CN114572387B - Forward-jet flow resistance-reducing heat-proof method for hypersonic-velocity pointed cone aircraft - Google Patents

Abstract

The invention discloses a forward jet flow resistance-reducing and heat-preventing method for a hypersonic pointed cone aircraft, wherein a jet flow resistance-reducing and heat-preventing system is arranged on the wall surface of the windward side of the aircraft, and comprises a plurality of jet pipes, and the jet pipes jet in the forward direction along the incoming flow direction of the wall surface of the windward side of the aircraft; the spray pipes are sonic or supersonic spray pipes, and a plurality of spray pipes are uniformly distributed along the circumferential direction or the spanwise direction of the pointed cone to form an array covering circumferential or spanwise range, and the shape, the size and the working parameters of the spray pipes are optimally set. The method aims at the hypersonic pointed cone aircraft, a jet flow resistance-reducing and heat-preventing system of the hypersonic pointed cone aircraft can be arranged on most of the windward side of the aircraft, the pressure resistance and the friction resistance can be respectively reduced by different mechanisms, the jet flow resistance-reducing and heat-preventing effects are achieved, the downstream of jet flow has a heat flow reducing effect under different jet flow conditions, and the heat flow reducing area covers the cone section and extends to the column section.

Description

A method for drag reduction and heat protection of forward jet flow for hypersonic sharp-cone aircraft

technical field

The invention belongs to the field of aircraft design, and relates to a drag reduction and heat protection method for a forward jet flow for a hypersonic sharp-cone aircraft.

Background technique

Hypersonic vehicle technology is one of the key technologies affecting the future pattern of international relations, but hypersonic flight will cause aerodynamic drag and aerodynamic heating problems. Among them, piezoresistance dominates the aerodynamic resistance, which can reach 2/3 of the total resistance, and increases significantly with the increase of the flight Mach number, which seriously affects the aerodynamic performance of the aircraft; aerodynamic heating corresponds to the thermal protection requirements, so the overall design of the aircraft is proposed. Severe constraints, the above constraints often also impose additional constraints on the aerodynamic performance of the aircraft. Therefore, drag reduction and heat protection technology is one of the key supporting technologies for hypersonic vehicle technology.

In the series of monographs of Hypersonic Publishing Engineering, "New Methods of Drag Reduction and Heat Protection for Space Mission Vehicles and Their Applications", it is pointed out that the existing methods of drag reduction and heat protection are divided into two categories: active and passive. Passive methods mainly use special surface materials, rely heavily on new material technologies, and are greatly affected by the ablation environment. Active methods are divided into windward concave cavity, reverse jet flow, drag reduction rod, energy delivery and their combined configuration, among which reverse jet flow and drag reduction rod are the two main methods in the existing research. The drag-reducing rod confines the detached shock wave of the aircraft head to a far upstream distance through geometric constraints. A separation zone is formed between the drag-reducing rod and the aircraft head, and a weaker separation shock wave is generated, which reduces the wall pressure and heat flow of the aircraft head. , the high heat flow environment is endured by the head of the drag reduction rod, which has been used in the US "Trident" missile. The reverse jet achieves a function similar to the drag reduction rod through the jet, confines the debody shock to the upstream of the reverse jet, and forms a recirculation zone at the head of the aircraft to weaken the shock at the head to achieve the purpose of reducing drag and preventing heat. The physicochemical action of the cooling medium can further reduce the wall heat flow. However, the above active methods are mainly aimed at the wave resistance generated by the passivation of the head of the blunt body aircraft, and the strong debody shock wave is weakened into an oblique shock wave through the flow control method to achieve the purpose of resistance reduction. For a pointed-cone aircraft with a small head bluntness, the proportion of the head wave drag is small, and the above method has no significant drag reduction effect.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a method for drag reduction and heat prevention by a forward jet flow for a hypersonic pointed-cone aircraft. For the hypersonic pointed-cone aircraft, a nozzle is arranged on the wall of the windward surface of the aircraft to carry out the forward jet flow. , which can effectively reduce piezoresistance and frictional resistance, and play a role of heat protection while realizing the jet flow drag reduction. Under different jet flow conditions, there is a heat flow reduction effect downstream of the jet flow, and the heat flow reduction area covers the cone section and extends to the column section. .

