Highly compensated pressure stabilized aerial fire extinguishing liquid discharge device

Abstract

The present application relates to a kind of highly compensated aviation fire extinguishing liquid release device of stabilized voltage, belong to the technical field of liquid material release of aircraft in flight.The mechanical stabilized pressure valve is connected in series on the upstream of nozzle, two diaphragms in valve are rigidly connected, the effective area of second diaphragm is greater than first diaphragm, and the isolation cavity between two diaphragms is isolated by breathing hole and communicated with atmosphere;The outside of first diaphragm is feedback chamber communicated with the inlet side of nozzle, and the outside of second diaphragm is reference chamber.Reference chamber is connected to the part communicated with continuous liquid column by reference channel and the outlet side of ground liquid supply equipment, and reference pressure decreases with the increase of flight height.The force of reference pressure acting on second diaphragm is balanced with the sum of the force of feedback pressure acting on first diaphragm and spring force, so that the inlet pressure of nozzle decreases with the decrease of reference pressure, and the decreasing ratio is adjusted by the ratio of effective area of two diaphragms.Therefore, without height sensor and electric control circuit, the change rate of inlet pressure of nozzle with height can be adjusted by only one geometric quantity.

Description

Technical Field

[0001] This invention relates to a device for releasing liquid substances during flight of an aircraft, specifically to an aviation fire extinguishing liquid release device that continuously supplies liquid from a ground-based liquid supply device via a tethered liquid supply pipe and releases the fire extinguishing liquid to a target surface during flight. Background Technology

[0002] Delivering water or other liquid extinguishing agents directly from aircraft to high places or above fires that are difficult for personnel to access is a rapidly developing firefighting method in recent years. Due to takeoff weight limitations, the amount of extinguishing liquid carried by the onboard water tank is limited. Therefore, in situations requiring continuous liquid supply, ground-based fire trucks or pumping stations typically deliver the extinguishing liquid continuously to the onboard nozzles via a tethered supply hose that accompanies the aircraft into the air. The aircraft's role is only to position the nozzles and maintain their attitude.

[0003] This liquid supply method introduces an unavoidable physical constraint. There is always a liquid column in the vertical section of the tethered supply pipe, and the height of this column corresponds to the aircraft's hovering altitude. Taking water as an example, for every 1-meter change in hovering altitude, the static pressure at the nozzle changes by approximately 9.8 kPa; a 10-meter change in hovering altitude results in an increase or decrease of approximately 0.1 MPa at the nozzle. For fire extinguishing nozzles with a rated inlet pressure of only 0.6 to 1 MPa, this is not a negligible amount.

[0004] When an aircraft rises or falls a few meters in gusts of wind, or when an operator slightly adjusts its altitude by a few meters to avoid external structural components, the nozzle inlet pressure changes accordingly, the jet exit velocity changes, and the landing point shifts. Existing technologies offer two approaches to address this constraint.

[0005] The first approach involves pressure adjustment at the ground pump side, where the pump unit adjusts the outlet pressure according to the aircraft's altitude to replenish the static pressure of the liquid column. The difficulty lies in the fact that the flexible piping between the ground pump and the airborne nozzle is often over 30 meters long, exceeding 100 meters for ultra-high-altitude operations. The piping has volumetric elasticity, and the propagation and attenuation of pressure waves require time; by the time the adjustment reaches the nozzle, the aircraft has often already moved elsewhere. This approach can only compensate for slowly varying components and is ineffective against high-frequency fluctuations during hovering.

[0006] The second approach is to move the compensation mechanism onto the aircraft, installing an altitude sensor and an onboard booster pump. A cascade control loop calculates the jet pressure based on the measured altitude, and the onboard pump then supplements the pressure. While this does improve the response time, moving the pump, motor, sensor, controller, and power supply all into the air is costly for aircraft constrained by takeoff weight. Furthermore, if any component—controller, sensor, or onboard pump—fails, the pressure compensation is completely lost.

[0007] Another seemingly simpler approach is to connect a constant pressure-reducing valve upstream of the airborne nozzle. The diaphragm takes the feedback pressure from the nozzle inlet side and balances it with the preload of the pressure regulating spring, thus stabilizing the nozzle inlet pressure at the spring's set value. This approach requires no sensors or electronic controls and is lightweight. However, careful analysis of the operating conditions reveals that stabilizing the nozzle inlet pressure to a constant value does not equate to stabilizing the jet's landing point.

[0008] The reason is that there is a free-flowing jet between the nozzle on the aircraft and the fire on the ground. After the extinguishing liquid leaves the nozzle, the time it takes for it to fall onto the target surface depends on the nozzle's current altitude. As the hovering altitude increases, the jet's flight time in the air becomes longer, and even if the exit velocity is exactly the same, the point of impact will be pushed outward.

[0009] The inventor realized while calculating this free-flight phase that the problem wasn't pressure stability, but rather that the compensation force was implicitly set to zero. Changes in hovering altitude affect the landing point through two paths: one is the hydrostatic pressure of the liquid column altering the exit velocity, and the other is the altitude above the ground altering the flight time; these two paths act in opposite directions. The conventional pressure-reducing valve precisely cuts off the first path completely, so the landing point is then solely guided by the second path, only the drift direction changes from inward to outward. Completely stabilizing the pressure and completely destabilizing it are two sides of the same coin; neither is a solution for a stable landing point.

[0010] In existing aerial spraying, aerial firefighting, and tethered liquid supply platform solutions, pressure regulation methods primarily rely on electrically controlled pumps, pneumatic compression, nozzle selection, and ground pump pressure regulation. The role of mechanical valves is limited to stabilizing pressure. Furthermore, the use of purely mechanical means to treat compensation force as a variable adjustable according to operational conditions lacks a suitable technical approach. Therefore, a fire extinguishing liquid release device is needed that is installed on an aircraft, does not rely on altitude sensors or electronic control, and whose compensation force can be adjusted according to operational conditions. Summary of the Invention

[0011] The technical problem to be solved by this invention is divided into two levels. The first is how to make the inlet pressure of the airborne nozzle vary with flight altitude by a factor greater than 1, adjustable by geometric dimensions, without relying on altitude sensing and electronic control. Existing ground-based pump pressure regulation routes have sluggish responses, and airborne electronically controlled pressurization routes are heavy and have a high risk of failure. Conventional pressure-reducing valves stabilize the nozzle inlet pressure at a constant level. Commonly used proportional pressure-reducing valves determine the proportional coefficient based on the ratio of the inlet-side working area to the outlet-side working area; their outlet-side working area is larger than the inlet-side, resulting in an outlet pressure that is always lower than the inlet pressure, and the proportional coefficient is also less than 1. Neither of these methods provides this characteristic. The next step is to determine how to select this factor based on the jet's landing point conditions, thereby significantly reducing the sensitivity of the jet's landing point to small fluctuations in hovering altitude. This level is achieved by the tuning criteria given later. If the factor is not chosen correctly, the landing point drift may not reach its minimum, but the device itself will still operate according to the aforementioned factor.

