Effect of nozzle transients and compressibility on the penetration of fuel sprays

Abstract

A study has been performed using a combination of high speed optical imaging and a synchrotron based technique to obtain a time history of nozzle exit velocity, discharge coefficient, and spray tip velocity of high pressure fuel sprays. The results support a recently proposed theoretical model of spray propagation that suggests a compressible region of flow immediately ahead of the spray has a strong influence on the evolution of the tip velocity profile. Coupled with this is the variation in discharge coefficient due to injector needle movement which largely governs the spray exit velocity immediately after start of injection.

Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle

“…The introduction of this time-shift is motivated by different reasons: on one hand, the atomization and mixing process is not clearly understood in the near-field and the complete momentum transfer assumption of the 1D model might not be appropriate; on the other hand, the mass flow rate measurements (used as an input for the 1-D model) are not reliable during the opening phase [24] and contribute to the discrepancies between the experiments and the model predictions; moreover, in the near field, the spray tip velocity is of the same order of magnitude of the atmosphere gas speed of sound and, therefore, spray jet -shock wave interactions are expected [25]. However, after this first changed, both the spreading angle and the time shift need to be changed.…”

Estimation of a suitable Schmidt number range in diesel sprays at high injection pressure

“…In this sense, Argonne National Laboratories have developed a technique for quantifying projected density distribution inside the spray based on X-ray absorption. The advantage of using X-rays is that while other radiations in the electromagnetic spectra (as for example visible light) are rapidly attenuated by fuel particles, intensity loss for the X-rays is much lower, so that it can be used even in the densest zones of the spray [31]- [34].…”

Spray flow structure from twin-hole diesel injector nozzles

“…In the LTRAC experiments, standard ultra-low sulphur automotive diesel with a measured density q l at room temperature of 830 kg/m 3 was used. This fuel was also used for the single-hole nozzle X-ray radiography APS data [2]. For the twin-hole nozzle APS experiments, the diesel (Viscor 1487) was doped with a cerium additive (Rhodia DPX9) to enhance absorption giving a measured density at room temperature of 874 kg/m 3 .…”

“…Because of the experimental advantages to their use, particularly in optimizing the spatial resolution of the measurement domain, single-hole nozzles (SHNs) have been a significant focus of many of these past studies [1][2][3][4][5][6][7]. There is however a growing recognition of the need to study nozzles which are more representative of the multi-hole nozzles used in engines (e.g.…”