Optical measurements of injection and fuel mixing in a dual-fuel internal combustion engine and a constant volume chamber

Abstract

Due to the need to reduce greenhouse gases and prevent global warming, alternative solutions for internal combustion engines are being developed. Since electric engines cannot fully replace internal combustion engines in certain transportation sectors, this thesis explores dual-fuel combustion as a promising alternative. Two experimental investigations were conducted: Dual-Fuel Combustion Experiments at Brunel University A single-cylinder optical dual-fuel engine was used to study the effects of injection timing and fuel quantity on combustion. High-speed imaging captured flame area, ignition delay, and cycle-to-cycle variations. Results showed that a split pilot fuel injection creates an initial flame front, which efficiently ignites the subsequent pilot and main fuel injections, thereby reducing the required Diesel quantity. However, this approach exhibited significant variability in the initial flame formation, attributed to random flame locations, while variations in swirl speeds affected the later combustion stages. Pilot Spray Characteristics and TWIN Nozzle Geometry at Woodward L’Orange Spray experiments in a Constant Volume Chamber examined how TWIN nozzle geometry influences spray penetration, angle, and area. The results indicated that spray hole diameter and distance are the primary factors affecting spray characteristics, while the relative spray hole angle plays a role mainly under low-pressure, short-duration conditions. By comparing the experimental data to established spray penetration formulas, modifications were recommended to better predict the behavior of TWIN nozzles. The findings contribute to a deeper understanding of dual-fuel combustion and nozzle design, paving the way for future studies on optimizing initial flame front formation with premixed main fuel and minimal pilot fuel, as well as exploring additional geometric parameters of TWIN nozzles.