The present invention adopts following technical scheme:

A method for drag reduction and heat protection by forward jet flow for a hypersonic pointed-cone aircraft, wherein a jet flow drag reduction and heat protection system is arranged on the wall of the windward surface of the aircraft, and the jet flow drag reduction and heat protection system includes a plurality of jets. A pipe, the nozzle conducts a forward jet along the inflow direction of the windward surface wall of the aircraft.

Further, the nozzle is a sonic or supersonic nozzle.

Further, the nozzles are evenly arranged along the circumference of the sharp cone to form an array covering the circumferential range, and the coverage angle range accounts for 50% to 100% of the angle range of the windward surface. The direction is at an acute angle.

Further, the nozzles are arranged along the extension direction of the fuselage or the wing to form an array covering the spanwise range, the coverage angle range accounts for 50% to 100% of the windward angle range, the nozzle axis and the wall tangent plane and the local flow of the nozzle. The direction is at an acute angle.

Further, the minimum outlet static pressure of the nozzle is greater than the wall pressure of the aircraft around the nozzle arrangement when there is no jet flow, and the maximum outlet static pressure of the nozzle should ensure that the shock wave generated by the interference does not fall off the body and avoid spraying. The flow causes the upstream flow to separate.

Further, the jet outlet Mach number is 1-2 Mach, and the jet static pressure ratio is 10-40.

Further, determining the outlet static pressure and the total outlet area of the nozzle includes the following steps:

(1) Determine the drag reduction value D to be achieved by the jet drag reduction and heat protection system in each flight profile design point of the aircraft, and give the estimated jet drag reduction amplification factor K , K> 1, to obtain the required jet flow Vacuum net thrust F= D/K ;

(2) Determine the working fluid mass consumption m of the jet drag reduction and heat protection system and the working time t of the jet drag reduction and heat protection system in the whole process of the flight profile, and obtain the jet flow rate Q=m/t ;

(3) Determine the outlet static pressure p of the nozzle and the total area A of the nozzle outlet according to the jet vacuum net thrust F and the jet flow Q ;

(4) According to the total outlet area A of the nozzles, determine the number of nozzle layouts, the outlet area of each nozzle, the nozzle layout position, and the nozzle axis direction. The nozzle layout is circumferential or spanwise. The outlet static pressure of the nozzle is p ;

(5) After the initial design of the jet drag reduction and heat protection system is obtained according to steps (1)-(4), in order to meet the overall design requirements of the aircraft, the design parameters of the jet drag reduction and heat protection system are carried out on the basis of numerical calculation or experiment. Iterative optimization to determine the final scheme of the jet drag reduction and heat protection system.

Further, the step (3) is specifically:

（1）

(1)

Among them, F is the jet vacuum net thrust, p is the outlet static pressure of the nozzle, A is the total area of the nozzle outlet, γ is the specific heat ratio of the given working medium, M is the Mach number of the given design jet outlet, M ≥ 1;

（2）

(2)

Among them, Q is the jet flow rate, p ₀ is the total pressure at the nozzle inlet, A is the total area of the nozzle outlet, q ( M ) is the flow coefficient, R is the gas constant of the jet working fluid, and γ is the given working fluid Specific heat ratio, T ₀ is the total working temperature of a given jet;

（3）

(3)

（4）

(4)

Simultaneous formulas (1)-(4) are used to determine the outlet static pressure p of the nozzle and the total area A of the nozzle outlet.

The beneficial effects of the present invention relative to the prior art:

(1) The arrangement position of the existing active method is limited to the head of the aircraft, and the scope of application of the present invention is extended to most areas of the windward side of the aircraft.

