Aircraft engine's infrared lock-on range due to back pressure penalty from choked convergent nozzle

Baranwal, Nidhi; Mahulikar, Shripad P.

doi:10.1016/j.ast.2014.09.020

Cited by 21 publications

(7 citation statements)

References 18 publications

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“…In the case of a choked converging nozzle, the exit area reduction (nozzle length is not altered) increases the engine backpressure, and hence the pressure ratio across the turbine decreases [31]. Therefore, a reduction in the nozzle-exit area A ne leads to reduced power output from the turbine, which in turn leads to less power to the compressor, which decreases the pressure rise across the compressor and, in turn, decreases the mass flow _ m through the compressor [31]. Thus, the outcomes of the choked converging nozzle-exit area reduction are a loss in engine net thrust, an increase in specific fuel consumption (SFC), and a decrease in mission power.…”

Section: Ir Signature Study Due To Reduction In Choked Convergingmentioning

confidence: 99%

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Infrared Signature of Aircraft Engine with Choked Converging Nozzle

Baranwal

Mahulikar

2016

Journal of Thermophysics and Heat Transfer

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Incorporation of an infrared suppressor is generally accompanied by a compromise in engine performance, which indirectly reduces the effectiveness of infrared signature suppression. This investigation illustrates the percentage increase in the infrared signature level in the 1.9-2.9 μm and 3-5 μm bands resulting from an increase in engine backpressure in a jet engine due to a reduction in the exit area of a choked converging nozzle. The effectiveness of optically blocking the hot engine parts by reducing the choked nozzle-exit area is estimated. Thermodynamic offdesign point analysis of the jet engine is done using GasTurb software to evaluate the percentage reduction in thrust and the net change in infrared signature level for the reduced choked converging nozzle-exit area relative to that for the design point. NomenclatureA ne = converging nozzle-exit area, m 2 A ne;dp = design point nozzle-exit area, m 2 A pl = planar projected area of discretized elements of engine components, m 2 c = velocity of light in vacuum; 2.99792 × 10 8 , m∕s D a = axial distance measured from the turbine-exit disk, m E = irradiance incident on a surface; ∫ E λ dλ, W∕m 2 F = thrust, kN F C = engine thrust with converging nozzle, kN F C−D = engine thrust with converging-diverging nozzle, kN h = Planck's constant; 6.62606 × 10 −34 , J · s k = Boltzmann's constant; 1.38065 × 10 −23 , J∕K L = directional radiance from a surface; ∫ L λ dλ, W∕m 2 · sr M e = nozzle-exit Mach number M ∞ = flight Mach number _ m = engine mass flow rate, kg∕s P = absolute pressure, kPa P o = nozzle total pressure, kPa T = absolute temperature of a surface, K T e = temperature at the nozzle exit, K V e = exhaust gas velocity at the nozzle exit, m∕s α = semicone angle, deg Δ = difference operator ΔA ne % = percentage change in A ne relative to A ne;dp ΔA ne;red % = percentage reduction in A ne relative to A ne;dp ΔF% = percentage change in thrust relative to F dp for case 1 ΔIRSL% = percentage change in infrared signature level relative to the design point infrared signature level λ = wavelength, μm λ 1 = lower limit of detector's wavelength band λ 2 = upper limit of detector's wavelength band τ = atmospheric transmissivity between infrared detector and aircraft along a line of sight ϕ = viewing aspect angle; 0 deg for direct rear view along engine axis, deg ω = solid angle subtended, srSubscripts atm = atmospheric bg-tp = background replaced by tailpipe in detector's field of view det = infrared detector dp = design point f = constant design point thrust IS = internal source jp = jet pipe red = due to a reduction in the choked converging nozzleexit area T = constant turbine-exit temperature tp = tailpipe λ = spectral quantity λ 1 − λ 2 = in detector's wavelength band λ 1 − λ 2 1 = decrease in infrared signature level for case 1 2 = increase in infrared signature level for case 2 I = i n1.9-2.9 μm band II = in 3-5 μm band

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Section: Ir Signature Study Due To Reduction In Choked Convergingmentioning

confidence: 99%

“…An increase in fuel flow rate for constant design point thrust F dp Fig. 1 Schematic sketch of the rear portion of the aircraft engine layout [31]. Fig.…”

Section: Ir Signature Study Due To Reduction In Choked Convergingmentioning

confidence: 99%

Infrared Signature of Aircraft Engine with Choked Converging Nozzle

Baranwal

Mahulikar

2016

Journal of Thermophysics and Heat Transfer

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“…Thermal cloaking has become key research issues in the development of modern military equipment and facilities, 1 , 2 , 3 , 4 such as aircrafts, 5 , 6 armor vehicles, 7 , 8 naval vessels, 9 , 10 and among others. As these researches involve the convective heat transfer closely, extending thermal cloaking from pure thermal conduction to convective heat transfer has played a critical role in thermal fluid motion community, which has facilitated the explorations in manipulating heat flux proactively as well.…”

Section: Introductionmentioning

confidence: 99%

Convective thermal cloaks with homogeneous and isotropic parameters and drag-free characteristics for viscous potential flows

Yao¹,

Wang²,

Wang³

et al. 2022

iScience

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“…6 The alteration of nozzle exit area is not only the central influence of aircraft engine IR signature radiation but also the chief effect of aircraft engine performance. 7 It means that for aircraft engine the thrust of a given pressure and temperature is determined by the dimension of nozzle. Consequently, a variable area nozzle could provide appropriate thrust for different flight stages (such as take-off, cruise and climb).…”

Section: Introductionmentioning

confidence: 99%

Nozzle dimension design for aircraft engine infrared signature and thrust active control using MOEA/D

Zhao

Zheng

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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Aircraft infrared signature is one of the most important properties for the military aircraft survivability. In terms of military aircraft, the exhaust system is the most significant infrared radiation source. The exhaust system accounts for more than 90% of the aircraft infrared radiation, and that the exhaust nozzle contributes the most significant infrared radiation of the whole radiation energy provided by the exhaust system from the rear aspect. Low detectionable feature for military aircraft has attracted more importance to promote aircraft survivability via reducing infrared signature. The alteration of nozzle exit area affects an aircraft engine performance; meanwhile, it severely influences the engine infrared signature radiation from the rear side. The present paper is mainly focused on searching an appropriate group of nozzle exit diameter and throat to exit diameter ratio, which can reduce infrared signature radiation while cutting down the loss of thrust. Hence, objectives involve two aspects: one is minimum infrared signature level, and the other is minimum thrust loss. The multi-objective evolutionary algorithm based on decomposition has been employed to solve this bi-objective optimization problem. The optimization results illustrate that dimension selection range and throat to exit diameter ratio exert more important effect on the thrust loss and infrared signature level. Furthermore, the thrust plays significant role for deciding nozzle exit diameter and throat diameter.

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Aircraft engine's infrared lock-on range due to back pressure penalty from choked convergent nozzle

Cited by 21 publications

References 18 publications

Infrared Signature of Aircraft Engine with Choked Converging Nozzle

Infrared Signature of Aircraft Engine with Choked Converging Nozzle

Convective thermal cloaks with homogeneous and isotropic parameters and drag-free characteristics for viscous potential flows

Nozzle dimension design for aircraft engine infrared signature and thrust active control using MOEA/D

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