Angled Injection Research Articles

Effect of strut profile, angled injection, and blunting of leading edge on mixing of supersonic hydrogen-air streams

Mixing fuel and air in a scramjet combustor is one of the key challenges in its development due to the short residence time available. Strut based injection is considered a viable alternative and is widely investigated. In the present work, the effect of the strut profile, angled injection of fuel, and the blunting of the leading edge of the strut on the mixing of fuel and air is studied using the Finite Volume Method (FVM). The base case chosen is an experiment with Hydrogen fuel injection from a strut at Mach 2.3 in a supersonic air stream of Mach 2. The popular strut profiles of diamond and wedge shapes are considered. The mixing due to wedge strut with dual injection from the trailing face and the effect of the inclination angle of the two fuels is studied. It is observed that the wedge strut with single fuel injection results in the highest mixing efficiency. Compared to the diamond strut, the distance to reach the complete mixing of fuel and air is reduced by 100 mm for the wedge strut with single injection. The high thermal load on the leading edge of the strut requires blunting (and rounding) for heat removal, and its effect is also investigated. The blunting of the leading edge of the strut leads to a decrease in mixing efficiency and an increase in total pressure loss as well as rise in entropy compared to a strut with pointed leading edge. Blunted wedge strut with single injection requires 40 mm more length for complete mixing than wedge strut with pointed leading edge. Also, after blunting, its rounding increases the mixing efficiency slightly but reduces the total pressure loss and entropy rise noticeably.

Large eddy simulation of compound angle film cooling with vortex generators

Film cooling is a commonly used approach in high-performance gas turbine engines to insulate the components from the hot mainstream flow. Compound angle injection with orientation oblique to the freestream laterally are employed to achieve wide coolant coverage. The passive control devices of delta winglets are effective in improving thermal performance. In the current study of film cooling by LES, the compound angles are investigated with 35° vertical inclined angle to the cooling wall and 0 deg, 30 deg, and 60 deg lateral inclined angles to the streamwise crossflow. Vortex generators of delta winglets pair are installed upstream of the cooling hole. Adiabatic film cooling effectiveness is examined at the blowing ratio of 1.0 and density ratio of 2.0. The cooling performance improves significantly when the compound angled injection and delta winglets are applied. Mean and instantaneous vortical structures in the near-hole field are presented. The counter-rotating vortex pair (CRVP) associated with streamwise injection changes into a strong symmetric vortex in compound angled cases. Anticounter-rotating vortex pair (anti-CRVP) evolved from delta winglets cancels the strength of CRVP in the streamwise coolant injection case, and the downwash effect of anti-CRVP is weakened with lateral angle increasing.

Effects of fuel injection angle on mixing performance of scramjet pylon-cavity flameholder

A numerical investigation on the effects of fuel injection angle on various mixing parameters within a pylon-cavity aided supersonic combustor flameholder under non-reactive flow conditions is performed. The computational model based on Reynolds-averaged Navier–Stokes equations for compressed real gas is solved by a coupled, implicit, second-order upwind solver with a two-equation Menter’s shear stress transport turbulence model. The steady simulations are experimentally validated using wall pressure data, two-dimensional (2D) velocity field, and fuel mass fraction. Three distinct fuel injection locations at the cavity floor are used for sonic hydrogen fuel injection at 90° and 45° injection angles, with a crossflow Mach number of 2.2. The results show deeper fuel jet penetration capability for the transverse injection when compared to an angled injection, whereas better mixing capability is observed for the latter. The fuel jet vortex pairs formed due to the interaction of the surrounding cavity flow with the barrel shock play a vital role in the mixing mechanisms. The lower pressure regions due to the barrel shock result in the formation of a secondary fuel jet vortex pair. The Kelvin–Helmholtz instability observed between the counter-rotating vortex pairs results in the formation of smaller eddies, which enhance the fuel dispersion and transport.

