Showing papers on "Gear pump published in 2022"

Experimental Study on the Internal Pressure Pulsation Characteristics of a Bidirectional Axial Flow Pump Operating in Forward and Reverse Directions

Abstract: A bidirectional axial flow pump can realize bidirectional pumping, which has a wide application prospect in coastal low-head pumping stations and water jet propulsion systems. In this paper, a typical bidirectional axial flow pump is taken as the research object, and the hydraulic model of the bidirectional axial flow pump is manufactured. The hydrodynamic characteristics of the bidirectional axial flow pump are tested on the high-precision hydraulic mechanical test bench, including the positive and negative directions. In the experiment, multiple pressure pulsation monitoring points were arranged in the impeller chamber, and the pressure fluctuations in the pump under a total of 42 flow conditions were measured by a micro pressure pulsation sensor, involving 21 working conditions of forward operation and 21 working conditions of reverse operation. According to the experimental results, the hydrodynamic characteristics, especially the pressure pulsation characteristics in the pump, of the two-way axial flow pump under positive and negative operation are comprehensively compared and analyzed, and the energy characteristics and the propagation law of pressure pulsation of the two-way axial flow pump under positive and negative operation are revealed. The research results provide an important reference for the safe and stable operation of coastal bidirectional axial flow pump stations.

An Investigation of the Vibration Modes of an External Gear Pump through Experiments and Numerical Modeling

Abstract: This paper presents an experimental and numerical modal analysis for an external gear pump considering its mounting on a test rig in a laboratory setting. Most of the previous studies on experimental modal analysis (EMA) of hydraulic pumps focused on the modal frequencies to allow model validation. However, the mode shapes of pump bodies have not extensively been discussed. Furthermore, the nature of the pump components assembly and mounting poses some modeling challenges, such as the uncertain material properties of each component, the behavior of the bolted joints, and some critical modeling boundary conditions related to pump mounting. In this regard, the experimentally obtained vibration modes of a reference pump using the least-square complex exponential (LSCE) method are analyzed with an emphasis on the characteristics of the mode shapes. Then, simple modeling strategies are proposed and validated by performing the analysis from the component level to the full assembly. As a result, the mode shapes are categorized depending on the type of motions that the modes exhibit. It is observed that the pump casing does not show any substantial deformation but is close to the rigid body motion. Moreover, without considerably increasing model complexities, the proposed numerical approach provides reasonable accuracy with average errors in modal frequencies of 6%, as well as good agreement in terms of mode shapes. The vibration reduction strategy is briefly discussed based on the measured mode shapes, and the proposed modeling approaches can be useful to study external gear pumps with minimal model complexities yet allowing reasonable result accuracy.

Study on Health Indicator Construction and Health Status Evaluation of Hydraulic Pumps Based on LSTM–VAE

Abstract: This paper addresses the difficulty of evaluating operating status in widely used gear pumps. A method for constructing hydraulic pump health indicators and evaluating health status is proposed based on LSTM–VAE. In this study, the vibration signal data source of gear pumps was assessed in the accelerated life test. Firstly, the normalized feature vectors of the whole-life operation data of gear pumps were extracted by wavelet packet decomposition and amplitude feature extraction. Combining an LSTM algorithm with a VAE algorithm, a method for constructing hydraulic pump health indicators based on LSTM–VAE is proposed. By learning the feature vectors of gear pumps in varying health conditions, a one-dimensional HI curve of the gear pumps was obtained. Then, LSTM was used to predict the HI curve of gear pumps. According to the volume efficiency of the gear pumps, the health status of gear pumps is divided into four states: health, sub-health, deterioration, and failure. The health status of the hydraulic pump is accurately evaluated by the health indicator. Finally, the proposed method is compared with the traditional method based on feature selection and PCA dimensionality reduction. The health indicator constructed by the method proposed in this paper is superior to the traditional method in terms of tendency, robustness, and monotonicity, which proves the effectiveness of the method proposed in this paper.

