An Analysis of the Combustion Behavior of Ethanol, Butanol,Iso-Octane, Gasoline, and Methane in a Direct-Injection Spark-Ignition Research Engine

Abstract

Future automotive fuels are expected to contain significant quantities of bio-components. This poses a great challenge to the designers of novel low-CO 2 internal combustion engines because biofuels have very different properties to those of most typical hydrocarbons. The current article presents results of firing a direct-injection spark-ignition optical research engine on ethanol and butanol and comparing those to data obtained with gasoline and iso-octane. A multihole injector, located centrally in the combustion chamber, was used with all fuels. Methane was also employed by injecting it into the inlet plenum to provide a benchmark case for well-mixed ''homogeneous'' charge preparation. The study covered stoichiometric and lean mixtures (k ¼ 1.0 and k ¼ 1.2), various spark advances (30-50 CA), a range of engine temperatures (20-90 C), and diverse injection strategies (single and ''split'' triple). In-cylinder gas sampling at the spark-plug location and at a location on the pent-roof wall was also carried out using a fast flame ionization detector to measure the equivalence ratio of the in-cylinder charge and identify the degree of stratification. Combustion imaging was performed through a full-bore optical piston to study the effect of injection strategy on late burning associated with fuel spray wall impingement. Combustion with single injection was fastest for ethanol throughout 20-90 C, but butanol and methane were just as fast at 90 C; iso-octane was the slowest and gasoline was between iso-octane and the alcohols. At 20 C, k at the spark plug location was 0.96-1.09, with gasoline exhibiting the largest and iso-octane the lowest value. Ethanol showed the lowest degree of stratification and butanol the largest. At 90 C, stratification was lower for most fuels, with butanol showing the largest effect. The work output with triple injection was marginally higher for the alcohols and lower for iso-octane and gasoline (than with single injection), but combustion stability was worse for all fuels. Triple injection produced a lower degree of stratification, with leaner k at the spark plug than single injection. Combustion imaging showed much less luminous late burning with tripe injection. In terms of combustion stability, the alcohols were more robust to changes in fueling (k ¼ 1.2) than the liquid hydrocarbons.

Flame front analysis of ethanol, butanol, iso-octane and gasoline in a spark-ignition engine using laser tomography and integral length scale measurements

“…The cylinder charge of this engine has not been investigated regarding locally rich or lean regions at the spark plug at ignition timing. However, AFR variations were likely and would also vary with fuel type as shown by [50] for the same fuels in an optical engine of very similar geometry and capacity to that of the current study (typically 0.05 among fuels).…”

“…capturing one flame image per crank-angle degree at 1500 RPM. Details of the system have been described in previous studies and not repeated here for brevity [13,20,21,[47][48][49][50][51]. The fast shutter speed reduced background noise but also led to low combustion luminosity levels requiring small thresholding values for processing.…”

“…Pressure data were post-processed to calculate the Indicated Mean Effective Pressure (IMEP), amplitude and timing of peak in-cylinder pressure, including mean values and Coefficients of Variation (COV=Mean/RMS). Heat release analysis and calculation of Mass Fraction Burned (MFB) was performed using methods based on [58,59] and followed practices of earlier work by the current authors for consistency [13,20,21,[48][49][50][51]. All uncertainties involved in acquiring and processing in-cylinder pressure data were carefully considered according to [60].…”

Experimental study on combustion duration and performance characteristics of a hydrogen-ethanol dual fueled engine

“…Also, hydrogen addition allowed the engine to run stable in points where methane could not be tested. A study by Pereira et al [6] covered stoichiometric and lean mixtures (λ = 1.0 and λ = 1.2), various spark advances (30-50° CA), a range of engine temperatures (20-90°C), and diverse injection strategies (single and "split" triple). In-cylinder gas sampling at the spark-plug location and at a location on the pent-roof wall was also carried out using a fast flame ionization detector to measure the equivalence ratio of the in-cylinder charge and identify the degree of stratification.…”

Characterisation of Spray Development from Spark-Eroded and Laser-Drilled Multi-Hole Injectors in an Optical DISI Engine and in a Quiescent Injection Chamber

“…8, and geometrical details are summarised in Table 1. Further information on this engine and can be found in previous publications and are not repeated here for brevity [15][16][17][18][19][20]. Inlet: 129° CA after intake TDC Exhaust: 86° CA before intake TDC…”