As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solut...As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solution process to prepare freestanding TiO_2/graphene hydrogel electrode with tunable density and porous structures. By incorporating room temperature ionic liquids（RTILs）, even upon drying, the non-volatile RTILs that remained in the gel film would preserve the efficient ion transport channels and prevent the electrode from closely stacking, to develop dense yet porous structures. As a result, the dense TiO_2/graphene gel film as an electrode for lithium ion battery displayed a good gravimetric electrochemical performance and more importantly a high volumetric performance.展开更多
The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering per...The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.展开更多
This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were inve...This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m<sup>2</sup>. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m<sup>2</sup>. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.展开更多
In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main...In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel.Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10%（by volume） of hexanol and 90%（by volume） neat cashew nut shell biodiesel was referred to as CNSBD900 H100 and fuel comprising 20%（by volume） of hexanol and 80%（by volume）of neat cashew nut shell biodiesel was referred to as CNSBD800 H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at10% and 20%（by volume） to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.展开更多
In this study, an electro-mechanical valve （EMV） system for the intake valve ofa fottr stroke, single cylinder, overhead valve and spark ignition （SI） engine was designed and constructed. An engine with the EMV sy...In this study, an electro-mechanical valve （EMV） system for the intake valve ofa fottr stroke, single cylinder, overhead valve and spark ignition （SI） engine was designed and constructed. An engine with the EMV system and a standard engine were tested to observe the effects of the EMV on engine performance and emissions at different speeds under full load. The EMV engine showed improved engine power, engine torque and break specific fuel consumption （BSFC）. A 66% decrease in CO emissions was also obtained with the EMV system, but hydrocarbons （HC） and NOx emissions increased by 12% and 13% respectively.展开更多
A dual-mode scramjet can operate in a wide range of flight conditions. Higher thrust can be generated by adopting suitable combustion modes. Based on the net thrust, an analysis and preliminary optimal design of a ker...A dual-mode scramjet can operate in a wide range of flight conditions. Higher thrust can be generated by adopting suitable combustion modes. Based on the net thrust, an analysis and preliminary optimal design of a kerosene-fueled parameterized dual-mode scramjet at a cru- cial flight Mach number of 6 were investigated by using a modified quasi-one-dimensional method and simulated annealing strategy. Engine structure and heat release distrib- utions, affecting the engine thrust, were chosen as analytical parameters for varied inlet conditions （isolator entrance Mach number： 1.5-3.5）. Results show that different opti- mal heat release distributions and structural conditions can be obtained at five different inlet conditions. The highest net thrust of the parameterized dual-mode engine can be achieved by a subsonic combustion mode at an isolator entrance Mach number of 2.5. Additionally, the effects of heat release and scramjet structure on net thrust have been discussed. The present results and the developed analytical method can provide guidance for the design and optimization of high-performance dual-mode scramjets.展开更多
This work focuses on blending Jatropha oil with diesel fuel and heptane to improve its physico-chemical characteristics for production of blends and their use as fuel in a diesel engine. The influence of the heptane c...This work focuses on blending Jatropha oil with diesel fuel and heptane to improve its physico-chemical characteristics for production of blends and their use as fuel in a diesel engine. The influence of the heptane content was evaluated by comparing the results obtained from the engine (performance and combustion parameters) with those of the diesel fuel and straight Jatropha oil. The results obtained show an improvement in engine performance especially at low loads. Specifically, a reduction in the specific fuel consumption of the engine is obtained when the heptane content in the mixture is around 10% compared to that obtained with pure Jatropha oil. The best results were obtained with the blend containing 70% Jatropha oil, 20% diesel fuel and 10% heptane (J70G20H10). Overall engine efficiency and exhaust gas temperatures are comparable for all fuels tested. Engine combustion parameters are improved with J70G20H10. The results obtained with J70G20H10 are close to those of the engine operating on diesel fuel. The cyclic dispersion is low with coefficients of variation of the indicated mean effective pressure (COV<sub>IMEP</sub>) whose values are less than 10%. The lowest values of the COV<sub>IMEP</sub> are obtained with the blend J70G20H10.展开更多
