Research Projects

Low-Temperature Combustion (LTC) engines emit very low soot and NOx as they burn a major part of injected fuel in premixed phase with good mixing before ignition. The newest addition to LTC engine technology is Gasoline Compression Ignition (GCI). The GCI engine uses increased ignition delay of low octane/ low cetane fuels to achieve superior charge formation and higher premixed heat release, reducing soot and NOx emissions while enhancing overall engine efficiency. Higher HC and CO emissions accompanied by combustion instability and cold-start problems have dampened the commercial adaptation of this technology. Researchers have blended diesel and gasoline to achieve low octane, low cetane test fuel. The high miscibility of gasoline in the air and its higher ignition delay produce overmixed lean regions. This issue is severe at low loads as the wall and charge temperatures are low, increasing the ignition delay and increasing the HC and CO emissions. The fuel injected at the end of injection has low momentum causing a lean mixture near the nozzle, which is hard to auto-ignite. This also contributes to HC and CO emissions. Theoretically, a low octane and cetane fuel with a lower sensitivity index, broad flammability index, wider distillation curve with inherent fuel oxygen, and superior mixing characteristics can resolve this issue. In this project, these challenges will be resolved with the help of alternate oxygenated low-carbon fuels, namely Methanol and di-ethyl ether (DEE) in Compression Ignition (CI) engines. DEE has a high cetane number, high oxygen content, low autoignition temperature, extended flammability limits, and moderate energy density compared to baseline diesel. Methanol being high octane and less volatile than gasoline can reduce the overmixing phenomenon. We propose using Methanol/DEE blend to address the over-mixing and autoignition challenges in GCI-LTC engines. Operating an engine in LTC mode over a wide range requires understanding fuel-air mixing and ignition in engine-relevant conditions. It is understood from the literature that octane number alone doesn’t affect ignition and flame propagation. It is affected by the fuel’s physical and chemical properties and ambient conditions. We propose to develop an ultra-clean methanol/DEE-fueled CI engine operating in LTC mode. Optical visualisation investigations in a customised Constant Volume Combustion Chamber will support the engine development. The Methanol/DEE blend spray and flame in engine-relevant conditions will be investigated. This project will analyse the effect of properties such as latent heat, distillation temperature, flammability limits, and autoignition temperature on ignition and flame propagation. These experiments and 3-D simulations will help develop injection strategies to operate the engine in LTC mode in different operating conditions.