Narrow-Throat Pre-Chamber Combustion with Ethanol, a Comparison with Methane

Combustion Characteristics of Ethanol as Main Chamber Fuel with Methane-fueled Pre-chamber Fahad Amer Almatrafi Pre-Chamber combustion systems are gaining popularity in Internal Combustion Engines (ICE) with the increasing emissions regulations due to their advantages in improving fuel economy by increasing the lean limit and cutting emission, especially NOx. In pre-chamber Combustion, flame jets shoot out from the pre-chamber orifices into the main chamber and generates several ignition points that promote a rapid burn rate of the lean mixture (air-excess ratio (λ) >1) in the main chamber. This work focused on studying two different fuels in the main chamber, lean limit, combustion efficiency (ηc), and emissions. A single-cylinder heavy-duty engine equipped with a narrow throat active pre-chamber was used. Two fuels were tested in the main chamber, Methane (CH4) and Ethanol (C2H5OH), the first fuel is used as a baseline, while keeping the pre-chamber fueled by Methane only. The engine was operated at a fixed speed, intake pressure, and spark-timing. The amount of fuel injected was varied to attain different global λ, then at each global λ; the amount of fuel injected to the Pre-chamber was varied to observe the effect of the pre-chamber λ. Different air intake temperatures were tested to see the effect on combustion efficiency. Results from the study showed an increase in the lean-limit using Ethanol in the main chamber compared to using only Methane in both chambers. However, lower ηc than that of the Methane was reported; this is due to a combination of the narrow-throat feature and the high heat of vaporization of Ethanol, ηc showed improvement when the air intake temperature increased.