MODERN TRENDS OF DESIGN, RESEARCH AND USE OF HYDRAULIC MACHINES IN DRIVES OF MECHANISMS AND TRANSMISSIONS (REVIEW ARTICLE)

The work is devoted to an overview of modern trends in the design, research and use of hydraulic machines in the drives of mechanisms and transmissions. The analysis of the use of hydromechanical transmissions has been carried out. The advantages and disadvantages of hydromechanical transmissions in comparison with mechanical ones are described. A brief overview of modern approaches to the design of new products, taking into account the existing information technologies, is carried out. We have analyzed modern software products designed to support the project at different stages of the product life cycle. It has been found that at the present time the appearance of individual variants of highly specialized software with a modern interface for synthesizing the structure of a designed product does not make it possible to solve the problems of synthesis and structural analysis of hydro-mechanical transmissions. A review of the analysis of operational factors affecting the fault tolerance and operating parameters of hydrostatic transmissions in general and hydromechanical transmission in particular is carried out. We have also considered the examples of technical solutions that allow to reduce the number of failures associated with the influence of one factor or another, as well as allow to reduce its influence on the parameters of the mechanism. The analysis of sources with information on the study of the parameters of hydrostatic transmissions using field tests or the mathematical apparatus developed by the authors is carried out. The ways of solving problems arising at the stages of design research are outlined. Keywords: design, hydrostatic transmission, hydromechanical transmission, influence of operational factors, synthesis

Measuring system for monitoring the polydimensional deformation of superstructures of bridges and over-bridges improvement of volume hydraulic drive construction and road machines using flow shareholders

Due to its advantages, the hydraulic drive is widely used in road construction machines. Depending on its design, the share of the hydraulic drive, which is the most expensive unit of a road construction machine, accounts for thirty to eighty percent of all failures. Reliable hydraulic drive, provides, to a large extent, the reliability of the whole machine and the efficiency of the construction organization as a whole. The efficiency of the hydraulic drive of construction machines, and, as a consequence, the machines themselves, is ensured by a set of measures, among which the most important is the quality design, manufacture and operation, combined into a single structural system. Depending on the quality of cleaning of the working fluid, the service life of hydraulic machines can be increased or decreased several times. Accumulation of pollutants in the hydraulic drive, the hardness of which is significantly higher than the hardness of metals, causes rapid wear of the surfaces of hydraulic units and the service life is rapidly reduced. Cavitation in the pump is accompanied by a pulsation of fluid pressure and noise. These pulsations are due to the return flow of fluid from the discharge cavity of the pump, which is accompanied by hydraulic shocks and as a result of alternating shocks, a pressure pulsation in the discharge line of the pump. The amplitude of these pulsations can, under known conditions, reach a value that causes the destruction of the pump. The possibility of cavitation can be reduced by rational choice of modes of operation of the hydraulic system and the correct design of its units, but this phenomenon can be completely eliminated only by using auxiliary pumping pumps, as well as increasing the pressure in the suction line of the pump. On the basis of the analysis of perspective directions of improvement of the hydraulic drive of the excavator the following improved scheme of it is developed. Usually only high-flow hydraulic motors can be used in flow dividers. But in our case it is necessary that the device had, first of all, small mechanical losses and small cost, and accuracy of division of working liquid which follows on filters can be small. In the volume flow divider, hydraulic motors are used: gear, piston, vane, screw, roller. The simplest dividers of volume type are paired (connected by shafts) hydraulic motors of lamellar (vane) and roller types. Hydraulic motors in this scheme are flow measuring devices (dispensers), which supply for one revolution the volume of liquid, equal without taking into account the leaks in the hydraulic motor, its working volume. The use of a flow divider as a source of hydraulic energy makes it possible to improve the hydraulic drive by combining in a single system the purification of the working fluid and the ejector feed of the pump. The most promising, in terms of cost, are flow dividers based on vane and rotary hydraulic motors..

Analysis of the characteristics of axial-piston hydraulic machines for drives for maintenance of airfields and planes

