Progress in hydrogen enriched compressed natural gas (HCNG) internal combustion engines - A comprehensive review

With the huge growing demand of energy utilization and various threats posed due to the emissions had substantially led the thinkers to put on strategic plans to decrease the usage of energy and reduce the carbon contents of fuels. Moving ahead with these plans hydrogen enriched compressed natural gas (HCNG) engines have emanated as a forthcoming energy carrier for internal-combustion engines. Several nations are endeavoring hard to bring down the pollution level by promoting hydrogen enriched compressed natural gas-fueled vehicles, predominantly by powering medium and heavy transportation vehicles. In general, under precise circumstances the indicated thermal efficiency of the HCNG engine is much better than CNG engines without tolerating the high level of harmful emissions. In spite of that the hydrogen addition to NG provides increased NOx, emission because of a great amount of heat generation inside the combustion chamber. However, it can be overcome by some extent of the application of lean burn combustion or with three-way catalyst (TWC). This report presented an encyclopedic overview of hydrogen enriched compressed natural-gas engines. This paper provides a detailed discussion on the hydrogen generation methods, fundamentals of characteristics of HCNG mixture, refinements on different fuel mixture affecting the combustion. For covering the prospects of the HCNG engines, its technical and numerical approaches are discussed. Furthermore, various methods are discussed which increase the power output and thermal efficiency along with a check on the emission parameters. An exploration of HCNG vehicle's demonstration projects worldwide is a key feature of this article.