Development of Low-Temperature Difference Stirling Engine
Fujio TODA* Shoichi IWAMOTO** Makoto TAKEUCHI***
Stirling engine can be operated by many kinds of heat sources other than fossil fuel. Low temperature heat sources of solar radiation, biogas, geothermal and exhaust heat energies can be utilized. The authors first designed and developed a low temperature difference Stirling engine which can generate 300W of shaft power with heat source of 100℃. And we developed a low temperature difference Stirling engine which can generate 1kW of shaft power with thermal ratio of 0.8. These engines were designed on the basis of quasi steady flow model.
As a result, it is confirmed that the maximum brake power of 741W/174rpm was obtained on the experimental engine under the condition of higher heat source temperature of about 135℃, buffer pressure of 0.8MPa.
Key Words: Stirling Engine, Engine Performance, Energy Saving, Natural Energy
1 . INTRODUCTION
The Stirling engine can be used in the wide temperature range of heat energies from high temperature to low temperature. Such as exhaust heat and natural energies (solar heat, geothermal, hot spring heat etc.). In recent years, energy saving and environmental protection are serious subjects in global scale. It is very important to develop the technology which obtains power by using these kind of heat energies.
The authors designed and manufactured γ type low temperature difference Stirling engines for the practical study ,. These engines were operated to get data and information for simulations and performance predictions. Based on these basic researches, the engine type has been changed from the γ type to a unique α type which is specialized for low temperature difference engine. This paper describes the performance characteristics of the γ type low temperature difference Stirling engine performance prediction and engine performance examination results by raising the buffer pressure on the 1 kW α type low temperature difference Stirling engine.
2. TRIAL MANUFACTURING OF ENGINES
2.1 300W Class Low Temperature Difference Stirling Engine
1) Structure of Engine.
Figure 1 shows 300W class low temperature difference Stirling engine, and table 1 shows the specifications. This engine is a γ type engine composed of power piston and displacer and flywheel. The bore of the displacer piston is 800mm, and stroke is 80mm. Considering weight and adiabatic requirements, the material was made of foamed polyurethane. To apply the pressure to the engine inside of the low temperature difference Stirling engine is a feature of this engine for the first trial. Working gas is pressurized to get higher output power. By this concept, epoch-making result was obtained in the performance of the low temperature difference Stirling engines.