Twin-screw compressors are very well known since the last century, but only nowadays, they become largely used in industry. Better performances may achieved, but this is possible only applying sophisticated techniques (CFD) that requires empirical validation. Discovering the flow structure inside a screw compressor and provide empirical data for validating purposes is the aim of the thesis. This was made possible using techniques known as LDV and PIV. It must be empathised that designing an optical compressor and measuring its flow is not an easy task. On one hand, the machine must run without oil therefore, at low speed and low pressure ratio; On the other hand, the compressor has to run in such a way that a representative internal flow is produced. It was found that the best compromise was, running the compressor at 1000 rpm with pressure ratio 1: 1. The LDV, revealed that flow within the rotor chamber can be divided in three zones: • The first, at the leading edge and in the centre, is dominated by the rotor movement, • The second, at the trailing edge, is dominated by the discharge process • The third, near the clearances, is dominated by the leakages. Although LDV is more precise than PIV, the latter proved to have a superior ability to visualise the complexity of the flow at the discharge chamber. It was found that: • The beginning of the discharge process is always unstable and shows jet like flows moving from rotor to discharge chambers • The remaining of the discharge process is stable and, at the top of the discharge chamber, a strong swirl motion takes place. Flow at the inlet port is slow, stable and almost independent of the rotors
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:578050 |
| Date | January 2011 |
| Creators | Guerrato, Diego |
| Publisher | City University London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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