Factors Impacting on Performance of Lobe Pumps: A Numerical Evaluation

Abstract

The aim of current research is to investigate numerically the fluid dynamics of lobe pumps and typical factors which could impact on performance of the pump including profile of rotor surface, number of lobes, gap size between rotor and casing, and clearance between two rotors, etc. The circular and epicycloidal curves are used to generate profiles for rotor surface, while the complex flow phenomena inside the pump are simulated by dynamic mesh technique. With wide range of investigated speed from 1000 to 5000rpm, the study produces significant information on flow pattern, velocity and pressure fields. The advantage of epicycloidal pumps over circular ones has been demonstrated via characteristic curve which performs pressure head versus rotational speed. Meanwhile the analysis has proved that multilobes, three and four lobes, do not increase performance of the pump but provide more stable output and higher capacity compared with two-lobe pumps. The results confirm great impact of gap size between rotor and casing wall on the pump efficiency. Decrease of the gap from 1.25mm down to 0.5mm produces about 425% increasing of pressure head. In addition, it has been also proved that the clearance between two rotors could be varied from 0.12mm to 0.15mm without much effect on performance of the pump.

Effects of Head Gaps and Rotor Gap on Flow Rate and Hydraulic Leakage of a Novel Non-Contact Rotor Blower

“…In 2018, Sun et al [7] determined leakage of flow rate per one revolution of the rotor through modeling the clearance like nozzle positioned directly on the housing of the blower. Kang, Vu et al [8] have used CFD to evaluate influence of the head clearances and the rotor clearances on the efficiency of traditional Roots blower which has rotor profile that is established from circular arc [9] and epicycloidal curve [10]. The results of the research [8] showed that the performance of blower decreased 43 % when the clearance dimension was 2.0 mm.…”

“…Kang, Vu et al [8] have used CFD to evaluate influence of the head clearances and the rotor clearances on the efficiency of traditional Roots blower which has rotor profile that is established from circular arc [9] and epicycloidal curve [10]. The results of the research [8] showed that the performance of blower decreased 43 % when the clearance dimension was 2.0 mm. Ashish et al [11] have investigated and evaluated the phenomenon of leakage of the Roots compressor with the involute rotor profile.…”

Numerical study and experimental validation of a Roots blower with backflow design

“…Litvin and Feng (1996) proposed an approach for the design and generation of the planar cycloidal gearings for screw Roots blowers and developed an improved design to avoid the surface singularity. Kang, Vu, and Hsu (2012) developed a Roots blower with an epicycloid curve, which demonstrated a better performance over circular ones. They also found that multi-lobe pumps did not exhibit a higher performance than two-lobe pumps but provided a more stable output.…”

Fluid analysis of cylindrical and screw type Roots vacuum pumps

“…Hence, Strasser [14] used the commercial computational fluid dynamics (CFD) solver, FLUENT, to simulate a gear pump, with a focus on the involute external gear pump. Subsequently, Kang et al [15,16] utilized the dynamic mesh method to provide an overall evaluation of factors affecting on performance of lobe pumps. They also proposed an improvement design of Roots rotor profile which was assessed by a CFD analysis using FLUENT package.…”