Abstract

Carbon dioxide is one of the leading contributors to global warming. Oxy-fuel combustion (OFC) integrated with Carbon Capture and Storage (CCS) technology is an efficient way to reduce carbon dioxide emissions. In OFC, pure oxygen is used instead of air to react with hydrocarbon fuel. Consequently, the products of combustion mainly include CO2 and water vapor (H2O) under lean conditions. Meanwhile, due to the absence of N2 in the intake charge, nitrogen-related emissions such as NOx are greatly removed from the exhaust gases. In the present study, the effect of intake charge temperature on OFC has been investigated in a diesel engine under the Homogeneous Charge Compression Ignition (HCCI) mode. In order to control combustion temperature and avoid overheating problems caused by pure oxygen in OFC, a portion of the exhaust CO2 was added to the oxygen. For this purpose, different CO2 dilutions ranging from 79-85% have been employed. It has been found that OFC can significantly reduce CO and PM emissions while eliminating NOx emissions. With a higher intake charge temperature, combustion occurs earlier with shorter main stages, reducing the Indicated Mean Effective Pressure (IMEP) and increasing the Indicated Specific Fuel Consumption (ISFC), whereas, with a lower intake charge temperature, combustion stability deteriorates leading to incomplete OFC. By raising the intake charge temperature from 140°C to 220°C and applying 21% O2 and 79% CO2 v/v, the Indicated Thermal Efficiency (ITE) is increased by 34.6%. However, ISFC is adversely affected by 18%.