CN101976275B - Airplane infrared radiation and atmospheric transmittance modeling method - Google Patents

Abstract

The invention discloses an airplane infrared radiation and atmospheric transmittance modeling method, belonging to the field of airplane infrared radiation modeling and simulation in computer simulation. The modeling method comprises the following steps of: firstly acquiring an airplane infrared radiation intensity interface, establishing an airplane surface skin temperature model by integrating surrounding environmental radiation, and calculating airplane surface skin infrared radiation intensity according to an area model; and then establishing an engine effuser infrared radiation intensity model; and finally establishing an plume input parameter model and plume temperature model and calculating plume infrared radiation intensity. After acquiring an airplane zero-distance infrared radiation intensity model, the invention adopts software Modtran4 to establish a transmission radiation model of infrared radiation in an atmospheric environment to acquire atmospheric transmittance and further obtain an infrared radiation intensity signal reaching an sensor terminal. In the modeling method, the models are simple, and experiment data accords with real conditions. The modeling method can be applied to platform infrared scene generation and infrared target detection platforms easily.

Description

Aircraft infrared radiation and atmospheric transmittance modeling method

Technical field

The present invention relates to a kind of aircraft infrared radiation and atmospheric transmittance modeling method, belong to aircraft infrared radiation modeling and simulation field in the Computer Simulation.

Background technology

It is significant to platform detection system and the research of infrared imaging analogue system in the Military Simulation system, to set up aerospace plane infrared simulation model.At present existing a lot of scholars do this respect research and have obtained certain achievement in research, yet how based on the also not consideration of influence to engine working process of state of flight such as the height of aircraft and speed and state of flight.Also have the scholar to adopt CFD to carry out the infrared signature temperature of numerical simulation calculation aircraft, yet this method is applicable to infrared stealth and structural design analysis, is difficult to be applied in the middle of the REAL TIME INFRARED THERMAL IMAGE emulation.Therefore how from the demand of emulation, problem demanding prompt solution in setting up a kind of modeling method that is suitable at the aircraft infrared simulation and being.

The aircraft infrared signature is mainly reflected in aircraft surfaces covering, engine jet pipe mouth and plume three parts.At present, machine is carried out also mainly concentrated this three part of research of modeling and simulation of ir signature.Wherein, Temperature model comparative maturity to covering, plume; Consider the pneumatic heat problem of aircraft skin through introducing heat transfer principle in the computing machine infrared imaging emulation of the high-speed moving object of Yu Weijie research, adopted Newton iteration method to find the solution the temperature after the aircraft balanced; Gao Sili has set up the plume temperature field of aircraft aloft in the modeling and simulation of airbound target wake flame infrared radiation signal, can be used to set up the plume temperature field of aircraft.

The aircraft infrared radiation arrives through propagation in atmosphere in the process of sensor side owing to receive the atmospheric attenuation and the path radiation effect in DIFFERENT METEOROLOGICAL CONDITIONS and geographic position, and the infrared radiation that sensor side receives is difference also.The National University of Defense technology has carried out the C++ code encapsulation of Modtran4 software to propagation in atmosphere infrared radiation software, can conveniently be used for the foundation of infrared propagation in atmosphere model.

Summary of the invention

The objective of the invention is in order to solve in simulation process; Resolve the technical matters of Model Calculation aircraft infrared intensity value according to the current motion state of target; In conjunction with synthetic natural environment, thermal conduction study, theoretical, the aerodynamics relevant knowledge of engine; Propose a kind of aircraft infrared radiation and atmospheric transmittance modeling method, engine mockup is applied in the middle of the temperature computation of aircraft, reach the purpose that to resolve the aircraft infrared radiation according to the current flight state.

Aircraft infrared radiation and atmospheric transmittance modeling method comprise following step:

Step 1: the infrared intensity value of obtaining aircraft

Aircraft is divided into aircraft surfaces covering, jet pipe and three parts of plume, the independent temperature T of calculating each several part _i, calculating i parts of aircraft then is T in temperature _iUnder radiance be N _i:

$N_i=\frac{1}{\mathrm{\&pi;}}{\&Integral;}_{{\mathrm{\&lambda;}}_1}^{{\mathrm{\&lambda;}}_2}\frac{{\mathrm{\&epsiv;}}_i\&CenterDot;c_1}{({\mathrm{\&lambda;}}^5\exp ({\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000278285500021.png,HSA00000278285500051.png"\; state="\{\{state\}\}">c</figure-callout>}}_2/\mathrm{\&lambda;}{T}_i)-1)}\mathrm{d\&lambda;}---\left(1\right)$

Wherein, N _iUnit is W/m ²Sr, promptly watt of/meter ²Sterad, ε _iFor being the emissivity of i part, λ ₁, λ ₂Be detecting band scope, c ₁Be first radiation constant, 3.71418 * 10 ⁸Wm ^-2μ m ⁴, c ₂Be second radiation constant, 1.4388 * 10 ⁴μ mK.λ is the wavelength variable, and unit is um.

Obtain the zero distance infrared intensity value I of direction of visual lines aircraft i part _iFor:

I _i＝N _iA _i (2)

Wherein: I _iUnit be W/sr, A _iBe swept area on the direction of visual lines, unit is m ²

Step 2: set up aircraft surfaces covering infrared intensity model

1) sets up aircraft ambient radiation model

Set up the ambient radiation model of solar radiation, the earth self radiation, sky radiation, four aspects of earth reflected solar radiation, finally obtain aircraft ambient radiation model;

2) set up pneumatic thermal model

The wall surface temperature of adiabatic wall is recovery temperature T _γ:

$T_{\mathrm{\&gamma;}}=T_{\&infin;}(1+\mathrm{\&sigma;}\frac{\mathrm{\&gamma;}-1}{2}{\mathrm{Ma}}^2)---\left(12\right)$

Wherein: T _∞Be the place ahead temperature of incoming flow, equate with environment temperature; γ is a gas adiabatic exponent; σ is a coefficient of restitution; Ma is the airplane motion Mach number, then, sets up pneumatic thermal model according to the method in the computing machine infrared imaging emulation of high-speed moving object.

3) equilibrium establishment equation;

Balance equation is:

Q _i+q _o＝q _abs+q _rad+q _cdi+q _cv (13)

Wherein: Q _iBe the energy of ambient atmosphere environmental radiation, q _oSend and arrive the heat of object inside surface by the engine endogenous pyrogen, by the decision of engine work at present state, q _RadFor being radiated the heat in the environment, q _AbsBe the heat that surfacing absorbs, q _CdiBe the heat of external world's conduction, q _CvBe convection heat transfer;

Adopt Newton iteration method to find the solution nonlinear equation (13), calculate temperature after the covering balance, then according to the radiance value N of formula (1) gauging surface covering _Skin

4) set up aircraft surfaces covering area model

At direction of visual lines aircraft surfaces covering area model be:

$A_{\mathrm{fus}}=\left\{\begin{array}{cc}{A}_{\mathrm{hd}}\cos {\mathrm{\&theta;}}_{\mathrm{asp}}+(A_{\mathrm{bd}}+2A_{\mathrm{wng}})\sin {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="0"\; label="asp"\; filenames="HSA00000278285500022.png,HSA00000278285500023.png"\; state="\{\{state\}\}">asp</figure-callout>}}& 0\&le;{\mathrm{\&theta;}}_{\mathrm{asp}}<90\\ (A_{\mathrm{bd}}+2A_{\mathrm{wng}})\sin {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="90"\; label="asp"\; filenames="HSA00000278285500053.png"\; state="\{\{state\}\}">asp</figure-callout>}}& 90\&le;{\mathrm{\&theta;}}_{\mathrm{asp}}<1\end{array}---\left(14\right)\right.$

Wherein, A _Hd, A _Bd, A _WngRepresent the area of head, fuselage, wing respectively, θ _Asp=arc cos (cos θ _AzCos θ _El), θ _AzBe the position angle on the line of observation, θ _ElBe the angle of pitch on the line of observation, A _Hd=π R ², A _Bd=2RL _bR is a body radius, L _bLength for fuselage.

