Spray droplet velocity characterization for convergent nozzles with three different diameters (original) (raw)
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Nowadays Diesel nozzle geometry is a major issue in order to fulfil new emission regulations due to the influence on internal flow, cavitation phenomenon, spray characteristics and therefore atomization behavior, which are very important for engines performance and pollutant formation. The aim of this article is to study the effect of cavitation on Diesel spray behavior. For this purpose, two bi-orifices nozzle geometries, a cylindrical nozzle and a convergent one, are characterized by means of two fundamental spray parameters: mass flux and momentum flux. Five injection pressure values and five discharge pressure levels have been measured in order to change the cavitation regime inside the nozzle flow. It is known from the literature that cavitation brings about a mass flux choke, but there are few studies that investigate its effects on momentum and outlet velocity in real geometries. The key point of this study is the measurement of spray momentum in order to explain the effects of nozzle geometry on spray behavior.
Droplet Size and Velocity Distributions of a Transient Hollow-Cone Spray for GDI Engines
Particle & Particle Systems Characterization, 2001
An experimental investigation of a gasoline direct injection (GDI) spray, emerging from an electronically controlled swirl-type injector, was carried out at an injection pressure and duration of 7.0 MPa and 3.0 ms, respectively, in an optically accessible vessel, at atmospheric pressure and ambient temperature. The temporal and spatial spray evolution was investigated in terms of global spray structure, interaction with the external gas, time-resolved droplet size and velocity distribution. The measurements were carried out with an AVL Engine Video System with a CCD camera, a frame grabber and a strobe flash triggered by the injection apparatus. Digital image processing software for the study of the global parameters of the spray was used. A particle Doppler analyzer (PDA) system was used to estimate the local droplet size and velocity as function of the radial coordinate and distance from the nozzle. A laser light extinction technique was applied to investigate the region close to the nozzle up to 5 mm.
Characteristics of droplet motion in effervescent sprays
EPJ Web of Conferences, 2014
Time resolved droplet size and velocity measurement was made using Phase-Doppler anemometry in an effervescent spray at GLR of 6 % and operation pressure drops 21 -52 kPa. The spray shows a size dependent variation of mean as well as fluctuating axial and radial velocities of droplets similarly for all operation regimes. Particles under 13 μm follow the gas flow, axially decelerated due to gas expansion. Velocity of medium sized particles is positively size correlated and larger particles keep high velocity, given them during discharge. Fluctuating radial velocity of small particles is larger than that of large particles while fluctuating axial velocity increases with size. Small particles thus reach a ratio of radial to axial velocity fluctuations ~ 0.6 but large particles only ~ 0.1, which indicates large transverse dispersion of small particles. Overall fluctuating velocity ratios smaller than 0.5 document an anisotropic character of the liquid mass fluctuations. Power spectral density (PSD) of axial velocity fluctuations of large droplets is uniform up to 1 kHz, while PSD of smaller particles drops down with frequency for frequencies > 100 Hz. Large particles thus preserve the fluctuations imposed during discharge while the gas turbulence drops with frequency. Turbulence intensity reaches 14 to 21 % depending on pressure. Such high-turbulence character of the flow probably results from a heterogeneous gas-liquid mixture at the discharge. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Velocity field analysis of the high density, high pressure diesel spray
International Journal of Multiphase Flow, 2016
In this study, particle image velocimetry (PIV) measurements have been performed extensively on a nonreactive dense diesel spray injected from a single orifice injector, under various injection pressure and steady ambient conditions, in a constant flow chamber. Details of PIV setup for diesel spray measurement without additional seeding are explained first. The measured velocity profiles are compared to those obtained from other similar measurements performed in a different institution, as well as those obtained from a 1D spray model simulation, presenting in both cases a good level of agreement. In addition, the velocity fields under various injection pressures and ambient densities show the dominant effects of these parameters on the behavior of diesel spray. The self-similarity of the transverse cut profiles of axial velocity is evaluated, showing that the measurements are in agreement with the hypothesis of self-similar velocity profiles. Finally, the effect of injection pressure and ambient density on the velocity fluctuations is presented and analyzed as well. While the experimental results presented here could help to understand the complex diesel fuel-air mixing process during injection, they also provide additional spray velocity data for future computational model validation, following the main idea of the Engine Combustion Network.
