Clearance Analysis and Leakage Flow CFD Model of a Two‐Lobe Multi‐Recompression Heater

Abstract

This paper reports the results of a study on multi-recompression heating. This process employs a Roots-type mechanism to heat gases to very high temperatures by compressive gas heating. A CFD model predicting the leakage flows in the machine was developed, and an excellent comparison with experimental data taken on a two-lobe Roots blower was obtained. A "clearance analysis" was performed to show that the clearance between the impellers remains constant for 96% of the angles of rotation. Assuming a quasi-steady state, the CFD simulation was performed for a single angle of rotation. A three-dimensional analysis showed that the flow field is identical along the rotor length, except for the leakage through the end plates. Hence, the model was further simplified to a two-dimensional analysis. This research may provide guidance in predicting the leakage flows in other blowers of the same kind with a different geometry.

Effects of Head Gaps and Rotor Gap on Flow Rate and Hydraulic Leakage of a Novel Non-Contact Rotor Blower

“…Considering the compressing process in the outlet chamber, from [17], the relation between temperature and pressure are given by the following set of equations: (14) substituting (11,12,13) into (14), we can calculate the temperature of the outlet chamber:…”

“…The results of the research [8] showed that the performance of blower decreased 43 % when the clearance dimension was 2.0 mm. Ashish et al [11] have investigated and evaluated the phenomenon of leakage of the Roots compressor with the involute rotor profile. Based on survey of those researches, we can see most of the works have implied CFD and experimental method, and the theoretical method was rarely used due to the complexity of Roots profile and due to the fact that the clearances (the clearance between two rotors in matching process K  and the clearances between rotor and stator r  ) significantly affect on performance of the blower.…”

Experimental and Numerical Investigation of Tip Leakage Flows in a Roots Blower

“…Xing et al [19] used TwinMesh and ANSYS-CFX to simulate a three-lobe Roots blower numerically and display the presence of strong vorticial flow field and backflow through three gaps. Joshi et al [20] predicted the leakage flow rate in a two-lobe Roots blower using a stationary mesh in CFD at a single rotation angle and compared them with experimental data. A tip step which was also applied in the present study was used and was proved to reduce tip leakage of the Roots blower [20].…”

Numerical study and experimental validation of a Roots blower with backflow design

“…Li, Jia, Meng, Shen, and Sang (2013) analysed the effects of different pressure angles on the velocity and pressure of oil as well as the turbulent kinetic energy by 2D numerical modeling. Joshi, Blekhman, Felske, Lordi, and Mollendorf (2006) analysed the clearance between the rotors, showing that the clearance remains constant for 96% of the angles of the rotation in a working period. They also investigated the leakage of the Roots blower through a quasi-steady state analysis.…”