Browse Publications Technical Papers 2009-24-0053
2009-09-13

An Experimental Study of Cluster Nozzles for DI Diesel Engine 2009-24-0053

In a conventional Diesel engine, air is gradually drawn into the fuel spray from the surrounding area. The ignition delay period is short, so combustion starts before the fuel has thoroughly mixed with the air. Consequently, the center of the spray is overly rich, resulting in smoke, while a stoichiometric mixture is formed in the surrounding area, resulting in a high NOx concentration. Based on the Diesel concept it is practically impossible to totally avoid fuel rich and stoichiometric pockets, but the formation of soot and NOx are also time dependent. If the mixing time is sufficiently small both pollutants could be reduced simultaneously without getting into the well known soot-NOx tradeoff. In order to develop a low emission engine, research is necessary to come up with a new combustion strategy for Diesel engines, which includes the use of cluster nozzles. Conditions for low raw particulate emission are: suitable start of injection, lean air/fuel mixture, sufficiently high temperatures in the combustion chamber and a sufficient retention time with these conditions. This could be achieved by use of cluster nozzles and a careful tuning of the air/fuel mixing parameters of the engine piston geometry. Decreasing the hole-size improves mixing in the center of the spray and therefore the soot production goes down tremendously. It has been observed, that an optimum number of holes exists (6 to 8) and that a certain swirl level is necessary. Based on this experience the cluster concept was developed. The cluster nozzles can also be used for improved homogenization of in-cylinder charge so as to enable a partly homogenous mode of Diesel combustion. In this study, three cluster designs are investigated through engine measurements. They were tested in a single-cylinder engine with CRI 3.3 piezo injectors under part-load conditions for a partly homogenous mode of Diesel combustion, and also under high load conditions for conventional Diesel combustion. The experimental studies give some detailed information on how cluster nozzles could help in lowering soot formation and thereby provide more freedom to reduce other pollutants.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:
TECHNICAL PAPER

Numerical Analysis of the Role of Initial Combustion on Reduction of NO and Soot from DI Diesel Engines

2000-01-2035

View Details

TECHNICAL PAPER

In-Cylinder Control of Smoke and NOx by High Turbulent Two-Stage Combustion in Diesel Engines

962113

View Details

TECHNICAL PAPER

Fuel Injection Effect on In-cylinder Formation and Exhaust Emission of Particulate from a 4-Stroke Engine for 2-Wheel Vehicles

2010-01-0354

View Details

X