Limits of compression ratio in spark-ignition combustion with methanol

Both the shift from fossil to alternative fuels and the implementation of a pre-chamber combustion system allow for an increase in the efficiency of an internal combustion engine through optimizing its combustion process, while simultaneously reducing the engine-out emissions. The combination of alcohol-based fuels and pre-chamber combustion concepts has not been investigated on spark-ignition engines with high compression ratios in a passenger car size. This study presents investigations to show the potential in maximum achievable lean limit and net indicated efficiency. In particular, we present investigations of two alternative alcohol fuels on a direct-injection spark-ignition single-cylinder research engine for passenger car applications with a compression ratio of 16.4. The engine was operated with both an active and a passive pre-chamber, and the experimental results were compared to those of conventional spark-ignition operation. Direct injection was used for both the main combustion chamber and the pre-chamber. Methanol and ethanol were used as fuels for the main combustion chamber, whereas exclusively ethanol was used for the pre-chamber fueling. The performance of the alcohol fuels in all combustion configurations was evaluated in both part-load and high-load conditions. In particular, investigations of the combustion behavior over a variation of the excess air ratio at indicated mean effective pressures of 6 and 15 bar were performed. It can be concluded that with the use of methanol as fuel for the main combustion chamber, both higher excess air ratios and higher indicated efficiencies were achieved compared to the use of ethanol as the main combustion chamber fuel. In particular, a maximum net indicated efficiency of 48% at an excess air ratio of 2.0 was achieved with methanol. Moreover, active pre-chamber operation extended the lean limit to an excess air ratio of 2.3 compared to the maximum lean limit of 1.7 in passive pre-chamber operation.

Section: Methodsmentioning

confidence: 99%

Potential of alcohol fuels in active and passive pre-chamber applications in a passenger car spark-ignition engine

Burkardt

Wouters

Pischinger

2021

“…Therefore, for every measurement 200 consecutive engine cycles were measured and statistical measures applied to analyze the combustion. Test bench data, static pressures and temperatures were adjusted and mass flows were measured according to Wouters et al 30 The calculation of the indicated efficiency is performed automatically at the test bench by the automation system of the engine and checked during post-processing of the data. The formula including a uncertainty analysis can be found in Appendix B.…”

Section: Single-cylinder Enginementioning

confidence: 99%

Impact of thermal swing piston top land coatings on gasoline engine performance and raw emissions

Fischer,

Achenbach,

Pischinger

2023

Self Cite

Upcoming legislations aim to significantly reduce carbon dioxide and hydrocarbon emissions compared to current regulations. Accordingly, options have to be evaluated to not only convert the raw emissions in a catalytic converter, but also to reduce the raw emissions from the combustion process in the first place. Therefore, thermal piston top land coatings, which lead to an oscillating piston surface temperature were investigated on a single cylinder research engine using a gasoline RON95E10 fuel. Measurements were conducted at a compression ratio of 12.2 and a long Miller intake event. In this manuscript the results achieved with yttria stabilized zirconia in comparison to an uncoated piston are displayed. Significant effects of the coatings on the indicated efficiency could be observed mainly at low engine speeds and loads due to the high share of fuel energy in the wall heat losses and incomplete combustion. At these operating points, the reduction of wall heat losses can almost be fully transferred into indicated efficiency, leading to an increase in indicated efficiency of 6.3% by the yttria stabilized zirconia coating. At higher engine speeds and loads, the advantage in indicated efficiency vanishes and a decrease of 0.5% can be observed. Near full load operation the indicated efficiency slightly lower. However, the effects of a thermal swing coating on combustion efficiency and wall heat losses strongly depend on the operation conditions.

“…These results are in good agreement with earlier investigations. [5][6][7] Thus, if ultra-lean engine operation is targeted with new combustion concepts, 8 which could be further extended with alternative fuels, 9 then solutions must be found to mitigate the increasing hydrocarbon emissions according to achieve future emission limits. 10 This applies in particular to the higher alkane emissions at lean engine operation conditions.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the near-wall gas composition in SI-engines using fast gas sampling

Fischer

Lehrheuer

Pischinger

2023

Self Cite

Future internal combustion engines using novel fuels and combustion systems have the potential to achieve ultra-high efficiency and lowest pollutant emissions to comply with future regulatory requirements. Realizing indicated efficiencies over 50% with ultra-lean low temperature combustion face new challenges. To meet this goal, hydrocarbon (HC) and carbon monoxide (CO) emissions need to be reduced significantly further. To do this, knowledge must be gained about how the operation regime of the engine affects the HC and CO emissions. Since these emissions partly originate from areas where flame quenching occurs, an investigation of the gases near the wall is of interest. To this end a fast gas sampling method is being developed to extract and analyze the gas from the combustion chamber. The used fast gas sampling valve from Kistler enables sampling durations of less than 1 ms. Fourier-transform-infrared spectroscopy and a fast mass spectroscopy allow the determination of the sample composition. The valve is positioned inside the cylinder head of a single cylinder engine between intake and exhaust valves. In order to assess the effects of engine operating conditions on the formation of HC and CO at the cylinder walls, the measurement uncertainty of the setup must be evaluated. Since the combustion process is subject to cyclic variations, the evaluation of only a few individual measurements is not meaningful. Therefore, mean values are determined from the evaluation of several measurements not performed consecutively. By examining the mean and standard deviation of these measurements for each species, one can determine a measurement error. In comparison, lean operation with RON95E10 fuel at an IMEP = 12 bar and an engine speed of n = 2000 1/min shows a significant reduction in intermediate hydrocarbon species such as acetylene and a significant increase in fuel species such as ethanol compared to stoichiometric operation.