5) obtain aircraft surfaces covering radiation intensity model

According to step 1)-step 4), then aircraft surfaces covering infrared intensity model is:

I _skin＝N _skin·A _fus (15)

Step 3: set up engine jet pipe infrared intensity model

Be specially:

A) set up air intake duct outlet temperature model

${T_B}^{*}=T_{\mathrm{amb}}(1+\frac{k-1}{2}{\mathrm{Ma}}^2)---\left(16\right)$

In the formula: T _B ^*Be air intake duct outlet temperature, k is a specific heats of gases ratios, and value is 1.4, and Ma is the airplane motion Mach number, T _AmbBe environment temperature, determine by the current flight height.

The pressure ratio π of air intake duct ^* _BFor:

${{\mathrm{\&pi;}}^{*}}_B={\mathrm{\&sigma;}}_i{(1+\frac{k-1}{2}{\mathrm{Ma}}^2)}^{(k-1/k)}---\left(17\right)$

Wherein: σ _iTotal pressure recovery coefficient for air intake duct.

B) set up blower outlet section temperature model

${T_{\mathrm{\&kappa;}}}^{*}={T_B}^{*}(1+\frac{{{{\mathrm{\&pi;}}^{*}}_{\mathrm{\&kappa;}}}^{(k-1/k)}-1}{{{\mathrm{\&eta;}}^{*}}_{\mathrm{\&kappa;}}})---\left(18\right)$

Wherein: T _κ ^*Be blower outlet section temperature, η ^* _κBe compressor efficiency, π ^* _κBe pressure ratio.

C) set up combustor exit section temperature model and after-burner outlet temperature model

Non-afterburning state lower combustion chamber outlet temperature model is:

${T_{\mathrm{\&Gamma;}}}^{*}={T_{\mathrm{\&kappa;}}}^{*}+T_{\mathrm{amb}}({{{\mathrm{\&pi;}}^{*}}_{\mathrm{\&Gamma;}}}^{(k-1/k)}-\frac{e-1}{{{\mathrm{\&eta;}}^{*}}_{\mathrm{\&kappa;}}}-1)---\left(19\right)$

Wherein: T _Γ ^*Be the combustor exit section temperature, e=a η ^* _κη ^* _T, η ^* _TBe engine turbine efficient, a value is 1.02～1.04, firing chamber step-up ratio π ^* _Γ=π ^* _Bπ ^* _κ

If engine operation is at afterburning state, the after-burner outlet temperature is T _Φ ^*, then after-burner outlet temperature model is:

T _Φ ^*＝1.61T _Γ ^* (20)

D) set up the temperature model in turbine outlet cross section

${T_T}^{*}={T_{\mathrm{\&Gamma;}}}^{*}(1-(1-\frac{1}{{{{\mathrm{\&pi;}}^{*}}_T}^{(k_1-1/k_1)}}){{\mathrm{\&eta;}}^{*}}_T)---\left(21\right)$

Wherein: η _T ^*Be the turbine efficiency level, value is 0～1, π ^* _TBe turbine step-up ratio, k _iBe specific heats of gases ratio, value 1.25.

E) set up the temperature in nozzle model

Aircraft is under non-afterburning state, and the temperature in nozzle model is:

${T_c}^{*}={T_T}^{*}-\frac{k_i-1}{k_i{R}_{\mathrm{<figure-callout\; id="2"\; label="i\; c\; c"\; filenames="HSA00000278285500021.png,HSA00000278285500051.png"\; state="\{\{state\}\}">i</figure-callout>}}}\frac{{c_c}^{}}{}\frac{{{}_{}}^2}{2}---\left(22\right)$

Wherein: c _cBe combustion gas exhaust velocity after the complete expansion in jet pipe, R _iBe gas law constant, get 289.3J/KgK; c _cObtain through following formula:

Wherein: is the jet pipe velocity coefficient, and

is used for estimating the loss of air-flow at jet pipe.

Aircraft is under afterburning state, and the temperature in nozzle model is:

${T_c}^{*}={T_{\mathrm{\&Phi;}}}^{*}-\frac{k_i-1}{k_i{R}_{\mathrm{<figure-callout\; id="2"\; label="i\; c\; c"\; filenames="HSA00000278285500021.png,HSA00000278285500051.png"\; state="\{\{state\}\}">i</figure-callout>}}}\frac{{c_c}^{}}{}\frac{{{}_{}}^2}{2}---\left(24\right)$

Wherein, c _cObtain through following formula:

According to the duty of aircraft current flight, select different models to obtain the nozzle outlet temperature, bring temperature into formula (1), calculate the infrared radiation brightness value N of jet pipe _Nozzle

F) set up nozzle exit plane product module type

Nozzle exit plane product module type is on direction of visual lines:

Wherein, R _HsBe the spout radius.

G) obtain engine jet pipe infrared radiation model

Through step a)～step f), engine jet pipe infrared radiation model is:

I _nozzle＝N _nozzle·A _hs (27)

Wherein, I _NozzleInfrared intensity for the jet pipe of boarding a plane at direction of visual lines.

Step 4: set up plume infrared intensity model and be specially:

(1) at first establishes atmospheric pressure P under the current flight height _HWith the mathematical model of density p, atmospheric pressure P _HMathematical model be:

$P_H=\left\{\begin{array}{cc}1.0133\&times;{10}^5{(1-H/44.308)}^{5.2553}& 0\&le;H<11\mathrm{Km}\\ 0.277\&times;{10}^5{e}^{\frac{11-H}{6.338}}& 11\mathrm{Km}\&le;H\&le;20\mathrm{Km}\end{array}\right.---\left(29\right)$

In the formula: H is the aircraft flight height, and unit is Km.

The mathematical model of density p is:

ρ＝1.225exp(-H/10.7) (30)

(2) calculate plume inlet pressure

A) set up air intake duct outlet pressure model

P _B ^*＝P _H(1+(k-1)Ma ²/2) ^(k/(k-1))σ _i (31)

Wherein: P _B ^*Be air intake duct outlet pressure, σ _iBe the total pressure recovery coefficient of air intake duct, generally get 0.97; K is the ideal gas index, value 1.4.

B) set up blower outlet cross section pressure model

P _K ^*＝P _B ^*·π _k ^* (32)

Wherein: P _k ^*Be blower outlet cross section pressure.

C) set up combustor exit cross section pressure

P _Γ ^*＝P _B ^*·σ _k·c (33)

Wherein: P _Γ ^*Be combustor exit cross section pressure, σ _KcBe the firing chamber total pressure recovery coefficient.

D) set up turbine outlet cross section pressure model

P _T ^*＝P _Γ ^*/π _T ^* (34)

Wherein: P _T ^*Be turbine outlet cross section pressure, π _T ^*For coefficient is compared in turbocharging.

E) set up the nozzle exit section pressure model

P _C ^*＝P _T ^*/π _c.kp ^*(35)

Wherein: P _C ^*Be nozzle exit section pressure, π _C.kp ^*Be pressure ratio, The ki value is 1.33.Nozzle exit pressure is equivalent to the import cross section pressure of plume, so according to steps A)-E) obtain plume porch pressure values.

(3) calculate inlet air flow speed

Plume inlet air flow speed and combustion gas be the exhaust velocity c after the complete expansion in jet pipe _cIdentical.

(4) calculate plume length

L ^*＝[F/(ρV _m) ²] ^1/2 (36)

Wherein, F is a thrust, ρ is an environmental gas density, V _mBe airplane motion speed, T _c ^*Be temperature in nozzle, q (λ _c) be the engine flow flow function, f (λ _c) be the engine impulsive function, m is a flow, q _TFlow function value for turbine.

(5) calculate the plume temperature field

Obtain to set up the required initial parameter in plume temperature field according to step (1)～step (4), i.e. plume inlet pressure, atmospheric pressure, atmospheric density, inlet initial temperature, inlet air flow speed, plume length; Then according to present state of flight, set up dynamic plume temperature field through the modeling and simulation method of airbound target wake flame infrared radiation signal aloft, calculate the infrared radiation brightness N of plume according to formula (1) _Plume

(6) set up plume area model

The area model of direction of visual lines plume is:

Wherein, R ₁Be wake flame maximum radius, R ₀Be the spout radius, R is a body radius, and l is the distance of body maximum radius and spout, L _FlareBe the length of plume,

Acquisition is in the board a plane infrared intensity of plume of direction of visual lines, and plume infrared intensity model is:

I _plume＝N _plume·A _flare (38)

Step 5: obtain overall aircraft zero distance infrared intensity value

To step 4, can obtain the integral radiation intensity level I that boards a plane at direction of visual lines through step 1 at last _Total:

I _total＝I _skin+I _nozzle+I _plume (39)

Step 6: obtain atmospheric transmittance

Key step is:

1. geographic model is set

Geographic model is divided into: horizontal atmospheric parameter, tropical atmosphere, middle latitude summer, winter atmosphere, polar region summer, winter atmosphere and United States standard atmosphere, according to user's request, select one of them geographic model.