Research on Prediction Method of Gear Pump Remaining Useful Life Based on DCAE and Bi-LSTM

Abstract: As a hydraulic pump is the power source of a hydraulic system, predicting its remaining useful life (RUL) can effectively improve the operating efficiency of the hydraulic system and reduce the incidence of failure. This paper presents a scheme for predicting the RUL of a hydraulic pump (gear pump) through a combination of a deep convolutional autoencoder (DCAE) and a bidirectional long short-term memory (Bi-LSTM) network. The vibration data were characterized by the DCAE, and a health indicator (HI) was constructed and modeled to determine the degradation state of the gear pump. The DCAE is a typical symmetric neural network, which can effectively extract characteristics from the data by using the symmetry of the encoding network and decoding network. After processing the original vibration data segment, health indicators were entered as a label into the RUL prediction model based on the Bi-LSTM network, and model training was carried out to achieve the RUL prediction of the gear pump. To verify the validity of the methodology, a gear pump accelerated life experiment was carried out, and whole life cycle data were obtained for method validation. The results show that the constructed HI can effectively characterize the degenerative state of the gear pump, and the proposed RUL prediction method can effectively predict the degeneration trend of the gear pump.

Hydraulic Tests of the PZ0 Gear Micropump and the Importance Rank of Its Design and Operating Parameters

Abstract: This article presents the results of hydraulic tests performed for a prototype gear micropump of a new design. The development of modern hydraulic systems is following two directions: the integration of hydraulic and electronic engineering and a reduction in the mass and the dimensions of the system. The scope of this research involved identifying static characteristics of the prototype gear pump, i.e., its efficiency, torque and power. The tests were performed for PZ0 pumps with the following specific deliveries (which are their design parameters), 0.25 cm3/rev, 0.315 cm3/rev, 0.5 cm3/rev, 0.8 cm3/rev, and 1.0 cm3/rev—with two different types of hydraulic oils, Azolla ZS 22 and HL 68. The operating parameters included the rotational speed, the discharge pressure and the flow rate. The obtained research results suggest an application of the decision tree induction-based classification method for identifying the most important design and operating parameters and their values influencing total efficiency. In addition, the article investigates the influence of rotational speed and specific delivery on total efficiency. The total efficiency translates indirectly into the energy consumption of the solution. The criterion of energy consumption is a key parameter for ecological and economical reasons, related mainly to future operating costs.

Analysis of the influence of hydraulic fluid quality on external gear pump performance

Abstract: The basis of every hydraulic system is based on energy transformations, which are realized through hydraulic working fluid. Hydraulic oils are certainly subject to changes within their structure, meaning the basic characteristics and parameters of hydraulic oil, such as density, viscosity, humidity. The oils that are exploited are exposed to the process of degradation, which largely leads to significantly poorer quality of hydraulic fluid. The paper deals with the influence of changes in the characteristics of the hydraulic fluid on the hydraulic operating parameters of the gear pump installed on the hydraulic press. The parameters refer to pressure, flow, and temperature, as well as the quality of hydraulic oil, which affects the volumetric efficiency of the pump, and the results presented in the conclusion are based on the measured values of parameters before and after corrective measures. The control of parameters aims to increase the efficiency and reliability of the hydraulic system, a way of modern detection of deviations of parameters from standard, required values.

Analysis and Experimental Research on Efficiency Characteristics of a Deep-Sea Hydraulic Power Source

Abstract: The deep-sea environment has the characteristics of high pressure and low temperature. In addition to the extremely high requirements on the structural reliability, the ultra-high ambient pressure also has a great impact on the working characteristics of the hydraulic source. In this paper, the efficiency characteristics of a deep-sea hydraulic source are studied in the full-ocean-depth pressure range. According to the power transfer process, the efficiency of the deep-sea motor, gear pump and hydraulic circuit is analyzed. In so doing, the oil friction loss of the motor rotor, the internal leakage of the gear pump, the viscous friction loss of the hydraulic system, etc., are calculated. Then, simulating the deep-sea high-pressure environment by the pressure cylinder, the output characteristics and corresponding input power of the prototype are measured. By analyzing the experimental data, the efficiency characteristic curve of the hydraulic source prototype, changing with the ambient pressure, is obtained. The experimental and calculation results show that, with the increase of ambient pressure, the system efficiency of the hydraulic source prototype increases first and then decreases.