This paper adopts American National Instruments (NI) Company’s LabVIEW and LabVIEW RT virtual instrument softwareplatform and lots of things for this engine performance LabVIEW virtual instrument test system, such as...This paper adopts American National Instruments (NI) Company’s LabVIEW and LabVIEW RT virtual instrument softwareplatform and lots of things for this engine performance LabVIEW virtual instrument test system, such as the matched NI PCI dataCollection Card, NI SCXI signal-adjusting instrument and NI compact FieldPoint (cFP) distributed I/O real time system hardware.This system has realized multi performances’parallel test; and it can complete load, torsional moment, rotate speed, power, pressureand temperature’s real time monitoring automatically according to user’s setting; and finally through TCP/IP protocol it realizes testdata’s teleshare and telecontrol that user put on the test system. This system has such character as short development period, highuse efficiency and low cost, at the same time it has strong extensibility and reusability, so it has very high applied cost.展开更多
Increasing global environmental issues and depleting fossil fuel reserves has necessitated the need for alternative and sustainable fuel. In this paper, the effects of biodiesel and its blend on engine emission and pe...Increasing global environmental issues and depleting fossil fuel reserves has necessitated the need for alternative and sustainable fuel. In this paper, the effects of biodiesel and its blend on engine emission and performance characteristics in an internal combustion engine were analyzed. Biodiesel derived from the transesterification of raw palm oil was blended with diesel fuel at different proportions designated as PO5 (5% Biodiesel and 95% Diesel), PO10 (10% Biodiesel and 90% Diesel), PO15 (15% Biodiesel and 85% Diesel), PO20 (20% Biodiesel and 80% Diesel), PO50 (50% Biodiesel and 50% Diesel), PO85 (85% Biodiesel and 15% Diesel), and PO100 (100% Biodiesel). A Lombardini 2-cylinder, four-stroke direct injection diesel engine with a compression ratio of 22.8 was developed using Ricardo Wave software in which diesel, palm oil biodiesel blends and pure biodiesel are used in the model, and the obtained results were analysed and presented. The simulation was done under varying engine speeds of 1200 rpm to 3200 rpm at full load condition. Biodiesel and its blends are more environment-friendly and non-toxic when compared to diesel fuel;it also improves the mechanical efficiency of the engines, and above all can also lead to a reduction in poverty among rural dwellers. The obtained results showed that brake specific fuel consumption and brake thermal efficiency increased with palm oil biodiesel blends as compared to diesel fuel which might be a result of biodiesel’s lower heating value, and the increase in thermal energy may be a result of the oxygenation of the biodiesel blend as compared to pure diesel. In terms of brake torque, palm oil biodiesel blends were lesser than diesel fuel. The CO, HC, and NO<sub>x</sub> emissions of palm oil biodiesel blends decreased significantly compared to that of pure diesel. From this study, palm oil biodiesel emits lesser emissions than diesel fuel and its performance characteristics are similar to diesel fuel. Therefore, palm oil biodiesel can be used without any modifications directly in a diesel engine. In addition, it can also be used as blends as an alternative and sustainable fuel, decreasing air pollution, and increasing environmental sustainability.展开更多
Development and application of new ceramic die materials is one of the important topics in the field of die research. The composition, processing technology, mechanical property and engineering performance of the cera...Development and application of new ceramic die materials is one of the important topics in the field of die research. The composition, processing technology, mechanical property and engineering performance of the ceramic materials such as cermet, ZTA, TZP, TZP/Al2O3, TZP/TiC/Al2O3, PSZ and Sialon, etc., with rare earth yttrium, lanthanum and cerium, and so on working as additives, were investigated and analyzed in the present study. Problems existed in the research and application of rare earth ceramic die materials were discussed. Rare earth additives can effectively improve the mechanical property and engineering performance of ceramic die materials. Thus, it will have further perspectives of wider application. More attention should be paid in the future to the toughening and strengthening of the ceramic die materials, the adding forms and kinds of rare earth elements and acting mechanisms of rare earth additives in ceramic die materials.展开更多
Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero...Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control(LADRC)is proposed.Firstly,based on CFD numerical simulation,aerodynamic performance model of AVEN is established,and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed.Subsequently,the integrated model of AVEN/-turbofan engine is established by Simulink/AMESim co-simulation.Finally,the nozzle throat area control loop based on LADRC is designed.The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system.The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%,indicating a high degree of confidence.Compared with the conventional PID control,the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%,which effectively improves the control stability of the vector deflection.Meanwhile,the fuel flow ratechange during the vector deflection process is smaller and more economical,which provides an important reference for engineering applications.展开更多
