Proceedings of Internal Combustion Engines Division Spring Technical Conference ICED 2012 May 6-9, 2012, Torino, Italy ICES2012-81223 DRAFT: UNDERSTANDING THE ACOUSTIC OSCILLATIONS OBSERVED IN THE INJECTION RATE OF A COMMON-RAIL DI DIESEL INJECTOR Julien Manin ∗ Sandia National Laboratories Combustion Research Facility 7011 East Avenue Livermore, CA 94551 Alan Kastengren Argonne National Laboratory Center for Transportation Research 9700 South Cass Avenue, Building 362 Argonne, IL 60439 Raul Payri CMT - Motores Termicos Universidad Politecnica de Valencia Camino de Vera s/n Valencia, Spain ABSTRACT Measuring the rate of injection of a common-rail injector is one of the first steps for diesel engine development. At the same time, this information is of prime interest for engine research and modeling as it drives spray development and mixing. On the other hand, the widely used long-tube method provides results that are neither straightforward, nor fully understood. This study performed on a 0.09 mm axially drilled single-hole nozzle is part of the Engine Combustion Network (ECN) and aims at analyzing these features from an acoustic point of view to separate their impact on the real injection process and on the results recorded by the experimental devices. Several tests have been carried out for this study including rate of injection and momentum, X-ray phase-contrast of the injector and needle motion or injector dis- placement. The acoustic analysis revealed that these fluctua- tions found their origin in the sac of the injector and that they were the results of an interaction between the fluid in the cham- ber (generally gases) and the liquid fuel to be injected. It has been observed that the relatively high oscillations recorded by the long-tube method were mainly caused by a displacement of the injector itself while injecting. In addition, the results showed that these acoustic features also appear on the momentum flux of the spray which means that the real rate of injection should present such behavior. ∗ Address all correspondence to this author: Email: jmanin@sandia.gov INTRODUCTION Spray development and mixing are the key parameters con- cerning combustion efficiency and pollutant emissions in diesel engines currently in production. The characteristics of the spray are strongly influenced by the properties of the flow of fuel in- jected into the combustion chamber [1]. Knowing and under- standing the properties of the flow at the outlet of an injector’s orifice is therefore crucial for the development of CFD models that accurately predict spray mixing and combustion. At the same time, experimental techniques such as rate of in- jection or spray momentum flux are available to the researcher to hydraulically characterize the flow at the outlet of an orifice [2]. However, these techniques fail to provide reliable signals con- cerning the injection rate due to the fact that the uncertainties surrounding the signals are still not fully understood. Developed by Bosch, the long-tube method [3] certainly presents the most used solution to record injection rate in a time domain. Though, the signal generated by the commercial system employing this method generally called Injection Discharge Rate Curve Indica- tor (IRDCI) shows oscillations of higher amplitude than that dis- played in the signal coming from spray momentum experiments for example (particularly for single-hole nozzles) [4]. Consequently, unidimensional models have been success- fully used to predict the rate of injection but they appear not to match and accurately describe the acoustic of the flow at the orifice exit [5]. In addition, these models are generally based on nominal dimensions whereas variations from orifice to orifice 1 Copyright c  2012 by ASME