Characteristics of Nozzle Internal Flow and Near-Field Spray of Multi-Hole Injectors for Diesel Engines

Multi-hole nozzles have a wide range of application in the fuel supply system of modern diesel engines, although single-hole nozzles dominate basic internal flow and spray research. The parameters of the nozzle geometry are crucial factors that can alter the internal flow dynamics of the nozzle and the consequent spray behaviours. The novelty of this study lies in implementing the application of practical prototype mini-sac multi-hole diesel nozzles to experimental and numerical studies. The internal flow and spray characteristics generated by practical multi-hole (10-hole) nozzles with different sac wall thicknesses (0.4 mm, 0.6 mm and 0.8 mm) were investigated in conjunction with a series of experimental and computational methods using a constant injection quantity (2 mm3/hole). Globally, the analysis mainly concentrated on different nozzle flow dynamics, different injection processes and different spray morphologies. Specifically, the high-speed video observation method was applied to visualize the injection processes and the spray evolution of different nozzles inside a high-pressure vessel. Furthermore, numerical simulations were conducted to reveal the three-dimensional nature of the internal flow inside different configurations; this was instructive in helping us to understand better the mechanism behind the spray behaviours. The results indicate that intense cavitating, turbulent and spiral rotating flow patterns occur inside practical multi-hole nozzles, and the consequent sprays emerging from the nozzles are perturbed, asymmetrical and unstable in both the near field and the far field. Moreover, a decrease in the nozzle hole length can increase the effects of cavitation, turbulence, the void fraction and the axial and radial injection velocity components on the nozzle hole exit; this is accompanied by an intriguing longer injection duration, wider near-field and far-field spray widths, a lower injection rate, and overlapping or even shorter spray propagation. However, these changes are not linear, and different parameters have different sensitivities to the variation in the nozzle hole length.

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PREDICTION OF NOISE GENERATED BY A ROUND NOZZLE JET FLOW USING COMPUTATIONAL AEROACOUSTICS

Journal of Computational Acoustics ◽

10.1142/s0218396x11004365 ◽

2011 ◽

Vol 19 (03) ◽

pp. 291-316 ◽

Cited By ~ 23

Author(s):

ALI UZUN ◽

M. YOUSUFF HUSSAINI

Keyword(s):

Flow Field ◽

Near Field ◽

Internal Flow ◽

Jet Flow ◽

Computational Aeroacoustics ◽

Far Field ◽

Free Jet ◽

Grid Points ◽

Field Noise ◽

Inflow Conditions

This paper demonstrates an application of computational aeroacoustics to the prediction of noise generated by a round nozzle jet flow. In this study, the nozzle internal flow and the free jet flow outside are computed simultaneously by a high-order accurate, multi-block, large-eddy simulation (LES) code with overset grid capability. To simulate the jet flow field and its radiated noise, we solve the governing equations on approximately 370 million grid points using high-fidelity numerical schemes developed for computational aeroacoustics. Projection of the near-field noise to the far-field is accomplished by coupling the LES data with the Ffowcs Williams–Hawkings method. The main emphasis of these simulations is to compute the jet flow in sufficient detail to accurately capture the physical processes that lead to noise generation. Two separate simulations are performed using turbulent and laminar inflow conditions at the jet nozzle inlet. Simulation results are compared with the corresponding experimental measurements. Results show that nozzle inflow conditions have an influence on the jet flow field and far-field noise.

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Local, Near-Field Mixing Augmentation Using Square Coaxial Jets

Volume 1: Turbo Expo 2004 ◽

10.1115/gt2004-53985 ◽

2004 ◽

Author(s):

Samuel Bonnafous ◽

Victor Piffaut ◽

Wai-Ho Choy ◽

Dimitris E. Nikitopoulos

Keyword(s):

Near Field ◽

Internal Flow ◽

Spreading Rate ◽

Central Plane ◽

Mean Velocity ◽

Mixing Rates ◽

Spreading Rates ◽

Diagonal Plane ◽

Axis Switching ◽

First Time

Results from un-forced experiments in flows ensuing from circular and equivalent square coaxial nozzles with parallel sides are presented in this paper. The nozzles are contoured and are designed so that the hydraulic diameters of the internal flow passages are identical for both geometries. The flow experiments were conducted at a co-flow-jet Reynolds number of Re = 16,000 and inner-to-outer jet nominal velocity ratios of λ = 0, 0.5, 1.5. Axis switching, a phenomenon readily observed in single non-axisymmetric nozzles, is shown for the first time to occur in the square coaxial nozzles as well. Comparisons of the mixing regions of the flows from both geometries are made to examine mixing advantages when using square nozzle configurations. Comparisons of stream wise mean velocity fields measured on a center plane parallel to the square nozzle sides, on a diagonal plane of the square nozzle and the center plane of the corresponding circular nozzle, are presented and discussed. Axis switching is shown to be evident in the near-field shear regions for all velocity ratios, resulting in considerable mixing advantages. The spreading rates (and therefore mixing rates) of the outer mixing region of the square nozzles clearly exceed the spreading rate observed in the circular case on the central plane. Axis switching and improved mixing is also observed in the inner mixing region of the square nozzle. This work is relevant to coaxial nozzles for gas turbine combustor applications, although the study has been carried out in a scaled up geometry with respect to this application.

