According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarator...According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarators.Using the constructed 0D model,the results obtained in this study under the same conditions are compared and validated against reference results for pure hydrogen plasma start-up in tokamak.The results are in good agreement,especially regarding electron temperature,ion temperature and plasma current.In the presence of finite Ohmic electric field in the spherical tokamak,a study on the EC wave assisted start-up of the NCST plasma at frequency of 28 GHz is conducted.The impact of the vertical magnetic field B_(v)on EC wave assisted start-up,the relationship between EC wave injection power P_(inj),Ohmic electric field E,and initial hydrogen atom density n_(H0)are explored separately.It is found that under conditions of Ohmic electric field lower than ITER(~0.3 V m^(-1)),EC wave can expand the operational space to achieve better plasma parameters.Simulating the process of28 GHz EC wave start-up in the CN-H1 stellarator plasma,the plasma current in the zerodimensional model is replaced with the current in the poloidal coil of the stellarator.Plasma startup can be successfully achieved at injection powers in the hundreds of kilowatts range,resulting in electron densities on the order of 10^(17)-10^(18)m^(-3).展开更多
Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched rockets.In this paper,the ignition start-up process of an underwater solid rocket motor across a wide d...Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched rockets.In this paper,the ignition start-up process of an underwater solid rocket motor across a wide depth range has been numerically studied.A novel multi-domain integrated model has been developed by combining the solid propellant ignition and combustion model with the volume of fluid multiphase model.This integrated model enables the coupled simulation of the propellant combustion and gas flow inside the motor,along with the gas jet evolution in the external water environment.The detailed flow field developments in the combustion chamber,nozzle,and wake field are carefully analyzed.The variation rules of the internal ballistics and thrust performance are also obtained.The effects of environmental medium and operating depth on the ignition start-up process are systematically discussed.The results show that the influence of the operating environment on the internal ballistic characteristics is primarily reflected in the initial period after the nozzle closure opens.The development of the gas jet in water lags significantly compared with that in air.As the water depth increases,the ignition delay time of the motor is shortened,and the morphology evolution of the gas jet is significantly compressed and accelerated.Furthermore,the necking and bulging of the jet boundary near the nozzle outlet and the consequent shock oscillations are intensified,resulting in stronger fluctuations in the wake pressure field and motor thrust.展开更多
Microstructures and properties of mortar using ammonium phosphate and potassium phosphate were tested and compared in this case.Moreover,two cementitious additions and two lightweight aggregates,including fly ash,redi...Microstructures and properties of mortar using ammonium phosphate and potassium phosphate were tested and compared in this case.Moreover,two cementitious additions and two lightweight aggregates,including fly ash,redispersible latex powder,ceramsite sand,and rubber powder,were respectively tried to be applied in magnesium ammonium phosphate cement mortar in order to modify the microstructures and properties.The experimental results show that potassium phosphate is not suitable for magnesium phosphate cement mortar for cold region construction purpose.Although fly ash can bring positive modification in the condition of normal temperature curing,it brings negative effects in the condition of sub-zero temperature curing.Either redispersible latex powder or ceramsite sand can improve the freeze-thaw cycling resistance of magnesium phosphate cement mortar in the conditions of low temperature coupled with freeze-thaw cycling,but only the ceramsite sand can improve both mechanical properties and freeze-thaw cycling resistance.The modification caused by ceramsite sand is mainly due to the exceptional bonding strength between hardened cement paste and the porous surface of ceramsite and the porous structure of ceramsite for the release of frost heave stress.展开更多
The biotreatment of mine drainage containing dissolved manganese(Mn)using Mn(II)-oxidizing bacteria is challenging.Sequencing-batch(SBRs)and continuous-flow reactors(CFRs)packed with limestones and inoculated with the...The biotreatment of mine drainage containing dissolved manganese(Mn)using Mn(II)-oxidizing bacteria is challenging.Sequencing-batch(SBRs)and continuous-flow reactors(CFRs)packed with limestones and inoculated with the mine-drainage microbial communitywere compared to determine the removal efficiency of Mn(II)from mine drainage.Mn(II)removal in CFRs was 11.4%±0.0%(mean±standard deviation)in the first two weeks and;it slightly increased to 13.6%±0.0%after four weeks,and more than 94%of Mn(II)was removed under the steady-state treatment phase.The performance of SBRs was more effective,wherein 24.4%±0.1%of Mn was removed in the first two weeks,and in four weeks,surpassed 66.6%±0.2%.Rapid Mn(II)removal observed in the start-up of SBR resulted from higher microbial metabolic activities.The adenosine triphosphate(ATP)content of the microbial community was four-fold more than in CFR,but comparable during the steady-state phase.The Mn-oxide deposits occurring in the SBR and CFR at steady-state were mixed phases of birnessite and woodruffite,and the average Mn oxidation valence in the SBR(+3.73)was slightly higher than that in the CFR(+3.54).During the start-up treatment,the closest relatives of Methyloversatilis,Methylibium,and Curvibacter dominated the SBR,whereas putative Mn oxidizers were associated with Hyphomicrobium,Pedobacter,Pedomicrobium,Terricaulis sp.,Sulfuritalea,and Terrimonas organisms.The growth of potential Mnoxidizing genera,including Mesorhizobium,Rhodococcus,Hydrogenophaga,Terricaulis sp.,and‘Candidatus Manganitrophus-noduliformans’was observed under the steady state.The SBR operation was effective as a prior start-up treatment for mine drainage-containing Mn(II),through which the CFR performed well as posterior bio-treatment.展开更多
