In practical engineering, it is very difficult to obtain data on the slipper wear of hydraulic pumps, especially under high-speed, high-pressure conditions, which limits the development of fault ...diagnosis technology for hydraulic pumps. At present, a test method that can accurately simulate the operating state of the slipper pair under high-speed and high-pressure conditions does not exist. The reliable load-bearing design of the slipper pair is difficult to carry out effectivetest verification, which limits the development of high-speed and high-pressure piston pumps. Therefore, an experimental design method was proposed to directly simulate the high-speed, high-pressure friction state of the slipper pair based on the change law of reprinting residual pressing force.
Remanufacturing is an effective measure for circular economy. In a maintenance business of mining machines, remanufactured parts are used as spare parts. In this business, forecasting demand of parts ...is critical for reproduction planning. This research proposes a demand forecasting model regarding the replacement as probability event. In the forecasting model, the demand is simulated using the actual data of mining machinery operation. The results show that, although there exist gaps between the simulated and the actual values, the simulation succeeded in reproducing rough trends of the demand. Solving these gaps will increase the accuracy of the demand forecast.
Throughout previous practice, estimating the life of aviation hydraulic drive assemblies has been utilizing a variant, which requires
conducting long-lasting studies of the drive assemblies until ...they move to the unfitness state. Such studies, which enable estimating life a posteriori, are costly and long-lasting. Hence the need to look for new strategies for estimating life. The article presents
a method of estimating the durability of a hydraulic drive assembly based on the control of its change in technical condition. Inspection of the technical condition enables timely detection of the condition before the emergency hydraulic assembly. The novelty of the
method is to use, to detect the condition before the emergency team, the principle of determining the pre-emptive control parameter
tolerance. Pre-emptive tolerances are a set of control parameter values between threshold levels and pre-emergency (allowable)
levels. The intensity of depletion of durability (intensity of aging, wear) is random. The paper presents a stochastic description of
the control parameter change and the resulting empirical relationships between the control parameter verification time probability
density (verification periodicity) and the control parameter value change probability density. The inter-relations between these two
functions were described. It also presents empirical relationships enabling the determination of the permissible value for the control
parameters and the periodicity of the control parameter checks after exceeding the limit value. An example of estimating the life of
a hydraulic piston pump on-board an aircraft operated in the Polish Air Forces was shown. The permissible values and the time
for the first control parameter verification after exceeding the limit value were determined for selected control parameters of the
hydraulic pump. The proposed method binds life (fitness time) with the physical wear mechanisms concerning the assemblies. It
can be applied in work aimed at determining the resource life of technical equipment. Furthermore, it enables utilizing technical
equipment according to a technical state strategy with monitoring the parameters.
•New requirements for hydraulic pump/motors caused by new system architectures.•Design challenges for pump/motors with reversed speed, pressure sides and swash angle.•Evaluation of commutation ...features for multi-quadrant operation.
In search of more efficient hydraulic systems, new system architectures are explored. These system architectures are often electrically driven and include energy recuperation. This requires hydraulic machines to function both as pumps, converting mechanical power into hydraulic power, and as motors, converting hydraulic power back into mechanical power. However, the availability of machines that can operate in all desired modes is limited. This indicates that operation in multiple modes comes with performance penalties. This paper highlights the challenges for multi-quadrant operation of hydraulic piston pump/motors, with a particular focus on commutation, i.e., the transition between high- and low-pressure level for each chamber. Various commutation strategies for piston machines are examined. Furthermore, other important aspects for pump/motor operation such as hydrostatic compensation ratios, design of inlet channels, low-speed capability, and flow control through speed or displacement control are discussed. The article shows that the design of multi-quadrant machines is challenging, and this has to be considered when choosing the system architecture.
Cavitation caused by insufficient suction is a major factor that influences the life of aircraft pumps. Currently, pressurizing the tank can solve the cavitation problem under steady large-flow ...conditions. However, this method is not always effective under transient conditions (from zero flow to full flow in a very short time). Moreover, to apply and design other measures, such as a boost impeller, the suction dynamics during the transient period must be investigated. In this paper, a novel approach based on the pressure wave propagation theory is proposed for predicting the inlet pressure of an aircraft pump under transient conditions. First, a dynamic model of a typical aircraft pump is established in the form of differential equations. Then, the transient flow model of the inlet line is described using momentum and continuity equations, and the governing equations are discretized by the method of characteristics and the finite difference method. The simulated results are in good agreement with the results from verification tests. Further simulation analysis indicates that the wave velocity and transient time may influence the inlet and reservoir pressure as well as the size of the inlet line. Finally, solutions for upgrading the inlet pressure are discussed. These solutions provide guidelines for designing inlet installations.
