Internal Combustion Engine fuelled by mixture of compressed natural gas and hydrogen gas (HCNG) has a better performance and emission characteristics compare to conventional engine. The basic emission characteristics such as carbon monoxide (CO), unburnt hydrocarbon emission (UHC) reduced in a direct injection hydrogen enriched compressed natural gas engine (DI-HCNG). However, nitric oxide emission increases (NOx). The increase in NOx in direct injection hydrogen enriched compressed natural gas engine (DI-HCNG) engine is caused by high combustion temperature. Therefore, the reduction of nitric oxide (NOx) emission becomes the main target in DI-HCNG engine. Addition of exhaust gas recirculation (EGR) is a strategy to reduce this NOx emission in DI-HCNG engine. Thus, the primary objective of this research is to study the emissions characteristics of direct injection hydrogen enriched compressed natural gas engine employing EGR (DI-HCNG-EGR) at both stoichiometric and lean mixtures. The experiment was conducted at part throttle, constant engine speed (i.e. 2000 rpm) with different percentage of H2 (i.e. 0, 28, and 46% by volume) and EGR (i.e. 0, 15, 30 and 40% by mass). The results showed that for a given percentage of H2, increasing the EGR rate decreases the BsNO emission concentration for both stoichiometric and lean mixtures. While it leads to rise and fall for BsUHC emission concentrations. EGR has no significant effect on BsCO emission at lean mixtures. In addition, the result also showed that the optimum percentage of EGR that is best for basic pollutant emission control in DI-HCNG-EGR lies between 15-30%. Thus, it can be concluded that EGR is an effective strategy that can reduce the basic pollutant emission in DI-HCNG engine at both stoichiometric and lean mixture respectively.
Volume 11 | Issue 1
Pages: 60 - 67