To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy stora...To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy storage,incorporating daily minimum chargeable energy constraints,was developed.Firstly,considering the variations in the frequency of unit start-ups and shutdowns under different levels of net load fluctuation,a method was proposed to reduce decision time periods for unit start-up and shut-down operations.This approach,based on the characteristics of net load fluctuations,minimizes the decision variables of units,thereby simplifying the monthly schedulingmodel.Secondly,the relationship between energy storage charging and discharging power,net load,and the total maximum/minimum output of units was analyzed.Based on this,daily minimum chargeable energy constraints were established to ensure the energy storage system meets charging requirements under extreme net load scenarios.Finally,taking into account the operational costs of thermal generators and energy storage,load loss costs,and operational constraints,the reduced time-period monthly schedulingmodel was constructed.Case studies demonstrate that the proposedmethod effectively generates economical monthly operation plans for thermal generators and energy storage,significantly reduces model solution time,and satisfies the charging requirements of energy storage under extreme net load conditions.展开更多
The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS ...The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS not complying with the contract target, etc. occurred during start-up and debugging of two 600 MW generating units in Yangzhou No.2 Thermal Power Plant. Through analysis on these problems. the remedial measures were put forward, to which can be referred for similar units.展开更多
The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal perc...The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal percentage of both ammonia and nitrite higher than 95% and volumetric total nitrogen removal as high as 149.55 mmol/(L·d). The soft padding made an important contribution to the high efficiency and stability because it held a large amount of biomass in the bioreactor.展开更多
N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL...N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL-containing AGSR supernatant into the continuously stirred tank reactors reduced the start-up time of the anammox process from80 to 66 days.Moreover,the nitrogen loading rate was also enhanced to 1.6 times that of the control reactor.AHLs could increase the secretion of extracellular polymeric substances and anammox obtained better enrichment with the addition of AHLs-containing AGSR supernatant.Denaturing gradient gel electrophoresis analysis further revealed that AHLs played a role in mediating microbial community parameters.In conclusion,adding AHL-containing supernatant could be an effective and economical way to accelerate the start-up of anammox.展开更多
Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding...Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding of cracking furnaces can be avoided if the cracking gas compressor is started and the refrigeration system is precooled in advance using mixed gas as the start-up working medium(SWM). Start-up scenario with mixed gas as SWM could significantly reduce the emission loss and shorten the precooling time. Research shows that making appropriate start-up scheme is important not only to ensure operational safety and feasibility, but also to reduce energy consumption. In this paper, a method is proposed to select suitable start-up operational parameters of compression and refrigeration system with sufficient safe operating ranges and short precooling time. The complex interrelation among key parameters of start-up is analyzed. It is found that higher energy consumption, especially for super high-pressure steam(SS), can promote operational safety and shorten the precooling time during start-up.Based on steady-state and dynamic simulation, appropriate operating parameter ranges are determined with reasonable SS consumption. A real case study demonstrates that an appropriate start-up scheme will optimize the operation.展开更多
