Nozzle configuration and in-cylinder pressure effects on fuel spray behaviour: studies using a rapid cycling machine

Abstract

Efforts to improve the efficiency of internal combustion engines in applications such as heavy-duty vehicles where electric propulsion is currently unfeasible or need complementing are essential. However, studying the conditions of actual internal combustion engines whilst accessing their combustion chambers whilst they are in operation remains difficult. To allow for the characterization of practical operating conditions of diesel engine designs, detailed studies examining the influence of the injector nozzle configuration, peak in-cylinder pressure conditions, and fuel injection pressure values up to 25% greater than those hitherto typically reported using rapid cycling machines for diesel spray diagnosis were carried out. A rapid cycling machine using a production diesel engine piston design, equipped with optical windows and fitted with a high-pressure common rail fuel injection equipment was used with temporal spray liquid and vapour penetration values obtained using Schlieren and Mie scattering imaging techniques for injector nozzles of various k-factor values. Even though the effects of the different injector nozzle conicity values on the fuel spray liquid and vapour penetration values observed were not significant, the studies supported the use of such methods to evaluate the piston and cylinder wall wetting which can have significant effects on the emissions and fuel consumption from internal combustion engines. These are also useful for internal combustion engine design and numerical spray code development.