation.
文摘The development and deployment of Carbon dioxide Capture and Storage （CCS） technology is a cornerstone of the Norwegian government＇s climate strategy. A number of projects are currently evaluated/planned along the Norwegian West Coast, one at Tjeldbergodden. COe from this project will be utilized in part for enhanced oil recovery in the Halten oil field, in the Norwegian Sea. We study a potential design of such a system. A combined cycle power plant with a gross power output of 832 MW is combined with CO2 capture plant based on a post-combustion capture using amines as a solvent. The captured CO2 is used for enhanced oil recovery （EOR）. We employ a hybrid life-cycle assessment （LCA） method to assess the environmental impacts of the system. The study focuses on the modifications and operations of the platform during EOR. We allocate the impacts connected to the capture of CO2 to electricity production, and the impacts connected to the transport and storage of CO2 to the oil produced. Our study shows a substantial reduction of the greenhouse gas emissions from power production by 80% to 75 g·（kW·h）^-1. It also indicates a reduction of the emissions associated with oil production per unit oil produced, mostly due to the increased oil production. Reductions are especially significant if the additional power demand due to EOR leads to power supply from the land.
基金This work was supported by National Key R&D Program of China(Grant No.2017YFA0604700)National Natural Science Foundation of China(Grant No.4181101243)+2 种基金the Fundamental Research Funds for the Central UniversitiesFrancesco Cherubini was supported by Nor-wegian Research Council(Grant No.286773)Paulo Pereira was sup-ported by the European Social Fund project LINESAM(Grant No.09.3.3-LMT-K-712-01-0104).
文摘The implementation of strategies to achieve the Sustainable Development Goals(SDGs)is frequently hindered by potential trade-offs between priorities for either environmental protection or human well-being.However,ecosystem services(ES)-based solutions can offer possible co-benefits for SDGs implementation that are often overlooked or underexploited.In this study,we cover this gap and investigate how experts from different countries value the SDGs and relate them with ES.A total of 66 countries participated to the survey,and answers were grouped into three macro-regions:Asia;Europe,North America,and Oceania(ENO);Latin America,Caribbean and Africa(LA).Results show that the most prioritized SDGs in the three macro-regions are usually those related to essential material needs and environmental conditions,such as SDG2(Zero Hunger),SDG1(No Poverty),and SDG6(Clean Water).At a global scale,the number of prioritized synergies between SDGs and ES largely exceeded trade-offs.The highest amount of synergies was observed for SDG1(No Poverty),mainly with SDG2,SDG3(Good Health),SDG5(Gender Equality),and SDG8(Economic Growth).Other major synergies among SDGs include SDG14-15(Life below water-Life on land),SDG5-10(Gender Equity-Reduced Inequality),and SDG1-2(No poverty-Zero Hunger).At a global scale,SDG15,SDG13,SDG14,and SDG6 were closely related to ES like climate regulation,freshwater,food,water purification,biodiversity,and education.SDG11(Sustainable Cities)and SDG3 were also relevant in Asia and in LA,respectively.Overall,this study shows the potential to couple future policies that can implement SDGs’strategies while adopting ES-based solutions in different regions of the world.
