Abstract:Computational fluid dynamics (CFD) can help in understanding the nature of leakage flow phenomena inside the rotary positive displacement machines (PDMs). However, due to the lack of experimental results, the analysis of leakage flows in rotary PDMs by CFD has not yet been fully validated. Particle image velocimetry (PIV) tests with a microscopic lens and phase-lock were conducted to obtain the velocity field around the tip gap in an optical Roots blower. The three-dimensional unsteady CFD model of the Roots b… Show more
“…However, a series of factors deteriorating the results of the PIV test were highlighted, such as limitations in resolving flow features in regions near the gaps and the large sample size required. Numerical analyses of a Roots blower were carried out by Sun et al [14]. It is observed that the CFD flow field agrees with experimental results in the flow pattern and velocity magnitude at certain areas but overestimates the leakage flow velocity.…”
“…However, a series of factors deteriorating the results of the PIV test were highlighted, such as limitations in resolving flow features in regions near the gaps and the large sample size required. Numerical analyses of a Roots blower were carried out by Sun et al [14]. It is observed that the CFD flow field agrees with experimental results in the flow pattern and velocity magnitude at certain areas but overestimates the leakage flow velocity.…”
“…The investigations of Stosic 2 and Pascu et al 12 have shown that the use of new techniques for rotors profiling helped to manufacture rotors of complex shapes with tolerances of the order of few microns, which improved efficiencies. Also, a limited number of the previous investigations have been carried out 19,20 to characterise flow leakages using experiments and CFD simulations. The gas pulsations are also a main source of noise within the discharge cavity and have been investigated since 1986 by many authors.…”
Spatial flow field velocities within the discharge cavity of an optical screw compressor have been measured using LDV and PIV techniques. Angle-resolved velocities were obtained over a time window of 1° at a speed of 1000 rpm, pressure ratio of 1 and temperature of 55°C. Comparison between the LDV and PIV results showed very good agreement and provided a good level of confidence in the presented data. Overall, the flow field results revealed the presence of a complex, turbulent, 3D and vortical flow structure within the discharge cavity. LDV measurements at the exit of the discharge port showed that the inflow into the cavity has two distinct flow features that includes undulated velocity profiles with high gradient during the opening of the port, and uniform jet-like flows during the rest of the time. The energy necessary to create that jet-like flow was from the built-in pressure in the rotors. Turbulence fluctuations were high and followed the mean flow variations with values up to 35% of the mean values during the undulating flow. PIV spatial mean flow measurements showed a uniform axial flow close to bottom of cavity that has been transformed to a stable solid body vortex at the top of the cavity. These measurements within the discharge cavity are made for the first time and they are unique and in great detail that can be used for validation of CFD codes and optimisation of compressors to improve their efficiency for different system applications. Graphical abstract [Formula: see text]
“…An investigation of flow through the male rotor housing clearance of screw machines was carried out by Utri [11] who compared simulation results with flow pictures obtained using the Schlieren method. Recently, an experimental and numerical study of a roots blower in actual running condition was carried out by Sun et al [12], They implemented the PIV technique for clearance flow visualization. A series of factors deteriorating the results of the PIV test were observed such as the surface flaws of the transparent window, the reflection of the surface, the jitter in the phase-locking due to uncertainties in the transmission of the synchronized gear, the accumulation of the liquid particles and the pressure fluctuations.…”
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