Simulação numérica de escoamentos em difusores radiais modificados para aplicação em válvulas do tipo palheta

Abstract

Reed-type valves are widely used in reciprocating compressors used in refrigeration systems. The radial diffuser model is widely used as a simplified geometry for reed valves in numerical simulations. In this work, the global parameters of effective force area and discharge coefficient for a modified radial diffuser with a 23° chamfer were evaluated. Numerical simulations were carried out using the free and open source software OpenFOAM, for small gaps between discs. A two-dimensional, permanent and isothermal flow was considered, whose governing equations were discretized by the Finite Volume Method, using two turbulence models for low Reynolds numbers. The simulation results of the modified diffuser were compared with data obtained for diffusers without a chamfer. The addition of the chamfer in the diffuser model resulted in smaller recirculation bubbles compared to the diffuser without modifications, resulting in lower pressure drop and lower reduction in the flow passage area. The effective force area presented a behavior close to a decreasing exponential function in relation to the spacing between discs and higher values for the modified diffuser for dimensionless spacings up to 0,04. The discharge coefficient showed a linear behavior and higher values for the modified diffuser for all spacings analyzed.