Lean flammability limit of high-dilution spark ignition with ethanol, propanol, and butanol

Abstract

Ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and sec-butanol are six potential carbon-neutral fuels of the future. One application of these carbon-neutral fuels is in high-dilution spark ignition. To understand the potential of these fuels in high-dilution spark ignition, this work experimentally determines the spark ignition lean flammability limit of each fuel with no external, cooled exhaust gas recirculation (EGR), and with 20% external, EGR. The spark ignition lean flammability limit in this work is defined as the excess-air ratio that results in a coefficient of variance of gross indicated mean effective pressure greater than 5%. This is done on an engine with a compression ratio of 12.5, using an intake pressure of 1 bar and an intake temperature of 320 K. It was found that ethanol had the leanest lean limit, due to its high flame speed, followed by n-propanol, isopropanol, and sec-butanol, which all had similar lean limits. n-Butanol and isobutanol had the richest lean limits due their high knock propensity and low flame speed, respectively. The lean limit of each fuel decreased with external, cooled EGR addition, with ethanol as the least sensitive and isopropanol as the most sensitive to EGR addition. Overall, using a high dilution strategy increased the cycle efficiency for each fuel. Ethanol, n-propanol, isopropanol, and sec-butanol all showed promising performance and are great candidates to be combined with an advanced high-dilution SI strategy to enable high-dilution SI with a carbon-neutral fuel.

An Experimental Investigation into the Performance and Emission Characteristics of a Gasoline Direct Injection Engine Fueled with Isopropanol Gasoline Blends

“…In a study conducted by Gainey and colleagues [25], they examined how isopropanol behaves in a gasoline engine when running on a lean-burn mixture. The findings indicated that, under specific conditions of an inlet pressure of 1 bar and an inlet temperature of 320 K, the lean-burn limit was extended to an excess air ratio (λ) of 1.6.…”

Effect of injection and ignition timing on a hydrogen-lean stratified charge combustion engine

“…16,17 Although lean burn can improve the thermal efficiency of SI engines, the lean limit could not be simply extended due to combustion stability. 18,19 Stratified charge combustion (SCC) is a valuable strategy for extending the lean limit of SI engines with stable operation. 20 However, a large amount of particulate matter (PM) is generated when SCC is applied due to the heterogeneity of fuel mixtures, particularly rich fuel mixtures.…”

A methodology to study the interaction between variable valve actuation and exhaust gas recirculation systems for spark-ignition engines from combustion perspective

“…Zhao et al [29] used hydrogen enrichment in the EGR gases as well as isobutanol-gasoline blends as means to overcome the negative effect of EGR on combustion duration and stability, reaching positive results both from thermal efficiency and exhaust emissions perspective. Gainey et al [30] also showed that alcohol-based fuels can help to improve EGR tolerance.…”