Part of an extensive research undertaken by the Concrete and Masonry Research Group at Kingston University-London was reported to demonstrate through scientific research and full-scale site trials,that quality recycle...Part of an extensive research undertaken by the Concrete and Masonry Research Group at Kingston University-London was reported to demonstrate through scientific research and full-scale site trials,that quality recycled concrete aggregates can be produced and can be used successfully in a range of concrete applications.The effects of up to 100% coarse recycled concrete aggregate（RCA） on fresh,engineering and durability related properties were established and assessed its suitability for use in a rage of sustainable applications.展开更多
The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area betw...The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.展开更多
The development of a diesel engine model using one-dimensional （1-D） fluid-dynamic engine simulation codes,and its validation using experimental measurements are described in this paper.The model was calibrated by r...The development of a diesel engine model using one-dimensional （1-D） fluid-dynamic engine simulation codes,and its validation using experimental measurements are described in this paper.The model was calibrated by running the engine on an electric dynamometer at eight steady-state operating conditions.The refined engine model was used to predict the oxides of nitrogen （NOx） less than those measured earlier in the experiments,and hence to recommend changes in the engine for the verification of the results.The refined engine model is greatly influenced by the start of injection angle （ψ）,ignition delay （φ）,premix duration （DP）,and main duration （DM） for the prediction of reduced NOx emissions.It is found that optimum ψ is 6.5° before top dead center （BTDC）.At this angle,the predicted and experimental results are in good agreement,showing only a difference of up to 4%,6.2%,and 7.5% for engine performance,maximum combustion pressure （Pmax）,and NOx,respectively.展开更多
To reduce the propulsion system installation thrust loss under high angle of attack maneuvering,a control method based on real-time optimization of the integrated aeropropulsion is proposed.Firstly,based on data fitti...To reduce the propulsion system installation thrust loss under high angle of attack maneuvering,a control method based on real-time optimization of the integrated aeropropulsion is proposed.Firstly,based on data fitting and physical principle,an integrated onboard model of propulsion system is established,which can calculate various performance parameters of the propulsion system in real time,and has high accuracy and real-time performance.Secondly,to improve the compatibility of optimization real-time performance and search accuracy,the online optimization control of aero-propulsion system is realized based on an improved trust region algorithm.Finally,by controlling the auxiliary intake valve,a good match between inlet and engine is realized,which solves the problems of intake flow reducing and total pressure recovery coefficient declining,and improves the installation performance of propulsion system.The simulation results indicate that,compared with the conventional independent engine control,the real-time integrated optimization method reduces the installed thrust loss by 3.61%under the design condition,and 4.58%under the off-design condition.Furthermore,the simulation on HIL(Hardware-In-theLoop)platform verifies the real-time performance of integrated optimization method.展开更多
The expanding amounts of information created by Internet of Things(IoT)devices places a strain on cloud computing,which is often used for data analysis and storage.This paper investigates a different approach based on...The expanding amounts of information created by Internet of Things(IoT)devices places a strain on cloud computing,which is often used for data analysis and storage.This paper investigates a different approach based on edge cloud applications,which involves data filtering and processing before being delivered to a backup cloud environment.This Paper suggest designing and implementing a low cost,low power cluster of Single Board Computers(SBC)for this purpose,reducing the amount of data that must be transmitted elsewhere,using Big Data ideas and technology.An Apache Hadoop and Spark Cluster that was used to run a test application was containerized and deployed using a Raspberry Pi cluster and Docker.To obtain system data and analyze the setup’s performance a Prometheusbased stack monitoring and alerting solution in the cloud based market is employed.This Paper assesses the system’s complexity and demonstrates how containerization can improve fault tolerance and maintenance ease,allowing the suggested solution to be used in industry.An evaluation of the overall performance is presented to highlight the capabilities and limitations of the suggested architecture,taking into consideration the suggested solution’s resource use in respect to device restrictions.展开更多
