Sound Source in Automotive Refrigerant System
by Joohwa Sarah Lee and Wolfgang Polifke
Motivation
Modern vehicles including electric automotive such as Battery Electric Vehicle (BEV) and Plug-in hybrid Electric Vehicle (PHEV) provide significantly enhanced acoustic comfort by reducing overall noise levels. Thus, a particular types of sound such as hiss and jet noise arising from an automotive air conditioning system unexpectedly become audible to passengers under specific operating points. However, the mechanisms of the sound generations are still not clearly specified, nor the corresponding operating points are unknown.
Objectives and Strategy
The goal of this project is to investigate mechanisms of the hiss and jet noise generation and to specify the corresponding operating points. The two types of noise are generated in thermostatic expansion valve (TXV), where the refrigerant flow undergoes phase transition from sub-cooled liquid into liquid-vapor phase due to depressurization. Initially, the sound characteristic and the resulting two-phase flow patterns are obtained by experiments on an automotive a/c circuit and even on an simplified set-up comparable with the automotive circuit. Based on those studies, acoustic effect of bubble dynamic, specifically, of evaporation under depressurization, is examined in theoretical and numerical approach.
Acknowledgement
This project is a part of Marie-Curie Initial Training Network (ITN) project, FlowAirS, Silent Air Flows in transport, buildings and power generation. We greatly acknowledge the financial support of the European Commission Seventh Framework Programme (FP7) within People work programme.