New Method to Determine the Dynamic Fluid Flow Rate at the Gear Pump Outlet

Abstract: External gear pumps are among the most popular fluid power positive displacement pumps; however, they often suffer from excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power systems, it is necessary to give a physically sound method of analyzing the operation of a volumetric pump. The analysis of the basic approach used by the majority of researchers for calculating the flow rate of a gear pump by E.M. Yudin is presented. The article presents a new method for analyzing the operation of volumetric pumps. The method is suitable for the pumps whose dynamic characteristics should be considered according to the model of an equivalent source of flow fluctuations by V.P. Shorin. The method is based on wave theory, the method of hydrodynamic analogies and the impedance method, where the pump is considered according to the model in lumped parameters. The method consists in determining the pressure pulsations at the pump output in bench systems with known dynamic characteristics and recalculating the pump flow rate in pulsations. Computational dynamic models of bench systems in lumped parameters are proposed for subsequent use in dynamic tests of pumps in the form of equivalent sources of fluid flow fluctuations. We give recommendations for the formation of test bench systems with a throttle, a cavity and a pipeline at the pump output. Using the example of an external gear pump with a working volume of 14 cm3/rev, the implementation of the proposed method is considered. The pump’s own pulsation characteristic of the flow rate in a bench system with an “infinitely long” pipeline along two harmonic components of the spectrum is determined, and a test of the method based on the method of determining the instantaneous flow rate by R.N. Starobinskiy is proposed. It is shown that, according to the proposed method and the method of R.N. Starobinskiy, the divergence of the amplitudes of flow pulsations does not exceed (5–10)%. The high degree of coincidence of the results confirms that the external gear pump in question should be considered according to the equivalent source of flow fluctuations model.

Modeling the Meshing Procedure of the External Gear Fuel Pump Using a CFD Tool

Abstract: In modern aircraft engine technology, there is a tendency to replace the mechanical drive of external gear fuel pumps with an electric one. This significantly reduces the integral energy consumption for pumping fuel (kerosene). On the other hand, in order to reduce the dimensions of the structure, it is reasonable to increase the rotation speed of the pumping unit gears. The above considerations make it advisable to study the problems that may arise in the design of pumping units. Analysis of the existing designs of external gear fuel pumps shows that the flow processes in the meshing zone have a significant impact on the pump performance and lifetime. Incorrect truss plate geometry and the compensation system lead to an increase in the velocities when opening and closing the cavity in the meshing zone, which causes intense cavitation. To understand the causes and factors which influence this phenomenon, it is necessary to study the fluid flow behavior in the meshing zone gaps. High-speed cameras are used to experimentally study the flow behavior. However, this approach gives only a qualitative result but does not allow for determining the absolute values of pressure and load in terms of the angle of rotation. Nevertheless, high-speed surveying can be used as a basis for fluid flow model verification. In this paper, the model of the fluid flow in a high-pressure external gear pump was proposed. The verification of the simulation results for HDZ 46 HLP 68 oil operation was carried out according to the results of experimental data visualization. The influence of rotation speed on the position of cavitation zones was revealed and confirmed by operational data. The analysis of the flow process in meshing for kerosene as a working fluid was carried out.

Energy-Efficient Electro-Hydraulic Power Source Driven by Variable-Speed Motor

Abstract: Hydraulic systems are widely used in industry due to their small size-to-power ratios and their ability to produce very large linear force and torque. In traditional hydraulic systems, a variable pump driven by an electric motor is often used as power source. In these systems, the electro-hydraulic power source always operates at its rated speed, causing lots of noise and low energy consumption, especially in no-load and light-load conditions. These problems can be solved by changing the speed of the electric motor according to the load state of the electro-hydraulic power source. In order to improve the energy efficiency of the electro-hydraulic power source and realize pressure and flow control on the basis of low cost, this paper presents the power-source structure of a variable-displacement pressure-compensated pump driven by a variable-speed electric motor; this controls the flow by adjusting the electric motor speed and controls the pressure with the variable-displacement pressure-compensated pump. However, for the variable-speed system, the starting of the electric motor with a load is relatively slow; this makes it difficult to meet the demand of flow control, and will also have a great impact on the power grid. To address these problems, a hydraulic accumulator is introduced to the inlet port of the hydraulic pump to assist in starting the pump. This method can realize the combined control of pressure, flow and power, and has high energy efficiency. This research uses experiments to verify the feasibility of the scheme, and the results show that the starting periods of the power source can be shortened from 2.8 s to 0.7 s when the load pressure is about 18 MPa. Furthermore, regarding maintaining pressure without flow outputs, the energy consumption of the designed power source can be reduced by almost 30% compared with a pure variable-displacement power source.

