An investigation into the swash plate vibration and pressure pulsation of piston pumps based on full fluid-structure interactions

In this paper, dynamic analyses of the swash plate vibration and pressure pulsation of an aircraft piston pump based on fluid-structure interactions (FSIs) are presented. Models of the swash plate piston pumps with three FSIs (named full FSIs and non FSI) are given. The simulation results of the discharge pressures at different rotation speeds in the synthesized pump model and experiments show good agreement. The numerical simulation results of the forces on the swash plate and the flow rate of the outlet chamber are presented and compared. The results of the two models show that the discharge pressure pulsation mostly depends on the kinematic relations of the piston slipper-shoe units (FSI-1), and is almost isolated from the swash plate vibration. The full FSIs simulation shows that the swash plate vibration is strongly influenced by the pressure pulsation through the control actuator mechanism (FSI-2) and the control valve mechanism (FSI-3), but the non FSI model does not show the same result. The full FSIs model is much more accurate in predicting the vibration of the swash plate and the pulsation of the discharge pressure than the non FSI model.     

Simulation on the impact pneumatic cylinder with a reservoir

We proposed a novel impact pneumatic cylinder with a reservoir connected to the inlet chamber so that the pneumatic cylinder can achieve a high speed. A reservoir with high-pressure air enabled the cylirider to achieve considerable＇acceleration when it began to Work. We established a mathematical model to simulate the behaviors of an impact pneumatic cylinder, focusing on the relationships of the maximum piston speed with the air supply pressure and the reservoir volume. The results show that the reservoir .can help significantly enhance the pneumatic system velocity. When the reservoir volume is less than double the cylinder volume, an increase in the reservoir volume is more effective in increasing the maximum piston velocity.     

正逆向重构技术在航空发动机机匣中的应用

为提高传统正、逆向工程设计中的模型重构效率与精度,解决航空发动机机匣因形状复杂导致实体造型困难的问题,研究逆向工程与正向建模相结合的模型重构方法及其特点。以某型航空活塞发动机机匣为研究对象,绘制机匣正逆向混合重建流程图,搭建测量扫描环境,利用三维扫描设备对机匣形面进行数据采集,并使用Geomagic Design X等软件进行数据处理与优化,最终得到机匣数字重构模型。通过偏差检测分析得出,模型平均重构精度误差小于0.5mm,重要配合端面平均误差小于0.1mm,与实际情况相吻合,验证了正逆向重构技术的正确性与便捷性,对航空发动机机匣性能预测、疲劳仿真及结构维修具有一定指导意义。     

基于Simulink的膜式空气弹簧研究

活塞缸式模型有其局限性,为了普遍地反映膜式空气弹簧的特性,应用Simulink建立了空气弹簧悬架单轮模型、压力模型、有效面积模型、有效容积模型、滤波白噪声模型。通过对膜式空气弹簧特性的仿真分析,探索了弹簧位移—弹力的非线性特性。在空气弹簧建模过程中确定了相关参数,对弹簧的几何特性和力学性能进行了详细的推导。通过随机路面输入信号波形与仿真结果的对比,验证了改进型活塞缸式模型的正确性,可以更真实地描述弹簧的变化特性。     

Three-dimensional transient numerical simulation for gas exchange process in a four-stroke motorcycle engine

INTRODUCTION In-cylinder flow characteristics during fuel in-jection and subsequent interactions with fuel sprays and combustion are important effect on engine per-formance and exhaust emissions of an engine(Floch et al.,1998;Kim et al.,1999).Four key parameters control the flow field in an engine:the mean flow components,the stability of the mean flow,the tem-poral turbulence evolution during the intake and compression strokes,and the mean velocity near the spark gap at the time of ignit…     

Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

In this paper,a new pressure reducing valve(PRV) with an orifice plate is proposed.The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV.A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure,outlet temperature,velocity,and superheat.A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss.The governing equations for internal flow numerical simulation are composed of the continuity,momentum,energy and k-ε transport equations,based on isotropic eddy viscosity theory.Different valve plug displacement models were built to describe the double throttling process.Our analysis shows that the steam pressure drops twice and the degree of superheat increases.There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity.After modifying the structure,the numerical results show a better performance of steam flow.     

