共查询到20条相似文献，搜索用时 187 毫秒
1.
《浙江大学学报(A卷英文版)》2016,(3)
目的:航空柱塞泵是飞机液压系统的核心元件,具有高压高转速的特点,其压力脉动是飞机液压系统振动的主要激励源,对飞机液压系统的安全性和可靠性具有重要影响。本文首次全面分析了压力脉动和斜盘振动之间的关系,对降低柱塞泵的压力脉动、提高其可靠性具有重要理论意义。创新点:1.将柱塞泵压力脉动和斜盘振动相结合,综合分析两者相互作用关系;2.综合分析柱塞、斜盘控制阀、斜盘控制柱塞三者间的作用关系,建立全耦合模型。通过仿真分析和实验验证,指出普通模型的局限性以及全耦合模型在研究斜盘振动与压力脉动的真实内在关系的可靠性。方法:1.通过仿真和试验对比,分析全耦合模型和普通模型在压力脉动仿真结果上的差别及原因;2.通过对比分析,确定全耦合模型在斜盘振动仿真方面具有的较高精度;3.通过柱塞泵高压腔流量仿真结果,讨论柱塞泵压力脉动成因以及与斜盘的振动关系;4.通过斜盘力矩仿真分析讨论斜盘振动成因以及与压力脉动的关系;5.通过分析压力脉动、斜盘振动和转速三者间的关系,探讨减轻斜盘振动与减小压力脉动的有效途径。结论:1.全耦合模型的精确度比普通模型高,能较好地预测斜盘振动和压力脉动状态。2.斜盘振动的基频部分主要取决于压力脉动的动态特性,同时还受控制阀机构(FSI-3)和变量柱塞机构(FSI-2)的动态特性影响。压力脉动主要由柱塞泵的柱塞运动关系(FSI-1)决定,不受斜盘高频振动影响。 相似文献
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本文针对《电工技术》中电源的几种等效变换,通过对几个电路分析．分别说明了电源等效变换的三种情况：同种电源的等效：电压源及电流源之间的等效：在求解电路时涉及地电源的第三种等效,即广义电源的等效。作者通过以上三种电源的等效变换的教学研讨,使学生理解电源等效变换在电路分析中的灵活运用。 相似文献
3.
本文通过用等效模型求解一例静电学问题,阐明在普物教学中,应重视用等效模型或等效方法来解决一些通常方法很难解决甚至无法解决的问题． 相似文献
4.
带电粒子在匀强电场和重力场组成的复合场中做圆周运动的问题是高中物理教学中一类重要而典型的题型。对于这类问题，若采用常规方法求解，过程复杂，运算量大。若采用“等效法”求解，则能避开复杂的运算，过程比较简捷。所谓“等效法”就是先求出重力与电场力的合力，将这个合力视为一个“等效重力”，将α=F合/m视为“等效重力加速度”。再将物体在重力场中做圆周运动的规律迁移到等效重力场中分析求解即可。下面通过两个实例分析说明“等效法”在此类问题中的应用。 相似文献
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曹彦检 《衡阳师范学院学报》2003,24(6):124-126
通过力学中的种种应用，说明了等效变换是力学乃至物理学中最基本的思维方法，它不仅是量的方面的等效代换，而且由量的等效可以引起对物理世界最深刻、最本质的理解。 相似文献
6.
等效是指不同的物理现象、模型、过程等在物理意义、作用效果等方面是相同的,它们之间可以相互替代,而保持结论不变。等效的方法是指面对一个较为复杂的问题,提出一个简单的方案或设想,而使它们的效果相同,从而将问题化难为易。常用的等效方法有等效替代、等效类比、等效假设。在高中物理中等效的思想比比皆是,例如,力的合成和分解是一个力和几个力的等效替代;用平均速度将变速直线运动等效变换为匀速直线运动;平抛、斜抛曲线运动等效为两个直线运动; 相似文献
7.
齐红 《乌鲁木齐成人教育学院学报》1997,(4)
根据二端网络的等效化简方法和等效定义,推导出了电源模型的七种等效变换。用之求解复杂电路中的电流或某一元件的电压和功率,可简化电路、简化分析问题的过程,使解题快而准。 相似文献
8.
从力学角度分析了位于漳州市南靖县书洋镇下版村的裕昌楼，看起来摇摇欲坠，却经受七百年风雨侵蚀和无数次地震的考验，至今依然如故的原因.根据土楼建造程序、“龙骨”架在外墙小槽内与内圈竖直木柱上横梁的事实，提出了土楼的建筑等效结构模型；根据动力学扰动理论确定的扰动区厚度、三合土弹性模量和埋入土墙深度，计算出柔性固定端的等效转动刚度系数；从几何静力学、分析静力学和材料力学的压杆稳定3个方面，分析得出外墙斑驳、楼内“东歪西斜”的福建现存最古老土楼裕昌楼的极限承载能力比一般土楼极限承载能力高25．9%，其原因除墙体中埋入杉木或竹片，甚至放进大石块为墙骨以增强抗力外，力学静定结构是斜而不危另一重要因素. 相似文献
9.
研究了公交车调度的最优策略问题,建立了分时段等间隔发车的综合优化调度模型。采用了时间步长法、等效法以及二者结合的等效时间步长法三种方法求解模型.给出了两个起点站的发车时刻表,得出了总共需要49辆车,共发440辆次,平均抱怨度对10%的随机干扰水平相对改变只有0.53%,能满足实际调度的需要. 相似文献
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11.
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. 相似文献
12.
对阀配流水压轴向柱塞泵进行运动学分析，给出了柱塞相对于缸体和柱塞相对于斜盘的运动分析表达式及仿真曲线。 相似文献
13.