An investigation of the impact of pump deformations on circumferential gap height as a factor influencing volumetric efficiency of external gear pumps

Abstract: Gear pumps are widely used in transport machines not only in hydraulic drive systems, but also in lubrication and fuel systems. A positive displacement pump converts mechanical energy into pressure energy stored in the liquid, which it transports to the hydraulic cylinder or motor. The efficiency of this process depends on the efficiency of the system components, including the efficiency of the pump, which depends on the amount of internal leakage through the gaps between the high and low pressure sides. The larger the gaps, the lower the volumetric efficiency. This article presents an investigations of impact of pump deformations on circumferential gap height. The article presents a three-dimensional model of an external gear pump using Finite Element Method (FEM) during operating conditions. The model reflects pumping operation at discharge pressures up to 32 MPa and it was validated against strain measurements of pump casing. The simulation results indicate that the pump casing becomes deformed due to pressure, causing a significant increase in the height of the circumferential gap. The increase of the discharge pressure from 8 to 32 MPa causes more than twofold local increase in the height of the circumferential gap. The obtained results indicate that for the correct modelling of the flow generated by gear pumps, it is necessary to consider the change in the size of the gaps resulting from the deformation of the pump.

Wear performance analysis and simulation of external gear pump

Abstract: As a kind of hydraulic power component, the external gear pump determines the performance of the entire hydraulic system. Gear pumps are subjected to various degradation such as wear which deteriorate the performance of the gear pump. The purpose of this research is to analyze the wear degradation of external gear pump under various operating conditions like speed, pressure and radial gap between gear tooth and casing. As wear affect the performance of gear pump, optimization of operating conditions on the performance of gear pump was studied. External gear pump is modelled in Fusion 360, and ANSYS CFD analysis was used for the simulation of volumetric efficiency under various operating conditions. The pump was simulated at different operating speeds and radial wear gaps.

Analysis of straight conjugate internal gear pump through numerical modeling and experimental validation

Abstract: As a medium and low pressure gear machine without automatic compensation structure for axial and radial clearances, the friction pairs in the straight conjugate internal gear pumps (SCIGPs) depend on the fixed small clearances to seal, lubricate and transfer the force. The oil film design of the friction pairs has become an important part of gear pump design. However, there has never been a publicly published research on the oil film design of the SCIGP in past literature. This paper applies orthogonal test to the oil film design of the SCIGP for the first time to determine the best working clearances. With this goal, the paper first provides the mathematical models for analyzing the internal leakage flow and the viscous friction loss, which elucidate the relationships between the leakage and the friction loss with working conditions. After that, the orthogonal test scheme for numerical simulation was designed on the basis of determining the range of oil film thickness. The paper also propounds the viewpoints of using the range-method to estimate the primary and secondary relationship of factors and determining the optimal combination according to the test target. Based on this concept, the main factors affecting the target are procured and the optimal working clearances of the friction pairs are determined. For the purpose of verifying the model, the redesigned prototype was tested and compared with the simulation results. The results validate the applicability of the simulation model and the correctness of the simulation method. Finally, the paper summarizes the ways to improve the total efficiency and the working conditions at the highest efficiency.