The Effect of Fuel Injection Location on Supersonic Hydrogen Combustion in a Cavity-Based Model Scramjet Combustor

Supersonic combustion experiments were performed using three different hydrogen fuel-injection configurations in a cavity-based model scramjet combustor with various global fuel–air equivalence ratios. The configurations tested were angled injection at 15° to the flow direction upstream of the cavity, parallel injection from the front step, and upstream injection from the rear ramp. Planar laser-induced fluorescence of the hydroxyl radical and time-resolved pressure measurements were used to investigate the flow characteristics. Angled injection generated a weak bow shock in front of the injector and recirculation zone to maintain the combustion as the equivalence ratio increased. Parallel and upstream injections both showed similar flame structure over the cavity at low equivalence ratio. Upstream injection enhanced the fuel diffusion and enabled ignition with a shorter delay length than with parallel injection. The presence of a flame near the cavity was determined while varying the fuel injection location, the equivalence ratio, and total enthalpy of the air flow. The flame characteristics agreed with the correlation plot for the stable flame limit of non-premixed conditions. The pressure increase in the cavity for reacting flow compared to non-reacting flow was almost identical for all three configurations. More than 300 mm downstream of the duct entrance, averaged pressure ratios at low global equivalence ratio were similar for all three injection configurations.

Liquid jet breakup behind a pylon in supersonic flow

The thin pylon has been found to be one of the most promising hypermixers, offering enhanced mixing of fuel with minimum pressure loss. In the present study, the effect of pylon height and the angled injection on the liquid jet breakup and its effect on atomization in a free stream of Mach 1.71 has been studied experimentally. Acetone is used as the liquid medium to characterize the liquid jet injection in supersonic flow. Acetone is injected into the flow in the transverse direction behind the pylon at different mass flow rates for 3 different pylon geometries and 3 angled injection cases. The height of the pylon is varied (17.32 mm, 10 mm, 6 mm) and the injection angle is such that it impinges against the pylon wall at three different angles of 30°, 45° and 60° while maintaining the other geometrical features to be the same. The study includes Schlieren imaging to find the effect of liquid injection and Pylon on the compressible flow field, and Shadowgraphy visualization was employed to evaluate the jet disintegration and atomization; Mie Scattering visualization techniques were used for evaluating the lateral spread of liquid jet spray. Mathematical techniques such as temporal variance, POD and DMD are used to analyze the temporal behavior of the jet spread. It is observed that the pylon height not only increases the penetration height but also has a significant effect on the jet breakup and atomization. The shear layer also plays a major role in jet atomization and penetration height. Angled injection case was observed to perform better than transverse injection in terms of penetration height and jet spread.

Flameholding characteristics of ethylene-fueled model scramjet in shock tunnel

The flameholding characteristics of a model scramjet were investigated experimentally. Experiments were performed in a shock tunnel at a nominal freestream Mach number of 4. The considered total enthalpy was approximately 1.7 MJ/kg. The test model consisted of a double- ramp inlet, combustor with cavity, and cowl. The investigated fuel was ethylene, with a fuel–air equivalence ratio ranging from 0.05 to 0.21. Shadowgraph and flame luminescence images were obtained. The effects of injection location, angle, and equivalence ratio on flameholding were investigated. As the equivalence ratio was increased, the flame signals in the cavity shear layer strengthened with a near-constant spreading angle for inlet injection. The flame was maintained at the shear layer above the cavity. Unlike in the inlet case, the cavity upstream injection indicated that the flame was quite unstable during steady flow, and in general, the flame height downstream of the cavity increased as the equivalence ratio increased. In line with the literature, the flame stabilization mode for inlet injection was categorized as a “cavity shear layer-stabilized flame,” while the cavity upstream injection was a “combined cavity shear layer/recirculation zone-stabilized flame.” The effect of the injection angle on flameholding indicated that transverse injection exhibited superior fuel–air mixing compared to angled injection for the inlet case. With the cavity upstream injection, the flame was effectively maintained for both the transverse and angled injections, with approximately equivalent flame spreading angles downstream of the cavity.

