Compressed air injection in spark-ignition engines represents a promising approach to improve combustion while reducing pollutant emissions. This thesis builds on the work of Niquet et al. (2025), adapting a concept initially developed for direct injection of recirculated exhaust gases (EGR) to compressed air. The main objective is to numerically evaluate the impact of different injection strategies on engine performance.
A three-dimensional CFD model of the cylinder was developed using the k–ζ–f turbulence model and the ECFM-3Z combustion model. A mesh sensitivity study ensured the reliability of the results, while experimental validation of pressure and heat release curves confirmed the model’s accuracy.
The simulations were then used to explore the effects of air injection at various crank angles, with constant spark timing. When performed before top dead center (TDC), the injection increases peak pressure, indicated mean effective pressure (IMEP), and turbulence, depending on the injected air’s mass and temperature. Certain strategies, particularly at 175° and 130° before TDC, proved effective in accelerating combustion. After TDC, air injection favorably alters the conditions of the following cycle by reducing residual gases and increasing the local cylinder temperature. Finally, an exploratory strategy at 20° after TDC demonstrated that a late injection can significantly increase pressure during the expansion stroke, resulting in an improvement in the IMEP-to-fuel mass ratio of up to 15 %, without compromising the combustion.
| Date | 20 Aug 2025 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Patrice Seers (Supervisor) |
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Bigaouette, F. (Author),
Seers (Supervisor),
20 Aug 2025Student thesis: Master's thesis › Master in Engineering: Engineering