2. gasoloid is set

Aerosol model is divided into: do not consider gasoloid; The rural area model, acquiescence 5Km; The cities and towns model, acquiescence 5Km; The sea level model is specified by wind speed and relative humidity; The sea level model, acquiescence 23Km; The troposphere, acquiescence 50Km; Greasy weather 0.2Km; Greasy weather 0.5Km according to user's request, selects one of them aerosol model.

3. the sexual intercourse pattern is set

The sexual intercourse pattern comprises: cloudless or rain; The heap cloud; Altostratus; Stratus; Cumulus; Nimbostratus; Drizzle; Light rain; Moderate rain; Heavy rain; Heavy rain; User Defined; Cirrus, 64 microns accumulated ice particles of radius; Cirrus, 4 microns accumulated ice particles of radius; Cirrus, the NOAA standard; According to user's request, select one of them sexual intercourse pattern.

4. path mode is set

Path mode is divided into: slant path between horizontal route, both heights and vertical-path, according to user's request, select one of them path mode.

5. calculate infrared radiation atmospheric transmittance on the different-waveband in propagation in atmosphere

Step 7: the aircraft infrared intensity that obtains to arrive sensor side

The infrared intensity that aircraft arrives sensor is:

I＝I _total·τ _a (40)

Wherein: τ _aBe the mean transmissivity of aircraft submodel under current detecting band and meteorological condition.

The invention has the advantages that:

(1) improvement of aircraft skin temperature model

When aircraft skin is surveyed in far infrared, have very big contribution effect, the place of plane nose, the leading edge of a wing etc. and windage especially, temperature can be very high.In order to improve the temperature model of covering, among the present invention aspects such as the sun, terrestrial radiation, the outside heat radiation of body in pneumatic heat, the environment are integrated, the balance equation that the consideration various factors is set up temperature model provides temperature data for the aircraft infrared radiation.

(2) foundation of engine jet pipe model

Engine is the important infrared source of aircraft, sets up the engine temperature model and can important temperature data source be provided for infrared origin.In the middle of modeling in the past, ignored the influence of engine, so the temperature of final jet pipe and plume is that the user sets, and these data are to be difficult to obtain in the middle of real infrared counteraction.Not enough to this point among the present invention, the temperature model that will start is incorporated in the middle of the infrared radiation modeling, has improved the infrared radiation model of aircraft, and the infrared radiation signal in the emulation all depends on the current movement position of aircraft, attitude and velocity information.

(3) foundation of aircraft plume model parameter model

The mathematical model of plume has had research at present, yet the initial conditions of model is more, and a lot of parameters also can't be given in reality, must obtain through model.Among the present invention,,, set up the input parameter model of plume according to fluid mechanics, engine correlation theories knowledge to this demand.This improvement makes that plume model parameter information is to obtain according to current aircraft state, and is not only user's setting.

Description of drawings

Fig. 1 is a method flow diagram of the present invention;

Fig. 2 is each section temperature of engine;

Fig. 3 is 8Km, 0.9Ma, the infrared radiation result of 3～5um angle of sight direction;

Fig. 4 is 8Km, 0.9Ma, the infrared radiation result of 8～14um angle of sight direction;

Fig. 5 is 8Km, 1.5Ma, the infrared radiation result of 3～5um angle of sight direction;

Fig. 6 is 8Km, 1.5Ma, the infrared radiation result of 8～14um angle of sight direction;

Fig. 7 is 8Km, 150 degree, the infrared radiation result of the non-afterburning angle of sight direction of 3～5um;

Fig. 8 is 8Km, 150 degree, 3～5um, the infrared radiation result of afterburning angle of sight direction;

Fig. 9 is 8Km, 150 degree, 8～14um, the infrared radiation result of non-afterburning angle of sight direction;

Figure 10 is 8Km, 150 degree, 8～14um, the infrared radiation result of afterburning angle of sight direction;

Figure 11 is the distribution plan of atmospheric transmittance under DIFFERENT METEOROLOGICAL CONDITIONS;

Figure 12 is the 8Km height, 1.5Ma, and 3～5um is before and after the decay;

Figure 13 is the 8Km height, 1.5Ma, and 8～14um is before and after the decay.

Embodiment

Below in conjunction with accompanying drawing the present invention is elaborated.

A kind of aircraft infrared radiation of the present invention and atmospheric transmittance modeling method, flow process is as shown in Figure 1, comprises following step:

Step 1: the infrared intensity value of obtaining aircraft

Aircaft configuration is complicated, and it is divided into aircraft surfaces covering, jet pipe and three parts of plume, and each several part temperature under the different working state is different with radiation intensity, so in calculating the infrared intensity process, the independent temperature T of calculating each several part _iAccording to Planck law, calculating each parts of aircraft i is T in temperature then _iUnder radiance be N _i:

$N_i=\frac{1}{\mathrm{\&pi;}}{\&Integral;}_{{\mathrm{\&lambda;}}_1}^{{\mathrm{\&lambda;}}_2}\frac{{\mathrm{\&epsiv;}}_i\&CenterDot;c_1}{({\mathrm{\&lambda;}}^5\exp ({\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000278285500021.png,HSA00000278285500051.png"\; state="\{\{state\}\}">c</figure-callout>}}_2/\mathrm{\&lambda;}{T}_i)-1)}\mathrm{d\&lambda;}---\left(1\right)$

Wherein, N _iUnit is W/m ²Sr, promptly watt of/meter ²Sterad, ε _iFor being the emissivity of i part, λ ₁, λ ₂Be detecting band scope, c ₁Be first radiation constant, 3.71418 * 10 ⁸Wm ^-2μ m ⁴, c ₂Be second radiation constant, 1.4388 * 10 ⁴μ mK.λ is the wavelength variable, and unit is um.

Obtain the zero distance infrared intensity value I of direction of visual lines aircraft i part _iFor:

I _i＝N _iA _i (2)

Wherein: I _iUnit be W/Sr, promptly watt/sterad A _iBe swept area on the direction of visual lines, unit is m ²

Step 2: set up aircraft surfaces covering infrared intensity model

1) sets up aircraft ambient radiation model

Environment is influential to the aircraft surfaces radiation, and the present invention mainly sets up the environmental radiation model of solar radiation, the earth self radiation, sky radiation, four aspects of earth reflected solar radiation, is specially:

I: set up the solar radiation environmental model

If Q _iIntensity of solar radiation for arbitrary moment aircraft receives then obtains respectively:

For high-altitude target (approaching or outer space), the earth and sun distance are distant, think uniform when sunshine is directional light and intensity of solar radiation, and then the solar radiation environmental model is:

Q ₁＝α _iS ₀F _nA[1+0.33cos(360n/370)] (3)

Wherein: Q ₁Unit is W, α _iBe the absorptivity of object, span 0～1 generally gets 0.54; S ₀Be solar constant (being generally 1353W/Sr), be the exoatmosphere or the vertical lip-deep intensity of solar radiation of sunshine of average solar distance; F _nBe the solar radiation angle factor of object, span 0～1 generally gets 0.6; A is the equivalent area of aircraft reflection; N is the some day in 1 year, and scope is 0～365, in the present invention, gets 81 spring, gets 145 summer, gets 243 autumn, gets 334 winter.

For low latitude and terrain object, need to consider that sunray sees through the influence of atmosphere, then I _nBe the intensity of solar radiation behind the process atmosphere:

I _n＝S ₀[1+0.33cos(360n/370)]p ₂ ^m(W/m ²) (4)

Wherein: p ₂Be atmospheric transparency, m is an air quality, the m=2 that averages in the common engineering, p ₂=0.8.

