CN115636078B - Hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection - Google Patents
Hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection Download PDFInfo
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- 238000002347 injection Methods 0.000 title claims abstract description 85
- 239000007924 injection Substances 0.000 title claims abstract description 85
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- 229920001971 elastomer Polymers 0.000 title claims abstract description 28
- 239000000806 elastomer Substances 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 25
- 230000009467 reduction Effects 0.000 title claims abstract description 21
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
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- ADHFMENDOUEJRK-UHFFFAOYSA-N 9-[(4-fluorophenyl)methyl]-n-hydroxypyrido[3,4-b]indole-3-carboxamide Chemical compound C1=NC(C(=O)NO)=CC(C2=CC=CC=C22)=C1N2CC1=CC=C(F)C=C1 ADHFMENDOUEJRK-UHFFFAOYSA-N 0.000 claims description 2
- 241001482237 Pica Species 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- 239000003575 carbonaceous material Substances 0.000 claims description 2
- 229910052681 coesite Inorganic materials 0.000 claims description 2
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Abstract
The invention discloses a hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection, and belongs to the field of aerospace. The implementation method of the invention comprises the following steps: solving the density, pressure and wall ejection speed of the ejection wall according to a three-dimensional NS equation and a wall momentum conservation equation, and setting an ablation gas ejection boundary condition; under hypersonic incoming flow conditions and under the condition of meeting the constructed injection boundary conditions, the ablation material can be subjected to the injection of the ablation gas quality outwards in an injection area of the elastomer through the passive ablation of the material paved on the surface of the elastomer, the density of the surface of the elastomer is reduced by using the injected ablation gas, the velocity gradient at the surface of the elastomer is reduced, and the friction resistance between the injection area and the downstream of the injection area is reduced; in addition, the ablation gas emitted from the surface of the projectile body can push out the shock wave of the surface of the hypersonic aircraft, so that the shock wave is far away from the surface of the projectile body, the temperature gradient at the wall surface is reduced, the heat flow of the wall surface is reduced, the effect of reducing the aerodynamic heat and friction resistance of the surface of the projectile body is realized, and the aerodynamic performance of the aircraft is improved.
Description
Technical Field
The invention relates to a hypersonic elastomer surface resistance and heat reduction method by material ablation gas injection, in particular to a control method for reducing heat flow and friction resistance on the hypersonic elastomer surface, and belongs to the field of aerospace.
Background
The hypersonic aircraft has the characteristics of quick global reaching, high detection difficulty, strong outburst prevention capability, high combat effectiveness and the like, and becomes one of the main focuses of international competition. Hypersonic aircrafts are frequently frustrated in the development process, such as two flight experiments of American HTV-2 project fail, HIFiRE-5 flight failures are jointly implemented in the United states and Australia, and the like, and the main reasons are that hypersonic technology has a plurality of unknown fields, especially the influence of thermal barrier problems and wall friction resistance caused by aerodynamic heat, so that effective drag reduction and heat reduction measures are needed to be adopted for guaranteeing the flight safety of the aircrafts and improving the aerodynamic performance of the aircrafts.
The thermal barrier problem caused by aerodynamic heat has become a bottleneck restricting the development of hypersonic aircrafts. When the aircraft makes supersonic flight, the surface of the aircraft body and the airflow generate intense friction, and the air is blocked and compressed to lead the temperature to rise sharply, so that a strong thermal barrier is formed for the aircraft; when the flying speed is further increased to hypersonic speed, the air flow characteristic is changed substantially, and the physical phenomena of the air flow characteristic are mainly represented by a thin shock wave layer, an entropy layer, viscous interference, low density and a real gas effect in a high-temperature shock wave layer. Taking a reentry vehicle with Mach number Ma >20 as an example, the temperature of the residence point of the front edge of the reentry vehicle can reach more than 1 multiplied by 10 4 K, and in the high-temperature environment, not only can the surrounding air ionize, but also the surface material of the vehicle can chemically react to cause unrecoverable damage to the vehicle. Accordingly, to ensure flight safety, appropriate thermal protection measures must be taken to ensure proper operation of the aircraft structure and internal settings. The drag reduction and heat reduction schemes of the aircraft are few under the condition of the high Mach number real gas effect, and the existing drag reduction and heat reduction methods are not ideal.
