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An experimental investigation in to a highly forward swept, low specific speed turbocompressor

Cattell, R. (2019). An experimental investigation in to a highly forward swept, low specific speed turbocompressor. (Unpublished Doctoral thesis, City, University of London)

Abstract

A novel turbocompressor with ultra high forward sweep has been investigated using optical flow visualisation, Laser Doppler Velocimetry (LDV) and testing to establish the relationship between inlet conditions and compressor geometry, and compressor performance.

This compressor type, now known as TurboClaw®, exhibits efficiencies comparable to existing positive displacement compressors but below standard radial turbocompressors designed to operate at much higher shaft speed. This work extends the understanding of the compressor by examining the internal flow field with the intention of informing new designs in order to improve performance.

A three times scale model of a commercially available compressor was designed and built. The test rig had optical access allowing flow visualisation of the whole diffuser passage and the rotor. High speed photography with smoke injection was used to image the bulk flow. In addition, LDV was used to determine the flow field to facilitate future CFD studies. These investigations showed the presence of pulsing flow that propagated the full length of the diffuser. However, there was no evidence of flow separation in the LDV results, even though the flow gravitated to the outer wall of the diffuser as it flowed round the bend. The LDV also showed a difference between the direction of the flow exiting the impeller and entering the diffuser implying slip is a significant factor in the compressor’s performance. Investigations on the effect of blade height and the generation of an empirical prediction tool were performed on a second compressor test rig with commercial scale dimensions. A method for comparing various blade height data on a single chart was developed. This showed that there is a positive relation between blade height and pressure ratio. This data was used to develop an empirical performance prediction tool that links impeller diameter, blade height and inlet conditions to the compressor performance. Measurements of the static pressure at the exit of the impeller have shown significant pressure rise showing the reaction of TurboClaw is higher than previously thought.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments: Doctoral Theses
Doctoral Theses > School of Mathematics, Computer Science and Engineering Doctoral Theses
School of Mathematics, Computer Science & Engineering > Engineering > Mechanical Engineering & Aeronautics
Date Deposited: 14 Jan 2021 14:12
URI: https://openaccess.city.ac.uk/id/eprint/25522
[img] Text - Accepted Version
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