Lateral Jet Research Articles

Numerical simulation of non-conventional liquid fuels feeding in a bubbling fluidized bed combustor

The paper deals with the development of mathematical models for detailed simulation of lateral jet penetration into the fluidized bed (FB), primarily from the aspect of feeding of gaseous and liquid fuels into FB furnaces. For that purpose a series of comparisons has been performed between the results of in-house developed procedure- fluid-porous medium numerical simulation of gaseous jet penetration into the fluidized bed, Fluent?s two-fluid Euler-Euler FB simulation model, and experimental results (from the literature) of gaseous jet penetration into the 2D FB. The calculation results, using both models, and experimental data are in good agreement. The developed simulation procedures of jet penetration into the FB are applied to the analysis of the effects, which are registered during the experiments on a fluidized pilot furnace with feeding of liquid waste fuels into the bed, and brief description of the experiments is also presented in the paper. Registered effect suggests that the water in the fuel improved mixing of fuel and oxidizer in the FB furnace, by increasing jet penetration into the FB due to sudden evaporation of water at the entry into the furnace. In order to clarify this effect, numerical simulations of jet penetration into the FB with three-phase systems: gas (fuel, oxidizer, and water vapour), bed particles and water, have been carried out.

Concept of Non-Ablative Thermal Protection System for Hypersonic Vehicles

In order to reduce the shock-wave drag and aerodynamic heating of hypersonic vehicles effectively a new concept of non-ablative thermal protection system was proposed based on the idea of flowfield reconstruction. In this non-ablative thermal protection system a spike-blunt body structure and lateral jets are combined together to realize the flowfield modification. The spike transforms the bow shock into a conical shock, and the lateral jets increase the angle of conical shock wave and keep it away from the blunt body to avoid severe shock/shock interactions. Flow visualizations and pressure measurements were conducted in a hypersonic wind tunnel at Mach number 6 to demonstrate this concept. Numerical simulations were also carried out. Both experimental and numerical results demonstrate that the non-ablative thermal protection system works well for shock-wave drag reduction and thermal protection. The peak pressure at the reattachment region is reduced by 65% even under 4 deg attack angle by the lateral jet. Experimental data also show that the working pressure of lateral jets is much lower than that of forward-facing jets at the stagnation point. All the results show that the engineering application of non-ablative thermal protection system appears to be quite promising.

Range Prediction and Trajectory Correction of Long Range Rocket with Attitude Stabilization

The dispersion of long range rocket is significantly suppressed by the attitude stabilization in the boost phase. However, the attitude stabilization system cannot govern the propellant impulse error and mass error, which induces large dispersion in the longitudinal direction. Therefore, it is necessary to conduct range correction in the post-boost phase of flight trajectory. A range prediction method based on the elliptic ballistic theory is proposed in this paper. Elliptic ballistic equations and range estimation equations are derived and the modified range prediction method with correction factor is presented. It is verified that the proposed method can predict the residual flight range accurately. After that, the lateral pulse jets control is presented and utilized to correct the trajectory and eliminate the range error. A unique control law is reported that combines elliptic ballistic theory and control mode for lateral pulse jets. The impact point is directly controlled and rocket dispersion in the longitudinal direction is efficiently reduced.

THEFERMIBUBBLES. I. POSSIBLE EVIDENCE FOR RECENT AGN JET ACTIVITY IN THE GALAXY

The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 degrees (~ 10 kpc) above and below the Galactic center (GC) and are symmetric about the Galactic plane. Using axisymmetric hydrodynamic simulations with a self-consistent treatment of the dynamical cosmic ray (CR) - gas interaction, we show that the bubbles can be created with a recent active galactic nucleus (AGN) jet activity about 1 - 3 Myr ago, which was active for a duration of ~ 0.1 - 0.5 Myr. The bipolar jets were ejected into the Galactic halo along the rotation axis of the Galaxy. Near the GC, the jets must be moderately light with a typical density contrast 0.001 <~ \eta <~ 0.1 relative to the ambient hot gas. The jets are energetically dominated by kinetic energy, and over-pressured with either CR or thermal pressure which induces lateral jet expansion, creating fat CR bubbles as observed. The sharp edges of the bubbles imply that CR diffusion across the bubble surface is strongly suppressed. The jet activity induces a strong shock, which heats and compresses the ambient gas in the Galactic halo, potentially explaining the ROSAT X-ray shell features surrounding the bubbles. The Fermi bubbles provide plausible evidence for a recent powerful AGN jet activity in our Galaxy, shedding new insights into the origin of the halo CR population and the channel through which massive black holes in disk galaxies release feedback energy during their growth.