As an efficient method for ammonium（NH4~＋）removal,contact catalytic oxidation technology has drawn much attention recently,due to its good low temperature resistance and short start-up period.Two identical filters ...As an efficient method for ammonium（NH4~＋）removal,contact catalytic oxidation technology has drawn much attention recently,due to its good low temperature resistance and short start-up period.Two identical filters were employed to compare the process for ammonium removal during the start-up period for ammonium removal in groundwater（Filter-N）and surface water（Filter-S）treatment.Two types of source water（groundwater and surface water）were used as the feed waters for the filtration trials.Although the same initiating method was used,Filter-N exhibited much better ammonium removal performance than Filter-S.The differences in catalytic activity among these two filters were probed using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,and compositional analysis.XRD results indicated that different manganese oxide species were formed in Filter-N and Filter-S.Furthermore,the Mn3p XPS spectra taken on the surface of the filter films revealed that the average manganese valence of the inactive manganese oxide film collected from Filter-S（FS-MnOx）was higher than in the film collected from Filter-N（FN-MnOx）.Mn（IV）was identified as the predominant oxidation state in FS-MnOxand Mn（III）was identified as the predominant oxidation state in FN-MnOx.The results of compositional analyses suggested that polyaluminum ferric chloride（PAFC）used during the surface water treatment was an important factor in the mineralogy and reactivity of MnOx.This study provides the theoretical basis for promoting the wide application of the technology and has great practical significance.展开更多
The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is ...The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network（ANN）inverse system and the two degrees of freedom（2-DOF） internal model controller（IMC）. The HS-BLDC motor is identified by the online least squares support vector machine（OLS-SVM） algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.展开更多
Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline electrolyte.High energy plas...Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline electrolyte.High energy plasma,however,inevitably generates porous structures that limit their practical performance.The present study proposes a straight-forward simple method by utilizing sub-zero electrolyte(268 K)to alter the plasma characteristics during formation of the protective coating on AZ31 Mg alloy via PEO with a comparison to the electrolyte at room temperature(298 K).In refrigerated electrolyte,the formation of micro-defects is suppressed relatively at the expense of low coating growth,which is measured to be twice lower than that at 298 K due to the temperature-dependent soft plasma discharges contributing to the development of the present coating.As a consequence,corrosion resistance of the sample processed at 268 K is superior to that of 298K,implying that the effect of coating thickness is less dominant than that of compactness.This phenomenon is interpreted in relation to the ionic movement and oxide solidification controlled by soft plasma discharges arising from the temperature gradient between electrolyte and surface of the substrate during PEO.展开更多
The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325℃and 400℃after austenitizing at...The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325℃and 400℃after austenitizing at 875℃and 950℃. The sub-zero treatments were carried out by cooling down the samples to -30℃, -70℃and -196℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875℃and austempered at 325℃remained unchanged, whilst it reduced in samples austenitized at 950℃and 875℃for austempering temperature of 400℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior.展开更多
The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady os...The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance.展开更多
Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 ...Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 - 24d） seeded with activated sludge, the butyric acid type-fermentation formed when the initial expanding rate, organic loading rate （OLR）, the initial redox potential （ORP） and hydraulic retention time （HRT） were 10%, 10.0 kg COD/（m^3·d）, -215 mV and 6.7 h, respectively. At the beginning of the second stage on day 25, the novel hydrogen-producing fermentative bacterial strain B49 （AF481148 in EMBL） were inoculated into the reactor under the condition of OLR 16. 0 kg COD/（m^3·d）, ORP and HRT about - 139 mV and 6.7 h, respectively, and then the reaction system transformed to ethanol-type fermentation gradually with the increase in OLR. When OLR, ORP and HRT were about 94.3 kg COD/（m^3·d）, -250 mV and 1.7 h, respectively, the system achieved the maximum hydrogen-producing rate of 282.6 mL H2/L reactor·h and hydrogen percentage of 51% -53% in the biogas.展开更多
This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful...This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy.To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions.Thus,the shorter the start-up time,the better for the environment and economy.High-pressure(HP)part of the turbine originally located on the Queen Elizabeth II unit was analysed.Advanced numerical calculations by thermal fluid-solid-interaction(Thermal FSI)were carried out.A series of simulations were performed for the accelerated start-up with controlled steam injection.A description of the chosen calculation methodology and the results obtained by simulation are included in this paper.The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up.The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm(0.83 mm for ultra-fast start-up).Reducing the steam turbine start-up time by 75%results in a 36.7 tons reduction in fuel consumption for start-up,resulting in an annual savings of 5372 USD.In conclusion,the concept proposed by the authors is safe,less expensive and does not affect the life of the turbine.In addition,results and applications from Siemens prove that additional injection of cooling steam is possible.展开更多
