Numerical and Experimental Analysis of Ignition and Combustion Stability in EGR Dilute GDI Operation

This paper discusses the characteristics of EGR dilute GDI engines in terms of combustion stability. A combined approach consisting of RANS numerical simulations integrated with experimental engine testing is used to analyze the effect of the ignition source on flame propagation under dilute operating conditions. A programmable spark-based ignition system is compared to a production spark system in terms of cyclic variability and ultimately indicated efficiency. 3D-CFD simulations are carried out for multiple cycles with the goal of establishing correlations between the characteristics of the ignition system and flame propagation as well as cycle-to-cycle variations. Numerical results are compared to engine data in terms of in-cylinder pressure traces. The results show that an improved control over the energy released to the fluid surrounding the spark domain during the ignition process has beneficial effects on combustion stability. This allows extending the dilution tolerance for fuel/air mixtures. Although affected by cyclic variability, numerical results show good qualitative agreement with experimental data. The result is a simple but promising approach for relatively quick assessment of stability improvements from advanced and alternative ignition strategies.

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Parametric Study of Ignition and Combustion Characteristics From a Gasoline Compression Ignition Engine Using Two Different Reactivity Fuels

ASME 2016 Internal Combustion Engine Fall Technical Conference ◽

10.1115/icef2016-9395 ◽

2016 ◽

Cited By ~ 6

Author(s):

Khanh Cung ◽

Toby Rockstroh ◽

Stephen Ciatti ◽

William Cannella ◽

S. Scott Goldsborough

Keyword(s):

High Speed ◽

Injection Pressure ◽

Operating Conditions ◽

Combustion Stability ◽

Injection Timing ◽

Strong Impact ◽

Boost Pressure ◽

Compression Ignition ◽

Compression Ignition Engine ◽

Ignition And Combustion

Unlike homogeneous charge compression ignition (HCCI) that has the complexity in controlling the start of combustion event, partially premixed combustion (PPC) provides the flexibility of defining the ignition timing and combustion phasing with respect to the time of injection. In PPC, the stratification of the charge can be influenced by a variety of methods such as number of injections (single or multiple injections), injection pressure, injection timing (early to near TDC injection), intake boost pressure, or combination of several factors. The current study investigates the effect of these factors when testing two gasoline-like fuels of different reactivity (defined by Research Octane Number or RON) in a 1.9-L inline 4-cylinder diesel engine. From the collection of engine data, a full factorial analysis was created in order to identify the factors that most influence the outcomes such as the location of ignition, combustion phasing, combustion stability, and emissions. Furthermore, the interaction effect of combinations of two factors or more was discussed with the implication of fuel reactivity under current operating conditions. The analysis was done at both low (1000 RPM) and high speed (2000 RPM). It was found that the boost pressure and air/fuel ratio have strong impact on ignition and combustion phasing. Finally, injection-timing sweeps were conducted whereby the ignition (CA10) of the two fuels with significantly different reactivity were matched by controlling the boost pressure while maintaining a constant lambda (air/fuel equivalence ratio).

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Development of Advanced Laser Ignition System for Stationary Natural Gas Reciprocating Engines

ASME 2005 Internal Combustion Engine Division Fall Technical Conference (ICEF2005) ◽

10.1115/icef2005-1325 ◽

2005 ◽

Cited By ~ 21

Author(s):

Bipin Bihari ◽

Sreenath B. Gupta ◽

Raj R. Sekar ◽

Jess Gingrich ◽

Jack Smith

Keyword(s):

Natural Gas ◽

Operating Conditions ◽

Combustion Stability ◽

Laser Ignition ◽

Nox Emissions ◽

Ignition System ◽

Performance Improvements ◽

Discharge Ignition ◽

Reciprocating Engines ◽

Load Conditions

Laser ignition is considered the prime alternative to conventional coil based ignition for improving efficiency and simultaneously reducing NOx emissions in lean-burn natural gas fired stationary reciprocating engines. In this paper, Argonne’s efforts towards the development of a viable laser ignition system are presented. The relative merits of various implementation strategies for laser based ignition are discussed. Finally, the performance improvements required for some of the components for successful field implementation are listed. Also reported are efforts to determine the relative merit of laser ignition over conventional Capacitance Discharge Ignition (CDI) ignition. Emissions and performance data of a large-bore single cylinder research engine are compared while running with laser ignition and the industry standard CDI system. It was primarily noticed that NOx emissions reduce by 50% under full load conditions with up to 65% reductions noticed under part load conditions. Also, the lean ignition limit was significantly extended and laser ignition improved combustion stability under all operating conditions. Other noticeable differences in combustion characteristics are also presented. Efforts wherein ignition was achieved while transmitting the high-power laser pulses through optical fibers showed performance improvements similar those achieved by using free-space laser ignition.