[0012] To address the aforementioned problems, the present invention provides a highly compensated and pressure-stabilized aviation fire extinguishing liquid release device, comprising an airborne bracket for installation on an aircraft, a nozzle disposed on the airborne bracket, and a tethered supply pipe connecting the nozzle to a ground-based liquid supply device. An airborne mechanical pressure-stabilizing valve that rises and falls with the aircraft is connected in series upstream of the nozzle. The mechanical pressure-stabilizing valve comprises a valve body, a valve core, a pressure regulating spring, and a differential diaphragm assembly.

[0013] The differential diaphragm assembly includes a first diaphragm and a second diaphragm rigidly connected. The effective area of ​​the second diaphragm is larger than that of the first diaphragm. An isolation cavity is formed between the two diaphragms, which is connected to the atmosphere through a breathing hole. The side of the first diaphragm facing away from the isolation cavity is a feedback cavity connected to the inlet side of the nozzle through a feedback channel. The side of the second diaphragm facing away from the isolation cavity is a reference cavity connected to a reference pressure tapping part through a reference channel.

[0014] The reference pressure tapping point is connected to the outlet side of the ground-based liquid supply equipment by a continuous liquid column, so that the reference pressure in the reference chamber decreases as the aircraft's flight altitude increases.

[0015] The resultant force of the pressure on the inlet side of the mechanical pressure regulator acting on the valve core is zero in the direction of the valve core's movement. The differential diaphragm assembly is drivenly connected to the valve core. The force exerted by the reference pressure on the second diaphragm is inversely balanced by the sum of the force exerted by the pressure in the feedback chamber on the first diaphragm and the spring force of the pressure regulating spring, causing the nozzle inlet pressure to decrease as the reference pressure decreases. From this balance relationship, it can be seen that when the spring force can be considered constant within the valve core's adjustment stroke, the ratio of the change in nozzle inlet pressure to the change in reference pressure is equal to the ratio of the effective areas of the two diaphragms.

[0016] The core of the above solution lies in three points. First, the flight altitude information is extracted directly from the liquid column in the tethered supply line, instead of using a separate sensor. The reference pressure tap is connected to the outlet side of the ground-based liquid supply equipment by a continuous liquid column. The reference pressure naturally contains a negative value that is proportional to the hovering altitude. As the altitude increases, the reference pressure decreases, and the decrease is exactly equal to the increase in the hydrostatic pressure of the liquid column.

[0017] Secondly, the spring chamber in a conventional pressure-reducing valve that is open to the atmosphere is modified into a reference chamber that withstands this reference pressure. Furthermore, the spring's opening force, which is opposite to the outlet feedback pressure, is changed to a biasing force in the same direction. Therefore, the valve's setpoint is no longer a constant, but a quantity that moves with height. Thirdly, two rigidly connected diaphragms with unequal effective areas are used to amplify the reference pressure according to the area ratio before comparing it with the feedback pressure. Thus, the following force becomes a proportional coefficient determined by geometric dimensions and selectable during the design phase.

[0018] In one implementation, the device further includes a reference pipe laid parallel to the tethered supply pipe, the lower end of the reference pipe being connected to the outlet side of the ground supply equipment, the upper end of the reference pipe being a closed end connected only to the reference channel, the reference pressure tapping point being the upper end of the reference pipe, and the reference pipe having no continuous flow when the nozzle steadily releases the extinguishing liquid.

[0019] Since there is no flow inside the reference tube, there is no friction loss along the way. The obtained reference pressure is equal to the outlet pressure of the ground liquid supply equipment minus the static pressure of the liquid column. It is a clean signal that only varies with altitude, and the compensation ratio will not drift due to changes in the release flow rate.

[0020] As an alternative pressure tapping method, the reference pressure tapping point is the section of the tethered supply pipe located on the inlet side of the mechanical pressure regulating valve. The reference channel extends from this section and connects to the reference chamber along the outer wall of the valve body of the mechanical pressure regulating valve. The outlet orifice diameter of the nozzle is fixed, and the ground-based supply equipment operates at a constant outlet pressure. This pressure tapping method does not require the addition of a second pipeline, and the interface between the airborne and ground-based components remains unchanged. The trade-off is that the reference pressure contains a friction loss that varies with the flow rate. This loss can only be approximated as constant under the aforementioned conditions of fixed orifice diameter and constant pressure operation; therefore, it is a secondary option.

[0021] The value of the compensation ratio can be determined with clear criteria. The rated operating height is set as the vertical distance from the nozzle outlet to the horizontal target surface; the rated depression angle is the downward tilt angle of the nozzle axis relative to the horizontal plane; the outlet velocity is the outlet velocity of the nozzle at the rated operating height and rated depression angle under the rated inlet pressure; and the jet flight time is the time taken for the extinguishing liquid to travel from the nozzle outlet to the horizontal target surface under these conditions. The ratio of the effective area of ​​the second diaphragm to the effective area of ​​the first diaphragm is between 1.2 and 5.0, and the relative deviation between this ratio and the set value is no greater than 5%. The set value is the square of the quotient, which is the ratio of the product of the outlet velocity, gravitational acceleration, and the jet flight time. This relationship is derived from the projectile motion of the jet, directly corresponding a geometric quantity to a set of operating conditions.

[0022] To allow for on-site adjustment of this geometry, the first and second diaphragms are rigidly connected via a connecting disc with a fixed outer diameter. The periphery of the second diaphragm is pressed against the valve body by a replaceable sizing ring. The effective area of ​​the second diaphragm is defined by the inner diameter of the sizing ring and the outer diameter of the connecting disc. The valve body is equipped with multiple sizing rings with different inner diameters. Replacing a single sizing ring changes the compensation ratio, allowing the same valve to be adapted to different rated operating heights and rated tilt angles.

