Combustion-Related Emissions in SI Engines

Hochgreb, Simone

doi:10.1016/b978-012639855-7/50045-4

Cited by 27 publications

(12 citation statements)

References 111 publications

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“…In contrast to CO, the equilibrium levels are very low and the oxidation rates fast [14]. Different literature studies identified and quantified the main sources of HC emissions [7,[15][16][17][18][19] as crevices (piston-ring pack, valves, spark plug, cylinder head gasket, etc. ), flame quenching, oil-film, and fuel film.…”

Section: Hydrocarbon Emission From Si Enginesmentioning

confidence: 99%

Development of Phenomenological Models for Engine-Out Hydrocarbon Emissions from an SI DI Engine within a 0D Two-Zone Combustion Chamber Description

Esposito¹,

Diekhoff²,

Pitsch³

et al. 2021

SAE Technical Paper Series

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The increasingly stringent limits on pollutant emissions from internal combustion engine-powered vehicles require the optimization of advanced combustion systems by means of virtual development and simulation tools. Among the gaseous emissions from spark-ignition engines, the unburned hydrocarbon (HC) emissions are the most challenging species to simulate because of the complexity of the multiple physical and chemical mechanisms that contribute to their emission. These mechanisms are mainly three-dimensional (3D) resulting from multi-phase physics -e.g., fuel injection, oil-film layer, etc. -and are difficult to predict even in complex 3D computational fluid-dynamic (CFD) simulations. Phenomenological models describing the relationships between the physical-chemical phenomena are of great interest for the modeling and simplification of such complex mechanisms. In addition, phenomenological models can be applied within simplified simulation environments, e.g., 0D-1D engine simulations, to enable predictions of HC emissions for a wide range of operating conditions. In this work, the development of phenomenological models to account for HC emissions from piston top-land crevices, wall flame quenching, and oil-film adsorption/desorption mechanisms is explained in detail. The model development is based on measurements and models from a single cylinder direct injection (DI) spark ignition (SI) research engine. Common modeling hypotheses and approaches from literature have been verified and further developed with 3D-CFD simulations. In particular, assumptions regarding local temperature and air-fuel ratio, which are necessary for HC modeling, have been developed on the basis of a zone post-processing of the 3D-CFD results. Additionally, a novel approach to describe HC post-oxidation, which is based on 0Dchemistry calculations, has been developed. The HC models have been implemented within a GT-POWER model of the engine in conjunction with a 0D two-zone combustion chamber description. The accuracy of the developed models has been tested against a large experimental database with varying engine load, speed, air to fuel ratio, valve timing, and oil/coolant temperature. The deviation in the HC emission prediction is mainly within 20% at warm engine operation. Higher deviations are observed at cold engine conditions because of the absence of secondary HC models which have not been considered in the present work.

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Section: Hydrocarbon Emission From Si Enginesmentioning

confidence: 99%

Development of Phenomenological Models for Engine-Out Hydrocarbon Emissions from an SI DI Engine within a 0D Two-Zone Combustion Chamber Description

Esposito¹,

Diekhoff²,

Pitsch³

et al. 2021

SAE Technical Paper Series

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show abstract

“…This is a phenomenon characteristic of diluted combustions, reduced engine load, and high cyclic variability. 13…”

Section: Introductionmentioning

confidence: 99%

“…In light of the above considerations, the main aim of this work is the development of a phenomenological model for the quantification of the unburned hydrocarbons, able to sense the most important engine operating parameters and some geometrical features (ring pack geometry, engine compression ratio, bore). Conversely to other works available in the current literature, 11–23 the model is developed and validated concerning engines fueled with natural gas, instead of gasoline. Moreover, the considered engines are also characterized by different ignition devices, specifically dual fuel mode and pre-chamber.…”

Section: Introductionmentioning

confidence: 99%

A phenomenological model for the description of unburned hydrocarbons emission in ultra-lean engines

