Flow characteristics of variable hydraulic transformer

A new kind of hydraulic transformer, called variable hydraulic transformer(VHT), is proposed to control its load flow rate. The hydraulic transformer evolves from a pressure transducer to a power transducer. The flow characteristics of VHT, such as its instantaneous flow rates, average flow rates, and flow pulsations in the ports, are investigated. Matlab software is used to simulate and calculate. There are five controlled angles of the port plate that can help to define the flow characteristics of VHT. The relationships between the flow characteristics and the structure in VHT are shown. Also, the plus-minus change of the average flow rates and the continuity of the instantaneous flow rates in the ports are presented. The results demonstrate the performance laws of VHT when the controlled angles of the port plate and of the swash plate change. The results also reveal that the special principle of the flow pulsation in the ports and the jump points of the instantaneous curves are the two basic causes of its loud noise, and that the control angles of the port plate and the swash plate and the pressures in the ports are the three key factors of the noise.

Effect of plunger number on hydraulic transformer's flow pulsation rate

In order to supply theoretical guidance to hydraulic transformer's design and application,the effect of the number of plungers in hydraulic transformer on its flow characteristic is analyzed,theoretical analysis and simulation are done on hydraulic transformer's flow characteristic when the number of plungers is different.Based on the working principle of swash plate piston hydraulic components,mathematical models of instantaneous flow and flow pulsation rate are built,and simulation study is done with MATLAB.As a result,the effect is found,and some conclusions worth referring to are obtained.

Research on characteristics of integrated type hydraulic transformer's control angle

In order to realize remote control of hydraulic transformers and improve the control precision of the pressure ratio,an integrated type electric hydraulic servo hydraulic transformer is proposed in this paper,a mathematical model is built and simulation of electro-hydraulic servo integrated hydraulic transformer's control angle is carried out,the principle prototype of the transformer is designed and manufactured,and experimental study is carried out on the experimental bench. The experimental results verify the correctness of the mathematical model. The results show that electro hydraulic servo control can improve the accuracy and dynamic response speed of control angle,which provides a reference for the further research of the hydraulic transformers.

Research on buffer structure and flow field simulation of swash plate plunger type hydraulic transformer

In order to solve the problem of excessive noise and vibration during the operation of the hydraulic transformer,an optimization method of valve plate damping hole structure is proposed to alleviate the phenomenon of pressure shock.Firstly,the mathematical model of oil pressure gradient in the plunger cavity is established,and the incremental equation of pressure change is derived.Secondly,a kind of buffering structure is proposed,the corresponding relationship between the pressure change and the envelopment angle of the buffering hole and the aperture size is determined by analyzing the oil pressure change curve in the plunger cavity.Finally,the flow field models with buffering holes are established,and the transient simulation of the pressure change process under the optimal solution is carried out with ANSYS software and the flow field pressure distribution contours are obtained.Through the analysis of simulation results,it is concluded that the optimal envelope angle of the three buffer holes ofA-T-B-Ais 5°,and the optimal aperture is 1.8 mm,1.6 mm,and 1.7 mm,respectively.The buffer hole can achieve a better-buffering effect in the range of variable pressure angle[0°,101°].The buffer hole structure can effectively alleviate the pressure shock and reduce the noise level,which lays a foundation for the design and theoretical research of hydraulic transformers.

Simulation and Experimental Study on Influence of Multi⁃port Integrated Hydraulic Transformer Port Number on Transformer Ratio Characteristics

The integrated hydraulic transformer has a compact structure and no throttling loss in the process of pressure regulation.It is widely used in the common pressure rail hydrostatic transmission system.The integrated hydraulic transformer is realized by designing more than three ports on the distribution plate,and the voltage transformation characteristics of the integrated hydraulic transformer with different port numbers are different.In this paper,the influence of port number on the pressure ratio of integrated hydraulic transformer was studied,and the pressure ratio characteristics of 3⁃ports,4⁃ports,and 5⁃ports integrated hydraulic transformer were obtained,and an experimental platform was built for experimental verification,which shows that the simulation results are consistent with the experimental results and provides a theoretical basis for the design of integrated hydraulic transformer.

Simulation of a vehicle hydraulic propulsion system

The characteristics of a hybrid hydraulic vehicle driven by the hydraulic common rail propulsion system with a hydraulic free-piston engine and a hydraulic transformer were studied.A mathematical model of the propulsion system was established and a control method of the propulsion system was proposed.Extensive simulation results of hybrid hydraulic vehicles with the hydraulic common rail propulsion system were presented.The hydraulic common rail propulsion system achieved the switch power control and the constant power propulsion.The control method based on the propulsion,break and speed limit requirement was verified.Our results showed that the hydraulic common rail propulsion system gained an ideal acceleration process.

Transient Mould Friction Based on the Wavelet Theory

The mould friction is an important parameter reflecting the initial shell and mould lubrication conditions.The research of mould friction is very important to the optimization and developing of continuous casting.The measured mould friction under hydraulic oscillation mode was researched with wavelet analysis to reveal its time-frequency characteristics.Firstly,the mould friction signals under different production conditions were monitored and the mould friction was calculated.Then,mother wavelet function was selected from three wavelet functions which were chosen preliminary according to the characteristics of mould friction and wavelet theory.Through wavelet transformation,mould friction signal was projected onto the wavelet domain,and the time-frequency characteristics of mould friction under different production conditions were obtained and discussed.Mould friction under different production conditions such as different oscillation mode,casting speed fluctuation,increasing and decreasing stage of casting speed and breakout occurrence was reported in detail in the wavelet time-frequency maps.The characteristics of mould friction were reflected well through wavelet transformation which proved that wavelet analysis had a good feasibility for mould friction study and can further reveal the nature of mould friction.