[0023] Alongside the compensation ratio, another adjusting factor is the bias component. The pressure regulating spring is a tension spring, with one end attached to the differential diaphragm assembly and the other end attached to a threaded adjusting seat screwed onto the valve body. The threaded adjusting seat protrudes from the valve body and is equipped with a locking nut. The product of the valve core's full adjustment stroke and the stiffness of the pressure regulating spring is no greater than 2% of the spring force of the pressure regulating spring under rated operating conditions, thus allowing the spring force to be considered constant within the adjustment stroke. The pressure regulating spring determines the negative bias component, which is independent of height, while the area ratio determines how quickly the nozzle inlet pressure moves with height. Both together determine the nozzle inlet pressure at the rated operating height; therefore, any change to one of them requires readjusting the rated pressure using the threaded adjusting seat.

[0024] The method of obtaining the feedback quantity also affects the accuracy of the compensation relationship. The pressure tap of the feedback channel is a pressure tapping hole opened on the inner wall of the nozzle inlet section and flush with the inner wall. The feedback channel is provided with a damping orifice. The flush pressure tapping hole obtains static pressure, without incorporating the dynamic pressure component brought by the jet acceleration, while the damping orifice is used to filter out the plunger pulsation of the ground pump, so that the diaphragm assembly only responds to slowly changing altitude signals.

[0025] The stress on the valve core itself also needs to be properly handled. The valve core is a lift-type valve core that mates with the valve seat. The valve core is connected to the differential diaphragm assembly via a valve stem. The valve stem passes through the isolation chamber and is guided by a guide sleeve fixed to the valve body. The valve core has a balance piston section. The valve body has a balance cylinder bore that slides and seals with the balance piston section and is isolated from the outlet cavity downstream of the valve core. The balance cylinder bore communicates with the inlet side via a pressure-feeding through hole opened in the valve core. Its cross-sectional area is equal to the sum of the area enclosed by the valve seat diameter and the cross-sectional area of ​​the valve stem, so that the effective pressure-bearing area of ​​the valve core acting on the inlet side pressure in two opposite directions along the valve stem axis is equal. In this way, the inlet pressure will not add an extra force to the diaphragm assembly through the valve core. The compensation ratio is entirely determined by the ratio of the effective areas of the two diaphragms and will not be contaminated by the valve port size.

[0026] For no-flow conditions, a vent valve is installed on the pipe section between the mechanical pressure regulator and the nozzle. The opening pressure of the vent valve is 1.1 to 1.3 times the rated inlet pressure, and lower than the lowest permissible operating pressure among the pipe section, the nozzle, and the feedback chamber. When the nozzle is closed and the aircraft is still descending, there is no downstream flow available for valve core adjustment. The vent valve provides a pressure relief path to prevent downstream pressure from rising.

[0027] On the support side, the airborne support includes a base fixed to the aircraft and a pitch adjustment seat rotatably supported on the base about a horizontal axis. Both the nozzle and the mechanical pressure regulating valve are mounted on the pitch adjustment seat. Since the nozzle and pressure regulating valve are mounted on the same pitch adjustment seat, the length and direction of the feedback channel do not change with the pitch angle, and the pressure tapping relationship remains stable.

[0028] It should also be noted that the spring bias requirement is necessary when the compensation ratio is greater than 1. Mechanical pressure regulators can only reduce pressure, not increase it; therefore, the nozzle inlet pressure must always be lower than the valve inlet pressure at any height. The reference pressure is taken from a stagnant liquid column, which is higher than the valve inlet pressure by a friction loss. Therefore, when the compensation ratio is greater than 1, only a sufficiently large negative bias component can bring the nozzle inlet pressure back to its rated value.

[0029] Based on this, a selection criterion can be given. The bias component obtained by dividing the spring force by the effective area of ​​the first diaphragm should not be less than the compensation ratio minus 1, multiplied by the reference pressure at the lowest operating height, plus the friction loss of the tethered supply pipe and the minimum operating pressure difference required by the valve itself. According to the calculation example below, when the compensation ratio is 2.47, the rated inlet pressure is 0.8 MPa, and the friction loss is 0.1 MPa, the bias component can be taken as 1.8 MPa. At this time, the outlet pressure of the ground supply equipment is about 1.64 MPa, which is within the capacity range of conventional fire pumps.

[0030] The beneficial effects of this invention are as follows. First, the flight altitude signal comes from the liquid column itself in the tethered liquid supply pipe, eliminating the need to add altitude sensors, controllers, and airborne booster pumps to the aircraft. The airborne components only require the addition of a valve and a section of piping, resulting in minimal increases in weight and power consumption, and eliminating the possibility of electrical failure.

[0031] Second, the compensation force is a tuneable quantity. A conventional fixed-value pressure reducing valve is equivalent to setting this ratio to zero, resulting in a constant nozzle inlet pressure; without a valve, it's equivalent to setting it to 1, where the nozzle inlet pressure changes in the same amount as the hydrostatic pressure of the liquid column. This invention sets this ratio to a range greater than 1, causing the nozzle inlet pressure to decrease with height faster than the hydrostatic pressure of the liquid column itself—a characteristic that neither fixed-value pressure reducing valves nor commonly used proportional pressure reducing valves can provide. Furthermore, by selecting the ratio according to the jet's landing point conditions, the sensitivity of the landing point to the hovering height can be significantly reduced.

[0032] Third, the compensation is completed locally upstream of the nozzle, without being transmitted through long pipelines or waiting for controller calculations, and the height fluctuation during hovering can be instantly followed. Fourth, the two settings have a clear sequence rather than being intertwined: first, the sizing ring is selected according to the working conditions to determine the compensation ratio, and then the threaded adjusting seat is turned to set the nozzle inlet pressure at the rated working height back to the rated value. Only a wrench is needed on site to complete the task. Attached Figure Description

[0033] Figure 1 This illustrates an application scenario of the device of the present invention in tethered liquid supply aerial firefighting operations.

[0034] Figure 2 The front view of the airborne part of the device of the present invention is shown.

[0035] Figure 3 The axial cross-sectional view of the mechanical pressure regulating valve is shown.

[0036] Figure 4 This shows a magnified cross-sectional view of the differential diaphragm assembly.