The solar radiation environmental model is:

Q ₁＝α _iS ₀F _nAI _n(W) (5)

Ii: the solar radiation environmental model of setting up earth reflection

Earth surface and atmosphere are relevant to the distribution of the character on the reflection of sunlight and ground, cloud layer, and difference is very big, and high-altitude target is also obviously different with the reflected radiation that low target receives, and for high-altitude target, establishes Q ₂The intensity of solar radiation that the earth that receives for aircraft reflects, then the solar radiation environmental model of earth reflection is:

Q ₂＝α _iρ _ES ₀F _SEA (6)

Wherein: Q ₂Unit is W, F _SEBe earth radiation reflected angle factor, span is 0～1, and value is 0.7 among the present invention; ρ _EBe reflectivity,, can adopt the average reflectance 0.35 of the earth for aerial target.

For low target, only consider the reflecting part on the face of land, different terrestrial references is adopted different reflectivity, then the solar radiation environmental model of earth reflection is:

Q ₂＝o _iρ _EI _nF _SEA (7)

Iii: the infrared radiation that obtains the earth self

The infrared radiation of the earth comes from that part of energy of the solar radiation that earth surface absorbs, and supposes that the earth is a uniform heat radiation balanced body, and then everywhere caloradiance is identical.If infrared solar radiation intensity is E ₀, then:

E ₀＝(1-ρ _E)S ₀/4 (8)

Wherein: E ₀Unit is W/m ², ρ _EBe reflectivity, span is 0～1, and value 0.7 among the present invention.If Q ₃The earth caloradiance that receives for aircraft, then:

${\mathrm{<figure-callout\; id="3"\; label="Q"\; filenames="HSA00000278285500021.png"\; state="\{\{state\}\}">Q</figure-callout>}}_3={\mathrm{\&alpha;}}_i{E}_0{f}_{E_i}A---\left(9\right)$

Wherein: is the terrestrial radiation angle factor of aircraft; Scope is 0～1; Get 0.7 among the present invention, A is the aircraft reflective surface area.

Iv: obtain sky radiation

Sky radiation is:

$Q_{\mathrm{sky}}=(c+b\sqrt{e})\mathrm{\&sigma;}{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="HSA00000278285500021.png"\; state="\{\{state\}\}">T</figure-callout>}}^4=\mathrm{\&epsiv;\&sigma;}{T}^4---\left(10\right)$

Wherein: Q _SkyUnit is W, and c, b are the empirical parameter values, and span is 0～1, according to the test experience, gets 0.58,0.208 respectively, and e is water vapor pressure (hPa).

V: obtain aircraft ambient radiation model

According to step I-step I v, acquisition aircraft ambient radiation model is:

Q _i＝Q ₁+Q ₂+Q ₃+Q _sky (11)

2) set up pneumatic thermal model

The relative engine components of aircraft skin temperature are lower; Survey at 3～5 mu m wavebands, the infrared radiation contribution is smaller, but when airplane motion speed is higher; Because pneumatic heat and the influence of engine endogenous pyrogen; The surface temperature temperature rise is bigger, so when gauging surface covering temperature, consider heat transfer problem equilibrium establishment equation.When high velocity air flows to wing or fuselage, be compressed at the object head, flow velocity reduces to zero at the place, stationary point, and temperature is increased to stagnation temperature.Consider that body conducts heat, the wall surface temperature of adiabatic wall is recovery temperature T _γ:

$T_{\mathrm{\&gamma;}}=T_{\&infin;}(1+\mathrm{\&sigma;}\frac{\mathrm{\&gamma;}-1}{2}{\mathrm{Ma}}^2)---\left(12\right)$

Wherein: T _∞Be the place ahead temperature of incoming flow, it is generally acknowledged with environment temperature to equate.γ is a gas adiabatic exponent, and ideal gas gets 1.4.σ is a coefficient of restitution, and general laminar flow gets 0.85, and turbulent flow gets 0.88, and Ma is the airplane motion Mach number.

Then, set up pneumatic thermal model according to the method in the computing machine infrared imaging emulation of high-speed moving object.

3) equilibrium establishment equation

In the present invention, take all factors into consideration the influence to the aircraft surfaces covering of physical environment radiation, endogenous pyrogen and pneumatic heat, as wing or body boundary temperature, recovery temperature is carried out thermally equilibrated initial temperature value as the aircraft surfaces covering with stagnation temperature.The equilibrium establishment equation is:

Q _i+q _o＝q _abs+q _rad+q _cdi+q _cv (13)

Wherein: Q _iBe the energy of ambient atmosphere environmental radiation, q _oSend and arrive the heat of object inside surface by the engine endogenous pyrogen, by the decision of engine work at present state, q _RadFor being radiated the heat in the environment, q _AbsBe the heat that surfacing absorbs, q _CdiBe the heat of external world's conduction, q _CvBe convection heat transfer.

Adopt Newton iteration method to find the solution nonlinear equation (13), calculate temperature after the covering balance, then according to the radiance value N of formula (1) gauging surface covering _Skin

4) set up aircraft surfaces covering area model

At direction of visual lines aircraft surfaces covering area model be:

$A_{\mathrm{fus}}=\left\{\begin{array}{cc}{A}_{\mathrm{hd}}\cos {\mathrm{\&theta;}}_{\mathrm{asp}}+(A_{\mathrm{bd}}+2a_{\mathrm{wng}})\sin {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="0"\; label="asp"\; filenames="HSA00000278285500022.png,HSA00000278285500023.png"\; state="\{\{state\}\}">asp</figure-callout>}}& 0\&le;{\mathrm{\&theta;}}_{\mathrm{asp}}<90\\ (A_{\mathrm{bd}}+2A_{\mathrm{wng}})\sin {\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="90"\; label="asp"\; filenames="HSA00000278285500053.png"\; state="\{\{state\}\}">asp</figure-callout>}}& 90\&le;{\mathrm{\&theta;}}_{\mathrm{asp}}<180\end{array}\right.---\left(14\right)$

Wherein, A _Hd, A _Bd, A _WngRepresent the area of head, fuselage, wing respectively, θ _Asp=arc cos (cos θ _AzCos θ _El), θ _AzBe the position angle on the line of observation, θ _ElBe the angle of pitch on the line of observation, A _Hd=π R ², A _Bd=2RL _bR is a body radius, L _bLength for fuselage.

5) obtain aircraft surfaces covering radiation intensity model

According to step 1)-step 4), then aircraft surfaces covering infrared intensity model is:

I _skin＝N _skin·A _fus (15)

Step 3: set up engine jet pipe infrared intensity model

For verification model, adopt the turbojet of a certain model among the present invention, carry out infrared modeling according to engine working process principle and composition structure.The different conditions of aircraft flight is different to a few partial cross section temperature effects of engine intake, pneumatic plant, firing chamber, turbine and after-burner, finally can influence the temperature of spout and plume.The different model engine temperature is different under identical flying height and speed conditions; Mainly by each level work efficient of engine and two parameter determining of pressure ratio, the user can be provided with each these two parameter of level according to self engine model demand and set up corresponding temperature model.Each grade of engine outlet temperature is analyzed.The specific heats of gases are than three kinds of values are generally arranged in the pneumatic function table: (1.4,1.33,1.25).Cold parts process for engine adopts k=1.4, and the process of calculating in turbojet engine turbine and the jet pipe adopts k _i=1.33, the expansion process of calculating jet pipe under the afterburning state then adopts k _i=1.25.

A) set up air intake duct outlet temperature model

In inlet device, air intake duct outlet temperature T _B ^*Irrelevant with the loss size in adiabatic stagnant air temperature and the air intake duct, only depend on airplane motion Mach number Ma and environment temperature T _Amb, then air intake duct outlet temperature model is:

${T_B}^{*}=T_{\mathrm{amb}}(1+\frac{k-1}{2}{\mathrm{Ma}}^2)---\left(16\right)$

In the formula: the k value is 1.4.Environment temperature T _AmbDetermine by the current flight height.Because the step-up ratio of air intake duct is relevant with current flight speed, and plays an important role to chamber temperature, according to the pressure ratio π of computes air intake duct ^* _B:

${{\mathrm{\&pi;}}^{*}}_B={\mathrm{\&sigma;}}_i{(1+\frac{k-1}{2}{\mathrm{Ma}}^2)}^{(k-1/k)}---\left(17\right)$

Wherein: σ _iBe the total pressure recovery coefficient of air intake duct, generally get 0.97.

