This study presents the development and optimization of an air intake manifold for a 3-liter, 4-cylinder, 4-valve turbocharged engine operating on Compressed Natural Gas (CNG). The intake manifold plays a critical role in determining engine performance, directly influencing parameters such as power output, brake-specific fuel consumption (BSFC), and emissions. A systematic design methodology was adopted, starting with standard design repository, which were refined through iterative improvements focused on manifold volume, runner geometry, injector location, and fuel injection pressure.
Computational Fluid Dynamics (CFD) simulations were conducted to evaluate the influence of manifold geometry and injector positioning on air-fuel mixing. The analysis assessed three potential injector locations: the tangential port, the swirl port, and a common upstream point where air splits into individual intake runners. Among these, the common upstream point consistently demonstrated superior air-fuel mixing and uniform charge distribution. Experimental validation on an engine test cell confirmed the findings, with significant improvements observed in volumetric efficiency, power output, BSFC, Lambda stability, knocking resistance, and exhaust temperature optimization.
Additionally, higher injection pressures were found to reduce injection duration, thereby mitigating the risk of charge backflow into adjacent cylinders. The study highlights how a well-optimized intake manifold can not only enhance air-fuel mixing but also reduce emissions, improve engine performance, and ensure compliance with BS6 emission standards. In this work, a comprehensive design approach is demonstrated for designing a air intake manifold along with positioning of gas injectors for optimal engine performance.