Experimental Analysis of Angled Injection Aerostatic Hybrid Bearings

Counter-rotation angled injection employed for aerostatic hybrid bearings reduces the cross coupling stiffness that may lead to whirl–whip instabilities at high rotation speeds. The benefits of counter-rotation injection have been known for years. Theoretical investigations were performed for water or air fed hybrid bearings but experiments were conducted only for water fed bearings. The present work is the first effort dedicated to angled injection in air fed hybrid bearings. The tests were performed for a simple rotor supported by two identical hybrid bearings. The hybrid bearings are provided with small size, shallow pockets and are fed with air via counter-rotation-oriented orifice type restrictors. An impulse turbine fed with air entrains the rotor. An impact gun applies dynamic excitations and the rotordynamic coefficients are identified from the equations of motion of the rotor. Different air feeding pressures are tested as well as high rotational speeds. Compared to the dynamic characteristics of radial injection hybrid bearings, the direct stiffness of counter-rotation injection bearings has slightly lower values and the direct damping is higher but the main impact is the drastic reduction of the cross-coupling stiffness that may have even negative values.

The role of angled-tip microcatheter and microsphere injection velocity in liver radioembolization: A computational particle-hemodynamics study.

Liver radioembolization is a promising treatment option for combating liver tumors. It is performed by placing a microcatheter in the hepatic artery and administering radiation-emitting microspheres through the arterial bloodstream so that they get lodged in the tumoral bed. In avoiding nontarget radiation, the standard practice is to conduct a pretreatment, in which the microcatheter location and injection velocity are decided. However, between pretreatment and actual treatment, some of the parameters that influence the particle distribution in the liver can vary, resulting in radiation-induced complications. The present study aims to analyze the influence of a commercially available microcatheter with an angled tip and particle injection velocity in terms of segment-to-segment particle distribution. Specifically, 4 tip orientations and 2 injection velocities are combined to yield a set of 8 numerical simulations of the particle-hemodynamics in a patient-specific truncated hepatic artery. For each simulation, 4 cardiac pulses are simulated. Particles are injected during the first cycle, and the remaining pulses enable the majority of the injected particles to exit the computational domain. Results indicate that, in terms of injection velocity, particles are more spread out in the cross-sectional lumen areas as the injection velocity increases. The tip's orientation also plays a role because it influences the near-tip hemodynamics, therefore altering the particle travel through the hepatic artery. However, results suggest that particle distribution tries to match the blood flow split, therefore particle injection velocity and microcatheter tip orientation playing a minor role in segment-to-segment particle distribution.

Angled etching of Si by ClF3–Ar gas cluster injection

Reactive gas cluster injection is an etching method that uses a neutral cluster beam without ions. This process can avoid damage caused by energetic ion irradiation and vacuum UV light from plasma. ClF3–Ar gas cluster injection was performed using a nozzle placed at various angles in the range of 0–78° from the normal to the sample. The Si substrate was anisotropically etched in the direction of the cluster beam, although the incident angle of the cluster beam was oblique. Oblique holes of 100 nm diameter and oblique square pillars of 3 µm width were fabricated with a high aspect ratio by angled cluster injection. It is expected that this process will create unprecedented structures for use in micro-electromechanical systems (MEMSs) or photonic crystals.

Fuel–Air Mixing Experiments in a Directly Fueled Supersonic Cavity Flameholder

In the present study, planar laser-induced acetone fluorescence was used to quantify the streamwise concentration distribution of an ethylene fuel surrogate (acetone-seeded nitrogen) injected directly into the recirculation region of a cavity flameholder embedded in a nonreacting supersonic airflow. The effect of injection configuration and fueling rate were studied. Parallel injection from the cavity front wall resulted in an ultra-fuel-rich recirculation region (beyond the upper flammability limit of an ethylene–air mixture) with a mixing efficiency that degraded with increased fueling rate. Downstream angled injection from the cavity floor yielded a substantial improvement in terms of the spatial uniformity and flammability of the local mixture. Its mixing efficiency was observed to be independent of fueling rate. The superior mixing ability of the latter injection configuration has the potential to provide increased cavity flameholder operability through a broader range of ignition and blowout limits and more flexibility in terms of ignitor placement than conventional direct-fueling schemes. Further investigation of its performance over a wider range of reacting conditions is warranted.

