Hydrogen Enriched Compressed Natural Gas (HCNG) as an Alternative Fuel for Conventional IC Engines. A Review

The continuous increasing demand of alternative energy and various stringent emission norms have led the engine researchers to develop strategic plans for the appropriate usage of available energy and reduce the carbon emission of fuels. Moving ahead with these plans, hydrogen has emerged as one of the promising energy carriers amongst the gaseous fuels but technical limitations restrict its uses. In this regard, hydrogen enriched compressed natural gas (HCNG), also called hythane, has been emerged as an attractive energy carrier for internal-combustion engines. Worldwide many countries are endeavoring hard to lower down the emission level by promoting HCNG-fueled gasoline vehicles. It has been observed that under precise circumstances, the indicated thermal efficiency of the HCNG engine is much better compared to CNG engines with identical emissions. In spite of that the H, enrichment to NG/CNG provides increased NO,, it can be reduced with the application of lean burn combustion concept and also using three-way catalytic (TWC) converter. This review is an overview of HCNG engines and provides a detailed discussion on the fundamentals of characteristics of HCNG mixture, engine combustion and emissions. For covering the prospects of the HCNG engines, various approaches are discussed along with methods to increase the power output, thermal efficiency, and emissions reduction along with gaseous fuel induction strategy.