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83-20135696�Numerical Simulation for Ignitability of Spark Plug Using In-Cylinder Combustion Model (Second Report)

� � � Hirotoshi Yoshizaki 1) Takafumi Shichida 2) Shunsuke Tsuga 3) Noriyasu Sugimoto 4) Katsutoshi Nakayama 5)

� � 1) -5) NGK SPARK PLUG CO., LTD 2808 Iwasaki, Komaki-shi, Aich 485-8510, Japan

Presented at the JSAE Annual Congress on 10, 23 ,2013

KEY WORS: heat engine, spark ignition engine, numerical calculation Ignitability (A1)

To improve efficiency highly on gasoline engine, there are methods such as high tumble flow, high compression ratio, high EGR orimprovement of ignition system. However under such conditions, the specification of high-ignitability spark plug may differ from the conventional specification. Estimation of spark plug ignitability at the design phase was difficult, and evaluation was mainly made on engine test; thus numerical simulation method of estimating spark plug ignitability in the cylinder by using detailed chemical kinetics was developed in the last paper.

In this paper, the ignitability of four types of spark plug with different shapes of ground electrode, DFE (Double Fine Electrode), PSPE (Projected Square Platinum Electrode), SPE (Square Platinum Electrode) and Ir (Iridium) shown in fig.1, is calculated and improving the evaluation method of ignitability was considered.

Calculation was coupled with CFD-code STAR-CD, complex chemistry code DARS-CFD and engine simulation code es-ice of CD-adapco. One cylinder of gasoline engine for automotive of inline-4-cylinder, 1500cc, 4-valve per one cylinder was targeted. Calculation was made from opening of inlet valve up to TDC under 1600rpm and light-load condition. Reduced mechanism of Ethane (C2H6, 24 species, 106 reactions) which is gasoline surrogate mechanism considered in the last paper was applied for detailed chemical kinetics. Spark displacement model with virtual particle and spring which were developed by the last paper was applied for the ignition model.

Evaluation method of setting criteria in the cylinder temperature at TDC and set the excess air ratio as a lean limit at the temperature of criteria, correspondence was seen with the experiment at the criteria set at 900K (fig.2 and 3). Therefore heat loss to the spark plug significantly influences ignitability, because area of electrode contacted to the flame at early stage is small and heat loss to the spark plug is small with superior ignitable spark plugs.

Input energy to the spark plug, in-cylinder flow and spark displacement that makes an impact on ignitability other than the electrode shape of the spark plug were also examined. Generally, spark displacement becomes larger by high in-cylinder flow; therefore in-cylinder combustion simulation with spark displacement forcibly controlled was conducted, in order to divide combustion acceleration effect by flow and spark displacement. In consequence, in-cylinder flow was found out to have the largest impact. In this result, correlation was seen between the time average of spark displacement and lean limit when input energy shape is the same.

As mentioned above, numerical simulation can not only simulate actual phenomenon, but can create impossible conditions on actual test and be greatly useful to understand phenomenon that is difficult to make clear on experiments.

20135696

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Fig.2 Comparison of Cylinder Temperature at TDC of Ground Electrode Shapes

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SPE Ir

PSPE DFE

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SPE Ir

PSPE DFE

� Fig.1 Shape of Spark Plug Ground Electrode and Flame (Iso-Surface 1000K) at 1degCA after Ignition Timing

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Fig.3 Comparison of Lean Limit between Calculation at Criteria=900K and Experiment

2013 JSAE Annual Congress(Autumn) - Summarized PaperCopyright © 2013 JSAE

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