Executive Summary : | Diesel engines are widely used for power generation and transportation applications because of their high fuel efficiency and are likely to be used for commercial transportation for decades to come. However, diesel engines can cause environmental pollution owing to their high NOx and soot emissions. In normal CI engine combustion, diesel is sprayed in a combustion chamber at high pressure. The combustion initiates at high local equivalence ratio and during combustion in the local rich mixture zone, soot is formed. The soot further mixes with air and starts oxidation in the outer lean zone and this condition is favourable for high NOx emission. Due to this type of combustion occurring at both high and low equivalence ratios, a high amount of NOx and soot are formed. If the entire combustion happens at a low equivalence ratio and low temperature, the NOx and soot emissions can be reduced. This is the basis of Low Temperature Combustion (LTC) in diesel engines. One of the most prominent LTC strategy is RCCI (Reactivity Controlled Compression Ignition) which has potential to control the combustion process and reduce the fuel consumption and emission without the need of after-treatment methods. RCCI is a dual fuel combustion technology which allows to control fuel reactivity in cylinder by appropriately choosing the reactivities of the fuel charges, their relative amounts and timing and therefore, combustion can be tailored to achieve optimal fuel efficiency at low temperatures (for NOx reduction) with controlled equivalence ratios (for soot reduction). Researchers used CNG/ethanol/methanol as low reactivity fuels and diesel/biodiesel as high reactive fuels, giving an excellent opportunity to operate the engine in the RCCI combustion range. CNG is sustainable and easy to integrate in the RCCI as well as CDF (Conventional Dual Fuel) combustion. However further investigation is required to integrate RCCI and CDF combustion in existing diesel engine for wide operating range using CNG-Diesel fuels. The present research aims to develop a unified RCCI-CDF combustion strategy for heavy-duty diesel engine to reduce emission levels and improve performance at all load conditions. The fundamental insights gained from this project will contribute to developing a new-age CI engine running with renewable fuel with modern combustion strategies. |