A PLIF and PIV study of liquid mixing enhanced by a lateral synthetic jet pair

In this paper, enhancement of mixing between two water streams of the same flow rate in a planar channel by means of a lateral synthetic jet pair is studied at a net flow Reynolds number of 83 using PLIF and PIV. The synthetic jet pair is operated 180° out-of-phase at a range of actuation frequencies and displacements, with the latter being characterized by the dimensionless stroke length. The extent of mixing is evaluated using PLIF data at a location further downstream in the mixing channel. It is found that at a fixed actuation frequency a higher dimensionless stroke length produces a better mixing, and as the actuation frequency increases a lower dimensionless stroke length is required to achieve a given mixing degree. At a sufficiently high frequency or dimensionless stroke length, a nearly homogenous mixing with a mixing degree greater than 0.9 can be obtained. A functional relationship between actuation frequency and dimensionless stroke length is also obtained by best fitting the experimental data, which can be used for selecting the synthetic jet operating conditions to ensure a good mixing. Furthermore, both PLIF and PIV results show that each synthetic jet actuation cycle produce two opposing vortex pairs, which play an important role in prompting mixing between the two fluid streams. The excellent mixing obtained at a high frequency or a high dimensionless stroke length is found to be largely caused by a strong interaction between these opposing vortex pairs.

Evaluation and Characterization of a Lateral Synthetic Jet Actuator

Evaluation and Characterization of a Lateral Synthetic Jet Actuator

Effects of Target Compliance on a High-Speed Droplet Impact

High speed spray cleaning which utilize droplets impact has been used for removing contaminants from wafer surface. When a droplet impacts a solid surface at high speed, the contact periphery expands very quickly and liquid compressibility plays an important role in the initial dynamics and the formation of lateral jets. Impact results in high pressures that can clean or damage the surface. In this study, we numerically investigated a high speed droplet impacts on a solid wall. In order to compare the available theory and experiments, 1D, 2D and axisymmetric solutions are obtained. The generated pressures, shock speeds, and the lateral jetting mechanism are investigated; especially the effect of target compliance is focused.

Design of Missile Autopilot with Aerodynamic Lift and Reaction Jets Based on Auto Disturbance Rejection Controller

First a new autopilot design model is presented for the interceptor missile with the blended aerodynamic lift and reaction jet. The reaction jet can improve the response speed, but the structure of control system becomes more complex. Therefore how to design control strategy properly is an urgent problem. Second, considering the discrete property of the lateral pulse jet thrusters and the continuous property of the aerodynamic fins, a kind of ADRC (active disturbance rejection control) autopilot system was designed for the aerodynamic lift/reaction jet missile. Finally, through a testing in the simulation of MATLAB, it is shown that, due to the sufficient utilization of the reaction jet, there is a significant improvement in the fast response and robust performance of the proposed controller. It is applicable to design the autopilot of aerodynamic lift and reaction jet blended missile.

Numerical Investigation of Lateral Jets over a Body of Revolution in Supersonic Cross-flow

DOI: 10.2514/1.B34171 In this paper, the flowfield induced by a sonic lateral jet in a supersonic crossflow of Mach number 3.3 around a bodyofrevolutionisnumericallystudied.Thenumericalsimulationis firstvalidatedforthecaseofacircularnozzle. Shock and vortical structures are examined and compared with those of jet in crossflow over a flat plate. It is found that horseshoe vortices are generated from the flow separation region before the jet orifice. They are shed laterally alongthefootprintofthejetbowshock,wrappingthebodyofrevolution.Thiswrappingeffectisabsentinthecaseof the crossflow over a flat plate. Effects of the jet nozzle shape on the flow structure are further investigated and analyzed. These nozzles, including circular, elliptical, dropletlike, and inverse dropletlike shapes, have equivalent cross-sectional area. The elliptical nozzle with its semimajor axis in the lateral direction has the largest force amplification factor and is thus the most effective. The detailed flow structures also indicate that the low-pressure regionaftofthejet isnot onlyclosely related withthesurfacetrailingvortices,butalsowiththe indentandreflection lines of the leeward barrel shock.

