CN105404722B - A kind of method analyzed projectile impact and Inerting Aircraft Fuel Tanks are influenced - Google Patents
A kind of method analyzed projectile impact and Inerting Aircraft Fuel Tanks are influenced Download PDFInfo
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- CN105404722B CN105404722B CN201510726235.3A CN201510726235A CN105404722B CN 105404722 B CN105404722 B CN 105404722B CN 201510726235 A CN201510726235 A CN 201510726235A CN 105404722 B CN105404722 B CN 105404722B
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Abstract
A kind of method analyzed projectile impact and influenced on Inerting Aircraft Fuel Tanks, is the amendment to existing Inerting Aircraft Fuel Tanks model：According to primary condition, calculate the motion state parameters after bullet breakdown oil tank wall, puncture the energy variation after oil tank wall to bullet again to analyze, it analyzes heat transfer of the bullet in fuel tank in motion process and calculates resulting fuel droplets evaporation and increased fuel-steam amount, calculate the amount that bullet penetrates the air that oil tank wall enters in the external environment brought into during fuel tank gas-phase space, finally according to above-mentioned analysis, existing inerting model is modified.The present invention can be used for influence of the change of bullet parameter and environmental parameter under analysis operational environment to gas-phase space gas concentration, and then determine whether fuel tank is flammable.
Description
Technical field
The present invention relates to aviation operational aircraft vulnerability design fields, specifically consider the fuel oil inerting of projectile impact
Analysis method.
Background technology
Airborne combat viability is that the ability of artificial hostile environment is evaded or born to aircraft, is divided into sensibility and vulnerability two
Big research field.Vulnerability is defined as operational aircraft under combat situation, bears the ability that artificial hostile environment threatens.It provides winged
As soon as the vulnerability of machine component is the important process in survivability Evaluation, it should give and consider early stage airplane design.It
Guideline is provided to effectively improve Aircraft Survivability, major design task is targetedly placed on the high component of vulnerability
On, so as to reach the design of the effectively optimizing of Aircraft Survivability.
Development of Aircraft Vulnerability is higher, then easier when catching a packet to be killed, and can more reduce the ability that aircraft completes task.Fly
Machine fuel tank is used for storing the dynamical system fuel oil to be consumed for maintaining aircraft flight, and military aircraft uses wing and fuselage more
Large area arrangement, thus the exposed area of fuel tank usually accounts for more than the 50% of full machine, is that vulnerability is highest on aircraft
One of component.When military aircraft is fought, it is more likely that can be hit, threaten be subject to the deterrents such as bullet or guided missile fragmentation
Object hits aircraft fuel tank and killing pattern is caused predominantly to burn and explode, and is the major reason for causing aircraft damage.
Fuel oil inerting technology is anti-flaming datonation-inhibition effective measures, by being passed through nitrogen-rich gas into fuel tank, makes fuel tank
Oxygen content is less than combustion limits so as to prevent burning.Fuel-tank inert gas technology at this stage is divided into washing fuel and gas phase is empty
Between rinse two kinds.Washing fuel is that inert gas is passed through in fuel oil by being mounted on the tiny jet pipe of tank bottoms, displacement combustion
The oxygen dissolved in oil, so as to reduce the concentration of the oxygen dissolved in fuel oil, then in flight course, the amount of precipitation of oxygen can be compared with
Small or be not precipitated, the oxygen concentration of gas-phase space will be maintained in a safe range in fuel tank.Gas-phase space douching technique
It is then that inert gas is directly passed through fuel tank gas-phase space to dilute the oxygen in original gas, gas phase sky is reduced so as to reach
Between oxygen concentration purpose.At present due to the battlefield surroundings residing for military aircraft, two kinds of technologies are used in combination mostly, with
Reduce the vulnerability of fuel tank to improve the survival ability of aircraft afield.
Inerting is influenced for penetrator, takes place mostly in military aircraft, therefore, the inerting related generally to herein is fuel oil
Washing.During washing fuel, nitrogen-rich gas are passed through by the jet pipe of fuel tank bottom in fuel oil, form a large amount of small gas
It steeps, with the nitrogen-rich gas in bubble there are concentration gradient, original equilibrium state is destroyed, is partly dissolved dissolved oxygen nitrogen in fuel oil
Oxygen is precipitated from fuel oil, as shown in Figure 1.Existing inerting analysis basic procedure as shown in left in Figure 2, illustrate by basic inerting
Figure is as follows.
