Cloud Technology is a new platform that offers on-demand computing Peripheral such as storage,processing power,and other computer system resources.It is also referred to as a system that will let the consumers utilize...Cloud Technology is a new platform that offers on-demand computing Peripheral such as storage,processing power,and other computer system resources.It is also referred to as a system that will let the consumers utilize computational resources like databases,servers,storage,and intelligence over the Internet.In a cloud network,load balancing is the process of dividing network traffic among a cluster of available servers to increase efficiency.It is also known as a server pool or server farm.When a single node is overwhelmed,balancing the workload is needed to manage unpredictable workflows.The load balancer sends the load to another free node in this case.We focus on the Balancing of workflows with the proposed approach,and we present a novel method to balance the load that manages the dynamic scheduling process.One of the preexisting load balancing techniques is considered,however it is somewhat modified to fit the scenario at hand.Depending on the experimentation’s findings,it is concluded that this suggested approach improves load balancing consistency,response time,and throughput by 6%.展开更多
Based on the solution of the governing differential equation for deformation of throttle slice while satisfying required boundary conditions, the coefficient （Gr） and an analytical formula for computing the deformat...Based on the solution of the governing differential equation for deformation of throttle slice while satisfying required boundary conditions, the coefficient （Gr） and an analytical formula for computing the deformation of throttle slice is presented through equivalency transformation, which is a concise, accurate and practical method for throttle slice design and characteristic analysis. Researched the deformation at any radius, compared with ANSYS FEA software by the simulation analysis, the availability opening size of throttle that was defined by the deformation at the valve mouth radius is studied. The affection of valve mouth radius to the damper characteristic is analyzed. Tests are made for the damper characteristic, compared with simulation results, it is shown that Gr method is an accurate computation method for computing the deformation of throttle slice at valve mouth radius, suitihle to use in the damper design, analysis, and verification. The deformation at mouth radius could not be replaced with the outside radius.展开更多
This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock, and a valve positioned at ...This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock, and a valve positioned at the downstream end of the penstock. Analytical formulas of maximum water hammer pressures at the downstream end of the tunnel and the valve were derived for a system subjected to linear and slow valve closure. The analytical results were then compared with numerical ones obtained using the method of characteristics. There is agreement between them. The formulas can be applied to estimating water hammer pressure at the valve and transmission of water hammer pressure through the surge chamber at the junction for a hydraulic pipe system with a surge chamber.展开更多
Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of ...Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.展开更多
In modern vehicles, electronic throttle(ET) has been widely utilized to control the airflow into gasoline engine. To solve the control difficulties with an ET, such as strong nonlinearity,unknown model parameters and ...In modern vehicles, electronic throttle(ET) has been widely utilized to control the airflow into gasoline engine. To solve the control difficulties with an ET, such as strong nonlinearity,unknown model parameters and input saturation constraints,an adaptive sliding-mode tracking control strategy for an ET is presented. Compared with the existing control strategies for an ET, input saturation constraints and parameter uncertainties are adequately considered in the proposed control strategy. At first, the nonlinear dynamic model for control of an ET is described. According to the dynamical model, the nonlinear adaptive sliding-mode tracking control method is presented,where parameter adaptive laws and auxiliary design system are employed. Parameter adaptive law is given to estimate the unknown parameter with an ET. An auxiliary system is designed,and its state is utilized in the tracking control method to handle the input saturation. Stability proof and analysis of the adaptive sliding-mode control method is performed by using Lyapunov stability theory. Finally, the reliability and feasibility of the proposed control strategy are evaluated by computer simulation.Simulation research shows that the proposed sliding-mode control strategy can provide good control performance for an ET.展开更多