Numerical Investigation of Lateral Jets over a Body of Revolution in Supersonic Cross-flow

Numerical Investigation of Lateral Jets over a Body of Revolution in Supersonic Cross-flow

A Numerical Simulation on Characteristics of Annular Helical Flow in Horizontal Wellbore Cleanout

Trajectories of directional jets and characteristics of annular helical flow in horizontal wellbore cleanout were investigated by the computational fluid dynamics method. For an annular helical flow, the drive source is the partial lateral jets, while the forward and backward jets provide the fluid source. The axial and radial distributions of annular and tangential velocity were analyzed comprehensively. As the distance increases and the flow rate decreases, the strength of the helical flow weakens dramatically. As the rotating speed of the jetter increases, the helical strength enhances slightly. The best performance to achieve annular helical flow is water, followed by Guar-B and Guar-A. This article is beneficial to study the solid transportation in helical flow and optimize the operation parameters.

Heat transfer and pressure drop in a reciprocating blind duct with swirls generated by a lateral entry jet

This experimental study simulates the advanced piston cooling passage of a marine propulsive diesel engine to examine the heat transfer performance of a reciprocating square blind duct with swirl induced by injecting a lateral jet. The detailed Nusselt number ( Nu) distributions over two opposite walls, namely the jet wall and the back wall, of the reciprocating blind duct at channel (jet) Reynolds numbers Re( Re j ) of 1500 (6000), 2000 (8000), 3000 (12,000), 5000 (20,000), 7000 (28,000) and 10,000 (40,000) with reciprocating frequencies of 0, 0.67, 0.83, 1 and 1.17 Hz are measured using the steady-state infrared thermo-graphic method. The jet flows and the jet-induced swirl, which improve heat transfer performance considerably, interact with the reciprocating and buoyancy forces to exhibit synergistic impacts on Nu distributions. This is demonstrated by comparatively examining a set of full-field Nu distributions to illustrate the Nu variations responding to the changes of Re j , pulsating ( Pu) and reciprocating Grashof ( Gr p ) numbers. The individual and interdependent channel Reynolds number ( Re), Pu and Gr p effects on the area-averaged Nusselt number ( Nu ¯ ) are parametrically analyzed to devise Nu ¯ correlations. A comparison with reported Nu ¯ data for the various reciprocating channels indicates the favorable heat transfer performance for the present jet-swirl system. Due to the combined Re, Pu and Gr p effects, the Nu ¯ over the jet wall and back wall are respectively raised to 0.78–1.3 and 0.8–1.51 times of the static heat transfer levels. Nevertheless, the high pressure potentials required to facilitate the lateral jet and to overcome the viscous frictions and the pressure drop through the enlargement of flow passage are observed, leading to significant increases of the pressure drop coefficient ( f) from the static smooth pipe flow reference ( f ∞). The thermal performance factors ( η) defined on the basis of constant pumping power consumption for such flow configuration relative to the smooth pipe flow condition and the static jet-swirl condition are evaluated.

Comparative study of turbulent heat transfer in smooth and scale-rib roughened reciprocating blind ducts with laterally tangent entry jet