基金the financial support from the National Natural Science Foundation of China(91752205,11702158 and 11490551)granted by the Programme for Supercomputing(NN2649K)
文摘Axis-symmetric spheroids, such as rod-like and disk-like particles, have been found to orient preferentially in near-wall turbulence by both experiment and numerical simulation. In current work we examined the orientation of inertialess spheroids in a turbulent channel flow at medium friction Reynolds number Reτ=100 given based on the half of channel height. Both elongated prolate spheroid and flat oblate spheroid are considered and further compared with the reference case of spherical particle. The statistical results show that in near wall region the prolate spheroids tend to align in the streamwise direction while the oblate spheroids prefer to orient in the wallnormal direction, which are consistent with earlier observation in low Reynolds number (Reτ=180)wall turbulence. Around the channel center we found that the orientation of spheroids is not fully isotropic, even though the fluid vorticity are almost isotropic. The mechanism that gives rise to such particle orientations in wall-turbulence has been found to be related to fluid Lagrangian stretching and compression (Zhao and Andersson 2016). Therefore, we computed the left Cauchy-Green strain tensor along Lagrangian trajectories of tracer spheroids in current flow field and analyzed the fluid Lagrangian stretching and compression. The results indicated that, similar to the earlier observations, the directions of the Lagrangian stretching and compression in near-wall region are in the streamwise and wall-normal directions, respectively. Furthermore, cross over the channel the prolate spheroids aligned with the direction of Lagrangian stretching but oblate spheroids oriented with the direction of Lagrangian compression. The weak anisotropy of orientations of fluid Lagrangian stretching and compression observed at the channel center could be the reason for the aforementioned modest anisotropic orientation of spheroids in channel central region.
文摘The transition to a non-emitting energy mix for power generation will take decades. This transition will need to be sustainable, e.g.economically affordable. Fossil fuels which are abundant have an important role to play in this respect, provided that Carbon Capture and Storage(CCS) is progressively implemented. CCS is the only way to reduce emissions from energy intensive industries.Thus, the need for upgraded and new CCS research facilities is widely recognised among stakeholders across Europe, as emphasised by the Zero Emissions Platform(ZEP) [1] and the European Energy Research Alliance on CCS(EERA-CCS) [2].The European Carbon Dioxide Capture and Storage Laboratory Infrastructure, ECCSEL, provides funders, operators and researchers with significant benefits by offering access to world-class research facilities that, in many cases, are unlikely for a single nation to support in isolation.This implies creation of synergy and the avoidance of duplication as well as streamlining of funding for research facilities.ECCSEL offers open access to its advanced laboratories for talented scientists and visiting researchers to conduct cutting-edge research.In the planning of ECCSEL, gap analyses were performed and CCS technologies have been reviewed to underpin and envisage the future experimental setup; 1) Making use of readily available facilities, 2) Modifying existing facilities, and 3) Planning and building entirely new advanced facilities.The investments required for the first ten years(2015-2025) are expected to be in the range of €80-120 miilion. These investments show the current level of ambition, as proposed during the preparatory phase(2011-2014).Entering the implementation phase in 2015, 9 European countries signed Letter of Intent(LoI) to join a ECCSEL legal entity: France, United Kingdom, Netherlands, Italy, Spain, Poland, Greece, Norway and Switzerland(active observer). As the EU ERIC-regulation [3] would offer the most suitable legal framework for ECCSEL, the host country, Norway, will apply for establishing ERIC as the ECCSEL Research Infrastructure(RI)legal entity in 2017. Until the ECCSEL ERIC is approved by the European Commission(probably by summer 2017), an interim MoU agreement for the implementation phase of ECCSEL RI has been signed by 13 research institutions and universities representing the 9 countries. A consortium of these partners were granted 3 million EURO from Horizon 2020 to boost implementation of ECCSEL from September 2015 and two years onwards.?2016, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).
基金the Special Program for Innovation Methodology of the Ministry of Science and Technology of China(No.2016IM010100)。
文摘Load forecasting can increase the efficiency of modern energy systems with built-in measuring systerms by providing a more accurate peak power shaving performance and thus more reliable control.An analysis of an integrated CO2 heat pump and chiller system with a hot water storage system is presented in this paper.Drastic power fluctuations,which can be reduced with load forecasting,are found in historical operation records.A model that aims to forecast the ventilation system heating demand is thus established on the basis of a long short-term memory(LSTM)network.The model can successfully forecast the one hour ahead power using records of the past 48h of the system operation data and the ambient temperature.The mean absolute percentage error(MAPE)of the forecast results of the LSTM-based model is 10.70%,which is respectively 2.2%and 7.25%better than the MAPEs of the forecast results of the support vector regression based and persistence method based models.
