为得到准确的离心喷嘴气涡固有声学频率,通过renormalization group(RNG)k-ε湍流模型和volume of fluid(VOF)气液两相流模型进行数值仿真研究。仿真结果表明将离心喷嘴与喷嘴出口锥形液膜视为一个声学系统可准确预测固有声学频率,修正...为得到准确的离心喷嘴气涡固有声学频率,通过renormalization group(RNG)k-ε湍流模型和volume of fluid(VOF)气液两相流模型进行数值仿真研究。仿真结果表明将离心喷嘴与喷嘴出口锥形液膜视为一个声学系统可准确预测固有声学频率,修正后离心喷嘴固有声学频率计算公式可准确计算气涡中不同气体介质的1、2阶声学频率,误差在3%以内。室压扰动频率等于离心喷嘴固有声学频率时两者发生耦合共振,气涡压力脉动振幅增加量约为室压扰动幅值的16倍,气涡声学压力脉动可能传入上游供应系统,引起喷注不稳定。展开更多
针对装甲车辆柴油机喷油器故障诊断不能满足实时在线监测的问题,提出一种基于多层双向长短时记忆网络(bidirectional long short term memory,Bi-LSTM)的装甲车辆柴油机喷油器故障诊断方法。对柴油机喷油器故障进行模拟实验,利用多层双...针对装甲车辆柴油机喷油器故障诊断不能满足实时在线监测的问题,提出一种基于多层双向长短时记忆网络(bidirectional long short term memory,Bi-LSTM)的装甲车辆柴油机喷油器故障诊断方法。对柴油机喷油器故障进行模拟实验,利用多层双向长短时记忆网络具备较长距离的时序分析能力的优势,分别将压力波特征值和压力波时序信号作为输入进行故障模式识别验证。结果表明:该方法具有较高的识别精度和较快的分类速度,能够满足实时在线监测的要求。展开更多
It is known that increasing the injection pressure reduces the breakup length and the droplet size.Adding pulses,on the other hand,helps to atomize the liquid into finer droplets,similar to airassisted injectors but w...It is known that increasing the injection pressure reduces the breakup length and the droplet size.Adding pulses,on the other hand,helps to atomize the liquid into finer droplets,similar to airassisted injectors but without altering the airtofuel concentration.To further reduce the droplet size and breakup length,a novel injector type,called''Pulsed PressureSwirl"(PPS),is introduced in this work,which is a combination of pressureswirl and ultrasonic pulsed injectors.A pressureswirl atomizer was designed and fabricated specifically for Mazut HFO(Heavy Fuel Oil).The droplet formation process and droplet size distribution have been studied experimentally(by shadowgraphy high speed imaging)and numerically(with the opensource VolumeofFluid code Gerris).Changing liquid injection pressure effect on the spray angle and film thickness has been quantified.These simulations have been used to study the primary breakup process and quantify the droplet size distributions,using different injection pulse frequencies and pressures.The numerical results have revealed that the new injector concept successfully produces finer droplets and results in a decrease in the breakup length,especially when applying high pulse frequencies,with no significant changes in the spray angle.展开更多
Abrasive suspension flow machining(ASFM)is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components.This study examines the e...Abrasive suspension flow machining(ASFM)is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components.This study examines the effect of back pressure on the grinding characteristics of an abrasive suspension flow during the grinding of slender holes.A numerical model was developed to simulate the abrasive suspension flow in a slender hole and was verified experimentally using injector nozzle grinding equipment under different grinding pressures and back pressures.It is shown that the ASFM with back pressure not only eliminates the cavitation flow in the spray hole,but also increases the number of effective abrasive particles and the flow coefficient.Increasing the back pressure during the grinding process can increase the Reynolds number of the abrasive suspension flow and reduce the thickness of the boundary layer in the slender hole.Moreover,increasing the back pressure can improve the flow rate of the injector nozzle and its grinding performance.展开更多
Understanding the hydraulic and frictional sensitivity of fault to different injection conditions is one of the efficient ways to provide useful implications for fault reactivation potential.Numerical simulations of f...Understanding the hydraulic and frictional sensitivity of fault to different injection conditions is one of the efficient ways to provide useful implications for fault reactivation potential.Numerical simulations of fractured reservoir have provided information on how fault behaviour varies under changing hydromechanical properties and injection conditions.A coupled hydro-mechanical model which can represent the elastoplastic behaviour of a fault was employed to predict and quantify the effects of varying injection positions and injection rates on permeability response and potential of fault reactivation under isothermal injection.We examine the sensitivity of seismic event magnitude and timing to variations in both pressure perturbation and stress as injection location changes.We generate results for two scenarios:one with changing injection position but with uniform injection rate,and another scenario with increasing injection rate at the same injection position.We observed that the potential of fault reactivation is affected by the hydraulic diffusivity potential of the fluid pressure,and this mechanism is mediated by a function of the injector position and injection rate.As the velocity of fluid transmission increases,increasing fluid pressure impact pore pressure elevation and reduced effective stress.However,an injector position where there is low diffusivity causes low pore pressure build-up rate,incapable of inducing shear failure,and thus,permeability enhancement is retarded in this case.Accordingly,the injection rate variation influences the rate of pore pressure build-up,the timing and magnitude of induced seismic events.This is also reflected in the permeability evolution as a response to the variations in the magnitude of fault openings and cracks.This changing injection conditions however influences the timing required to reach the critical peak friction point as pore pressure build-up rate and sensitivity to loading response change.Hence,with changing position and rate of injection,the evolution of展开更多
Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low po...Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions.Gasoline direct injection(GDI)has been recognized as one of the most effective ways to improve fuel atomization.As a special direct injection method,the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure.This injection method has excellent application potential and advantages for high performance and lightweight engines.In this study,the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa.External macro characteristics of spray were obtained using high speed backlit imaging.Phase Doppler particle analyzer(PDPA)was utilized to study the microcosmic spray characteristics.The results show that under the flash boiling condition,the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards.The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width.The sauter mean diameter(SMD)of flash boiling condition can be reduced to 5μm compared to the level close to 10μm in the non-flash boiling condition.展开更多