(2) The existing active method is applicable to the shape of the aircraft being limited to a blunt-head configuration. The present invention is suitable for a pointed-cone aircraft with a small head bluntness, and according to the shape characteristics, the shape of the jet drag reduction and heat protection system is carried out. Size and working parameter settings.

(3) For different aircraft, the ratio of piezoresistance to frictional resistance is different. The drag reduction mechanism of existing active methods is to reduce the piezoresistance caused by strong shock waves. On the other hand, the present invention can reduce piezoresistance and frictional resistance respectively by different mechanisms, and can adjust different drag reduction structures through design, and has a wider application range.

(4) The present invention can play the role of heat protection while realizing the jet flow drag reduction. Under different jet flow conditions, there is a heat flow reduction effect downstream of the jet flow, and the heat flow reduction area covers the cone section and extends to the column section.

Description of drawings

Figure 1 is a schematic diagram of the reference shape of the aircraft, wherein 1 is the reference shape of the aircraft;

Figure 2 is an enlarged schematic diagram of the head of the aircraft with a nozzle shape, wherein 2 is the shape of the aircraft with a nozzle;

Fig. 3 is the wall pressure distribution diagram of the aircraft under different jet flow conditions obtained by CFD numerical calculation in Example 1, the abscissa is the geometric coordinate with the reference shape head vertex as the origin, the unit is m, and the ordinate is the wall pressure and come ratio of hydrostatic pressure;

Fig. 4 is the distribution diagram of the coefficient of friction on the wall of the aircraft under different jet flow conditions obtained by CFD numerical calculation in Example 1, and the abscissa is the geometric coordinate with the reference shape head vertex as the origin;

Fig. 5 is the heat flow distribution diagram on the wall surface of the aircraft under different jet flow conditions obtained by CFD numerical calculation in Example 1, and the abscissa is the geometric coordinate with the reference shape head vertex as the origin;

FIG. 6 is a schematic diagram of the arrangement of nozzles in Embodiment 2. FIG.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments, and it should be understood that the following embodiments are intended to facilitate the understanding of the present invention, but do not have any limiting effect on it.

The present invention is a method for drag reduction and heat protection of forward jet flow for a hypersonic pointed cone aircraft. A plurality of nozzles are included, and the nozzles carry out co-flow jets along the incoming flow direction of the windward side wall of the aircraft.

Preferably, the nozzle is a sonic or supersonic nozzle.

Nozzles are arranged on the wall of the windward face of the aircraft, and a plurality of nozzles are evenly arranged along the circumference of the pointed cone to form an array covering the circumferential range. The coverage angle range accounts for 50% to 100% of the windward face angle range. The tangent plane of the wall and the direction of the incoming flow from the nozzle form an acute angle.

For the fuselage or wing of the aircraft with a flat shape such as wing or wing body fusion or waverider, arrange the nozzles along the extension direction of the fuselage or wing to form an array covering the spanwise range, and the coverage angle range accounts for the windward side The angle range is 50%~100%, and the axis of the nozzle forms an acute angle with the tangent plane of the wall surface and the local flow direction of the nozzle.

Preferably, for the jet of the nozzle, the minimum outlet static pressure of the nozzle is controlled according to the flight environment pressure, so that the jet is in an under-expanded working state, that is, the minimum outlet static pressure of the nozzle is greater than the flow around the aircraft when there is no jet The wall pressure at the nozzle arrangement position; control the jet static pressure ratio (nozzle outlet static pressure/incoming static pressure) within a certain range, and the maximum outlet static pressure of the nozzle should ensure the shock wave generated by the interference It does not fall off the body and avoids the upstream flow separation caused by the jet flow, which will cause adverse interference.

The jet is in an under-expanded state, and the piezoresistance of the downstream wall of the nozzle outlet is reduced by free expansion. The jet flow interferes with the incoming flow, and a low-pressure interference area is generated downstream of the jet flow, which further reduces the wall piezoresistance. In addition, the jet forms a gas film on the wall, and by changing the boundary layer velocity profile, the wall velocity gradient is reduced, thereby reducing the wall friction; the gas film changes the composition of the gas components in the boundary layer. The working fluid can further reduce the wall friction.

