Research On Performance Of Sliding Vane Expander With Synchronous Rotating Cylinder And Guiding Vanes

Expander is an important component of power cycle,which is one of the key equipment to convert thermal energy into kinetic energy and mechanical energy.In the research of supercritical carbon dioxide power cycle,organic Rankine cycle and waste heat recovery power cycle,which are proposed and studied to alleviate the energy and environmental problems,improving or developing more suitable and energy-efficient novel expander is a hot topic of research in recent years.Turbo-expanders are suitable for large and medium-sized application situations,while volumetric expanders are widely recommended for small and medium-sized application situations.Sliding vane expander is one of them,which has the advantages of simple structure,low cost,high reliability and good power balance performance.However,there are many problems such as serious friction and wear in cylinder,small working flow,low efficiency and internal leakage,which hinder the application and development of sliding vane expander.Therefore,a novel type of sliding vane expander with guide vanes and synchronous rotating cylinder is proposed and studied in this paper.The expander is not only equipped with the cylinder rotating with rotor synchronously,which can effectively reduce the wear and friction,but also reduces the diameter of the rotor to increase the volume of chambers,in order to improve the air flow and enhance the impact force of the air flow on the sliding vanes,several guiding vanes which can change the direction of the air flow are set in the intake and exhaust passages.In terms of research methods,Solid Works is used for establishing geometric model,ICEM is used for mesh generation,RNG k-ε turbulence model is selected,and FLUENT is used for numerical simulation of the novel expander model combined with dynamic mesh technology.The main research contents and results are as follows:(1)The intake guiding vanes can change the direction of air flow,and cause a certain degree of expansion effect,which is beneficial to the flow field distribution and performance of the expander.The exhaust guiding vanes is mainly used to change the direction of air flow and make the exhaust smooth.(2)For the expander model with 6 sliding vanes,the end edge angle of exhaust port is set to 270°,277.5° and 285° separately,and the above three schemes are compared.According to the simulation results,the changes of internal flow field and exhaust parameters are analyzed.The results show that on the premise of ensuring that there is at least one transition chamber between the intake and exhaust passages,properly increasing the end edge angle of the exhaust structure is conducive to improving the clearance volume problem,increasing the exhaust mass flow,improving the isentropic efficiency,and delaying the leakage.(3)The expander models with 6,8,10 and 12 different numbers of sliding vanes respectively in two groups of different exhaust structure schemes are set to simulate and compare.The simulation results are analyzed to find out the influence of the two groups of schemes on their performance,which contain changing the numbers of sliding vanes while the end edge angles of exhaust structure are constant and changing both the numbers of sliding vanes and the end edge angles of exhaust structure.The results show that while the end edge angles of exhaust structure remain unchanged,the more the numbers of sliding vanes are,the better the exhaust continuity is;while both the numbers of sliding vanes and the end edge angles of exhaust structure are increased,the decrease of the average exhaust volume can be alleviated,the isentropic efficiency can be improved,and the leakage at the end of the sliding vanes can be reduced.(4)With the same cylinder size,four schemes are set to simulate and compare,of which the minimum clearance ratio ε are 0.03,0.04,0.05 and 0.06 separately.The results show that increasing the value of ε in the research range is beneficial to enhance the continuity and stability of exhaust,reduce the expansion pressure ratio,increase the working flow rate,improve the isentropic efficiency,and improve the leakage condition at the end of the sliding vanes.