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An experimental study was conducted to characterize the dynamics and spray behavior of a wide range of minisac and Valve-Covered-Orifice (VCO) nozzles using a high-pressure diesel common-rail system. The measurements show that the resultant injection-rate is strongly dependent on common-rail pressure, nozzle hole diameter, and nozzle type. For split injection the dwell between injections strongly affects the second injection in regards to the needle lift profile and the injected fuel amount. The minisac nozzle can be used to achieve shorter pilot injections at lower common-rail pressures than the VCO nozzle. Penetration photographs of spray development in a high pressure, optical spray chamber were obtained and analyzed for each test condition. Spray symmetry and spray structure were found to depend significantly on the nozzle type.

The combustion and emission characteristics of a high speed, small-bore, direct injection, single cylinder, diesel engine are investigated using two different nozzles, a 430-VCO (0.171mm) and a 320 Mini sac (0.131mm). The experiments were conducted at conditions that represent a key point in the operation of a diesel engine in an electric hybrid vehicle (1500 rpm and light load condition). The experiments covered fuel injection pressures ranging from 400 to 1000 bar and EGR ratios ranging from 0 to 50%. The effects of nozzle hole geometry on the ignition delay (ID), apparent rate of energy release (ARER, ARHR), NOx, Bosch smoke unit (BSU), CO and hydrocarbons are investigated.

The nozzle configuration for an injector is known to have an important effect on the fuel atomization. A comprehensive experimental and numerical investigation has been performed to determine the influence of various internal geometries on the primary spray breakup and development using the electronically controlled high-pressure diesel injection systems. Different types of multi-hole minisac and VCO nozzles with cylindrical and tapered geometries, and different types of single-hole nozzles with defined grades of Hydro Grinding (HG) were investigated. The global characteristics of the spray, including spray angle, spray tip penetration and spray pattern were measured from the spray images with a high-speed drum camera. A long-distance microscope with a pulsed-laser as the optical shutter was used to magnify the diesel spray at the nozzle hole vicinity. A CFD analysis of the internal flow through various nozzle geometries has been carried out with a commercial code.

One of the most challenging problems in diesel engines is to reduce unburned HC emissions that appear as (white smoke) during cold starting. In this paper the research is carried out on a 4-cylinder diesel engine with a common rail fuel injection system, which is able to deliver multiple injections during cold start. The causes of combustion failure at lower temperature limits are investigated theoretically by considering the rate of heat release. The results of this clearly indicate that in addition to low cranking engine speed, heat transfer and blow-by losses at lower ambient temperatures, fuel injection events would contribute to the failure of combustion. Also, combustion failure takes place when the compression temperature is lower than some critical value. Based on these results, split-main injection strategy was applied during engine cold starting and validated by experiments in a cold room at lower ambient temperatures.