A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed （JBILAFB）, was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose w...A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed （JBILAFB）, was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose wastewater treatment. With the wastewater recycle ratio of 2.5 ： 1, the recycled wastewater with biogas could mix sludge and wastewater in the JBILAFB reactor completely. The start-up of the JBILAFB reactor could be completed in less than 70 d through maintenance of hydraulic retention time （HR^I＂） and stepwise increase of feed total organic carbon （TOC） concentration. After the start-up, with the volumetric TOC loadings of 14.3 kg·m ^-3·d^-1, the TOC removal ratio, the effluent pH, and the volatile fatty acids （VFA）/alkalinity of the JBILAFB reactor were more than 80%, close to 7.0 and less than 0.4, respectively. Moreover, CH4 was produced at more than 70% of the theoretical value, The reactor exhibited high stability under the condition of high volumetric TOC loading. Sludge granules in the JBILAFB reactor were developed during the start-up and their sizes were enlarged with the stepwise increase of volumetric TOC loadings from 0.8 kg.m^-3.d ^-1 to 14.3 kg.m^-3.d^-1. Granules, an offwhite color and a similar spherical shape, were mainly comprised of global-like bacteria. These had good methanogenic activity and settleability, which were formed probably through adhesion of the bacteria. Some inorganic metal compounds such as Fe, Ca, Mg, Al, etc. were advantageous to the formation of the granules.展开更多
In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-...In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-up pressure wave speeds under various operation conditions were measured,and effects of correlative factors on pressure wave were analyzed.The experimental and theoretical analysis shows that thermal shrinkage and structural properties of gelled crude oils are key factors influencing on start-up pressure wave propagation.The quantitative analysis for these effects can be done by using volume expansion coefficient and structural property parameter of gelled crude oil.A new calculation model of pressure wave speed was developed on the basis of Large-scale flow loop experiment and theoretical analysis.展开更多
We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear ...We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear flow Wi=12.6, the shear stress proportionally increases with shear strain at short times, followed by a strain hardening behavior and then passes through a maximum(σmax, γmax) and finally decreases until it reaches the steady state. During the evolution of stress, the gel network is only slightly broken and essentially maintains its framework, and the strain hardening behavior originates from the excessive stretching of chains. On the other hand, the stress-strain curve at intermediate shear flow Wi=505.6 shows two differences from that at Wi=12.6, namely, the absence of strain hardening and a dramatic increase of stress at large strains,which is caused by the rupture of gel network at small strains and the network recovery at large strains, respectively. Finally, at very strong shear flow Wi=6319.7, the gel network is immediately broken by shear flow and the stress-strain curve exhibits similar behaviors to those of classical polymeric liquids.展开更多
In this work, the influence of sub-zero Celsius treatment and tempering on the mechanical and thermal stability of retained austenite in beating steel were assessed by tensile test and DSC. Compared with traditional q...In this work, the influence of sub-zero Celsius treatment and tempering on the mechanical and thermal stability of retained austenite in beating steel were assessed by tensile test and DSC. Compared with traditional quenched and tempered treatment, sub-zero Celsius treatment obviously decreases the volume fraction of retained austenite. Moreover, the mechanical stability of retained austenite was enhanced due to the accumulation of compressive stresses in retained austenite after sub-zero Celsius treatment and tempering. Meanwhile, the morphology of retained austenite changed from film-like to blocky with austenitization temperature increasing, and the mechanical stability of film-like retained austenite is higher than that of blocky one. The DSC results showed that the activation energy of retained austenite decomposition slightly increased through sub-zero Celsius treatment and tempering. This result may probably be ascribed to partitioning of carbon during tempering. However, the temperature at which retained austenite starts to decompose is unchanged.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFE03070000 and 2022YFE03070003)National Natural Science Foundation of China(Nos.12375220 and 12075114)。
文摘According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarators.Using the constructed 0D model,the results obtained in this study under the same conditions are compared and validated against reference results for pure hydrogen plasma start-up in tokamak.The results are in good agreement,especially regarding electron temperature,ion temperature and plasma current.In the presence of finite Ohmic electric field in the spherical tokamak,a study on the EC wave assisted start-up of the NCST plasma at frequency of 28 GHz is conducted.The impact of the vertical magnetic field B_(v)on EC wave assisted start-up,the relationship between EC wave injection power P_(inj),Ohmic electric field E,and initial hydrogen atom density n_(H0)are explored separately.It is found that under conditions of Ohmic electric field lower than ITER(~0.3 V m^(-1)),EC wave can expand the operational space to achieve better plasma parameters.Simulating the process of28 GHz EC wave start-up in the CN-H1 stellarator plasma,the plasma current in the zerodimensional model is replaced with the current in the poloidal coil of the stellarator.Plasma startup can be successfully achieved at injection powers in the hundreds of kilowatts range,resulting in electron densities on the order of 10^(17)-10^(18)m^(-3).
