2005-01-2094 Comparison between different hole to hole measurement techniques in a Diesel injection nozzle F. Payri, R. Payri, F.J. Salvador, J. Gimeno CMT Motores Termicos, Universidad Politécnica de Valencia, Spain Copyright © 2005 SAE International ABSTRACT In order to study differences between Diesel nozzle holes, four methodologies have been tested. The techniques compared in this paper are: the internal geometry determination, hole to hole mass flow measurement, spray momentum flux and macroscopic spray visualization. The first one is capable of obtaining the internal geometry of each of the orifice of the nozzle; the second one is capable of measuring the mass flow of each nozzle hole in both, continuous and real injections. The third one gives the momentum flux of each orifice, and finally, with the macroscopic spray visualization, the spray penetration and spray cone angle of each hole, are obtained. Generally, all these techniques can be used in order to determine the hole to hole dispersion due to different angle inclination of the holes, different internal geometry of orifices, deposits, nozzle needle off-center, needle deflection, etc. Moreover, the results obtained from theses techniques are a very useful tool in order to study the injection process. Special attention deserves the new capability developed to carry out the hole to hole mass flow measurement. In fact, although Diesel nozzle mass flow measurement, either injection rate or continuous mass flow, is a technique widely used, it has the disadvantage that the complete nozzle mass flow is characterized without a distinction between the mass flow from each of the orifices. Here, a new test rig is presented in order to achieve this kind of measurements. INTRODUCTION In modern Diesel engines, especially in high-speed direct injection engines, the performance, efficiency, noise and pollutant emissions have a strong dependency on the characteristics of fuel injection. Nowadays, the amount of fuel injected is not only the most relevant characteristic of the injection process. The instantaneous fuel mass flow rate introduced into the combustion chamber, the evolution of the spray and its interaction with the air are also important [1-4]. One important phenomenon in this process is the flow behavior across the nozzle holes in the injectors, which is influenced by nozzle geometry and which affects spray characteristics and therefore atomization process (droplet formation) and fuel-air mixing [3-7]. Atomization and the fuel-air mixing are decisive for engine performance and pollutant formation. The most influential parameters on droplet formation and fuel-air interaction are fuel injection rate, spray momentum and orifice effective flow area. These parameters can be affected by other phenomena as cavitation [3, 4, 6, 8- 13]. Nowadays Direct Injection Diesel engines are equipped with multi-hole nozzles. The intention of using multi-hole nozzles is to improve the fuel-air mixing process inside the combustion chamber. Nevertheless, this kind of nozzles, can be affected, as stated before, by hole to hole dispersion which can affect the uniformity and so the combustion performance. In the present paper four measurement techniques are going to be compared to evaluate the uniformity of fuel mass distribution of injectors with multi-hole nozzles. These techniques are: internal geometry determination with the silicone technique [3, 14], mass flow measurement over each orifice of the nozzle, spray momentum [4, 12] and spray macroscopic visualization [3, 6, 8, 15-17]. As an example, the four methodologies will be used in order to study the hole to hole variations in a micro-sac nozzle with three symmetric holes which have different internal geometry. In this case, therefore, only differences related to the nozzle manufacture process are expected. The paper is divided into three main sections. The first section gives a brief description of the experimental capabilities that will be used with a description of the four methodologies. Next, the results obtained in the different test rig are described and compared with each other, and finally a conclusion summary is presented.