[0037] Figure 5 This shows a partially enlarged cross-sectional view of the valve core and valve seat mating area.

[0038] Figure 6 The exploded structure of the second diaphragm and the sizing ring is shown.

[0039] Figure 7 The connection structure between the reference tube and the tethered supply tube at the outlet of the ground supply equipment is shown.

[0040] Figure 8 The diagram shows a partial cross-sectional view of the nozzle inlet section and its flush pressure tapping orifice.

[0041] Figure 9The structure of the airborne support pitch adjustment mount is shown.

[0042] Figure 10 The diagram illustrates the operation of the device of the present invention when the hovering height changes.

[0043] In the diagram, 1 is the aircraft, 2 is the airborne support, 21 is the base, 22 is the pitch adjustment seat, 23 is the trunnion, 24 is the locking handle, 3 is the nozzle, 31 is the inlet section, 32 is the pressure tap, 33 is the retraction section, 4 is the tethered liquid supply pipe, and 5 is the ground liquid supply equipment.

[0044] 51 is the outlet, 52 is the tee connector, 6 is the mechanical pressure regulating valve, 61 is the valve body, 62 is the valve core, 63 is the valve stem, 64 is the guide sleeve, 65 is the valve seat, 66 is the pressure regulating spring, 67 is the threaded adjusting seat, 68 is the lock nut, and 7 is the differential diaphragm assembly.

[0045] 71 is the first diaphragm, 72 is the second diaphragm, 73 is the connecting plate, 8 is the control chamber, 81 is the feedback chamber, 82 is the reference chamber, 83 is the isolation chamber, 84 is the breathing hole, 9 is the feedback channel, 91 is the damping hole, 10 is the reference channel, and 11 is the reference tube.

[0046] 111 is the closed upper end, 112 is the lower end connector, 113 is the binding component, 12 is the sizing pressure ring, 13 is the relief valve, 14 is the jet, and 15 is the target surface. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention will be further described below with reference to the accompanying drawings. The embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; the structural forms, materials, and numerical values ​​given in the embodiments are illustrative examples and do not constitute a limitation on the scope of protection of this invention.

[0048] In this article, flight altitude and hovering altitude refer to the same physical quantity, namely the vertical distance from the nozzle outlet to the horizontal plane where the outlet 51 of the ground liquid supply equipment is located, which is also the height of the liquid column in the vertical section of the tethered liquid supply pipe; working altitude refers to the vertical distance from the nozzle outlet to the horizontal target plane. When the horizontal plane where the outlet 51 is located coincides with the horizontal target plane, the two are equal, and all the following embodiments are described according to this situation; when the two do not coincide, the liquid column height is calculated according to the former, the landing point relationship is calculated according to the latter, and the working mode of the device remains unchanged. Rated working altitude, rated depression angle, and rated inlet pressure are three design values ​​under the same rated working condition, where rated inlet pressure refers to the design pressure value at the nozzle inlet under the rated working condition. Full adjustment stroke refers to the stroke traveled by the valve core from the fully closed position that is in contact with the valve seat to the position of maximum overflow opening.

[0049] Furthermore, the statement in this article that the resultant force of the inlet-side pressure acting on the valve core is zero in the direction of valve core movement means that the valve core is designed according to the pressure-bearing area relationship given in Example 5 below, so that this resultant force is zero in design. During implementation, the residual unbalanced force due to assembly tolerances and measurement accuracy is considered to be satisfied when it does not exceed 1% of the regulating force of the valve port under rated operating conditions. The statement in this article that the allowable working pressure refers to the maximum allowable working pressure determined by the material, structure, and connection type of the corresponding pipe section, component, or chamber.

[0050] In the following examples, water is used as the liquid extinguishing medium, with a density of 1000 kg / m³ and a gravitational acceleration of 9.8 m / s². Unless otherwise stated, all pressures mentioned are gauge pressures relative to the local atmospheric pressure connected to the isolation chamber, and the static pressure of the liquid column is also converted according to the same benchmark. When using foam mixtures or other liquid extinguishing media, it is only necessary to recalculate the static pressure of the liquid column according to the actual density; the device structure remains unchanged.

[0051] Example 1: Overall structure of the device and pressure balance relationship.

[0052] like Figure 1 As shown, this altitude-compensated and pressure-stabilized aviation fire extinguishing liquid release device is installed on a tethered rotorcraft 1. The ground-based liquid supply equipment 5 can be a fire pump truck, and its outlet 51 is connected to the inlet of the mechanical pressure-stabilizing valve 6 via the tethered supply pipe 4. A portion of the tethered supply pipe 4 is launched with the aircraft 1, and the height of its vertical section is the ground clearance of the nozzle 3. After the fire extinguishing liquid is ejected from the nozzle 3, it forms a jet 14 and falls onto the target surface 15 on the ground.

[0053] like Figure 2 As shown, the base 21 of the airborne support 2 is fixed under the fuselage of the aircraft 1, and the pitch adjustment seat 22 is supported on the base 21 via trunnion 23. The nozzle 3 and the mechanical pressure regulating valve 6 are both mounted on the pitch adjustment seat 22. The axis of the nozzle 3 is tilted downward relative to the horizontal plane, and the feedback channel 9 connects the inlet section 31 of the nozzle 3 with the upper part of the mechanical pressure regulating valve 6.

[0054] like Figure 3As shown, the mechanical pressure regulating valve 6 has a valve seat 65 inside its valve body 61. A lift-type valve core 62 is located below and cooperates with the valve seat 65. When the valve core 62 moves upwards closer to the valve seat 65, the flow opening decreases. The extinguishing liquid enters the inlet cavity below the valve core 62 from the inlet at the lower part of the valve body 61, flows upwards through the central hole of the valve seat 65 into the outlet cavity, and then flows from the outlet at the side of the valve body 61 to the nozzle 3. The upper part of the valve body 61 is the control chamber 8, which is separated by a differential diaphragm assembly 7. The differential diaphragm assembly 7 is connected to the valve core 62 via a valve stem 63. The valve stem passes through the isolation cavity and is guided by a guide sleeve 64 fixed to the valve body. The outlet cavity and the feedback cavity 81 are both under the nozzle inlet pressure. The valve stem 63 does not experience a pressure difference when moving between them, thus not adding additional axial force to the differential diaphragm assembly 7.