B) set up blower outlet section temperature model

In order to confirm blower outlet section temperature T _κ ^*, must selected compressor efficiency η ^* _κ(usually in 0.82～0.86 scope) and pressure ratio π ^* _κ(optimal value gets 7～11) calculates, and then blower outlet section temperature model is:

${T_{\mathrm{\&kappa;}}}^{*}={T_B}^{*}(1+\frac{{{{\mathrm{\&pi;}}^{*}}_{\mathrm{\&kappa;}}}^{(k-1/k)}-1}{{{\mathrm{\&eta;}}^{*}}_{\mathrm{\&kappa;}}})---\left(18\right)$

C) set up combustor exit section temperature model and after-burner outlet temperature model

The firing chamber principle of work is complicated, regulates rule mostly from engineering test and generally be temperature given in design, in emulation this value obtain not too easy.Adopt the experience engineering method to obtain combustor exit section temperature T in the present invention _Γ ^*, then combustor exit section temperature model is:

${T_{\mathrm{\&Gamma;}}}^{*}={T_{\mathrm{\&kappa;}}}^{*}+T_{\mathrm{amb}}({{{\mathrm{\&pi;}}^{*}}_{\mathrm{\&Gamma;}}}^{(k-1/k)}-\frac{e-1}{{{\mathrm{\&eta;}}^{*}}_{\mathrm{\&kappa;}}}-1)---\left(19\right)$

Wherein: e=a η ^* _κη ^* _T, η ^* _TBe engine turbine efficient, a gets 1.02～1.04, firing chamber step-up ratio π ^* _Γ=π ^* _Bπ ^* _κThereby, can obtain the temperature of firing chamber.

If engine operation is at afterburning state, the after-burner outlet temperature is T _Φ ^*, then after-burner outlet temperature model is:

T _Φ ^*＝1.61T _Γ ^* (20)

D) set up the temperature model in turbine outlet cross section

${T_T}^{*}={T_{\mathrm{\&Gamma;}}}^{*}(1-(1-\frac{1}{{{{\mathrm{\&pi;}}^{*}}_T}^{(k_i-1/k_i)}}){{\mathrm{\&eta;}}^{*}}_T)---\left(21\right)$

Wherein: η _T ^*Be the turbine efficiency level, scope is 0～1, and value is 0.9～0.92 in the invention, π ^* _TBe turbine step-up ratio, K _iValue 1.25.

E) set up the temperature in nozzle model

Aircraft is under afterbunring chamber opening whether situation, and the spout temperature has very big difference.

Under non-afterburning state, the temperature in nozzle model is:

${T_c}^{*}={T_T}^{*}-\frac{k_i-1}{k_i{R}_i}\frac{{c_c}^2}{2}---\left(22\right)$

Wherein: c _cBe combustion gas exhaust velocity after the complete expansion in jet pipe, R _iBe gas law constant, get 289.3J/KgK.c _cObtain through following formula:

Wherein:

is the jet pipe velocity coefficient; Value is 0.97～0.98, and

is used for estimating the loss of air-flow at jet pipe.

Under afterburning state, the temperature in nozzle model is:

${T_c}^{*}={T_{\mathrm{\&Phi;}}}^{*}-\frac{k_i-1}{k_i{R}_i}\frac{{c_c}^2}{2}---\left(24\right)$

Wherein, c _cObtain through following formula:

According to the duty of aircraft current flight, select different models to obtain the nozzle outlet temperature, bring temperature into formula (1), calculate the infrared radiation brightness value N of jet pipe _Nozzle

F) set up nozzle exit plane product module type

In order to calculate the radiation intensity at angle of sight direction jet pipe, then nozzle exit plane product module type is on direction of visual lines:

Wherein, R _HsBe the spout radius.

G) obtain engine jet pipe infrared radiation model

Through step a)～step f), in emulation under the flying height and speed conditions of known aircraft, resolve the infrared radiation model of jet pipe according to current state, calculate at the board a plane infrared intensity I of jet pipe of direction of visual lines _Nozzle, engine jet pipe infrared radiation model is:

I _nozzle＝N _nozzle·A _hs (27)

Step 4: set up plume infrared intensity model

The plume temperature is relevant with the nozzle temperature, is setting up on the nozzle temperature model basis, and plume temperature in computing method are:

T _f＝T _c ^*·(P ₂/P ₁) ^(γ-1)/γ (28)

In engineering, use T _f=0.85T _c ^*Replace formula (28).

The plume principle is complicated, yet existing model plume suction parameter all is to calculate under the stable condition, does not consider that aircraft is operated in different flying heights, duty and speed, and its flame profile (maximum radius and length) is different.If solve and resolve current infrared radiation problem through state of flight, need set up the initiation parameter model, the present invention satisfies the emulation demand through setting up dynamic plume model.

In order before setting up the temperature field, to obtain the required initiation parameter of models for temperature field, set up the mathematical model of suction parameter through introducing engine principles.

(1) at first establishes atmospheric pressure P under the current flight height _HWith the mathematical model of density p, atmospheric pressure P _HMathematical model be:

$P_H=\left\{\begin{array}{cc}1.0133\&times;{10}^5{(1-H/44.308)}^{5.2553}& 0\&le;H<11\mathrm{Km}\\ 0.277\&times;{10}^5{e}^{\frac{11-H}{6.338}}& 11\mathrm{Km}\&le;H\&le;20\mathrm{Km}\end{array}\right.---\left(29\right)$

In the formula: H is the aircraft flight height, and unit is Km.The mathematical model of density p is:

ρ＝1.225exp(-H/10.7) (30)

(2) calculate plume inlet pressure

A) set up air intake duct outlet pressure model

P _B ^*＝P _H(1+(k-1)Ma ²/2) ^(k/(k-1))σ _i (31)

Wherein: P _B ^*Be air intake duct outlet pressure, σ _iBe the total pressure recovery coefficient of air intake duct, generally get 0.97.K is the ideal gas index, value 1.4, and Ma is the airplane motion Mach number.

B) set up blower outlet cross section pressure model

P _K ^*＝P _B ^*·π _k ^* (32)

Wherein: P _K ^*Be blower outlet cross section pressure, π _k ^*Be pressure ratio, optimal value gets 7～11.

C) set up combustor exit cross section pressure

P _Γ ^*＝P _B ^*·σ _k·c (33)

Wherein: P _Γ ^*Be combustor exit cross section pressure, σ _KcBe the firing chamber total pressure recovery coefficient, general value 0.95～0.96.

D) set up turbine outlet cross section pressure model

P _T ^*＝P _Γ ^*/π _T ^* (34)

Wherein: P _T ^*Be turbine outlet cross section pressure, π _T ^*For turbocharging than coefficient, value 2.33.

E) set up the nozzle exit section pressure model

P _C ^*＝P _T ^*/π _c.kp ^* (35)

Wherein: P _C ^*Be nozzle exit section pressure, π _C.kp ^*Be pressure ratio,

Ki is value 1.33 here.Nozzle exit pressure is equivalent to the import cross section pressure of plume.So according to steps A)-E) obtain plume porch pressure values.

(3) calculate inlet air flow speed

Plume inlet air flow speed and nozzle exit c _c(combustion gas is the exhaust velocity after the complete expansion in jet pipe) is equal to.

(4) calculate plume length

L ^*＝[F/(ρV _m) ²] ^1/2 (36)

Wherein, F is a thrust, ρ is an environmental gas density, V _mBe target aircraft movement velocity, T _c ^*Be temperature in nozzle, q (λ _c) be flow function, f (λ _c) be impulsive function.What adopt on the hypothesis aircraft among the present invention is contracting nozzle, λ _cBe velocity coefficient, get 0.97, q _TFor the flow function value of turbine, get 0.0499 in the invention, m represents flow, at k _iIn the time of=1.25, get 0.0385, q (λ _c)=0.9999, f (λ _c)=1.248.