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Capturing Cyclic Variability in EGR Dilute SI Combustion Using Multi-Cycle RANS

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2015-1045 ◽

2015 ◽

Cited By ~ 8

Author(s):

Riccardo Scarcelli ◽

James Sevik ◽

Thomas Wallner ◽

Keith Richards ◽

Eric Pomraning ◽

...

Keyword(s):

Internal Combustion Engines ◽

Initial Conditions ◽

Stability Limit ◽

Operating Conditions ◽

Combustion Stability ◽

Navier Stokes ◽

Cyclic Variability ◽

Numerical Result ◽

Ignition Characteristics ◽

The Stability

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically Large Eddy Simulations (LES) are performed to simulate cyclic engine variations, since Reynold-Averaged Navier-Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multi-cycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder GDI research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as EGR dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multi-cycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data, but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.

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Extending Lean and EGR-Dilute Operating Limits of a Modern GDI Engine Using a Low-Energy Transient Plasma Ignition System

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2015-1048 ◽

2015 ◽

Cited By ~ 2

Author(s):

James Sevik ◽

Thomas Wallner ◽

Michael Pamminger ◽

Riccardo Scarcelli ◽

Dan Singleton ◽

...

Keyword(s):

Direct Injection ◽

Load Condition ◽

Operating Conditions ◽

Low Energy ◽

Gasoline Direct Injection ◽

Combustion Stability ◽

Ignition System ◽

Part Load ◽

Plasma Ignition ◽

Transient Plasma

The efficiency improvement and emissions reduction potential of lean and EGR dilute operation of spark-ignition gasoline engines is well understood and documented. However, dilute operation is generally limited by deteriorating combustion stability with increasing inert gas levels. The combustion stability decreases due to reduced mixture flame speeds resulting in significantly increased combustion initiation periods and burn durations. A study was designed and executed to evaluate the potential to extend lean and EGR-dilute limits using a low-energy transient plasma ignition system. The low-energy transient plasma was generated by nano-second pulses and its performance compared to a conventional transistorized coil ignition system operated on an automotive, gasoline direct injection (GDI) single-cylinder research engine. The experimental assessment was focused on steady-state experiments at the part load condition of 1500 rpm 5.6 bar IMEP, where dilution tolerance is particularly critical to improving efficiency and emissions performance. Experimental results suggest that the energy delivery process of the low-energy transient plasma ignition system significantly improves part load dilution tolerance by reducing the early flame development period. Statistical analysis of relevant combustion metrics was performed in order to further investigate the effects of the advanced ignition system on combustion stability. Results confirm that at select operating conditions EGR tolerance and lean limit could be improved by as much as 20% (from 22.7 to 27.1% EGR) and nearly 10% (from λ=1.55 to 1.7) with the low-energy transient plasma ignition system.

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Capturing Cyclic Variability in Exhaust Gas Recirculation Dilute Spark-Ignition Combustion Using Multicycle RANS

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4033184 ◽

2016 ◽

Vol 138 (11) ◽

Cited By ~ 4

Author(s):

Riccardo Scarcelli ◽

James Sevik ◽

Thomas Wallner ◽

Keith Richards ◽

Eric Pomraning ◽

...

Keyword(s):

Internal Combustion Engines ◽

Initial Conditions ◽

Exhaust Gas Recirculation ◽

Spark Ignition ◽

Operating Conditions ◽

Combustion Stability ◽

Exhaust Gas ◽

Cyclic Variability ◽

Ignition Characteristics ◽

Gas Recirculation

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically large eddy simulations (LES) are performed to simulate cyclic engine variations, since Reynolds-averaged Navier–Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper, it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multicycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder gasoline direct injection (GDI) research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as exhaust gas recirculation (EGR) dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multicycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.

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Effect of Temperature Conditions on Flame Evolutions of Turbulent Jet Ignition

Energies ◽

10.3390/en14082226 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2226

Author(s):

Jiaying Pan ◽

Yu He ◽

Tao Li ◽

Haiqiao Wei ◽

Lei Wang ◽

...