The first step, fuel oil determines the flow of nitrogen-rich gas (NEA) each component as research object using in fuel tank.With △ t
For time step, when △ t are sufficiently small, it is believed that each component state parameter is kept constant within the time period.It is flowed into the △ t times
The quality of oxygen and nitrogen with flowing out fuel tank follows mass conservation law,
In formula, O represents oxygen, and N represents nitrogen, and subscript F represents Fuel, and the subscript U in Fig. 1 represents Ullage, and 1 represents △
At the first moment in the t periods, 2 represent the last moment.
Second step obtains initial time according to oxygen in fuel oil and nitrogen partial pressure and ostwald relations and the last moment fires
The amount O of the oxygen dissolved in oilF1And OF2With the amount N of nitrogenF1And NF2.Ostwald relational expressions are,
In formula, β is ostwald coefficients.
3rd step determines the amount for the oxygen and nitrogen being precipitated from fuel oil.Assuming that the gas being precipitated is reached with the gas dissolved
To balance, the equilibrium volume V that can be newly increased by equation for ideal gasesEExist such as with the quality and partial pressure of bubbing
Lower relation,
Formula (3) and formula (4) are substituted into formula (1) and (2), and the equilibrium volume V in The Ideal-Gas EquationEPhase
Deng can obtain the amount of precipitated oxygen and nitrogen.
4th step, using fuel tank gas-phase space as research object, determine gas-phase space oxygen and nitrogen discharge rate and
The partial pressure of each gas component under balance new afterwards.Assuming that the gas being precipitated in fuel oil is filled with the original gas mixing of gas-phase space
Point, mixed gas can be discharged according to respective molar ratio, discharge rate by the last moment stagnation pressure Pt2And fuel tank vent mouth pressure is true
It is fixed.Existing balance is in gas-phase space,
OU,mix=OU1+OF,OUT=OU2+OU,OUT (5)
NU,mix=NU1+NF,OUT=NU2+NU,OUT (6)
In formula, 1 represents the original state of gas-phase space, and 2 represent the state after discharge gas.The amount O of oxygen and nitrogenU1With
NU1And OU2And NU2It is determined by its partial pressure in gas-phase space.
The stagnation pressure of gas-phase space can be calculated by formula (7) after mixing, and oxygen, nitrogen are by respective molar fraction XO,mixWith
XN,mixProportional discharge, molar fraction is than being identical with intrinsic standoff ratio.
At the end of each time step, according to fuel tank gas-phase space gross pressure P at this timet2P is pressed with fuel-steamv2It can
The partial pressure of oxygen and nitrogen under new balance, such as following formula are obtained,
pOU2=pNU2(XO.mix/XN.mix) (9)
5th step, by the meltage N of the last moment nitrogen and oxygen that are calculated in second step in fuel oilF2And OF2, with
And ginseng of the partial pressure of the 4th each gas of gas-phase space under the new balance that obtains of step as the moment at the beginning of in next △ t periods
Number, the inerting for carrying out next round calculate.
In existing inerting experiment or analysis model, the most of non-operational environments of situation that are considered, existing inerting
Analyze basic procedure as shown in left in Figure 2.When military aircraft is fought, it is more likely that bullet or guided missile fragmentation can be subject to
The strike of deterrents is waited, when threat penetrates fuel tank and enters inner space, often heat is carried and outside air enters oil gas
Space.In this case whether oxygen concentration can be impacted, so that gas-phase space each component is in flammable range, be worth
It is analyzed.The present invention by consider deterrent puncture oil tank wall after speed and temperature variation, due to deterrent entrance and
Situations such as variation of heat exchange, gas-phase space gas mixture concentration between air, deterrent and the ambient enviroment brought into, shape
Into a kind of fuel oil inerting analysis method for considering deterrent and hitting, and to existing inerting model into amendment.Wang Mingming et al. in
2010-10-15 exists《Nanjing Aero-Space University's journal》It delivers《Aircraft fuel tank rinses and washing inerting Technical comparing point
Analysis》A kind of method for establishing fuel-tank inert gas model is proposed in one text, this method establishes washing fuel theoretical model, analysis
The process of washing fuel has obtained gas-phase space oxygen volumetric concentration in fuel tank by model and has changed with time relation,
But washing fuel of model when being only applicable to analysis without projectile impact, consider that projectile impact is empty to gas phase in fuel tank
Between oxygen concentration influence, and under battlefield surroundings, military aircraft is likely to be hit be subject to bullet.The analysis that the present invention provides
Method considers influence of the projectile impact to Inerting Aircraft Fuel Tanks, aircraft fuel tank gas-phase space when finally providing projectile impact
Oxygen concentration changes with time relation.
