Lean Fuel/Air Mixtures for High-Compression Spark-Ignited Engines

Bolt, Jay A.; Holkeboer, David H.

doi:10.4271/620524

Cited by 25 publications

(4 citation statements)

References 5 publications

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“…The third mixture quality improvement, increased mixture temperature, is known to extend misfire lean limits from the work of Bolt and Holkeboer. 4 Finally, it seems logical that improved individual cycle mixture homogeneity in the region of the spark plug gap would extend the misfire lean limits. Table I is an estimate of the contribution of three of the four possible mixture quality improvements to the misfire lean limit extension with vaporization tank carburetion.…”

Section: Misfire Lean Limitsmentioning

confidence: 99%

The Influence of Improved Mixture Quality on Engine Exhaust Em issions ana Performance

Ja¹,

Wm²

1967

Journal of the Air Pollution Control Association

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The Influence of Improved Mixture Quality on Engine Exhaust Emissions and PerformanceA large, steam-heated, fuel vaporization tank was utilized as a carburetor in multicylinder engine testing at steady-state operating conditions. In comparison to normal carburetion, the tank provided improved airfuel mixture quality, i.e., completely vaporized fuel, thoroughly mixed with air, and at elevated temperatures.Although not a practical piece of engine hardware, the tank provided a means of determining the extent of gains to be made with improved mixture quality. Improved mixture quality produced slight reductions in rich mixture hydrocarbon and carbon monoxide concentrations but did not reduce the minimum emissions of these two exhaust contaminants. Minimum fuel consumption was similarly unaffected by improved mixture quality. The most important benefit of improved mixture quality was derived from improved geometric and cyclic fuel distribution-a substantial extension of the misfire lean limit. The significance of lean limit operation and its relationship to reduced exhaust contaminants is discussed in detail.

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Section: Misfire Lean Limitsmentioning

confidence: 99%

The Influence of Improved Mixture Quality on Engine Exhaust Em issions ana Performance

Ja¹,

Wm²

1967

Journal of the Air Pollution Control Association

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“…Equivalence ratio is defined as the ratio of the actual fuel to the stoichiometric ratio. As a result, the free piston engine operating on hydrogen is expected to achieve operating compression ratios in the range of 20-30:1 a completely unrealistic expectation for conventionally fueled SI engine [8,14,15].…”

Section: Introductionmentioning

confidence: 99%

Durability Assessment Of A New Free Piston Spark Ignition Linear Engine: A Computational Approach

Rahman¹,

Ariffin²,

Jamaludin³

et al. 2012

Jurnal Teknologi

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Pendekatan pengkomputeran moden yang berasaskan analisis unsur terhingga untuk penilaian ketahanan dalam komponen enjin linear palam pencucuh piston bebas dua lejang dibentangkan. Maklumat pembebanan adalah sukar ditentukan tanpa sebarang prototaip. Sejarah pembebanan boleh ditentukan menggunakan dinamik multi–jasad. Dengan menggabungkan dinamik multi–jasad, analisis unsur terhingga dan analisis hayat lesu, hayat lesu bagi enjin linear boleh diramal awal semasa reka bentuk. Kertas kerja ini membentangkan ramalan hayat lesu bagi komponen enjin linear piston bebas dengan pembebanan amplitud berubah. Permodelan dan analisis unsur terhingga dijalankan menggunakan reka bentuk terbantu komputer dan perisian analisis unsur terhingga serta ramalan hayat lesu adalah menggunakan kod lesu komersial. Pendekatan permulaan retak digunakan bagi meramal hayat lesu komponen bagi enjin linear piston bebas. Keputusan yang diharapkan adalah plot kontur hayat lesu dan histogram kerosakan pada kes yang paling rosak. Keputusan yang diperolehi menunjukkan bila menggunakan rangkaian beban tegangan yang lebih banyak (beban SAETRN), SWT dan Morrow memberikan hayat lebih singkat daripada model Coffin Manson Walau bagaimanapun, kaedah Coffin–Manson memberikan ramalan yang konservertif bila sejarah masa beban mampatan lebih banyak dan tegasan min sifar. Keputusan juga menunjukkan julat tegasan yang besar juga menyumbang lebih besar kerosakan. Kata kunci: ketahanan, hayat lesu, unsur terhingga, dinamik multi–jasad, enjin linear piston bebas. A modern computational approach based on finite element analysis for integrated durability assessment in a two–stroke free piston spark ignition linear engine components is presented. The loading information is difficult to determine without a prototype. The loading histories can be determined using multi–body dynamics. By combining the multi–body dynamics, finite element analysis and fatigue life analysis, the fatigue life of the linear engine components can be predicted early in the design cycle. This paper presents the prediction of fatigue life for free piston linear engine components with complex variable amplitude loadings. The finite element modeling and analysis has been performed using a computer–aided design and finite element analysis software packages, and the fatigue life prediction was carried out using commercial fatigue codes. Crack initiation approach is applied to predict the fatigue life of the component of a free piston linear engine. The results are expected to show contour plots of fatigue life, and damage histogram at the worst or most damaging case. The obtained results indicate that when using the loading sequences is predominantly tensile in nature (SAETRN loading), the SWT and the Morrow models give shorter life than that results obtained using the Coffin–Manson model. However, the Coffin–Manson method gives conservative prediction when the time histories are predominantly compressive, and zero mean stress loadings. It was also observed that the damage to be generated from the cycles is in the higher stress range. Key words: Durability, fatigue life, finite element, multi–body dynamics, free piston linear engine.