In order to effectively implement DPF(Diesel Particulate Filters)regeneration control,thermal management of exhaust products before and inside Diesel Oxidation Catalyst(DOC)is necessary.In the present study,the Influe...In order to effectively implement DPF(Diesel Particulate Filters)regeneration control,thermal management of exhaust products before and inside Diesel Oxidation Catalyst(DOC)is necessary.In the present study,the Influence of the intake throttle valve and late post injection process on temperature rise inside DOC is analyzed through engine bench tests.The steady experiment results show that adjustment of the intake throttle valve can effectively increase exhaust temperature before DOC;in particular,with intake throttle valve opening at 20%,temperature before DOC can be increased by about 170℃ with respect to the full opening.An increase in the late post injection quantity can produce a significant rise of the temperature inside DOC,however its impact on the exhaust temperature before DOC is relatively limited.As the late post injection quantity increases,Hydrocarbon(HC)emissions also grow;in the present work it is shown that with a proper injection quantity,a considerable temperature increase inside the DOC can be obtained with relatively low HC emission.More specifically,with the intake throttle valve at 30%and DOC reaching ignition temperature as the late post injection quantity is increased,the exhaust temperature after DOC can be made larger than 550℃,adequate for DPF active regeneration.展开更多
Experimental investigations are made on the effects of operating conditionson the flow characteristics of throttle when tap water is used as the working media. The researchedthrottles include cone poppet valve, ball v...Experimental investigations are made on the effects of operating conditionson the flow characteristics of throttle when tap water is used as the working media. The researchedthrottles include cone poppet valve, ball valve, disc valve and dumping orifice. Operating conditionincludes poppet lift, working media, back pressure, medium temperature, etc. Because the vapourouspressure of water is much higher than that of oil, cavitation is easier to occur in water hydraulicelements and systems, so the effects of operating conditions on the cavitation characteristics ofthrottle are also researched.展开更多
Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems res...Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.展开更多
Combining with the development of automated manual transmission （AMT）, the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift an...Combining with the development of automated manual transmission （AMT）, the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift and so on. Based on simulation, the responding throttle control strategies are proposed, and a simple but effective throttle control method is presented. The testing results have proved that the strategies are effective for improving the pedal tracking precision and the qualities of start and shift.展开更多
Seven adjustments of convergent-type Vortex Tube （VT） with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow...Seven adjustments of convergent-type Vortex Tube （VT） with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow structures inside the VTs. An experimental setup was designed, and tests were performed on different convergent VT configurations at injection pressures ranging from 0.45 to 0.65 MPa. The angles of the throttle valve were arranged between 30° to 90°, and the numbers of injection nozzles ranged between 2 and 6. Laboratory results indicated that the maximum hot and cold temperature drops ranged from 23.24 to 35 K and from 22.87 to 32.88 K, respectively, at four injection nozzles. Results also showed that temperature drop is a function of hot throttle valve angle with the maximum hot and cold temperature drops depending on the angle applied. We used graphs to demonstrate the changes in the cold and hot temperature drops with respect to hot throttle angle values. These values were interpreted and evaluated to determine the optimum angle, which was 60°. The CFD outputs agreed very well with the laboratory results. The proposed CFD results can help future researchers gain good insights into the complicated separation process taking place inside the VTs.展开更多
In allusion to easy invalidation of damping valve in vehicle shock absorber caused by the impact from the road surface, the importance of the study of damping valve water hammer pressure is presented. The physical mod...In allusion to easy invalidation of damping valve in vehicle shock absorber caused by the impact from the road surface, the importance of the study of damping valve water hammer pressure is presented. The physical model of damping valve with the circle throttle slice is established. The time for the throttle slice deformation is studied by using the finite software, and the laws that how the structure parameters affect the deformation time are obtained. Combining the theory of water hammer, the water hammer initial and boundary condition of the damping valve is deduced, and the water hammer model of throttle slice is established. The analysis of simulation results indicates that the water hammer pressure amplitude and the amount of water hammer oscillation period can be reduced and the dependability of the valve can be enhanced by modifying the structure parameters and aperture width between slice and valve body.展开更多