The content of the invention
In order to overcome limitation of the existing inerting model without considering deterrent shock fuel tank situation, the present invention proposes
A kind of method analyzed projectile impact and Inerting Aircraft Fuel Tanks are influenced.
The present invention's comprises the concrete steps that：
1. a kind of analyze the method that is influenced on Inerting Aircraft Fuel Tanks of projectile impact, which is characterized in that detailed process is：
Step 1：The residual velocity of projectile impact oil tank wall is calculated according to primary condition.
Assuming that blunt nosed bullet is incident perpendicular to target plate, the residue speed of bullet is determined using JTCG/ME residual velocity equations
Spend VrFor,
In formula, V be bullet stroke speed, unit m/s；V50For the bullet limit of bullet, unit m/s；T is target
Thickness, unit m；ρ be target material density, unit kg/m3；ApFor the exposed area of bullet, unit m2；M is bullet
Quality, unit kg；θ is the incident angle of bullet, and unit is °.
The ballistic limit refers to bullet just when penetrating target, i.e., bullet passes completely through the residue speed after oil tank wall
Spend for 0m/s when stroke speed；Namely Projectile Penetration target runs through incidence rate when probability is 50%.Ballistic limit can be by
Following formula obtains：
In formula, L is the perimeter of exposed area, and unit m, s are the shearing resistance of target plate material, unit Pa.
Step 2：Analyze the variation that bullet punctures energy after oil tank wall.
Ignore heat loss of the bullet during oil tank wall is punctured, the thermal energy of plastic work done conversion is deposited as the form of interior energy
Storage, i.e.,
Wherein, β turns hot coefficient for plastic work done, and Q is the interior energy of bullet, and △ E are the thermal energy that bullet is converted due to plastic work done.
In order to which the influence penetrated bullet to each gas component in fuel tank gas-phase space maximizes, if bullet punctures oil tank wall
The heat converted in the process has all passed to bullet, since the coefficient of thermal conductivity of bullet material is higher, therefore ignores inside bullet
Temperature gradient, if temperature is identical everywhere for bullet.
Step 3：Fuel oil liquid during analyzing heat transfer of the bullet in fuel tank in motion process and calculating heat transfer
Drop is evaporated and increased fuel-steam amount.
During bullet is through fuel tank gas-phase space, the flux of energy q " of heat transfer is determined by formula (13)：
Q "=h (T-T∞) (13)
In formula, T is bullet surface temperature；T∞The temperature of air-flow is generated for Projectile Motion；H is the heat transfer system of convective heat exchange
Number；The unit of the flux of energy q " of the heat transfer is W/m2。
Under the conditions of convective heat exchange, bullet heat transfer coefficient hconvIt is determined by cylinder heat transfer coefficient formula (14)：
In formula, k is the thermal conductivity factor of air or fuel oil, and Pr is Prandtl number, ReDIt is on the basis of length is D
Reynolds number.
Due to bullet, temperature is identical everywhere, therefore the variation of bullet its temperature in motion process in fuel tank passes through formula (15)
It determines：
In formula, c is the specific heat capacity of bullet material；AfFor the contact area of bullet and ambient enviroment,Be temperature at any time
Variable quantity.
If the heat that bullet transfers during the motion is completely used for the fuel droplets to suspend in evaporation gas-phase space, formed
Fuel-steam is gathered in fragmentation afterbody and is mixed with the air entered.The mass rate vaporization m " of liquid fueldropFor：
In formula, CfFor the specific heat capacity of fuel oil, TbFor the boiling point of fuel oil, T is the initial temperature of fuel oil, hqFor the evaporation of fuel oil
Heat.
Step 4：Calculate the amount that bullet penetrates the air brought into during fuel tank.
For bullet, the volume of air V in fuel tank is brought intoairFor：
Vair=Ap·s (17)
In formula, ApFor the exposed area of bullet, unit m2；S be bullet move distance, unit m.
Step 5：Existing inerting model is modified.