The research on the resistance reduction and heat reduction of hypersonic elastomers mainly focuses on how to effectively reduce the heat flow and friction resistance of the surfaces of the elastomers. The pyrolysis of the elastomeric surface material generates multi-component pyrolysis gas, and partial material ablation causes the elastomeric surface to be wrapped by the pyrolysis gas (the relative molecular weight is smaller than that of air), so that the heat flow and the friction resistance are reduced.
Disclosure of Invention
In order to effectively reduce heat flow and friction resistance on the surface of the hypersonic elastomer, the main purpose of the invention is to provide a hypersonic elastomer surface resistance reduction and heat reduction method based on material ablation gas injection, solving the density, pressure and wall injection speed of injection wall according to a three-dimensional NS equation and a wall momentum conservation equation, and setting ablation gas injection boundary conditions according to the density, pressure and wall injection speed; the ablative material can perform ablative gas quality injection outwards in an injection area of the projectile under hypersonic incoming flow conditions and under the condition of meeting the established injection boundary conditions, the ablative gas injected from the surface of the projectile is utilized to reduce the density of the surface of the projectile, the velocity gradient of the surface of the projectile is reduced, and the frictional resistance of the injection area and the downstream of the injection area is further reduced; in addition, the ablation gas emitted from the surface of the projectile can push out the shock wave of the surface of the hypersonic aircraft, so that the shock wave is far away from the surface of the projectile, the temperature gradient at the wall surface is reduced, the heat flow of the wall surface is reduced, the effect of reducing the aerodynamic heat and friction resistance of the surface of the projectile is realized, and the aerodynamic performance of the aircraft is further improved.
The aim of the invention is achieved by the following technical scheme.
The invention discloses a hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection, which comprises the following steps:
Step one: under the incoming flow condition that the Mach number Ma is between 12 and 25 and the flying height is between 35 and 80Km, an ablation material for generating ablation gas at the front end of the projectile body is selected according to the high ultrasonic velocity incoming flow condition, and a model, a thermal model, a transport model and a chemical reaction model are selected for the ablation material.
Constructing a thermodynamic model:
The internal energy of the molecule consists of translational energy, rotational energy, vibration energy, electron energy and zero energy; the internal energy of atoms consists of kinetic energy, electron energy and zero energy. In this patent, the internal energy of molecules and atoms is obtained by a statistical thermodynamic partitioning function method, and the internal energy mode for component s is:
Wherein: ru=8314J/(kmol.k) is a general gas constant; m s is the molar mass of the component s, in g/mol; θvs is the characteristic vibration temperature of the component s, in K.
From thermodynamics, the specific heat capacity of the gas component s is shown as follows:
cv,s＝cv,tr,s+cv,rot,s+cv,v,s
the specific expression is:
Under the Park double temperature model, the internal energy mode of the molecule is calculated by adopting the formula. For thermodynamic equilibrium flow, there is only one translational temperature (T), vibration temperature T v = T in the above equation.
For a chemical reaction mixture, the internal energy e and the static enthalpy h are calculated by the following formula:
The total enthalpy H and total energy E of the mixed gas are calculated by the following formula:
Constructing a transport coefficient model and a chemical reaction dynamic model:
The transport coefficients employed in the thermochemical unbalanced flow consist essentially of the viscosity coefficient μ, the thermal conductivity coefficient k (one temperature in the flow field corresponds to one thermal conductivity coefficient) and the mass diffusion coefficient D, the viscosity coefficient polynomial fit for component s being
The fitting range of the polynomial is 1000-30000K. For thermodynamic equilibrium gas (single temperature model), when the temperature is higher than 1000K, calculating the heat conduction coefficient by using Gupta fitting polynomials; when the temperature is lower than 1000K, the thermal conductivity is calculated using the plantty number:
For thermodynamically non-equilibrium gases (bi-temperature model), the semi-empirical formula of Eucken is used for calculation:
Where k tr,s and k v,s are the transport and vibrational heat transfer coefficients, respectively, of component s.