Based on the fact that the electronic throttle angle effect performs well in the traditional car following model,this paper attempts to introduce the electronic throttle angle into the smart driver model(SDM)as an acc...Based on the fact that the electronic throttle angle effect performs well in the traditional car following model,this paper attempts to introduce the electronic throttle angle into the smart driver model(SDM)as an acceleration feedback control term,and establish an extended smart driver model considering electronic throttle angle changes with memory(ETSDM).In order to show the practicability of the extended model,the next generation simulation(NGSIM)data was used to calibrate and evaluate the extended model and the smart driver model.The calibration results show that,compared with SDM,the simulation value based on the ETSDM is better fitted with the measured data,that is,the extended model can describe the actual traffic situation more accurately.Then,the linear stability analysis of ETSDM was carried out theoretically,and the stability condition was derived.In addition,numerical simulations were explored to show the influence of the electronic throttle angle changes with memory and the driver sensitivity on the stability of traffic flow.The numerical results show that the feedback control term of electronic throttle angle changes with memory can enhance the stability of traffic flow,which shows the feasibility and superiority of the proposed model to a certain extent.展开更多
In light of the light emission from cavitation bubbles under certain conditions, the phenomena of the cavitation bubble luminescence in the hydraulic cone-type throttle valve is focused in this paper. Firstly,the soft...In light of the light emission from cavitation bubbles under certain conditions, the phenomena of the cavitation bubble luminescence in the hydraulic cone-type throttle valve is focused in this paper. Firstly,the software of automatic dynamic incremental nonlinear analysis( ADINA) is applied to studying the flow field of the flow channel of the cone-type throttle valve. And the pressure distribution of the valve flow channel is obtained. The easyhappening area of cavitation in the cone-type throttle valve is also found out by ADINA. Then,the experimental research on the conetype throttle valve is carried out in this paper. The changing law of the hydraulic oil temperature in the corresponding region under different system pressure and the backpressure condition are experimentally researched. The relationship between the luminescence intensity and the cavitation intensity,the pressure,and the temperature are also studied. Finally,a summary of the causal relationship between the luminescence and cavitation in the cone-type throttle valve,the cavitation effect on the hydraulic oil temperature,and the method for the inhibition of cavitation bubble luminescence are presented. The results show that the light intensity increases with the increase of the cavitation intensity,and the luminescence can be inhibited by the increase of backpressure.展开更多
The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve p...The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve port,which can improve the two-step throttle characteristics of the valve port,reduce the cavitation phenomenon of the valve port,and increase the output accuracy of the hydraulic servo joint.Firstly,the internal flow field of the rotary valve is simulated by using the sliding grid technology of FLUENT software,and the changing rule of the throttle position in the working process of the structure is analyzed.Secondly,compared with the simulation results of rotary valve with single-rotation valve port,it is shown that the two-step throttle characteristics of the structure are less affected by the change of the opening of the rotary valve,and the cavitation index of the joint valve port is reduced.Finally,the influence of the rotation speed of the valve core,oil supply pressure and key dimension of valve core on throttle characteristics of rotary valve have been analyzed.展开更多
Back-stepping control (BSC), which is deemed effective for a non-holonomic system, is applied to improving both responsiveness and resolution performance of an electronic control throttle (ECT) used in automotive engi...Back-stepping control (BSC), which is deemed effective for a non-holonomic system, is applied to improving both responsiveness and resolution performance of an electronic control throttle (ECT) used in automotive engines. This paper is characterized by the use of a two-step type BSC in a manner that achieves an improvement in responsiveness with the ETC operated in a fully opened state by adding a derivative term in Step 1 and the improvement in resolution performance with the ETC operated in a minutely opened state by adding an adaptive feature in the form of an integral term using the control deviation in Step 2. This paper presents an ECT control expressed as a second-order system including nonlinearities such as backlash of gear train and static friction in sliding area, a BSC system designed based on Lyapunov stability, and a determination method for control parameters. Also, a two-step type BSC system is formulated using Matlab/Simulink with a physics model as a control object. As a result of simulation analyses, it becomes clear that the BSC system can achieve quicker response because the derivative term works effectively and finer resolution because the adaptive control absorbs the error margin of the nonlinear compensation than conventional PID control.展开更多
