Wyniki wyszukiwania - BazTech

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Wear processes of hydraulic plunger and barrel assemblies connected with the time of their work

Ułanowicz L.

Journal of KONES

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2014

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Vol. 21, No. 4

515--524

EN

The article discusses the wear processes of hydraulic plunger assemblies connected with the time of their work and the impact exerted by these processes on the value of parameters of a hydraulic plunger pump. It describes working conditions and loading of a hydraulic plunger assembly. The paper presents also the results of empirical analyses of the wear process of the connection of the plunger base with the working surface of the swivel disk, which is related to time and conditions of its work. It discusses the impact of the loading value and sliding speed on the character and intensity of the wear of the connection between the plunger base and the working surface of a swivel disk. Furthermore, it presents a general characteristic and mechanism responsible for the wear of the hydraulic plunger assembly through oxidation. The article also analyses the impact of the hardness of materials used for producing the hydraulic plunger assembly on the intensity of its wear. Another issue is the dependence of the coefficient of friction in the hydraulic plunger assembly on the contact pressure at different sliding speeds. Finally, the paper discusses the impact of wearing of the cooperating plunger base and the working surface of the swivel disk on the initial parameters of the hydraulic pump at a given working pressure and its volumetric efficiency.

2

Effect of dynamic properties attributable to hydraulic lines onto operation of avionic

Ułanowicz L.

Journal of KONES

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2011

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Vol. 18, No. 4

535-542

EN

The present paper is dedicated to discuss how dynamic parameters of a hydraulic line intended to transfer hydraulic power from a source of hydraulic power (a hydraulic pump) to an actuating device (a hydraulic motor) can affect operation of an avionic hydraulic drive. Avionic hydraulic drives are operated with fast-varying waveforms of flow intensities and pressures. It is why analysis of most hydraulic drive systems must take account of compressibility of working fluid and elasticity of hydraulic lines. It leads to a wave model for propagation of energy variation down a hydraulic line (a pipe). The paper deals with flow of a compressible liquid via a hydraulic line with flexible walls. Theoretical deliberations were successfully verified by experimental research studies that were carried out on a dedicated test bench, therefore the presented amplitude vs. frequency characteristic curves of the hydraulic line could be obtained from both theoretical considerations and experimental research studied. The experimental research studies were carried out for hydraulic line terminated with a fixed flow restrictor alone and a flow restrictor combined with a hydraulic accumulator as well as for a hydraulic line supplied from a source of constant pressure and terminated with a valve with adjustable flow together with a hydraulic accumulator. The theoretical calculations for the amplitude vs. frequency characteristic curve are based on a model for a hydraulic line with its resistance depending on frequency.

3

Outline of the method for prediction of lifetime achieved by ayionic hydraulic drives operated under real field conditions

Ułanowicz L.

Journal of KONES

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2009

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Vol. 16, No. 2

473-484

EN

The presented approach to predict lifetime of avionic hydraulic drives belongs to a priori (accelerated) methods as by its nature it does not reeuire to continue tests until a hydraulic subassembly or drive reaches its boundary value of a structural parameter. The method uses distributions of a random variable with time-dependent variance as models for lifetime prediction. Variations of structural parameters over a discretional period of time are described with use of the Gaussian distribution with the assumption that the course of the process when the structural parameters are subject to deterioration comprises the entire probabilistic characteristic that defines resistance of the hydraulic drive to a wear and tear process. In that context distributions of characteristics for variations of structural parameters were determined for a selected period of time and it served as a basis to find out parameters for the distribution of the defect-free operation time. The completed functional and design decomposition of an example avionic hydraulic drive made it possible to obtain a hierarchical description of the hydraulic drive, to identify its structural parameters that are available during the drive operation as well as to define a set of measurable out put parameters of a system, a module (a hydraulic system) and a block (a hydraulic subassembly). The set of measurable output parameters attributable to the hydraulic system in question is described with use of mathematic equations that result from fundamental equations for hydraulic systems dynamics, i.e. the mass conservation law, the principle of momentum and angular momentum conservation as well as the energy conservation law.