RU2145563C1 - Method of control of aerodynamic loads acting on aircraft compartments and device for realization of this method (versions) - Google Patents

Abstract

FIELD: rocketry. SUBSTANCE: method is based on change of pressure of gas medium in compartment relative to pressure on its surface through efflux of gas medium from compartment at action of aerodynamic flow. Change in pressure inside compartment is preliminarily determined by the flight trajectory. Efflux of gas medium is effected to local zone of surface at outside pressure equal to pressure inside compartment in mode of maximum pressure drops in the flight trajectory. In some versions, device have drainage holes whose positions are selected taking into account gradient of change of outside pressure in the flight trajectory; effective area is selected taking into account volume of compartment occupied by gas medium, flow coefficient of drainage hole and maximum drop of pressure between cavity of compartment and outside pressure. EFFECT: enhanced strength. 4 cl, 9 dwg

Description

 The invention relates to the field of aerodynamics of aircraft (LA) and can be used in rocket science and aviation in determining and regulating aerodynamic loads acting on a compartment, its elements (shell, mounting, technological hatches and other elements) and products (payload blocks, payloads (GH), control system automation units, etc.) located in the compartment.

 Known and widely used in rocket science is a method for regulating aerodynamic loads (pressure drops per unit area of a structure) acting on an aircraft compartment, including a change in the pressure of the gaseous medium inside the compartment, for example, a sealed fuel tank [1] of a launch vehicle (LV), sealed compartments of an airplane [2] or an orbital ship. (OK) "Buran" [3], launched by the launch vehicle (LV), in relation to the pressure on its surface by blowing a gaseous medium into a closed volume under the influence of an aerodynamic flow.

 According to these technical solutions, the positive gas pressure in relation to the outside is realized in the compartment necessary to pressurize the airtight tank, compartment or module of the aircraft, which leads to significant loads acting on the structural elements of the compartment along the flight path of the aircraft.

 Also known in rocket science is a method for regulating aerodynamic loads acting on an aircraft compartment, including changing the pressure of the gaseous medium inside the enclosed volume of the compartment, for example, the space head part (CGP) of the launch vehicle [4] with respect to the pressure on its surface by the outflow of the gaseous medium into the atmosphere when exposed to aerodynamic flow.

 The disadvantages of this technical solution include the disordered movement of the gas medium inside the compartment, due to the presence of technological holes with a substantially uneven distribution of external pressure along the length of the compartment, which leads to an uneven distribution of pressure drops along the length of the compartment. Since a pressure equal to atmospheric pressure is adopted inside a closed container [5], which reduces the reliability of obtaining aerodynamic loads.

 Also known in rocket science is a method for regulating aerodynamic loads acting on an aircraft compartment, including changing the pressure of the gaseous medium inside the compartment, for example, the payload compartment of the Buran OK [6], with respect to the pressure on its surface by the outflow of the gaseous medium into the atmosphere when exposed aerodynamic flow.

 This technical decision was made by the authors for the prototype. The given technical solution, in comparison with analogues, allows to reduce aerodynamic loads acting on the compartment due to equalization of pressure inside the compartment compared to the outside. The disadvantages include the disordered flow of a gaseous medium in a closed volume, which leads to a decrease in the accuracy of determining aerodynamic loads.

 A device for regulating aerodynamic loads acting on an aircraft compartment, for example, on a sealed fuel tank [1] LV, an airtight compartment of an airplane [2] or OK "Buran" [3], containing a shell of the compartment, a system for supplying and regulating the pressure of the gas medium in a closed compartment volume.

 The disadvantages of the technical solution include significant loads acting on the structural elements of the compartment along the flight path. In addition, to ensure the required pressure in the sealed compartment, a pressurization and control system is installed according to a predetermined pressure change program for the normal functioning of the compartments, which leads to an increase in the weight of its structure.

 A device is known for regulating aerodynamic loads acting on an aircraft compartment, for example, a compartment of the GC OK "Buran" [6], containing a compartment shell, drainage holes made in the compartment shell, sashes installed in drainage holes, an actuator and a sash control system.

