Understanding the effect of Intake temperature on the φ-sensitivity of toluene-ethanol reference fuels and neat ethanol

The low-temperature combustion (LTC) is an attractive concept that enables the modem combustion engines to move toward sustainability mainly by increasing the efficiency and decreasing the emissions. The modern combustion engines which are working based on the LTC concept have specific fuel requirements. Fuel phi-sensitivity is a key factor to be considered for tailoring fuels for these engines. Fuel with a high phi-sensitivity are more responsive to thermal or fuel stratifications; the auto-ignition properties of different air-fuel mixtures of these fuels, with different equivalence ratio (phi), are more diverse. This diversity provide a smoother heat release rate in stratified condition. In this study 11 different toluene-ethanol reference fuels (TERFs) in three research octane number (RON) groups of 63, 84, and 105 together with neat ethanol are evaluated. The Lund phi-sensitivity method is used to evaluate these fuels in a cooperative fuel research (CFR) engine. The effect of variation of intake temperature on pressure sensitivity of fuel at a constant combustion phasing is evaluated. This evaluation is performed at two intake temperature of 373 and 423 K, and the results are compared with the outcome of the Lund phi-sensitivity number with the intake temperature of 323 K. This study shows that the CR sensitivity response of different blends to the intake charge temperature variation depends on the fuel composition. Accumulated low temperature heat release and latent heat of vaporization. It proves that the fuel phi-sensitivity will vary under different thermodynamic conditions. There was a clear link between the accumulated heat released during the early reaction and CR sensitivity of the blends at different intake temperature of 373 and 423 K but the link with the latent heat of vaporization (HoV) found to be inexplicit.

Automated summary

Low-temperature combustion (LTC) is an attractive concept for sustainable modern combustion engines. This study evaluates the phi-sensitivity response of different fuel blends under different thermodynamic conditions. It also explores the link between accumulated low temperature heat release and latent heat of vaporization with the CR sensitivity of the blends.