Application of gear hydraulic machines in the composition of hydrostatic transmissions

Abstract: Hydraulic machines serve either to impart energy to the fluid flowing through them, or to obtain energy from the fluid for its further useful use. The number of hydraulic machines used in the national economy is increasing annually, due to the fact that, in comparison with electric motors, they have smaller overall dimensions and weight, and also have a higher ratio of torque on the output shaft to the moment of inertia of the rotor. In agriculture, hydraulic machines are widely used in crop production. Through the use of hydraulics and automation, the development of complex mechanization of production processes is carried out, which provides for the development of machines of increased power and reliability. Also, the use of hydraulic machines allows you to relieve the structure of rigid mechanical connections and allows a wide range of adjustment of the unit operation. The most widely used today are two types of hydraulic machines - piston and gear. The use of hydraulic piston machines places high demands on the degree of purification and quality of transmission oil, as well as on the qualifications of technical personnel to ensure quality maintenance. Gear hydraulic machines are less demanding on the purity of the working fluid, as well as simplicity in design, are quite reliable, have a low cost price and a wide range of rotational speeds, in addition, they are able to create a relatively high pressure with low weight. The overall efficiency of gear hydraulic machines, which is 90%, is slightly inferior to that of piston hydraulic machines, which reaches 93%, respectively. The given characteristics of gear hydraulic machines allow us to consider them, taking into account modern design features, as a power basis for a hydrostatic transmission, with a limitation in power of application.

FEM Strength Analysis of Circumferential Compensation with Integrated Lips in Gear Pumps

Abstract: Currently, gear pumps are developed with a aim to increase their efficiency, reduce internal leaks, and increase their working pressures. This development direction requires new solutions which would compensate backlash while ensuring an optimal size of the gaps for the entire range of working pressures. One of the solutions intended to meet this demand is to design circumferential compensation with the so-called integrated lips. The presented backlash compensation method is the result of research performed as part of a project named Designing High-Pressure Gear Pumps. The project was granted funding under path A of the Applied Research Program, contract No. PBS3/A6/22/2015. The research works were performed in the Laboratory of Hydraulic Drives and Vibroacoustics of Machines at Wrocław University of Science and Technology, and in cooperation with Hydrotor SA.

Determination of the dynamic characteristics of a gear pump by the load variation method using special bench systems

Abstract: Introduction . Some of the major factors in the occurrence of vibration of units, causing fatigue failure of the housings of elements, pipelines, and failure of pump elements, are pulsations of the working medium in the hydraulic systems of machine tools, fuel feed systems of aircraft engines and liquid-propellant engine supply. This study aimed at the implementation of a method for determining the dynamic characteristics of a volumetric pump using special bench systems, and the comparison of the calculation results to the experimental data. The stages of calculating the dynamic characteristics of a volumetric pump were described, taking into account the pre-developed special bench systems on the example of an external gear pump with a capacity of 14 cm3 /rev. The implementation of V. P. Shorin's load variation method using special bench systems developed by the authors with predetermined dynamic characteristics was shown. The main stages of the methodology for determining the dynamic characteristics of a gear pump were described. Materials and Methods . Methods of spectral analysis of pulsating pressure were applied in the work. Pulsations of fluid flow at the pump outlet were determined using the impedance method, the method of load variation, and special bench systems. Results . The paper implemented a technique for determining the dynamic characteristics of a gear pump in the drive shaft speed range of 500-2500 rpm for four harmonic components of the vibration spectrum in a wide range of dynamic loads (from inertial to capacitive nature). The bench systems yielding the calculation of the dynamic characteristics of the pump with a minimum error based on the condition of matching the dynamic load and the source of vibrations were analyzed. The developed approach to the evaluation of the dynamic characteristics of the pump was verified through comparing the calculated and experimental data of pressure pulsations in the bench systems with choke, cavity and an extended pipeline at the pump outlet. Discussion and Conclusions . The method for determining the dynamic characteristics of a volumetric pump was implemented using special bench systems developed by the authors. The research results show that the gear pump under study can be considered as an independent source of flow fluctuations, for which the deviation of its own dynamic characteristics from the average values does not exceed 10% for the first harmonic component.