With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth...With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth-quakes.This study presents a novel comprehensive probabilistic framework to quantify the environmental impact of buildings,including uncertainties in the material extraction and production,transportation,construction,seis-mic exposure and aging(including deterioration),and end-of-life stages.The developed framework is used to quantify the environmental impact of a 3-story residential building located in Vancouver,Canada.The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment.If the prototype building is hit by the design level earthquake,it is expected that the median environmental impact of the prototype will be further increased by 42%.In addition,by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building,the earthquake related damage will result in an additional 5%of the initial carbon emission of the building.This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.展开更多
<span style="font-family:Verdana;">In the efforts to reduce effects of climate change, biodiesel fuels from plant oils such as </span><i><span style="font-family:Verdana;">J...<span style="font-family:Verdana;">In the efforts to reduce effects of climate change, biodiesel fuels from plant oils such as </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> have been proposed as alternative fuels which can be used in the transportation sector in diesel engines. The current study investigates the effects of fatty acids composition on fuel properties of biodiesel derived from </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> seeds obtained from selected regions of Botswana. The physicochemical fuel properties investigated include kinematic viscosity, flash point, energy content, density, pour point and cloud point from derived </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel. Results of the study showed that </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel samples for all regions under review are dominated by unsaturated fatty acids which are desirable for cold flow properties and kinematic viscosity of the biodiesel fuel. The major fatty acids in</span><i><span style="font-family:Verdana;"> Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel fuels from all the regions range </span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">from</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> 69.00% to 77.81% of unsaturated fatty acids. The overall results conclude that fatty acids composition has influence on the fuel properties of the biodiesel under investigated.</span></span></span>展开更多
The purpose of carrying out present work is to design, build and test a rhombic drive Stirling engine with a β-type configuration consisting of two dynamic pistons (displacer and power) reciprocates in the in-line co...The purpose of carrying out present work is to design, build and test a rhombic drive Stirling engine with a β-type configuration consisting of two dynamic pistons (displacer and power) reciprocates in the in-line concentric cylinder arrangement. The displacement rod is assembled concentrically inside the power piston rod. The rhombic drive mechanism is proposed in such a way that, by using a pair of gear wheels the sliding motion of both piston rods is controlled and thus, an engine is balanced. The developed prototype has a swept volume of 75 cm<sup>3</sup> with the displacer piston and power piston cylinder hot ends heated by liquefied petroleum gas (LPG) burner and cooled water, respectively. It uses air as the working gas at atmospheric pressure for initial charging of the engine. Several designs were studied before settling on a β-type configuration. The LPG gas burner was considered as a potential heat source. The various elements of an engine (heater, cooler, re-generator, flywheel and piping systems) were designed, constructed and analyzed. The testing results revealed that the engine at initial atmospheric air filling started working in only about 120 seconds at an LPG heater temperature of 400℃ (824<sup>°</sup>F) with 280 rpm. At a heater temperature of 550℃ (1022<sup>°</sup>F), the engine speed was 630 rpm. At the engine speed of 245 rpm, the maximum torque was 0.215 Nm, while the maximum power was 8 Watts at 355 rpm. Engine speed increased with the increase of flame temperature. Several tests were performed on the engine to improve its running efficiency and critical problem areas were isolated and addressed. Moreover, results revealed that Stirling engines working with relatively low-temperature air are potentially attractive engines of the future, especially LPG powered low temperature differential Stirling engines. The Stirling engine was capable of generating between 50 to 100 Watts of electricity.展开更多
基金supported by grants from the National Natural Science Foundation of China(21303251)Innovation Program of Shanghai Municipal Education Commission(16SG17)the Shenzhen Science and Technology Foundation(JCYJ201419122040621)
文摘As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solution process to prepare freestanding TiO_2/graphene hydrogel electrode with tunable density and porous structures. By incorporating room temperature ionic liquids（RTILs）, even upon drying, the non-volatile RTILs that remained in the gel film would preserve the efficient ion transport channels and prevent the electrode from closely stacking, to develop dense yet porous structures. As a result, the dense TiO_2/graphene gel film as an electrode for lithium ion battery displayed a good gravimetric electrochemical performance and more importantly a high volumetric performance.