 This technical decision was made by the authors for the prototype device.

 The flaps are designed to reduce loads by balancing the pressures acting inside and outside the compartment with a control system with actuators for closing and opening drainage holes along the flight path in accordance with the shutter operation sequence fixed for this path. This leads to a complication of the compartment design, and also necessitates the attachment of the cyclogram to the calculated trajectory. This reduces the operational capabilities of the technical solution.

 Since the drainage holes are located at different distances along the length of the compartment, due to the uneven distribution of pressure outside the compartment, especially significant at transonic flight speeds, local flows inside the compartment may occur, which can lead to unacceptable loads acting on the products located inside the compartment, for example GHG elements.

 The objective of the invention is to increase the accuracy of regulation of aerodynamic pressures along the flight path of an aircraft and, as a result, to ensure that aerodynamic loads acting on the compartment and products placed in the compartment are specified from the strength conditions, while simplifying the design for implementing the regulation method.

The technical result of the invention is:
- providing aerodynamic loads specified from the strength conditions acting on the compartment and at the same time on products placed in the compartment, due to changes in the path of the gas medium from the compartment to the local area of the compartment surface;
- increasing the reliability of determining aerodynamic loads by determining the pressure of the gas medium in the compartment along the flight path of the aircraft;
- simplification of the compartment design by eliminating trajectory-controlled devices for ensuring equalization of pressure outside and inside the compartment.

 The technical result is achieved by the fact that in the proposed method of regulating aerodynamic loads acting on the compartment of the aircraft, including changing the pressure of the gas medium in the compartment with respect to the pressure on its surface by the outflow of the gas medium from the compartment when exposed to the aerodynamic flow, according to the invention, previously along the flight path determine the change in pressure inside the compartment, and the outflow of the gas medium is carried out in the local zone of the surface of the compartment with an external pressure equal to The pressure inside the chamber, at the time of the flight trajectory of the aircraft maximum differential pressure.

где S, см² - площадь дренажного отверстия,
V, м³ - объем отсека, занимаемый газовой средой,
μ - коэффициент расхода дренажного отверстия,
ΔP_вн. , кГс/см² - максимальный по траектории перепад давлений между полостью отсека и наружным давлением;
a, b, c, d - коэффициенты, зависящие от параметров траектории летательного аппарата.In the device (option 1) for regulating aerodynamic loads acting on an aircraft compartment containing a shell, on the side surface of which a drainage hole is made, according to the invention, a drainage hole is made in a local area of the compartment surface with predetermined coordinates corresponding to a minimum gradient of external pressure change along the flight path while the effective area of the drainage hole, related to the volume of the compartment occupied by the gas medium, is determined from the ratio:

where S, cm ² - the area of the drainage hole,
V, m ³ - the volume of the compartment occupied by the gaseous medium,
μ is the discharge coefficient of the drainage hole,
ΔP _ext. , kgf / cm ² - maximum path differential pressure between the compartment cavity and external pressure;
a, b, c, d - coefficients depending on the parameters of the trajectory of the aircraft.

 In the device (option 2) for regulating the aerodynamic loads acting on the aircraft compartment, in contrast to option 1, according to the invention, a device for separating the aerodynamic flow is mounted in the drainage hole or its vicinity.

 The aerodynamic flow separation device can be made in the form of an aerodynamically profiled superstructure with a drainage hole on its surface connected to a drainage hole of the shell.

 The invention provides aerodynamic loads specified from strength conditions acting on the compartment along the flight path, while increasing the reliability of determining the loads due to changes in the pressure of the gas medium in the compartment and the nature of its change along the flight path, as well as determining the coordinates and effective area of the drainage hole to achieve these loads .

 The essence of the invention is illustrated by examples of solving the problem with reference to the compartment of the aircraft mounted behind the head part of the launch vehicle with the product placed in it, for example, the steam generator unit.

 In FIG. Figures 1 and 2 show the compartment diagrams, made respectively according to option 1 with a cylindrical part and according to option 2, with a conical part of the compartment. Here, arrows indicate the direction of flow of the gas medium.