The air quality that bullet is brought into is Aair, then the new amount of oxygen O ' of gas-phase space in formula (7)U,mixIt needs to add and bring into
Air in oxygen amount, therefore：
The new nitrogen amount O ' of gas-phase space is determined by formula (19)U,mixIn nitrogen in the air brought into amount：
In formula, MairFor the molal weight of air, MN、MOThe respectively molal weight of nitrogen and oxygen.Consider fuel tank air inlet
When bullet bring portion of air into, formula (5), (6) become respectively,
OU,mix=OU1+OF,OUT+Oair=OU2+OU,OUT (20)
NU,mix=NU1+NF,OUT+Nair=NU2+NU,OUT (21)
In projectile strike, because the fuel-steam increment that the heat transfer of bullet is evaporated is in the partial pressure of gas-phase space
pvb, then fuel-steam new in formula (7), which divides, is
p′v1=pv1+pvb (22)
Then formula (7) becomes
Assuming that the fuel-steam formed due to projectile strike and the air brought into after original mix equilibrium state it is each
Component is sufficiently mixed again, thus the discharge ratio of mixed gas be new equilibrium state when molar ratio.
The present invention is the amendment to existing Inerting Aircraft Fuel Tanks model.First according to primary condition, calculate bullet and hit
Wear the motion state parameters after oil tank wall, such as the residual velocity of bullet, then bullet is punctured the energy variation after oil tank wall into
Row analysis, heat transfer of the analysis bullet in fuel tank in motion process simultaneously calculate resulting fuel droplets evaporation and increase
Fuel-steam amount, calculate bullet and penetrate oil tank wall and enter air in the external environment brought into during fuel tank gas-phase space
Amount, finally according to above-mentioned analysis, is modified existing inerting model.The present invention can be used for bullet under analysis operational environment to join
Influence of the change of number and environmental parameter to gas-phase space gas concentration, and then determine whether fuel tank is flammable.The present invention provides certain
The example of bullet single impact fuel tank verifies the correctness of analysis method, as shown in final result, bullet breakdown fuel tank
During wall thickness passes through fuel tank inside, the concentration of gas-phase space oxygen and fuel-steam changes as shown in Figure 4, Figure 5, oil gas
Concentration ratio brings portion of air into after changing as shown in fig. 6, entering due to bullet so that and oxygen concentration gradually increases, and with
The evaporation for being suspended in fuel droplets in gas-phase space, the fuel-steam amount of generation gradually increases, and oxygen concentration change continuously decreases,
But the fuel-steam amount that fuel droplets generate is less compared with air capacity is entered, so fuel-steam concentration can continuously decrease, because
Whether this can determine oil/gas concentration in the case of projectile strike in fuel tank in flammable shape according to the combustible concentration scope of fuel oil
State further provides reference for the design of fuel tank viability.
Description of the drawings
Attached drawing 1 is washing fuel process schematic in unit time step；
Attached drawing 2 is existing inerting analysis model and considers the inerting analysis model of projectile impact, in figure：Left side is existing
Washing fuel flow, to the amendment flow chart of model when right side is considers projectile strike；
Attached drawing 3 penetrates the schematic diagram that fuel tank enters air for fragmentation；In figure：1. gas-phase space；2. projectile strike；3. combustion
Oil；
Attached drawing 4 is gas-phase space oxygen concentration change curve, in figure：Solid line represents that gas-phase space oxygen is dense during projectile impact
The change curve of degree, dotted line indicate the change curve of gas-phase space oxygen concentration during no projectile impact；
Attached drawing 5 is gas-phase space fuel-steam concentration curve, in figure：Chain-dotted line represents gas-phase space during projectile impact
Fuel-steam concentration curve, dotted line indicate gas-phase space fuel-steam concentration curve during no projectile impact；
Attached drawing 6 is gas-phase space oil/gas concentration ratio change curve, in figure：Chain-dotted line represents that gas phase is empty during projectile impact
Between space oil/gas concentration ratio change curve, dotted line indicates during no projectile impact that the variation of gas-phase space oil/gas concentration ratio is bent
Line；
Attached drawing 7 is flow chart of the invention.
Specific embodiment
The present embodiment is so that bullet single impact is to the influence of gas concentration in fuel tank as an example, is illustrated proposed by the present invention
Projectile impact is to the impact analysis method of Inerting Aircraft Fuel Tanks.
Step 1：According to primary condition, the residual velocity of calculating projectile impact oil tank wall.
