Abstract
Customized grid generation of twin screw machines for CFD analysis is widely used by the refrigeration and air-conditioning industry today, but is currently not suitable for topologies such as those of single screw, variable pitch or tri screw rotors. This paper investigates a technique called key-frame re-meshing that supplies pre-generated unstructured grids to the CFD solver at different time steps. To evaluate its accuracy, the results of an isentropic compression-expansion process in a reciprocating piston cylinder arrangement have been compared. Three strategies of grid deformation; diffusion equation mesh smoothing, user defined nodal displacement and key-frame remeshing have been assessed. There are many limitations to key-frame re-meshing. It requires time consuming pre-processing, has limited applicability to complex meshes and leads to inaccuracies in conservation of calculated variables. It was concluded that customized tools for generation of CFD grids are required for complex screw machines.
Highlights
Rotary Screw Compressors are commonly used in industrial refrigeration and air-conditioning
Due to the introduction of new refrigerants, the use of natural refrigerants and other means of reducing greenhouse gases, the trends in refrigeration and heat pump technology today are towards higher pressure applications. In such cases single screw compressors start to dominate due to higher load capacities and more flexible control system than a twin screw compressor
Capability to analyze performance of such complex screw machines is prerequisite for their successful design and commercialization, There have been a number of studies conducted to develop thermodynamic models for twin screw and single screw compressors
Summary
Rotary Screw Compressors are commonly used in industrial refrigeration and air-conditioning. Capability to analyze performance of such complex screw machines is prerequisite for their successful design and commercialization, There have been a number of studies conducted to develop thermodynamic models for twin screw and single screw compressors. Voorde et al (2005) have developed a grid conversion algorithm for unstructured to block–structured mesh from the solution of the Laplace equation for twin screw compressors and pumps Apart from these works, there are only a few reports available on transient three dimensional CFD analyses of screw machines. Two cases with increasing geometric complexity of the working chambers are studied, namely an isentropic compression-expansion process in a reciprocating piston cylinder arrangement and the twin screw compressor which proved to be extremely challenging for key-frame re-meshing
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