1 - compartment;
2, 4, 6 - drainage holes;
3 - expanding (tapering) part;
5 - add-in.

In FIG. Figure 3 shows the distribution of the coefficient Cp of excess external pressure along the length of the compartment at M = 1 for these options. Here Cp = ΔP _nar. / q, where q is the velocity head.

 In FIG. Figure 4 shows the change in the coefficient Cp by the numbers M at the characteristic points of the compartment made in option 1 (vols. A, a1, a2) and in option 2 (vols. B, b1, b2), and also the areas of drainage holes for these options are highlighted .

In FIG. Figure 5 shows a typical change in the flight time of the limiting differences ΔP acting on the compartment, in comparison with the permissible ΔP _add. , as well as the components of the differences ΔP _nar. , ΔP _ext. Here ΔP _nar. = P _nar. - P _n , ΔP _int. = P _nn - P _n , where P _n - atmospheric pressure.

In FIG. 6 shows the change in overpressure inside the compartment ΔP _ext. in time at different relative passage areas of the drainage hole S. Here S is the area of the drainage hole, referred to the volume of the compartment occupied by the gas medium.

In FIG. 7 shows a generalized dependence of the maximum pressure ΔP _ext. from the relative area S.

In FIG. 8 shows the pressure dependencies P _nar. , P _ext. and their differences acting on the compartment along the flight path of the LV.

 In FIG. Figure 9 shows similar dependences along the descent trajectory of an aircraft.

 The PH compartment (Figs. 1 and 2) contains a shell 1 with power elements, on the lateral surface of which a drainage hole 2 or 4 is made. The shell 1 may have an expanding (or tapering) part 3.

According to option 1 (Fig. 1), the drainage hole 2 is made in the local area of the compartment surface (node I) with coordinates corresponding to the minimum gradient of the external pressure ΔP _nar. along the flight path (Fig. 4, zone a1-a2).

 According to option 2 (Fig. 2), an aerodynamically profiled superstructure 5 (assembly II) is installed in the drainage hole 4 located on the surface of the compartment with coordinates different from option 1. The add-in is selected from a number of add-ons, allowing you to change the pressure in the local area on the surface of the compartment and, therefore, the pressure inside the compartment. It can be performed, for example, in the form of a hollow aerodynamic superstructure installed in the vicinity of this drainage hole (unit II, 7, 8), or in the drainage hole 4 of the compartment (unit II, 9, 10). Its drainage hole 6 is made on the side or bottom surface of the superstructure and communicated with the drainage hole 4 of the shell placed in the superstructure.

The introduction of the add-in is due to the peculiarity of changing the plot ΔP _bunks. along the length of the compartment, along which to establish the local zone of the outflow of the gaseous medium with the required pressure ΔP _int. in order to achieve the given differences ΔP along the trajectory, at the same time having fulfilled the design requirements, it is not possible or necessary to combine a drainage hole, for example, with the thermostatic system piping, which must be mounted in the required section of the compartment. Depending on the characteristics of the distribution ΔP _nar. the drainage hole 4 can be made both on the generatrix with zero, and negative or positive angle of inclination to the axis of the compartment.

 A drainage hole 4 is also performed in the local area of the compartment surface with coordinates corresponding to the minimum gradient of the external pressure change along the flight path (Fig. 4, zone b-b2).

 The effective area of the drainage holes 2, 4 or 6 is determined by the formula (1).

 The proposed method for controlling the pressure drop ΔP and, therefore, aerodynamic loads acting on the compartment and its elements along the flight path, on the side surface of which a drainage hole is made, is implemented as follows.

Preliminarily, for the entire range of changes in the numbers M, the distribution of the external pressure ΔP _nar. along the length of the compartment. In FIG. 3 for options 1 (version 1) and 2 (version 2) illustrates the distribution of the pressure coefficient C _p along the length of the compartment, for example, at M = 1.