The diffusion coefficient calculation uses a two-component diffusion model based on Schimit number hypothesis for molecules, atoms and ions other than electrons:
Wherein Schmidt number sc=0.5 for atoms and molecules; for ion sc=0.25. The diffusion coefficient of electrons is calculated by the following formula:
Constructing a chemical reaction source item in a chemical reaction power model:
Assuming that the number of components in the gas is ns and the number of primitive reactions possibly existing among the components is nr, the chemical reaction formula is as follows:
Wherein r is a chemical reaction sequence number, and X i＝ρi/Mi is the mole number of a chemical component per unit volume.
The specific form of the component mass production rate omega s of the component s per unit volume is as follows:
Wherein: alpha rs,βrs is the equivalent coefficient of the reactant and the product respectively, Respectively expressed as the elementary reaction forward and reverse reaction rate coefficients.
The primitive reaction rate coefficient can be calculated by the Arrhenius formula:
Wherein: t d is the chemical reaction control temperature, and C r,nr,Er is the chemical reaction rate constant, respectively.
The selection requirements of the construction ablation material are as follows:
silicon-based ablative material: an ablation product model consisting of 34 component 57 chemical equations was constructed, with 24 ablation gas components as follows ：O2、、N2、NO、NO+、CO、CO2、O、N、C、C2、CN、H2、H、H2O、OH、C2H2、 C2H、CH2、CH、HCO、Si、SiO、SiO2、e.
Carbon-based material: build an ablation product model consisting of 17 component 33 chemical equations, 17 ablation gas components are as follows ：O、N、O2、N2、NO、NO+、e-、N2 +、CO、C、C2、C3、CO2、CN、CH2、H2、H.
PICA material: build an ablation product model consisting of 18-component 27 chemical equations, 18 ablation gas components are as follows ：CO2、CO、N2、O2、NO、C2、C3、CN、H2、HCN、C、N、O、H、C+、N+、O+、e.
Step two: solving the density, pressure and wall ejection speed of the ejection wall according to the three-dimensional NS equation and the wall momentum conservation equation and combining the thermodynamic model, the transport model and the chemical reaction model constructed in the first step, and constructing the ablation gas ejection boundary conditions according to the density, the pressure and the wall ejection speed.
Constructing a smooth wall boundary condition:
in the viscous flow calculation, the wall surface satisfies the slip-free boundary condition, i.e., u=v=w=0;
For the isothermal wall case, let the wall temperature be T w, there is T w＝T＝Tv;
non-catalytic wall conditions:
Complete catalytic wall conditions: y s,w＝Ys,∞, s=1.
Selecting a classical first-order sliding boundary condition of Maxwell:
wherein s represents the slip amount, and w represents the wall parameter. n is the wall surface external normal vector. Molecular mean free path
Sigma and alpha are tangential momentum adjustment coefficient and energy adjustment coefficient, respectively, sigma, alpha epsilon [0,1]. For the tangential momentum adjustment coefficient, sigma=0 corresponds to the complete specular reflection of the gas molecules on the wall surface, and sigma=1 corresponds to the complete diffuse reflection of the wall surface; the tangential momentum adjustment coefficient characterizes how well the temperature of the reflecting molecules "adapts" to the temperature of the object plane, α=0 corresponds to the incident molecules not adapting to the object plane temperature at all, i.e. no energy exchange takes place between the incident molecules and the wall surface at all, whereas α=1 corresponds to the situation of complete thermal adaptation, i.e. the incident molecules give all the carried energy to the wall surface.
And (3) constructing an ablation gas ejection boundary condition according to the density, the pressure and the wall ejection speed by considering the coupling relation between the flow field and the material ablation ejection response and combining the conditions shown in formulas (1) to (16), and constructing the ablation gas ejection boundary condition after specific information of ablation gas ejection such as wall temperature, mass flow rate, pyrolysis gas mass fraction and the like is obtained by combining the ablation response calculation.
The density, pressure and speed on the wall surface are calculated by the formulas (17) and (18).
The left side of equation (19) represents the diffuse and convective flux approaching the wall from the flow field domain, the right side represents the convective flux of the wall,Is the mass flow rate, T w is the wall temperature, and Y gs is the ablation gas composition. The mass fraction Y ws of the injection gas is calculated by a mass balance equation of formula (19).