In the present embodiment, bullet is U.S. 12.7mm bore machine gun ball bullets, and the parameter of this bullet is as shown in table 1：
1 12.7mm machine gun bullet specifications parameters of table
| Type | Bore | Full bullet is long | It is complete to play quality | Bullet diameter | Bullet is long | Warhead mass | Bullet initial velocity |
| Ball | 12.7mm | 137.8mm | 116g | 12.98mm | 57.18mm | 46.01g | 858m/s |
Assuming that bullet velocity attenuation 200m/s when being met with fuel tanker, the flying speed of aircraft is 250m/s, bullet
The incident angle θ of flight and head-on crash, i.e. bullet is 0 ° in opposite directions for ball and aircraft, and relative velocity during projectile impact fuel tank is
900m/s.Fuel tanker is aluminum fuel tank, and specification is 1 × 1 × 0.5m, wall thickness 3mm.The shearing resistance of aluminium is 69 (MP),
Ballistic limit is determined by formula (11)：
In formula (11), V is the stroke speed (m/s) of bullet, and t is the thickness (m) of target (oil tank wall), and θ is bullet
Incident angle (°), L are the perimeter (m) of exposed area, and s is the shearing resistance (Pa) of target plate material.
Wherein, the perimeter L of bullet exposed area is determined by formula (24)：
In formula (24), d is the diameter (m) of bullet.
Using JTCG/ME residual velocity equations, i.e. formula (10) can determine the residual velocity V of bulletr(m/s) it is,
In formula, V be bullet stroke speed (m/s), V50For the bullet limit (m/s) of bullet, t is target (oil tank wall)
Thickness (m), ρ are target material density (kg/m3), ApFor the exposed area (m of bullet2), m is the quality (kg) of bullet, and θ is bullet
The incident angle (°) of ball.
Exposed area ApIt is determined by formula (25)：
To sum up, V is obtainedr=886.50m/s.
Step 2：Analyze the variation that bullet punctures energy after oil tank wall.
Bullet is during oil tank wall is punctured, and bullet has speed loss, and oil tank wall is present with plastic deformation, with
And during penetrating shear stress effect, the temperature at bullet and oil tank wall perforation can change.Ignore penetrator hitting
The heat loss during oil tank wall is worn, the thermal energy of plastic work done conversion is stored as the form of interior energy.Bullet is calculated with formula (12)
Interior energy：
Wherein, β turns hot coefficient for plastic work done.2024 aluminium are in 3000s-1Strain rate under, the scope of β value is 0.5~
0.9；So β is taken as 0.9 in the calculation, to calculate the accessible maximum interior energy of bullet.
In the present embodiment, Q=798.50J.
Step 3：It analyzes heat transfer of the bullet in fuel tank in motion process and calculates resulting fuel droplets and steam
It sends out and the quantity of steam of increased fuel oil 3.
Due to bullet, temperature is identical everywhere, then the variation of its temperature is true by following formula in motion process in fuel tank for bullet
It is fixed：
In formula, the specific heat capacity c=439 of bullet material.The contact area A of bullet and ambient enviromentfIt is calculated with formula (26)：
Af=π × 0.01298 × 0.05718+Ap=2.464 × 10-3(m2) (26)
Projectile impact can cause rocking for liquid fuel 3 in fuel tank, and gas-phase space 1 is present with small fuel droplets, works as height
When warm bullet moves in fuel tank, the fuel droplets that it is run into can be evaporated.Assuming that the heat that bullet transfers during the motion
Amount all for evaporating the fuel droplets to suspend in gas-phase space, forms fuel-steam and is gathered in fragmentation afterbody and the air entered
Mixing.The mass rate vaporization of liquid fuel is：
In formula, the specific heat capacity C of fuel oilf=3.01 × T+729, the boiling point T of fuel oilb=-3899/ (log (Pt)-
21.536859), the initial temperature T=278.4 of fuel oil is the heat of evaporation h of fuel oilq=291000.
Step 4：It calculates bullet and penetrates the air capacity brought into during fuel tank.
For cylinder-shaped bullet, the volume of air V in fuel tank is brought intoairIt is determined by formula (17)：
Vair=Ap·s (17)
In formula, the exposed area A of bulletp=1.3232 × 10-4m2；S be bullet move distance, unit m.Bullet band
Entering the volume of air in fuel tank can change with the variation of time.
Step 5：According to discussed above, existing inerting model is modified.
