Role of Volatility in the Development of JP-8 Surrogates for Diesel Engine Application

Abstract

Surrogates for JP-8 have been developed in the high temperature gas phase environment of gas turbines. In diesel engines, the fuel is introduced in the liquid phase where volatility plays a major role in the formation of the combustible mixture and autoignition reactions that occur at relatively lower temperatures. In this paper, the role of volatility on the combustion of JP-8 and five different surrogate fuels was investigated in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT is used to determine the derived cetane number (DCN) according to ASTM D6890. The surrogate fuels were formulated such that their DCNs matched that of JP-8, but with different volatilities. Tests were conducted to investigate the effect of volatility on the autoignition and combustion characteristics of the surrogates using a detailed analysis of the rate of heat release immediately after the start of injection. In addition, the effect of volatility on the spray dynamics was investigated by Schlieren imaging in an optical accessible rapid compression machine (RCM), and the imaging data supported the conclusion made in the IQT tests. Furthermore, apparent activation energies of JP-8 and surrogate fuels were determined based on the chemical delay periods, which could be considered as a new parameter for developing surrogate fuel.

From fundamental study to practical application of kerosene in compression ignition engines: An experimental and modeling review

“…IQT, FIT, CVCC, and engine experiments 56,65,66,81–84 complement the shock tube and RCM experiments as the effects of kerosene’s physical properties on autoignition are taken into consideration. It should be noted that the IQT and FIT experiments were done in accordance with ASTM D6890 and ASTM D7170 standards, respectively.…”

“…51,70,85,154 The second class of surrogate was a surrogate that could emulate both the chemical and the physical properties of kerosene. 82,85,156–159…”

“…Table 3 shows a compilation of the latest as well as significant kerosene surrogates from the literature, the number of species and reactions in their respective reaction mechanisms, as well as the target properties that each surrogate was made to emulate. 45,51,56,68–70,82,85,154–156,158,161,163–186…”

“…66,67 In addition to having a better understanding of kerosene's autoignition characteristics, data gathered from autoignition studies is crucial in aiding the development of kerosene surrogates and their reaction mechanisms. 45,46 Autoignition studies from the literature 45,46,48,56,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] mainly investigate the ignition delay times of kerosene using different equipment such as shock tube, RCM, FIT, IQT, CVCC, and even singleand multi-cylinder engines. Of all the aforementioned equipment, the shock tube and RCM are meant to test only the chemical ignition delay as the investigated fuel is fully vaporized prior to ignition.…”

“…On the contrary, the IQT, FIT, CVCC, and engine take into consideration both the chemical and the physical delays because fuel spray is involved. Table 2 shows a compilation of the different kerosene autoignition studies 45,46,48,56,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] carried out under different conditions with varying temperatures (T), pressures (P), equivalence ratios (j), ambient densities, and levels of oxidizer. From Table 2, it can be seen that all of the studies investigated the autoignition characteristics of Jet-A, Jet A-1, and JP-8 except for one study done by Zhang et al 45 which focused on RP-3.…”