Session: 05-01-04 Applied CFD

Paper Number: 65868

Start Time: August 11th, 12:50 PM

65868 - Flow Characterization in the Upper Cavity of a Rotary Compressor 

As hundreds of millions of Air conditioning (AC) systems are produced each year, and many of them use rotary compressors as the heat pump, optimizing the flow inside the rotary compressor to improve its reliability and efficiency becomes a key issue of the manufactures. Since the invention of the rotary compressor, its internal flow has been studied numerically with real models. However, the internal flow of a rotary compressor can be extremely complicated due to the complex internal structures’ geometry and high-speed moving parts, making it difficult to interpret the result by CFD simulation and repeat the simulation in different models. In our experiments for observing lubricant oil droplets above the rotor/stator in a rotary compressor, droplets’ movement reveals that there are two major effects that control the gas flow in the upper cavity of the compressor. One is the swirling jet produced by the high-speed rotating rotor with no-slip condition on its sidewall. The other one is the rotating disk effect induced by the top of the high-speed rotating rotor. Either of them has been studied individually in different areas. For example, the swirling jet is often used in combustors while the rotating disk is applied in viscous pump. However, the coupling of these two effects in the rotary compressor with different velocity ranges, size scales and fluid properties has not been studied according to our best knowledge. In our simulation, a model that only consists of a simplified rotor, simplified stator, sidewall and discharge tube (outlet) is built. Thus, the effect by small parts, such as the balance block and coils, is excluded. The rotor is set to rotate at 30, 60 and 90 Hz. Uniform velocity calculated with the flow rate and ambient pressure conditions are given at the inlet (rotor/stator clearance) and the outlet, respectively. No-slip conditions are defined at other walls. Steady-state K-omega SST and Large Eddy simulation turbulence models are applied, and the cases are computed with OpenFoam. The CFD results show that there is an inner recirculation zone above the rotor that creates a downward velocity component above the rotor, and an outer circulation zone above the stator. The CFD result meets the observation of the droplets’ movement above the rotor/stator. With the CFD results and the experiment’s observations, we propose the model of the oil droplet’s path in the upper cavity of the rotary compressor, which can help reduce the exhausted lubricant oil droplets from the compressor.

Presenting Author: Puyuan Wu Purdue University

Authors:

Puyuan Wu Purdue University
Ang Li Purdue University
Jun Chen Purdue University
Paul Sojka Purdue University
Yang Li Guangdong Meizhi Compressor Co., Ltd.
Hongjun Cao Guangdong Meizhi Compressor Co., Ltd.