Application of an innovative system for recovering and storage of cold energy from regasification of LNG when feeding heavy-duty truck engines

Liquefied Natural Gas (LNG) is becoming progressively attractive as a sustainable alternative fuel for heavy-duty vehicles and its share is expected to grow in the near future. Compared to diesel fuel, indeed, it is more environmentally friendly and has a lower cost per kWh. On board heavy-duty vehicles, LNG is stored in cryogenic vessels and needs to be vaporized (re-gasified) before being injected into the engine, which makes available a significant amount of cold energy. In this paper, the authors present their patented innovative system aimed at recoverying the cryogenic energy from the LNG vaporization upstream the engine injection. The main feature of the proposal is the possibility of storing the cold energy and using it at a later moment. The different possible ways of cold energy recovery are illustrated. Among them, the potential improvement in engine performance is calculated and discussed. Referring to a commercial 240 kW truck engine, simulated by a home built code, the limit cycle was reconstructed by the manufacturer performance data. Then, an aftercooler downstream the intercooled compressor was applied to exploit the cold energy available from the LNG re-gasification. Due to the cold energy storage, the aftercooling can be performed when needed, being independent from the LNG use. The calculations showed the very interesting potential of engine power boosting into the range of 10 - 15% which, thanks to the storage, may be exploited when the traffic and road conditions make it more convenient. Also a modest reduction in specific energy consumption of the engine was calculated.