Hydraulic motors have been widely used in large-scale machinery such as ground heavy equipment and heavy-duty vehicles, ships, and so on because of their high-power drive capability. However, the driving device is confronted with constraints related to its size and weight. Typically, the hydraulic axial piston motor is preferred for its simplicity and efficiency. However, the oil distributor in traditional hydraulic motors faces significant challenges, such as evident oil leakage and power loss from the mating surfaces of the fixed oil distributor and rotating cylinder block. To enhance the reliability and performance of hydraulic motors employed in paper driving applications, this paper introduces a digital radial hydraulic motor used for heavy-duty vehicle traction. The motor is powered by an on-board pump station from which several on/off valves can distribute the hydraulic oil. This design effectively mitigates the performance degradation issues associated with friction and wear in traditional hydraulic motor oil distributors. The drive characteristics of the motor can be flexibly adjusted through the combination of valves. Our investigation into the motor’s design principles and parameter analysis is poised to make an indirect yet significant contribution to the optimization of heavy-duty vehicle traction systems. This paper delineates the application conditions and operational principles of the digital hydraulic motor, thoroughly analyzes the intricate topological interrelationships of its parameters, and meticulously develops a detailed component-level model. Through comprehensive calculations, it reveals the impact of configuration and flow valve parameters on motor efficiency. A simulation model is established for the purpose of verification. Furthermore, the influence of the flow allocation method on efficiency and pressure pulsation is examined, leading to the proposal of a novel flow allocation strategy, the efficacy of which is substantiated through simulation. In conclusion, this paper formulates critical insights to inform the design and selection of components for digital hydraulic motors. These findings may provide a feasible solution for heavy-duty vehicle traction application scenarios.
By discussing the effect of spindle speed and feed rate to bit life,experiments of high speed drilling in small and deep hole on stainless steel were processed.Parameter range and optimization direction were determined by the experiment analysis.The conclusion could not only improve the machining efficiency and reduce the cost of high speed drilling in small and deep hole on stainless steel,but also provide reference for high speed drilling on other materials.
The quasi-periodic orbit about the translunar libration point can be used to establish a continuous communication link between the Earth and the far side of the Moon.In this paper,Sun-Earth-Moon autonomous navigation is implemented and investigated in the translunar libration point problem.Firstly,a new navigation dynamic model is proposed.Furthermore,due to the unstable nature of the translunar libration orbit,three sensor configuration cases for Sun-Earth-Moon autonomous navigation are studied.Simulation results of autonomous navigation are obtained by the iterative Least Squares Filtering.The nonlinear identifiability analysis is used to evaluate the identifiability and find an appropriate and robust sensor configuration for translunar libration probe.Finally,Simulations show that the sensor configuration of using directional data from the spacecraft to the Sun,the Earth and the Moon and one Doppler measurement can satisfy both the economical index and reliability.
In order to solve the problem of low accuracy of trajectory prediction for near space vehicles, this paper, firstly, establishes the dynamic model of the near space vehicles and simplifies the model according to the equilibrium glide characteristics, so as to obtain the prediction model. Then, the parameters of the simplified equilibrium glide prediction model can be identified by the least square method combined with the previous observation data. On this basis, to further eliminate the prediction error caused by the inadequate accuracy of the prediction model, the time-varying identification parameters approach is presented instead of the original fixed parameters by the small interval constant method. Finally, the comparison simulations illustrate the efficacy and advantage against the traditional ballistic prediction.
The 16th Asian Games will be held in Guangzhou in 2010.This paper introduces the basice planning background briefly,then it expound the planning task,aim and principle.Because different Asian Games colony have different traffic demand,against the difference,the article put forward roads building plans in three areas.It has give the better reference for other cities which would hold large games.
According to the pipe bursting problem of the high pressure pipeline occurred frequently,with the analysis on the relationship among the pump sources,leakage flow and system pressure,the steady state and transient state pressure variation model of the high pressure pipeline with the different leakage degrees was obtained.A set of pipe bursting simulation experiment system was designed based on the emergency pressure releasing valve as the key.The simulation experiment system could individually control the two high flow channels of the emergency pressure releasing valve and could have a different degree pipe bursting simulation.The system was applied to the pipe bursting simulation experiment in the underground mine and the pipe bursting pressure features obtained from the experiment and the theoretical analysis were fully the same.Based on the theoretical analysis and the experiment,the paper provide the judgment basis of the pipe bursting for the high pressure pipeline,which could provide the references to the system design of the high pressure emulsion liquid pumping station and the protection of the pipe bursting accident occurred in the underground mine.
The structure and dynamics of a reciprocating pump liquid end affect the volumetric efficiency and net positive suction head. To match the kinematics with theoretical parameters, reciprocating pump valve motion and flow visualization tests and computational fluid dynamics (CFD) analyses were performed on a wing-guided bevel discharge valve in a horizontal quintuple single-acting reciprocating pump. The valve motion test results showed that the maximum pump valve displacement and the pump valve opening and closing durations were approximately 8.3 mm, 29 ms, and 38 ms, respectively. The corresponding flow visualization test results were 11.4 mm, 9.5 ms, and 35.5 ms. The valve closing durations obtained from the valve motion and flow visualization tests are approximately twice as high as the U-Adolph prediction. The maximum displacement obtained from the valve motion test is consistent with the U-Adolph prediction. Three-dimensional CFD analyses were performed to investigate the flow states, pressure, and velocity characteristics of the discharge valve opening. Finally, the proposed method was applied to develop a new horizontal quintuple single-acting reciprocating pump with a rated flow rate of 1250 L/min and pressure of 40 MPa. This developed pump exhibited good performance and excellent reliability.
The contact behavior of a stepseal affects its reliability and remaining life. In this study, experimental and numerical analyses were performed to investigate the contact behavior of a typical stepseal. Its dimensions and material properties were also tested. The Mooney–Rivlin hyperelastic model was used to fit the stress–strain data of the rubber. A static contact pressure of 105.1 MPa was obtained using the Fujifilm pressure measurement film. A finite element model of a stepseal with reasonable element sizes was established. A comparison between the experimental results and finite element (FE) predictions shows that the finite element method underpredicts the maximum static contact pressure and contact length. For the maximum contact pressure, the test results were approximately 30.4% higher than those of the FE predictions.
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