Design of Small Scale Shockwave Generators for the ORCHID Setup

This report focuses on the design and analysis of various subcomponents of the supersonic nozzle test section of the ORCHID setup. The primary concern is a study dedicated to the model support system which is crucial to the success of a series of gas dynamic experiments for high fidelity software validation. Standard design rules and empirical models are not directly suitable for the nozzle test section design, mainly due to the thermodynamic behaviour of the working fluid, which expand close to the critical point. The configuration of such a support system for the model typically consists of a sting and base support. The aim of the study is to design this model configuration and computationally investigate the influence of these non-ideal flow effects on the conceived model and support system. The model support must remain minimally intrusive to the results of the flow field whilst also being structurally sound. Such results will be useful for the ongoing development of realising the ORCHID setup. A number of sub-goals to complete the objective included analysing non-ideal compressible flow simulations, designing the model and support system and conceiving a coupling tool between the fluid and structural domain. A field known as fluid-structure interaction was investigated to model the coupling tool, and it revealed that using a method known as the radial basis interpolation was recommended. This transferred values between the interfacing boundaries of the fluid and structural domain. Several geometric models were investigated and a diamond model was chosen as it transfers the most stress onto the support system. Pertaining to the fluid setup, a frontal height of 9 mm was selected for the diamond based off results and a review of literature concerning the supersonic blockage phenomenon. The Method of Characteristics was also used to generate the diverging nozzle profile. Concerning the structural setup, a low-carbon AISI 1010 steel was chosen. Two test cases were chosen which involved high-fidelity calculations. This required the coupling tool, where information was transferred to the FEA solver. The first case being an aligned case where the model was aligned to the nozzle and the second being a deflected case. Results indicate that the effect of pressure was insignificant for the aligned case, with a maximum stress of 0.564 MPa and deflections at the tip being 6.074 x 10-4 mm. For the deflected case, it was found that the influence of temperature played a major role in the structural integrity; an increase of 500% in stress from the results of pressure influence and 7% in maximum deflection at the tip. The main conclusions drawn are that the support system would not yield under steady state conditions but the deflections observed was considered significant enough such that it may hinder the results of the flow field. As a result, recommendations for future work include conceiving the automation tool to conduct a full two-way fluid-structure interaction process to analyse plant start-up.

Subject

FEA
FSI
vapour tunnel
supersonic nozzle
Model Support System

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master thesis

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