Elarrami, Ablgasem M. (2018) Experimental and Numerical Based Analysis of Performance Characterisation of Roots Blower. Doctoral thesis, University of Huddersfield.

Roots blower is a positive displacement machine widely used as pressure or vacuum device in several industrial processes due to its simple construction, large volumetric efficiency and it has been most effective in low or moderate compression ratios. There are several geometric and flow relevant variables that affect its operation and performance. Internal leakage is an essential issue of the Root blower’s design. The leakage (slip) in the Roots blower effect the process efficiency by affecting the mass flow rate and therefore the volumetric efficiency, so the proper sizes of clearances must be provided inside the blower. The flow field conditions, inside clearances, and at the inlet and the exit of the blower are unsteady. The temperatures, pressures, and velocities vary significantly and are a function of operating condition and geometry of the Roots blower.

Based on available literature, extensive studies are being carried out to improve the efficiency of current models of Roots blowers, as well as to develop new blower models. But, the detailed knowledge of the flow behaviour in such machines is still a subject of active research. This is because most of the studies conducted lack details analysis of flow characteristics and limited studies on the local flow behaviour within these blowers have been reported. Therefore, the main aim of this study is the in-depth characterisation of internal flow with varying clearance sizes of Roots blower in order to improve their performance. Experimental approach and numerical method using Computational Fluid Dynamics (CFD) have been used in this research study.

Qualitative and quantitative analyses were carried out to establish the effect of operating conditions and clearance sizes on the flow and performance characteristics of the Roots blower. Based on these in-depth analysis, the performance characterisation of the influence of rotational speed and pressure difference on the Roots blower performance under the transient condition has been conducted and it is a new add to available knowledge in this field. Also, the effect of pressure difference, rotational speed and gap size on the variation and the distribution of other performance parameters such as pressure, temperature and velocity within the blower was established. Moreover, a new non-dimensional analysis of performance parameters and develop novel empirical and semi-empirical correlations for performance factors of Roots blower are main contributions to the knowledge have been achieved in this research study.

Furthermore, a new clearance model of Roots blower has been developed which considered as a main novelty in this study. Numerical characterisation of pressure fluctuations in both time and frequency domain with clearance variation inside the blower has been achieved. A new methodology for detection of the change of clearance size inside Roots blower has been developed.

FINAL THESIS - Elarrami.pdf - Accepted Version
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