Semi-empirical modelling and analysis of single screw expanders considering inlet and exhaust pressure losses

At present, the performance analysis of volumetric expanders by semi-empirical model is a very popular method. How to improve the universality without reducing the calculation accuracy is the key issue. For an atypical volumetric expander, the irreversibility analysis of the working process for single screw expanders is still lacking. In this paper, we explore the possibility of using a semi-empirical model considering geometric constraints to improve the universality. Firstly, a basic model of SSEs is proposed, in which the model parameters related to the structure are directly calculated by the geometry instead of being calculated by the optimization algorithm. So, the number of the model parameters is reduced to 5. And then, the model is solved by our previous experimental results. However, the deviation between the calculation results and the experimental data is significantly large. So, the sub-process assumptions and calculation formulas are adjusted, including mechanical loss, leakage loss and pressure resistance loss. Then, the modified model is solved and compared with the result of the basic model. From the calculation results, the deviation of the modified model is significantly lower than that of the basic model. Meanwhile, the calculation results are in good agreement with the experimental data. Moreover, due to considering the exhaust resistance loss, not only improves the calculation accuracy of the modified model, but also makes the physical meaning of the model clearer. The work of this paper indicates that adding geometric constraints and modifying sub-process assumptions at the same time is an effective method to improve the accuracy and universality of the semi-empirical model simultaneously.

Automated summary

Currently, using a semi-empirical model for performance analysis of volumetric expanders is a popular method. The key challenge is to improve universality without reducing calculation accuracy. This paper analyzes the irreversibility of the working process for a specific type of volumetric expander and explores the possibility of using a modified semi-empirical model that considers geometric constraints to improve universality.