Experimental Study of Vitiation Effects on Scramjet Mode Transition

Haw, Willie; Goyne, Christopher P.; Rockwell, Robert D.; Krauss, Roland H.; McDaniel, James C.

doi:10.2514/1.49090

Cited by 17 publications

(6 citation statements)

References 3 publications

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“…Compared with experimental and numerical results referred to [6][7][8][9][10][11][12][13][14], the essential tendency of vitiation effects on scramjet performance is identical, which evidenced that the method based on thermodynamic cycle analysis can validate and predict ground test results effectively and offer forecast when choosing simulation criterions and heating mediums. Therefore, this method will economize lots of costs and time.…”

Section: Calculated Resultsmentioning

confidence: 99%

“…It was discovered that as the increase of the level of H 2 O, CO 2 or H 2 O and CO 2 in vitiated air, the pressure rise due to combustion and isolator shock train length decreased and the combustion mode might be changed [10]. The fuel equivalence ratio at which mode transition takes place raised when compared with clean air [11,12], and the influence of water and carbon dioxide on combustor performance was nonlinear as the concentration of vitiation species increased [13].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Air Vitiation on Scramjet Performance Based on Thermodynamic Cycle Analysis

Chang¹

2014

J Aeronaut Aerospace Eng

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The influences of air vitiation on scramjet performance were studied in this paper based on thermodynamic cycle analysis. By the aid of NASA Glenn's computer program Chemical Equilibrium with Applications (CEA), parameters of vitiated air at combustion heater exit could be calculated. Based on thermodynamic cycle analysis, scramjet performance, including internal thrust, specific thrust, and specific impulse, were analyzed with 9 simulation criterions under Mach 4.5 and 6.5 conditions, respectively. The results show that, (1) specific heat and specific heat ratio of vitiated air are mainly affected by combustion heating medium, and also have minor connection with temperature criterions. Moreover, choosing different simulation criterions influences the temperature or pressure between clean air and vitiated air significantly; (2) the internal thrust and specific thrust of scramjet with hydrogen heated airstream are greater than that of scramjet with alcohol and kerosene heated airstream; (3) matching static pressure and dynamic pressure will obtain higher internal thrust compared to total pressure, and the effect of pressure criterions on internal thrust is more remarkable than temperature criterions. On the other hand, these findings proved that the method based on thermodynamic cycle analysis is a simple, dependable, and effective approach to evaluate the scramjet performance affected by air vitiation.

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Section: Calculated Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Air Vitiation on Scramjet Performance Based on Thermodynamic Cycle Analysis

Chang¹

2014

J Aeronaut Aerospace Eng

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“…This will be achieved through quantification of the similarities and differences of axial pressure distributions obtained from experimental testing of a dual-mode scramjet. The second objective is to provide insight into the relevance of previously published results obtained in the direct-connect facility of the current study [14][15][16][17]. Of particular concern here is to confirm that the direct-connect facility can capture many of the relevant flow physics of a freejet test.…”