Numerical Investigation of a Trapped Vortex Miniature Ramjet Combustor

The design of a miniature ramjet combustor using gaseous methane fuel for Mach 2.5 has been conducted. The main challenges stem mainly from the insufficient space for mixing and burning, short residence time, and the flame stabilization. Impossible utilization of relatively large air-blast fuel injectors provides more difficulties for the design. The trapped vortex combustor, as a novel way of flameholding by trapping the pilot flame inside a cavity instead of exposing it to the mainstream, is selected. Three main parts are studied numerically, which include the cold flowfield characteristics, the fuel-injection schemes, and the overall combustion performance. The results show that the drag coefficient can help to determine the optimum cavity size for trapping a stable vortex. Injecting all the fuel in the cavity always leads to an overly fuel-rich condition, whereas injecting in front of the cavity with a momentum flux ratio between 0.61 and 1.0 can successfully achieve stoichiometric mixing in the cavity. However, compared to nonreacting fuel mixing, the combustion performance is found to be more sensitive to the value of . Among the cases studied, the one with a small of about 0.61 has more intense pilot flames and shorter main combustor flames. The effects of angled injection, upstream injection location, and the combustor length based on the found are also investigated.

First measurements of D(α) spectrum produced by anisotropic fast ions in the gas dynamic trap.

Angled injection of eight deuterium beams in gas dynamic trap (GDT) plasmas builds up the population of fast ions with the distribution function, which conserves a high degree of initial anisotropy in space, energy, and pitch angle. Unlike the Maxwellian distribution case, the fast ion plasma component in GDT cannot be exhaustively characterized by the temperature and density. The instrumentation complex to study of fast ions is comprised of motional Stark effect diagnostic, analyzers of charge exchange atoms, and others. The set of numerical codes using for equilibrium modeling is also an important tool of analysis. In the recent campaign of summer 2014, we recorded first signals from the new fast ion D-alpha diagnostic on GDT. This paper presents the diagnostic description and results of pilot measurements. The diagnostic has four lines of sight, distributed across the radius of an axially symmetric plasma column in GDT. In the present setup, a line-integrated optical signal is measured in each channel. In the transverse direction, the spatial resolution is 18 mm. Collected light comes to the grating spectrometer with the low-noise detector based on a charge-coupled device matrix. In the regime of four spectra stacked vertically on the sensor, the effective spectral resolution of measurements is approximately 0.015 nm. Exposure timing is provided by the fast optical ferroelectric crystal shutter, allowing frames of duration down to 70 μs. This number represents the time resolution of measurements. A large dynamic range of the camera permits for a measurement of relatively small light signals produced by fast ions on top of the bright background emission from the bulk plasma. The fast ion emission has a non-Gaussian spectrum featuring the characteristic width of approximately 4 nm, which can be separated from relatively narrow Gaussian lines of D-alpha and H-alpha coming from the plasma periphery, and diagnostic beam emission. The signal to noise ratio varies from approximately ten for the central channel to approximately five for the outermost channel. We used the special set of Monte Carlo codes to fit the measured spectra. The shape of model fit shows a good agreement with the experimental fast ion D-alpha spectrum.

Influencing factors on the mode transition in a dual-mode scramjet

An experimental investigation was performed to characterize the effects of fuel type, injector configuration, inflow total temperature and fuel injection distribution on the mode transition in a dual-mode scramjet combustor. High enthalpy vitiated air was heated to three total temperatures by the hydrogen–oxygen combustion, entering the isolator entrance at a Mach number of 2.0. Fuel was injected through a four-hole aero-ramp or transverse injector, and ignited by a gas-pilot flame. At an inflow stagnation condition of P0=0.85MPa and T0=1200K, three combustion modes, namely Pure Scram Mode, Dual-Mode Scram Mode and Dual-Mode Ram Mode, were classified through the wall pressure distributions, one-dimensional performance analysis, and optical visualization. Two critical fuel equivalence ratios were selected to divide three combustion modes. At the lower transition point, ERlc, the transition from Pure Scram Mode to Dual-Mode Scram Mode occurred corresponding to a normalized wall pressure at x/H=2.5 of 0.23; while at the upper transition point, ERuc, the transition from Dual-Mode Scram Mode to Dual-Mode Ram Mode occurred corresponding to a normalized wall pressure at x/H=2.5 of 0.34. The transition width, ERw, was defined as the difference of two transition points. In this limited range, the combustor was operating in the Dual-Mode Scram Mode. The ERuc was estimated based on the Rayleigh flow relation, and the applicability of the analytic equation was testified through a series of experiments with different boundary conditions. The experimental results showed that two transition points in the ethylene case were higher in ER than in the hydrogen case, and the measured ERuc of two fuels were all 2.5 times larger than the predicted values. However, two fuels had little difference on the transition width. Due to the angled injection, two transition points in the aero-ramp case were higher in ER than in the transverse injector case; while the influence of injector configuration on the transition width can be neglected. Two transition points and transition width increased with increase in the inflow total temperature. Although having the same changing trend, all the measured ERuc at three inflow total temperatures were approximately 3.0 times larger than the predictions. Under the constant overall ER, the transition from Dual-Mode Ram Mode to Dual-Mode Scram Mode occurred with more fuel injected in the downstream combustor. Furthermore, hysteresis was observed in the transition region, illustrating the dynamic characteristics of the Dual-Mode Scram Mode.

