Jet Expansion Angle Research Articles

Experimental study on spray characteristics of RP-3 kerosene under the near critical condition with different injection conditions

In an aero-engine, the effect of oil-gas mixing directly affects the working condition of the combustion chamber, and the mixing process of RP-3 kerosene near the near-critical point is more complicated because its physical properties are more strongly affected by its own temperature and pressure changes. The injection process of RP-3 kerosene near the near-critical point was photographed under different injection conditions using high-speed ripple shadowing technology. It was found that the increase in air injection pressure and the distance from the nozzle outlet to the cyclone outlet would reduce the jet expansion angle and jet width. The former would reduce the jet’s self-excited oscillation frequency, and the latter would increase it.

Effect of nozzle inclination angle on characteristics of a gas jet in a gas-solid fluidized bed

Changing the incident angle of the nozzle could make the characteristics of the jet such as jet expansion angle (θ), jet width (b), and jet penetration depth (L) change drastically. Experiments were carried out to investigate the effect of nozzle inclination on the jet characteristics in a two-dimensional (2D) fluidized bed of three different particles. The summation method and statistical method are used to extract the θ, bmax, and L from the video data. There is a trend that the penetration of the jet increases with α from −60° to 60°. As the particle diameter and the particle density increase, L and bmax decrease. Considering the variation of force on supported particles at the jet boundary when α ≠ 0°, a penetration model for the inclined jets is proposed. The error between the model prediction value and the experimental value of the L is in the range of −15% ~ 20%.

Spraying Liquid Using Pneumatic Nozzle for Suspension Fuel

Characteristics of gas-droplet flow created by spraying a liquid using an advanced pneumatic nozzle for suspension fuel were studied experimentally. The measurements were made using the shadow photography method. On the example of water, the disperse composition of the gas-droplet flow, jet expansion angle, and flow structure stability were determined for different regimes. It was shown that most droplets were less than 10 $$\mu$$ m in size. The disperse composition of the flow remained unchanged for a wide range of operating parameters. The nozzle designed generates droplets of a size sufficient for efficient combustion of suspension fuel under real conditions.

Experimental investigation of the expansion characteristics of vaporized kerosene jets in a quiescent atmospheric environment

In this paper, the time-averaged and instantaneous information of the vaporized kerosene jet injection into a quiescent atmospheric environment, including the expansion angle, deflection angle and shock wave structure, were acquired by natural light and a schlieren system. The results show that the jet expansion angle increases first and then decreases during the kerosene vaporization, which is mainly governed by the pressure change inside the shear layer and the variation in the jet axial speed. Compared with straight injection, the oblique scheme inhibits the jet expansion process and enhances the expansion property in the vertical and parallel directions of the bevel face. Because of the asymmetric configuration of the injector exit and the adsorptive effect of the bevel face, the jet plume in the oblique injection scheme obviously deflects along the axial direction. In addition, the expansion angle fluctuates when the vaporized kerosene is injected into some specific conditions. The frequency of the jet pulse is approximately 2.1 Hz, and the pulsation mode gradually converts during the vaporization process. The two-phase flow instability occurring in upstream heated kerosene might be responsible for this unique phenomenon.

Characteristics of two-dimensional counter-flowing wall jets

Wastewater plant effluents discharged into streams are expected to undergo dilution in a short reach. Jets provide rapid mixing and enhance dilution of the effluent discharged into the stream. The counter-flowing wall jet expansion angle, the geometry of the dividing streamline and the jet penetration length were found using the measured mean axial jet velocity data. These jet characteristics were expressed in terms of the jet velocity ratio (jet exit velocity against main stream velocity). A salt solution of known concentration was injected into the jet flow. The distribution of the salt concentration was determined at several cross-sections of the jet wake using a concentration meter. The standard deviation of the salt concentration provided a measure of jet mixing. When standard deviation reached zero at a cross-section, mixing was considered to be complete.

