Determining the Effect of Material Properties on Operating Temperatures of Fiber Reinforced Internal Combustion Engine Poppet Valves

Internal combustion engine poppet valves operate in extreme conditions. These extreme conditions are a result of the high temperatures in the combustion chamber. Especially in Motorsport applications, the high temperatures have led to the development of exotic metallic alloys that can operate in this environment. One key problem in developing materials for poppet valves is that it is necessary to know the temperature at which they operate. This is increasingly important when developing valves from alternative materials such as fiber reinforced composites. Composite engine valves have the potential to produce substantial increases in engine performance, through substantial weight reductions, if they can be designed to withstand the environment. Research to-date has demonstrated the functionality of fiber reinforced composite intake valves that are significantly lighter than metallic valves; however, composite valve surface temperatures seem higher than expected. Using measurements of standard steel valve temperatures and engine heat transfer correlations, thermal simulations have been used to predict the operating temperatures of composite valves. These predictions have been made using measured thermal conductivities of the composite materials currently being investigated to produce composite valves. Simulations were also performed on composite valves with conductive coatings to evaluate the relative effects of using an insulating thermal barrier coating versus conductive coatings. The simulations have been compared to actual composite valve temperature measurements. It has been determined that to extend the useable temperature range of composite intake valves it is most effective to increase the valve face conductivity to help extract heat.