Centrifugal Turbopumps - Flow Physics and Modelling

Abstract: Choices made in the early stages of a design process are crucial. They dictate many of the limitations and freedoms the designer has in later stages of the design. Informed decisions are therefore crucial at this stage. With the increasing computational power of modern computers, more and more designers utilise CFD software to design and evaluate performance of turbopumps. The simulations allow the designer to visualise intricate flow patterns and simulate effects of advanced 3D geometry. However, even with modern computers, CFD simulations are relatively slow and should, therefore, mainly be used to improve an already decent design. Centrifugal pumps are complicated, and in order to perform fast calculations the flow is modelled in a simplified fashion. Analogies from the field of centrifugal compressors are utilised since research within this field has progressed further in certain areas. Generally, the flow in radial turbomachinery is not well understood, and many empirical correlations are still in use, at least in open literature. An extensive literature review has been made, detailing the flow through the pump. Ways to model these flows are presented and discussed. The main aim of this degree project is to develop a computer-program for the early stages of new centrifugal turbopump development. In order to develop this software, the flow physics of a centrifugal pump has been studied and broken down in a way that allows the vital parts to be easily implemented in computer code. The developed tool achieves its main purpose, being able to quickly deliver a preliminary design with analysis regarding off-design performance. The software developed from these models allows generation of a preliminary design, from specified design criteria, in less than a second. The program has been validated against a similar, commercial, program, with satisfactory results. All geometry created within the software can also be analysed in off-design, i.e. varied mass-flow and rotational speed. Another aspect regarding off-design is the stable operating-range, which is included in the analysis.