Testing of a microrocket engine turbopump

Abstract

Advances in microfabrication suggest its application to rocket engines. A MEMS thrust chamber producing 50 N of thrust at design point was previously developed that requires propellants pressurized as high as 300 atmospheres. Hence the need for turbopumps at the MEMS scale. A demonstration microturbopump approximately 20x20x6mm in size was designed and built using silicon microfabrication technology. Nitrogen and deionized water are used as operating fluids in the turbine and in the pump respectively. The design speed is 750,000 RPM, with a 23 atmospheres pump pressure rise, and an overall 30% turbomachinery efficiency. This thesis addresses the key points of the turbopump design, modelling, fabrication, and testing. A 3D CFD simulation of the pump was run and performance predicted. Cavitation risk was shown to be small. A fabrication process flow was set up and continuously improved using the feedback from experiments. Non-destructive fabrication inspection methods were introduced. A test rig and a packaging were built, on which 13 turbopumps have been tested, 8 of them spinning. The maximum speed reached was 100,000 RPM without pump loading, and 65,000 RPM with pump loading. Structural concerns have been addressed. Rotordynamics issues have been investigated. Pumping tests were performed and have paved the way toward an effective pressure rise. The innovative rotor arrangement with coplanar pump and turbine was validated. Dual phase operation involving water and nitrogen as running fluids was achieved successfully.