基金supported by the National Level Project of China.
文摘Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched rockets.In this paper,the ignition start-up process of an underwater solid rocket motor across a wide depth range has been numerically studied.A novel multi-domain integrated model has been developed by combining the solid propellant ignition and combustion model with the volume of fluid multiphase model.This integrated model enables the coupled simulation of the propellant combustion and gas flow inside the motor,along with the gas jet evolution in the external water environment.The detailed flow field developments in the combustion chamber,nozzle,and wake field are carefully analyzed.The variation rules of the internal ballistics and thrust performance are also obtained.The effects of environmental medium and operating depth on the ignition start-up process are systematically discussed.The results show that the influence of the operating environment on the internal ballistic characteristics is primarily reflected in the initial period after the nozzle closure opens.The development of the gas jet in water lags significantly compared with that in air.As the water depth increases,the ignition delay time of the motor is shortened,and the morphology evolution of the gas jet is significantly compressed and accelerated.Furthermore,the necking and bulging of the jet boundary near the nozzle outlet and the consequent shock oscillations are intensified,resulting in stronger fluctuations in the wake pressure field and motor thrust.
基金Funded by the National Natural Science Foundation of China(No.51878227)。
文摘Microstructures and properties of mortar using ammonium phosphate and potassium phosphate were tested and compared in this case.Moreover,two cementitious additions and two lightweight aggregates,including fly ash,redispersible latex powder,ceramsite sand,and rubber powder,were respectively tried to be applied in magnesium ammonium phosphate cement mortar in order to modify the microstructures and properties.The experimental results show that potassium phosphate is not suitable for magnesium phosphate cement mortar for cold region construction purpose.Although fly ash can bring positive modification in the condition of normal temperature curing,it brings negative effects in the condition of sub-zero temperature curing.Either redispersible latex powder or ceramsite sand can improve the freeze-thaw cycling resistance of magnesium phosphate cement mortar in the conditions of low temperature coupled with freeze-thaw cycling,but only the ceramsite sand can improve both mechanical properties and freeze-thaw cycling resistance.The modification caused by ceramsite sand is mainly due to the exceptional bonding strength between hardened cement paste and the porous surface of ceramsite and the porous structure of ceramsite for the release of frost heave stress.
基金funded by the JOGMEC Research Grant and JSPS KAKENHI(No.JP21H03636).
文摘The biotreatment of mine drainage containing dissolved manganese(Mn)using Mn(II)-oxidizing bacteria is challenging.Sequencing-batch(SBRs)and continuous-flow reactors(CFRs)packed with limestones and inoculated with the mine-drainage microbial communitywere compared to determine the removal efficiency of Mn(II)from mine drainage.Mn(II)removal in CFRs was 11.4%±0.0%(mean±standard deviation)in the first two weeks and;it slightly increased to 13.6%±0.0%after four weeks,and more than 94%of Mn(II)was removed under the steady-state treatment phase.The performance of SBRs was more effective,wherein 24.4%±0.1%of Mn was removed in the first two weeks,and in four weeks,surpassed 66.6%±0.2%.Rapid Mn(II)removal observed in the start-up of SBR resulted from higher microbial metabolic activities.The adenosine triphosphate(ATP)content of the microbial community was four-fold more than in CFR,but comparable during the steady-state phase.The Mn-oxide deposits occurring in the SBR and CFR at steady-state were mixed phases of birnessite and woodruffite,and the average Mn oxidation valence in the SBR(+3.73)was slightly higher than that in the CFR(+3.54).During the start-up treatment,the closest relatives of Methyloversatilis,Methylibium,and Curvibacter dominated the SBR,whereas putative Mn oxidizers were associated with Hyphomicrobium,Pedobacter,Pedomicrobium,Terricaulis sp.,Sulfuritalea,and Terrimonas organisms.The growth of potential Mnoxidizing genera,including Mesorhizobium,Rhodococcus,Hydrogenophaga,Terricaulis sp.,and‘Candidatus Manganitrophus-noduliformans’was observed under the steady state.The SBR operation was effective as a prior start-up treatment for mine drainage-containing Mn(II),through which the CFR performed well as posterior bio-treatment.