基金the support of the National Natural Science Foundation of China(Grant Nos.41902286 and 41972269)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z019026)。
文摘The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.
文摘This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m<sup>2</sup>. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m<sup>2</sup>. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.
文摘In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel.Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10%（by volume） of hexanol and 90%（by volume） neat cashew nut shell biodiesel was referred to as CNSBD900 H100 and fuel comprising 20%（by volume） of hexanol and 80%（by volume）of neat cashew nut shell biodiesel was referred to as CNSBD800 H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at10% and 20%（by volume） to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.
基金Project supported by T.R.Prime Ministry State Planning Organization,Turkey
文摘In this study, an electro-mechanical valve （EMV） system for the intake valve ofa fottr stroke, single cylinder, overhead valve and spark ignition （SI） engine was designed and constructed. An engine with the EMV system and a standard engine were tested to observe the effects of the EMV on engine performance and emissions at different speeds under full load. The EMV engine showed improved engine power, engine torque and break specific fuel consumption （BSFC）. A 66% decrease in CO emissions was also obtained with the EMV system, but hydrocarbons （HC） and NOx emissions increased by 12% and 13% respectively.
基金supported by the National Natural Science Foundation of China(Grant 11002148)
文摘A dual-mode scramjet can operate in a wide range of flight conditions. Higher thrust can be generated by adopting suitable combustion modes. Based on the net thrust, an analysis and preliminary optimal design of a kerosene-fueled parameterized dual-mode scramjet at a cru- cial flight Mach number of 6 were investigated by using a modified quasi-one-dimensional method and simulated annealing strategy. Engine structure and heat release distrib- utions, affecting the engine thrust, were chosen as analytical parameters for varied inlet conditions （isolator entrance Mach number： 1.5-3.5）. Results show that different opti- mal heat release distributions and structural conditions can be obtained at five different inlet conditions. The highest net thrust of the parameterized dual-mode engine can be achieved by a subsonic combustion mode at an isolator entrance Mach number of 2.5. Additionally, the effects of heat release and scramjet structure on net thrust have been discussed. The present results and the developed analytical method can provide guidance for the design and optimization of high-performance dual-mode scramjets.
文摘This work focuses on blending Jatropha oil with diesel fuel and heptane to improve its physico-chemical characteristics for production of blends and their use as fuel in a diesel engine. The influence of the heptane content was evaluated by comparing the results obtained from the engine (performance and combustion parameters) with those of the diesel fuel and straight Jatropha oil. The results obtained show an improvement in engine performance especially at low loads. Specifically, a reduction in the specific fuel consumption of the engine is obtained when the heptane content in the mixture is around 10% compared to that obtained with pure Jatropha oil. The best results were obtained with the blend containing 70% Jatropha oil, 20% diesel fuel and 10% heptane (J70G20H10). Overall engine efficiency and exhaust gas temperatures are comparable for all fuels tested. Engine combustion parameters are improved with J70G20H10. The results obtained with J70G20H10 are close to those of the engine operating on diesel fuel. The cyclic dispersion is low with coefficients of variation of the indicated mean effective pressure (COV<sub>IMEP</sub>) whose values are less than 10%. The lowest values of the COV<sub>IMEP</sub> are obtained with the blend J70G20H10.
