A Stirling engine for use with lower quality fuels

• Effect of combustor gas temperature on original GPU-3 is analyzed.
• Increasing the heater surface area allows the system to produce more power.
• There is an engine swept volume that maximizes system efficiency.
• Multiple cylinder engines can achieve higher efficiencies than single cylinder ones.
• Adding combustion gas recirculation improves system efficiency.

A Stirling engine for use with lower quality fuels was designed. The design is a derivative of the GPU-3 (ground power unit-3), modified to be used with a lower combustion gas temperature (900 °C). It is to be used in a generator set producing 5 kWe. The engine model used is based off of the ideal adiabatic model with decoupled loss mechanisms. Single-cylinder and two-cylinder engines were analyzed using a preheater and CGR (combustion gas recirculation). The analysis shows that the external surface area of the heater plays a very important role in determining the system performance. Maximum system efficiency was found by significantly increasing the surface area at the expense of increased dead volume. A single-cylinder configuration was found to offer the best combination of system efficiency (23.6%) and manufacturing cost.