Experimental Investigations of the Flow Field Structure and Interactions between Sectors of a Double-Swirl Low-Emission Combustor

In this paper, the flow field characteristics of a double-swirl low-emission combustor were analyzed by using Particle Imaging Velocimetry (PIV) technology in an optical three-sector combustor test rig. The interactions between sectors and the flow field structure were explained. The results illustrated that there was a big difference between the flow field structures of the middle sector and the side sector under the same pressure drop, which was mainly induced by the interactions between sectors. The interactions made the swirl intensity of the middle sector weaker than that of the side sector, which made the recirculation zone of the middle sector be smaller than that of the side sector. With the increase of swirler pressure drop, the jet velocity at the exit of the swirler, the jet expansion angle, the width of the recirculation zone and the recirculating speed of the central axis became larger, enhancing the interactions between air streams from middle sector and side sector. The flow velocity in the central plane between sectors was small, especially the radial velocity, mainly because of the loss of the swirl intensity by the interactions between flow field of adjacent sectors. The expansion angle determined the position of the vortex in the primary recirculation zone; the axial and radial position of the vortex move downstream and radial outward with the increase of the jet expansion angle. The results of the mechanism of flow field organization in this study can be used to support the design of new low-emission combustor.

Experimental study on the diffusive flame stabilization mechanism of plasma injector driven by AC dielectric barrier discharge

A plasma injector element was designed to experimentally study the mechanism of methane-air diffusive flame stabilized by a discharge plasma. The air plasma was generated within the annulus gap of the injector by alternating current dielectric barrier discharge. The discharge voltage, current and photographs were recorded first. Three internal effects of the plasma on combustion were later investigated separately through several diagnostic methods, including optical emission spectrometry (OES), infrared thermography, thermocouple, infrared thermometer, schlieren imaging, photos and CH* chemiluminescence. Finally, the return on investment (ROI) was calculated. The results showed that a large number of filamentary micro discharge paths occur within the discharge gap. These discharge paths rotate anticlockwise at high speed and act as a virtual ‘fan’ to induce the flow jet. The velocity of the induced jet increases with increasing discharge voltage. The original jet expansion angle is enlarged by the radial velocity component of the induced jet, resulting in the mixing enhancement of the air and methane. The plasma rotational temperature (the first negative system ) obtained from OES is close to the discharge gas temperature measured by infrared thermography, indicating that the discharge gas temperature can be approximately represented by the rotational temperature. According to the measured temperature of the injector and the jet, the impact of the thermal effect of the plasma on flame stabilization is negligible. Due to the plasma, the height of the flame center and its representative length are generally reduced as the voltage rises, and the methane-air mixture becomes ignitable, and a stable flame can be reached under the conditions in which direct ignition fails. The combustion is enhanced with increasing heat release rate of the flame by the plasma. This finding revealed that the ROI of plasma-assisted flame stabilization is lower under a higher flowrate and a larger equivalence ratio for unstable flame situations.

Injection characteristics of near critical and supercritical kerosene into quiescent atmospheric environment

The injection of RP-3 aviation kerosene at near and above critical conditions into a quiescent atmospheric environment is experimentally investigated with special emphasis on the effects of injection temperature and pressure on the jet characteristics of shock structure and phase transition. Visualization of the near-field shock/jet structure is performed using Schlieren imaging. Results show that fuel condensation occurs when supercritical RP-3 is injected at near critical temperature. At the supercritical injection conditions investigated, ideal-gas-like expansion and internal shock structures are observed. A RP-3 surrogate is used to determine the thermodynamic phase diagram to reveal the phase transition during the injection processes. The characteristics of the Mach disk are further presented and discussed. It is found that the location and size of the Mach disk as well as jet expansion angle increase with increasing injection pressure. Furthermore, specific heat ratios and compressibility factors of RP-3 surrogate and N2 are evaluated to analyze their differences in Mach disk diameter and jet expansion angle; it is shown that the compressibility factor is the primary factor that deviates the jet structure of RP-3 from that of ideal-gas N2.

Numerical simulation of the influence of environmental and jet parameters on supercritical injection

The establishment of fuel injection model and the research of supercritical injection characteristics are crucial to supercritical state fuel injection technology. We established a numerical model of supercritical fuel injection based on the analysis of supercritical aviation fuel injection. The model was modified and validated by existing experimental data. Subsequently, the model was used to simulate supercritical fuel injection into the supercritical environment. The effects of environmental conditions and injection temperature on the jet length and the expansion angle were studied. The following observations were made: (1) Changes in the supercritical fuel jet length and expansion angle decreased with increasing environmental pressure. (2) As the environmental temperature increased, the supercritical fuel jet length and expansion angle did not obviously change. (3) With the increasing jet temperature, the supercritical jet length increased with the increasing jet temperature, but the jet expansion angle did not show obvious changes. In summary, supercritical fuel injection is significantly affected by environmental pressure.