文摘The demand for fuel for utilisation of machinery and transport has culminated in large amounts of fossil fuel usage in the last century. The environmental dangers attached with the usage of fossil fuels have created a large demand for alternative sources of fuels. There is an array of polysaccharides contained within macroalgae, such as mannitol, cellulose and laminarin. These polysaccharides have potential for production of alternative biofuels;however, they are not easily accessible for biological digestion. By pretreatment of macroalgae with enzymes, these polysaccharides may be easier to access by microbes, allowing effective utilization in anaerobic digestion. Saccharina latissima, available in abundance on the Norwegian coast line, is a brown macroalgae with a high level of carbohydrates. This study assesses the ability for utilisation of enzymatically pre-treated Saccharina latissima for production of biogas through anaerobic digestion. The harvested Saccharina latissima was analysed to contain 30.11 ± 2.30 g of reducing sugars per 100 g of dry sample upon enzymatic hydrolysis. This was able to yield 459 ± 30 mL per gVS of biogas through anaerobic digestion, with a methane content of 56%. This suggests a biomethane potential of 1760 m3 per ha of productive sea floor growing Saccharina latissima. An evaluation of this process has been performed to demonstrate the industrial potential of Saccharina latissima in biogas production.
基金Supported by the National Natural Science Foundation of China （51309118）, the National Key Technology R＆D Program of the Ministry of Science and Technology of China （2011BAF14B01）, the Postdoctoral Science Foundation of China （2013M531282） and the Doctorate Program of Higher Education of China （20120101110121）.
文摘A numerical method for predicting fiber orientation is presented to explore the flow properties of turbulent fiber suspension flowing through a stock pump impeller. The Fokker-Planck equation is used to describe the distribution of fiber orientation. The effect of flow-fiber coupling is considered by modifying the constitutive mode.The three-dimensional orientation distribution function is formulated and the corresponding equations are solved in terms of second-order and fourth-order orientation tensors. The evolution of fiber orientation, flow velocity and pressure, additional shear stress and normal stress difference are presented. The results show that the evolutions of fiber orientation are different along different streamlines. The velocity and its gradient are large in the concave wall region, while they are very small in the convex wall region. The additional shear stress and normal stress difference are large in the inlet and concave wall regions, and moderate in the mid-region, while they are almost zero in most downstream regions. The non-equilibrium fiber orientation distribution is dominant at the inlet and the concave wall regions. The flow will consume more energy to overcome the additional shearing losses due to fibers at the inlet and the concave wall regions. The change of flow rates has effect on the distribution of additional shear stress and normal stress difference. The flow structure in the inlet and concave wall regions is essential in the resultant rheological properties of the fiber suspension through the stock pump impeller, which will directly affect the flow efficiency of the fiber suspension through the impeller.
文摘Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load （T5.4-control）, hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field＇s production and economy. The performance and operational experience with on-line wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line wash are given. This work is based on long-term operation with on-line wash, where operational data are collected and performance analyzed, over a 4-5 year period. All engines are operated with four-month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load （i.e., normal operating load for the subject engine）. To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line wash. It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine＇s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed. Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.
基金the Swedish Waterpower Centre(SVC)for the financial support.SVC has been established by the Swedish Energy Agency,Elforsk and SvenskaKraftnat together with LuleUniversity of Technology,the Royal Institute of Technology,Chalmers University of Technology and Uppsala University(www.svc.nu)
文摘Penetration of the power generated using wind and solar energy to electrical grid network causing several incidents of the grid tripping, power outage, and frequency drooping. This has increased restart （star-stop） cycles of the hydroelectric turbines significantly since grid connected hydroelectric turbines are widely used to manage critical conditions of the grid. Each cycle induces significant stresses due to unsteady pressure loading on the runner blades. The presented work investigates the pressure loading to a high head （ He = 377 m, De = 1.78 m） Francis turbine during start-stop. The measurements were carried out on a scaled model turbine （HM = 12.5 m, DM = 0.349 m）. Total four operating points were considered. At each operating point, three schemes of guide vanes opening and three schemes of guide vanes closing were investigated. The results show that total head variation is up to 9% during start-stop of the turbine. On the runner blade, the maximum pressure amplitudes are about 14 kPa and 16 kPa from the instantaneous mean value of 121 kPa during rapid start-up and shutdown, respectively, which are about 1.5 times larger than that of the slow start-up and shutdown. Moreover, the maximum pressure fluctuations are given at the blade trailing edge.