[0055] like Figure 4 As shown, the differential diaphragm assembly 7 consists of a first diaphragm 71, a second diaphragm 72, and a connecting disc 73 that rigidly connects the two. The upper diameter of the valve body 61 is larger than the lower diameter, so the second diaphragm 72, located at the upper part, is larger than the first diaphragm 71, located at the lower part. The effective area of ​​the first diaphragm 71 is denoted as the first area, and the effective area of ​​the second diaphragm 72 is denoted as the second area, which is larger than the first area. The side of the first diaphragm 71 facing away from the second diaphragm 72 is the feedback chamber 81, which is connected to the inlet section 31 of the nozzle 3 via the feedback channel 9.

[0056] The side of the second diaphragm 72 facing away from the first diaphragm 71 is a reference chamber 82. The reference chamber 82 is connected to the reference pressure tapping part through a reference channel 10 opened in the valve body cover. When using a reference tube for pressure tapping, the closed upper end 111 of the reference tube 11 is connected to the outer end of the reference channel 10. Between the first diaphragm 71 and the second diaphragm 72 is an isolation chamber 83. The isolation chamber 83 is connected to the atmosphere through a breather hole 84 penetrating the side wall of the valve body 61, so that each of the two diaphragms only bears the liquid pressure on one side. When the diaphragms are displaced, the air in the isolation chamber can freely enter and exit without generating additional air pressure.

[0057] The pressure regulating spring 66 is a tension spring, with its lower end attached to the connecting plate 73 and its upper end attached to the threaded adjusting seat 67, which protrudes from the valve body and is equipped with a locking nut 68. The reference chamber 82 is located above the differential diaphragm assembly 7, and its pressure pushes the diaphragm assembly downwards; the feedback chamber 81 is located below the differential diaphragm assembly 7, and its pressure pushes the diaphragm assembly upwards; the pressure regulating spring 66 pulls the diaphragm assembly upwards, with the spring force in the same direction as the feedback pressure. The balance of these three elements determines the position of the valve core 62.

[0058] From this, the force balance relationship of the differential diaphragm assembly 7 can be written. The reference pressure multiplied by the second area equals the nozzle inlet pressure multiplied by the first area plus the spring force of the adjusting spring. Dividing both sides of the equation by the first area and rearranging the terms, we obtain the nozzle inlet pressure as the following component obtained by multiplying the reference pressure by the ratio of the second area to the first area, minus the bias component obtained by dividing the spring force by the first area. For ease of explanation, the ratio of the second area to the first area will be referred to as the compensation ratio below.

[0059] The negative sign of the bias component here is the fundamental difference in force relationship between this device and a conventional pressure reducing valve. In a conventional pressure reducing valve, the spring provides the force in the opening direction, and the outlet pressure equals the positive value set by the spring. In this device, the spring is changed to run in the same direction as the feedback pressure, only serving to pull the following component back to its rated value. Because of this, the compensation ratio can be greater than 1, meaning the nozzle inlet pressure decreases with height faster than the hydrostatic pressure of the liquid column itself. If the spring force were still positive using the conventional connection method, the right side of the equation would be higher than the reference pressure when the compensation ratio is greater than 1. Since the reference pressure is already higher than the valve inlet pressure, balance cannot be established.

[0060] The above proportional relationship holds true only if the spring force can be considered constant within the valve core's adjustment stroke. Therefore, the full adjustment stroke of the valve core 62 is limited to within 2 mm, and the stiffness of the pressure regulating spring 66 is set to below 3 N / mm. At this point, the change in spring force within the full adjustment stroke does not exceed 6 N, which is on the order of 1% compared to the spring force under rated operating conditions; that is, the product of stroke and stiffness does not exceed 2% of the spring force. If the operating pressure range is very wide and the stroke must be increased, a constant force spring can be used, whose force value remains essentially unchanged within the full adjustment stroke.

[0061] The statement in this paper that the ratio of pressure change to area ratio is equal refers to the design relationship obtained under the above-mentioned force balance relationship and under the premise that the spring force is considered constant within the adjustment stroke. In actual devices, the spring stiffness is limited, and the spring force still has a systematic change of about 1% within the full adjustment stroke. This can be reduced to a negligible level during the design process according to the above-mentioned stroke and stiffness constraints. In addition, the friction between the valve stem 63 and the guide sleeve 64, as well as the elastic hysteresis of the diaphragm itself, will also create a hysteresis. The former can be controlled by the fit clearance and coaxiality, while the latter depends on the material and structure of the diaphragm. The superposition of the above factors causes a small deviation of the measured slope from the design value. According to this, the deviation in Embodiment 7 below will be used as a criterion for whether the assembly is normal.

[0062] The effective area of ​​the diaphragm is determined according to the commonly used method in the diaphragm industry, that is, the effective diameter is taken as the arithmetic mean of the inner diameter of the sizing ring and the outer diameter of the connecting plate, and the effective area is calculated as the area of ​​the circle with that diameter. The effective area referred to herein and in the claims is determined according to this method; the calibration in Example 7 below is only used to verify the value obtained therefrom, and is not used to define it.

[0063] The source of the reference pressure is crucial. The reference pressure tap is connected to the outlet 51 of the ground-based liquid supply device 5 by a continuous liquid column. Therefore, the reference pressure equals the pressure at outlet 51 minus the static pressure of that liquid column, which is a factor proportional to the hovering height. For every 1 meter increase in hovering height, the reference pressure decreases by approximately 9.8 kPa. Substituting this into the above formula, the nozzle inlet pressure decreases by approximately 9.8 kPa multiplied by the compensation ratio.

[0064] When the compensation ratio is 1, the nozzle inlet pressure is the same as when no valve is installed, changing by an equal amount with the hydrostatic pressure of the liquid column. When the compensation ratio is zero, the reference chamber disappears, the valve degenerates into a constant-value pressure-reducing valve, and the nozzle inlet pressure remains constant. This invention sets the compensation ratio to a range greater than 1, allowing the nozzle inlet pressure to decrease with height faster than the hydrostatic pressure of the liquid column itself. This characteristic is a necessary condition for the landing point to remain stationary; whether the landing point can truly remain stationary depends on whether the ratio is selected according to the criteria given in Example 2.

[0065] Example 2: The basis for adjusting the compensation ratio and the effect of the landing point.

