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Biogas is one of the most promising alternatives fuel for the future. Biogas, when used in automotive field, will help to bring down harmful emissions. However, some technical improvements are still needed, especially in the Indian automotive sector. In this research work 100% biogas operated two wheeler four stroke SI engine has been tested for exhaust gas emissions. The result shows the lower emissions than the existing petrol engine limits without exhaust gas after treatment. The current work clearly indicates the breakdown of compression ratio barrier and it is shown that the engine runs smoothly at compression ratio of 11:1 without any tendency of auto-ignition. Experiments were conducted by varying compression ratios from 9:1 to 11:1 and retaining the combustion chamber design. This study shows that using biogas in SI engines, it is particularly beneficial to reach interesting conversion efficiencies with low emissions.

This paper reviews the current research work on Homogeneous Charge Compression Ignition (HCCI) concept for diesel engines to meet future tightened emission norms. Heavy duty diesel engines are facing conflict between the goal of emission reduction and optimization of fuel consumption. In response to social demands and progressively strengthened emission regulations, diesel engines have been made cleaner through various means such as the combustion chamber, high pressure fuel injection, and turbocharger. In recent years, high pressure fuel injection has been considered as an effective method to reduce Particulate Matter (PM) by improving atomization and better air utilization, however, resulting in an increased Nitric Oxides (NOx) formation due to high temperature combustion. To fulfill future tightened emission norms, further developments on diesel engine technology and combustion improvements are required for simultaneous reduction of NOx and PM emissions as opposed to a trade-off.