Achieving Enhanced Swirl with Vortex Generating Jets in a Light-Duty Direct-Injected Diesel Engine

As the transportation sector faces increasingly stringent environmental regulations, enhancing thermal efficiency and reducing emissions remain critical objectives. The development covers combustion process, lubrication to exhaust gas after treatment as well as engine control strategies. This study focuses on both charge exchange and combustion processes. Swirl plays a crucial role in combustion and engine performance. Conventionally, swirl is induced through intake port geometries such as helical and tangential designs, though these methods compromise airflow, leading to increased pumping losses. In this context, our study builds on earlier work from our institutes, employing Vortex Generating Jets (VGJs) to produce swirl. VGJ are a state-of-the-art technology in the aerospace industry to increase capability of aircraft by influencing airflow. Three representative intake ports were selected from a computational fluid dynamics (CFD) simulated Pareto front - characterizing high, mid, and low swirl scenarios - for empirical evaluation. These simulations follow the geometric constraints of a passenger car 2L diesel engine. The influence of air injection via VGJs into the intake ports was investigated using a steady-state flow test bench, assessing impacts on swirl and flow. A variation in VGJ placement and injected airflow rates revealed that strategic air injection significantly enhances both swirl and flow. The increase in swirl by air injection via VGJ rises with lower base swirl of the geometry. Notably, the low swirl / high flow scenario achieved a substantial increase in swirl levels comparable to the high swirl case, without compromising airflow, thereby demonstrating the potential to surpass the existing Pareto front through swirl generation using VGJs and suggests a new achievable limit. With air injection the discharge coefficient can be increased by 26 % while maintaining the same swirl level with a different port geometry.