基金This study was supported by State Grid Corporation headquarters technology project(4000-202399368A-2-2-ZB).
文摘To address the excessive complexity of monthly scheduling and the impact of uncertain net load on the chargeable energy of storage,a reduced time-period monthly scheduling model for thermal generators and energy storage,incorporating daily minimum chargeable energy constraints,was developed.Firstly,considering the variations in the frequency of unit start-ups and shutdowns under different levels of net load fluctuation,a method was proposed to reduce decision time periods for unit start-up and shut-down operations.This approach,based on the characteristics of net load fluctuations,minimizes the decision variables of units,thereby simplifying the monthly schedulingmodel.Secondly,the relationship between energy storage charging and discharging power,net load,and the total maximum/minimum output of units was analyzed.Based on this,daily minimum chargeable energy constraints were established to ensure the energy storage system meets charging requirements under extreme net load scenarios.Finally,taking into account the operational costs of thermal generators and energy storage,load loss costs,and operational constraints,the reduced time-period monthly schedulingmodel was constructed.Case studies demonstrate that the proposedmethod effectively generates economical monthly operation plans for thermal generators and energy storage,significantly reduces model solution time,and satisfies the charging requirements of energy storage under extreme net load conditions.
文摘The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS not complying with the contract target, etc. occurred during start-up and debugging of two 600 MW generating units in Yangzhou No.2 Thermal Power Plant. Through analysis on these problems. the remedial measures were put forward, to which can be referred for similar units.
文摘The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal percentage of both ammonia and nitrite higher than 95% and volumetric total nitrogen removal as high as 149.55 mmol/(L·d). The soft padding made an important contribution to the high efficiency and stability because it held a large amount of biomass in the bioreactor.
基金supported by the Major State Science and Technology Water Projects (No. 2013ZX07202010)
文摘N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL-containing AGSR supernatant into the continuously stirred tank reactors reduced the start-up time of the anammox process from80 to 66 days.Moreover,the nitrogen loading rate was also enhanced to 1.6 times that of the control reactor.AHLs could increase the secretion of extracellular polymeric substances and anammox obtained better enrichment with the addition of AHLs-containing AGSR supernatant.Denaturing gradient gel electrophoresis analysis further revealed that AHLs played a role in mediating microbial community parameters.In conclusion,adding AHL-containing supernatant could be an effective and economical way to accelerate the start-up of anammox.
基金Supported by the National Basic Research Program of China(2012CB720500)the National Natural Science Foundation of China(U1462206)
文摘Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding of cracking furnaces can be avoided if the cracking gas compressor is started and the refrigeration system is precooled in advance using mixed gas as the start-up working medium(SWM). Start-up scenario with mixed gas as SWM could significantly reduce the emission loss and shorten the precooling time. Research shows that making appropriate start-up scheme is important not only to ensure operational safety and feasibility, but also to reduce energy consumption. In this paper, a method is proposed to select suitable start-up operational parameters of compression and refrigeration system with sufficient safe operating ranges and short precooling time. The complex interrelation among key parameters of start-up is analyzed. It is found that higher energy consumption, especially for super high-pressure steam(SS), can promote operational safety and shorten the precooling time during start-up.Based on steady-state and dynamic simulation, appropriate operating parameter ranges are determined with reasonable SS consumption. A real case study demonstrates that an appropriate start-up scheme will optimize the operation.
