Energy-saving technologies of the unconventional thermal cycle internal combustion engines

Many unconventional thermal cycle internal combustion (IC) engines have been proposed which greatly enhance IC engine thermal efficiency. By reviewing some typical energy-saving technologies of the unconventional thermal cycle IC engines, two common characteristics are summarized in this paper, charger transit between cylinders and steam assistance. By using the technology of the charger transit between cylinders, a working cycle of an IC engine can be divided into several cylinders, so the compression ratio can be greatly increased, or the over-expansion cycle can be realized, both of which can substantially enhance the IC engine thermal efficiency. By using the technology of steam assistance, water can be heated and evaporated into steam by injection into hot gas or heat exchanger. The exhaust energy can be recovered when the water absorbs the exhaust heat and evaporates to perform further work, which can reduce the exhaust temperature, thereby the IC engine thermal efficiency can be enhanced. The technologies of unconventional thermal cycle IC engines provide new ideas for the development of the high efficiency IC engine technology.