[0066] After leaving nozzle 3, jet 14 undergoes projectile motion. In this embodiment, the target surface 15 is a horizontal plane, and the rated operating height is the vertical distance from the nozzle 3 outlet to this horizontal plane. The nozzle ejects the jet diagonally downward at a rated depression angle. The nozzle outlet velocity is determined by the nozzle inlet pressure according to the velocity relationship of the liquid jet. The time it takes for the jet to travel from the nozzle outlet to the target surface 15 is called the jet flight time. As the hovering height increases, the jet flight time becomes longer. If the outlet velocity remains unchanged, the landing point will inevitably shift outward. Simultaneously, if the nozzle inlet pressure decreases with height according to the compensation ratio, the outlet velocity decreases accordingly, and the landing point will shift inward.

[0067] By making these two effects cancel each other out, we can solve for the condition that the compensation ratio should satisfy when the landing point is stationary, that is, the compensation ratio is equal to the square of the ratio of the product of the exit velocity and the product of the gravitational acceleration and the jet flight time.

[0068] To facilitate verification against the diagram, let's break down the above derivation. First, neglecting local losses within the nozzle, the outlet velocity is equal to the square root of the quotient obtained by dividing twice the nozzle inlet pressure by the medium density. Therefore, for every minute change in the nozzle inlet pressure, the change in outlet velocity is equal to that minute change divided by the product of the medium density and the outlet velocity.

[0069] Next, substituting the relationship between the nozzle inlet pressure and height according to the compensation ratio, we obtain that the rate of change of the outlet velocity with respect to the hovering height is equal to the product of the compensation ratio and gravitational acceleration divided by the outlet velocity, and we take a negative sign, meaning that as the height increases, the velocity decreases. Finally, we express the horizontal range of the jet as the product of the horizontal velocity component and the jet flight time. The jet flight time is solved from the uniform acceleration relationship in the vertical direction. Taking the total derivative with respect to the hovering height and setting it to zero, we obtain the aforementioned conditions.

[0070] The derivation only uses the two basic relationships of uniformly accelerated linear motion and projectile motion, without introducing empirical coefficients. Therefore, this condition holds true for nozzles of different diameters and media densities. When the target surface is an inclined or vertical surface, the derivative of the jet flight time with respect to height differs from the above formula. The stationary condition must be derived separately according to the geometry of the target surface. The relationship given in this embodiment is only applicable to horizontal target surfaces. The media density is only included in the result through the outlet flow velocity. When using a foam mixture, the outlet flow velocity can be recalculated based on its actual density.

[0071] After repeatedly verifying the dimensions and limiting cases of this condition, the inventor confirmed that it is independent of nozzle diameter, flow rate, and pipe diameter, and depends only on the kinematics of the jet itself. This point has not been discussed before in the context of aviation release. The form of this relationship is very simple, and its meaning is intuitive. The product of gravitational acceleration and jet flight time is the increase in vertical velocity acquired by the jet in the air, and the compensation ratio is the square of the ratio of the outlet velocity to this increase in vertical velocity. The longer the jet flies, that is, the higher the operating altitude and the smaller the depression angle, the smaller the required compensation ratio; conversely, when the operating altitude is low and the depression angle is large, the jet falls to the ground quickly, and the flight time is more sensitive to altitude, requiring a larger compensation ratio.

[0072] The jet is also affected by air resistance and jet breakup in the air, and the actual landing point is slightly closer than the landing point calculated by the ideal projectile mentioned above. This effect mainly changes the absolute position of the landing point, while this invention is concerned with the sensitivity of the landing point to changes in hovering height. Air resistance slightly increases the jet flight time and slightly decreases the horizontal velocity component, the net effect of which is equivalent to slightly increasing the required compensation ratio. In engineering, the value can be obtained first according to the aforementioned relationship, and then the sizing ring can be finely adjusted by one step according to the actual landing point during calibration.

[0073] The following are examples calculated using the above formulas to illustrate the order of magnitude. The values ​​are calculated using these formulas and are not actual measured data. Assuming a rated nozzle inlet pressure of 0.8 MPa and water as the medium, the nozzle outlet velocity is approximately 40 m / s. With a rated depression angle of 15 degrees and a rated operating height of 60 meters, the jet flight time is approximately 2.60 seconds. The compensation ratio calculated using the formula is approximately 2.47, corresponding to a ratio of approximately 1.57 between the effective diameters of the two diaphragms. If the effective diameter of the first diaphragm is 20 mm, the effective diameter of the second diaphragm should be 31.5 mm. Using the aforementioned method for determining the effective diameter, a sizing ring with an inner bore of 47 mm is selected, resulting in a compensation ratio of approximately 2.48. The relative deviation from the criterion value of 2.47 is approximately 0.4%, within the aforementioned 5% tolerance.

[0074] Under this set of parameters, if the hovering height fluctuates within a range of 4 meters above and below the rated working height, the full-width drift of the landing point, i.e., the difference between the maximum and minimum values ​​of the landing point position within this height range, is compensated as follows: approximately 8.6 meters when using a conventional pressure-reducing valve (i.e., compensation ratio of zero); approximately 5.1 meters when not using a pressure-reducing valve (i.e., compensation ratio of 1); and approximately 0.6 meters when using a compensation ratio of 2.48 according to this invention.

[0075] With a rated depression angle of 25 degrees and a rated operating height of 50 meters, the jet flight time is approximately 1.91 seconds. The compensation ratio calculated using the formula is approximately 4.59. The effective diameter of the second diaphragm should be 43 mm, meaning a sizing ring with an inner diameter of 70 mm should be selected, resulting in a compensation ratio of approximately 4.62 and a relative deviation of approximately 0.7%, both within the allowable tolerance. Similarly, with a height fluctuation of 4 meters above and below the diaphragm, the landing point drifts approximately 8.2 meters when the compensation ratio is zero. After adjustment according to this invention, the drift is approximately 1.1 meters.