Is an integral part of the development of the concept of forming a standard range of transport and technological hydrophilic modular means for maintenance of airfields and aircraft. Goal. Development of scientifically sound recommendations for determining the rational parameters of the hydraulic system with automation of control and energy saving during operation of modular vehicles for maintenance of airfields and aircraft, taking into account the potential of domestic engineering and critical imports of units. Methodology. Analysis of the development of axial-piston pumps and motors according to the manufacturers' catalogs taking into account the needs of modular vehicles for maintenance of airfields and aircraft, in particular, taking into account the creation of modern hydraulic machines by enterprise «Hydrosila» by increasing pressure, speed and development new regulators. Results. It is established that the domestic nomenclature of modern pumps and motors of axial piston type allows to create three-dimensional hydraulic drives with power to 110 kW for transmissions with machine stepless remote electrohydraulic regulation of speed of rotation of wheels of modular vehicles and to 85 kW throttle drives of technological equipment with energy saving systems by using pumps with automatic regulators of change of working volume. It has been established that in the pumps for of transmissions the ratio of mass to power is reduced three times.Originality. Graphic dependences of power, supply and torque of standard size series on the working volume of axial-piston pumps and hydraulic motors of the domestic enterprise "Hydrosila" for volumetric hydraulic transmissions and technological equipment of aerodrome and aircraft maintenance facilities are constructed. Practical value. The possibility of a rational selection of axial-piston domestic hydraulic machines for the development of hydraulic drives for airfields and aircraft.

Experimental and Computational Investigation of Flow Fields using Accelerated Erosion Test Ring (AETR)

The erosion of the blades of hydraulic pumps and turbines, caused due to the water that has enormous suspended particles and erosive agents, is a severe global challenge among scientists and engineers. In the present work, an attempt has been made to compute the extent of erosion caused by water when it passes through devices like hydraulic machines, centrifugal pumps and turbines. Experimental and computational techniques using pitched turbine blades with 45o with the horizontal plane under down pumping condition is employed for investigation of the suspension phenomena for calculating erosion wear by sand suspended in water in river, canal on turbine, pump blades. An experimental set up, named as Accelerated Erosion Test Rig (AETR), is developed through dimensional analysis. For experimental analysis, the sand particle size and propeller dimensions were varied while running the propeller at different speeds. Experimental results revealed that the propeller speed must be maintained at an optimum value, preferably lower speeds, to ensure maximum lifting of impurities and sand particles from the base of the cylinder.

Ways to ensure the efficiency and improvement the efficiency of hydraulic machines

In this paper, the methods of designing hydraulic drives with minimal energy losses are considered. As well as ways to reduce energy losses in hydraulic systems. The importance of the work is due to the fact that methods have been proposed to improve the reliability and environmental friendliness of the hydraulic drive.

Development of a Methodology for Model Testing of Utor Welded Joints of a Vertical Cylindrical Tank

The methodology of laboratory modeling of the loading of utor welded joint of the tank is presented. The methodology is based on testing of the special design sample. It allows under uniaxial tension on the typical servo-hydraulic machines to reproduce in the zone of a utor welded joint the combined action of bending and shear forces, similar to that which occurs during the operation of a vertical cylindrical tank. To assess the distribution of the stress-strain state in the proposed design of the sample under its loading, the finite element modeling was performed in the ANSYS software package. It showed the fundamental correspondence of the stress distribution in the zone of the utor node in the sample and in the real tank. The experimental studies consisted in carrying out tests for the durability of a series of 16 samples loaded with the maximum force in the cycle, causing the calculated stresses in the zone of the welded utor node in the range of 100–200 % from the maximum permissible ones. The obtained results showed that the maximum loaded zone, where the destruction of the samples occurred, is the near-seam zone of the utor welded joint on the inside of the tank. This corresponds to the statistics of the real tank failures. It is established that the developed methodology ensures the possibility of carrying out correct resource tests of the tank utor welded joints. It is also possible to vary the stress-strain state scheme within a wide range in the area of the utor welded joint by changing the design parameters of the test sample. In compliance with the regulated welding technologies and the absence of unacceptable defects in the welded joint, the utor node has a high resource, which significantly exceeding 50 years of the tank operation.

Numerical Assessment of Cavitation Erosion Risk in a Commercial Water-Jet Pump

In this paper, the risk of cavitation erosion is assessed in a commercial water-jet pump using a recently developed numerical erosion assessment method by Arabnejad et al. [1]. This assessment is performed for two flow conditions with different cavitation erosion risk according to the experimental paint tests and the high erosion risk areas identified by the method are compared with the experimental results. This comparison shows that the applied method is capable of both identifying the regions of high erosion risk and also capturing the difference between the cavitation erosion risk in the two studied conditions. The latter capability of the numerical assessment method, which has not been reported in the literature for other published methods, is one step forward toward the application of the method in the design process of hydraulic machines. Furthermore, the numerical results are analysed to explain the reasons for different erosion risk in the two conditions. This analysis reveals that this difference is mostly related to the stronger flow non-uniformities entering the rotor in the most erosive condition. Using the numerical results, one reason behind these stronger nonuniformities is identified to be the stronger bursting of vortices shed from the shaft in the most erosive condition.