Low Temperature Combustion (LTC) Optimization and Cycle-by-Cycle Variability Through Injection Optimization and Gas-to-Liquid (GTL) Fuel-Blend Ratio

Abstract

The advent of common rail technology alongside powerful control systems capable of delivering multiple accurate fuel charges during a single engine cycle has revolutionized the level of control possible in diesel combustion. This technology has opened a new path enabling low-temperature combustion (LTC) to become a viable combustion strategy. The aim of the research work presented within this paper is the understanding of how various engine parameters of LTC optimize the combustion both in terms of emissions and in terms of fuel efficiency. The work continues with an investigation of in-cylinder pressure and IMEP cycle-by-cycle variation. Attention will be given to how repeatability changes throughout the combustion cycle, identifying which parts within the cycle are least likely to follow the mean trend and why. Experiments were formulated to include rail pressure, injection settings of single injection and split-injection of varying dwell times. All injection conditions were phased across several crank-angles to demonstrate the interaction between emissions and efficiency. These tests are then repeated with blends of 30% and 50% gas-to-liquid (GTL)-Diesel blends in order to determine whether there is any change in the trends of repeatability and variance with increasing GTL blend ratio. Compression-ignition has been traditionally regarded as sufficiently stable that such investigation is irrelevant. Major improvements have been made, however, both to the understanding of compression-ignition and its control. Re-assessing and investigating how pressure repeatability fluctuates over the combustion cycle, especially in atypical engine conditions will help our understanding of combustion and facilitate a more accurate optimization of the combustion process.