Equation (17), equation (18) and equation (19) are the constructed ablation gas ejection boundary conditions.
Step three: and (3) presetting an ablation material in the step I, solving the injection boundary condition of the ablation gas constructed in the step II, and determining the mass fraction and the mass flow rate of each component of the ablation gas by combining the step II under the hypersonic incoming flow condition and the injection boundary condition constructed in the step I, so as to select the ablation material and determine the gas component and the mass fraction of the ablation product.
Determining the chemical reaction components (N 2、O2, NO, N, O) of the air flow field; boundary layer ablative gas composition (H2、CO、 CH4、H2O、CO2、OH、C2H2、HCN、C2H、C3、CN);
Setting ablation gas injection mass flow rate through formula (6)
In the formula (9)Is the mass flow rate, ρ jet is the injection gas density, v jet is the injection velocity
Tjet＝Tw (21)
Wherein T jet is the injection temperature.
Step four: according to the third step, an ablation material is selected, the gas component and the mass fraction of an ablation product are determined, the ablation material is paved at the front end position of the projectile body, the ablation material is subjected to ablation gas mass ejection outwards in an ejection area of the projectile body under hypersonic incoming flow conditions and under the condition of meeting the constructed ejection boundary conditions, the surface density of the projectile body is reduced by using the ablation gas ejected from the surface of the projectile body, the velocity gradient at the surface of the projectile body is reduced, and the friction resistance between the ejection area and the downstream of the ejection area is further reduced; in addition, the ablation gas emitted from the surface of the bullet can push out the shock wave of the surface of the hypersonic aircraft, so that the shock wave is far away from the surface of the bullet, the temperature gradient at the wall surface is reduced, the heat flow of the wall surface is reduced, the effect of reducing the aerodynamic heat and friction resistance of the surface of the bullet is realized, and the aerodynamic performance of the aircraft is further improved.
The beneficial effects are that:
1. According to the hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection, an ablation material is paved at the front end position of the elastomer, the ablation material can be subjected to uniform mass injection of ablation gas outwards in an elastomer injection area under hypersonic incoming flow conditions and under the condition of meeting the established injection boundary conditions, the injection velocity along the normal direction of the wall surface is caused by mass injection, the flow velocity at the wall surface is reduced, namely the velocity gradient at the wall surface is reduced, the friction resistance between an injection area and the downstream of the injection area is further reduced, and the effects of reducing the aircraft resistance and improving aerodynamic force are achieved.
2. According to the hypersonic elastomer surface drag reduction and heat reduction method based on material ablation gas injection, the ablation material is paved at the front end of the elastomer, the ablation material can be used for injecting ablation gas with uniform quality outwards in an elastomer injection area under hypersonic incoming flow conditions and under the condition of meeting injection boundary conditions, the ablation gas injected from the elastomer surface can also be used for pushing shock waves of the hypersonic aircraft surface outwards, so that the shock waves are far away from the elastomer surface, the temperature gradient at the wall surface is reduced, the influence of wall surface heat flow on the aircraft is reduced greatly, and the aerodynamic performance of the aircraft is improved.
3. Compared with the traditional mode of injecting and reducing heat flow by single air quality, the hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection disclosed by the invention combines the characteristics of heat flow and friction resistance influence caused by material pyrolysis and quality injection on the basis of realizing the beneficial effects 1 and 2, realizes the effect of reducing wall heat flow based on hypersonic aircraft wall quality injection, and can realize better resistance and heat reduction effect compared with air quality injection.
Drawings
FIG. 1 is a flow chart of a method for reducing drag and heat on the surface of a hypersonic elastomer by injecting material ablation gas;
FIG. 2 is a schematic view of a wall portion area quality ejection area of an embodiment;
fig. 3 is a material ablation gas injection and pure air injection Ma field cloud image, wherein: fig. 3 (a) is a mass-free injection Ma field cloud, fig. 3 (b) is a pure air mass injection Ma field cloud, and fig. 3 (c) is an ablative gas mass injection Ma field cloud.