Heterogeneous mechanisms governing formation of droplets in atomizing superheated liquid by a spray atomizer

The effects of increasing the jet expansion angle, decreasing droplet sizes, and forming a bimodal spectrum of droplets in atomizing superheated liquid by a spray atomizer are discussed. Condensation is adopted to be the mechanism governing the formation of a smaller-size fraction, and atomization enhanced by superheating is adopted to be the mechanism governing the formation of a larger-size fraction. Formulas for calculating the droplet diameter and the jet expansion angle are obtained. It is demonstrated that the calculated and experimentally determined droplet sizes are in satisfactory agreement with each other.

Computational Fluid Dynamics (CFD) Investigation of Submerged Combustion Behavior in a Tuyere Blown Slag-fuming Furnace

A thin-slice computational fluid dynamics (CFD) model of a conventional tuyere blown slag-fuming furnace has been developed in Eulerian multiphase flow approach by employing a three-dimensional (3-D) hybrid unstructured orthographic grid system. The model considers a thin slice of the conventional tuyere blown slag-fuming furnace to investigate details of fluid flow, submerged coal combustion dynamics, coal use behavior, jet penetration behavior, bath interaction conditions, and generation of turbulence in the bath. The model was developed by coupling the CFD with the kinetics equations developed by Richards et al. for a zinc-fuming furnace. The model integrates submerged coal combustion at the tuyere tip and chemical reactions with the heat, mass, and momentum interfacial interaction between the phases present in the system. A commercial CFD package AVL Fire 2009.2 (AVL, Graz, Austria) coupled with several user-defined subroutines in FORTRAN programming language were used to develop the model. The model predicted the velocity, temperature field of the molten slag bath, generated turbulence and vortex, and coal use behavior from the slag bath. The tuyere jet penetration length (l P) was compared with the equation provided by Hoefele and Brimacombe from isothermal experimental work $$ \left( {\frac{{l_{\text{P}} }}{{d_{o} }} = 10.7\left( {N^{\prime }_{Fr} } \right)^{0.46} \left( {\rho_{\text{g}} /\rho_{l} } \right)^{0.35} } \right) $$ and found 2.26 times higher, which can be attributed to coal combustion and gas expansion at a high temperature. The jet expansion angle measured for the slag system studied is 85 deg for the specific inlet conditions during the simulation time studied. The highest coal penetration distance was found to be l/L = 0.2, where l is the distance from the tuyere tip along the center line and L is the total length (2.44 m) of the modeled furnace. The model also predicted that 10 pct of the injected coal bypasses the tuyere gas stream uncombusted and carried to the free surface by the tuyere gas stream, which contributes to zinc oxide reduction near the free surface.

Unimpeded Air Velocity Profiles of an Air-Assisted Five-Port Sprayer

A capability that relies on tree structure information to control the flow rates of liquid and air is the preferential design in the development of variable-rate orchard and nursery sprayers. Unimpeded air jet velocities from an air-assisted, five-port sprayer in an open field were measured at four heights above ground, seven distances up to 3 m from the sprayer outlets, and five sprayer travel speeds from 0 to 8.0 km h-1. Air jet velocities were adjusted by changing the sprayer fan inlet diameter. Calculations of the air jet initial region length, transition length, and expansion angle from the five-port nozzles were computed with an air jet distribution model. The intersection between adjacent air jets from the five-port nozzles was determined from the air jet expansion angle. Air velocities were measured with a constant-temperature anemometer system coupled with hot-wire sensors. The air jets expanded at a 50 angle and intersected with adjacent air jets at 0.027 m from the five-port nozzles. When the sprayer was stationary (0 km h-1), axial air velocities from the nozzle outlets increased as fan inlet diameter increased and decreased as a hyperbolic function as the distance increased. Variations in the peak air velocities and airflow pressures with travel speeds of 3.2 to 8.0 km h-1 and heights of 0.2 to 2.0 m were statistically insignificant. When the sprayer was in motion and due to air entrainment and air jet disturbance, the peak air velocities decreased and airflow pressures increased as distance from the nozzle outlets increased. For all parameters tested, the peak air velocities and airflow pressure increased as fan inlet diameter increased, demonstrating that changing the fan inlet diameter achieved variable airflow rates with uniform air profiles.

