Autoignition study of tetralin in a rapid compression machine at elevated pressures and low-to-intermediate temperatures

Tetralin (1,2,3,4-tetrahydronaphthalene) is a naphtheno-aromatic compound found in diesel fuels and a candidate component widely used in diesel surrogates. The fundamental understanding of the autoignition characteristics of tetralin is meager due to the lack of experimental and computational studies in the literature. Considering this, an experimental study using a rapid compression machine (RCM) has been conducted to investigate the ignition characteristics of tetralin at varying pressures from 15 bar to 50 bar, temperatures between 762 K and 950 K, and equivalence ratios of ϕ = 0.5 and 1.0. The effect of dilution on ignition delay times was also studied by varying the initial concentrations of oxygen and tetralin independently. Furthermore, the test conditions investigated in the current study were designed to provide ignition delay measurements complementary to the literature data. A comparison of the ignition delays measured from the current study with those existing in the literature demonstrated consistent trends and good agreement. Examination of the RCM pressure histories showed that while tetralin does not exhibit two-stage ignition behavior, some evidence of pre-ignition heat release was noticed at the low temperature conditions investigated in the study. Further comparison with experimentally measured ignition delays of n-butylbenzene was conducted to demonstrate the effect of molecular structure on the autoignition properties. Chemical kinetic simulations carried out to assess the performance of an available kinetic model showed this model to be significantly less reactive than the experiments. Brute force sensitivity analyses and reaction pathway analyses were further conducted at varying pressures, temperatures, and equivalence ratios to identify the controlling chemistry. Possible reasons for the poor performance of this chemical kinetic model in predicting the experimental ignition delays have been discussed based on experimental results and chemical kinetic analyses from the current study.