Research On The Design And Application Of The Electro-hydraulic Flow Distribution Svstem With Large Flow Rate And High Speed

With characteristics of small volume, high power density, simple structure and high reliability, electro-hydraulic distribution system (EHFS) has been extensively applied in chemical fluid machinery, engine valve, digital distribution pump/motor, hydraulic impact machine, etc. With fluid transmission machinery working as the heart of industrial production process, the performance of flow distribution system, to a great extent, affects the stability and energy consumption of the main engines and the industrial processing. Besides, with the development of industrial automatization, the efficiency, lower noise and longer operating life of fluid machinery are endued with higher and higher requirement. The research on flow distribution system has appeared to be extremely urgent and important. How to pass the design of flow distribution system with high performance and efficiency to improve the capability of main engines has become a new highlight in the industry. So far, relevant domestic study on EHFS has been carried out later and most of the mature products in China are imported with high price. It’s difficult to do secondary development for the basic components and technology blockage. So it’ll be conductive to the improvement of relevant technical level in China and better meet market demand by carrying out research on the design of EHFS and developing independent intellectual property products.Based on the structural design, mathematical calculation, digital simulation and experimental study, this paper particularly discusses the flow distribution system with large flow rate and high speed. The influencing factors of action delay are analyzed by establishing the modeling of electro-hydraulic actuator. The design approach of electro-hydraulic actuator with high response is presented. New actuator structures including the dual high speed on/off valves parallel type and the pilot type are adopted based on the principle of flow rate improvement. The pilot electro-hydraulic actuator has a typical on/off time of20ms by parameters optimization research. A new hydraulic buffer with bidirectional, high speed movement is presented by analysis of load characteristics in the flow distribution process. Calculation and field tests show that, the load impact velocity is largely reduced with operation of this hydraulic buffer, so that the reliability of flow distribution system is greatly improved. In order to realize the industrial applications of EHFS, the new system is installed in the stepless capacity control equipment of reciprocating compressor, and the dynamic characteristics of EHFS with operation of dynamic gas forces is discussed. Experimental results show that the capacity control process is stable without impact and the discharge pressure fluctuation is less than0.2bar.The main content of each chapter is summarized as following:In chapter1, the application fields, engineering background and research value of flow distribution system are expounded. The special application background and the technology status of EHFS with large flow rate and high speed in stepless capacity control of reciprocating compressors are described in detail. Through the comparison of common flow distribution technology schemes, the technique features of high speed on/off flow distribution are highlighted. Relative technologies such as high speed electro-hydraulic actuator, high speed on/off valve and high speed hydraulic buffer are analyzed. The research significance and main study content are proposed in the final section of this chapter.In chapter2, the performance indicators of high speed electro-hydraulic actuator are presented based on the application condition of EHFS. The common structure and working principle of electro-hydraulic actuator are introduced. The basic mathematical model is established based on the physical model of high speed on/off valve control hydraulic cylinder. The influences of main design factors on the actuator action delay are illustrated. Two new high speed actuators with different structures are proposed based on the theoretical analysis. Simulation models of electro-hydraulic actuators, dual high speed on/off valve parallel type and pilot type are established to do comparative research on their dynamic characteristics. Finally, optimization design theory of high speed actuators is proposed through analysis of structure factors.In chapter3, by analyzing performance characteristics of high speed EHFS, the necessity of adopting hydraulic buffer is described and the performance requirements of hydraulic buffer are proposed. Based on the load features with high speed and short stroke, the structure concept of high speed hydraulic buffer is presented. Then its working principle is elaborated. And the main structural characteristics are determined by mathematical calculation. By establishing the simulation model of the bidirectional buffer, research on dynamic buffering characteristics of opening and closing process is deeply developed. The optimization design theory is summarized in the last section of this chapter.In chapter4, the working principle of EHFS with large flow rate and high speed is expounded. The structure and elements of EHFS are introduced. Based on the physical modeling of EHFS, the mathematical model of valve motion is established with consideration of dynamic gas force. Then co-simulation model is established in AMESim and Matlab. The controllability, valve motion and dynamic characteristics of EHFS are discussed by simulation study. Theory basis for optimization design of EHFS is provided by analyzing the influence of key factors. Finally, a test rig for dynamic characteristics is built to validate simulation model and provide data support for improvement of EHFS design theory.In chapter5, the application of EHFS with large flow rate and high speed in stepless capacity control of reciprocating compressors is introduced. The structure of stepless capacity control equipment is described, and the performance characteristics of capacity control compressor are listed. A prototype of EHFS with large flow rate and high speed is designed combined with technical requirements of stepless capacity control technology. Control system consisting of upper computer, lower computer, TDC sensor and communication module is built. Experimental research is carried out on the hydrocracking compressor in Sinopec Tianjin refinery and the results show a remarkable energy saving effect.In chapter6, all achievements of the dissertation are summarized and the further research work is put forward.