Fig. 4 is a cloud illustration of material ablation gas injection and pure air injection gas composition, wherein: fig. 4 (a) is a mass-free injection gas composition cloud, fig. 4 (b) is a pure air mass injection gas composition cloud, and fig. 4 (c) is an ablative gas mass injection gas composition cloud.
Fig. 5 is a cloud plot of material ablation gas injection and pure air injection heat flow distribution, wherein: fig. 5 (a) is a mass-free injection wall heat flux cloud, fig. 5 (b) is a pure air mass injection wall heat flux cloud, and fig. 5 (c) is an ablated gas mass injection wall heat flux cloud.
Fig. 6 is a cloud plot of material ablation gas ejection and pure air ejection friction resistance distribution, wherein: fig. 6 (a) is a mass-free jet wall friction cloud, fig. 6 (b) is a pure air mass jet wall friction cloud, and fig. 6 (c) is an ablative gas mass jet wall friction cloud.
Fig. 7 is a graph comparing heat flows of a windward side and a leeward side of material ablation gas ejection and pure air ejection, wherein: fig. 7 (a) is a windward side heat flow comparison chart, and fig. 7 (b) is a leeward side heat flow comparison chart.
FIG. 8 is a graph comparing frictional resistance of windward and leeward sides of material ablated gas ejection versus pure air ejection, wherein: fig. 8 (a) is a graph showing contrast of friction on the windward side, and fig. 8 (b) is a graph showing contrast of friction on the leeward side.
Detailed Description
For a better description of the objects and advantages of the present invention, the following description will be given with reference to the accompanying drawings and examples.
Example 1:
As shown in FIG. 1, the method for reducing resistance and heat on the surface of the hypersonic elastomer based on material ablation gas injection disclosed in the embodiment comprises the following specific implementation steps:
Step one: under the incoming flow condition that the Mach number Ma is between 12 and 25 and the flying height is between 35 and 80Km, an ablation material for generating ablation gas at the front end of the projectile body is selected according to the high ultrasonic velocity incoming flow condition, and a model, a thermal model, a transport model and a chemical reaction model are selected for the ablation material.
The analysis object of this example is a blunt cone with a length l=0.15 m and a half cone angle of 5 ° and a head radius of 1mm, the incoming flow mach number Ma ∞ =25.0, the flying height of 65km and the attack angle of 10 °, the isothermal wall is adopted for calculation, and the wall temperature T w =1500k. The air flow field adopts Gupta 5 component (N 2、O2, NO, N, O) chemical reaction to calculate, thermodynamic calculation adopts Park double-temperature model, and wall surface catalysis adopts complete catalysis wall. And selecting material ablation gas (CO and CH 4、H2、H2O、CO2) to carry out mass injection. The mass ejection zone is shown in figure 2.
Step two: solving the density, pressure and wall ejection speed of the ejection wall according to the three-dimensional NS equation and the wall momentum conservation equation and combining the thermodynamic model, the transport model and the chemical reaction model constructed in the first step, and constructing the ablation gas ejection boundary conditions according to the density, the pressure and the wall ejection speed.
The injection area at the front end of the blunt cone is provided with a gas injection boundary:
the density, pressure and speed on the wall surface are calculated by the formulas (17) and (18).
Step three: and (3) presetting an ablation material in the step I, solving the injection boundary condition of the ablation gas constructed in the step II, and determining the mass fraction and the mass flow rate of each component of the ablation gas by combining the step II under the hypersonic incoming flow condition and the injection boundary condition constructed in the step I, so as to select the ablation material and determine the gas component and the mass fraction of the ablation product.
Selecting mass flow rate of mass injection as mG=0.02 kg/m 2 & s; the gas temperature t=t w =1500k is caused.
TABLE 2 injection gas composition mass fraction
Step four: according to the third step, an ablation material is selected, the gas component and the mass fraction of an ablation product are determined, the ablation material is paved at the front end position of the projectile body, the ablation material is subjected to ablation gas mass ejection outwards in an ejection area of the projectile body under hypersonic incoming flow conditions and under the condition of meeting the constructed ejection boundary conditions, the surface density of the projectile body is reduced by using the ablation gas ejected from the surface of the projectile body, the velocity gradient at the surface of the projectile body is reduced, and the friction resistance between the ejection area and the downstream of the ejection area is further reduced; in addition, the ablation gas emitted from the surface of the bullet can push out the shock wave of the surface of the hypersonic aircraft, so that the shock wave is far away from the surface of the bullet, the temperature gradient at the wall surface is reduced, the heat flow of the wall surface is reduced, the effect of reducing the aerodynamic heat and friction resistance of the surface of the bullet is realized, and the aerodynamic performance of the aircraft is further improved.
