In this study, iso-paraffinic kerosene (IPK) was analyzed for ignition delay, combustion delay, pressure trace, pressure rise rate and, apparent heat release rate in an experimental single cylinder indirect injection (IDI) compression ignition engine as well as in a constant volume combustion chamber (CVCC). Neat IPK, neat ULSD, and a by-mass blend of 50%IPK50%ULSD were analyzed in a CVCC and an IDI engine to determine the effect of Derived Cetane Number (DCN), Ignition Delay (ID), and Low Temperature Heat Release (LTHR) on combustion timing and engine knock.
In the CVCC, IPK was found to have a significantly lower DCN than ULSD at 26 and 47, respectively. The blend was found to have a DCN between the two neat fuels at 37.5. Additionally, the ignition delay increased in the CVCC from 3.56 ms for ULSD to 5.3 ms for IPK with the blend falling between the two at 4.38 ms.
For engine research, the single-cylinder experimental IDI engine was run at 2400 rpm at 5, 6, and 7 Indicated Mean Effective Pressure (IMEP) using each of the three researched fuels. It was found that when running neat IPK, there was a profound level of engine knock at all loads characterized by the 60% increase in the Peak Pressure Rise Rate (PPRR) when compared to ULSD. The pressure trace for IPK at all loads showed a significant delay in combustion due to IPK’s resistance to autoignition. This was observed in the increasing ignition delay in the engine from 0.88 ms for ULSD to 1.1 ms at 7 bar IMEP for IPK. Despite the delay in ignition for IPK, all three researched fuels reached peak Apparent Heat Release Rate (AHRR) at approximately 370° leading to a much more rapid increase in AHRR for IPK when compared to ULSD. This steep slope in the AHRR, also seen in the increased PPRR, and longer ID caused the high levels of engine knock, observed as oscillations in the pressure trace which decreased in magnitude as IMEP increased.