基于Multisim10的积分运算电路的仿真

通过实例介绍Multisim10电路仿真软件在集成运放积分运算中的仿真演示,对三种输入情况积分运算过程进行仿真分析,弥补学生在数学分析和理论计算电路中的不足,增强学生分析和解决问题的能力。仿真波形与理论分析值比较吻合证实了仿真实验的有效性。     

电动汽车用永磁同步电机模糊控制

本文研究了电动汽车用的正弦波永磁同步电机（PMSM）模糊控制的仿真分析。分析了永磁同步电机用于矢量控制的数学模型，并建立了基于其数学模型的电机控制仿真软件包。在PMSM双闭环调速系统中，电流环采用滞环电流调节器，速度环采用参数自调整模糊PI控制。通过对传统PI控制和模糊PI控制方法的仿真实验，去验证这种模糊PI控制方法响应快、无超调，与传统PI控制方法相比具有更好的稳定性和抗干扰能力。所开发的电动汽车用的永磁同步电动机驱动系统具有良好的性能，能够很好地满足电动汽车性能要求。     

Single-acting double-stator multi-pumps and multi-motors

We investigated a series of novel motors and pumps with a new structure called double-stator. Double-stator can be used as pump or motor just for the working condition on demand. A certain amount of pumps or motors are formed in one shell and these subpumps or submotors can work alone or in company without influence on other pumps or moters. This kind of double-stator pumps （motors） are called multi-pumps （multi-motors）. Through the analysis of multifarious connection modes of single-acting double-stator multi-pumps and multi-motors, the mathematical expressions of output flow rate, rotational speed and torque are acquired. The results indicate that different flow rates can be provided by one fixed displacement double-stator multi-pump system under the condition of an unalterable driven speed. Likewise, under the terms of a fixed input flow and without complex variable mechanisms, the functions of double speeds, multiple speeds and even differential connection can be realized by a double-stator multi-motor system with various output rotational speeds and torques.     

基于AMESim的装载机液压制动系统设计与仿真

装载机向着重载高速智能化方向发展,对其制动系统提出了更高的要求.动力制动系统以其优越的制动性能及可靠性被广泛应用于工程装备领域.本文分析了全液压湿式制动系统的工作原理,根据简化后的制动系统工作原理,建立了全液压湿式制动系统的数学模型,并利用AMESim仿真平台搭建了全液压湿式制动系统的仿真模型.在此基础上对全液压湿式制动系统制动性能进行仿真分析.仿真结果表明:从制动盘与摩擦片开始接触,制动力上升时间为0.1 s,且制动力上升分为3个阶段,解除制动时制动压力下降时间也为0.1 s.蓄能器充满油液后,至下一次充液可以实施约4次制动.活塞在0.1 s的时间内便达到了极限位置0.8 mm.     

Numerical analysis of flow and cavitation characteristics in a pilot-control globe valve with different valve core displacements

The pilot-control globe valve (PCGV) is a novel globe valve with a piston-type valve core and a small pilot valve. It can utilize a pressure difference to control the state of the main valve by the pilot valve. In this paper, a mathematical model of PCGV is established and a computational fluid dynamics (CFD) method is used to numerically simulate its flow and cavitation characteristics. Analysis of the pressure difference between the upside and downside of the valve core and comparison with similar previous work increase the reliability of the simulation. Then an analysis of flow and cavitation characteristics is carried out with three comparisons: a comparison between opened and closed states, a comparison between different inlet velocities, and a comparison between different valve core displacements. The results demonstrate that the vapor volume fraction reaches its peak point at the valve seat near the outlet tube, and that a higher inlet velocity or smaller valve core displacement can cause greater cavitation damage. This study can help further design work for optimization and engineering applications of PCGV.     

土仓压力与掘进参数相关性分析及预测模型

提出一种基于长短期神经网络的深度学习预测模型,依托现场数据对土仓压力进行预测。结果表明,在5个可控因素的基础上,增加与土仓压力具有相关关系的不可控因素作为输入,评价指标平均绝对误差、均方误差分别降低了0.901%、0.021%,校正后的决定系数提高了16%,为土仓压力的精准预测和设定提供了借鉴。     

基于Simulink的整车行驶模型的建立与仿真

在Simulink环境下建立了整车的行驶动力学模型,模型包括加速判断模块、加速行驶模块、匀速行驶模块和输入模块,输入模块以节气门开度为参数。仿真结果与汽车实际运行相符合。该模型可以与发动机模型一起用于发动机电控系统的开发。     

Effects of structural parameters and rigidity of driving diaphragm on flow characteristics of micro valveless pump

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英语研究论文讨论部分中的强势语

强势语是英语研究论文中常用的修饰作者论断的语言手段。在研究论文的讨论部分所使用的强势语相对丰富。强势语对增加陈述力度、表达确信、增强说服力起着重要作用,人文社会科学和自然科学研究论文所使用的强势语不但频次有差异,而且所使用的强势语类型、形式和功能也表现出不同的特点,这些差别与不同学科的论证策略和研究对象和方法的不同密切相关。     