The steady-state flow field characteristics have important effects on the stability of the throttled surge tank with the standpipe. This paper analyzes these effects on the basis of the numerical simulation of the flo...The steady-state flow field characteristics have important effects on the stability of the throttled surge tank with the standpipe. This paper analyzes these effects on the basis of the numerical simulation of the flow field by using the Computational Fluid Dynamics （CFD） method. It is shown that the anticlockwise recirculation zone is formed in the standpipe, which affects the local head loss at the junction of the standpipe with the pipeline. The variation of the head loss coefficient at the junction is linearly related with the diameter ratio of the standpipe to the pipeline. The dimensionless recirculation flow rate is proportional to the square of the diameter ratio. Considering the effects of the recirculation zone, an empirical expression of the critical stability area is obtained. Comparing with the Thoma critical area, the area obtained by the present method is smaller, and the reduction depends on the diameter ratio and the ratio of the velocity head to the head losses in the tunnel. words：展开更多
For vehicle adaptive cruise control （ACC） systems, the switching performance between throttle and brake determines the driving comfort, fuel consumption and service lives of vehicle mechanical components. In this pa...For vehicle adaptive cruise control （ACC） systems, the switching performance between throttle and brake determines the driving comfort, fuel consumption and service lives of vehicle mechanical components. In this paper, an ACC algorithm with the optimal switching control between throttle and brake is designed in model predictive control （MPC） framework. By introducing the binary integer variables, the dynamics of throttle and brake are integrated in one model expression for the controller design. Then the ACC algorithm is designed to satisfy not only safe car following, but also the optimal switching between throttle and brake, which leads to an online mixed integer quadratic programming solved by the nested two-loop method. The simulation results show that the proposed ACC algorithm meets the requirements of safe car following, outperforms the traditional algorithms by performing smoother responses, reducing the switching times between throttle and brake, and therefore improves driving comfort and fuel efficiency significantly.展开更多
Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To ...Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To solve this problem,large-diameter multi-stage circumfluence nozzle was designed to release pressure stage by stage.In order to illuminate the throttle characteristics of the CO2 multi-stage circumfluence nozzles,numerical simulation was performed to test several nozzles with different diameters and stage numbers.Furthermore,we tested the throttle characteristics through laboratory experiments and obtained the effects of several critical parameters such as nozzle diameter,number of stage and pressure drop on the throttle characteristics.The results show that the flow rate decreases as the nozzle stage increases on the condition of constant pressure and nozzle diameter.And pressure difference increases as nozzle stage number increases under the constant flow rate.The throttle capability of multi-stage circumfluence nozzles was much better than the concentric nozzles.Large-diameter multi-stage nozzle is recommended rather than small-diameter single-stage nozzle during the process of separate-layer injection,which can efficiently prevent impurities and ice blocking.The results are expected to provide a theoretical support for the nozzle choice of separate-layer injection of CO2.展开更多
Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet ...Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet channel. The two modified models have identical geometrical spacing except for the number and location of the orifices in the upper plate of the throttle chamber added in the jet channel. Different pressure values were set at the outlets of different row film holes simulating the mainstream favorable pressure gradient. The ratios of inlet total pressures of impingement holes to outlet static pressures of the third row film holes ranged from 1.6 to 3.6. The Nusselt number distributions were validated by the experimental data. The main target of this study was to quantify the impact of the throttle chamber on the flow regulation and internal heat transfer characteristics. The flow factor, relative mass flow rate, the Nusselt number and the heat transfer factors on the target walls were presented. It is found that the mass flow rate distributions in the film hole rows become more reasonable by the modification of location and number of the orifices on the throttle chamber. The throttle chamber decreases the heat transfer on the target walls.展开更多
China’s largest train maker seeks to lower its high liability-asset ratio through a dual listing in Shanghai and Hong Kong china’s largest train maker debuted on Shanghai and Hong Kong stock exchanges in August-the ...China’s largest train maker seeks to lower its high liability-asset ratio through a dual listing in Shanghai and Hong Kong china’s largest train maker debuted on Shanghai and Hong Kong stock exchanges in August-the country’s first domestic initial public offering (IPO) in the second half of the year.展开更多
基金supported by the project:“Research and Implementation of Innovative Solutions for Monitoring Consumption in Technical Installations Using Artificial Intelligence”,beneficiary S.C.REMONI TECHNOLOGIES RO S.R.L in partnership with“Gheorghe Asachi”Technical University of Iasi,Financing Contract No.400/390076/26.11.2021,SMIS Code 121866,financed by POC/163/1/3.
