Abstract
In the context of the cooperative development of the L75 Liquid Rocket Engine (with 75 kN of thrust) and in the frame of a global enlargement of competence in the field of turbomachines for liquid rocket propulsion systems, Institute of Space Propulsion of the German Aerospace Center (DLR; in German, Deutsches Zentrum für Luft- und Raumfahrt), in Lampoldshausen, and the Brazilian Institute of Aeronautics and Space (IAE; in Portuguese, Instituto de Aeronáutica e Espaço) have managed to produce its first flight ready components for pumps in liquid rocket propulsion systems. Among these components was a series of prototyped shrouded impellers for the oxidizer pumps manufactured in different materials and by different fabrication processes executed by four independent Brazilian and German workshops. Non-destructive and destructive testing methods have been applied for impellers materials validation, and for manufacturing processes verification. A special attention was given to the spin tests results and analysis, which included verification at maximum operational speed and burst testing, in order to determine the failure speed. Each tested impeller reached the required specification for the application in the L75 turbopump. Spin test logic and test results are discussed later on. Therefore, the scope of the present study is to investigate several traditional and cutting-edge processes applied for shrouded turbopump impellers manufacturing. A verification and validation of these processes will also be discussed.
Highlights
Liquid rocket engines are normally designed for a high combustion pressure, typically around a hundred bar, and for some types and cycles of propulsion systems far higher than this
The 718 nickel superalloy was used in the impellers manufactured by additive layer manufacturing (ALM) process, due to its very high strength, good mechanical properties at cryogenic temperature, well-known behavior in high speed rotational parts application, mostly in turbopump components, and the ALM pre-developed construction parameters
Three of type C and two of type D impellers have been tested, but only one curve is shown for clarity in each case, because excellent agreement between the different tests could be found for average expansion over rotational speed
Summary
Liquid rocket engines are normally designed for a high combustion pressure, typically around a hundred bar, and for some types and cycles of propulsion systems far higher than this. Study of Manufacturing Processes for Liquid Rocket Turbopump Impellers: Test and Analysis 013//1144 shroud which closes the flow channels to the casing side. This design provides a well ducted flow of the fluid. The 718 nickel superalloy was used in the impellers manufactured by ALM process, due to its very high strength, good mechanical properties at cryogenic temperature, well-known behavior in high speed rotational parts application, mostly in turbopump components, and the ALM pre-developed construction parameters. The main requirements that the manufacturing processes of high-speed pump impellers shall meet are dimensional tolerances, material properties and integrity, chemical and mechanical homogeneity, surface finishing, internal stress, mass balancing, cost, and lead time.
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