CFD Analysis of Pintle-Nozzle Spray for Swirl Chamber Type Small Diesel Engine -Application of Hole-Nozzle Atomization Model to Pintle-Nozzle

Swirl chamber combustion system is commonly used for IDI (In-Direct Injection) diesel engine. It is characterized by swirl combustion chamber arranged in cylinder head, main combustion chamber with shallow piston recess and connecting throat where fuel spray and flame mixture is ejected out from the swirl chamber to the main chamber [1]. Fuel is supplied in the swirl chamber and a pintle type nozzle is often used in this type engine as its simple structure and robustness for operating condition.

In this paper, numerical simulation of a pintle nozzle spray was focused on and simulated results were compared with high speed photo data obtained in a constant volume vessel (CVV). Spray angle and tip penetration were mainly evaluated, but simulated angle and penetration could not be matched simultaneously to these characteristics of the pintle nozzle spray when conventional spray models were used for the simulation. To overcome this mismatch, “Multi-hole replacement model” was newly introduced. In this model, annular liquid sheet was treated as a circular bundle of liquid columns and hole-nozzle breakup model is applied to each liquid column. Fundamental concept of “Multi-hole replacement model” and practical application procedure were explained here. This proposed spray model will be applied actual engine model for the next step and contribute to expand the scope of application of IDI engines.