Deep insights of HCNG engine research in China

Hydrogen enriched compressed natural-gas has emerged to be an alternative vehicular fuel, due to its adaptability for the current CNG infrastructure. The various research laboratories of China, did a remarkable experimental/numerical research on the development of HCNG engines. A deep perusal of the performance and emission characteristic of the HCNG blends under specific conditions has been explored by these research facilities. This is proved by the series of research paper published by researchers of these laboratory. Hydrogen addition to natural gas increases the laminar burning velocity of the mixture, which will boost the combustion and reduces the brake specific fuel consumption. At an optimum excess air ratio and spark timing, the brake thermal efficiency increases while cycle-by-cycle variations significantly reduces. However, the presence of hydrogen increases the combustion temperature result in high NO_x emission. However, at optimized ignition timing and excess air ratio, higher thermal efficiency at low NO_x under the limit of emission regulation is possible. Other pollutant species in exhaust smoke like total hydrocarbon (THC), carbon monoxide (CO), and methane (CH₄) emission impressively reduces after hydrogen enrichment. These advantages of HCNG engines over CNG engines are impressive and provides an option for the betterment of environment. Apart from the laboratory research, many HCNG fueled, heavy-duty city bus demonstration projects have been successfully accomplished in various provinces of China. Presented review article not only gleams the contribution of China in the research and demonstration projects of HCNG engines, also included the studies of other HCNG research facilities worldwide.