Rapid Compression Machine Ignition Delay Time Measurements under Near-Constant Pressure Conditions

Abstract

This work presents and validates a new methodology that determines the adiabatic ignition delay of a hydrocarbon-based fuel using several nonadiabatic ignition delay measurements. The new methodology was developed and validated in a numerical modeling and then applied to propane autoignition experiments to determine the adiabatic ignition delay of the fuel, the so-called measured adiabatic ignition delay. Propane ignition delays were measured in a wide range of low to intermediate gas temperatures ranging from 769 to 952 K, at pressures of 23–30 bar, and at equivalence ratios of approximately 0.5 and 1.0 for a rapid compression machine (RCM). Application of the new methodology removed the effect of heat transfer on measured ignition delay, thus reporting the adiabatic ignition delay free from facility heat-transfer effects. The measured adiabatic ignition delays from the RCM are close to the ones measured by a shock tube.

Measurement and Simulation of n-Heptane Mixture Autoignition

“…The slightly longer ignition delay is mainly due to the higher heat transfer rate (or higher pressure drop) during the post-compression period at the higher compression ratio, as shown in Figure . The heat transfer from the hot core gas to the cold boundary layer is a function of several factors, such as area-to-volume ratio, chamber geometry, and diluent composition. , The area-to-volume ratio is higher at the higher compression ratio; thu,s a greater heat transfer and pressure drop are expected during the post-compression period; higher pressure drop leads to a longer ignition delay.…”

“…Thus, considerable temperature drops were observed in the RCM with a flat piston compared to a creviced piston. The work of refs , showed that heat transfer leads to longer ignition delay times within RCMs at the tested conditions. A new methodology was developed to compensate for the effect of heat transfer and was used to eliminate the effect of heat transfer on the ignition delay. , …”

“…Ignition delay experiments of hydrocarbons have been performed with RCM and ST, leading to great advances in the understanding of combustion phenomena. Differences in the design and operation of these devices, however, has led to differences in the measured ignition delays at similar conditions. − These differences in the ignition delay times between RCMs and STs have been associated with heat loss from the hot core gas to the cold boundary layer (most relevant for RCMs), pressure rise at the shock tube condition, and formation of hot or cold spots during experimentation. , …”

“…A new methodology was developed to compensate for the effect of heat transfer and was used to eliminate the effect of heat transfer on the ignition delay. 2,3 The effect of temperature heterogeneities on the ignition delay of an n-heptane/methyl-cyclohexane (MCH) blend was studied experimentally by Houidi et al 9 using different optical diagnostics techniques such as chemiluminescence imaging, Schlieren imaging, and toluene planar laser-induced fluorescence (PLIF). A large temperature heterogeneity was observed using an RCM with a flat piston.…”

High-Temperature Ignition of Propane–Oxygen–Argon Mixtures in a Shock Tube at A Pressure of 30 Atm

“…Shock tubes are a traditional tool for studying various high-temperature processes, including measuring the radiation characteristics of shock-heated gases [12,13], determining the rate constants of chemical reactions [14,15], and measuring the ignition delay times in high-temperature combustible mixtures [16][17][18]. Despite the significant progress in the study of the combustion of propane under various conditions, experimental studies on the study of the characteristics of its ignition of propane are still taking place [19][20][21]. Nevertheless, the available data on ignition delay times are limited and are related to pressures less than 20 atm [2,4,22].…”