For the prototype, when determining ΔP (ΔP = ΔP _nar. -ΔP int _. ) Acting on the compartment, the pressure in the compartment along the flight path is taken equal to atmospheric ΔP _int. = 0 (see [6]). Thus, the reliability of determining the loads is reduced.

 To solve the problem, according to the results of studies of the pressure distribution for all numbers M, the pressure change is established at the characteristic points of the compartment and the coordinates of the local zone corresponding to the minimum gradient of the pressure change along the path are determined from it (Fig. 4). From FIG. 4 it follows that the coordinates of zone a1-a2 for option 1 and zone b1-b2 for option 2 meet this requirement in comparison with the change in pressure, for example, in t. A and t. B, respectively, for these options.

The path extreme differences ΔP _{bunk are} also determined _. taking into account changes in angles of attack and roll. Further, based on the given restrictions on permissible pressure drops ΔP _add. acting on the elements of the compartment, determine the maximum levels of differences ΔP _ext. necessary to ensure the differences ΔP, acting along the trajectory, and not exceeding the permissible (Fig. 5). In FIG. 5 illustrates the change in these differences.

In accordance with the invention, for the calculated trajectory for the selected drainage hole with coordinate li, dependencies of excess pressure inside the compartment ΔP _ext. by flight time with a different area of the drainage hole S (Fig. 6). Moreover, ΔP _ext. determined using the pressure in the local zone on the surface of the compartment with coordinate li, at the place of the outflow of the gas medium into the atmosphere, taking into account interference with the aerodynamic flow. Their extreme values are also revealed. From FIG. 6 it follows that the dependence ΔP _ext. from time to time along the trajectory has a characteristic maximum corresponding to transonic flight speeds.

In FIG. 7, for the calculated trajectory, the generalized dependence (ΔP _ext. ) On S established using the results of these studies is shown using the grid of dependencies shown in FIG. 6, and its mathematical description is given in the form of formula (1). In this formula, a, b, c, d are coefficients that depend on the parameters of the trajectory (number M, flight altitude H).

For the compartment made in embodiment 1 (Fig. 1), the change in pressure drop ΔP is carried out by the outflow of the gas medium into the local area of the compartment surface through the drainage hole 2, while the outflow of the gas medium is realized in the zone a1-a2 with an external pressure ΔP of the _bunk. equal to the pressure inside the compartment ΔP _ext. at the mode of maximum pressure drops along the flight path.

Similarly, for the compartment made in option 2 (Fig. 2), the change in ΔP is carried out by the outflow of the gaseous medium through the drain holes 4 or 6 (depending on the option of the superstructure), while the outflow of the gaseous medium is realized in zone b1 - b2 with an external pressure ΔP _Nar equal to the pressure inside the compartment ΔP _ext. at the mode of maximum pressure drops along the flight path.

Depending on the need to increase or decrease ΔP _ext. along the path, the outflow is carried out through openings 2, 4 or 6, respectively, with a greater or lesser pressure on the surface of the compartment, or a smaller or larger area of the drainage hole S.

 This ensures that the specified maximum ΔP1 and minimum ΔP2 excess pressures along the flight path and, accordingly, aerodynamic loads acting on the compartment and its elements are not exceeded.

In FIG. Figure 8 illustrates the change in the differences ΔP1 and ΔP2 acting on the compartment at different points in time along the flight path of the LV compared to the pressure inside the compartment P _ext. and atmospheric P _n . The data were obtained for a compartment with a volume of gas medium V = 50 m ³ , a drainage hole 2 or 4 with an area S = 30 cm ^{2 was made in it} .

 Thus, along the flight path of the launch vehicle, aerodynamic loads specified from the conditions of strength are realized, acting on the compartment elements and the products placed in it. At the same time, they increase the reliability of operation of the structural elements of the compartment and products placed in the compartment, as well as simplify the design of the compartment by eliminating trajectory-controlled devices for providing pressure changes inside the compartment.