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Characterization of Internal Flow of Intersecting Hole Nozzle for Diesel Engines

10.4271/2015-01-1860 ◽

2015 ◽

Cited By ~ 1

Author(s):

Xianyin Leng ◽

Zhixia He ◽

Yu Jin ◽

Wenjun Zhong ◽

Wuqiang Long

Keyword(s):

Diesel Engines ◽

Internal Flow

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The near-field flow characteristics of some wall-mounted mixing tabs

The Aeronautical Journal ◽

10.1017/s0001924000027925 ◽

1999 ◽

Vol 103 (1023) ◽

pp. 253-256

Author(s):

S. C. M. Yu ◽

L. P. Chua ◽

E. K. Goh

Keyword(s):

Boundary Layers ◽

Near Field ◽

Flow Characteristics ◽

Vortex Generator ◽

Internal Flow ◽

Vortex Generators ◽

Streamwise Vortices ◽

Internal Flows ◽

Distortion Control ◽

Flow Feature

It is well known that passive vortex generators can be very effective in controlling separation by ‘re-energising’ the low momentum fluids at the boundary layers. They have been used extensively in many practical aerodynamic applications; both in external and internal flows. Typical examples include aerofoil stall alleviation and engine face distortion control in the jet aircraft intake during high angles of incidence. The general flow feature behind a vortex generator is that a pair of contra-rotating streamwise vortices would be formed which will significantly strengthen the flow at the boundary layers. However, the rationale for successful vortex generator designs is often poorly understood. In many cases, vortex generator designs have even been shown to be arbitrary. Anderson et al and Reichert and Wendt used rectangular fin and tapered fin vortex generators respectively, to eliminate the internal flow separation of S-shaped intake ducts. Both geometries were found to be equally effective. Weng and Guo successfully applied aerofoil shape type of vortex generators to suppress the swirl on the engine face of an S-shaped intake duct at high angles of incidence.

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The effect of transient needle lift on the internal flow and near-nozzle spray characteristics for modern GDI systems investigated by high-speed X-ray imaging

International Journal of Engine Research ◽

10.1177/1468087420986751 ◽

2021 ◽

pp. 146808742098675 ◽

Cited By ~ 1

Author(s):

Dmitrii Mamaikin ◽

Tobias Knorsch ◽

Philipp Rogler ◽

Jin Wang ◽

Michael Wensing

Keyword(s):

High Speed ◽

Near Field ◽

Internal Flow ◽

Transient Behavior ◽

Liquid Jet ◽

Nozzle Flow ◽

Spray Characteristics ◽

X Ray ◽

X Ray Imaging ◽

Primary Breakup

The development of the injector nozzle is a dynamic area in regard of several technical aspects. At first, the internal flow influences the near-field spray characteristics via various phenomena such as cavitation and turbulence. However, these phenomena are not fully understood due to their extremely fast, complex and multiscale nature. Furthermore, it governs the spray targeting inside the combustion chamber. High-speed X-ray imaging of GDI injector nozzles is performed in this study. The experimental results presented are related to the internal flow and primary breakup of discharged liquid jets. The injectors used are equipped with nozzles made of aluminum which have been specially developed for these investigations to enhance optical accessibility. The visualization of the needle motion, in-nozzle flow and the primary breakup region provides several exciting observations. First, the needle lift tracking exhibits short overshooting right before the steady-state of the injection phase. This event leads to a short-term, however, significant change in the associated performance of the breakup. This phenomenon is found to be a consequence of the transient behavior of the in-nozzle flow. It is shown that under some circumstances hydraulic flip may occur during this overshooting period. The primary jet breakup region is visualized and evaluated by means of image processing. Thus, the transient behavior of liquid jet expansion is quantified in the vicinity of the nozzle. It is observed that the liquid jet direction deviates from the hole axis already at the nozzle outlet, which is caused by internal flow characteristics.

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The effect of nozzle internal flow on spray atomization

International Journal of Engine Research ◽

10.1177/1468087419875843 ◽

2019 ◽

Vol 21 (1) ◽

pp. 55-72 ◽

Cited By ~ 7

Author(s):

Arpit Agarwal ◽

Mario F Trujillo

Keyword(s):

Axial Velocity ◽

Near Field ◽

Liquid Core ◽

Mean Field ◽

Internal Flow ◽

Two Phase ◽

Surface Features ◽

Nozzle Orifice ◽

Core Length ◽

Nozzle Configuration

The effect of nozzle surface features on the overall atomization behavior of a liquid jet is analyzed in the present computational work by adopting three representative geometries, namely a single X-ray tomography scan of the Engine Combustion Network’s Spray A nozzle (Unprocessed), a spline reconstruction of multiple scans (Educated), and a purely external flow configuration. The latter configuration is often used in fundamental jet atomization studies. Numerically, the two-phase flow is solved based on algebraic volume-of-fluid methodology utilizing the OpenFoam solver, interFoam. Quantitative characterization of the surface features concerning the first two geometries reveals that while both of them have similar levels of cylindrical asymmetries, the nozzle configuration pertaining to the Unprocessed geometry has much larger surface features along the streamwise direction than the Educated geometry. This produces for the Unprocessed configuration a much larger degree of non-axial velocity components in the flow exiting the orifice and also a more pronounced disturbance of the liquid surface in the first few diameters downstream of the nozzle orifice. Furthermore, this heightened level of surface destabilization generates a much shorter intact liquid core length, that is, it produces faster primary atomization. The surprising aspect of this finding is that the differences between the Unprocessed and Educated geometries are of [Formula: see text](1) μm, and they are able to produce [Formula: see text](1) mm effects in the intact liquid core length. In spite of more pronounced atomization for the Unprocessed geometry, the magnitude of the turbulent liquid kinetic energy is roughly the same as the Educated geometry. This highlights the important role of mean field quantities, in particular, non-axial velocity components, in precipitating primary atomization. At the other end of the spectrum, the external-only configuration has the mildest level of surface disturbances in the near field resulting in the longest intact liquid core length.

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