基金supported by the National Key Research and Development Program of China (No. 2016YFC0400706)the National Natural Science Foundation of China (Nos. 51278409, 51608431, 51408469)the Key Laboratory of Education Department of Shaanxi province (Nos. 15JS046, 16JS060)
文摘As an efficient method for ammonium（NH4~＋）removal,contact catalytic oxidation technology has drawn much attention recently,due to its good low temperature resistance and short start-up period.Two identical filters were employed to compare the process for ammonium removal during the start-up period for ammonium removal in groundwater（Filter-N）and surface water（Filter-S）treatment.Two types of source water（groundwater and surface water）were used as the feed waters for the filtration trials.Although the same initiating method was used,Filter-N exhibited much better ammonium removal performance than Filter-S.The differences in catalytic activity among these two filters were probed using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,and compositional analysis.XRD results indicated that different manganese oxide species were formed in Filter-N and Filter-S.Furthermore,the Mn3p XPS spectra taken on the surface of the filter films revealed that the average manganese valence of the inactive manganese oxide film collected from Filter-S（FS-MnOx）was higher than in the film collected from Filter-N（FN-MnOx）.Mn（IV）was identified as the predominant oxidation state in FS-MnOxand Mn（III）was identified as the predominant oxidation state in FN-MnOx.The results of compositional analyses suggested that polyaluminum ferric chloride（PAFC）used during the surface water treatment was an important factor in the mineralogy and reactivity of MnOx.This study provides the theoretical basis for promoting the wide application of the technology and has great practical significance.
基金co-supported by the National Major Project for the Development and Application of Scientific Instrument Equipment of China (No. 2012YQ040235)
文摘The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network（ANN）inverse system and the two degrees of freedom（2-DOF） internal model controller（IMC）. The HS-BLDC motor is identified by the online least squares support vector machine（OLS-SVM） algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.
基金the Mid-Level Researcher National Project of the National Research Foundation(NRF)funded by the Ministry of Science and ICT,Republic of Korea(NRF-2020R1A2C2004192)supported partly by the Competency Development Program for Industry Specialist of the Korea Institute for Advancement of Technology(KIAT)funded by the Ministry of Trade,Industry,and Energy,Republic of Korea(P0002019)。
文摘Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline electrolyte.High energy plasma,however,inevitably generates porous structures that limit their practical performance.The present study proposes a straight-forward simple method by utilizing sub-zero electrolyte(268 K)to alter the plasma characteristics during formation of the protective coating on AZ31 Mg alloy via PEO with a comparison to the electrolyte at room temperature(298 K).In refrigerated electrolyte,the formation of micro-defects is suppressed relatively at the expense of low coating growth,which is measured to be twice lower than that at 298 K due to the temperature-dependent soft plasma discharges contributing to the development of the present coating.As a consequence,corrosion resistance of the sample processed at 268 K is superior to that of 298K,implying that the effect of coating thickness is less dominant than that of compactness.This phenomenon is interpreted in relation to the ionic movement and oxide solidification controlled by soft plasma discharges arising from the temperature gradient between electrolyte and surface of the substrate during PEO.
文摘The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325℃and 400℃after austenitizing at 875℃and 950℃. The sub-zero treatments were carried out by cooling down the samples to -30℃, -70℃and -196℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875℃and austempered at 325℃remained unchanged, whilst it reduced in samples austenitized at 950℃and 875℃for austempering temperature of 400℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior.
文摘The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance.
文摘Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 - 24d） seeded with activated sludge, the butyric acid type-fermentation formed when the initial expanding rate, organic loading rate （OLR）, the initial redox potential （ORP） and hydraulic retention time （HRT） were 10%, 10.0 kg COD/（m^3·d）, -215 mV and 6.7 h, respectively. At the beginning of the second stage on day 25, the novel hydrogen-producing fermentative bacterial strain B49 （AF481148 in EMBL） were inoculated into the reactor under the condition of OLR 16. 0 kg COD/（m^3·d）, ORP and HRT about - 139 mV and 6.7 h, respectively, and then the reaction system transformed to ethanol-type fermentation gradually with the increase in OLR. When OLR, ORP and HRT were about 94.3 kg COD/（m^3·d）, -250 mV and 1.7 h, respectively, the system achieved the maximum hydrogen-producing rate of 282.6 mL H2/L reactor·h and hydrogen percentage of 51% -53% in the biogas.
文摘This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy.To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions.Thus,the shorter the start-up time,the better for the environment and economy.High-pressure(HP)part of the turbine originally located on the Queen Elizabeth II unit was analysed.Advanced numerical calculations by thermal fluid-solid-interaction(Thermal FSI)were carried out.A series of simulations were performed for the accelerated start-up with controlled steam injection.A description of the chosen calculation methodology and the results obtained by simulation are included in this paper.The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up.The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm(0.83 mm for ultra-fast start-up).Reducing the steam turbine start-up time by 75%results in a 36.7 tons reduction in fuel consumption for start-up,resulting in an annual savings of 5372 USD.In conclusion,the concept proposed by the authors is safe,less expensive and does not affect the life of the turbine.In addition,results and applications from Siemens prove that additional injection of cooling steam is possible.