The single cylinder and multi-cylinder pumping dynamics model of a swash plate piston pump were improved.Particular attention has been paid to the design influences of key parts of the valve plate such as relief groove,pre-compression/ expansion and fluid inertia effect of the unsteady flow.Some important parameters,such as the discharge area,discharge coefficient,fluid bulk modulus,were especially analyzed using numerical methods or by experiment-based estimation.Consequently,the mathematical results of pressure pulsation and flow ripple agree well with experimental results from the test-rig of the flow ripple.Therefore,the cross angle and the pre-compression angle of the valve plate was optimized,based on the pumping dynamics model.Considering both the flow ripple and the cylinder pressure of the pump,the cross angle is set to be 2.2° to 2.7° with a pre-compression angle of 1.7° to 2.2°,so the pumping dynamics character can obtain the best result. 相似文献
14.
A good efficiency performance of a pump over a wide range of displacement conditions is crucially important for variable pump control systems to save energy. However, according to the literature, less attention has been paid to the understanding of the efficiency, leakage flow, and compression flow characteristics of the pump with respect to displacement conditions. In this study, a test bench was built, and a novel explicit volumetric loss model was proposed to investigate these problems. The overall efficiency is found to drop considerably with the decreasing displacement. The volumetric losses range from 13% to 47% of the total power losses of pump at the rated speed, under the conditions of pressure ranging from 5 to 35 MPa and displacement ranging from 13% to 100% of full displacement. The highest proportion of compression flow losses in the total volumetric losses of pump at the rated speed can reach up to 41% when the pressure and displacement are greater than 30 MPa and 88% of full displacement, respectively; after that, the proportion gradually decreases with decreasing displacement. However, the leakage flow generally increases with decreasing displacement, or may decrease first and begin to increase after the minimum with the further decrease of displacement. In the components of leakage of slipper/swash plate pair, the squeeze leakage is found to reach a magnitude equal to that of the Poiseuille leakage. The findings can guide the further research and design of pumps with better efficiency performance. 相似文献
15.
林抒毅田源黄晓生孔毅鹏俞智坤 《福建工程学院学报》2020,(3):260-266
针对四线圈非理想耦合对系统输出电流特性的影响,采用等效容性耦合的方法来实现理想的四线圈系统电流输出特性。 首先结合补偿电感的磁集成,减少了无线电能传输系统磁元件数量并缩小其体积,再对等效电路参数的设计进行分析并设计了实验样机。 实验结果验证了容性耦合等效方法的准确性与有效性。 在负载范围内,样机接收端直流输出电流的波动小于8%,传输距离为75 mm时整机输出功率为300 W,效率峰值达到了81.49%。 相似文献
16.
EX220—3型挖掘机是日本日立公司生产的小型履带式挖掘机。该挖掘机有工作装置、上部回转台和行走装置三部分组成。该挖掘机行走速度的改变主要通过行走马达的斜盘角和主泵位移角的配合来实现的。而行走速度控制电路允许挖掘机以三种不同的速度行走,通过对行走速度控制系统分析,找出了行走速度不变化或比规定速度慢的故障原因和排除方法,这对EX220-3挖掘机行走速度不变化或比规定速度慢故障诊断起到一定的指导作用。 相似文献
17.
游士琴 《淮南职业技术学院学报》2002,2(4):105-107
机械在运转过程中，等效力矩和等效转动惯量的周期性变化将导致速度的周期性波动。这种速度波动可用飞轮来调节，其实质是增加机械的转动惯量。从分析飞轮调节作用的原理入手，总结了飞轮转动惯量的计算方法。 相似文献
18.
This paper presents an efficient method for globally optimizing and automating component sizing for rotary traveling wave oscillator arrays. The lumped equivalent model of transmission lines loaded by inverter pairs is evaluated and posynomial functions for oscillation frequency, power dissipation, phase noise, etc. are formulated using transmission line theory. The re- sulting design problem can be posed as a geometric programJning problem, which can be efficiently solved with a convex opti- mization solver. The proposed method can compute the global optima more efficiently than the traditional iterative scheme and various design problems can be solved with the same circuit model. The globally optimal trade-off curves between competing objectives are also computed to carry out robust designs and quickly explore the design space. 相似文献
19.
输油泵为炼化企业流体输送与转运主要设备。基于Pro/Engineer建立了输油泵的整体和所有部件的三维立体模型,然后在3DS Max环境下制作其动态装配动画仿真及渲染输出,最后在Adobe Flash CS4中进行动画的剪辑和修饰;结合AutoCAD绘制二维图形库,并以在PowerPoint界面建立超级链接的形式进行图形调用。综合以上技术开发了一套输油泵计算机三维仿真系统,包含输油泵主要零部件的三维模型、部件装配、整体总装配以及设备运行过程的动态仿真等内容。通过对输油泵的组装过程动态仿真,较好地展示了输油泵整体及部件三维立体动态装配、各部件动态关系等,演示了输油泵的结构和组装过程。在输油泵运营管理和教学培训等实际应用方面都具有重要意义。 相似文献
20.
In the beach well intake system, heat is transferred from soil to fluid when seawater is filtered through the aquifer, providing higher temperature source water to the seawater source heat pump (SWHP) system in winter. A 3-D coupled seepage and heat transfer model for studying beach well intake system is established by adopting the computer code FLUENT. Numerical results of this model are compared with the experimental results under the same conditions. Based on the experiment-verified coupled model, numerical simulation of the supply water temperature is studied over a heating season. Results show that the minimum temperature of supply water is 275.2 K when this intake system continuously provides seawater with flow rate of 35 m3/h to SWHP. Results also indicate that the supply water temperature is higher than seawater, and that the minimum temperature of supply water lags behind seawater, ensuring effective and reliable operation of SWHP. 相似文献