Preferably, the nozzle design of the jet drag reduction and heat protection system needs to determine all the parameters of the nozzle, including the total temperature of the jet outlet, the Mach number of the jet outlet, the specific heat ratio of the working medium, the outlet static pressure and the outlet area of the nozzle five parameters. Considering the overall design requirements of the aircraft, the two constraints of jet flow and jet flow rate are directly given, and the remaining two parameters need to be determined after three parameters are given. Among the five parameters, the adjustment space of temperature, Mach number and specific heat ratio is relatively Therefore, the required outlet static pressure and outlet area of the nozzle are given by calculation, which has better engineering application significance.

Specifically, determining the outlet static pressure and the total outlet area of the nozzle includes the following steps:

(1) Determine the drag reduction value D that the jet drag reduction and heat protection system needs to achieve in each flight profile design point of the aircraft, and given the estimated jet drag reduction amplification factor K, K> 1, the value of K is (1.0 , 3.0] is optimal, and the required jet vacuum net thrust F = D / K is obtained;

(2) Determine the working fluid mass consumption m of the jet drag reduction and heat protection system and the working time t of the jet drag reduction and heat protection system in the whole process of the flight profile, and obtain the jet flow rate Q=m/t ;

(3) Determine the outlet static pressure p of the nozzle and the total area A of the nozzle outlet according to the jet vacuum net thrust F and the jet flow Q , specifically:

According to the overall design requirements of the aircraft, given the total working temperature T ₀ of the jet, room temperature can be taken when the gas source is compressed gas, and the total working temperature of the engine can be taken when the gas source is the engine bleed air; given the specific heat ratio γ of the working medium, for the dual Molecular gas is usually γ = 1.4; given the design jet outlet Mach number M , M ≥ 1, M = 1 is optimal.

The jet vacuum net thrust F can be expressed as:

（1）

(1)

where F is the jet vacuum net thrust, p is the static pressure at the nozzle outlet, A is the total area of the nozzle outlet, γ is the specific heat ratio of the given working medium, and M is the Mach number at the given design jet outlet;

The jet flow Q can be expressed as:

（2）

(2)

In the formula, Q is the jet flow; p0 is the total pressure _at the nozzle inlet; A is the total area of the nozzle outlet; q ( M ) is the flow coefficient, which is equal to the ratio of the critical area to the outlet area of a single nozzle, where the critical area is The area is the cross-sectional area where the velocity of sound is the speed of sound in the nozzle flow, which is approximately the cross-sectional area of the throat; R is the gas constant of the jet working fluid; γ is the specific heat ratio of the given working fluid; T ₀ is the working total of the given jet temperature.

（3）

(3)

（4）

(4)

Simultaneous formulas (1)-(4) are used to determine the outlet static pressure p of the nozzle and the total area A of the nozzle outlet.

(4) According to the total outlet area A of the nozzles, determine the number of nozzle layouts, the outlet area of each nozzle, the nozzle layout position, and the nozzle axis direction. The nozzle layout is circumferential or spanwise. The outlet static pressure of the nozzle is p ;

(5) After the initial design of the jet drag reduction and heat protection system is obtained according to steps (1)-(4), in order to meet the overall design requirements of the aircraft, the design parameters of the jet drag reduction and heat protection system are carried out on the basis of numerical calculation or experiment. Iterative optimization to determine the final scheme of the jet drag reduction and heat protection system.

The following is a further description through Examples 1 and 2. The selected reference shape of the aircraft is shown in Figure 1. The overall length of the aircraft is 7m, the length of the cone section is 3.6m, the length of the column section is 3.4m, the diameter of the column section is 750mm, and the radius of the head passivation is 750mm. is 30mm.