Malfi

Bellis

Bozza

et al. 2021

International Journal of Engine Research

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The adoption of lean-burn concepts for internal combustion engines working with a homogenous air/fuel charge is under development as a path to simultaneously improve thermal efficiency, fuel consumption, nitric oxides, and carbon monoxide emissions. This technology may lead to a relevant emission of unburned hydrocarbons (uHC) compared to a stoichiometric engine. The uHC sources are various and the relative importance varies according to fuel characteristics, engine operating point, and some geometrical details of the combustion chamber. This concern becomes even more relevant in the case of engines supplied with natural gas since the methane has a global warming potential much greater than the other major pollutant emissions. In this work, a simulation model describing the main mechanisms for uHC formation is proposed. The model describes uHC production from crevices and flame wall quenching, also considering the post-oxidation. The uHC model is implemented in commercial software (GT-Power) under the form of “user routine”. It is validated with reference to two large bore engines, whose bores are 31 and 46 cm (engines named accordingly W31 and W46). Both engines are fueled with natural gas and operated with lean mixtures (λ > 2), but with different ignition modalities (pre-chamber device or dual fuel mode). The engines under study are preliminarily schematized in the 1D simulation tool. The consistency of 1D engine schematizations is verified against the experimental data of BMEP, air flow rate, and turbocharger rotational speed over a load sweep. Then, the uHC model is validated against the engine-out measurements. The averaged uHC predictions highlight an average error of 7% and 10 % for W31 and W46 engines, respectively. The uHC model reliability is evidenced by the lack of need for a case-dependent adjustment of its tuning constants, also in presence of relevant variations of both engine load and ring pack design.

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“…It is currently held that in urban areas in the United States, cars, trucks and off-road vehicles are responsible for about 40 -50 per cent of HC or VOC emissions, 50 per cent of NO x emissions and 80-90 per cent of the CO emissions [1]. The largest contribution (\ 90 per cent) to HC emission from spark-ignition (SI) engines during a standard test was found to occur during the first minute of operation [2].…”

Section: Introductionmentioning

confidence: 99%

Reducing cold-start emission from internal combustion engines by means of a catalytic converter embedded in a phase-change material

Korin

Reshef

Tshernichovesky

et al. 1999

Proceedings of the Institution of Mechanical Engineers, Part D:

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Under normal operating conditions, catalytic converters appear to be the most effective means of reducing air pollution from internal combustion (IC) engines. The conversion efficiency, however, declines very steeply for temperatures below about 350°C and is practically zero during the starting and warming-up period. Improving the conversion efficiency under these conditions is important, particularly in large cities, where the number of startings per vehicle per day tends to be high. Among the more successful solutions are preheating of the catalyst electrically, warming up of the catalyst in an external combustion chamber, installation of an auxiliary small-capacity catalytic converter, and employment of an adsorbing unit between two catalysts. Although these methods are quite effective, their disadvantage lies in the fact that they require an external energy source, an additional component (a control unit) or a three-stage catalyst. In the present work an investigation was made of a solution based on the exploitation of thermal capacitance to keep the catalyst temperature high during off-operation periods. A phase-change material (PCM) with a transition temperature of 352.7°C, which is slightly above the light-off temperature of the metallic catalyst, was specially formulated, and a system comprising a catalytic converter embedded in the PCM was designed and tested. Under normal engine operating conditions, some of the thermal energy of the exhaust gases was stored in the PCM. During the time that the vehicle was not in use, the PCM underwent partial solidification, and the latent heat thus produced was exploited to maintain the catalyst temperature within the desired temperature range for maximum conversion efficiency.

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Combustion-Related Emissions in SI Engines

Cited by 27 publications

References 111 publications

Development of Phenomenological Models for Engine-Out Hydrocarbon Emissions from an SI DI Engine within a 0D Two-Zone Combustion Chamber Description

Development of Phenomenological Models for Engine-Out Hydrocarbon Emissions from an SI DI Engine within a 0D Two-Zone Combustion Chamber Description

A phenomenological model for the description of unburned hydrocarbons emission in ultra-lean engines

Reducing cold-start emission from internal combustion engines by means of a catalytic converter embedded in a phase-change material

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