Penetration of gaseous jets injected into a supersonic stream.

Billig, F. S.; Schetz, Joseph A.

doi:10.2514/3.28721

Cited by 248 publications

(58 citation statements)

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“…The decay rate of the maximum concentration was found to be nearly insensitive to the orifice shape. The same tendencies for penetration height and maximum mass fraction decay were observed in an experimental study with a Mach 2.5 crossflow, which also examined the characteristics of supersonic and subsonic injections in the matched-pressure conditions (where the fuel is injected at the effective backpressure [11]) as well as offdesign conditions [12]. A considerable advantage of a diamond orifice in penetration was also reported by Schetz et al [13], who examined the flowfields in the presence of sonic injection of helium into a Mach 3.8 airflow through circular and diamond injectors inclined at 30 deg in a combined experimental/computational approach.…”

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confidence: 57%

Mixing Characteristics of Inclined Fuel Injection via Various Geometries for Upstream-Fuel-Injected Scramjets

Ogawa

2015

Journal of Propulsion and Power

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Efficient fuel/air mixing plays a crucial role in successful operation of hypersonic airbreathing engines, particularly scramjets, where fuel must be injected into high-speed crossflow and mixed with air at an extremely short timescale. This paper presents the results of a numerical study that investigates the effects of various orifice shapes on fuel mixing characteristics into hypersonic airflow at Mach 5, aiming at the application to scramjet operation with upstream fuel injection at Mach 10. The performance of the injectors at an inclination angle of 45 deg are assessed with respect to various criteria such as the mixing efficiency, streamwise circulation, total pressure recovery, fuel penetration, and spread. Streamwise slot injectors have been found to yield higher mixing efficiency than the other injectors tested (namely, square, circular, diamond, and triangular injectors), owing to the buffering effects. Apparent higher total pressure recovery has been obtained with these rectangular injectors, but their advantages have diminished significantly with the alignment of the trailing-edge position. The highest vertical penetration has been achieved by the square injector, whereas the performances of other injectors with a sharp leading edge have been found to be affected considerably by the axis switch phenomenon due to inclined injection at higher injection pressure. A major influence of the fore and aft shapes of the orifice has been observed on the three-dimensional bow shock formation and wake recirculation, respectively. Nomenclature A = cross section at a streamwise station AR = aspect ratio (streamwise/spanwise) A j = injector area on floor, m 2 A n j = injector area normal to jet, m 2 c = mass fraction c H 2 = hydrogen mass fraction c O 2 = oxygen mass fraction c s = stoichiometric mass fraction D = effective injector diameter, m H = height of computational domain, m h f = fuel penetration height J = jet-to-freestream momentum flux ratio L = length of computational domain, m L 0 = distance to upstream end of injector, m _ m = mass flow rate, kg∕s p = static pressure, Pa p 0 = total pressure, Pa p 02 = pitot pressure, Pa U = crossflow velocity, m∕s W = domain width (injector spacing), m w f = lateral fuel spread x = streamwise direction, m y = spanwise direction, m z = vertical direction, m α j = injection angle, deg Γ = streamwise circulation γ= specific heat ratio Δp 0 = total pressure loss, Pa η m = mixing efficiency Φ = fuel/air equivalence ratio χ m = overall mesh refining factor χ m xy = refining factor in x and y directions χ m z = refining factor in z direction ω x = streamwise vorticity, ∕s Subscripts j = jet property STA = stream-thrust-averaged value ∞ = freestream property

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confidence: 57%

Mixing Characteristics of Inclined Fuel Injection via Various Geometries for Upstream-Fuel-Injected Scramjets

Ogawa

2015

Journal of Propulsion and Power

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“…The effective backpressure p eb has been considered as an important metric for the performance of fuel injection, conveniently accounting for the state of the flowfield in the vicinity of the injector orifice [13,14,22], as described formerly in Sec. I.…”

Section: Effective Backpressurementioning

confidence: 99%

“…A notion of the effective backpressure was introduced by Schetz and Billig as another metric for optimum fuel injection [13]. This is analogous to the backpressure around a jet injected into the quiescent air [14,26].…”

Section: Introductionmentioning

confidence: 99%

“…The interactions between fuel and air including mixing, ignition, and combustion occur at an extremely short time scale, rendering the development of effective and reliable fuel injection systems crucially important. The significance of fuel injection in high-speed airbreathing engines has brought about a considerable number of preceding studies for the last half-century, starting with early experimental and analytical investigations of underexpanded injection flowfields in supersonic crossflow [12,13]. Fuel injection for supersonic combustion commonly aims to achieve both high efficiency and effectiveness simultaneously, primarily targeting three objectives [11,14]: 1) high mixing efficiency to ensure desirable mixture of fuel and air before entering the combustor, 2) minimum total pressure losses in the mixing process to maintain high stream thrust, and 3) proper penetration of the injected fuel into the airstream for ignition and sustained combustion.…”

Section: Introductionmentioning

confidence: 99%

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Physical Insight into Fuel-Air Mixing for Upstream-Fuel-Injected Scramjets via Multi-Objective Design Optimization