文摘Cloud Technology is a new platform that offers on-demand computing Peripheral such as storage,processing power,and other computer system resources.It is also referred to as a system that will let the consumers utilize computational resources like databases,servers,storage,and intelligence over the Internet.In a cloud network,load balancing is the process of dividing network traffic among a cluster of available servers to increase efficiency.It is also known as a server pool or server farm.When a single node is overwhelmed,balancing the workload is needed to manage unpredictable workflows.The load balancer sends the load to another free node in this case.We focus on the Balancing of workflows with the proposed approach,and we present a novel method to balance the load that manages the dynamic scheduling process.One of the preexisting load balancing techniques is considered,however it is somewhat modified to fit the scenario at hand.Depending on the experimentation’s findings,it is concluded that this suggested approach improves load balancing consistency,response time,and throughput by 6%.
基金the Ministerial Level Foundation (5040001) the Nationality Excellence Doctor Thesis Foster & Encouragement Foundation of School of MechanicalVehicular Engineering,Beijing Institute of Technology(No 010003)
文摘Based on the solution of the governing differential equation for deformation of throttle slice while satisfying required boundary conditions, the coefficient （Gr） and an analytical formula for computing the deformation of throttle slice is presented through equivalency transformation, which is a concise, accurate and practical method for throttle slice design and characteristic analysis. Researched the deformation at any radius, compared with ANSYS FEA software by the simulation analysis, the availability opening size of throttle that was defined by the deformation at the valve mouth radius is studied. The affection of valve mouth radius to the damper characteristic is analyzed. Tests are made for the damper characteristic, compared with simulation results, it is shown that Gr method is an accurate computation method for computing the deformation of throttle slice at valve mouth radius, suitihle to use in the damper design, analysis, and verification. The deformation at mouth radius could not be replaced with the outside radius.
基金supported by the National Natural Science Foundation of China (Grant No.50539070)the Major State Basic Research Development Program of China (Grant No.2006CB403304)
文摘This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock, and a valve positioned at the downstream end of the penstock. Analytical formulas of maximum water hammer pressures at the downstream end of the tunnel and the valve were derived for a system subjected to linear and slow valve closure. The analytical results were then compared with numerical ones obtained using the method of characteristics. There is agreement between them. The formulas can be applied to estimating water hammer pressure at the valve and transmission of water hammer pressure through the surge chamber at the junction for a hydraulic pipe system with a surge chamber.
基金Supported by the China Postdoctoral Science Foundation(2014M552195)the State Key Laboratory Foundation of Subtropical Building,South China University of Technology(2013ZC13)the Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization,South China University of Technology(2013A061401005)
文摘Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.
基金partially supported by the National Natural Science Foundation of China(61773189)Natural Science Fundamental of Liaoning Province(20170540443)the Program for Liaoning Innovative Research Team in University(LT2016006)
文摘In modern vehicles, electronic throttle(ET) has been widely utilized to control the airflow into gasoline engine. To solve the control difficulties with an ET, such as strong nonlinearity,unknown model parameters and input saturation constraints,an adaptive sliding-mode tracking control strategy for an ET is presented. Compared with the existing control strategies for an ET, input saturation constraints and parameter uncertainties are adequately considered in the proposed control strategy. At first, the nonlinear dynamic model for control of an ET is described. According to the dynamical model, the nonlinear adaptive sliding-mode tracking control method is presented,where parameter adaptive laws and auxiliary design system are employed. Parameter adaptive law is given to estimate the unknown parameter with an ET. An auxiliary system is designed,and its state is utilized in the tracking control method to handle the input saturation. Stability proof and analysis of the adaptive sliding-mode control method is performed by using Lyapunov stability theory. Finally, the reliability and feasibility of the proposed control strategy are evaluated by computer simulation.Simulation research shows that the proposed sliding-mode control strategy can provide good control performance for an ET.
