Effect Of Injector Geometry Research Articles

Effect of injector geometry in breakup of liquid jet in crossflow – insights from POD

The present study aims to investigate the role of injector geometry, particularly injector tube length to diameter ratio (L/D) in liquid jet stability and breakup in presence of crossflow. Water is injected into a crossflow of air. Aerodynamic Weber number (We) and liquid Reynolds number (Rel) are systematically varied to observe various breakup modes. Bag breakup and surface stripping is observed for different operating conditions. Time-resolved jet trajectory images are processed using Proper Orthogonal Decomposition (POD) algorithm. POD mode shapes and corresponding Power Spectral Density (PSD) plots are analyzed to study breakup process and probe role of injector geometry effects. Further, high-resolution images are captured for the near-nozzle region. Detailed comparison is made for various cases. It is observed that with increase in (L/D), the jet surface becomes more turbulent and unstable. This results in early breakup and lower jet penetration

The effects of injector geometry and operating conditions on spray mass, momentum and development using high-pressure gasoline

High fuel injection pressure (>500 bar) in direct injection gasoline engines is an important means to reduce particulate emissions. While decades of fuel spray research has dramatically advanced the understanding high-pressure diesel fuel sprays, few studies focus on high-pressure gasoline sprays. The objective of this work was to quantify the effects of different injector nozzle geometries on important high-pressure gasoline spray characteristics including injection mass flow rate, momentum flux, and spray imaging at evaporative and non-evaporative conditions. Three categories of nozzle internal geometry were evaluated: inlet rounding; converging-, diverging-, and straight-cylindrical internal flow passages; and different nozzle outlet diameters. Reference grade gasoline was used at injection pressures of 600, 900, 1200, and 1500 bar at chamber pressures from 1 to 30 bar and chamber temperatures from 293 to 800 K. Two fuel injector temperatures of 293 K and 363 K were studied. The mass and momentum measurements were used to quantify differences in injector geometry as well as to evaluate for effects of cavitation. The visualization data were analyzed to determine spray penetration and spray angle development for a broad range of operating and state conditions. The results showed internal flow significantly impacts injector performance, where nozzles with inlet rounding resulted in 20% higher mass flow rate compared with straight cylindrical nozzles. Higher fuel injector temperatures also increased mass flow rate by up to 5%. Spray momentum coefficients showed a linear relationship with cavitation number indicating all nozzles were cavitating at all conditions tested. Trends in fuel spray penetration and spray angle development were similar to those observed previously for diesel sprays, which was unexpected given the significant differences in thermal-physical properties of the fuels. Chamber pressure had the strongest influence on penetration distance, and the momentum measurements were good indicators of the injector geometry with the highest penetration distance.

Effects of Injector Geometry on Cryogenic Shear Coaxial Jets at Supercritical Pressures

For shear coaxial injectors, which are widely used in liquid oxygen–gaseous hydrogen rocket engines, the key parameters that characterize injector geometry are the recess length, taper angle, and wall thickness of the liquid oxygen post, which is the inner tube of the coaxial injector. In the present study, the effects of the recessed length and taper angle of the liquid oxygen post on cryogenic coaxial jets at supercritical pressures were experimentally investigated. The large-scale structure and mixing enhancement of cryogenic nitrogen and gaseous helium coaxial jets were evaluated using a high-speed backlighting technique. Instantaneous backlit images revealed that the dark core, which is believed to be dense nitrogen, exhibited sinusoidal forms induced by the presence of the outer helium jets. However, the sinusoidal oscillations were less influenced by the injector geometry. The mixing enhancement of coaxial jets was evaluated with respect to the dark-core length and the jet spread angle. The recessed liquid oxygen post enhanced the mixing of cryogenic nitrogen when the recess length was sufficiently large, which suggests that a recess of a certain length is required to improve the mixing of cryogenic coaxial jets at supercritical pressures. Because the decrease in the dark-core length with the recessed length was consistent with the increase in the jet spread angle at the injector exit, the mixing enhancement caused by the recess can be regarded as a result of an improvement in the mixing between the inner and outer jets in the recessed region. The effects of the liquid oxygen post exit taper on the mixing enhancement were more significant than those of the recess. The decrease in the dark-core length with the inner-to-outer momentum flux ratio ( number) is consistent with the relevant empirical correlation at supercritical pressures. Therefore, the mixing enhancement caused by the liquid oxygen post exit taper can be considered the result of an increase in the number, rather than the result of giving azimuthal velocity to the cryogenic nitrogen jet at the liquid oxygen post exit.