(5) calculate the plume temperature field

Obtain to set up the required initial parameter in plume temperature field according to step (1)～step (4), i.e. plume inlet pressure, atmospheric pressure, atmospheric density, inlet initial temperature, inlet air flow speed, plume length.Then according to present state of flight, set up dynamic plume temperature field through the modeling and simulation method of airbound target wake flame radiation signal aloft, calculate the infrared radiation brightness N of plume according to formula (1) _Plume

(6) set up plume area model

In order to calculate infrared intensity, need to establish the long-pending computation model of direction of visual lines edged surface at the direction of visual lines angle.The area model of direction of visual lines plume is:

Wherein, R ₁Be wake flame maximum radius, R ₀Be the spout radius, R is a body radius, and l is the distance of body maximum radius and spout, L _FlareBe the length of plume,

Acquisition is in the board a plane infrared intensity of plume of direction of visual lines, and plume infrared intensity model is:

I _plume＝N _plume·A _flare (38)

Step 5: obtain overall aircraft zero distance infrared intensity value

Aircraft infrared intensity model method through step 1-step 4 is set up can obtain the integral radiation intensity level I that boards a plane at direction of visual lines at last _Total:

I _total＝I _skin+I _nozzle+I _plume (39)

Step 6: obtain atmospheric transmittance

Adopt Modtran4 to carry out the calculating of atmospheric transmittance among the present invention.Key step is:

1. geographic model is set

Geographic model is divided into: horizontal atmospheric parameter, tropical atmosphere, middle latitude summer, winter atmosphere, polar region summer, winter atmosphere and United States standard atmosphere etc.Select U.S.'s mode standard atmosphere in 1976 among the present invention.

2. gasoloid is set

Aerosol model is divided into: do not consider gasoloid; The rural area model, acquiescence 5Km; The cities and towns model, acquiescence 5Km; The sea level model is specified by wind speed and relative humidity; The sea level model, acquiescence 23Km; The troposphere, acquiescence 50Km; Greasy weather 0.2Km; Greasy weather 0.5Km can select for several kinds.The defeated people of gasoloid pattern rural area type among the present invention, visibility is 23Km.

3. the sexual intercourse pattern is set

The sexual intercourse pattern comprises: cloudless or rain; The heap cloud; Altostratus; Stratus; Cumulus; Nimbostratus; Drizzle; Light rain; Moderate rain; Heavy rain; Heavy rain; User Defined; Cirrus, 64 microns accumulated ice particles of radius; Cirrus, 4 microns accumulated ice particles of radius; Cirrus, several kinds of moulds of NOAA standard.Select cloudless in the present invention or the rain pattern.

4. path mode is set

Path mode is divided into: slant path between horizontal route, both heights and vertical-path, select slant path among the present invention.

5. calculate infrared radiation atmospheric transmittance on the different-waveband in propagation in atmosphere

Through Modtran4 above pattern is set and just can calculates infrared radiation atmospheric transmittance on the different-waveband in propagation in atmosphere, compare, proved the availability of current model through the atmospheric transmittance and the prior art of emulation on obstructed wavelength.

Step 7: the aircraft infrared intensity that obtains to arrive sensor side

The last mean transmissivity that when the wavelength condition of current detection is respectively 3～5um and 8～14um, calculates combines the result with aircraft infrared radiation model, the infrared intensity of calculating aircraft arrival sensor is:

I＝I _total·τ _a (40)

Wherein: τ _aBe the mean transmissivity of aircraft submodel under current detecting band and meteorological condition.

Embodiment:

The present invention provides infrared radiation signal for platforms such as the generation of aircraft IR Scene, infrared acquisition, target seeker modelings.

Adopt and above-mentionedly set up aircraft infrared radiation realistic model with heat transfer principle,, through the VS2005 programming tool aircraft infrared radiation is built emulation platform and carry out emulation experiment some parameters employing empirical parameter values based on engine is theoretical.Experimental procedure is following:

Step1: programming realizes formula (1), and parameter is provided with function interface, returns the infrared radiation brightness value.Interface input detecting band information: 3～5um/8～14um, the angle of pitch of observation and position angle.

Step2: aircraft area model is set.The formal parameter that mainly comprises aircraft: length of aircraft, plane nose diameter, aircraft wing area etc.Calculate the board a plane area of covering, jet pipe and plume of angle of sight direction according to the angle of sight.

Step3: the required parameter configuration of input aircraft environment radiation model, concrete value provides in the model of setting up.Set environmental parameter and carry out resolving of environmental radiation model.

Step4: input aircraft surfaces covering model information needed mainly comprises aircraft initial position, attitude information, afterburning and non-afterburning State Selection.Surperficial covering emissivity is set then, value 0.9.The covering model is resolved, obtain the infrared intensity of covering on the sight angle direction.

Step5: jet pipe model desired parameters is set, mainly comprises each grade of engine pressure ratio, work efficiency, each parameter value provides in model.Resolve the engine jet pipe model, obtain in the infrared intensity that realizes the angle direction jet pipe.

Step6: resolve plume parameter model and plume models for temperature field, calculate the infrared intensity of plume then.

Step7: aircraft is set to the Modtran4 parameter configuration between the sensor, calculates atmospheric transmittance.Obtain to arrive the value of sensor side aircraft infrared intensity according to formula (40).

Step8: change the band class information of surveying and repeat Step2-Step7, obtain simulation result.

Can know by the experiment simulation result; As shown in Figure 2, each section temperature of engine and flying height and Mach number are closely related, when assigned altitute is 8Km; Under the non-afterburning state of 0.9Ma; The highest nozzle hole temperature of chamber temperature, but under the afterburning state of 1.5Ma, the after-burner after the turbine can make the temperature of spout and plume higher.So aircraft is when high-speed motion, engine is very big to the influence of infrared radiation.Simultaneously; The experimental data that obtains meets engine correlation experience data; The engine temperature data that obtain through model have solved and can only set the defective of carrying out infrared radiation calculating under jet pipe, the plume temperature in, and the model of simplifying can satisfy emulation demand in time.

As can be seen from Figure 3, in 3～5 mum wavelength scopes, aircraft is operated in 0.9Ma, when the less and forward direction of covering radiation is surveyed the nozzle hole radiation inoperative, so this moment, the plume contribution was maximum.But in surveying, the nozzle radiation intensity is bigger, becomes the main source of detection in the back.

As can be seen from Figure 4; At 8～14 mu m wavebands; Aircraft is operated in 0.9Ma; Because plume is that selective gas radiation and radiation wave band mainly concentrate on 4.1～4.2 μ m and 4.3～4.5 mu m wavebands, so infrared radiation is 0 in this wave band, and covering becomes the main source radiation of this wave band.

As can be seen from Figure 5, in 3～5 mum wavelength scopes, aircraft is operated in the afterburning state of 1.5Ma; The jet pipe radiation intensity increases 30 times approximately, and plume increases near 100 times, and smaller to the covering influence; So engine is when augmented operation, plume is very important detection source.

As can be seen from Figure 6, at 8～14 mu m wavebands, aircraft is operated in the afterburning state of 1.5Ma, and covering and jet pipe radiation increase, but it is less to compare 3～5 mu m waveband amplitudes of variation.

As can be seen from Figure 7, in 3～5 mum wavelength scopes, if the detector angle of sight is constant; Change the flight Ma of aircraft, and aircraft flight do not open after-burner in the sustained height and the course of work, along with the rising of Mach number; In 0～1Ma scope; The radiation variation of covering, jet pipe and plume is less, but after Ma was greater than 1, each several part radiation variation scope was bigger.

As can be seen from Figure 8; In 3～5 mum wavelength scopes,, change the flight Ma of aircraft if the detector angle of sight is constant; And aircraft flight is opened after-burner when Ma is 1.2 in the sustained height and the course of work, and then the total infrared intensity of aircraft can great change.

As can be seen from Figure 9, in 8～14 mum wavelength scopes, if the detector angle of sight is constant, change the flight Ma of aircraft, and aircraft flight do not open after-burner in the sustained height and the course of work, Changing Pattern is identical with Fig. 7.

As can be seen from Figure 10, in 8～14 mum wavelength scopes, if the detector angle of sight is constant, change the flight Ma of aircraft, and aircraft flight opens after-burner in the sustained height and the course of work when Ma is 1.2, Changing Pattern is identical with Figure 10.

