Rotary compressor, CFD, compressor, parametric study, rotary displacement machine
Efficient compressors are generally important for applications in air conditioning and refrigeration systems. Therefore, innovative technologies are needed to improve their performance and expand their area of application. A new type of rotary compressor, called “Schukey compressor”, has been investigated both experimentally and theoretically. The Schukey-technology goes back to its founder Jürgen Schukey in 1987, who invented a special gear that enables two rotors to rotate out of phase in the same direction within the compressor housing. Each rotor consists of four rectangular shaped piston wings that interlock and perform non-uniform rotary movements, leading to a periodic change of the working chamber volume. During one revolution of the main shaft, 32 compression cycles are performed. Except for our own research work, no further development on this new device is known to us. Initial studies have shown that changes in the geometrical design of the machine, especially the position of the suction and discharge ports, have a direct influence on thermodynamical variables e.g. technical work, mass flow or pressure ratio. In this contribution, a parametric study is presented to determine the performance of the machine and to show optimization potentials with regard to the volumetric efficiency. The impact of the annular gap and port size variations is examined by using numerical CFD analysis. It is shown that the annular gap size does has a big impact on the mass flow rate and volumetric efficiency. In order to maintain a high efficiency, the gap size should be kept at least below 0.1 mm, where an efficiency of 85.3% is given. An enlargement of the discharge ports leads to an improvement of the volumetric efficiency up from 85.3% to almost 92% but also leads to a decrease of the pressure ratio at the same time since the compression phase ends off earlier. An enlargement of the inlet ports shows no significant effect in terms of pressure ratio and volumetric efficiency. By using the determined surface plots, the size of the ports can be estimated and adjusted according to the intended application of the compressor.