Testing Composite Valve Covers for Reciprocating Engine Applications

Abstract

Theuse of composites within the aeronautical field is not limited to airframeapplications and includes powerplant components in reciprocating engines. Toadd to the research body in this area, the presented work aimed to evaluate theperformance of novel carbon fiber valve covers installed on an aircraftreciprocating engine. Specifically, the comparative performance between novelcomposite-based valve covers and original steel valve covers was of interest,with a focus on the thermal and cooling behavior. The experimental proceduresimulated certification testing required for parts manufacturer approvalprovided by the Federal Aviation Administration and followed the cooling testprotocol outlined by ASTM International. The test engine was run once with eachvalve cover type and at multiple power settings, throughout which the surfacetemperature of the valve covers was recorded. In addition, the carbon fibervalve cover was subjected to a post-run visual inspection to identify theoverall condition thereof and any potential damage introduced under engineoperating conditions. The experimental study revealed lower temperatures withaccompanying higher cooling and heating rates for the carbon fiber valve coverwhen compared to the original steel valve cover. Moreover, sealing issues onthe carbon fiber valve cover were observed. The high heating rates coupled withthe sealing issues can have a detrimental impact on the engine operation andlifetime, thus, equivalency requirements were not met. While the novel carbonfiber valve cover did not perform at directly equivalent levels to the originalsteel valve cover, the potential for future improved performance isdemonstrated. Especially the lower temperatures sustained, the rapid coolingrate, and the weight savings associated with the use of composite materials arepromising. Moreover, the results obtained can be used to further refine thedesign of composite-based valve covers, with the ultimate goal of meetingcertification and applicational requirements.