As can be seen from Figure 11, when atmospheric visibility distance is 2000 meters and 4000 meters respectively, low visibility, atmospheric transmittance is little, and the high atmospheric transmittance of visibility is big.And, along with the transmitance of wavelength change distributes and actual conditions meet.

As can be seen from Figure 12, in 3～5um stage, the infrared intensity of aircraft is after propagation in atmosphere, and infrared intensity decays.

As can be seen from Figure 13, in 8～14um stage, the infrared intensity of aircraft is after propagation in atmosphere, and infrared intensity decays, but because the difference of detecting band, the degree of the infrared intensity value decay of aircraft is different with Figure 12.

From above conclusion, can find out; The aircraft infrared simulation model of setting up; Can the calculating real-time state of flight the get off the plane zero distance infrared radiation of covering and engine; First engineering engine temperature model is applied in the infrared radiation modeling, has changed in the past the deficiency of calculating infrared radiation through given aircraft each several part temperature setting under the flying condition.The logical at last atmospheric attenuation model that Modtran4 is set up has combined to calculate the infrared radiation value after the atmospheric attenuation with the infrared zero distance radiation of aircraft model.With the flight status is that the realistic model of importing more can satisfy the analogue system requirement.

Claims (9)

1. aircraft infrared radiation and atmospheric transmittance modeling method is characterized in that, comprise following step:

Step 1: the infrared intensity value of obtaining aircraft;

Aircraft is divided into aircraft surfaces covering, jet pipe and three parts of plume, the independent temperature T of calculating each several part _i, calculating i parts of aircraft then is T in temperature _iUnder radiance be N _i:

Wherein, N _iUnit is W/m ²Sr, promptly watt of/meter ²Sterad, ε _iFor being the emissivity of i part, λ ₁, λ ₂Be detecting band scope, c ₁Be first radiation constant, 3.71418 * 10 ⁸Wm ^-2μ m ⁴, c ₂Be second radiation constant, 1.4388 * 10 ⁴μ mK, λ are the wavelength variable, and unit is um;

Obtain the zero distance infrared intensity value I of direction of visual lines aircraft i part _iFor:

I _i＝N _iA _i (2)

Wherein: I _iUnit be W/Sr, A _iBe swept area on the direction of visual lines, unit is m ²

Step 2: set up aircraft surfaces covering infrared intensity model;

1) sets up aircraft ambient radiation model;

Set up the ambient radiation model of solar radiation, the earth self radiation, sky radiation, four aspects of earth reflected solar radiation, finally obtain aircraft ambient radiation model; Be specially:

I: set up the solar radiation environmental model;

If Q _iIntensity of solar radiation for arbitrary moment aircraft receives then obtains respectively:

For high-altitude target, think uniform when sunshine is directional light and intensity of solar radiation, then the solar radiation environmental model is:

Q ₁＝α _iS ₀F _nA[1+0.33cos(360n/370)] (31)

Wherein: Q ₁Unit is W, α _iBe the absorptivity of object, span 0～1; S ₀Be solar constant, be the exoatmosphere or the vertical lip-deep intensity of solar radiation of sunshine of average solar distance; F _nBe the solar radiation angle factor of object, span 0～1; A is the equivalent area of aircraft reflection; The span of n is 0～365;

For low latitude and terrain object, then pass through the intensity of solar radiation I behind the atmosphere _nFor:

I _n＝S ₀[1+0.33cos(360n/370)]p ₂ ^m(W/m ²) (32)

Wherein: p ₂Be atmospheric transparency, m is an air quality;

The solar radiation environmental model is:

Q ₁＝α _iS ₀F _nAI _n(W) (33)

Ii: the solar radiation environmental model of setting up earth reflection;

For high-altitude target, establish Q ₂The intensity of solar radiation that the earth that receives for aircraft reflects, then the solar radiation environmental model of earth reflection is:

Q ₂＝α _iρ _ES ₀F _SEA (34)

Wherein: Q ₂Unit is W, F _SEBe earth radiation reflected angle factor, span is 0～1; ρ _EBe reflectivity;

For low target, then the solar radiation environmental model of earth reflection is:

Q ₂＝α _iρ _EI _nF _SEA (35)

Iii: the infrared radiation that obtains the earth self;

Suppose that the earth is a uniform heat radiation balanced body, then everywhere caloradiance is identical; If infrared solar radiation intensity is E ₀, then:

E ₀＝(1-ρ _E)S ₀/4 (36)

Wherein: E ₀Unit is W/m ², ρ _EBe reflectivity; If Q ₃The earth caloradiance that receives for aircraft, then:

Wherein:

is the terrestrial radiation angle factor of aircraft; Scope is 0～1, and A is the aircraft reflective surface area;

Iv: obtain sky radiation;

Sky radiation is:

Wherein: Q _SkyUnit is W, and c, b are the empirical parameter values, and value is 0～1, and e is a water vapor pressure, and unit is hPa, and σ representes the blackbody radiation constant, and value is 5.67 * 10-8W/m ²K ⁴, T representes sky temperature;

V: obtain aircraft ambient radiation model;

According to step I-step I v, acquisition aircraft ambient radiation model is:

Q _i＝Q ₁+Q ₂+Q ₃+Q _sky (39)

2) set up pneumatic thermal model;

The wall surface temperature of adiabatic wall is recovery temperature T _γ:

Wherein: T _∞Be the place ahead temperature of incoming flow, equate with environment temperature; γ is a gas adiabatic exponent; σ is a coefficient of restitution; Ma is the airplane motion Mach number;

Then, set up pneumatic thermal model according to the method in the computing machine infrared imaging emulation of high-speed moving object;

3) equilibrium establishment equation;

Balance equation is:

Q _i+q _o＝q _abs+q _rad+q _cdi+q _cv (4)

Wherein: Q _iBe the energy of ambient atmosphere environmental radiation, q _oSend and arrive the heat of object inside surface by the engine endogenous pyrogen, by the decision of engine work at present state, q _RadFor being radiated the heat in the environment, q _AbsBe the heat that surfacing absorbs, q _CdiBe the heat of external world's conduction, q _CvBe convection heat transfer;

Adopt Newton iteration method to find the solution nonlinear equation (4), calculate temperature after the covering balance, then according to the radiance value N of formula (1) gauging surface covering _Skin

4) set up aircraft surfaces covering area model;

At direction of visual lines aircraft surfaces covering area model be:

Wherein, A _Hd, A _Bd, A _WngRepresent the area of head, fuselage, wing respectively, θ _Asp=arc cos (cos θ _AzCos θ _El), θ _AzBe the position angle on the line of observation, θ _ElBe the angle of pitch on the line of observation, A _Hd=π R ², A _Bd=2RL _bR is a body radius, L _bLength for fuselage;

5) obtain aircraft surfaces covering radiation intensity model;

According to step 1)-step 4), then aircraft surfaces covering infrared intensity model is:

I _skin＝N _skin·A _fus (6)

Step 3: set up engine jet pipe infrared intensity model;

Be specially:

A) set up air intake duct outlet temperature model;

In the formula: T _B ^*Be air intake duct outlet temperature, k is a specific heats of gases ratios, and value is 1.4, and Ma is the airplane motion Mach number, T _AmbBe environment temperature, determine by the current flight height;

The pressure ratio π of air intake duct ^* _BFor:

Wherein: σ _iTotal pressure recovery coefficient for air intake duct;

B) set up blower outlet section temperature model;

Wherein: T _κ ^*Be blower outlet section temperature, η ^* _κBe compressor efficiency, π ^* _κBe pressure ratio;

C) set up combustor exit section temperature model and after-burner outlet temperature model;

Non-afterburning state lower combustion chamber outlet temperature model is:

Wherein: T _Γ ^*Be the combustor exit section temperature, e=a η ^* _κη ^* _T, η ^* _TBe engine turbine efficient, a value is 1.02～1.04, firing chamber step-up ratio π ^* _Γ=π ^* _Bπ ^* _κ

If engine operation is at afterburning state, the after-burner outlet temperature is T _Φ ^*, then after-burner outlet temperature model is:

T _Φ ^*＝1.61T _Γ ^* (11)

D) set up the temperature model in turbine outlet cross section;

Wherein: η _T ^*Be the turbine efficiency level, value is 0～1, π ^* _TBe turbine step-up ratio, k _iBe specific heats of gases ratio, value 1.25;

