Experimental Study On Dynamic And Steady State Performance Of Organic Rankine Cycle

Organic Rankine Cycle(ORC)is an effective medium-low temperature waste heat power generation technology.It is of great significance to study the performance of ORC system to improve the utilization efficiency of medium low temperature waste heat in China.At present,the experimental research on ORC system is less,and mainly focuses on the steady-state characteristics of pure working fluid.Therefore,in this paper,the steady-state performance and dynamic response characteristics of ORC system under different working conditions are experimentally studied.It can provide the basic experimental data and theoretical guidance for the actual operation of ORC system and the control strategy.The main work and conclusions are as follows:1.The ORC system experimental platform is buildt.A 1kW ORC system experiment system is built,which mainly includes four parts:heat source,working medium circuit,cooling pipeline and data acquisition system.A multi-stage centrifugal pump is used as working medium pump,and the expander is modified from a scroll compressor.The test rig uses steam from an electric steam generator as the heat source.2.Steady state characteristics of ORC system are studied by experiments.R245fa,R141b and their mixture are used as circulating working fluids to test ORC system performance under different inlet pressure,rotating speed and cooling water flow rate of expander.The results show that:under the heat source condition of 100-110℃,when the inlet pressure rises,the output power of the expander increases,the thermal efficiency of the system decreases with the increase of the speed of the expander,and the output power increases with the increase of the cooling water flow,and the rising trend tends to moderate with the increase of the cooling water flow.In the contrast experiment of working fluid components,the mechanical efficiency and isentropic efficiency of the scroll expander are 80%-96%and 50-60%respectively.The maximum output shaft power of pure working fluid is 669W,and the maximum thermal efficiency is 5.2%;The maximum output shaft power of 0.25R245fa/0.75R141b(mass ratio)is 731W,and the maximum thermal efficiency is 5.5%.Compared with pure refrigerants,mixed refrigerants have higher output power and thermal efficiency;3.Dynamic characteristics of ORC system are studied by experiments.Taking R245fa and 0.5R245fa/0.5R141b(mass ratio)as working fluids,the dynamic response characteristics of ORC system’s main parameters under the step change of expander inlet pressure,speed and cooling water flow were studied.The results show that the influence of parameter disturbance on the inlet temperature of expander is very small,but the response speed of working fluid flow,expander output power,expander torque and speed is relatively fast,and the response time is between 1-5s;The response time of the inlet and outlet temperature of the working fluid pump is 200-800s,and the response time of the outlet temperature of the working fluid pump is obviously behind the inlet temperature;In the dynamic characteristic experiment,there is no obvious difference between the pure working fluid and the mixed working fluid.