In order to estimate the trafficability of off-road vehicles, the linear relationships between the pressure and the stiffness of the tire and the action of the vertical tire force with the viscoelasticity are analyzed...In order to estimate the trafficability of off-road vehicles, the linear relationships between the pressure and the stiffness of the tire and the action of the vertical tire force with the viscoelasticity are analyzed. The method to improve the precision of the model by the coefficients is presented. The constitutive equation of the three-parameter linear model and the stiffness matrix of four-node isoparametric elements are derived to construct the FEM （finite element method） tire model in plan stress. A demarcation and verification system is designed based on the six-dimensional wheel force transducer and the vertical tire force is measured under different velocities. The results show that the model and the method proposed are reasonable.展开更多
To improve the semi-empirical model, the slip sinkage effect is analyzed based on the real vehicle test. A dynamic testing system is used to gain the dynamic responses of wheel-soil interactions, The Gauss-Newton algo...To improve the semi-empirical model, the slip sinkage effect is analyzed based on the real vehicle test. A dynamic testing system is used to gain the dynamic responses of wheel-soil interactions, The Gauss-Newton algorithm is adopted to estimate the undetermined parameters involved in the slip sinkage models. Wong＇s original model is compared with three typical slip sinkage models on the prediction performance of a drawbar pull. The maximum error rate, root mean squared error and correlation coefficient are utilized to evaluate the performance. The results indicate that the slip sinkage models outperform Wong＇s model and greatly improve the prediction accuracy. Lyasko＇s model is confirmed as an outstanding one for its comprehensive performance. Hence, the existence of the slip sinkage effect is validated. Lyasko＇s model is selected as an optimal one for the practical evaluation of military vehicle trafficability.展开更多
A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulat...A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.展开更多
Governing valve is the necessary passage through which steam enters into the steam turbine. The instability of the gas flow inside valve is the main reason that can induce the valve vibration, especially the valve rod...Governing valve is the necessary passage through which steam enters into the steam turbine. The instability of the gas flow inside valve is the main reason that can induce the valve vibration, especially the valve rod vibration. In order to reduce the vibration and improve the performance of the governing valve such as the security and economy of the steam turbine, we try to find the method by experimental investigation. As to commonly used governing valve such as ball governing valve in this paper, a number of micro pressure sensors that have high frequencies and nice dynamic capability are employed successfully. The micro sensors are inserted directly in key positions of the valve, such as positions of valve seat throat, valve disc top and so on. The collection and measurement of many different working conditions are carried out and the conclusion of the valve instability is obtained. Therefore, vibration induced by fluid flow is controlled and reduced by means of regulating operation conditions and valve structure. Meanwhile, by numerical simulation of ball governing valve, valve disc adhered flow and asymmetric collision force are considered as main factor to cause oscillation under the condition of small lift as well as small and middle pressure ratio.展开更多
文摘In order to estimate the trafficability of off-road vehicles, the linear relationships between the pressure and the stiffness of the tire and the action of the vertical tire force with the viscoelasticity are analyzed. The method to improve the precision of the model by the coefficients is presented. The constitutive equation of the three-parameter linear model and the stiffness matrix of four-node isoparametric elements are derived to construct the FEM （finite element method） tire model in plan stress. A demarcation and verification system is designed based on the six-dimensional wheel force transducer and the vertical tire force is measured under different velocities. The results show that the model and the method proposed are reasonable.
基金The National Natural Science Foundation of China(No.51305078)the Science and Technology Plan of Suzhou City(No.SYG201303)
文摘To improve the semi-empirical model, the slip sinkage effect is analyzed based on the real vehicle test. A dynamic testing system is used to gain the dynamic responses of wheel-soil interactions, The Gauss-Newton algorithm is adopted to estimate the undetermined parameters involved in the slip sinkage models. Wong＇s original model is compared with three typical slip sinkage models on the prediction performance of a drawbar pull. The maximum error rate, root mean squared error and correlation coefficient are utilized to evaluate the performance. The results indicate that the slip sinkage models outperform Wong＇s model and greatly improve the prediction accuracy. Lyasko＇s model is confirmed as an outstanding one for its comprehensive performance. Hence, the existence of the slip sinkage effect is validated. Lyasko＇s model is selected as an optimal one for the practical evaluation of military vehicle trafficability.
基金The National Natural Science Foundation of China(No.62173122)the Hebei Key Project of Natural Science Foundation(No.F2021201031)。
文摘A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.
文摘Governing valve is the necessary passage through which steam enters into the steam turbine. The instability of the gas flow inside valve is the main reason that can induce the valve vibration, especially the valve rod vibration. In order to reduce the vibration and improve the performance of the governing valve such as the security and economy of the steam turbine, we try to find the method by experimental investigation. As to commonly used governing valve such as ball governing valve in this paper, a number of micro pressure sensors that have high frequencies and nice dynamic capability are employed successfully. The micro sensors are inserted directly in key positions of the valve, such as positions of valve seat throat, valve disc top and so on. The collection and measurement of many different working conditions are carried out and the conclusion of the valve instability is obtained. Therefore, vibration induced by fluid flow is controlled and reduced by means of regulating operation conditions and valve structure. Meanwhile, by numerical simulation of ball governing valve, valve disc adhered flow and asymmetric collision force are considered as main factor to cause oscillation under the condition of small lift as well as small and middle pressure ratio.