助推器附近二维激波边界层干扰的数值分析

本文利用二维雷诺平均的Navier-Stokes方程，采用K-ε湍流模式，运用有限体积法，对大型运载火箭的助推器与芯级的激 波边界层干扰进行了二维数值模拟.数值结果表明在助推器激波的干扰下，芯级边界层流场明显出现了分离和再附过程。助推器头 部形状对流场有显著的影响，在半球助推器头形状情形下由于产生丁较强的弓形激波，边界层的分离和再附过程最显著，压力分布 最复杂。助推器与芯级距离对流场也有显著的影响，距离较小时，压力系数较大，激波边界层的强干扰会产生分离区甚至分离泡。     

Stress uniformity process of specimens in SHPB test under different loading conditions of rectangular and half-sine input waves

Based on the characteristics of 1D waves,the stress uniformity process in specimens under different loading conditions of rectangular and half-sine input waves was analyzed in split Hopkinson pressure bar (SHPB) test.The results show that the times of an elastic wave propa-gating from one end to the other in a specimen to attain stress equilibrium,is related to input wave-forms and relative mechanical impedance between the specimen and the input/output bars.Here-into,with the increae of the relative impedance,the times decreases under rectangular input waves loading,while it increases under half-sine input wave loading.The dimensionless stress value of specimen corresponding to the status of stress equilibrium increases with the increase of the rela-tive mechanical impedance.However,the dimensionless stress value under half-sine input wave loading is significantly lower than the value under rectangular input wave loading for specimen with low mechanical impedance,and the relative differentia of the dimensionless stress values under two loading conditions decreases with the increase of the relative mechanical impedance.In gen-eral,the forced state of specimen with relatively low mechanical impedance under half-sine input wave loading is evidently superior to the state under rectangular input wave loading in SHPB test,and the advantages of forced state under half-sine input wave loading turns weak with the increase of the relative mechanical impedance.     

Simulation and experimental evaluation of a combustion-powered actuator for hopping

A combustion-powered actuator has been proposed in our previous work (Wang et al., 2015), and it has shown great power hopping ability. To explore the hopping process and output performance of the actuator, the model of an actuator driving the hopping process is investigated through theoretical analysis and experimental validation. Firstly, the structure of the actuator and hopping process are described briefly, and the dynamic models of the process are constructed. Secondly, the thermodynamic model of the actuator is established by the Wiebe heat release function and the input energy density is computed by Chemkin for when propane and nitrous oxide with different equivalence ratios are injected into the chamber. Thus, the thermodynamic model is obtained by integrating dynamic and thermodynamic equations. After that, a few output performance parameters are identified to assess system performance. Lastly, the experimental rig of the combustion actuator is set up to test the displacement and pressure of the actuator driven hopping process. By solving the thermodynamic equations, the post-combustion pressure, the displacement and the velocity varying with time are computed, and are compared with the test results, indicating that the computational results match the experimental test well. At the end of the stroke, the velocities of the experiment and simulation are 6.5 m/s and 6.99 m/s, respectively. The hopping results are compared with the simulation when different pressures under equivalence ratio of 1 are injected, and the maximum and minimum deviations are 14.45% and 1.83%, respectively.     

Effects of structural parameters and rigidity of driving diaphragm on flow characteristics of micro valveless pump

The structure and operating principle of micro valveless pump were investigated theoretically and experimentally. The mathematical model of pressure and flow rate within the micro nozzle/diffuser was established to analyze the effects of nozzle/diffuser parameters on the output flow rate of the micro valveless pump. The experiments were carried out with different structural parameters, driving frequencies, vibration amplitudes and stiffness of the driving diaphragms. Effects of the structural parameters and driving conditions on the operation performance of the pump are discussed in detail. The work provides useful reference for structure optimization selection of the driving diaphragm of micro valveless pump. Project supported by National Natural Science Foundation of China (Nos. 50175098, 59835160)     

Modeling and analysis of wet clutch engagement characteristics

A mathematical model was developed to analyze the characteristics of the wet clutch during engagement. The lubricant squeeze action was simulated with Patir and Cheng average flow model in which the permeability of friction material is taken into account, and the asperity load is calculated according to the Greenwood and Tripp approach. In this model, effects of friction material permeability, applied load and driving velocity on the engagement characteristics of the wet clutch were studied. The results show that friction material with high permeability reduces the film thickness rapidly and increases the torque peak; the applied load increases the asperity contact pressure and the friction torque, and reduces the engagement time; the driving velocity mainly increases the engagement time. The theoretical torque and relative velocity curves agree qualitatively with the experimental ones, which verifies the wet clutch engagement model.