Fig. 5 is a cloud plot of material ablation gas injection and pure air injection heat flow distribution, wherein: fig. 5 (a) is a mass-free injection wall heat flux cloud, fig. 5 (b) is a pure air mass injection wall heat flux cloud, and fig. 5 (c) is an ablated gas mass injection wall heat flux cloud. Fig. 7 is a graph comparing heat flows of a windward side and a leeward side of material ablation gas ejection and pure air ejection, wherein: fig. 7 (a) is a windward side heat flow comparison chart, and fig. 7 (b) is a leeward side heat flow comparison chart. By comparing the windward and leeward heat flows in fig. 7, the heat flow of the wall surface can be better reduced by injecting the ablative gas generated by laying the ablative material than by not injecting the mass and injecting the single air mass; fig. 6 is a cloud plot of material ablation gas ejection and pure air ejection friction resistance distribution, wherein: fig. 6 (a) is a mass-free injection wall friction cloud, fig. 6 (b) is a pure air mass injection wall friction cloud, and fig. 6 (c) is an ablative gas mass injection wall friction cloud. FIG. 8 is a graph comparing frictional resistance of windward and leeward sides of material ablated gas ejection versus pure air ejection, wherein: fig. 7 (a) is a graph showing contrast of friction on the windward side, and fig. 7 (b) is a graph showing contrast of friction on the leeward side. By comparing the windward side friction resistance with the leeward side friction resistance in fig. 8, compared with mass injection and single air mass injection, the wall friction resistance can be better reduced by injecting the ablation gas generated by paving the ablation material.
While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the principles of the present invention, and that various modifications, equivalents, improvements and modifications may be made without departing from the spirit and principles of the present invention.
Claims (3)
1. The hypersonic elastomer surface resistance and heat reduction method based on material ablation gas injection is characterized by comprising the following steps of: comprises the following steps of the method,
Step one: under the incoming flow condition that the Mach number Ma is between 12 and 25 and the flying height is between 35 and 80Km, selecting an ablation material for generating ablation gas at the front end of the projectile body according to the hypersonic incoming flow condition, and constructing an ablation material selection model, a thermodynamic model, a transport model and a chemical reaction model;
In the first step, the first step is to perform,
Constructing a thermodynamic model:
The internal energy of the molecule consists of translational energy, rotational energy, vibration energy, electron energy and zero energy; the internal energy of atoms consists of kinetic energy, electron energy and zero energy; the internal energy of molecules and atoms is obtained by a statistical thermodynamic coordination function method, and the internal energy modes for the component s are as follows:
Wherein: ru is a universal gas constant; m s is the molar mass of the component s, in g/mol; θvs is the characteristic vibration temperature of the component s, and the unit is K;
From thermodynamics, the specific heat capacity of the gas component s is shown as follows:
the specific expression is:
under a Park double-temperature model, the internal energy mode of the molecule is calculated by adopting the formula; for thermodynamic equilibrium flow, there is only one translational temperature T, vibration temperature T v = T in the above formula;
For a chemical reaction mixture, the internal energy e and the static enthalpy h are calculated by the following formula:
The total enthalpy H and total energy E of the mixed gas are calculated by the following formula:
Constructing a transport coefficient model and a chemical reaction dynamic model:
The transport coefficients employed in the thermochemical unbalanced stream mainly include the viscosity coefficient μ, the thermal conductivity coefficient k and the mass diffusion coefficient D, the viscosity coefficient polynomial fit for component s being:
The fitting range of the polynomial is 1000-30000K; for thermodynamic equilibrium gas, when the temperature is higher than 1000K, calculating the heat conduction coefficient by adopting a Gupta fitting polynomial; when the temperature is below 1000K, the heat transfer coefficient is calculated using the prandtl number:
