Fuel injection strategy optimisation and experimental performance and emissions evaluation of diesel displacement by port fuel injected methanol in a retrofitted mid-size genset engine prototype

Abstract

The reliance of the transport, agriculture, marine, and power generation sectors on heavy-duty diesel engines would continue in the foreseeable future due to their higher efficiency, torque, fuel economy, and durability, despite growing concerns about emissions. This dependence would rise further due to the unavailability of an equally efficient alternative prime mover having a similar or better power density. The adoption of alternative fuels has emerged as a promising solution to tackle emission issues. Methanol has exhibited great potential to reduce pollutants by adopting advanced combustion technologies among various new fuels. Retrofitment of existing engines can be a viable solution for methanol adaptation because engine design modifications are not practical for on-field engines. The present study focused on evaluating the performance and emissions of a commercial Genset CI engine adapted to operate using diesel-methanol dual-fuel combustion (DFC) technology, which required very few hardware modifications to facilitate retrofitment for methanol adaptation. Inlet charge temperature was controlled using hot air from the turbocharger. Port fuel injection was used to induct methanol into the engine manifold, and a premixed charge entered the engine combustion chamber. This charge was ignited by spraying diesel directly into the engine combustion chamber. The engine's performance and emissions were compared with the OEM configuration (diesel fuelling mode) at methanol's low, medium, and high diesel replacement. The fuel injection parameters (injection timing and pressure) of diesel were varied to obtain optimum fuel injection strategies for various engine loads. A sharp increase in thermal efficiency was observed at 30% diesel displacement (on an energy basis) by methanol at a 9 kW generator load. In contrast, a slight penalty in thermal efficiency was observed at 80% diesel displacement (on an energy basis) by methanol. Higher HC and CO emissions were also observed for the engine using higher methanol fractions. The CO2 emission was comparable to or less than the OEM diesel configuration at identical loads. Exhaust smoke was considerably lower for methanol-fuelled operation, indicating a significant reduction in particulates in the engine exhaust. Advancing fuel injection timings and higher fuel injection pressure of diesel proved to be a good strategy for methanol adaptation in genset engines, with an acceptable cylinder noise.