Example 1:

Determine the position and size of the nozzle arrangement on the aircraft. For this kind of hypersonic pointed-cone aircraft with small head bluntness, sonic/supersonic nozzles are arranged on the windward wall surface to form an array covering a circumferential 360° range. The flow direction is at a smaller acute angle. As shown in Figure 2, the angle between the nozzle axis and the tangential plane of the wall is 10°, the nozzles are evenly arranged in the circumferential direction of the aircraft column, the nozzle outlet width is 5mm, and the axial distance between the nozzle outlet center and the aircraft head is 233mm .

The incoming flow is air, the incoming flow Mach number is 6, the incoming flow pressure is 101325Pa, and the incoming flow static temperature is 300K; the working fluid of the jet flow is hydrogen, the Mach number of the jet flow outlet is 1, 2, and the jet flow static pressure ratio (the outlet static pressure of the nozzle) Pressure/incoming static pressure) is 10, 20, 40, the total temperature of the jet outlet is 300K, the aircraft is set to the isothermal wall surface, and the wall temperature is 300K.

The pressure distribution of the aircraft wall under different jet flow conditions obtained by CFD numerical calculation is shown in Figure 3, and the friction coefficient distribution of the aircraft wall under different jet flow conditions obtained by CFD numerical calculation is shown in Figure 4. Figure 3 shows that there are local low pressure interference areas downstream of the jet under different jet conditions. Figure 4 shows that there is friction reduction in the downstream of the jet under different jet conditions. The drag reduction area covers the cone section and extends to the column section. The results in Fig. 5 show that there is a heat flow reduction downstream of the jet flow under different jet flow conditions, and the heat flow reduction area covers the cone section and extends to the column section.

The jet drag reduction amplification factor K is the ratio of the aircraft drag reduction to the jet vacuum net thrust, which is used to evaluate the jet drag reduction effect. K = 1 indicates that the jet drag reduction scheme has the same effect as the jet directly used as thrust, and K > 1 It shows that the jet drag reduction scheme can obtain additional favorable interference compared with the jet as thrust directly. Specifically as follows:

（5）

(5)

In the formula, F _on is the force in the direction of drag of the aircraft when the jet is used, F _off is the force in the direction of the drag of the aircraft when the jet is not used, and F _j is the net thrust of the jet vacuum.

Table 1 shows the reduction and amplification factors of the aircraft drag obtained by numerical integration. With the increase of jet outlet Mach number and jet static pressure ratio, drag reduction is more significant, but the amplification factor decreases. The results show that the drag reduction effect of the forward jet drag reduction scheme in this example is remarkable. Under the conditions that the Mach number of the jet outlet is 1 and the jet static pressure ratio is 40, the resistance can be reduced by 16.49% of the total resistance, which has a relatively high performance. With a high amplification factor (1.7947), it can be considered that the output of the jet drag reduction scheme is greater than the input.

Table 1

Example 2:

The position of the nozzle, the width of the outlet, and the direction of the jet are the same as those in Example 1. The arrangement of the nozzles is shown in Figure 6. The nozzles with an angle of 22.5° are arranged at intervals of 45°. The total number of nozzles is 8, forming an array covering a range of 180° in the circumferential direction. The total outlet area of the nozzles is that of Example 1. half. In the calculation conditions, the incoming flow conditions, the working fluid of the jet, the total temperature of the jet outlet and the wall temperature are the same as those in Example 1, the Mach number of the jet outlet is 1, and the static pressure ratio of the jet is 40. The results show that the piezoresistance is reduced by 4.51%, The total resistance is reduced by 10.31%, the piezoresistance is reduced by 43.69%, and the amplification factor is 2.1064.

The results of this nozzle arrangement are similar to the results in Example 1 where the jet outlet Mach number is 1 and the jet static pressure ratio is 20, indicating that under the same jet flow and vacuum net thrust conditions, different nozzle arrangements can A considerable drag reduction effect is achieved, that is, the forward jet flow drag reduction and heat prevention method proposed by the present invention can adjust the nozzle arrangement to suit the actual application requirements under the premise of ensuring the drag reduction effect.

For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can also be made to the embodiments of the present invention, which all belong to the protection scope of the present invention.