This experimental study investigated the performances of heat transfer enhancement (HTE), pressured drop coefficient ( C f ) and relative thermal performance factor ( η th) generated by a lateral entry jet for two reciprocating square blind ducts with smooth and scale-rib roughened walls for piston cooling applications. At each test reciprocating frequency ( f) in the range of 0–2 Hz, the lateral and longitudinal Nusselt number ( Nu) distributions over two opposite duct walls, namely the jet wall and the back wall, are measured at duct (jet) Reynolds numbers Re( Re j ) of 5000(31,850), 10,000(63,690), 15,000(95,540) and 20,000(127,400). The jet-induced flow phenomena in each blind duct interact with the reciprocating and buoyancy forces to exhibit synergistic impacts on HTE performances. This is demonstrated by examining the Nu variations over the reciprocating jet and back walls in response to the changes of Re, pulsating ( Pu) and reciprocating Grashof ( Gr p ) numbers for each blind duct. The individual and interdependent Re, Pu and Gr p effects on heat transfer are comparatively examined to reveal the influences of the scale-rib roughness on HTE performances. Within the parametric conditions tested, the ratios of the averaged Nusselt number ( N u ¯ ) between those measured from the reciprocating and static jet and back walls fall respectively in the ranges of 0.68–0.9 and 0.69–0.89 for the smooth blind duct; and 0.63–0.97 and 0.62–0.99 for the roughened blind duct. Due to the presence of the scale-rib roughness, the ( N u ¯ ) over the roughened reciprocating jet and back walls are respectively raised to 1.04–1.4 and 1.01–1.14 times of the smooth-walled references; while the pressure drop coefficients are raised to about 2–4.2 times of the smooth-walled duct levels. Two sets of N u ¯ correlations over the jet and back walls for the reciprocating blind ducts with smooth and scale-rib roughened walls are generated. Justified by the relative thermal performance factor results, the present wall roughness in the reciprocating blind duct with a lateral entry jet can provide both improvements in HTE effectiveness and the thermal efficiency at Re = 20000.

Solid Launcher Dynamical Analysis and Autopilot Design

The dynamics of a small solid launch vehicle has been investigated. This launcher consists of a liquid upper stage and three fundamental solid rocket boosters aligned in series. During the ascent flight phase, lateral jets and grid fins are adopted by the flight control system to stable the attitude of the launcher. The launcher is a slender and aerodynamically unstable vehicle with sloshing tanks. A complete set of six-degrees-of-freedom dynamic models of the launcher, incorporation its rigid body, aerodynamics, gravity, sloshing, mass change, actuator, and elastic body, is developed. Dynamic analysis results of the structural modes and the bifurcation locus are calculated on the basis of the presented models. This complete set of dynamic models is used in flight control system design. A methodology for employing numerical optimization to develop the attitude filters is presented. The design objectives include attitude tracking accuracy and robust stability with respect to rigid body dynamics, propellant slosh, and flex. Later a control approach is presented for flight control system of the launcher using both State Dependent Riccati Equation (SDRE) method and Fast Output Sampling (FOS) technique. The dynamics and kinematics for attitude stable problem are of typical nonlinear character. SDRE technique has been well applied to this kind of highly nonlinear control problems. But in practice the system states needed in the SDRE method are sometimes difficult to obtain. FOS method, which makes use of only the output samples, is combined with SDRE to accommodate the incomplete system state information. Thus, the control approach is more practical and easy to implement. The resulting autopilot can provide stable control systems for the vehicle.

Substitution of Hot-Gas Lateral Jets by Cold-Gas Jets in Supersonic Flows

C = wave celerity similarity number Cf = friction coefficient Cp = pressure coefficient Cp diff = differential pressure coefficient D = diameter of the body, m J = momentum flux similarity number JR = momentum flux ratio M = mass flux similarity number Mth = thruster ejection Mach number M1 = freestream Mach number NCR = nozzle celerity ratio NJR = nozzle momentum flux ratio NMR = nozzle mass flux ratio NPR = nozzle pressure ratio NrTR = nozzle temperature ratio P = pressure similarity number PR = total pressure ratio Pj = nozzle exit static pressure, Pa Po, P1 = freestream static pressure, Pa Pt = total pressure, Pa Pti = thruster stagnation pressure, Pa ReD = diameter-based Reynolds number rth = specific thruster gas constant, J kg 1 K 1 r1 = specific freestream gas constant, J kg 1 K 1 T = temperature similarity number Tj = nozzle exit static temperature, K Tt = total temperature, K Tti = thruster stagnation temperature, K T1 = freestream static temperature, K U = velocity component along the x axis, m s 1 Uo, U1 = freestream velocity component along the x axis, m s 1 uf = friction velocity component along the x axis, m s 1 W = velocity component along the mean ejection direction, m s 1 Wj = nozzle exit velocity component along the mean ejection direction, m s 1 x = horizontal coordinate along the body axis, m y = horizontal coordinate perpendicular to the body axis, m y = dimensionless wall distance z = vertical coordinate, m th = thruster gas isentropic coefficient 1 = freestream gas isentropic coefficient = kinematic viscosity, m s 1 = density, kg m 3 j = nozzle exit density, kg m 3 1 = freestream density, kg m 3 w = wall shear, Pa