Keyword(s):

Flame Propagation ◽

Early Stage ◽

Turbulent Jet ◽

Combustion Stability ◽

Effect Of Temperature ◽

Main Chamber ◽

Detailed Chemical Kinetics ◽

Jet Flame ◽

Spherical Flame ◽

Temperature Conditions

Turbulent jet ignition technology can significantly improve lean combustion stability and suppress engine knocking. However, the narrow jet channel between the pre-chamber and the main chamber leads to some difficulties in heat exchange, which significantly affects combustion performance and mechanical component lifetime. To clarify the effect of temperature conditions on combustion evolutions of turbulent jet ignition, direct numerical simulations with detailed chemical kinetics were employed under engine-relevant conditions. The flame propagation in the pre-chamber and the early-stage turbulent jet ignition in the main chamber were investigated. The results show that depending on temperature conditions, two types of flame configuration can be identified in the main chamber, i.e., the normal turbulent jet flame propagation and the spherical flame propagation, and the latter is closely associated with pressure wave disturbance. Under low-temperature conditions, the cold jet stoichiometric mixtures and the vortexes induced by the jet flow determine the early-stage flame development in the main chamber. Under intermediate temperature conditions, pre-flame heat release and leading pressure waves are induced in the jet channel, which can be regarded as a transition of different combustion modes. Whereas under high-temperature conditions, irregular auto-ignition events start to occur, and spherical flame fronts are induced in the main chamber, behaving faster flame propagation.

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The behaviour of heavily loaded line contacts with transverse roughness

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/0954406991522275 ◽

1999 ◽

Vol 213 (4) ◽

pp. 309-320 ◽

Cited By ~ 10

Author(s):

C. J. Hooke

Keyword(s):

Surface Roughness ◽

Full Range ◽

Numerical Results ◽

Operating Conditions ◽

Entrainment Velocity ◽

Original Surface ◽

Line Contacts ◽

Transverse Roughness ◽

Inlet Length

In heavily loaded, piezoviscous contacts the surface roughness tends to be flattened inside the conjunction by any relative sliding of the surfaces. However, before it is flattened, the roughness affects the inlet to the contact, producing clearance variations there. These variations are then convected through the contact, at the entrainment velocity, producing a clearance distribution that differs from the original surface. The present paper explores this behaviour and establishes how the amplitude of the convected clearance varies with wavelength and operating conditions. It is shown that the primary influence is the ratio of the wavelength to the inlet length of the conjunction. Where this ratio is large, the roughness is smoothed and there is little variation in clearance under the conjunction. Where the ratio is small, significant variations in clearance may occur but the precise amplitude and phasing depend on the ratio of slide to roll velocities and on the value of a piezoviscous parameter, c. The numerical results agree closely with existing solutions but extend these to cover the full range of operating conditions.

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Diagnostics of automotive ignition system in operating conditions

2020 ELEKTRO ◽

10.1109/elektro49696.2020.9130258 ◽

2020 ◽

Author(s):

Milan Sebok ◽

Matej Kubis ◽

Miroslav Gutten ◽

Matej Kucera ◽

Tomasz N. Koltunowicz ◽

...

Keyword(s):

Operating Conditions ◽

Ignition System

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Improving Blowout Performance of the Conical Swirler Combustor by Employing Two Parts of Fuel at Low Operating Condition

Energies ◽

10.3390/en14061681 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1681

Author(s):

Yixiang Yuan ◽

Qinghua Zeng ◽

Jun Yao ◽

Yongjun Zhang ◽

Mengmeng Zhao ◽

...

Keyword(s):

Distribution Ratio ◽

Performance Enhancement ◽

Experimental Testing ◽

Stability Boundary ◽

Operating Conditions ◽

Nox Emission ◽

Combustion Stability ◽

Gas Temperature ◽

Contact Ratio ◽

Fuel Distribution

Aiming at the problem of the narrow combustion stability boundary, a conical swirler was designed and constructed based on the concept of fuel distribution. The blowout performance was studied at specified low operating conditions by a combination of experimental testing and numerical simulations. Research results indicate that the technique of the fuel distribution can enhance the combustion stability and widen the boundary of flameout within the range of testing conditions. The increase of the fuel distribution ratio improves the combustion stability but leads to an increase in NOx emission simultaneously. The simulation results show the increase of the fuel distribution ratio causes contact ratio increase in the area of lower reference velocity and gas temperature increase. The increased contact ratio and temperature contribute to the blowout performance enhancement, which is identical to the analysis result of the Damkohler number. The reported work in this paper has potential application value for the development of an industrial burner and combustor with high stability and low NOx emission, especially when the combustion system is required to be stable and efficient at low working conditions.

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