Verified calculation of compression process in a scroll compressor
Authors: Zharov Anton A. , Borisenko Artem V. , Valiakina Anna V. , Bykovskaya Veronika  S. 
Published: August 2023

BACKGROUND: Because the geometric compression ratio of scroll compressors remains constant and the actual compression ratio (from suction to discharge pressure) varies depending on the operating conditions, allowing additional compression to occur in the first (central) cavity of scrolls up to the discharge pressure is necessary for correctness of the dynamic calculation of compressors. When the pressure in the different cavities in a scroll block during shaft rotation is determined, we need to take into account the surge that occurs immediately after the union of the first and second cavities between the scrolls. Simultaneously, during the design of the geometry of spirals, undercutting the end of the spirals must be considered to ensure the required geometric compression ratio.
AIM: The aim of this study is to create a refined methodology for the dynamic calculation of a scroll compressor, which takes into account the constancy of geometric compression ratio and pressure jumps when the first and second cavities (central and adjoining cavities) between the scrolls are combined.
METHODS: A step-by-step methodology for the dynamic calculation of a scroll compressor is presented. The principles of modeling the compression process in the scroll compressor in a Mathcad modeling environment are outlined. The case of different geometric and actual degrees of compression of the compressor is considered. The construction principle of the compressor indicator diagram is presented. Methods of determining the forces and moments that arise in the compressor-operation process are presented, and their graphs are shown. A practical example of modeling the advantage of the proposed methodology is shown.
RESULTS: Dependence that allows estimation of the change in the volumes and pressure in the compressor compression cavities according to the angle of scroll trimming is obtained. The dependence of the change in the forces and moments that arise during compressor operation, which takes into account the pressure jump caused by cavity unification, is obtained. The modeling accuracy of the scroll-compressor compression cavities and the processes that take place in these cavities are assessed by determining the relative error of the effective compressor power resulting from the thermal calculation and the power resulting from the dynamic calculation. The power error in the aforementioned calculations amounts to 8.8%, which indicates the high accuracy of the proposed methodology.
CONCLUSION: A refined method of dynamic calculation of a scroll compressor in a Mathcad modeling environment has been developed. This method allows calculation of the pressure in paired cavities of a scroll block, including all the necessary forces and moments that arise during the rotation process of the compressor shaft. This method also takes into account scroll trimming to obtain the given geometric degree of compression and the pressure jump when the first and second cavities between the scrolls are combined.