Abstract
Rotary twin screw machines are used in the wide range of industrial applications and are capable of handling single and multiphase fluids as compressors, expanders and pumps. Concentration of liquid in the inlet flow can influence the performance of the machine significantly. Characteristics of the multiphase flow at the suction of a screw compressor depend on the local flow velocities and concentration. Local flow velocity measurements inside the screw compressors are difficult to obtain. However other flow properties such as local pressures are easier to attain. It is therefore useful to carry out experiments with local pressure variations in the suction which can be used to validate the 3D numerical Computational Fluid Dynamic (CFD) models that could help in studying the single and multiphase flow behaviour in screw compressors.This paper presents experimental efforts to measure the local pressure losses inside the suction plenum of the screw compressor. Pressure variations are measured at 23 locations in the suction port at various operating conditions and compared with 3D CFD model. The grid generator SCORGTM was used for generating numerical mesh of rotors. The flow calculations were carried out using commercial 3D solver ANSYS CFX. It was found that the local pressure changes predicted by the CFD model are in the good agreement with measured pressures. This validated the use of CFD for modelling of the single phase flows in suction of screw machines.
Highlights
IntroductionManufacturers and users are constantly challenged to broaden the scope of application of such machines and operate them more efficiently than ever
Screw compressor developers, manufacturers and users are constantly challenged to broaden the scope of application of such machines and operate them more efficiently than ever
The measured results are compared against 3D Computational Fluid Dynamic (CFD) simulations for the compressor main rotor speeds of 4000, 6000 and 8000 RPM
Summary
Manufacturers and users are constantly challenged to broaden the scope of application of such machines and operate them more efficiently than ever. One of the objectives is use of screw compressors for handling of multiphase flows. Chamber models such as the one embedded in SCORPATH, as discussed in [1], provide very good accuracy in predicting standard oil injected and oil free compressor performance. The reason is that, the thermodynamic models are computationally efficient and reasonably accurate they do not capture fully the characteristics of the fluid transport through the suction and discharge plenums. More detailed characterization of flow is required and it is believed that 3D CFD modelling can offer accurate prediction of the flow in the suction and discharge plenums of screw machines
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