Entrained droplets in underexpanded gas jet in water

A visualization study was performed to investigate the flow of an underexpanded nitrogen gas jet injected into water. The stagnation pressure was varied in the range 0.5–8.0 MPa. The gas jet length and expansion angle were obtained from time-averaged images captured using a high-speed camera. The gas jet length and expansion angle increased approximately linearly with increasing stagnation pressure. The entrainment velocity and the velocity of entrained water droplets in the gas jet were obtained by particle image velocimetry.

Study of horizontal sonic gas jets in gas–solid fluidized beds

AbstractExisting jet penetration correlations have all been developed for sub‐sonic gas jets and have been found to perform poorly when employed in sonic and supersonic regimes. In the present study, triboelectric probes were used to measure both the penetration depth and expansion angle of sonic gas jets. Experiments were conducted using nozzles of different size and geometry, different particle types, different injection gases, and different fluidization velocities. All these data were used to develop a new, general correlation to predict the penetration depth of sonic gas jets. The effects of these variables on jet expansion angle were also studied.

Visualization of the Effect of a Shroud on Entrainment of Fluidized Solids into a Gas Jet

Submerged gas jets issuing into fluidized beds are used in many different industries and it is important to have a fundamental understanding of how the gas and surrounding medium interact – to understand the flow patterns and how the solids behave in the vicinity of the nozzle jet. Following the discussions of Bohnet and Teifke (1985) and Idelchek (1994) it was decided to qualitatively investigate the effects of altering the region surrounding the contact between the jet and the fluidized bed. Alteration of the flow pattern was accomplished using a semi-cylindrical shroud (0.035 m i.d. and 0.043 m long) that formed a physical barrier around the nozzle tip. The nozzle inner diameter was 0.0016 m i.d. and the motive gas flow rate was supersonic. Videos were recorded of the solids and gas flow patterns via a special transparent plate on the wall of the fluidized bed for a half-jet with and without a shroud at a superficial fluidization gas velocity of 0.11 m/s. Presented below are the original videos and observations derived from the two simple experiments in a fluidized bed with a rectangular cross-section (0.10 by 1.20 m and 2.0 m high). There was a significant difference in the flow patterns of the solids in the vicinity of the nozzle tip when the shroud was present. Furthermore, the jet expansion angle and penetration were observed to decrease by approximately 50% and 43%, respectively.

STRUCTURES AND PHASE TRANSITION PROCESSES OF SUPERCRITICAL METHANE/ETHYLENE MIXTURES INJECTED INTO A SUBCRITICAL ENVIRONMENT

ABSTRACT The structure and phase transition of supercritical methane/ethylene mixtures injected into quiescent subcritical nitrogen were investigated in this study. Visualization of the near-field jets and flow structure inside the injector, as well as measurement of shock/jet structures, were performed using shadowgraph images. It was found that supercritical methane/ethylene jets injected away from the critical point undergo ideal–gas-like expansion and exhibit visible internal shock structures. Opaque jets with condensation occurring at the injection plane or even inside the injector were observed when the supercritical mixture was injected near the critical point. The pressure profile along the injector axis for the condensed jet indicates that a pressure rise inside the injector comes from the release of latent heat during homogeneous nucleation processes and is the primary factor in the production of a large jet expansion angle in the condensed jet. The fluid along streamlines passing through the Mach disk is less likely to condense, due to the short residence time within the nongaseous region and substantial increases in pressure and temperature downstream of the Mach disk.