基金Supported by the National Natural Science Foundation of China （No.50278036）, the Natural Science Foundation of Guangdong Province （No.04105951） and the National High Technology Research and Development Program of China （No.2006AA06Z378）.
文摘A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed （JBILAFB）, was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose wastewater treatment. With the wastewater recycle ratio of 2.5 ： 1, the recycled wastewater with biogas could mix sludge and wastewater in the JBILAFB reactor completely. The start-up of the JBILAFB reactor could be completed in less than 70 d through maintenance of hydraulic retention time （HR^I＂） and stepwise increase of feed total organic carbon （TOC） concentration. After the start-up, with the volumetric TOC loadings of 14.3 kg·m ^-3·d^-1, the TOC removal ratio, the effluent pH, and the volatile fatty acids （VFA）/alkalinity of the JBILAFB reactor were more than 80%, close to 7.0 and less than 0.4, respectively. Moreover, CH4 was produced at more than 70% of the theoretical value, The reactor exhibited high stability under the condition of high volumetric TOC loading. Sludge granules in the JBILAFB reactor were developed during the start-up and their sizes were enlarged with the stepwise increase of volumetric TOC loadings from 0.8 kg.m^-3.d ^-1 to 14.3 kg.m^-3.d^-1. Granules, an offwhite color and a similar spherical shape, were mainly comprised of global-like bacteria. These had good methanogenic activity and settleability, which were formed probably through adhesion of the bacteria. Some inorganic metal compounds such as Fe, Ca, Mg, Al, etc. were advantageous to the formation of the granules.
基金Project(2008B-2901) supported by China National Petroleum Corporation
文摘In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-up pressure wave speeds under various operation conditions were measured,and effects of correlative factors on pressure wave were analyzed.The experimental and theoretical analysis shows that thermal shrinkage and structural properties of gelled crude oils are key factors influencing on start-up pressure wave propagation.The quantitative analysis for these effects can be done by using volume expansion coefficient and structural property parameter of gelled crude oil.A new calculation model of pressure wave speed was developed on the basis of Large-scale flow loop experiment and theoretical analysis.
基金financially supported by the National Natural Science Foundation of China (Nos. 21873092, 21774127,21790341, 21790342)the Key Research Program of Frontier Sciences+1 种基金CAS (No. QYZDY-SSW-SLH027)the Jilin Provincial science and technology development program (No.20190103115JH)。
文摘We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear flow Wi=12.6, the shear stress proportionally increases with shear strain at short times, followed by a strain hardening behavior and then passes through a maximum(σmax, γmax) and finally decreases until it reaches the steady state. During the evolution of stress, the gel network is only slightly broken and essentially maintains its framework, and the strain hardening behavior originates from the excessive stretching of chains. On the other hand, the stress-strain curve at intermediate shear flow Wi=505.6 shows two differences from that at Wi=12.6, namely, the absence of strain hardening and a dramatic increase of stress at large strains,which is caused by the rupture of gel network at small strains and the network recovery at large strains, respectively. Finally, at very strong shear flow Wi=6319.7, the gel network is immediately broken by shear flow and the stress-strain curve exhibits similar behaviors to those of classical polymeric liquids.
基金financially supported by the National Basic Research Program of China (No. 2011CB706604)National Natural Science Foundation of China (No. 51174251 and 51201105)
文摘In this work, the influence of sub-zero Celsius treatment and tempering on the mechanical and thermal stability of retained austenite in beating steel were assessed by tensile test and DSC. Compared with traditional quenched and tempered treatment, sub-zero Celsius treatment obviously decreases the volume fraction of retained austenite. Moreover, the mechanical stability of retained austenite was enhanced due to the accumulation of compressive stresses in retained austenite after sub-zero Celsius treatment and tempering. Meanwhile, the morphology of retained austenite changed from film-like to blocky with austenitization temperature increasing, and the mechanical stability of film-like retained austenite is higher than that of blocky one. The DSC results showed that the activation energy of retained austenite decomposition slightly increased through sub-zero Celsius treatment and tempering. This result may probably be ascribed to partitioning of carbon during tempering. However, the temperature at which retained austenite starts to decompose is unchanged.