It is A that bullet, which enters the air quality that fuel tank is brought into,air, determined by formula (27)：
Aair=Vair×ρair (27)
Wherein, ρair=1.29kg/m3。
In the air brought into, the amount O of oxygenairIt is determined by formula (18)：
In the air brought into, the amount N of nitrogenairIt is determined by formula (19)：
In formula (18), (19), MairFor the molal weight of air, MN、MOThe respectively molal weight of nitrogen and oxygen.Mixing
The amount of oxygen and nitrogen is calculated respectively by formula (20), (21) in gas-phase space 1 in gas：
OU,mix=OU1+OF,OUT+Oair=OU2+OU,OUT (20)
NU,mix=NU1+NF,OUT+Nair=NU2+NU,OUT (21)
Under projectile strike 2, because bullet heat transfer evaporate fuel-steam increment gas-phase space partial pressure be pvb, newly
Fuel-steam partial pressure p 'v1It is determined by formula (22)：
p′v1=pv1+pvb (22)
The stagnation pressure P of gas-phase space after mixingt,mixIt is determined by formula (23)：
Assuming that the fuel-steam formed due to projectile strike 2 and the air brought into after original mix equilibrium state it is each
Component is sufficiently mixed again, the discharge ratio of the mixed gas therefore when gas-phase space molar ratio.
In the present embodiment, bullet breakdown fuel tank wall thickness is through during fuel tank inside, gas-phase space oxygen and
The concentration variation of fuel-steam is as shown in Figure 4, Figure 5：Portion of air is brought into after entering due to bullet so that oxygen concentration is gradual
Increase, and with the evaporation for being suspended in fuel droplets in gas-phase space, the fuel-steam amount of generation gradually increases, and oxygen concentration becomes
It continuously decreases, but the fuel-steam amount that generates of fuel droplets is compared with less into air capacity, so fuel-steam concentration can be by
Gradually reduce, thus the concentration of fuel tank gas-phase space oxygen and fuel-steam is all first to increase, be then gradually reduced during projectile impact,
But the concentration when concentration of fuel tank gas-phase space oxygen and fuel-steam is totally both greater than without projectile impact during projectile impact.
The variation of gas-phase space oil/gas concentration ratio is as shown in Figure 6：During projectile impact, gas-phase space oil/gas concentration ratio is first
Concentration when increasing, be then gradually reduced, but being generally larger than without projectile impact.
Claims (3)
1. a kind of analyze the method that is influenced on Inerting Aircraft Fuel Tanks of projectile impact, which is characterized in that detailed process is：
Step 1：The residual velocity of projectile impact oil tank wall is calculated according to primary condition；
Assuming that blunt nosed bullet is incident perpendicular to target plate, the residual velocity V of bullet is determined using JTCG/ME residual velocity equationsr
For,
In formula, V be bullet stroke speed, unit m/s；V50For the bullet limit of bullet, unit m/s；T is the thickness of target
Degree, unit m；ρ be target material density, unit kg/m3；ApFor the exposed area of bullet, unit m2；M is the matter of bullet
Amount, unit kg；θ is the incident angle of bullet, and unit is °；
Step 2：Analyze the variation that bullet punctures energy after oil tank wall；
Ignore heat loss of the bullet during oil tank wall is punctured, the thermal energy of plastic work done conversion is stored as the form of interior energy, i.e.,
Wherein, β turns hot coefficient for plastic work done, and Q is the interior energy of bullet, and △ E are the thermal energy that bullet is converted due to plastic work done；
Step 3：Fuel droplets steam during analyzing heat transfer of the bullet in fuel tank in motion process and calculating heat transfer
It sends out and increased fuel-steam amount；
During bullet is through fuel tank gas-phase space, the flux of energy q " of heat transfer is determined by formula (13)：
Q "=h (T-T∞) (13)
In formula, T is bullet surface temperature；T∞The temperature of air-flow is generated for Projectile Motion；H is the heat transfer coefficient of convective heat exchange；
The unit of the flux of energy q " of the heat transfer is W/m2；
Under the conditions of convective heat exchange, bullet heat transfer coefficient hconvIt is determined by cylinder heat transfer coefficient formula (14)：
In formula, k is the thermal conductivity factor of air or fuel oil, and Pr is Prandtl number, ReDIt is the Reynolds on the basis of length is D
Number；