Increasing the cold atom density in an integrating spherical cavity

A novel method of angled incidence for diffuse laser cooling of Rb-87 is presented to improve the distribution of cold atom density in an integrating sphere. The angled injection scheme could cool more atoms in the middle of the sphere compared to the previous normal injection scheme. The loading time of the cold atoms for the angled injection scheme is twice as that of the normal injection scheme. The SNR and the contrast of the detected signal would be improved in the angled injection scheme. (C) 2014 Elsevier B.V. All rights reserved.

Inclined Injection of Supersonic Steam into Subcooled Water: A CFD Analysis

The phenomenon of direct-contact condensation gains attention because of various industrial applications; nuclear reactor emergency core cooling systems,steam driven jet injectors, direct-contact heat exchangers etc..The phenomenon was investigated computationally by injecting an inclined steam jet using a supersonic nozzle submerged in subcooled water. The condensation mechanism is based on two resistance model, which involves consideration of the heat transfer process on both sides of the interface along with use of a variable steam bubble diameter. For computations, ANSYS Fluent based Euler-Euler multiphase model is used. The angle of inclination varies from 5o to 45o at constant inlet pressure of 7 bars with water temperature of 30°C. The maximum penetration length is achieved using a right angled vertical injection.

Identification of stiffness and damping coefficients of hydrostatic bearing with angled injection

This study deals with the experimental results obtained for a hydrostatic/hydrodynamic bearing used in aerospace turbopumps. This supporting element, if fitted with angled injection directed against shaft rotation, can provide a stabilizing effect to the rotor by reducing the circumferential flow. In order to characterize this effect and to improve its numerical simulation, an experimental housing has been designed to test the three directions of injection (radial, 25° and 50°). Measurements were obtained for the centered bearing operating at 2 kr/min, 4 kr/min and 6 kr/min with supply pressures of 2.5 MPa, 3.5 MPa and 4.5 MPa. The test rig uses hot water (<50 ℃) as a working fluid. For given operating conditions, a set of dynamic excitations imposed to the rotor provides complex impedances that are used for identifying dynamic coefficients. According to many pressure plugs distributed along the housing, the pattern of the pressure field in the recess and the thin fluid film near the recess is reconstructed. The bearing flow rate is also measured. Static and dynamic experimental results are compared with theoretical results obtained bycombining a pressure pattern model with a bulk-flow analysis. A good agreement between the two methods is observed. The measured cross-coupled stiffness is lower than the predicted one, indicating that the benefits of angled injection are better than what was predicted.

Simulations of combustion with normal and angled hydrogen injection in a cavity-based supersonic combustor

Combustion characteristics in a supersonic combustor with normal and angled hydrogen injection upstream of a cavity flameholder are investigated numerically using a hybrid Reynolds-averaged Navier–Stokes/large eddy simulation method acting as a wall-modeled large eddy simulation. A turbulent incoming boundary layer with thickness of δinf = 2.5 mm is considered and a recycling/rescaling method is adopted to treat the unsteady inflow. Three injection angles, α = 30°, 60° and 90°, are considered. The results show that combustion efficiency increases with increasing injection angle since the fuel jet with larger injection angle tends to benefit more from the close coupling of flow, mixing and combustion. Moreover, it is found that the heat release distribution in the streamwise direction is more uniformly for larger injection angle than for lower injection angle, which tends to result in higher total pressure recovery in the far downstream regions for larger injection angle as uniformly-distributed heat release seems beneficial to reduce the total pressure loss for the present diffusion combustion.