文摘为得到准确的离心喷嘴气涡固有声学频率,通过renormalization group(RNG)k-ε湍流模型和volume of fluid(VOF)气液两相流模型进行数值仿真研究。仿真结果表明将离心喷嘴与喷嘴出口锥形液膜视为一个声学系统可准确预测固有声学频率,修正后离心喷嘴固有声学频率计算公式可准确计算气涡中不同气体介质的1、2阶声学频率,误差在3%以内。室压扰动频率等于离心喷嘴固有声学频率时两者发生耦合共振,气涡压力脉动振幅增加量约为室压扰动幅值的16倍,气涡声学压力脉动可能传入上游供应系统,引起喷注不稳定。
文摘针对装甲车辆柴油机喷油器故障诊断不能满足实时在线监测的问题,提出一种基于多层双向长短时记忆网络(bidirectional long short term memory,Bi-LSTM)的装甲车辆柴油机喷油器故障诊断方法。对柴油机喷油器故障进行模拟实验,利用多层双向长短时记忆网络具备较长距离的时序分析能力的优势,分别将压力波特征值和压力波时序信号作为输入进行故障模式识别验证。结果表明:该方法具有较高的识别精度和较快的分类速度,能够满足实时在线监测的要求。
文摘It is known that increasing the injection pressure reduces the breakup length and the droplet size.Adding pulses,on the other hand,helps to atomize the liquid into finer droplets,similar to airassisted injectors but without altering the airtofuel concentration.To further reduce the droplet size and breakup length,a novel injector type,called''Pulsed PressureSwirl"(PPS),is introduced in this work,which is a combination of pressureswirl and ultrasonic pulsed injectors.A pressureswirl atomizer was designed and fabricated specifically for Mazut HFO(Heavy Fuel Oil).The droplet formation process and droplet size distribution have been studied experimentally(by shadowgraphy high speed imaging)and numerically(with the opensource VolumeofFluid code Gerris).Changing liquid injection pressure effect on the spray angle and film thickness has been quantified.These simulations have been used to study the primary breakup process and quantify the droplet size distributions,using different injection pulse frequencies and pressures.The numerical results have revealed that the new injector concept successfully produces finer droplets and results in a decrease in the breakup length,especially when applying high pulse frequencies,with no significant changes in the spray angle.
文摘Abrasive suspension flow machining(ASFM)is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components.This study examines the effect of back pressure on the grinding characteristics of an abrasive suspension flow during the grinding of slender holes.A numerical model was developed to simulate the abrasive suspension flow in a slender hole and was verified experimentally using injector nozzle grinding equipment under different grinding pressures and back pressures.It is shown that the ASFM with back pressure not only eliminates the cavitation flow in the spray hole,but also increases the number of effective abrasive particles and the flow coefficient.Increasing the back pressure during the grinding process can increase the Reynolds number of the abrasive suspension flow and reduce the thickness of the boundary layer in the slender hole.Moreover,increasing the back pressure can improve the flow rate of the injector nozzle and its grinding performance.
文摘Understanding the hydraulic and frictional sensitivity of fault to different injection conditions is one of the efficient ways to provide useful implications for fault reactivation potential.Numerical simulations of fractured reservoir have provided information on how fault behaviour varies under changing hydromechanical properties and injection conditions.A coupled hydro-mechanical model which can represent the elastoplastic behaviour of a fault was employed to predict and quantify the effects of varying injection positions and injection rates on permeability response and potential of fault reactivation under isothermal injection.We examine the sensitivity of seismic event magnitude and timing to variations in both pressure perturbation and stress as injection location changes.We generate results for two scenarios:one with changing injection position but with uniform injection rate,and another scenario with increasing injection rate at the same injection position.We observed that the potential of fault reactivation is affected by the hydraulic diffusivity potential of the fluid pressure,and this mechanism is mediated by a function of the injector position and injection rate.As the velocity of fluid transmission increases,increasing fluid pressure impact pore pressure elevation and reduced effective stress.However,an injector position where there is low diffusivity causes low pore pressure build-up rate,incapable of inducing shear failure,and thus,permeability enhancement is retarded in this case.Accordingly,the injection rate variation influences the rate of pore pressure build-up,the timing and magnitude of induced seismic events.This is also reflected in the permeability evolution as a response to the variations in the magnitude of fault openings and cracks.This changing injection conditions however influences the timing required to reach the critical peak friction point as pore pressure build-up rate and sensitivity to loading response change.Hence,with changing position and rate of injection,the evolution of
基金Supported by Beijing Institute of Technology Research Fund Program for Young Scholars(2019CX04-031)Foundation Research Funds of Ministry of Industry and Information Technology(JCKY2019602D018)。
文摘Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions.Gasoline direct injection(GDI)has been recognized as one of the most effective ways to improve fuel atomization.As a special direct injection method,the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure.This injection method has excellent application potential and advantages for high performance and lightweight engines.In this study,the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa.External macro characteristics of spray were obtained using high speed backlit imaging.Phase Doppler particle analyzer(PDPA)was utilized to study the microcosmic spray characteristics.The results show that under the flash boiling condition,the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards.The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width.The sauter mean diameter(SMD)of flash boiling condition can be reduced to 5μm compared to the level close to 10μm in the non-flash boiling condition.
