Conference Year

2012

Keywords

Screw, Expander, Experimental, Techniques, Aquisition

Abstract

For the past twenty years the Centre for Positive Displacement Compressor Technology, at City University, has employed experimental techniques for the measurement of screw compressors’ performance where both experimental data and predicted mathematical models are found to be in agreement with each other. Some of the experimental measuring techniques involve the use of pressure and temperature transducers installed in the housing to determine the vital thermodynamic process characteristics and functioning performance of compressors. Moreover, as advanced technologies were available, measurements were performed in an optical compressor with a transparent window near the discharge port to allow the application of a laser technique, Laser Doppler Velocimetry (LDV), to investigate the axial mean flow and turbulence characteristics inside the working chamber of the male rotor.Recently a prototype two-phase screw steam expander has been designed and developed as a means of power recovery from liquid geothermal brine. An experimental setup has been designed by using a set of new generation instruments to complement the unit’s numerical modeling, from which predictions of an adiabatic efficiency in the order of 70%, were obtained. The testing includes measurements of instantaneous pressure and temperature in the suction and discharge port, instantaneous torque, speed and flow rate as well as monitoring the temperature and pressure of its lubrication system. Furthermore, four miniature high resolution pressure transducers were installed in the expander unit to measure the main rotor inter lobe temporal pressures with respect to crank angle of the main rotor. The high dynamic characteristics and response of the instrument are captured by a real time processor, National Instrument Compact-RIO, data logger and the programming is done using LabVIEW.The paper presents the measuring method, preparation of the instruments, acquisition and processing of the results obtained during experimental investigation of the two-phase screw expander.

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