Effects of the injector geometry on a sonic jet into a supersonic crossflow

Large-eddy simulation of a sonic injection from circular and elliptic injectors into a supersonic crossflow has been performed. The effects of injector geometry on various fundamental mechanisms dictating the intricate flow phenomena including shock/jet interaction, jet shear layer vortices and their evolution, jet penetration properties and the relevant turbulence behaviors have been studied systematically. As a jet issuing transversely into a supersonic crossflow, salient three-dimensional shock and vortical structures, such as bow, separation and barrel shocks, Mach disk, horseshoe vortex, jet shear layer vortices and vortex pairs, are induced. The shock structures exhibit considerable deformations in the circular injection, while their fluctuation becomes smaller in the elliptic injection. The jet shear layer vortices are generated at the jet periphery and their evolution characteristics are analyzed through tracing the centroid of these coherent structures. It is found that the jet from the elliptic injector spreads rapidly in the spanwise direction but suffers a reduction in the transverse penetration compared to the circular injection case. The turbulent fluctuations are amplified because of the jet/crossflow interaction. The vertical Reynolds normal stress is enhanced in the downstream of the jet because of the upwash velocity induced by the counter-rotating vortex pair.

Effect of injector geometry on the performance of an internally mixed liquid atomizer

This paper presents the results of an experimental study of the effect of injector's geometry on the performance of an internally mixed, air-assisted, liquid injector. In this type of injector a small amount of air is injected into a liquid stream within the injector. The interaction of the liquid with the atomizing air inside the injector induces atomization. The results presented in this paper show that the size of the droplets produced by the investigated injector decreases with a decrease in the air injection area. This is due to the increase in atomizing air injection velocity that accompanies the decrease in the air injection area, which improves atomization. This study also shows that the droplet sizes decrease with an increase in the injector's length, which is attributed to the increase in total interactive force.

Field Studies on the Formation of Sinking CO2 Particles for Ocean Carbon Sequestration: Effects of Injector Geometry on Particle Density and Dissolution Rate and Model Simulation of Plume Behavior

We have carried out the second phase of field studies to determine the effectiveness of a coflow injector which mixes liquid CO2 and ambient seawater to produce a hydrate slurry as a possible CO2 delivery method for ocean carbon sequestration. The experiments were carried out at ocean depths of 1000-1300 m in Monterey Bay, CA, using a larger injector than that initially employed under remotely operated vehicle control and imaging of the product. Solidlike composite particles comprised of water, solid CO2 hydrate, and liquid CO2 were produced in both studies. In the recent injections, the particles consistently sank at rates of approximately 5 cm s(-1). The density of the sinking particles suggested that approximately 40% of the injected CO2 was converted to hydrate, while image analysis of the particle shrinking rate indicated a CO2 dissolution rate of 0.76-1.29 micromol cm(-2) s(-1). Plume modeling of the hydrate composite particles suggests that while discrete particles may sink 10-70 m, injections with CO2 mass fluxes of 1-1000 kg s(-1) would result in sinking plumes 120-1000 m belowthe injection point.

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices.

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.

Effects of injector geometry on scramjet combustor performance

An experiment was conducted to investigate the effect of injector/combustor geometry on combustion-induced peak wall pressure and associated upstream influence, as well as on mixing/combustion characteristics at an entrance Mach number of 2.5. The length of the constant area section downstream of injection orifices had a strong influence on the above-mentioned characteristics. However, the sweep of the rearward-facing steps on both side walls had little effect on these characteristics, nor did reversing them have any effect. The peak wall pressure and the length of the upstream influence agreed qualitatively with predictions of an analytical model and an empirical formula developed at Johns Hopkins University. Fuel jets injected from the model with the longest constant area section and the fuel equivalence ratio of unity, coalesced at a very early stage downstream of the fuel injection orifices. This coalescence led to a decrease in mixing rate downstream, despite the higher degree of mixing near the injection orifices. The combustion efficiencies were higher than those obtained at NASA Langley in the upstream region due to the higher mixing rate near the injection orifices.