Study On The Effect Of Structural Optimization On Working Performance Of Roots-type Engine

In order to address the disadvantages of existing technology in the recovery of low quality waste heat steam,the research group puts forward a new low pressure steam generation device-roots-type engine.The roots-type engine is mainly used for the recovery of low quality waste heat steam of pressure lower than 0.8MPa and temperature lower than 230℃.As the core of power generation system,its performance has important influence on the final generation effect.In order to increase the working efficiency,improve the operation stability and enhance the working reliability,the paper studied deeply the working performance of roots-type engine,and improved the working performance of through the structure optimization.The paper mainly to carry out research from the following several aspects:1.Firstly,the paper briefly introduced the basic structure and working principle of rootstype engine,and then put forward four performance indexes according to the characteristics of the engine.Furthermore,based on the principle of volumetric rotating machinery,the mathematical model of performance indexs have been established,and provided theoretical basis for optimizing structure of the engine.2.The improvement design of rotor profile and structure parameters of roots-type engine were carried out.Based on the theory of engagement,New arc-involute-arc envelope rotor was put forward to improve the utilization coefficient of area and coefficient of engagement of the engine.Next the structure parameters were optimized with the total efficiency as the objective function,and according to the best value obtained,the performance parameters of the engine,such as the output torque、the output power and the flow rate,can be calculated.The results indicate that the working performance parameters have been improved after theoretical analysis and study.3.In order to carry out numerical simulation of working performance of the engine,roots-type engine was simulated using CFD technology and dynamic mesh technology.The pressure field and velocity field of the engine before and after optimization were discussed,and the relationship between volumetric efficiency and speed also was studied.The simulation results show that the the optimized engine reduced airflow pulsation and improved stability and volumetric efficiency.The numerical simulation results are similar to the theoretical results.4.With the optimized roots-type engine as the research object,a simple experimental platform with the compressed air as working medium was set up,and the working performance of roots-type engine were tested.Afterward,the variation law of performance indexs with speed was studied and the working performance curves of the engine before and after optimization were discussed in details.The test results show that the optimization results improve the working performance of the engine,and enhances the working reliability of the engine.The results also verify the correctness of the theoretical analysis and numerical simulation results.