For thermodynamically non-equilibrium gases, the semi-empirical formula of Eucken is used to calculate:
wherein k tr,s and k v,s are the transport and vibrational heat transfer coefficients, respectively, of component s;
the diffusion coefficient calculation uses a two-component diffusion model based on Schimit number hypothesis for molecules, atoms and ions other than electrons:
Wherein Schmidt number sc=0.5 for atoms and molecules; for ion sc=0.25; the diffusion coefficient of electrons is calculated by the following formula:
Constructing a chemical reaction source item in a chemical reaction power model:
assuming that the number of components existing in the gas is ns and the number of primitive reactions possibly existing among the components is nr, the chemical reaction equation is:
Wherein r is a chemical reaction sequence number, and X i＝ρi/Mi is the mole number of a chemical component in unit volume;
the specific form of the component mass production rate omega s of the component s per unit volume is as follows:
Wherein: alpha rs,βrs is the equivalent coefficient of the reactant and the product respectively, Respectively expressed as the forward and reverse reaction rate coefficients of the elementary reaction;
The primitive reaction rate coefficient can be calculated by the Arrhenius formula:
Wherein: t d is chemical reaction control temperature, and C r,nr,Er is chemical reaction rate constant respectively;
The selection requirements of the construction ablation material are as follows:
silicon-based ablative material: an ablation product model consisting of 34 component 57 chemical equations was constructed, with 24 ablation gas components as follows ：O2、N2、NO、NO+、CO、CO2、O、N、C、C2、CN、H2、H、H2O、OH、C2H2、C2H、CH2、CH、HCO、Si、SiO、SiO2、e;
Carbon-based material: an ablation product model consisting of 17-component 33 chemical reaction formula was constructed, 17 ablation gas components were as follows ：O、N、O2、N2、NO、NO+、e-、N2 +、CO、C、C2、C3、CO2、CN、CH2、H2、H;
PICA material: build an ablation product model consisting of 18-component 27 chemical equations, 18 ablation gas components are as follows ：CO2、CO、N2、O2、NO、C2、C3、CN、H2、HCN、C、N、O、H、C+、N+、O+、e;
Step two: solving the density, pressure and wall ejection speed of the ejection wall according to the three-dimensional NS equation and the wall momentum conservation equation and combining the thermodynamic model, the transport model and the chemical reaction model constructed in the first step, and constructing an ablation gas ejection boundary condition according to the density, the pressure and the wall ejection speed;
step three: the method comprises the steps that an ablation material is preset in the first step, the injection boundary condition of the ablation gas constructed in the second step is solved, the ablation material is used for determining the mass fraction and the mass flow rate of each component of the ablation gas by combining the second step under the hypersonic incoming flow condition and the injection boundary condition constructed in the first step, and then the ablation material is selected and the gas components and the mass fraction of an ablation product are determined;
step four: according to the third step, an ablation material is selected, the gas component and the mass fraction of an ablation product are determined, the ablation material is paved at the front end position of the projectile body, the ablation material is subjected to ablation gas mass ejection outwards in an ejection area of the projectile body under hypersonic incoming flow conditions and under the condition of meeting the constructed ejection boundary conditions, the surface density of the projectile body is reduced by using the ablation gas ejected from the surface of the projectile body, the velocity gradient at the surface of the projectile body is reduced, and the friction resistance between the ejection area and the downstream of the ejection area is further reduced; in addition, the ablation gas emitted from the surface of the projectile can push out the shock wave of the surface of the hypersonic aircraft, so that the shock wave is far away from the surface of the projectile, the temperature gradient at the wall surface is reduced, the heat flow of the wall surface is reduced, the effect of reducing the aerodynamic heat and friction resistance of the surface of the projectile is realized, and the aerodynamic performance of the aircraft is further improved.