Liquid Spray Characterization Using Phase /Doppler Technique.(Dept.M)
2021
Spray characleriSlics of Ihree liquids, waler. diesel fue l. and kerosene. sprayed vcnica lly downward in a transparent squared section rube which IS accessed wilh an exhausler> Ihrough Doppler Particle a pressure SWi rl 'lIomizer, have been evaluated b~ means of Phase Ana lyzer (PIDPA) syslem. The experimental apparacus is accessed wilh a lfa ..-erSlOg syslem whic h enables 10 make complele scan. radially and axially, for the spra:-cone. Differenl pressure d ifferenlials across the nozzle are applied \0 study their effeci on sprn:-r charoclerislics. Measurements of drop lei mean diameter, droplet size distribution. droplet mean velocity , liquid volume nux and droplel number density have !xen carried out. Experimental results showed that the droplet size increases and droplet axial mean velocity decreases as the radial distance from spray axis increOlSes. Also, as the axial
Droplet diameter measurement near a nozzle exit of a common-rail Diesel injector using PDA
International Conference on Liquid Atomization and Spray Systems (ICLASS), 2021
The purpose of this study is to measure the droplet diameter distribution very close to the nozzle hole of a common-rail Diesel injector using a phase Doppler anemometer (PDA). Experimental investigations of atomization process were restricted due to very high-speed and very dense spray region phenomena in the case of the spray from the common-rail injection. In this experiment, droplet diameter and axial velocity in spray formed by one hole of the common-rail Diesel injector were measured with HiDense PDA system to investigate atomization characteristics near the nozzle exit of the common-rail Diesel injector. HiDense PDA system permits accurate measurements in spray with extremely high particle concentrations, and it is the only PDA system available that provide high quality measurements in the core region of the spray cone. Optimization of optical setup and measurement condition of signal processor were carried out to measure the accurate droplet diameter distribution very close to the nozzle exit under higher injection pressure conditions. It is possible to measure the droplet diameter distribution at the 10mm from the nozzle exit under 100MPa as the injection pressure. Radial distributions of droplet velocity were measured using HiDense PDA system. At 10 mm from the nozzle exit, there are strong shear layer between the surround air and injected spray. Narrower droplet distribution can be seen at 10 mm from the nozzle exit.
Droplet size development in a DISI injector fuel spray
2016
In this work, Phase Doppler Anemometry (PDA) measurements are used to test the hypothesis that the mean droplet size in Direct Injection Spark Ignition (DISI) engine fuel spray increases with distance from the injector due to the evaporation of the smaller droplets. In order to understand the role of evaporation, two velocity components and drop size PDA measurements were performed for one plume of a DISI injector using two fuels with widely differing vapour pressures. The measurements were taken along the plume centreline at four different vertical distances from the injector tip between 20 to 50 mm. on the plume centreline to evaluate the development of droplet size distributions along the plume. Measurements are also made across the plume (perpendicular to the plume centreline) at the 30 and 50 mm locations. Measurements using PDA closer to the injector are more difficult due to the high spray density (particularly apparent at 20mm or closer to the injector). A data fitting proce...
Flow regime effects on non-cavitating injection nozzles over spray behavior
This paper deals with the influence of flow regime (laminar, transition or turbulent) on the internal flow behavior, and how it affects the spray development in diesel nozzles. In particular, the research described here aims at studying and quantifying the internal flow regime effects on the spray behavior. With this purpose, internal flow results, based on mass flow rate and momentum flux measurements performed on three different tapered nozzles and which helped to determine the flow regime, has been taken into account as a point of departure for the spray behavior analysis. Thus, in this work, spray macroscopic visualization tests have been performed and analyzed which clearly revealed a change in the behavior of the angle and penetration of the spray related to the change of the flow nature. Moreover, with all the experimental data available, it has been possible to relate macroscopic parameters of the spray with those describing the internal flow (momentum and effective velocity) or the geometry of the nozzle (length or diameter) through correlations.