基金supported by the Ministry of Science and Technology of the People’s Republic of China[grant numbers 2017YFC0211304]the Natural Science Foundation of Shandong Province[grant number ZR2019MEE041]the Open Fund of the National Engineering Laboratory for Mobile Source Emission Control Technology[grant number NELMS2017A14].
文摘In order to effectively implement DPF(Diesel Particulate Filters)regeneration control,thermal management of exhaust products before and inside Diesel Oxidation Catalyst(DOC)is necessary.In the present study,the Influence of the intake throttle valve and late post injection process on temperature rise inside DOC is analyzed through engine bench tests.The steady experiment results show that adjustment of the intake throttle valve can effectively increase exhaust temperature before DOC;in particular,with intake throttle valve opening at 20%,temperature before DOC can be increased by about 170℃ with respect to the full opening.An increase in the late post injection quantity can produce a significant rise of the temperature inside DOC,however its impact on the exhaust temperature before DOC is relatively limited.As the late post injection quantity increases,Hydrocarbon(HC)emissions also grow;in the present work it is shown that with a proper injection quantity,a considerable temperature increase inside the DOC can be obtained with relatively low HC emission.More specifically,with the intake throttle valve at 30%and DOC reaching ignition temperature as the late post injection quantity is increased,the exhaust temperature after DOC can be made larger than 550℃,adequate for DPF active regeneration.
基金This project is supported by National Natural Science Foundation of China (No.50375056, 59975031).
文摘Experimental investigations are made on the effects of operating conditionson the flow characteristics of throttle when tap water is used as the working media. The researchedthrottles include cone poppet valve, ball valve, disc valve and dumping orifice. Operating conditionincludes poppet lift, working media, back pressure, medium temperature, etc. Because the vapourouspressure of water is much higher than that of oil, cavitation is easier to occur in water hydraulicelements and systems, so the effects of operating conditions on the cavitation characteristics ofthrottle are also researched.
文摘Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.
基金This project is supported by Provincial Open Foundation of Key Lab forAutomobile of Jiangsu, China (No.KJS02076) and 985 Project of AutomotiveEngineering Innovation Platform of Jilin University, China.
文摘Combining with the development of automated manual transmission （AMT）, the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift and so on. Based on simulation, the responding throttle control strategies are proposed, and a simple but effective throttle control method is presented. The testing results have proved that the strategies are effective for improving the pedal tracking precision and the qualities of start and shift.
文摘Seven adjustments of convergent-type Vortex Tube （VT） with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow structures inside the VTs. An experimental setup was designed, and tests were performed on different convergent VT configurations at injection pressures ranging from 0.45 to 0.65 MPa. The angles of the throttle valve were arranged between 30° to 90°, and the numbers of injection nozzles ranged between 2 and 6. Laboratory results indicated that the maximum hot and cold temperature drops ranged from 23.24 to 35 K and from 22.87 to 32.88 K, respectively, at four injection nozzles. Results also showed that temperature drop is a function of hot throttle valve angle with the maximum hot and cold temperature drops depending on the angle applied. We used graphs to demonstrate the changes in the cold and hot temperature drops with respect to hot throttle angle values. These values were interpreted and evaluated to determine the optimum angle, which was 60°. The CFD outputs agreed very well with the laboratory results. The proposed CFD results can help future researchers gain good insights into the complicated separation process taking place inside the VTs.
基金Sponsored by the Ministerial Level Advanced Research Foundation (623010202 4)
文摘In allusion to easy invalidation of damping valve in vehicle shock absorber caused by the impact from the road surface, the importance of the study of damping valve water hammer pressure is presented. The physical model of damping valve with the circle throttle slice is established. The time for the throttle slice deformation is studied by using the finite software, and the laws that how the structure parameters affect the deformation time are obtained. Combining the theory of water hammer, the water hammer initial and boundary condition of the damping valve is deduced, and the water hammer model of throttle slice is established. The analysis of simulation results indicates that the water hammer pressure amplitude and the amount of water hammer oscillation period can be reduced and the dependability of the valve can be enhanced by modifying the structure parameters and aperture width between slice and valve body.
