Combustion time of the oxygenated and non-oxygenated fuels in an Otto cycle engine

Abstract

Speed flame propagation in Otto cycle engines is one of the principal characteristics of fuel and is fundamental in defining the ignition advance. The greater the propagation speed the less the negative work required to compress the mixture before the piston reaches the top dead center and the higher the cycle’s efficiency. This paper presents experimental results of time measurements of the fuel’s ignition and the maximum pressure rating in the combustion chamber of a Cooperative Fuel Research engine specially instrumented. The combustion duration measurements of oxygenated and non-oxygenated fuels were taken as a function of the compression ratio (8:1, 10:1 and 12:1) and lambda (λ). The speed flame propagation in the combustion chamber is significantly changed with the change of the lambda different compression ratios. The VNG has a maximum in the speed flame propagation in the stoichiometric region (λ = 1.0) in all compression rates in this study. Similar behavior occurs with ethanol and gasohol, but only in compression ratio 12:1. Ethanol and gasohol have the higher rate of flame propagation for all compression ratios measured as compared to the non-oxygenated (isooctane) and oxygenated fuels (MTBE and TAEE).