Claims (5)

1. A forward jet flow resistance-reducing and heat-preventing method for a hypersonic pointed cone aircraft is characterized in that a jet flow resistance-reducing and heat-preventing system is arranged on the wall surface of the windward side of the aircraft, the jet flow resistance-reducing and heat-preventing system comprises a plurality of jet pipes, the jet pipes jet in a forward direction along the incoming flow direction of the wall surface of the windward side of the aircraft, the pressure resistance and the friction resistance can be effectively reduced, the jet flow resistance-reducing effect is achieved, the downstream of the jet flow has a heat flow reducing effect under different jet flow conditions, and a heat flow reducing area covers a cone section and extends to a column section;

the spray pipe is a sonic or supersonic spray pipe;

the spray pipes are uniformly distributed along the circumferential direction of the conical section of the pointed cone to form an array coverage circumferential range, the coverage angle range accounts for 50% -100% of the angle range of the windward side, and the axis of each spray pipe forms an acute angle with the wall tangent plane and the local incoming flow direction of each spray pipe.

2. The forward jet flow resistance-reducing and heat-preventing method for the hypersonic pointed cone aircraft as claimed in claim 1, wherein the minimum outlet static pressure of the jet pipe is greater than the wall pressure of the aircraft bypass flow at the position where the jet pipe is arranged when no jet flow exists, and the maximum outlet static pressure of the jet pipe ensures that the shock wave generated by interference does not fall off and the upstream flow separation caused by the jet flow is avoided.

3. The method of forward jet flow drag reduction and heat protection for hypersonic nose cone vehicles according to claim 1, wherein jet exit mach number is in the range of mach 1-2 and jet static pressure ratio is in the range of 10-40.

4. The forward jet drag reduction and thermal protection method for hypersonic nose cone vehicles according to claim 1, wherein determining the static exit pressure and the total exit area of said nozzle comprises the steps of:

(1) determining the resistance reduction value to be achieved by the jet flow resistance reduction and heat protection system in each flight section design point of the aircraftDGiving estimated jet flow drag reduction amplification factorK，K>1, obtaining the required jet vacuum net thrustF= D/K；

(2) Determining the working medium quality consumption of a jet flow resistance-reducing and heat-proof system in the whole process of flight profilemAnd working time of jet flow anti-drag heat-proof systemtTo obtain the flow rate of the jet flowQ=m/t；

(3) Vacuum net thrust based on jet flowFAnd jet flow rateQDetermining outlet static pressure of nozzlepAnd total area of the outlet of the nozzleA；

(4) According to the total area of the outlet of the nozzleADetermining the arrangement number of the spray pipes, the outlet area of each spray pipe, the arrangement position of the spray pipes and the axial direction of the spray pipes, wherein the spray pipes are arranged along the circumferential direction, and the outlet static pressures of the spray pipes are allp；

(5) After the initial design of the jet flow anti-drag heat protection system is obtained according to the steps (1) to (4), in order to meet the overall design requirement of the aircraft, iterative optimization is carried out on the design parameters of the jet flow anti-drag heat protection system on the basis of numerical calculation or experiment, and the final scheme of the jet flow anti-drag heat protection system is determined.

5. The forward jet flow resistance-reducing and heat-preventing method for the hypersonic pointed cone aircraft according to claim 4, wherein the step (3) is specifically as follows:

（1）

wherein,Fin order to jet the vacuum net thrust,pis the static pressure at the outlet of the spray pipe,Ais the total area of the outlet of the spray pipe, gamma is the specific heat ratio of a given working medium,Mfor a given design jet exit mach number,M≥1；

（2）

wherein,Qin order to jet the flow rate of the liquid,p ₀ the total pressure of the inlet of the spray pipe is,Ais the total area of the outlets of the spray pipes,q(M) In order to be the flow coefficient,Ris the gas constant of the jet flow working medium, gamma is the specific heat ratio of the given working medium,T ₀ total temperature for a given jet operation;

（3）

（4）

simultaneous equations (1) - (4) for determining outlet static pressure of nozzlepAnd total area of the outlet of the nozzleA。

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