基金the Natural Science Foundation of Zhejiang Province,China(Grant No.LY20G010004)the the Program of Humanities and Social Science of Education Ministry of China(Grant No.20YJA630008)the K.C.Wong Magna Fund in Ningbo University,China.
文摘Based on the fact that the electronic throttle angle effect performs well in the traditional car following model,this paper attempts to introduce the electronic throttle angle into the smart driver model(SDM)as an acceleration feedback control term,and establish an extended smart driver model considering electronic throttle angle changes with memory(ETSDM).In order to show the practicability of the extended model,the next generation simulation(NGSIM)data was used to calibrate and evaluate the extended model and the smart driver model.The calibration results show that,compared with SDM,the simulation value based on the ETSDM is better fitted with the measured data,that is,the extended model can describe the actual traffic situation more accurately.Then,the linear stability analysis of ETSDM was carried out theoretically,and the stability condition was derived.In addition,numerical simulations were explored to show the influence of the electronic throttle angle changes with memory and the driver sensitivity on the stability of traffic flow.The numerical results show that the feedback control term of electronic throttle angle changes with memory can enhance the stability of traffic flow,which shows the feasibility and superiority of the proposed model to a certain extent.
基金National Natural Science Foundation of China(No.51275123)
文摘In light of the light emission from cavitation bubbles under certain conditions, the phenomena of the cavitation bubble luminescence in the hydraulic cone-type throttle valve is focused in this paper. Firstly,the software of automatic dynamic incremental nonlinear analysis( ADINA) is applied to studying the flow field of the flow channel of the cone-type throttle valve. And the pressure distribution of the valve flow channel is obtained. The easyhappening area of cavitation in the cone-type throttle valve is also found out by ADINA. Then,the experimental research on the conetype throttle valve is carried out in this paper. The changing law of the hydraulic oil temperature in the corresponding region under different system pressure and the backpressure condition are experimentally researched. The relationship between the luminescence intensity and the cavitation intensity,the pressure,and the temperature are also studied. Finally,a summary of the causal relationship between the luminescence and cavitation in the cone-type throttle valve,the cavitation effect on the hydraulic oil temperature,and the method for the inhibition of cavitation bubble luminescence are presented. The results show that the light intensity increases with the increase of the cavitation intensity,and the luminescence can be inhibited by the increase of backpressure.
基金Supported by the National Natural Science Foundation of China(No.61105086)Hubei Province Natural Science Foundation(No.2018CFB626)+1 种基金Wuhan Application Foundation Frontier Project(No.2019010701011404)Institute of Robotics and Intelligent Systems Foundation(No.F201803)。
文摘The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve port,which can improve the two-step throttle characteristics of the valve port,reduce the cavitation phenomenon of the valve port,and increase the output accuracy of the hydraulic servo joint.Firstly,the internal flow field of the rotary valve is simulated by using the sliding grid technology of FLUENT software,and the changing rule of the throttle position in the working process of the structure is analyzed.Secondly,compared with the simulation results of rotary valve with single-rotation valve port,it is shown that the two-step throttle characteristics of the structure are less affected by the change of the opening of the rotary valve,and the cavitation index of the joint valve port is reduced.Finally,the influence of the rotation speed of the valve core,oil supply pressure and key dimension of valve core on throttle characteristics of rotary valve have been analyzed.
文摘Back-stepping control (BSC), which is deemed effective for a non-holonomic system, is applied to improving both responsiveness and resolution performance of an electronic control throttle (ECT) used in automotive engines. This paper is characterized by the use of a two-step type BSC in a manner that achieves an improvement in responsiveness with the ETC operated in a fully opened state by adding a derivative term in Step 1 and the improvement in resolution performance with the ETC operated in a minutely opened state by adding an adaptive feature in the form of an integral term using the control deviation in Step 2. This paper presents an ECT control expressed as a second-order system including nonlinearities such as backlash of gear train and static friction in sliding area, a BSC system designed based on Lyapunov stability, and a determination method for control parameters. Also, a two-step type BSC system is formulated using Matlab/Simulink with a physics model as a control object. As a result of simulation analyses, it becomes clear that the BSC system can achieve quicker response because the derivative term works effectively and finer resolution because the adaptive control absorbs the error margin of the nonlinear compensation than conventional PID control.
