Mixture Formation in a CNG-DI Engine in Stratified Operation

Friedrich, Wolfgang; Grzeszik, R.; Wensing, Michael

doi:10.4271/2015-24-2474

Cited by 12 publications

(2 citation statements)

References 11 publications

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“…In addition to this, excess air results in a higher isentropic exponent of the mixture and has a positive impact on the thermodynamic efficiency of the process [1]. It was shown that a stratified lean DI operation mode of a spark-ignited CNG engine consumes significantly less fuel than a stoichiometric homogeneous port fuel injection (PFI) operation mode [2].…”

Section: Introductionmentioning

confidence: 99%

A novel cfd approach for modelling the high-pressure direct injection and mixture formation in a spark-ignited cng engine

Twellmeyer¹,

Köpple²

2016

Int. J. CMEM

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The use of compressed natural gas (CNG) as a fuel in internal combustion engines brings significant advantages in terms of reduction of CO 2 -emissions and fuel consumption. Compared to standard gasoline combustion, the CO 2 -production can be clearly reduced by using a methane-based fuel as it has a beneficial H/C ratio. The high knock resistance of methane allows higher compression ratios so that the thermodynamic efficiency is enhanced. Furthermore, the realization of a stratified mixture formation concept shows great potential to further increase fuel savings due to the reduced throttling losses.In the present work, an URANS-based simulation strategy using the commercial code AVL Fire for the direct injection (DI) of CNG and the mixture formation, including a discretisation of the full nozzle and cylinder geometry is presented. High pressure ratios between the injector and the cylinder lead to a choked flow inside the nozzle. A supersonic region, including shock-occurrence follows as the jet is expanded further downstream the orifice. To successfully resolve the multi-scale flow phenomena the mesh generation process involves the design of a fine hexahedral mesh for the injector, which is merged to the moving cylinder mesh by an arbitrary interface. Turbulence is modelled using the k-ζ-f model. To estimate the grid-induced error of the simulation, a set of calculations was performed on meshes of decreasing cell dimension. Different nozzle geometries are investigated and evaluated with regard to their mixture formation suitability as well as the effect of increasing rail pressure. Variations include an inward opening multi-hole injector and an outward opening annular ring injector. The results show a strong tendency of the gas jets to interact with each other and with the surrounding walls.

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Section: Introductionmentioning

confidence: 99%

A novel cfd approach for modelling the high-pressure direct injection and mixture formation in a spark-ignited cng engine

Twellmeyer¹,

Köpple²

2016

Int. J. CMEM

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“…However, natural gas DI also offers the possibility to stratify the charge. The effects of NG stratification in monofuel PC engines have been studied experimentally by Friedrich et al [5] and Melaika and Dahlander [14]. Baratta et al [1] investigated the phenomena numerically by means of CFD simulations.…”

Section: State Of the Artmentioning

confidence: 99%

A holistic investigation of natural gas–diesel dual fuel combustion with dual direct injection for passenger car applications

Fasching

Sprenger

Granitz

2017

Automot. Engine Technol.

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This publication covers the investigation of a dual fuel combustion process for passenger car applications using natural gas and diesel as fuels. In the literature a widely studied dual fuel concept is the combination of port fuel injection of natural gas and direct injection of diesel. The challenge of this concept is a high emission of unburned hydrocarbons at low load operation as previous publications show. The proposed concept features a low pressure direct injection of natural gas in combination with direct injection of diesel to circumvent this problem. The acronym DDI-dual direct injection is introduced for this concept. It enables charge stratification of the air-natural gas mixture. This allows for a significant reduction of the unburned hydrocarbon emissions as earlier studies already demonstrated. The focus of this publication is on hardware variations which were performed on the engine test bench. Results are presented of a variation of the compression ratio and of different charge motion patterns which were studied. The results are compared with a conventional diesel and a gasoline spark ignited engine. The investigations demonstrate that a CO 2 reduction of 20-29% is feasible as compared to conventional engines. Finally, investigations of exhaust gas aftertreatment with a threeway catalyst are published. The aftertreatment of the remaining engine-out hydrocarbon emissions is still the key challenge due to the low exhaust gas temperature during low load operation.

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Quantitative 1-D LIBS measurements of fuel concentration in natural gas jets at high ambient pressure

Zhang

Wang

et al. 2021

Experimental Thermal and Fluid Science

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Mixture Formation in a CNG-DI Engine in Stratified Operation

Cited by 12 publications

References 11 publications

A novel cfd approach for modelling the high-pressure direct injection and mixture formation in a spark-ignited cng engine

A novel cfd approach for modelling the high-pressure direct injection and mixture formation in a spark-ignited cng engine

A holistic investigation of natural gas–diesel dual fuel combustion with dual direct injection for passenger car applications

Quantitative 1-D LIBS measurements of fuel concentration in natural gas jets at high ambient pressure

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