文摘This paper adopts American National Instruments (NI) Company’s LabVIEW and LabVIEW RT virtual instrument softwareplatform and lots of things for this engine performance LabVIEW virtual instrument test system, such as the matched NI PCI dataCollection Card, NI SCXI signal-adjusting instrument and NI compact FieldPoint (cFP) distributed I/O real time system hardware.This system has realized multi performances’parallel test; and it can complete load, torsional moment, rotate speed, power, pressureand temperature’s real time monitoring automatically according to user’s setting; and finally through TCP/IP protocol it realizes testdata’s teleshare and telecontrol that user put on the test system. This system has such character as short development period, highuse efficiency and low cost, at the same time it has strong extensibility and reusability, so it has very high applied cost.
文摘Increasing global environmental issues and depleting fossil fuel reserves has necessitated the need for alternative and sustainable fuel. In this paper, the effects of biodiesel and its blend on engine emission and performance characteristics in an internal combustion engine were analyzed. Biodiesel derived from the transesterification of raw palm oil was blended with diesel fuel at different proportions designated as PO5 (5% Biodiesel and 95% Diesel), PO10 (10% Biodiesel and 90% Diesel), PO15 (15% Biodiesel and 85% Diesel), PO20 (20% Biodiesel and 80% Diesel), PO50 (50% Biodiesel and 50% Diesel), PO85 (85% Biodiesel and 15% Diesel), and PO100 (100% Biodiesel). A Lombardini 2-cylinder, four-stroke direct injection diesel engine with a compression ratio of 22.8 was developed using Ricardo Wave software in which diesel, palm oil biodiesel blends and pure biodiesel are used in the model, and the obtained results were analysed and presented. The simulation was done under varying engine speeds of 1200 rpm to 3200 rpm at full load condition. Biodiesel and its blends are more environment-friendly and non-toxic when compared to diesel fuel;it also improves the mechanical efficiency of the engines, and above all can also lead to a reduction in poverty among rural dwellers. The obtained results showed that brake specific fuel consumption and brake thermal efficiency increased with palm oil biodiesel blends as compared to diesel fuel which might be a result of biodiesel’s lower heating value, and the increase in thermal energy may be a result of the oxygenation of the biodiesel blend as compared to pure diesel. In terms of brake torque, palm oil biodiesel blends were lesser than diesel fuel. The CO, HC, and NO<sub>x</sub> emissions of palm oil biodiesel blends decreased significantly compared to that of pure diesel. From this study, palm oil biodiesel emits lesser emissions than diesel fuel and its performance characteristics are similar to diesel fuel. Therefore, palm oil biodiesel can be used without any modifications directly in a diesel engine. In addition, it can also be used as blends as an alternative and sustainable fuel, decreasing air pollution, and increasing environmental sustainability.
基金Project supported by National Natural Science Foundation of China (50405047)Natural Science foundation of Shandong Province (Y2005F04)Jinan Young Star Plan of Science and Technology (08108)
文摘Development and application of new ceramic die materials is one of the important topics in the field of die research. The composition, processing technology, mechanical property and engineering performance of the ceramic materials such as cermet, ZTA, TZP, TZP/Al2O3, TZP/TiC/Al2O3, PSZ and Sialon, etc., with rare earth yttrium, lanthanum and cerium, and so on working as additives, were investigated and analyzed in the present study. Problems existed in the research and application of rare earth ceramic die materials were discussed. Rare earth additives can effectively improve the mechanical property and engineering performance of ceramic die materials. Thus, it will have further perspectives of wider application. More attention should be paid in the future to the toughening and strengthening of the ceramic die materials, the adding forms and kinds of rare earth elements and acting mechanisms of rare earth additives in ceramic die materials.
