Effect of Cetane Improver on Autoignition Characteristics of Low Cetane Sasol IPK Using Ignition Quality Tester1

Abstract

This paper investigates the effect of a cetane improver on the autoignition characteristics of Sasol IPK in the combustion chamber of the ignition quality tester (IQT). The fuel tested was Sasol IPK with a derived cetane number (DCN) of 31, treated with different percentages ofLubrizol 8090 cetane improver ranging from 0.1 to 0.4%. Tests were con ducted under steady state conditions at a constant charging pressure of 21 bar. The charge air temperature before fuel injection varied from 778 to 848 K. Accordingly, all the tests were conducted under a constant charge density. The rate of heat release was calculated and analyzed in detail, particularly during the autoignition period. In addi tion, the physical and chemical delay periods were determined by comparing the results o f two tests. The first was conducted with fuel injection into air according to ASTM stand ards where combustion occurred. In the second test, the fuel was injected into the cham ber charged with nitrogen. The physical delay is defined as the period of time from start o f injection (SOI) to point of inflection (POI), and the chemical delay is defined as the pe riod of time from POI to start of combustion (SOC). Both the physical and chemical delay periods were determined under different charge temperatures. The cetane improver was found to have an effect only on the chemical ID period. In addition, the effect of the ce tane improver on the apparent activation energy of the global combustion reactions was determined. The results showed a linear drop in the apparent activation energy with the increase in the percentage of the cetane improver. Moreover, the low temperature (LT) regimes were investigated and found to be presented in base fuel, as well as cetane improver treated fuels.