基金sponsored by the Research Council of Norway 2007-2009 National Strategic Research Programme[Institusjonsforankret strategisk prosjekt(ISP)]
文摘Three floating liquefaction concepts aiming at offshore natural gas recovery,Liquefied Natural Gas(LNG),Heavy Liquefied Gas(HLG)or another similar concept Pressurized Liquid Natural Gas(PLNG)and Liquefied Unprocessed Well Stream(LUWS)have gained interest in the past decade,control or prevention of solid formation is crucial for all these processes.In this work,the solubility of carbon dioxide and heavy hydrocarbons in the gas mixture at low temperature is simulated and compared with literature data.Using Soave-Redlich-Kwong(SRK)equation of state(EOS)for the fluid phase and a fugacity model for the solid phase,the simulation of carbon dioxide solid behavior agrees with experimental data.The phenomenon of carbon dioxide and benzene solids existing together in gas mixture is analyzed,the result shows the difference in dealing with the potential solid formation components in the offshore liquefaction concepts.
文摘Guide vane cascade of a low speed number Francis turbine is developed for the experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference prototype turbine. Standard analytical methods are used to design the reference turbine. Periodic walls of flow channel between guide vanes are identified as the starting profile for the boundary of the cascade. Two alternative designs with three guide vanes and two guide vanes, without runner, are studied. A new approach, for the hydraulic design and optimization of the cascade test setup layout, is proposed and investigated in details. CFD based optimization methods are used to define the final layout of the test setup. The optimum design is developed as a test setup and experimental validation is done with PIV methods. The optimized design of cascade with one guide vane between two flow channels is found to produce similar flow conditions to that in the runner inlet of a low speed number Francis turbine.
文摘The industrial sector is vital to economic progress,yet industrial pollution poses environmental and economic concerns.The purpose of the study was to investigate the influence of green industrial transformation in re-ducing Pakistan’s carbon intensity between 1975 and 2020.Carbon emissions are considered an endogenous construct,while foreign direct investment(FDI)inflows,technological innovation,green industrial transforma-tion,environmental legislation,and research and development(R&D)investment are possible mediators.The association between variables is assessed using the robust least-squares approach.Green industrial transforma-tion is connected with lower carbon emissions,yet technical innovation,R&D investment,and inbound FDI raise a country’s carbon emissions.The findings support the pollution haven hypothesis in a country.The causality esti-mates indicate that inward FDI contributes to environmental regulations;green industrial transformation directly relates to inbound FDI and R&D expenditures;and technological innovations correspond to inbound FDI,R&D ex-penditures,industrial ecofriendly progression,and environmental standards.According to the impulse response function,environmental policies are anticipated to have a differential effect on carbon emissions in 2023,2024,2028-2030,while they are likely to decrease in the years 2025-2027 and 2031 forward.Additionally,inward FDI and technology advancements would almost certainly result in a rise in carbon emissions over time.Green industrial transitions are projected to result in a ten-year reduction in carbon emissions.The variance decomposi-tion analysis indicates that eco-friendly industrial adaptations would likely have the largest variance error shock on carbon emissions(11.747%),followed by inbound FDI,technological advancements,and regulatory changes,with R&D spending having a minimal impact over time.Pakistan’s economy should foster a green industrial revolution to avoid pollution and increase environmental sustainability to meet its environmental goals.
