Fischer-Tropsch coal-to-liquid fuel negative temperature coefficient region (NTC) and low-temperature heat release (LTHR) in a constant volume combustion chamber (CVCC)

The purpose of the study was to investigate the correlation between thermal characteristics of neat Iso-Paraffinic Kerosene (IPK) in relation to Low Temperature Heat Release (LTHR), ignition delay, and combustion delay within the Negative Temperature Coefficient region (NTC), utilizing a Box-Behnken design matrix. There were 15 trials of 3 control input parameters which were strategic manipulations of ASTM standard D7668-14a. The standard parameters are: 1000 bar for injection pressure, a combustion chamber temperature of 595.5 °C, and an injection pulse width of 2.5 ms. It was observed that, at ASTM standard, the Derived Cetane Number of neat Ultra-Low Sulfur Diesel (ULSD) and IPK was 47.38 and 25.9, respectively. Results show that the LTHR duration and energy release were reduced when two parameters were simultaneously increased in ULSD operation. Meanwhile, for both fuels, the duration and energy release in LTHR has increased when two parameters were simultaneously reduced. It was found that the lower set wall temperature resulted in increased NTC region and LTHR increased to over 10% of the total energy release. The maximum combustion pressure for both ULSD and IPK where increased by 17.2% and 16.1% respectively from the standard due to the increase in injection pressure and pulse width.