2. The method for reducing drag and heat on the surface of hypersonic elastomer based on material ablation gas injection as set forth in claim 1, wherein the method comprises the following steps: in the second step, the second step is to carry out the process,
Constructing a smooth wall boundary condition:
In viscous flow calculations, the wall surface meets the slip-free boundary condition, i.e
For the isothermal wall case, let the wall temperature be T w, there is T w＝T＝Tv;
non-catalytic wall conditions: s＝1,...,ns；
complete catalytic wall conditions: y s,w＝Ys,∞, s=1,..ns;
selecting a classical first-order sliding boundary condition of Maxwell:
Wherein s represents the slip quantity, and w represents the wall parameter; n is the wall surface external normal vector; molecular mean free path
Sigma and alpha are tangential momentum adjustment coefficient and energy adjustment coefficient respectively, sigma, alpha epsilon [0,1]; for the tangential momentum adjustment coefficient, sigma=0 corresponds to the complete specular reflection of the gas molecules on the wall surface, and sigma=1 corresponds to the complete diffuse reflection of the wall surface; the tangential momentum adjustment coefficient characterizes how much the temperature of the reflective molecules "adapts" to the temperature of the object plane, α=0 corresponds to the fact that the incident molecules do not adapt to the temperature of the object plane at all, i.e. no energy exchange occurs between the incident molecules and the wall surface at all, while α=1 corresponds to the fact that the incident molecules adapt to the wall surface at all, i.e. the incident molecules give all the carried energy to the wall surface;
The coupling relation between a flow field and material ablation ejection response is considered, the conditions of the formulas (1) to (16) are combined, an ablation gas ejection boundary condition is constructed according to density, pressure and wall ejection speed, and specific information of wall temperature, mass flow rate and pyrolysis gas mass fraction is obtained by combining ablation response calculation, and then the ablation gas ejection boundary condition is constructed;
calculating the density, pressure and speed on the wall surface through the formulas (17) and (18);
the left side of equation (19) represents the diffuse and convective flux approaching the wall from the flow field domain, the right side represents the convective flux of the wall, Is the mass flow rate, T w is the wall temperature, Y gs is the ablation gas composition; the mass fraction Y ws of the injection gas is calculated by a mass balance equation of the formula (19);
equation (17), equation (18) and equation (19) are the constructed ablation gas ejection boundary conditions.
3. The method for reducing drag and heat on the surface of hypersonic elastomer based on material ablation gas injection as set forth in claim 2, wherein the method comprises the following steps: in the third step, the first step is performed,
Determining the chemical reaction components (N 2、O2, NO, N, O) of the air flow field; boundary layer ablative gas composition (H2、CO、CH4、H2O、CO2、OH、C2H2、HCN、C2H、C3、CN);
Setting ablation gas injection mass flow rate through formula (6)
In the formula (9)Is the mass flow rate, ρ jet is the injection gas density, v jet is the injection velocity
Tjet＝Tw (21)
Wherein T jet is injection temperature, and T w is wall temperature.
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| US4917335A (en) * | 1988-03-31 | 1990-04-17 | Gt-Devices | Apparatus and method for facilitating supersonic motion of bodies through the atmosphere |
| CN106845072A (en) * | 2016-12-15 | 2017-06-13 | 中国航天空气动力技术研究院 | Ablation velocity under many reaction mechanism controls of multicomponent heat insulation material determines method |
| CN111458366A (en) * | 2020-04-17 | 2020-07-28 | 北京空天技术研究所 | Ablation thermal protection system structure pneumatic heat/heat transfer coupling analysis method |
| CN112597590A (en) * | 2020-12-24 | 2021-04-02 | 中国航天空气动力技术研究院 | Method for determining body ablation mass loss of resin-based heat-proof material |
| CN113792508A (en) * | 2021-11-10 | 2021-12-14 | 中国空气动力研究与发展中心计算空气动力研究所 | Aerodynamic heat calculation method considering surface quality injection effect |
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| US4917335A (en) * | 1988-03-31 | 1990-04-17 | Gt-Devices | Apparatus and method for facilitating supersonic motion of bodies through the atmosphere |
| CN106845072A (en) * | 2016-12-15 | 2017-06-13 | 中国航天空气动力技术研究院 | Ablation velocity under many reaction mechanism controls of multicomponent heat insulation material determines method |
| CN111458366A (en) * | 2020-04-17 | 2020-07-28 | 北京空天技术研究所 | Ablation thermal protection system structure pneumatic heat/heat transfer coupling analysis method |
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