[0076] The above example also explains why the compensation ratio must be adjustable and not fixed. With a rated depression angle of zero degrees and a rated working height of 80 meters, the compensation ratio calculated according to the formula is approximately 1.02. At this point, the natural characteristic of not installing a valve results in a stationary landing point, while a conventional pressure-reducing valve would amplify the landing point drift. This value is outside the preferred ratio range given later; the given condition is a boundary point for comparison, not the preferred operating condition for this device. Once the operating conditions deviate from this point, regardless of the direction of deviation, a specific compensation ratio is required. It is important to emphasize that only the ratio selected according to this formula can minimize landing point drift; an excessively large ratio will also cause the landing point to drift inwards. Therefore, the landing point effect of this invention is attributed to the implementation method adjusted according to this criterion, and not to any ratio greater than 1.

[0077] Example 3: Two methods for determining the reference pressure.

[0078] The first method is as follows: Figure 7 As shown. The device also includes a reference pipe 11 laid in parallel with the tethered liquid supply pipe. The lower end of the reference pipe is connected to the outlet side of the ground liquid supply equipment, and the upper end of the reference pipe is a closed end that is only connected to the reference channel. The reference pipe has no continuous flow when the nozzle releases the extinguishing liquid in a steady state.

[0079] The diameter of the reference tube 11 is much smaller than that of the tethered liquid supply tube 4. The two are tied together at intervals with the strapping piece 113 and are deployed and retrieved with the aircraft 1. Its lower end is connected to the tee connector 52 at the outlet 51 via the lower end connector 112, and its upper end is a closed upper end 111 that is connected to the reference channel 10.

[0080] When nozzle 3 releases extinguishing liquid in a steady state, there is no continuous flow inside reference tube 11, and therefore no friction loss. The pressure at the closed upper end 111 is equal to the pressure at outlet 51 minus the static pressure of the liquid column in the reference tube. Since there is flow in the moored supply pipe 4 but not in reference tube 11, the reference pressure at the same height is always higher than the valve inlet pressure by one friction loss. A compensation ratio greater than 1 is not contingent on this; as long as the offset component is large enough, a pressure greater than 1 can also be obtained when taking the pressure locally. The role of the reference tube is to eliminate this friction loss from the reference pressure, ensuring that the compensation ratio does not drift with flow rate. When the diaphragm displaces, there will be a very small amount of transient flow in the reference tube, the resulting pressure drop of which is negligible compared to the static pressure of the liquid column. Thus, the reference pressure obtained only changes with the hovering height, and the compensation ratio will not drift with nozzle diameter changes or flow rate adjustments.

[0081] Before the reference tube 11 is put into use, the air must be purged; otherwise, the residual air column will slow down the transmission of the reference pressure. To this end, a manual vent plug can be installed on the section of the pipe before the reference channel 10 connects to the reference chamber 82. Before operation, the plug is opened to vent until liquid flows out continuously, and then tightened. The plug is located on one side of the reference channel and is in a closed state during operation. The upper end of the reference tube 11 is still only connected to the reference channel 10.

[0082] The second method involves placing the reference pressure tap on a section of the tethered supply pipe located at the inlet side of the mechanical pressure regulator. The reference channel extends from this section and connects to the reference cavity along the outer wall of the mechanical pressure regulator body. This method eliminates the need for a second pipeline, maintains the interface between the airborne and ground-based components, and is more convenient for retrofitting existing equipment.

[0083] The trade-off is that the reference pressure includes frictional losses along the tethered supply pipe, which vary with the square of the release flow rate. This loss can only be approximated as a constant and incorporated into the bias component, and adjusted by the pressure regulating spring, under the conditions that the nozzle outlet orifice diameter is fixed (i.e., the nozzle does not employ a variable orifice structure during operation), the ground supply equipment operates at a constant outlet pressure, and the release flow rate is in a quasi-steady state. Even then, the actual compensation ratio will still drift slightly with flow fluctuations, making this a secondary option. If the nozzle orifice diameter needs to be changed during operation, or if the ground pump unit requires variable pressure operation, then the first method must be used.

[0084] Example 4: On-site adjustment of compensation ratio.

[0085] like Figure 6 As shown, the periphery of the second diaphragm 72 is pressed against the valve body 61 by the sizing ring 12. The effective area of ​​the second diaphragm 72 is defined by the inner diameter of the sizing ring 12 and the outer diameter of the connecting plate 73. When the outer diameter of the diaphragm itself remains constant and the outer diameter of the connecting plate is fixed, the smaller the inner diameter of the sizing ring, the narrower the annular surface on which the diaphragm can deform freely and bear pressure, and the smaller the second area becomes.

[0086] In this embodiment, the outer diameter of the connecting plate 73 is 16 mm and remains constant across all settings. The inner diameter of the pressure ring of the first diaphragm 71 is 24 mm, and its effective diameter is 20 mm according to the aforementioned method. A set of sizing pressure rings 12 with different inner diameters are provided with the valve, with inner diameters of 32 mm, 40 mm, 47 mm, 54 mm, 62 mm, and 70 mm respectively. The corresponding effective diameters of the second diaphragm are 24 mm, 28 mm, 31.5 mm, 35 mm, 39 mm, and 43 mm, with compensation ratios of approximately 1.44, 1.96, 2.48, 3.06, 3.80, and 4.62 respectively. During replacement, the valve body cover is removed, the original pressure ring is removed, a new pressure ring is installed, and the ring is tightened again. Neither the first diaphragm 71 nor the connecting plate 73 needs to be moved.

[0087] It is important to note that the compensation ratio itself appears in the pressure expression at the rated point. Therefore, the nozzle inlet pressure at the rated working height will inevitably change after changing the ring. It is necessary to then turn the threaded adjusting seat 67 to readjust the offset component so that the rated point pressure returns to its original value, and then tighten the locking nut 68. Changing the ring and adjusting the spring are two consecutive steps; the former cannot be done alone.

[0088] When it is necessary to take into account two significantly different working heights, the midpoint of the corresponding compensation ratios can be used. In this case, the drift of the landing point at both heights is not zero but is suppressed. A compensation ratio that is too large or too small will not cause the device to fail, but will only cause the drift direction of the landing point to turn inward or outward, respectively.

[0089] Example 5: Several structural details related to the compensation relationship.