Influence of Flow Structure on Compound Angled Film Cooling Effectiveness and Heat Transfer

Film cooling in turbine blades involves injecting cold air through small holes over the surface of the blade to thermally protect it against the incoming hot freestream. Compound angled film cooling, in which the injected jet is angled laterally with respect to the streamwise flow direction, is used in industrial designs owing to their lower cost of manufacture compared with shaped geometries but a high coolant spread. The current study incorporates flow structure measurements of film cooling injection flows inclined at 30 deg to a flat surface with lateral angles of 15 deg, 60 deg, and 90 deg to the freestream. Blowing ratios of 1–2 and density ratios of 1–1.5 are studied. Three dimensional velocity measurements are carried out through high resolution stereoscopic particle image velocimetry. It is observed that the typical counter-rotating vortex pair structure associated with streamwise coolant injection is replaced with a single large vortex, which causes a more lateral spread of the coolant. Infrared thermography measurements are made for the same operating points using the super position principle, which allows calculation of adiabatic effectiveness and heat transfer coefficient. The adiabatic effectiveness is high at low blowing ratios for compound angled injection due to greater proximity of the coolant jet to the wall. At higher blowing ratios, the detrimental effects on effectiveness due to jet lift-off are counteracted by the greater coolant spread due to asymmetric primary vorticity. The heat transfer coefficient is also enhanced especially in the downstream region for high compound angles. The average heat transfer coefficient due to very large compound angles is not very sensitive to changing momentum flux ratios.

Defining the Ideal Injection Techniques When Using 5-mm Needles in Children and Adults

OBJECTIVEWe aimed to establish the ideal injection techniques using 5-mm needles to reliably inject insulin into the subcutaneous fat in both children and adults and to quantify the associated pain and leakage of the test medium.RESEARCH DESIGN AND METHODSA total of 259 subjects (122 children/adolescents and 137 adults) were injected with sterile air corresponding to 20 IU insulin (200 μl) with 32-G 5-mm needles at 90° or 45°, in the abdomen and thigh, and with or without a pinched skin fold. Injection depth was assessed via ultrasonography. Subjects rated pain on a visual analog scale. Test medium injections into the abdomen and thigh (0.2–0.6 ml) were also administered to assess injection leakage.RESULTSAmong children, 5.5% of injections were intramuscular (IM) and 0.5% were intradermal, while in adults, the incidence was 1.3 and 0.6%, respectively. The frequency of IM injections was greater in boys and negligible among adult women. Subcutaneous fat thickness was the primary predictor of the likelihood of IM injections (P < 0.001). A third of all patients reported experiencing no pain during insulin injection, with children/adolescents experiencing considerably more discomfort than adults. Some leakage of medium was observed, but was unrelated to injection volume and was generally minimal.CONCLUSIONS5-mm needles are reliably inserted into subcutaneous fat in both adults and children. These needles were associated with reduced pain and minimal leakage. We recommend an angled injection with a pinched skin fold for children, while in adults, the technique should be left to patient preference.

EFFECTS OF CANTED INJECTION ANGLES ON THE SPRAY CHARACTERISTICS OF LIQUID JETS IN SUBSONIC CROSSFLOWS

The effects of variably angled injection characteristics such as liquid column trajectory and liquid column breakup length have been experimentally studied in liquid jets injected into subsonic crossflow. The fuel injection velocity and injection angle were varied to provide jet operation conditions. The pulsed shadowgraph photography with high resolution and planar liquid laser induced fluorescence measurements were used to determine the liquid column trajectory and liquid column breakup length of angles of spray in a subsonic crossflow of the airstream. The main objectives of this research are to obtain the empirical formula of the liquid column trajectory and breakup length when the injection angle is <90 deg, and these results are compared to previous results. Also in this study, the empirical formula of the trajectory in the liquid column region by the reverse injection angle of subsonic airflow was derived. As a result, this research has shown that liquid column trajectories and liquid column breakup lengths were spatially dependent on airstream velocities, fuel-injection velocities, various injection angles, and normalized injector exit diameters. Furthermore, the empirical formulas of liquid column trajectories and breakup length have different drag coefficient results between forward injection and reverse angle injection in subsonic crossflow.