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由于挖掘机采用定量液压系统的功率利用率较低(约为54%-60%),目前一般选用功率利用率较高的变量系统(两种系统比较如图1所示)。液压变量系统如图2所示。在功率调节器中,控制活塞右面有泵出口压力作用,左面有弹簧力作用,其控制过程为:外负载增大十活塞左移(弹簧被压缩)十泵斜盘摆角减小十泵排量下降十泵转速降低最终达到工作机械速度随外载增大而减少;随外载减少而增大。确保发动机功率在泵的调节范围内得到充分利用。这种恒功率控制系统在确定泵的输入功率时,必须考虑发动机的工作条件(如超载、高海拔作业等),因此,泵的… 相似文献
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发动机与泵扭矩的不匹配所造成发动机转速波动是挖掘机能量浪费的主要原因.分析了发动机与泵稳定工作条件下的扭矩匹配关系,试验研究了泵扭矩调整的影响因素,确定了调整泵吸收扭矩让发动机工作在调速特性曲线的电控节能控制目标,建立了基于PID(Proportion Integration Differentiation)的泵扭矩调整方案并开展了泵扭矩调整试验.试验结果表明:挖掘机液压系统自带压力切断功能可实现无负荷和溢流工况下的节能控制,电控系统仅在泵正常工作范围内通过改变比例阀电流调整泵扭矩,泵扭矩的控制策略在工作初始和工作过程中的调整方法有差异,采用的双闭环PID控制方法能保证发动机稳定在调速特性范围内,这为开发节能效果更好的挖掘机节能控制系统打下基础. 相似文献
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PC2OO-6型全液压履带式挖掘机有时会出现整机工作无力、动作缓慢的现象,我们分析其主要原因是液压系统出现了故障。1.主泵压力偏低PC2OO-6型挖掘机采用双联斜盘式轴向变量柱塞泵。正常情况下,主泵输出油压≥30 MPa。如果主泵的柱塞与缸体之间或者缸体的端面与配流盘之间的磨损量超过标准(柱塞 相似文献
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EX200-2型挖掘机主泵采用了泵调节器电子化的负荷传感功率控制系统,本文通过对主泵伺服变量系统的组成和工作原理进行分析,并详细分析了主泵伺服变量系统的故障诊断与排除方法.以对该设备的检修起到一定的指导作用. 相似文献
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一台小松PC360-7型挖掘机的发动机大修后试机,发现工作无力,发动机空载高怠速为2 170 r/min,一旦带负荷或做溢流时,转速立即下降到1 650 r/min,转速差达520 r/min,主液压泵油压从33 MPa下降到28 MPa,挖掘机无法正常工作。在发动机转速下降时,检查排气管排烟正常。由于该挖掘机发动机大修前液压系统工作正常,所以排查的重点放在发动机上。 相似文献
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R962全液压挖掘机是从西德进口的,其回转机构液压系统在使用中多次发生回转失灵,从而导致更换回转泵.每台泵价值10几万元,不仅造成很大的经济损失,且供货时间长,造成设备利用率低.一、系统分析回转液压系统工作原理见图1.齿轮泵3在发动机带动下从油箱中吸油,并通过功率控制阀实现对挖掘机主泵功率调节和回转泵的补油.回转操作是通过伺服系统驱动回转扭矩控制机构,控制回转泵的摆角以改变回转泵的流量.功率控制阀1和回转扭矩控制机构5均有压力检 相似文献
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开式节流恒功率控制液压系统在小型液压挖掘机上得到了广泛的应用。按照小型挖掘机实际工况特点,推导建立了开式节流系统主泵的动态数学模型,再结合主泵的p-q曲线,分析得出了主泵输出效率与主泵工作参数之间的特性。 相似文献
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Pressure variation is one of the major sources on noise emission in the axial type oil piston pumps. Therefore, it is necessary
that the pressure variation characteristics of the oil hydraulic piston pumps be clarified to reduce the pump noise. Pressure
variations in a cylinder at the discharge region and the pump noise were simultaneously measured with discharge pressures
and rotational speeds during the pump working. To investigate the effects of the pre-compres-sion and the V-notch in the valve
plate, we used the three types of valve plates. In this research, it is clear that the pressure variation characteristics
of axial type oil piston pumps is deeply related to the pre-compression and to the V-notch design in valve plate. Therefore,
we could reduce the pump noise by using the appropriate pre-compression angle and the notch design that are between the suction
port and the discharge port in valve plate. 相似文献