Modern investigation of rod well pumps

Abstract: At present, rod deep pumps are the basis of equipment widely used in the oilfield industry. These pumps are underground equipment of the rocking machine. Due to its wide application, solving problems during its operation is one of the most important and topical issues. Depending on the main characteristic features, oil well depth pumps are manufactured in various sizes and shapes. The research work studied the influence of sand on the operation of the depth pump, the accumulation of a large amount of gases at the inlet of the pump, wear on the working surfaces of the plunger, cylinder and valves, etc. Keywords: rod well pumps, wear resistance, underground repair of wells, operational indicators, refusals of pump elements.

Research on Seawater Hydraulic Internal Ball Gear Pump

Abstract: With high demands for novel technologies in the marine mechatronic instrumentality and the limitations of the present hydraulic pumps, a novel bidirectional seawater hydraulic internal ball gear pump is proposed to accomplish the function of fluid power transmission and control. The proposed hydraulic pump can be used for hydraulic buoyancy control systems of underwater vehicles and different marine mechatronic equipment. In this paper, the model, the meshing and the flow characteristics of the internal ball gear pump are developed. The radial unbalance force of the pump, leakage, and flow pulsation are also analyzed. The new type of eccentric shaft-hole rotary sealing designed in this paper can eliminate axial leakage and is expected to improve volumetric efficiency, working pressure, and power density. Simulation and experimental results show that: (1) by using the concave/convex ball gears rather than the existing gears, the concave ball gear drives the convex ball ring to rotate, realizing energy transfer and conversion; (2) compared with the water hydraulic internal gear pump, the internal ball gear pump has excellent performance. Experimental results also show that when the speed is 1500 rpm, the maximum operating pressure can reach 7 MPa. At 2 MPa, its volumetric efficiency and flow can reach 75% and 0.189L/min, respectively. The outcomes of this study show that the proposed seawater hydraulic internal ball gear pump is effective and has a lot of potential.

Stabilization of the radial clear in the pumping assembly of the supply pump improvement by improving the structure of the slide bearing bushing

Abstract: The performance of axial-piston hydraulic feed pumps depends on the technical condition of the coupling parts that form a radial gap in the pumping unit of the pump. The dynamics of its growth is largely due to the technical condition of parts that form a radial gap in the plain bearings of the pumping pump assembly: «drive shaft pin - bushing hole», «driven axle pin - bushing hole». Stabilization of a radial backlash in sliding bearings is possible by carrying out constructive improvement of the plug which will provide reduction of a contact angle of surfaces of friction of details in couplings. The aim of the work is to ensure the stabilization of the radial clearance in the pumping unit of the feed pump by developing constructive measures to reduce wear of parts in its plain bearings. From the analysis of the operating conditions of the plain bearing it is established that the reduction of the friction force is possible due to the reduction of the contour pressures and the increase of the area of liquid friction between the surfaces of the parts. Providing such conditions is possible by using combined bushings, which consist of working and guide bushings, between which is installed an elastic damping element in the spherical channels of which are additional compensation springs, which are placed in a circle through . The reduction of the friction force when using a combined sleeve with compensating springs is explained by the formation of the deformation component of the friction force at the vertices of the microroughness of the sleeve surface, as the spring elasticity is 4% less than the modulus of elasticity of the sleeve material. The lower value of the moment of friction forces at the end of the test is due to the constant absorption of vibration loads by the elastic damping element, the elasticity of which is 2% less than the modulus of elasticity of the sleeve material, which also reduces the contact area. The total less wear of the experimental friction pair is due to the reduction of the contact area of the shaft with the sleeve in the area of maximum values of friction forces.

Increasing gear Pump Hydraulic Systems of Car and Tractor Machinery Durability by Decreasing Details Attrition, Which Create Radial Clearance

