Researchs On Flow And Heat Transfer Mechanism And Optimization Method Of CW Primary Surface Heat Exchanger

In the micro turbine engine,compared with improving the existing components to improve the aerodynamic thermal cycle parameters,the installation of regenerator is a less difficult and more effective method.After adding the regenerative cycle into the simple thermal cycle,the thermal efficiency of the micro turbine can be increased by more than 10%.In view of the compact structure and strong heat exchange capacity of CW type original surface heat exchanger,it can be applied to the heat recovery system of micro turbine.However,the research on the working mechanism and design method of the heat exchanger is not mature.Therefore,it is necessary to carry out the research on the flow characteristics and heat exchange mechanism in the microchannel of CW type original surface heat exchanger and develop the design method of heat exchanger,It has practical engineering significance to improve the performance of micro turbine power plant.First of all,a mathematical model with low Reynolds number k-ε is established.Finally,combined with the existing research,the reliability of the calculation model is verified.The flow and heat transfer mechanism of heat exchanger and the influence of structural parameters,such as the ratio of height to width of channel section,the structural parameters of flow direction period and the ratio of equivalent diameter of cold and hot channels on the comprehensive performance of heat exchanger are discussed.The results show that the weakening of wall boundary layer in the process of secondary flow and diversion of fluid in corrugated channel strengthens the heat transfer,the influence of structural parameters on the comprehensive performance of heat exchanger has its specific rules.Secondly,based on the Kriging surrogate model optimization design method,the heat exchanger design work is carried out.Taking the heat exchanger structure parameters as design variables,the total heat transfer coefficient K and the air fanning friction coefficient as optimization objectives,Latin hypercube sampling method and genetic algorithm NSGA-II are used for sample collection and multi-objective optimization respectively.In addition,in order to avoid the influence of the inlet section effect,the verification of fluid full development is carried out,and the accuracy of Kriging surrogate model is verified by using leave one method.The results show that the heat exchanger structure can meet the design requirements.The heat recovery is 86.3%,and the total pressure recovery coefficients of air and gas also meet the design indexes.It shows that the application of surrogate model optimization design to the original surface recuperator design is feasible.The full ring heat recovery system of micro turbine device is composed of bending heat exchange plate superimposed and welded.On the basis of the previous research,a single arc bending heat exchange plate model with involute line and different parameters is established,and the working conditions of various types of heat exchange plate are numerically simulated,in order to provide reference for the design and processing of bending heat exchange plate.It is found that the comprehensive performance of the circular arc heat exchanger plate is the best,and the comprehensive performance increases with the increase of the circular arc curvature of the heat exchanger plate.Therefore,in the processing of the full ring regenerator,it is appropriate to press and bend the heat exchanger plate according to the large curvature circular arc.