The technical solution can be used to control aerodynamic loads acting on the compartment in the aircraft launch site. Moreover, in the formula (1) the sign of ΔP _ext. should be reversed. In FIG. 9 illustrates the change in the differences ΔP3 and ΔP4 acting on the compartment compared to P _ext. and P _n , on the descent section of the aircraft.

 The technical solution can be used to determine the allowable area of technological gaps at the junction of the structural elements of the compartment with each other using the formula (1).

 The presented technical solution can also be used in aviation, for example, in aircraft construction, in solving the problems of transporting goods of various purposes placed in unpressurized compartments of the aircraft.

 Currently, the proposed technical solution is being implemented in aircraft developed by the enterprise and is an obligatory element of aerodynamic design.

Sources of information
1. Cosmonautics. Encyclopedia. Ed. V.P. Glushko.- M.: Sov. Encyclopedia, 1985, p. 339.

 2. Aviation. Encyclopedia. -M .: TsAGI, 1994, p. 397.

 3. The space complex. Reusable orbiter "Buran". Ed. Yu.P. Semenova, G.E. Lozino-Lozinsky, V.L. Lapygina, V.A. Timchenko. - M.: Mechanical Engineering, 1995, pp. 223-225.

 4. Fundamentals of designing spacecraft launch vehicles. Ed. Acad. V.P. Mishin and prof. VK. Carrasque -M .: Engineering, 1991, pp. 187-190.

 5. The basics of designing spacecraft launch vehicles. Ed. Acad. V.P. Mishin and prof. VK. Carrasque -M.: Engineering, 1991, p. 290.

 6. The space complex. Reusable orbiter "Buran". Ed. Yu. P. Semenova, G.E. Lozino-Lozinsky, V.L. Lapygina, V.A. Timchenko. -M.: Engineering, 1995, p. 148-150.

 7. A. Pope, C. Heun. Wind tunnels of high speeds. -M.: Mir, 1968, p. 311-316.

Claims (4)

 1. The method of regulating aerodynamic loads acting on the compartment of the aircraft, including changing the pressure of the gaseous medium in the compartment relative to the pressure on its surface by the outflow of the gaseous medium from the compartment when exposed to an aerodynamic flow, characterized in that the change in pressure inside the flight path is determined compartment, and the outflow of the gas medium is carried out in the local zone of the compartment surface with an external pressure equal to the pressure inside the compartment at the maximum differential pressure occurrences along the trajectory of the aircraft flight. 2. Device for regulating aerodynamic loads acting on the compartment of the aircraft containing a shell, on the side surface of which a drainage hole is made, characterized in that the drainage hole is made in the local area of the compartment surface with predetermined coordinates corresponding to the minimum gradient of the external pressure change along the flight path while the effective area of the drainage hole, related to the volume of the compartment occupied by the gas medium, is determined from the ratio

where S is the area of the drainage hole, cm ² ;
V is the volume of the compartment occupied by the gas medium, m ³ ;
μ is the discharge coefficient of the drainage hole;
ΔP _ext. - the maximum path differential pressure between the cavity of the compartment and the external pressure, kgf / cm ² ;
a, b, c, d - coefficients depending on the parameters of the trajectory of the aircraft. 3. Device for regulating aerodynamic loads acting on the compartment of the aircraft, containing a shell, on the side surface of which a drainage hole is made with a device for detaching the aerodynamic flow, characterized in that the drainage hole is made in the local area of the surface of the compartment with predetermined coordinates corresponding to the minimum gradient of change external pressure along the flight path, while the effective area of the drainage hole, referred to the volume of the compartment occupied by the gas medium, determined from the ratio

where S is the area of the drainage hole, cm ² ;
V is the volume of the compartment occupied by the gas medium, m ³ ;
μ is the discharge coefficient of the drainage hole;
ΔP _ext. - the maximum path differential pressure between the cavity of the compartment and the external pressure, kgf / cm ² ;
a, b, c, d - coefficients depending on the parameters of the trajectory of the aircraft.  4. The device according to claim 3, characterized in that the aerodynamic flow separation device is made in the form of an aerodynamically profiled superstructure with a drainage hole on its surface connected to a drainage hole of the shell.

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