基金supported in part by the National Science and Technology Major Project,China(No.2017-V-0004-0054)in part by the Research on the Basic Problem of Intelligent Aeroengine,China(No.2017-JCJQ-ZD-047-21)+1 种基金in part by the Fundamental Research Funds for the Central Universities,China(No.NZ2020002)in part by the National Natural Science Foundation of China(No.51906102)。
文摘Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control(LADRC)is proposed.Firstly,based on CFD numerical simulation,aerodynamic performance model of AVEN is established,and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed.Subsequently,the integrated model of AVEN/-turbofan engine is established by Simulink/AMESim co-simulation.Finally,the nozzle throat area control loop based on LADRC is designed.The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system.The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%,indicating a high degree of confidence.Compared with the conventional PID control,the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%,which effectively improves the control stability of the vector deflection.Meanwhile,the fuel flow ratechange during the vector deflection process is smaller and more economical,which provides an important reference for engineering applications.
文摘Part of an extensive research undertaken by the Concrete and Masonry Research Group at Kingston University-London was reported to demonstrate through scientific research and full-scale site trials,that quality recycled concrete aggregates can be produced and can be used successfully in a range of concrete applications.The effects of up to 100% coarse recycled concrete aggregate（RCA） on fresh,engineering and durability related properties were established and assessed its suitability for use in a rage of sustainable applications.
基金This project is supported by National Innovation Foundation for TechnologyBased Firms, China (No.01C26213300872).
文摘The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.
基金Sponsored by the National Natural Science Foundation of China (50576063)
文摘The development of a diesel engine model using one-dimensional （1-D） fluid-dynamic engine simulation codes,and its validation using experimental measurements are described in this paper.The model was calibrated by running the engine on an electric dynamometer at eight steady-state operating conditions.The refined engine model was used to predict the oxides of nitrogen （NOx） less than those measured earlier in the experiments,and hence to recommend changes in the engine for the verification of the results.The refined engine model is greatly influenced by the start of injection angle （ψ）,ignition delay （φ）,premix duration （DP）,and main duration （DM） for the prediction of reduced NOx emissions.It is found that optimum ψ is 6.5° before top dead center （BTDC）.At this angle,the predicted and experimental results are in good agreement,showing only a difference of up to 4%,6.2%,and 7.5% for engine performance,maximum combustion pressure （Pmax）,and NOx,respectively.
基金supported in part by the National Natural Science Foundation of China (Nos. 51906102 and 52176009)the National Science and Technology Major Project, China (Nos. J2019-II-0009-0053, J2019-I-0020-0019 and 2019III-0014-0058)+2 种基金the Innovation Centre for Advanced Aviation Power, China (Nos. HKCX2020-02-022 and HKCX2020-02-027)the Research on the Basic Problem of Intelligent Aero-engine, China (No. 2017-JCJQZD-047-21)the Fundamental Research Funds for the Central Universities, China (No. NZ2020002)
文摘To reduce the propulsion system installation thrust loss under high angle of attack maneuvering,a control method based on real-time optimization of the integrated aeropropulsion is proposed.Firstly,based on data fitting and physical principle,an integrated onboard model of propulsion system is established,which can calculate various performance parameters of the propulsion system in real time,and has high accuracy and real-time performance.Secondly,to improve the compatibility of optimization real-time performance and search accuracy,the online optimization control of aero-propulsion system is realized based on an improved trust region algorithm.Finally,by controlling the auxiliary intake valve,a good match between inlet and engine is realized,which solves the problems of intake flow reducing and total pressure recovery coefficient declining,and improves the installation performance of propulsion system.The simulation results indicate that,compared with the conventional independent engine control,the real-time integrated optimization method reduces the installed thrust loss by 3.61%under the design condition,and 4.58%under the off-design condition.Furthermore,the simulation on HIL(Hardware-In-theLoop)platform verifies the real-time performance of integrated optimization method.
基金This research project was supported by a grant from the“Research Center of College of Computer and Information Sciences”,Deanship of Scientific Research,King Saud University.