Due to bullet, temperature is identical everywhere, therefore the variation of bullet its temperature in motion process in fuel tank is true by formula (15)
It is fixed：
In formula, c is the specific heat capacity of bullet material；AfFor the contact area of bullet and ambient enviroment,It is the change of temperature at any time
Change amount；
If the heat that bullet transfers during the motion is completely used for the fuel droplets to suspend in evaporation gas-phase space, fuel oil is formed
Steam is gathered in fragmentation afterbody and is mixed with the air entered；The mass rate vaporization m " of liquid fueldropFor：
In formula, CfFor the specific heat capacity of fuel oil, TbFor the boiling point of fuel oil, T is the initial temperature of fuel oil, hqFor the heat of evaporation of fuel oil；
Step 4：Calculate the amount that bullet penetrates the air brought into during fuel tank；
For bullet, the volume of air V in fuel tank is brought intoairFor：
Vair=Ap·s (17)
In formula, ApFor the exposed area of bullet, unit m2；S be bullet move distance, unit m；
Step 5：Existing inerting model is modified；
The air quality that bullet is brought into is Aair, amount of oxygen O ' new in the stagnation pressure of gas-phase space after mixingU,mixIt needs to add and bring into
Air in oxygen amount, therefore：
The new nitrogen amount O ' of gas-phase space is determined by formula (19)U,mixIn nitrogen in the air brought into amount：
In formula, MairFor the molal weight of air, MN、MOThe respectively molal weight of nitrogen and oxygen；Consider bullet during fuel tank air inlet
Ball brings portion of air into, nitrogen amount in gas-phase space after amount of oxygen OU, mix and gas mixing in gas-phase space after gas mixing
NU, mix are respectively：
OU,mix=OU1+OF,OUT+Oair=OU2+OU,OUT (20)
NU,mix=NU1+NF,OUT+Nair=NU2+NU,OUT (21)
In projectile strike, because the fuel-steam increment that the heat transfer of bullet is evaporated in the partial pressure of gas-phase space is pvb, then
Fuel-steam new in the stagnation pressure of gas-phase space partial pressure is after mixing
p′v1=pv1+pvb (22)
The stagnation pressure of gas-phase space is after then mixing
Assuming that each component of the fuel-steam formed due to projectile strike and the air brought into and equilibrium state after original mix
Be sufficiently mixed again, thus the discharge ratio of mixed gas be new equilibrium state when molar ratio.
2. the method that analysis projectile impact influences Inerting Aircraft Fuel Tanks as described in claim 1, which is characterized in that step 1
Described in the bullet limit pass through formula (11) obtain：
In formula, L is the perimeter of exposed area, and unit m, s are the shearing resistance of target plate material, unit Pa.
3. the method that analysis projectile impact influences Inerting Aircraft Fuel Tanks as described in claim 1, which is characterized in that step 2
In the variation of energy after analyzing bullet breakdown oil tank wall, in order to penetrate bullet to each gas component in fuel tank gas-phase space
It influences to maximize, if the heat converted during bullet breakdown oil tank wall has all passed to bullet, due to leading for bullet material
Hot function is higher, therefore ignores the temperature gradient inside bullet, if temperature is identical everywhere for bullet.
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| CN110765409A (en) * | 2019-10-23 | 2020-02-07 | 北京理工大学 | Method for predicting damage behavior of projectile penetrating through reinforced concrete target plate |
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| CN108090274A (en) * | 2017-12-13 | 2018-05-29 | 中国航空工业集团公司成都飞机设计研究所 | A kind of engineering design method of the airborne inerting system of fuel tanker |
| CN109145372B (en) * | 2018-07-17 | 2023-04-18 | 中国航空工业集团公司沈阳飞机设计研究所 | Thermal calculation modeling method for aircraft fuel tank and calculation model thereof |
| CN113492998B (en) * | 2021-01-15 | 2023-09-01 | 西北工业大学 | Experimental device and experimental method for simulating multi-angle impact of projectile on fuel tank of aircraft |
| CN113135296B (en) * | 2021-05-14 | 2022-03-08 | 金陵科技学院 | System for inhibiting fuel oil coking and working method thereof |
| CN114923378B (en) * | 2022-04-19 | 2023-02-03 | 北京理工大学 | Device and method for testing ignition enhancement of active damage element with gradient threshold |
| CN114692318B (en) * | 2022-06-01 | 2022-08-26 | 中国飞机强度研究所 | Grid type fuel tank structure damage resistance assessment method for airplane impact dynamics test |
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