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“…However, NG is more resistant to auto-ignition than most liquid hydrocarbons (i.e., NG has a higher octane number) [16], which allows the use of a higher CR to increase efficiency in SI engine applications. In addition, a higher CR reduce in-cylinder residual gas fraction, which increases the flame speeds and burned-gas expansion rates, hence a better use of the expansion stroke and lower exhaust temperatures [17]. But the higher octane number also increases the difficulty in initiating and controlling the combustion process in compression ignition (CI) engine applications without the use of an additional ignition source [1].…”

Section: Natural Gas Engine Considerationsmentioning

confidence: 99%

“…17 indicate that a higher ϕ advanced and increased peak in-cylinder pressure. A higher amount of fuel accelerated the flame development and propagation under lean conditions, resulting in higher power output (i.e., IMEP) from the engine, as seen inFigure 5.17c.…”

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confidence: 94%

Investigation of Combustion Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition Operation

Liu¹

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The conversion of existing diesel engines to natural-gas spark ignition operation by adding a gas injector in the intake manifold for fuel delivery and replacing the diesel fuel injector with a spark plug to initiate and control the combustion process can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. As the conventional diesel combustion chamber (i.e., flat head and bowl-in-piston) creates high turbulence, the engine can operate leaner, which would increase its efficiency and reduce emissions. However, natural gas combustion in such retrofitted engines presents differences compared to that in conventional spark ignited engines. Subsequently, the main goal of this study was to investigate the characteristics of natural gas combustion inside a diesel-like, fast-burn combustion chamber using a unique array of experimental and numerical tools. The experimental platform consisted of a heavy-duty single-cylinder diesel engine converted to natural-gas spark ignition and operated at a low-speed, lean equivalence ratio, and medium-load condition. The engine can also operate in an optical configuration (i.e., the stock piston and cylinder block can be replaced with a see-through piston and an extended cylinder block), which was used to visualize flame behavior. The optical data indicated a thick and fast-propagated flame in the piston bowl but slower flame propagation inside the squish region. In addition, a 3D numerical model of the optical engine was built to better explain the geometry effects. The simulation results suggested that while the region around the spark plug location experienced a moderate turbulence that helped with the ignition process, the interaction of squish, piston motion, and intake swirl created a highly-turbulent environment that favored the fast burn inside the bowl and stabilized the combustion process. However, the squish region experienced a much lower turbulence, which, combined with the reduced temperature and pressure during the expansion stroke and its higher surface-to-volume ratio, reduced the burning velocity and the flame propagation, but also avoided knocking. Consequently, the bowl-in-piston geometry separated the leanburn natural gas combustion into two distinct events. To extend the optical findings, the metal engine configuration was used to investigate the effects of gas composition, spark timing, equivalence ratio, and engine speed on the two-stage combustion. The results suggested that operating conditions controlled the magnitude and phasing of the two combustion events. Moreover, 3D CFD simulations of the metal engine configuration showed that the squish region contained an important mixture fraction that would burn much slower and can increase the phasing separation between the two combustion events to a point that a second peak would appear in the heat release rate. Moreover, the rapidburn event in such an engine was much shorter compared to its traditional definition (i.e., the time in crank angle degrees between the 10% and 90% energy-releas...

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Lean Fuel/Air Mixtures for High-Compression Spark-Ignited Engines

Cited by 25 publications

References 5 publications

The Influence of Improved Mixture Quality on Engine Exhaust Em issions ana Performance

The Influence of Improved Mixture Quality on Engine Exhaust Em issions ana Performance

Durability Assessment Of A New Free Piston Spark Ignition Linear Engine: A Computational Approach

Investigation of Combustion Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition Operation

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