Surface Synthetic Jet Actuators for Flow Control Applications in Internal Combustion Engines

Charge motion in internal combustion engines is controlled by valves located near the engine ports in the intake path. The valve bodies are obstructions in the air-flow path and are a source of inefficiencies in the engine over its entire operating load. In order to achieve charge motion control without the use of valves, this research investigates the use of synthetic jet actuators to perform swirl and tumble of the air mass entering the cylinder. The purpose of this research is to design, test, and characterize a synthetic jet actuator, and determine the feasibility of using synthetic jet actuators in automotive air-intake systems. The accomplished work to date has led to geometrical optimization, fabrication of a prototype, and experimental investigation for determining jet velocities. The geometrical optimization of synthetic jets has led to a device with a thinner profile that allows it to be embedded in structures with thin (< 5mm) cross-sections and hence we refer to our synthetic jets as surface synthetic jets. It is shown here that air exiting the surface synthetic jets achieves sustained peak velocities well above 125 m/s. A variational principles-based approach is used to model the frequency response of the piezoelectric diaphragm, coupled with the lumped-parameter model for the surface synthetic jets and simulated using MATLAB Simulink^®. The results of this model are validated with experimental results and extended to design charge motion control devices. From these results, it is anticipated that these surface synthetic jet actuators can achieve charge motion control using a radial array of surface synthetic jet actuators distributed around the intake runner.