engleski

Modeling of Natural Gas Engine With The Emphasis on Prediction of Knock

New engine development trends that include high levels of boosting have put a requirement for models that will be able to predict knock. Therefore a new knock model that uses non-uniform temperature distribution of the unburned zone and is able to run multiple cycles in reasonable time was developed. The model is implemented into cycle simulation software, with the calculation of unburned zone temperature distribution based on the CFD results of the engine. By using a newly developed knock model the calculations of knock in a research gas engine were performed. The research gas engine was modeled in AVL Fire to provide necessary mass-temperature distributions of the unburned zone, while the actual knock is modeled in AVL Boost. The simulations are performed during 250 cycles for each operating condition. Differences between cycles were calculated by setting different Vibe parameters for each cycle. These Vibe parameters are obtained from experimental pressures. That approach enabled the input of influence of cycle by cycle variations in the calculation of knock. Also the possibility to use Vibe combustion with random parameters as a means of simulating cycle by cycle variations and their influence on knock was explored. The calculations showed that predictions of the model were good and that the model was able to distinguish between knock and no knock conditions.

Knock; Combustion; Methane; Simulation

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