•A novel time-frequency analysis approach based on EWT-VCR.•First application of full vector spectrum improved by EWT-VCR in pumps’ data fusion.•The novel feature FVFE to efficiently describe pumps’ ...degradation process.•Two case studies highlighting good performance of the proposed methodology.
The full vector spectrum is an effective and efficient tool for homologous multi-sensor data fusion in rotating machinery. However, this methodology just takes Fourier Transform to obtain the harmonic trajectory information hidden in multi-sensor data and it has some drawbacks of processing nonlinear, multi-frequency and noise-containing data. To address this critical issue, this paper provides a novel approach called EWT-VCR based on Empirical Wavelet Transform (EWT) and Variance Contribution Rate (VCR) to improve the adaptability and accuracy of the fusion method. EWT is introduced as a signal preprocessing technique to decompose complex signals into variable frequency bands. And VCR is proposed to denoise, fuse EWT components at different frequency bands, and enhance useful harmonic components. The full vector spectrum technology is utilized to carry out the full vector information fusion of the improved multi-sensor signals for further spectrum analysis. The proposed methodology is applied to multi-channel vibration signal fusion for hydraulic pumps to detect specific frequencies related to pump’s degradation process and a novel degradation feature named Full Vector Factor Entropy (FVFE) is extracted to describe hydraulic pump’s degradation process during its life cycle. The effectiveness of the proposed methods is validated through two experimental cases.
This document presents a revised translation to the English language work developed more than 40 years ago by the first author. It further summarizes a common misinterpretation of the method and ...succinctly describes a graphical procedure to correctly determine the derived displacement volume of a pump or a motor. The original work contains a directive for the determination of the derived displacement volume of hydrostatic positive displacement pumps and motors, from volumetric (flow and speed) measurements. The procedure is based on the definition of the derived displaced volume, defined as: The volumetric flow pushed or admitted by hydrostatic positive displacement pumps and motors per (shaft) revolution, at zero internal and external leakage flow conditions.
Introduction. Russian and foreign manufacturers of volumetric hydraulic drives recommend using hydraulic oils (working fluid) from certain manufacturers for their hydraulic units: Lukoil, ...Gazpromneft, Mobil, Hydrau Gard, SHELL, Total, etc. The oils have different physicochemical properties, because of different additive packages in their composition. However, changes in these properties during operation are a negative factor. In this regard, the physicochemical properties of the power fluid will affect the determination of diagnostic parameters, namely their accuracy and reliability. Therefore, when monitoring the technical condition of volumetric hydraulic drives in bench equipment, it is necessary to use hydraulic oil, with constant physico-chemical properties. To select power fluid for determining the parameters of diagnosing new and existing volumetric hydraulic drives of Russian and foreign production with a minimum error, it is necessary to conduct experimental studies.
Aim of the Article. The study was aimed at determining the dependence of changes in the parameters of diagnosing new and operating hydraulic units of Russian and foreign production on the power fluid temperature.
Materials and Methods. As power fluid there were used Hydraulic oils MGE-46B and SHELL TELLUS S2 V46 recommended by manufacturers for volumetric hydraulic drives НST-90, НST-112 and Danfoss Power Solutions 90-series respectively. During the experiment, the volume efficiency and torque of volumetric hydraulic drives were tested as diagnostic parameters. The tests were carried out on specialized bench equipment in accordance with the requirements (methodology) of the manufacturers.
Results. Experimental studies presented in the article have shown that the changes in the temperature of the power fluid affect significantly the accuracy of the diagnosed parameters of hydraulic units under study. It was found that the power fluid SHELL TELLUS S2 V46 allows reliably determining the diagnostic parameters of new and having operating time domestic hydraulic units. Optimal temperature ranges equal to 60...69 °C were obtained for power fluid – MGE-46V when testing new and having operating time foreign hydraulic units Danfoss Power Solutions 90-series.
Discussion and Conclusion. It has been found that the power fluid MGE-46B in optimal temperature ranges ensures the completeness and high accuracy of diagnosing new and having operating time hydraulic units of Russian and foreign production in accordance with the requirements of GOST 17108 and manufacturers. Therefore, this hydraulic oil can be used as a universal power fluid for monitoring the technical condition of various hydraulic units at repair enterprises.
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