基金supported by the National Natural Science Foundation of China(Grant No.51079050)the Doctoral Innovation Foundation in Jiangsu Province(Grant No.2017-B0803338)
文摘The steady-state flow field characteristics have important effects on the stability of the throttled surge tank with the standpipe. This paper analyzes these effects on the basis of the numerical simulation of the flow field by using the Computational Fluid Dynamics （CFD） method. It is shown that the anticlockwise recirculation zone is formed in the standpipe, which affects the local head loss at the junction of the standpipe with the pipeline. The variation of the head loss coefficient at the junction is linearly related with the diameter ratio of the standpipe to the pipeline. The dimensionless recirculation flow rate is proportional to the square of the diameter ratio. Considering the effects of the recirculation zone, an empirical expression of the critical stability area is obtained. Comparing with the Thoma critical area, the area obtained by the present method is smaller, and the reduction depends on the diameter ratio and the ratio of the velocity head to the head losses in the tunnel. words：
基金supported by Science & Technology Program of Shanghai Maritime University(No.20120077)
文摘For vehicle adaptive cruise control （ACC） systems, the switching performance between throttle and brake determines the driving comfort, fuel consumption and service lives of vehicle mechanical components. In this paper, an ACC algorithm with the optimal switching control between throttle and brake is designed in model predictive control （MPC） framework. By introducing the binary integer variables, the dynamics of throttle and brake are integrated in one model expression for the controller design. Then the ACC algorithm is designed to satisfy not only safe car following, but also the optimal switching between throttle and brake, which leads to an online mixed integer quadratic programming solved by the nested two-loop method. The simulation results show that the proposed ACC algorithm meets the requirements of safe car following, outperforms the traditional algorithms by performing smoother responses, reducing the switching times between throttle and brake, and therefore improves driving comfort and fuel efficiency significantly.
文摘Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To solve this problem,large-diameter multi-stage circumfluence nozzle was designed to release pressure stage by stage.In order to illuminate the throttle characteristics of the CO2 multi-stage circumfluence nozzles,numerical simulation was performed to test several nozzles with different diameters and stage numbers.Furthermore,we tested the throttle characteristics through laboratory experiments and obtained the effects of several critical parameters such as nozzle diameter,number of stage and pressure drop on the throttle characteristics.The results show that the flow rate decreases as the nozzle stage increases on the condition of constant pressure and nozzle diameter.And pressure difference increases as nozzle stage number increases under the constant flow rate.The throttle capability of multi-stage circumfluence nozzles was much better than the concentric nozzles.Large-diameter multi-stage nozzle is recommended rather than small-diameter single-stage nozzle during the process of separate-layer injection,which can efficiently prevent impurities and ice blocking.The results are expected to provide a theoretical support for the nozzle choice of separate-layer injection of CO2.
基金supported by the National Natural Science Foundation of China(Grant No.51406124)by the Educational Department of Liaoning Province(Grant No.JYT19062)。
文摘Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet channel. The two modified models have identical geometrical spacing except for the number and location of the orifices in the upper plate of the throttle chamber added in the jet channel. Different pressure values were set at the outlets of different row film holes simulating the mainstream favorable pressure gradient. The ratios of inlet total pressures of impingement holes to outlet static pressures of the third row film holes ranged from 1.6 to 3.6. The Nusselt number distributions were validated by the experimental data. The main target of this study was to quantify the impact of the throttle chamber on the flow regulation and internal heat transfer characteristics. The flow factor, relative mass flow rate, the Nusselt number and the heat transfer factors on the target walls were presented. It is found that the mass flow rate distributions in the film hole rows become more reasonable by the modification of location and number of the orifices on the throttle chamber. The throttle chamber decreases the heat transfer on the target walls.
文摘China’s largest train maker seeks to lower its high liability-asset ratio through a dual listing in Shanghai and Hong Kong china’s largest train maker debuted on Shanghai and Hong Kong stock exchanges in August-the country’s first domestic initial public offering (IPO) in the second half of the year.
