There has recently been a large increase in development activities of remotely-controlled and autonomous miniature aerial vehicles (MAV). Military, scientific, law enforcement and mapping usage are among the important potential applications that motivate this effort. Another promising area is remote observation of hazardous environments which are hard or inaccessible to ground vehicles. Among the more severe limiting factors of the MAV development are the engine thermal efficiency and its performance degradation at high altitudes.
In this work we propose a unique method to extend the upper-limit altitude with no noticeable extra weight. We propose a special in-cylinder steam reforming approach to significantly increase the engine efficiency at high altitudes, thus allowing engine operation at higher altitudes with a negligible weight penalty. The gain in the engine performance at high altitude is attributed to the present unique method of internal heat recovery (in-cylinder steam reforming) by which a wider flammability and higher burning velocity are achievable. In the present research we analyze the effect of the in-cylinder steam reforming process on the engine performance at high altitude. The results of the research show that by the employment of the internal steam reforming concept in internal combustion engines (in either 2- or 4-stroke engines), it is possible to increase the indicated efficiency and engine brake power and therefore decrease the fuel consumption. Moreover, due to the higher in-cylinder pressure without an increase in the temperature, the cycle effectiveness is higher while keeping the same amount of NOx emission.