HD Base Engine Development to Meet Future Emission and Power Density Challenges of a DDI™ Engine

Dreisbach, Rolf; Graf, Gernot; Kreuzig, Gerhard; Theißl, Helmut; Pfahl, Ulrich

doi:10.4271/2007-01-4225

Cited by 5 publications

(4 citation statements)

References 1 publication

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“…These steps are also sometimes referred to as ''soot-in-oil'' rims. 46 One objective of stepped-lip bowls is to split the fuel spray, directing a portion of it upward toward the head and the remainder downward, into the bowl. By re-directing the radial momentum of the upper portion toward the head, the spray penetration into the squish volume is impededresulting in less soot generated near the cylinder walls where it could find its way into the engine oil.…”

Section: ''Stepped-lip'' Bowl Geometriesmentioning

confidence: 99%

A review of design considerations for light-duty diesel combustion systems

Miles

Andersson

2015

International Journal of Engine Research

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Practical aspects of light-duty diesel combustion system design are reviewed, with an emphasis on design considerations reported by manufacturers and engine design consultancies. The factors driving the selection of compression ratio, stroke-to-bore ratio, and various aspects of combustion chamber geometry are examined, along with the trends observed in these parameters in recently released engines. The interactions among geometric characteristics, swirl ratio, and the fuel injection nozzle parameters are also reviewed.

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Section: ''Stepped-lip'' Bowl Geometriesmentioning

confidence: 99%

A review of design considerations for light-duty diesel combustion systems

Miles

Andersson

2015

International Journal of Engine Research

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“…As injection timing is retarded, however, the improved DSL piston achieves lower thermal efficiency than the SL piston. This DSL piston was designed to enhance vorticity at early injection timings, 3 and late-injection timings were not considered during the design process. These results suggest that robustness of the engine efficiency to injection timing is an important design parameter.…”

Section: Resultsmentioning

confidence: 99%

“…More recent diesel piston-bowl designs have evolved to stepped-lip (SL) pistons. 3 The SL piston splits the fuel into a portion that enters the piston bowl and a second portion that interacts with the squish region. Compared to a conventional re-entrant bowl where the fuel is redirected towards the bowl only, the SL piston improves utilization of the available air in the squish region, which further enhances mixing and leads to higher heat release rates and improved thermal efficiencies, with reduced wall heat transfer due to the smaller surface area, and lower emissions.…”

Section: Introductionmentioning

confidence: 99%

Effects of a CFD-improved dimple stepped-lip piston on thermal efficiency and emissions in a medium-duty diesel engine

Cho

Pintor

et al. 2022

International Journal of Engine Research

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Diesel piston-bowl shape is a key design parameter that affects spray-wall interactions and turbulent flow development, and in turn affects the engine’s thermal efficiency and emissions. It is hypothesized that thermal efficiency can be improved by enhancing squish-region vortices as they are hypothesized to promote fuel-air mixing, leading to faster heat-release rates. However, the strength and longevity of these vortices decrease with advanced injection timings for typical stepped-lip (SL) piston geometries. Dimple stepped-lip (DSL) pistons enhance vortex formation at early injection timings. Previous engine experiments with such a bowl show 1.4% thermal efficiency gains over an SL piston. However, soot was increased dramatically [SAE 2022-01-0400]. In a previous study, a new DSL bowl was designed using non-combusting computational fluid dynamic simulations. This improved DSL bowl is predicted to promote stronger, more rotationally energetic vortices than the baseline DSL piston: it employs shallower, narrower, and steeper-curved dimples that are placed further out into the squish region. In the current experimental study, this improved bowl is tested in a medium-duty diesel engine and compared against the SL piston over an injection timing sweep at low-load and part-load operating conditions. No substantial thermal efficiency gains are achieved at the early injection timing with the improved DSL design, but soot emissions are lowered by 45% relative to the production SL piston, likely due to improved air utilization and soot oxidation. However, these benefits are lost at late injection timings, where the DSL piston renders a lower thermal efficiency than that of the SL piston. Energy balance analyses show higher wall heat transfer with the DSL piston than with the SL piston despite a 1.3% reduction in the piston surface area. Vortex enhancement may not necessarily lead to improved efficiency as more energetic squish-region vortices can lead to higher convective heat transfer losses.

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“…Initially, one objective of the step-bowl was to split the the fuel spray in two parts, with one direction toward the cylinder head, and the other part into the bowl. This helped the spray to avoid reaching the squish zone, resulting in less soot generated close to the cylinder walls, decreasing the soot-in-oil production in the engine [46,47]. The new bath-tube geometry is a result of the optimization process that reduces the soot emissions, and at the same time improves the efficiency, because this new geometry is focused on the area reduction, which reduces the heat transfer losses and improves the engine efficiency [48].…”

Section: Optimization Process Resultsmentioning

confidence: 99%

Development of an Oxy-Fuel Combustion System in a Compression-Ignition Engine for Ultra-Low Emissions Powerplants Using CFD and Evolutionary Algorithms

Serrano¹,

Bracho²,

Gómez-Soriano³

et al. 2022

Applied Sciences

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This study uses an optimization approach for developing a combustion system in a compression–ignition engine that is able to operate under oxy-fuel conditions, and produces mainly CO2 and H2O as exhaust gases. This is achieved because the combustion concept uses pure oxygen as an oxidizer, instead of air, avoiding the presence of nitrogen. The O2 for the combustion system can be obtained by using a mixed ionic–electronic conducting membrane (MIEC), which separates the oxygen from the air onboard. The optimization method employed maximizes the energy conversion of the system, reducing pollutant emissions (CxHy, particulate matter, and carbon monoxides) to levels near zero. The methodology follows a novel approach that couples computational fluid dynamics (CFD) and particle swarm optimization (PSO) algorithms to optimize the complete combustion system in terms of engine performance and pollutant generation. The study involves the evaluation of several inputs that govern the combustion system design in order to fulfill the thermo-mechanical constraints. The parameters analyzed are the piston bowl geometry, fuel injector characteristics, air motion, and engine settings variables. Results evince the relevance of the optimization procedure, achieving very low levels of gaseous pollutants (CxHy and CO) in the optimum configuration. The emissions of CO were reduced by more than 10% while maintaining the maximum in-cylinder pressure within the limit imposed for the engine. However, indicated efficiency levels are compromised if they are compared with an equivalent condition operating under conventional diesel combustion.

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HD Base Engine Development to Meet Future Emission and Power Density Challenges of a DDI™ Engine

Cited by 5 publications

References 1 publication

A review of design considerations for light-duty diesel combustion systems

A review of design considerations for light-duty diesel combustion systems

Effects of a CFD-improved dimple stepped-lip piston on thermal efficiency and emissions in a medium-duty diesel engine

Development of an Oxy-Fuel Combustion System in a Compression-Ignition Engine for Ultra-Low Emissions Powerplants Using CFD and Evolutionary Algorithms

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