Comparison of PV-Diagrams Between CFD and Experimental Results for Twin-Screw Compressors

As new technological advances emerge at breakneck speed, efficiency and robustness of design drives innovation in the field of compr- essors, expanders, and pumps. At the core of such exploration rests the notion that experimental validation is needed to prove the concept and efficacy of novel designs. Unfortunately, due to limits in instrumentation and experimental setup, it is sometimes infeasible to grasp the physics behind complicated phenomenon solely through experimentation. Experimentation results can provide an incomplete picture which may in turn force an incomplete solution to be incorporated into the product design. Using an experimentally validated CFD model in conjunction with exi- sting experimental results allows for an unexpurgated view of the broader system. One such instance of this problem is experimentally producing the pressure—volume (PV) diagram of a twin-screw compressor with an attached economizer. Due to instrumentation limitations caused by the geometry, the PV-diagram is created by adjoining several pressure transducers placed along the female rotor. However, drawing a conclusion from this PV-diagram is incomplete because comparing the result against the CFD model show that the pressure behavior exhibited in the experimentally created PV diagram is only local to the neighborhood of the pressure transducers, whereas the CFD model show that a continuous view of the compression process exhibits a smoother average pressure transition within the entire volumetric pocket. By combining experimental results along with the appropriate CFD model allows for a broadened understanding of the underlying physics that cannot be achieved solely through experimentation.