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以D82-19-2型中比转速离心泵为研究对象,根据无过载叶轮约束公式确定叶轮设计方案,选取四种叶轮包角(150°、170°、190°和210°)开展中比转速泵流场及无过载性能的模拟研究。与实验结果相比,模拟所得扬程、效率和功率值误差不超过9%,模拟方法可行。结果表明:当叶片包角由150°增大到210°时,叶轮进口压力提高24%,低速区面积扩大至整个叶轮流道的1/3,叶片对流体的约束能力及抗汽蚀性能增强,但叶轮出口压力降低,大包角下导叶的湍流损失加剧了动能损耗;功率备用系数由1.145减小至1.025,且功率曲线出现极大值,泵的无过载特性更显著,但扬程和效率分别下降了15.4%和4.48%。研究结果为中比转速离心泵的无过载设计提供了理论依据。 相似文献
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对D450-60-10型中比转速离心泵进行无过载优化设计,原始方案采用模型换算法设计模型泵进行试验并换算得到原型泵性能,同时利用Fluent模拟得到模型泵和原型泵性能,对泵性能分析后提出基于叶片出口角、叶轮出口直径和叶轮出口宽度等结构参数的3种原型泵优化方案。结果表明:当叶片出口角β2=10°时,与β2=15°相比,功率曲线的拐点更接近额定工况点,且最大功率下降了6.78%,但会牺牲部分扬程;3种优化方案下离心泵都达到了无过载的要求,功率备用系数K均小于1.2;最佳方案(叶轮出口直径D2=0.49m,叶轮出口宽度b2=0.03m,叶片出口角β2=10°)的功率备用系数最低,为1.09,与原始方案相比,扬程和效率分别提高了6.94%、1.95%,为中比转速离心泵无过载设计提供了参考。 相似文献
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涡轮增压辅助电子水泵是发动机涡轮增压器冷却系统中的重要组成部分。由于涡轮增压器在长时间工作下产生持续高温,对发动机可靠性和寿命产生较大影响,而电子水泵可通过防冻液冷却剂对涡轮增压器进行降温,有效降低涡轮增压器工作温度,保障发动机的持久动力性。分析了电子水泵的常见应用故障并提出了相关的改进方法。 相似文献
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The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump. 相似文献
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Optimum design on lobe shapes of gerotor oil pump 总被引:1,自引:0,他引:1
A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various
applications. In particular the pump is an essential machine element that feeds lubricant oil in an automotive engine. The
subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the two rotors. Usually
the outer one is characterized by lobes with a circular shape, while the inner rotor profile is determined as a conjugate
to the other. For this reason the first topic presented here is the definition of the geometry of the rotors starting from
the design parameters. The choice of these parameters is subject to some limitations in order to limit the pressure angle
between the rotors. Now we will consider the design optimization. The first step is the determination of the instantaneous
flow rate as a function of the design parameter. This allows us to calculate three performance indexes commonly used for the
study of positive displacement pumps: the flow rate irregularity, the specific flow rate, and the specific slipping. These
indexes are used to optimize the design of the pump and to obtain the sets of optimum design parameter. Results obtained from
the analysis enable the designer and manufacturer of the oil pump to be more efficient in this field. 相似文献
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民机液压系统的主泵一般为发动机驱动泵,用作功率提取装置从发动机提取功率为液压系统提供主要能源.发动机驱动泵为恒压变量泵,通过联轴器与发动机上的齿轮箱连接,随发动机启动而工作.因发动机驱动泵与发动机为机械连接,不能人工关闭,但在特定的飞行阶段需要发动机驱动泵能够卸荷工作,在试验时也需要EDP不能输出压力的状态.针对上述要... 相似文献