文摘The expanding amounts of information created by Internet of Things(IoT)devices places a strain on cloud computing,which is often used for data analysis and storage.This paper investigates a different approach based on edge cloud applications,which involves data filtering and processing before being delivered to a backup cloud environment.This Paper suggest designing and implementing a low cost,low power cluster of Single Board Computers(SBC)for this purpose,reducing the amount of data that must be transmitted elsewhere,using Big Data ideas and technology.An Apache Hadoop and Spark Cluster that was used to run a test application was containerized and deployed using a Raspberry Pi cluster and Docker.To obtain system data and analyze the setup’s performance a Prometheusbased stack monitoring and alerting solution in the cloud based market is employed.This Paper assesses the system’s complexity and demonstrates how containerization can improve fault tolerance and maintenance ease,allowing the suggested solution to be used in industry.An evaluation of the overall performance is presented to highlight the capabilities and limitations of the suggested architecture,taking into consideration the suggested solution’s resource use in respect to device restrictions.
文摘With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth-quakes.This study presents a novel comprehensive probabilistic framework to quantify the environmental impact of buildings,including uncertainties in the material extraction and production,transportation,construction,seis-mic exposure and aging(including deterioration),and end-of-life stages.The developed framework is used to quantify the environmental impact of a 3-story residential building located in Vancouver,Canada.The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment.If the prototype building is hit by the design level earthquake,it is expected that the median environmental impact of the prototype will be further increased by 42%.In addition,by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building,the earthquake related damage will result in an additional 5%of the initial carbon emission of the building.This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.
文摘<span style="font-family:Verdana;">In the efforts to reduce effects of climate change, biodiesel fuels from plant oils such as </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> have been proposed as alternative fuels which can be used in the transportation sector in diesel engines. The current study investigates the effects of fatty acids composition on fuel properties of biodiesel derived from </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> seeds obtained from selected regions of Botswana. The physicochemical fuel properties investigated include kinematic viscosity, flash point, energy content, density, pour point and cloud point from derived </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel. Results of the study showed that </span><i><span style="font-family:Verdana;">Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel samples for all regions under review are dominated by unsaturated fatty acids which are desirable for cold flow properties and kinematic viscosity of the biodiesel fuel. The major fatty acids in</span><i><span style="font-family:Verdana;"> Jatropha curcas</span></i><span style="font-family:Verdana;"> biodiesel fuels from all the regions range </span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">from</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> 69.00% to 77.81% of unsaturated fatty acids. The overall results conclude that fatty acids composition has influence on the fuel properties of the biodiesel under investigated.</span></span></span>
文摘The purpose of carrying out present work is to design, build and test a rhombic drive Stirling engine with a β-type configuration consisting of two dynamic pistons (displacer and power) reciprocates in the in-line concentric cylinder arrangement. The displacement rod is assembled concentrically inside the power piston rod. The rhombic drive mechanism is proposed in such a way that, by using a pair of gear wheels the sliding motion of both piston rods is controlled and thus, an engine is balanced. The developed prototype has a swept volume of 75 cm<sup>3</sup> with the displacer piston and power piston cylinder hot ends heated by liquefied petroleum gas (LPG) burner and cooled water, respectively. It uses air as the working gas at atmospheric pressure for initial charging of the engine. Several designs were studied before settling on a β-type configuration. The LPG gas burner was considered as a potential heat source. The various elements of an engine (heater, cooler, re-generator, flywheel and piping systems) were designed, constructed and analyzed. The testing results revealed that the engine at initial atmospheric air filling started working in only about 120 seconds at an LPG heater temperature of 400℃ (824<sup>°</sup>F) with 280 rpm. At a heater temperature of 550℃ (1022<sup>°</sup>F), the engine speed was 630 rpm. At the engine speed of 245 rpm, the maximum torque was 0.215 Nm, while the maximum power was 8 Watts at 355 rpm. Engine speed increased with the increase of flame temperature. Several tests were performed on the engine to improve its running efficiency and critical problem areas were isolated and addressed. Moreover, results revealed that Stirling engines working with relatively low-temperature air are potentially attractive engines of the future, especially LPG powered low temperature differential Stirling engines. The Stirling engine was capable of generating between 50 to 100 Watts of electricity.