CFD Analysis of the Aerodynamic Interaction Effects Due to Lateral Jet Injection in to Hypersonic Flow

Reentry vehicle often uses reaction control system for providing necessary critical forces during reentry. The effect of lateral jet due to reaction control system on aerodynamic characteristics especially stability aspect of a reentry vehicle has been investigated .CFD analysis of the interaction of a lateral jet on Leeward side has been investigated on a reentry body with a circular sonic air jet injected normally in to hypersonic flow from the body surface. A systematic numerical analysis for a lateral jet interaction was performed at angles of attack 0, 2, 5, 8, and 10 degrees at free stream Mach number 8.1. The methodology has also be verified by comparing the pressure distribution at an angle of attack of 20 degrees with experimental data. The effect of lateral jet on aerodynamic characteristic has been studied by comparing the variation of aerodynamic characteristic along the length with and without lateral jet. The aerodynamic coefficients variation of aerodynamic characteristics along the axial l...

Flow field characterization of coaxial conical and serrated (chevron) nozzles

PIV measurements were performed to provide insight into the effect of serrated (chevron) nozzles on the flow field of a coaxial circular jet. The serrations were tested on the primary nozzle. Mean flow results showed that the chevron effectively redistributes momentum from the high velocity center stream outward to the lower velocity secondary stream by creating lateral jets. This leads to a more rapid decay of the peak jet velocity and a consequent reduction in the length of the jet potential core. Local increases of up to 65% in the outer stream velocity were measured. The interaction of the secondary jets with the lower velocity outer stream produces increases in turbulent kinetic energy (TKE) near the center nozzle lip. These flow field effects correlate with the jet’s acoustic emissions: Reduction of low-frequency noise due to large scale mixing and potential core shortening, and increased high-frequency noise due to increased near-field turbulence.

Numerical simulation of transverse side jet interaction with supersonic free stream

The interference effects of side jets with supersonic cross flow for a lateral jet controlled missile are simulated numerically. Three-dimensional Navier–Stokes equations along with Menter's SST turbulence model are solved using a commercial CFD software. Effect of angle of attack, ratios of free stream and jet pressure, number of jets, etc. have been systematically studied. A very good agreement between computed and experimental surface pressure has been obtained. From detailed flow field analysis it is observed that the generation of pitching moment is taking place due to low pressure region behind the jet nozzle and the normal force and pitching moment is seen to vary linearly with the jet pressure ratio.

Predictive Guidance of a Projectile for Hit-to-Kill Interception

In this paper, a predictive guidance algorithm is developed for a spin-stabilized hit-to-kill guided projectile. The projectile is used as an interceptor against rockets, mortar, and artillery. Guidance is based on a new rapid trajectory prediction algorithm for projectiles fired at high quadrant elevations. The interceptor uses lateral pulse jets located near the mass center for control. High spin rates require additional guidance compensation for gyroscopic effects when compared to a fin-stabilized projectile. The probability of kill (PK) is evaluated based on typical gun pointing errors, roll angle uncertainty, and target acquisition errors. It is shown that guided interceptors can achieve a 90% PK by using as few as 5 projectiles in the presence of roll, gun pointing, and target errors. It is also shown that, despite sensitivity to errors in gun pointing and target errors, the predictive guidance system is able to achieve an acceptable PK. For a spin-stabilized interceptor, estimated-roll orientation errors may become large. Simulations are performed for errors in the estimated roll, and it is demonstrated that roll does not need to be precisely known for a successful interception.

Numerical model of gaseous fuel jet injection into a fluidized furnace

The paper presents a fluid-porous medium model, developed for stationary 2D predictions of fluidized bed. Dense phase is considered a fixed porous medium, while gas–particle interactions and bubbling phase are modeled regarding balance of friction forces between gas and particles. Like referent measurements, predictions of lateral jet injection into the bed suggest the jet penetration length is strongly affected by fluid velocity at the nozzle outlet, while influences of the nozzle vertical position and inclination angle are not significant. Also, the fluid velocity and the nozzle vertical position exert pronounced effects on mixing rate of components (fuel and oxidizer).