Experimental Studies of the Effect of Ethanol Auxiliary Fueled Turbulent Jet Ignition in an Optical Engine

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Experimental Studies of the Effect of Ethanol Auxiliary Fueled Turbulent Jet Ignition in an Optical Engine

Feng, Dengquan / Zhao, Hua / Bureshaid, Khalifa / Bunce, Mike / Shimura, Ray

Internal combustion (IC) engines are widely used in automotive, marine, agricultural and industrial machineries because of their superior performance, high efficiency, power density, durability and versatility in size and power outputs. In response to the demand for improved engine efficiency and lower CO2 emissions, advanced combustion process control techniques and more renewable fuels should be adopted for IC engines. Lean-burn combustion is one of the technologies with the potential to improve thermal efficiencies due to reduced heat loss and higher ratio of the specific heats. In order to operate the IC engines with very lean air/fuel mixtures, multiple turbulent jet pre-chamber ignition has been researched and developed to extend the lean-burn limit. Turbulent Jet Ignition (TJI) offers very fast burn rates compared to spark plug ignition by producing multiple ignition sites that consume the main charge rapidly. In this research, studies were carried out on the ignition and combustion characteristics of pre-chamber ignition produced by a Mahle TJI unit installed in a single-cylinder engine with optical access. In particular, this article focuses on the spatial and temporal formation of multiple jet sites in the main chamber by simultaneous high-speed combustion imaging and instantaneous pressure measurements in both the pre- and main chambers. This investigation includes the following: (1) the effects of fuel properties (gasoline vs. ethanol), (2) pre-chamber ignition without and with fuel injection, (3) quantity of pre-chamber fuel and its injection timing, and (4) spark ignition timing. The results show that by increasing the fuel injected in the pre-chamber, the pre-chamber pressure rises faster to a higher peak value and produces greater pressure differential between the pre-chamber and main chamber. Increasing pre-chamber pressure causes the jets to travel deeper into the main chamber and the ignition sites become bigger. The injection timing has less effect on combustion stability. Ethanol exhibits less cyclic variation and faster combustion than gasoline in all operations.