Ogawa

2015

Journal of Propulsion and Power

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Fuel injection and mixing into air play a crucial role in the operation of hypersonic airbreathing propulsion systems, particularly scramjet engines featuring upstream fuel injection. This study applies an advanced design methodology combining computational fluid dynamics and evolutionary algorithms assisted by surrogate modeling to a multi-objective optimization for fuel injection in a Mach 5.7 crossflow after the initial compression in a scramjet intake operating at Mach 7.6. Optimization is performed for elliptical injector configurations defined by four design parameters (i.e., the injection angle, spanwise spacing, aspect ratio, and radius of the injector), simultaneously aiming to maximize three objectives, that is, fuel/air mixing, total pressure saving, and fuel penetration into the crossflow. Statistical methods based on global sensitivity analysis are employed to assess the optimization results in conjunction with surrogate models to identify key design factors with respect to the three design objectives and additional performance measures. Major effects of the injection angle and aspect ratio have been observed on all considered design criteria. The spanwise spacing has been found to have considerable influence on the total pressure recovery, fuel penetration, and lateral spread when the injection pressure is adjusted to maintain a constant fuel/air equivalence ratio. Low-angle fuel injection through a highly elliptic orifice with wide spanwise spacing demonstrated the most comprehensive advantages in overall aspects. NomenclatureA j = injector area on floor, m 2 A n j = injector area normal to jet, m 2 AR = injector aspect ratio a j = semimajor axis of injector, m c = mass fraction c s = stoichiometric mass fraction c H 2 = hydrogen mass fraction c O 2 = oxygen mass fraction D = effective injector diameter, m f = vector of objective functions H = vertical height of computational domain, m h f = fuel penetration height (normalized) J = jet-to-freestream momentum flux ratio L = streamwise length of computational domain, m k = number of clustering L 0 = distance to upstream end of injector, m _ m = mass flow rate, kg∕s N = size of population pool p = static pressure, Pa p eb = effective backpressure (normalized) p j = jet static pressure (normalized) p 02 = pitot pressure behind normal shock, Pa p 0 = total pressure, Pa r j = effective injector radius, m S i = first-order sensitivity index S T i = total-effect sensitivity index U = freestream velocity, m∕s u = velocity, m∕s W = injector spacing (spanwise domain width), m w f = fuel lateral spread (normalized) X i = input vector for decision variable x i X = input matrices comprising vectors X i x = streamwise coordinate, m x = vector of decision variables Y = input vector for output parameter y y = spanwise coordinate, m z = vertical coordinate, m α j = injection angle, deg Γ= streamwise circulation (normalized) Δp 0 = total pressure loss (normalized) Δt = time step, s Δx = spatial step, m Δμ χ = mesh sensitivity error of parameter χ η m = mixing efficie...

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“…A number of investigations aimed at the development of thrust vector control systems were carried out in the 1960s to study the pressure distribution in the region around the injector and the resulting normal force and pitching moment. 4,11,12 Several researchers 10,11,[13][14][15][16][17][18] analyzed this flow field through analytical models and experiments. However, these efforts have been only partially successful due in large part to the difficulty of experimentally measuring the local flow without disrupting it and in part, due to the inherent complexity of the flow physics involved.…”

Section: Introductionmentioning

confidence: 99%

Detailed flow physics of the supersonic jet interaction flow field

2009

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The supersonic jet interaction flow field generated by a sonic circular jet with a pressure ratio of 532 exhausting into a turbulent MACH 4.0 cross flow over a flat plate was investigated using numerical simulations. The simulations made use of the three-dimensional Reynolds-averaged Navier-Stokes ͑RANS͒ equations coupled with Wilcox's 1998 k-turbulence model. The numerical solution was validated with experimental data that include the pressure distribution on the flat plate, with an empirical formula for the height of the barrel shock, and with the Schlieren pictures showing the location and shape of the main shock formations. The simulations correctly captured the location and shape of the main flow features and compared favorably with the experimental pressure distribution on the flat plate. The validated numerical simulation was used to investigate in detail the flow physics. The flow field was found to be dominated by the shock formations and their coupling with the strong vortical structures. Three primary shock formations were observed: a barrel shock, a bow shock, and a separation-induced shock wave. While the general structure of the barrel shock was found to be similar to that of the underexpanded jet exhausting into a quiescent medium, two unique features distinguished the flow field: the concave indentation in the leeside of the recompression ͑barrel͒ shock and the folding of the windward side of the barrel shock due to an inner reflection line. The presence of the steep pressure gradients associated with the shocks creates strong vortical motions in the fluid. Six primary vortices were identified: ͑i͒ the well-known horseshoe vortex, ͑ii͒ an upper trailing vortex, ͑iii͒ two trailing vortices formed in the separation region and, aft of the bow shock wave, ͑iv͒ two more trailing vortices that eventually merge together into one single rotational motion. The low-pressure region aft of the injector was found to be generated by the combined effect of the concave indentation in the leeside of the barrel shock and the lower trailing vortices. The trailing vortices were found to be the main mechanism responsible for the mixing of the injectant with the freestream fluid.

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Penetration of gaseous jets injected into a supersonic stream.

Cited by 248 publications

References 5 publications

Mixing Characteristics of Inclined Fuel Injection via Various Geometries for Upstream-Fuel-Injected Scramjets

Mixing Characteristics of Inclined Fuel Injection via Various Geometries for Upstream-Fuel-Injected Scramjets

Physical Insight into Fuel-Air Mixing for Upstream-Fuel-Injected Scramjets via Multi-Objective Design Optimization

Detailed flow physics of the supersonic jet interaction flow field

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