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 (k). 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 (k = 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 nonoxygenated (isooctane) and oxygenated fuels (MTBE and TAEE).

The Optimization of The Relationship between Octane Number of Gasoline-Ethanol Blend Fuels in Various Settings of The Engine Control Module

“…The ethanol added to gasoline improves the combustion process, reduces the combustion duration, reduces the ignition delay, and speeds up the flame front propagation 11) . The flame propagation rate of ethanol and the ethanol-gasoline blend is higher than non-oxygenated fuels in all engine compression ratios 16) . Fuel with higher burning speed needs smaller advancements of ignition timing.…”

“…Engine performance is affected by several factors, including engine operating conditions, engine design, and the properties of fuel/air mixture 16) . Among those factors, spark timing is the main parameter to be controlled to optimize engine performance (fuel economy, torque) 18) .…”

“…This is caused by spark timing gasoline which is limited by knocking. Different opinions expressed by Pedro Mello et al (2014) which stated that the addition of ethanol mixed with gasoline need to delay the ignition timing to avoid knocking because of its higher speed flame propagation compared to gasoline. By reversing ignition timing, it will reduce the tendency for detonation to occur, but at the same time reduce power output and fuel efficiency 16) .…”

“…Different opinions expressed by Pedro Mello et al (2014) which stated that the addition of ethanol mixed with gasoline need to delay the ignition timing to avoid knocking because of its higher speed flame propagation compared to gasoline. By reversing ignition timing, it will reduce the tendency for detonation to occur, but at the same time reduce power output and fuel efficiency 16) . To get the highest efficiency with the use of a high percentage of ethanol content in the mixture of ethanol-gasoline fuel, retarding the spark ignition timing has to be done.…”

An air-standard finite-time heat addition Otto engine model

“…The heat addition is modelled by a cumulative heat release function of time – an input parameter – that can approximate or be matched to results of more advanced combustion simulations, 7 thus capturing its energetic signature, while keeping the analysis within the realm of pure substance, classical, undergraduate thermodynamics. Thus, the finite-time Otto model is able to reproduce some real engine performance traits.…”