Abstract: The research goal is the determination of rational radial clearance, with what details, which create radial clearance, attrition will be minimal and eventually provides gear pump hydraulic systems of car and tractor machinery durability increasing. Research gives the results of the dependence of working liquid losses through radial clearance. Determined main parameters, which have an influence on them, and conditions due to which working liquid losses will be minimal, which corresponds to the rational value of radial clearance and provides decreasing of details attrition, which creates radial clearance. Were found as the main parameters, which allow managing working liquid losses through radial clearances. They consist of gear tooth tops width, gear rotation frequency, and outer gear radius. Offered a new conditions determination method, in which working liquid losses through radial clearances will be minimal. Mentioned models include the presence of pressurized and frictioned losses compounds. Was found that increasing gear pump durability is able due to gears processing and further gear pump assembling made with guaranteed radial clearance in connection «body - gears» details, which excludes initial attrition of gear pump body in time of its enabling. Increasing radial clearance to sizes, in which abrasive parts of any sizes are able to frequently walk through avoiding body walls and gear teeth tops, helps to prevent the abrasive attrition phenomenon. Rational radial clearance provides free passage for almost all abrasive parts, which increases gear pump durability. Rational radial clearance determination allows for increasing the efficiency of technology of gear pump manufacturing by rationalizing tolerances for gears manufacturing, which allows for increasing gear pump durability.

The Influence of Gear Pump Supply Fluctuations on Dynamic Processes in a Hydraulic Drive with a Long Pressure Hydraulic Line

Abstract: It is known that gear hydraulic pumps are characterized by significant supply pulsations, which can reach 30 % of its average value. Supply pulsations under certain conditions are caused by pressure fluctuations in pressure hydraulic lines and hydraulic units, which is a negative phenomenon, as it reduces the resource of their work. In this article, using the method of simulation modeling in the MATLAB Simulink environment, a study of a hydraulic drive of translational motion with a gear pump and a long pressure hydraulic line was carried out to identify the influence of drive parameters on the nature of dynamic processes caused by a sudden change in supply and oscillatory changes (pulsations) of pump supply relative to the possible occurrence of resonance phenomena in the pressure hydraulic line and in the drive as a whole. The effect of the length and diameter of the pipeline of the pressure hydraulic line, as well as the reduced modulus of elasticity of the pressure hydraulic line on the frequency and amplitude of resonant oscillations was studied. Research was carried out in a sufficiently wide range of frequencies of rotation of the drive shaft of the gear pump. This corresponds to the real operating conditions of mobile machines in which the pump of the hydraulic system is connected to the power take-off shaft of the internal combustion engine. As a result of research, it was established that noticeable resonance phenomena occur at relatively low frequencies of rotation of the pump shaft. It was also established that an increase in the length of the pressure hydraulic line, a decrease in the diameter of the pipeline and the reduced modulus of elasticity reduce the frequency of resonant oscillations. With an increase in the length of the pressure hydraulic line and an increase in the reduced modulus of elasticity, the amplitude of resonant oscillations increases, and with a decrease in the diameter of the pipeline, it decreases.

Increasing the Supply of Gear Pumps for Vehicles and Agricultural Machinery

Abstract: The purpose of this publication is to develop a mathematical model of the gear pump, which will develop a method for calculating the gearing of the pump with increased specific feed. One of the promising areas for further development of the gear pump is to increase its supply. And if the design of the pump with high flow is solved by increasing its dimensions - is an engineering problem, then increase the flow while maintaining its dimensions, ie increase the specific flow and specific power of the pump is a rather difficult scientific problem. Using the dimensionless GCUR - it is possible to estimate easily advantages of gearing of any two pairs of gear wheels on giving.From the dependences we see that the GCUR does not depend on the gearing module, which is an unexpected result, because it is known that the module plays a major role in increasing the supply of the pump. It is known that the gearing module plays the role of a scale factor, that is, with the growth of the module increases the RON, but the overall dimensions and weight of the pump increase. Therefore, increasing the RON by increasing the gearing module has its limitations, moreover, this method of increasing the feed is not able to increase the specific feed, and therefore does not increase the technical level of the pump on this parameter The results of the above studies, as well as production experience, show that the most significant effect on the volume utilization of the gear rings has the number of teeth of the pump gears. At the same time, reducing the number of teeth helps to increase the utilization rate of the gear rings. The minimum number of gear teeth z = 8 currently in use in the industry is teeth, which is the classic number of teeth of pump gears with an average value of working volume –q = 32…50 см3.

