Design and Performance Analysis of an Optically Accessible Pneumatic Poppet Valve

This paper discusses the design and testing of an optically accessible pneumatic poppet valve. In a graduate-level course titled “Propulsion Design Build Test” at Purdue University, students were tasked with designing optically accessible components for a hypergolic rocket engine experiment. As a part of this class, we designed this valve to study actuation dynamics and sealing characteristics and to gain greater insight into operational aspects of poppet valves, a common type of valve used in aerospace systems. The team designed the value to nominally operate at 500 psia with materials that are compatible with high-test peroxide. We used polycarbonate to make the valve’s casing, actuation stem, and poppet, which allowed for optical accessibility into the valve. The valve uses a hard-on-soft cone-on-cone poppet and seat configuration. The team designed the poppet and seat as modular components, enabling testing of different configurations and quick design iteration. As part of the designing process, we performed an analysis to estimate the actuation time and force margin of the valve as defined by NASA STD-5017. To characterize the valve, we determined the discharge coefficient and actuation stem friction forces experimentally. We also determined leak rates using a combination of pressure decay and pressure rise. We utilized high- speed video to determine the travel time of the poppet and to observe actuation dynamics within the valve. We were able to see cavitation associated with the opening of the valve, cavitation caused by hydraulic shock, and gain insights into the flow structures inside the valve