Spray Characteristics of Throttle Body Fuel Injection

This paper describes work from an investigation using a Phase/Doppler Particle Analyzer to characterize a throttle body injection system. Spray data are presented from two injectors, a ball type and a pintle type. Tests were performed on externally mounted injectors spraying continuously and under pulsed injection conditions. Further experiments were performed with these injectors mounted in the throttle body to obtain spray data at the throttle body exit under simulated engine operating conditions. Steady injection data from externally mounted injectors show that the pintle injector has better symmetry and spray atomization quality (including a 50 per cent reduction in peak mean drop size) than the ball nozzle. External pulsed tests indicate a severe degradation in spray atomization quality under the idle condition, while increasing the time the injector is open during an injection cycle provides a spray whose time averaged behavior approaches steady injection characteristics. Results at the throttle body exit plane demonstrate strong interactions between the fuel spray and the air flow and throttle body walls. Under idle conditions, exit plane measurements show a finely atomized uniform spray whose droplets are easily accelerated by the air flow, while results from the wide open throttle condition show a wider spray distribution with up to 60 per cent of the fuel spray leaving the throttle body dripping from the walls.