Numerical Analysis of the Combustion and Emission Characteristics of Diesel Engines with Multiple Injection Strategies Using a Modified 2-D Flamelet Model

Kim, Gyujin; Moon, Sun-Young; Lee, Seung-Ha; Min, Kyoungdoug

doi:10.3390/en10091292

Cited by 13 publications

(7 citation statements)

References 44 publications

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“…Previous studies indicate that the overall noise level of the diesel engine is strongly related to the high-frequency pressure oscillation, which can be reduced by variable working parameters, in high load conditions [11][12][13]. However, the quantitative characteristics of the cylinder pressure oscillations still have not been revealed systematically.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

Zheng

Zhou

et al. 2020

Energies

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It is difficult to decompose the in-cylinder pressure of combustion of the direct injection (DI) diesel engine, a transient process associated with complicated oscillation components, because of its steep property. An adaptive cyclic average method based on time varying filter based empirical mode decomposition (TVF-EMD) is proposed to decompose the in-cylinder pressure signal, and the cyclic number is determined adaptively with protruding ratio of high-frequency oscillation. The proposed method is used to compare with the ensemble empirical mode decomposition and original TVF-EMD. The results indicate that the proposed method can overcome the drawbacks of these methods and extract high-frequency oscillations accurately and effectively. Three evaluation indexes, center frequency, normalized energy, and average center frequency are defined to analyze the frequency and energy characteristics of high-frequency oscillation quantitatively. The influence of speed, load, rail pressure, main injection timing, pilot injection interval, and pilot injection quantity are investigated systematically. The energy of high-frequency oscillation reaches the peak at medium-high speed, and increase with engine load and rail pressure. However, the relationship of high-frequency oscillation with fuel injection parameters are non-monotonic.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

Zheng

Zhou

et al. 2020

Energies

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“…To cope with the emission problem and improve the performance of diesel engines, the common rail technology has flourished around the world. The advanced fuel injection technologies in a common rail system, such as the ultrahigh injection pressure [1][2][3][4] and the multiple-injection strategy [5][6][7] as well as the high control accuracy [8], have greatly improved the performance of diesel engines. Under the action of ultrahigh injection pressures, the fuel can be injected into the cylinder in a short time, while the multiple-injection strategy divides the whole injection duration into many parts, creating shorter injection durations.…”

Section: Introductionmentioning

confidence: 99%

Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model

2019

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Common rail systems have been widely used in diesel engines due to the stricter emission regulations. The advances in injector technology and ultrahigh injection pressure greatly promote the development of multiple-injection strategy, leading to the shorter injection duration and more variable injection rate shape, which makes the mixing process more significant for the formation of pollutant emission. In order to study the mixing process of diesel sprays under variable injection rate shapes and find the optimized injection strategy, a one-dimensional spray model was modified in this paper. The model was validated by the measured spray penetrations based on shadowgraphy experiments with the varying injection rate. The simulations were performed with five injection rate shapes, triangle, ramping-up, ramping-down, rectangle and trapezoid. Their spray penetrations, entrainment rates and equivalence ratios along spray axial distance are compared. The potentials of multiple-injection and gas-jet after end-of-injection (EOI) to improve mixing process and emission reduction are discussed finally. The results indicated that ramping-up injection rate obtains the highest entrainment rate after EOI, and it needs 1.5 times of injection duration for the entrainment wave to arrive at the spray tip. For the other four injection rates, the sprays can be treated as a steady-like state, needing twice of injection duration from EOI to the time the entrainment wave reaches the spray tip. The multiple-injection with proper injection rate shape enhanced the entrainment rate, and the gas-jet after EOI affected the mixture distribution and entrainment rate in spray tail under ramping-down injection rate.

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“…In-cylinder temperature and fuel/oxygen ratio (strongly dependent on fuel character [1]), fuel injection, and air entrainment [2,3] during the total injection-mixing-burning sequence in a diesel engine, are important in determining NO x and soot emission levels. Therefore, in recent years, high exhaust gas recirculation (EGR) and flexible two-stage fuel injection [4][5][6][7][8][9] are becoming increasingly popular due to their capability to control combustion temperature and fuel/oxygen ratio. Homogeneous charge compression ignition (HCCI) combustion [10,11], low temperature combustion [12] and high dilution combustion [13,14] are successful new combustion concepts for reducing engine-out toxic emissions by reducing oxygen and combustion temperature using high EGR, however, at the expense of high fuel consumption [15] and a narrow operation range in HCCI combustion [16].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Effects of Assigned EGR Stratification on a Heavy Duty Diesel Engine with Two-Stage Fuel Injection

Shen

Cui

et al. 2018

Energies

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External exhaust gas recirculation (EGR) stratification in diesel engines contributes to reduction of toxic emissions. Weak EGR stratification lies in that strong turbulence and mixing between EGR and intake air by current introduction strategies of EGR. For understanding of ideal EGR stratification combustion, EGR was assigned radically at −30 • CA after top dead center (ATDC) to organize strong EGR stratification using computational fluid dynamics (CFD). The effects of assigned EGR stratification on diesel performance and emissions are discussed in this paper. Although nitric oxides (NO x) and soot emissions are both reduced by means of EGR stratification compared to uniform EGR, the trade-off between NO x and soot still exists under the condition of arranged EGR stratification with different fuel injection strategies. A deterioration of soot emissions was observed when the interval between main and post fuel injection increased, while NO emissions increased first then reduced. The case with a 4 • CA interval between main and post fuel injection is suitable for acceptable NO and soot emissions. Starting the main fuel injection too early and too late is not acceptable, which results in high NO emissions and high soot emissions respectively. The start of the main fuel injection −10 • CA ATDC is suitable.

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Numerical Analysis of the Combustion and Emission Characteristics of Diesel Engines with Multiple Injection Strategies Using a Modified 2-D Flamelet Model

Cited by 13 publications

References 44 publications

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model

Numerical Investigation on Effects of Assigned EGR Stratification on a Heavy Duty Diesel Engine with Two-Stage Fuel Injection

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