Modelling of Cyclic Variability in Combustion of Spark-Ignition Engine Using the Cycle- Simulation Model

Sjerić, Momir and Kozarac, Darko and Taritaš, Ivan (2015) Modelling of Cyclic Variability in Combustion of Spark-Ignition Engine Using the Cycle- Simulation Model. = Modelling of Cyclic Variability in Combustion of Spark-Ignition Engine Using the Cycle- Simulation Model. In: AVL Advanced Simulation Technologies International User Conference 2015, 23.-25.06.2015., Graz, Austrija.

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The cycle-to-cycle variations (CCV) in combustion of SI (spark-ignition) engine are initiated by the stochastic nature of in- cylinder flow field and by the imperfect mixing of fuel, air and residual gases that oscillates from cycle-to-cycle. The presence of CCV in combustion causes that the individual combustion progress deviate from the cycle- averaged result increasing the fuel consumption and occurrence of knocking cycles. Variations of these factors are shown in the initial kernel growth rate, in the shifting of the flame center from the spark plug location and in the turbulent burning rate. For the correct prediction of CCV in combustion all mentioned effects should be taken into account. For the modelling of in-cylinder turbulence the developed k-ԑ turbulence sub-model is applied while the spark-ignition associated phenomena are described by using the newly developed quasi-dimensional ignition sub-model (QDIM) that is integrated into the modified quasi- dimensional combustion sub-model of AVL BOOST. The modified quasi-dimensional combustion sub- model is based on the fractal theory and it includes the ignition sub-model, modified transition from laminar to fully developed turbulent flame and two-zone turbulence. The newly developed sub-models for turbulence and combustion were calibrated with the available 3-D CFD results for several SI engines. After that, the cycle-simulation was applied to simulate the cyclic variability in combustion by comparing the cycle-simulation results with the experimental data. The CCV in combustion were triggered with the random and independent variations of in-cylinder turbulence level and the flow angle at the spark plug from cycle-to- cycle. The CCV study was performed on the single cylinder and naturally aspirated SI engine fuelled by gasoline. For each operating point at full load conditions 300 cycles were analyzed and simulated with the application of single set of constants. The simulation results are in a very good agreement with the experimental data for several operating points. The presented cycle-simulation model that includes developed sub-models for the turbulence, ignition and combustion represents the fast and well promising tool to simulate the real performance of SI engine.

Item Type: Conference or Workshop Item (Lecture)
Keywords (Croatian): spark-ignition; combustion; turbulence; cyclic variability
Subjects: TECHNICAL SCIENCE > Mechanical Engineering
Divisions: 400 Department of IC Engines and Mechanical Handling Equipment > 410 Chair of IC Engines and Motor Vehicles
Indexed in Web of Science: No
Indexed in Current Contents: No
Date Deposited: 16 Feb 2017 14:18
Last Modified: 03 Mar 2017 15:37

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