Phenomenological Analysis of the Combustion of Gaseous Fuels to Measure the Fuel's Energy Quality and Availability to Produce Work in Si Engines, Part 2

A novel methodology is proposed to evaluate fuel´s performance in spark ignition (SI) engines based on the fuel´s energy quality and availability to produce work. Experiments used a diesel engine with a high compression ratio (CR), modified by SI operation, and using interchangeable pistons. The interchangeable pistons allowed for the generation of varying degrees of turbulence during combustion, ranging from middle to high turbulence. The generating efficiency (ηq), and the maximum electrical energy (EEmax) were measured at the knocking threshold (KT). A cooperative fuel research (CFR) engine operating at the KT was also used to measure the methane number (MN), and critical compression ratio (CCR) for gaseous fuels. Fuels with MNs ranging from 37 to 140 were used: two biogases, methane, propane, and five fuel blends of biogas with methane/propane and hydrogen. Results from both engines are linked at the KT to determine correlations between fuel´s physicochemical properties and the knocking phenomenon. Certain correlations between knocking and fuel properties were experimentally determined: energy density (ED), laminar flame speed (SL), adiabatic flame temperature (Tad), heat capacity ratio (γ), and hydrogen/carbon (H/C) ratio. Based on the results, a mathematical methodology for estimating EEmax and ηq in terms of ED, SL, Tad, γ, H/C, and MN is presented. These equations were derived from the classical maximum thermal efficiency for SI engines given by the Otto cycle efficiency (ηOtto). Fuels with MN > 97 got higher EEmax, and ηq than propane, and diesel fuels.

The Effect of Hydrogen Enrichment on The Exhaust Emission Characteristic in A Spark Ignition Engine Fueled by Gasoline-Bioethanol Blends

Bioethanol characteristics can be used as an alternative fuel to spark-ignition (SI) engines to reduce emissions. This experiment evaluates the production of emissions for SI engines using hydrogen enrichment in the gasoline-bioethanol fuel blends. The fraction of bioethanol fuel blend was added to the gasoline fuel of 10% by volume and hydrogen fuel produced by the electrolysis process with a dry cell electrolyzer. The NaOH was used as an electrolyte which is dissolved in water of 5% by a mass fraction. The test is conducted using a single-cylinder 155cc gasoline engine with sensors and an interface connected to a computer to control loading and record all sensor variables in real-time. Hydrogen produced from the electrolysis reactor is injected through the intake manifold using two injectors, hydrogen injected simultaneously at a specific time with a gasoline-bioethanol fuel. The test was conducted with variations of engine speeds. The emission product of ethanol--H2 (BE10+H2) was an excellent candidate as a new alternative of fuel solution in the future. The engasolinerichment of hydrogen increased the flame speed and generated a stable combustion reaction. The hydrogen enrichment produced CO2 emission due to the unavailability of carbon content in hydrogen fuel. As a result, the C/H ratio is lower than for mixed fuels.

A review on the effects of ethanol/gasoline fuel blends on NOX emissions in spark-ignition engines

Ethanol can be used as an alternative fuel for spark-ignition (SI) engines to increase the octane number and oxygen content of ethanol/gasoline blends, thereby reducing dependence on fossil fuels and the exhaust emissions of incomplete combustion products. Although it is widely agreed that ethanol can reduce CO and HC exhaust emissions, the literature on ethanol and NOX emissions is far from conclusive; hence there is a need for an in-depth, updated review of ethanol/gasoline blends in SI engines and the relative production of NOX emissions. In light of that, the present work aims to provide a comprehensive literature review on the current state of ethanol combustion in SI engines to shed definitive light on the potential changes in NOX emissions under various operating conditions. The first part of this paper discusses the feasibility of ethanol as an alternative transportation fuel, including world production and ethanol production processes. The physicochemical properties of ethanol and gasoline are then compared to analyze their effects on combustion efficiency and exhaust emissions. Then, the pathways of NOX formation inside the cylinder of SI engines are discussed in depth. Finally, we review and critically discuss the effects of ethanol concentration in blends and different engine parameters on NOX formation.

Identification and Quantification of Hydrocarbon Functional Groups in Gasoline Using 1H-NMR Spectroscopy for Property Prediction

Gasoline is one of the most important distillate fuels obtained from crude refining; it is mainly used as an automotive fuel to propel spark-ignited (SI) engines. It is a complex hydrocarbon fuel that is known to possess several hundred individual molecules of varying sizes and chemical classes. These large numbers of individual molecules can be assembled into a finite set of molecular moieties or functional groups that can independently represent the chemical composition. Identification and quantification of groups enables the prediction of many fuel properties that otherwise may be difficult and expensive to measure experimentally. In the present work, high resolution 1H nuclear magnetic resonance (NMR) spectroscopy, an advanced structure elucidation technique, was employed for the molecular characterization of a gasoline sample in order to analyze the functional groups. The chemical composition of the gasoline sample was then expressed using six hydrocarbon functional groups, as follows: paraffinic groups (CH, CH2 and CH3), naphthenic CH-CH2 groups and aromatic C-CH groups. The obtained functional groups were then used to predict a number of fuel properties, including research octane number (RON), motor octane number (MON), derived cetane number (DCN), threshold sooting index (TSI) and yield sooting index (YSI).