E) set up the temperature in nozzle model;

Aircraft is under non-afterburning state, and the temperature in nozzle model is:

Wherein: c _cBe combustion gas exhaust velocity after the complete expansion in jet pipe, R _iBe gas law constant, get 289.3J/KgK; c _cObtain through following formula:

Wherein: is the jet pipe velocity coefficient, and

is used for estimating the loss of air-flow at jet pipe;

Aircraft is under afterburning state, and the temperature in nozzle model is:

Wherein, c _cObtain through following formula:

According to the duty of aircraft current flight, select different models to obtain the nozzle outlet temperature, bring temperature into formula (1), calculate the infrared radiation brightness value N of jet pipe _Nozzle

F) set up nozzle exit plane product module type;

Nozzle exit plane product module type is on direction of visual lines:

Wherein, R _HsBe the spout radius;

G) obtain engine jet pipe infrared radiation model;

Through step a)～step f), engine jet pipe infrared radiation model is:

I _nozzle＝N _nozzle·A _hs (18)

Wherein, I _NozzleInfrared intensity for the jet pipe of boarding a plane at direction of visual lines;

Step 4: set up plume infrared intensity model;

Be specially:

(1) at first establishes atmospheric pressure P under the current flight height _HWith the mathematical model of density p, atmospheric pressure P _HMathematical model be:

In the formula: H is the aircraft flight height, and unit is Km;

The mathematical model of density p is:

ρ＝1.225exp(-H/10.7) (20)

(2) calculate plume inlet pressure;

A) set up air intake duct outlet pressure model;

P _B ^*＝P _H(1+(k-1)Ma ²/2) ^(k/(k-1))σ _i (21)

Wherein: P _B ^*Be air intake duct outlet pressure, σ _iBe the total pressure recovery coefficient of air intake duct, generally get 0.97; K is the ideal gas index, value 1.4, and Ma is the airplane motion Mach number;

B) set up blower outlet cross section pressure model;

P _K ^*＝P _B ^*·π _k ^* (22)

Wherein: P _K ^*Be blower outlet cross section pressure; π _k ^*Be pressure ratio;

C) set up combustor exit cross section pressure;

P _Γ ^*＝P _B ^*·σ _k·c (23)

Wherein: P _Γ ^*Be combustor exit cross section pressure, σ _KcBe the firing chamber total pressure recovery coefficient;

D) set up turbine outlet cross section pressure model;

P _T ^*＝P _Γ ^*/π _T ^* (24)

Wherein: P _T ^*Be turbine outlet cross section pressure, π _T ^*For coefficient is compared in turbocharging;

E) set up the nozzle exit section pressure model;

P _C ^*＝P _T ^*/π _c.kp ^* (25)

Wherein: P _C ^*Be nozzle exit section pressure, π _C.kp ^*Be pressure ratio,

k _iValue is 1.33;

Nozzle exit pressure is equivalent to the import cross section pressure of plume; So according to steps A)-E) obtain plume porch pressure values;

(3) calculate inlet air flow speed;

Plume inlet air flow speed and combustion gas be the exhaust velocity c after the complete expansion in jet pipe _cIdentical;

(4) calculate plume length;

L ^*＝[F/(ρV _m) ²] ^1/2 (26)

Wherein, F is a thrust,

ρ is an environmental gas density, V _mBe airplane motion speed, T _c ^*Be temperature in nozzle, q (λ _c) be the engine flow flow function, f (λ _c) be the engine impulsive function, m is a flow, q _TFlow function value for turbine;

(5) calculate the plume temperature field;

Obtain to set up the required initial parameter in plume temperature field according to step (1)～step (4), i.e. plume inlet pressure, atmospheric pressure, atmospheric density, inlet initial temperature, inlet air flow speed, plume length; Then according to present state of flight, set up dynamic plume temperature field through the modeling and simulation method of airbound target wake flame infrared radiation signal aloft, calculate the infrared radiation brightness N of plume according to formula (1) _Plume

(6) set up plume area model;

The area model of direction of visual lines plume is:

Wherein, R ₁Be wake flame maximum radius, R ₀Be the spout radius, R is a body radius, and l is the distance of body maximum radius and spout, L _FlareBe the length of plume,

Acquisition is in the board a plane infrared intensity of plume of direction of visual lines, and plume infrared intensity model is:

I _plume＝N _plume·A _flare (28)

Step 5: obtain overall aircraft zero distance infrared intensity value;

To step 4, can obtain the integral radiation intensity level I that boards a plane at direction of visual lines through step 1 at last _Total:

I _total＝I _skin+I _nozzle+I _plume (29)

Step 6: obtain atmospheric transmittance;

Key step is:

1. geographic model is set;

Geographic model is divided into: horizontal atmospheric parameter, tropical atmosphere, middle latitude summer, winter atmosphere, polar region summer, winter atmosphere and United States standard atmosphere, according to user's request, select one of them geographic model;

2. gasoloid is set;

Aerosol model is divided into: do not consider gasoloid; The rural area model, acquiescence 5Km; The cities and towns model, acquiescence 5Km; The sea level model is specified by wind speed and relative humidity; The sea level model, acquiescence 23Km; The troposphere, acquiescence 50Km; Greasy weather 0.2Km; Greasy weather 0.5Km according to user's request, selects one of them aerosol model;

3. the sexual intercourse pattern is set;

The sexual intercourse pattern comprises: cloudless or rain; The heap cloud; Altostratus; Stratus; Cumulus; Nimbostratus; Drizzle; Light rain; Moderate rain; Heavy rain; Heavy rain; User Defined; Cirrus, 64 microns accumulated ice particles of radius; Cirrus, 4 microns accumulated ice particles of radius; Cirrus, the NOAA standard; According to user's request, select one of them sexual intercourse pattern;

4. path mode is set;

Path mode is divided into: slant path between horizontal route, both heights and vertical-path, according to user's request, select one of them path mode;

5. calculate infrared radiation atmospheric transmittance on the different-waveband in propagation in atmosphere;

Step 7: the aircraft infrared intensity that obtains to arrive sensor side

The infrared intensity that aircraft arrives sensor is:

Wherein: τ _aBe the mean transmissivity of aircraft submodel under current detecting band and meteorological condition.

2. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, in the described step I, and the absorptivity α of object _iGet 0.54; Solar constant S ₀Get 1353W/Sr; The solar radiation angle factor F of object _nGet 0.6; The span of n is 0～365; Atmospheric transparency p ₂=0.8, air quality m=2.

3. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, in the described step I, n gets 81 in spring, gets 145 summer, gets 243 autumn, gets 334 winter.

4. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, described earth radiation reflected angle factor F _SEGet 0.7; Reflectivity ρ _EGet 0.35; The terrestrial radiation angle factor of aircraft

Get 0.7; C=0.58, b=0.208.

5. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, described step 2 2) in; When being ideal gas; Gas adiabatic exponent γ gets 1.4, and coefficient of restitution σ gets 0.85 during general laminar flow, and coefficient of restitution σ gets 0.88 during turbulent flow.

6. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, the total pressure recovery coefficient σ of air intake duct in the described step 3 _iGet 0.97; Compressor efficiency η ^* _κValue is 0.82～0.86; Pressure ratio π ^* _κValue is 7～11; The horizontal η of turbine efficiency _T ^*Value be 0.9～0.92; The jet pipe velocity coefficient

Value is 0.97～0.98.

7. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, total pressure recovery coefficient σ in firing chamber in the described step 4 _KcValue is 0.95～0.96; Turbocharging is than coefficient π _T ^*Value is 2.33.

8. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, in (4) of described step 4, what suppose to adopt on the aircraft is contracting nozzle, velocity coefficient λ _cGet 0.97, the flow function value q of turbine _TGet 0.0499, work as k _iIn the time of=1.25, flow m=0.0385, then q (λ _c)=0.9999, f (λ _c)=1.248.

9. aircraft infrared radiation according to claim 1 and atmospheric transmittance modeling method is characterized in that, in the described step 6, geographic model is selected United States standard atmosphere; Aerosol model is selected rural model, and visibility is 23Km; Cloudless or the rain of sexual intercourse model selection; Path mode is selected slant path.

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