Determination of Range of Fuel Premixing Ratio in Compression Ignition Engine for Lower Exhaust Emissions and Higher Efficiency

In this study, the influence of fuel premixing ratio (PMR) on the performance, combustion and emission characteristics of dual fuel operation in compression ignition (CI) engine has been investigated. For dual fuel operation in CI-engine, two fuels of different reactivity are utilized in the same combustion cycle. In this study, low reactivity fuels such as gasoline/butanol is injected into the intake manifold and high reactivity fuel (diesel) is directly injected into the cylinder. To operate the conventional CI engine in dual fuel mode, the intake manifold of the engine was modified and a solenoid based port fuel injector was installed. A separate port fuel injector controller was used for injecting the gasoline/butanol. Suitable instrumentation was used to measure the in-cylinder pressure and exhaust gas emissions. Experiments were performed by maintaining the constant fuel energy at different fuel PMR for different engine loads at constant engine speed. The influence of fuel PMR on combustion pressure, heat release rate, and coefficient of variance (COV) in indicated mean effective pressure (IMEP), brake thermal efficiency (BTE), combustion duration, and gaseous emissions were investigated at different engine loads. The main objective of present study is to determine the range of fuel PMR and best possible fuel PMR for gasoline/butanol-diesel dual fuel CI-engine at 25%, 50% and 100% loads. Additionally, butanol-diesel dual fuel operation is also compared with gasoline-diesel dual fuel operation for 50% engine load. The range of fuel PMR is estimated on the basis of combustion (COV of IMEP) and unburned hydrocarbon (HC) emission characteristics while best fuel premixing ratio is estimated on the basis of performance and emissions characteristics. The results demonstrate that higher thermal efficiency was achieved for specific combinations of fuel premixing ratio and NOx emission drastically reduced for both the dual fuel operations. Particle number emissions are also found lower in dual fuel operation (using gasoline and butanol) in the determined range of premixing ratio.