Ivestigation Of Mathematical Modeling And Experiment For Scroll Expander

Utilizing Organic Rankine Cycle(ORC) to recover the industrial waste heat, solar heat, geothermal heat,engine exhaust heat is one of the effective technological approaches to realize energy conservation, emission reduction and environmental protection. Expander is a key component of the ORC, its performance has a significant effect on the overall ORC system. This paper presented a mathematical model for scroll expander and model validation was done with experimental work. The main content is as follows.(1) The meshing theory for scroll profiles was introduced, and the basic criteria of meshing was illustrated. Two kinds of scroll profiles, including involute circle, segment involute, square involute, involute circle of variable radius and hybrid profiles, were compared. The effect of these curves on the geometrical parameters and performances of the scrolls was analyzed, and in conclusion, on the premise of considering economy and practicability, circle involute is superior to other profiles;(2) The volumes of the working chambers were calculated with respect to the orbiting angle by integration method and base line method,and the calculated results were compared with actual model. The maximum error between the results of the calculation using base line method and the actual model was 8.76%, The maximum error between the results of the calculation using integration method and the actual model was 15.95%. The analysis results indicated that the base line method has more satisfactory accuracy compared with integration method. N2 was used as working fluid, Based on the first law of thermodynamics, the law of conservation of mass and state equation, considering working leakage and heat transfer, the thermodynamic model of the scroll expander was established. The models has been implemented into a FORTRAN computer code.This code calculated the pressure, masses in each of the working chambers as a function of the orbiting angle for an entire revolution;(3) In order to verify the accuracy of the model, N2 was used as working fluid, the test rig of the scroll expander performance was set up. The output voltage and current of prototype were tested under different inlet pressure and the output power was obtained. The maximum deviation between theoretical output power and actual output power was 45 W, the minimum was 16 W. From the comparison of the simulated and measured data, it can be seen that the expander model predicts the output power very well.