Determination of Hydrodynamic Power Losses in a Gearing

Abstract: Abstract Despite the relatively numerous experimental studies, there are few published works on the topic of development of mathematical models that describe the hydrodynamic processes in gears. There is no generic analytical model that integrates all types of losses. The purpose of this work is to develop a modern generalised methodology for calculating the hydrodynamic power losses of high-speed gears. For each gear, partially or fully immersed into an oil bath, the power spent to overcome the hydromechanical resistance can be represented as the sum of the following: the Coriolis force moment arising from the radial movement of the oil in the tooth spaces of the rotating gear, the viscous friction forces moment on the periphery of the gear addendums in the oil bath and the viscous friction forces moment at the face of the gear in the oil bath. The hydrodynamic power losses due to the Coriolis force action, viscosity friction losses at the periphery of the gear and the viscosity friction at the face of the gear (both turbulent and laminar modes) were observed separately. From the mathematical simulation of the rotation processes when the gear is immersed into the oil bath, an analytical dependence was obtained. It allows predicting the influence of the geometrical parameters of the gearing on the hydrodynamic power losses. Analysis of the calculation results of the power losses due to the action of hydraulic resistance forces and results from experimental studies is provided for several gears with different hydromechanical parameters. The proposed method of calculating power loss due to hydromechanical resistance of the oil bath to the rotation of the gear gave results that were close to the experimental data. Acceptable coincidence of theoretical and experimental results allows recommending the received analytical dependencies for practical calculations of high-speed gears.

Gaseous cavitation characteristics of high-speed hydraulic electric motor-pump based on centrifugal pressurization: A numerical study

Abstract: Hydraulic electric motor-pump is an integrated hydraulic power unit, raising rotational speed will further increase its power density. However, gaseous cavitation at high speed is the primary problem to be solved. In the present study, a new but simple centrifugal pressurization structure that integrated with the hollow shaft of hydraulic electric motor-pump was proposed to increase the inlet pressure of conjugated straight-line internal gear pump, and then to suppress gaseous cavitation at high speed. The numerical simulation is the main means of this work to investigate the gaseous cavitation characteristics of high-speed hydraulic electric motor-pump. In addition, a common conjugated straight-line internal gear pump model was developed as a reference to evaluate the pressurization effect of centrifugal tubes in terms of gas volume fraction. The simulation results present that compared with the significant increase of the suction chamber pressure of conjugated straight-line internal gear pump due to increasing the inclined angle of centrifugal tubes, the blocking effect of its inside wall to the fluid flow can be ignored. Under the same gas volume fraction in rotating volume, the rotational speed of hydraulic electric motor-pump is much higher than conjugated straight-line internal gear pump due to the pressurization effect of centrifugal tubes. On the premise of no obvious gaseous cavitation of centrifugal tubes, the recommended speed of hydraulic electric motor-pump is up to 13,000 r/min.

Radial Clearance in Gear Pump Hydraulic Systems of Auto and Tractor Machinery Forming Features

Abstract: The research goal is the analysis of the existing radial clearance forming method in gear pump details connection “body – gear teeth”, which provides the minimal size of radial clearance with the low accuracy of manufacturing details and offers another rational method of radial clearance creating. In this research was considered creating radial clearance between body and gears of gear pump hydraulic systems of auto and tractor machinery. The technology of gear pump manufacturing after pump folding provides it's enabling on a special stand in order to disability verification. During the period of enabling, as mentioned before, gear teeth cutting into the body happens with forming a so-called «bed», which must provide a radial clearance seal. Given research results of way of radial gear pump clearance forming influence, which is used in hydraulic systems of auto and tractor machinery, gears cutting in pump body during enabling for technical characteristics. Considered the main advantages and disadvantages of this method, and found, that existed way of radial clearance forming by cutting gear into the body, today does not comply with the requirements for pumps. Using the method of gear cutting negatively impacts the supply rate and pump durability. Offered a new way of radial clearance forming, which consists of getting a minimal radial clearance between gears and body due to more accurate gears manufacturing top diameter. This method does not provide gears cutting into the pump body, which increases pump durability. An effective method of radial clearance forming is more accurate manufacturing and folding pump details. The results of experimental research show that increasing radial clearance to certain sizes does not influence on pump supplying rate significantly.