Digital X-ray Imaging Technique to Study the Horizontal Injection of Gas-Liquid Jets into Fluidized Beds

Gas-liquid jets injected into fluidized beds of particles/catalyst find applications in many industrial processes. The effective distribution and mixing of the feed droplets with the entrained bed particles is vital in improving the process efficiency. The present study utilizes a sophisticated digital X-ray imaging system to study the internal flow structure of jets injected into fluidized beds. The system is equipped with an X-ray image intensifier (XRII) and optical detectors, which convert the transmitted X-ray photons into digital images of up to 60 frames s-1. The imaging technique provides useful information such as the jet expansion angle and the penetration distance. These are functional quantities in optimizing the performance of feed nozzles, and in modeling the jet-fluidized bed interactions.In this work, the horizontal injection of gas, gas-liquid, and liquid jets into fluidized beds is investigated. The results indicate that the jet expansion (half-angle) is considerably reduced for a gas-liquid jet (5-7 degrees) when compared to that of a gas jet (10-15 degrees). The gas-liquid jet also appears to penetrate more than a gas jet with the same momentum. When a liquid feed is introduced into a fluidized bed of particles, the particles may agglomerate if they are wet-enough to form liquid bridges. Improper feed distribution may be a direct contributor to enhanced agglomeration. In this regard, radio-opaque tracers mixed with the feed liquid are injected to track the formation and the movement of agglomerates. The tracer experiments show that the agglomerates are generated at the end of the jet region, close to its maximum penetration distance. A brief discussion on the modifications required to achieve improved contrast for the acquired images, and the effect of some important X-ray parameters are also included in the present study.

232 高分子溶液ジェットと自由液面の相互作用の可視化

Turbulence modification by polymer solution (Toms effect) had contributed to various flow systems such as pipe flows, including two-phase flow systems. However there are few studies on the Toms effect at the gas liquid interface, e.g., free surface. The turbulence modification on the free surface is highly related to the free surface turbulence. In this study, Toms effect at a free surface was experimentally investigated. The test section was a rectangular tank having a free surface. A circular nozzle was set horizontally beneath the free surface to form a jet. The jet interacted with the free surface, causing the wavy free surface condition. In previous studies, free surface with polymer additives are known to be much calm. This should be the consequence of turbulence under the free surface. PIV technique was applied to evaluate the flow field under the free surface. Instantaneous velocity distribution was obtained. Water jet expanded wide, while the Polymer jet had less jet expansion angle. Polymer additives reduced entrainment of the jet. The modification at the free surface was a consequence of Toms effect by polymer additives at the turbulent jet.

Supersonic Jets with Periodic Structure due to Arc plasma Expansion into a Low pressure ambient

AbstractA supersonic plasma jet was produced by a d.c. arc plasma generator operated at normal pressure and connected to a low‐pressure (p∞ = 0.2‐50 kPa) chamber via cylindrical nozzle with diameter of 2.5 mm. The argon gas flow rate was G = 0.025 to 0.35 g.s−1. In some experiments current IE ≦ 30 A passed coaxially through the initial part of the jet. Photographic records of the jet and pressure measurements are in agreement with theoretical predictions by a simple one‐dimensional, gasdynamical model capable of self‐consistent calculations throughout the plasma source/jet system. Periodic jet structure is observed over a wide range of experimental conditions, incl. in highly under‐expanded flow. The jet expansion angle and Mach disc position vary with p∞, G and IE, but are nearly constant at different arcing currents.

A fast fluidized bed reactor for industrial FCC regenerator

A mathematical model for catalyst regenerator of fluidized bed catalytic cracking process, including thermal effects, has been developed to simulate a regenerator having characteristics similar to that of the unit operated by Petrobras (Brazilian Oil Company). The proposed model was built up by splitting the regenerator into two regions: the first one was the jet region near the air distributor grid, the second one was the dense phase region (divided into bubbles and gas-solid emulsion phases). The jet region was described taking into account experimental observations related to the dead zones between adjacent jets, jet expansion angle, gas and solids entrance effects as well as coalescence of neighboring jets. It was assumed heterogeneous carbon, hydrogen and carbon monoxide combustion on the catalyst, as well as the homogeneous carbon monoxide oxidation in the gas phase. The model equations are solved numerically, allowing the physical properties of the system and compounds concentration in emulsion and diluted phases to vary with bed height so that more realistic predictions are obtained.