Section: Introductionmentioning

confidence: 89%

Comparison of a Direct-Connect and Freejet Dual-Mode Scramjet

Steva

Goyne

Rockwell

et al. 2015

Journal of Propulsion and Power

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Testing of identical dual-mode scramjet flowpath geometries in the freejet and direct-connect configurations was conducted in two separate facilities. These tests enabled a comparison study between the two configurations, which was directed toward the determination of the effects of inlet distortion and backpressure on the performance and operability of a dual-mode scramjet. Bulk flow conditions were matched between the two facilities at the isolator entrance plane to simulate Mach 4.8 flight, and a series of metrics were established to quantify similarities and differences. The effects of flowpath backpressure in the direct-connect case were seen to be isolated to regions close to the exhaust. An approximate 10% decrease in combustor pressure rise and consequently integrated pressure force were observed in the freejet configuration; shock train length, however, remained the same. Mode transition was delayed from an equivalence ratio of ∼0.5 in the direct-connect case to ∼0.7 in the freejet configuration. Further, ignition difficulties were experienced in the freejet tests which were not encountered in those of direct-connect tests, limiting the scope of comparable test points. This work represents the first attempt at a quantitative comparison in the literature of an identical direct-connect and freejet dual-mode scramjet. Nomenclature A = cross-sectional area D = isolator duct height F = integrated pressure force H = fuel injector ramp normal height L = shock train length M 0 = freestream Mach number M u = Mach number at shock train leading edge M c = Mach number at combustor entrance _ m TBIVmc = predicted freejet flowpath mass capture _ m TBIVnom = nominal freejet facility mass flow rate _ m test = as tested facility mass flow rate (direct connect or freejet) P s = static pressure P 0 = total pressure p d ∕p u = peak static pressure/static pressure at leading edge of shock train Re u = unit Reynolds number, m −1 Re θ = Reynolds number based on boundary-layer momentum thickness T s = static temperature T 0 = total temperature x = axial distance θ = boundary-layer momentum thickness at the leading edge of shock train ϕ = angle of flowpath divergence from the horizontal φ = fuel equivalence ratio

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“…A 2.9 deg divergence of the flowpath started at the leading edge of the ramp and extended downstream to exit with atmospheric backpressure. The exit plane corresponded to a distance of 37.1 cm downstream of fuel injection [9]. This relatively simple combustor geometry was chosen to facilitate comparison of results from CFD simulations [5] with combustion diagnostics.…”

Section: A University Of Virginia Supersonic Combustion Facilitymentioning

confidence: 99%

Diode Laser Absorption Sensor for Combustion Progress in a Model Scramjet

Schultz¹,

Goldenstein²,

Jeffries³

et al. 2014

Journal of Propulsion and Power

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The development and use of a tunable diode laser absorption spectroscopy sensor for combustion product water vapor in a hydrogen-fueled model scramjet combustor are presented. A pair of absorption transitions was selected from the combination bands of water vapor near 1.4 μm exploiting telecommunications diode laser and fiber technologies. Wavelength-modulation spectroscopy with detection of the peak second-harmonic signal was used owing to its superior noise-rejection capabilities. The sensor measured temperature and H 2 O column density at two axial planes downstream of fuel injection with the absorption line-of-sight positioned at over 40 measurement locations using a translation stage system. The combustion product concentration and the gas temperature were not uniform along the line-of-sight, and the influence of these nonuniformities on the interpretation of the tunable diode laser measurements is discussed. The measurements are compared with published computational fluid dynamics simulations using two different kinetic mechanisms. Nomenclature A= integrated absorbance f = modulation frequency, Hz I t = transmitted spectral intensity, W∕cm 2 · s −1 I 0 = incident spectral intensity, W∕cm 2 · s −1 L = path length, cm P = pressure, atm R i = specific gas constant of species i, J · kg −1 · K −1 S = line strength, cm −2 ∕atm T = temperature, K ν = optical frequency, cm −1 α = absorbance γ air = air-broadening coefficient, cm −1 · atm −1 γ self = self-broadening coefficient, cm −1 · atm −1 Δν c = collisional linewidth, cm −1 ρ = bulk gas density, kg · m −3 ρ i = partial density of species i, kg · m −3 σ i = column density of species i, kg · m −2 φ = H 2 -air equivalence ratio φ ν = line shape function χ i = gas mole fraction of species i

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Experimental Study of Vitiation Effects on Scramjet Mode Transition

Cited by 17 publications

References 3 publications

Effects of Air Vitiation on Scramjet Performance Based on Thermodynamic Cycle Analysis

Effects of Air Vitiation on Scramjet Performance Based on Thermodynamic Cycle Analysis

Comparison of a Direct-Connect and Freejet Dual-Mode Scramjet

Diode Laser Absorption Sensor for Combustion Progress in a Model Scramjet

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