[0090] like Figure 5 As shown, the valve core 62 is designed as a balanced structure with equal areas of inlet pressure in two opposite directions along the valve stem axis. The upper end of the valve core 62 has a balanced piston section, and the valve body 61 has a balanced cylinder bore that slides within it. A seal is provided at the fit to separate the balanced cylinder bore from the outlet cavity downstream of the valve core. The inlet pressure is led to the upper end face of the balanced piston section through a pressure-guiding hole inside the valve core. The area of ​​the inlet pressure acting upwards on the valve core is the area enclosed by the diameter of the valve seat 65; the area acting downwards is the upper end face of the balanced piston section, the center of which is occupied by the valve stem 63. Its pressure-bearing area is equal to the cross-sectional area of ​​the balanced cylinder bore minus the cross-sectional area of ​​the valve stem. Making these two equal, the cross-sectional area of ​​the balanced cylinder bore should be equal to the sum of the area enclosed by the valve seat diameter and the cross-sectional area of ​​the valve stem.

[0091] In addition, when the valve stem diameter is much smaller than the valve seat diameter, the balance cylinder bore diameter can be directly taken to be equal to the valve seat diameter. In this case, the residual unbalanced force is equal to the product of the inlet pressure and the valve stem cross-sectional area. As long as this value is still less than 1% of the regulating force of the valve port under rated operating conditions, it is still within the force balance meaning mentioned above. In this embodiment, the valve seat diameter is 16 mm and the valve stem diameter is 3 mm. The valve stem cross-sectional area accounts for about 3.5% of the area enclosed by the valve seat diameter. When using this approximation, it should be calculated according to the above criteria before determining the final value.

[0092] Without this treatment, the inlet pressure will exert an additional force on the valve stem 63 through the unbalanced area of ​​the valve core. This force also varies with the hovering height. The effect is equivalent to adding an additional term determined by the valve port size to the compensation ratio, causing the actual compensation ratio to deviate from the design value, and this deviation changes with valve port wear. With a balanced design, the compensation ratio is determined only by the ratio of the effective areas of the two diaphragms.

[0093] like Figure 8 As shown, the pressure tap on the nozzle inlet section 31 of the feedback channel 9 is a pressure tap 32 flush with the inner wall, with no burrs or protrusions at the opening. Since the flow velocity of the extinguishing liquid in the inlet section 31 is still low, the pressure tap obtained from the flush-mounted tap is static pressure. If the pressure tap is located on the contraction section 33 or the connecting pipe is inserted into the flow channel, the obtained pressure will be mixed with a dynamic pressure component that varies with the flow rate, and the feedback quantity will no longer be the nozzle inlet pressure itself.

[0094] The feedback channel 9 is equipped with a damping orifice 91, the orifice diameter of which can be 0.8 mm to 1.5 mm to filter out the discharge pulsation of the ground plunger pump; the orifice diameter should not be too small, otherwise it will slow down the response of the diaphragm assembly to altitude changes. The actual selection is based on the time constant formed by the damping orifice and the feedback cavity being significantly smaller than the aircraft's altitude floating period.

[0095] A relief valve 13 is installed on the pipe section between the mechanical pressure regulating valve 6 and the nozzle 3. Its opening pressure is 1.1 to 1.3 times the rated inlet pressure, and must be lower than the lowest allowable working pressure among the three: the pipe section, the nozzle 3, and the feedback chamber 81. Otherwise, the relief valve will not activate before downstream overpressure and will not provide protection. When the nozzle 3 is closed and the aircraft 1 continues to descend, the downstream section is a closed liquid. Although the valve core 62 is closed to the minimum opening, residual leakage at the valve port and elastic rebound of the pipeline may still cause the downstream pressure to rise slowly. At this time, the relief valve 13 opens a pressure relief passage, and a small amount of liquid can be discharged through the hose to the outside of the aircraft.

[0096] like Figure 9As shown, the pitch adjustment seat 22 is supported on the base 21 via the trunnion 23. After the locking handle 24 is released, it can rotate around the trunnion 23 to change the pitch angle of the nozzle 3. After rotating to the correct position, tighten the locking handle 24 to lock it in place. The nozzle 3 and the mechanical pressure regulating valve 6 are mounted on the pitch adjustment seat 22 together, and their relative positions do not change with the pitch angle. Therefore, the length and direction of the feedback channel 9 remain unchanged.

[0097] When the pitch angle changes, the jet flight time changes accordingly. The compensation ratio according to the formula in Example 2 should also be reselected. Therefore, the base 21 is provided with a pitch angle scale, and a comparison table of the pitch angle and the inner diameter of the sizing ring is given in the instruction manual.

[0098] Example 6: The operation process of the device.

[0099] like Figure 10 As shown, a complete operating cycle of the device is as follows. After the ground-based liquid supply equipment 5 is started, the tethered liquid supply pipe 4 and the reference pipe 11 are filled with fire extinguishing liquid. The aircraft 1 ascends to the rated operating altitude and adjusts the pitch angle. The threaded adjusting seat 67 is turned to increase the tension of the pressure regulating spring 66, so that the inlet pressure of the nozzle 3 drops to the rated value. The locking nut 68 is tightened. At this time, the differential diaphragm assembly 7 is in the equilibrium position, and the valve core 62 stops at a certain opening degree.

[0100] When aircraft 1 ascends due to gusts of wind, the liquid column in reference tube 11 rises, and the reference pressure in reference chamber 82 decreases, thus reducing the downward force pushing the differential diaphragm assembly 7. Under the combined action of the pressure in feedback chamber 81 and the tension of the pressure regulating spring 66, the diaphragm assembly 7 moves upward, driving the valve core 62 upward towards the valve seat 65 via valve stem 63. This reduces the flow opening, causing the inlet pressure of nozzle 3 to decrease until a new equilibrium is established. The magnitude of this decrease is approximately the product of the decrease in reference pressure and the compensation ratio. The deviation from this value is determined by the spring stiffness, the friction between valve stem 63 and guide sleeve 64, and the elastic hysteresis of the diaphragm. By selecting a spring according to the aforementioned constraints, controlling the fitting clearance, and choosing a diaphragm with low hysteresis, this deviation can be minimized. The nozzle outlet velocity thus decreases. If the compensation ratio has been set according to the criterion of Example 2, the reduction in flow velocity will offset most of the outward shift of the landing point caused by the longer jet flight time, and the residual drift is of the order of magnitude listed in the example of Example 2; the further the ratio deviates from the criterion value, the greater the residual drift, but the device still operates according to the ratio.

[0101] As aircraft 1 descends, the above process reverses. The reference pressure increases, increasing the downward force on diaphragm assembly 7. Diaphragm assembly 7 moves downward, valve core 62 moves away from valve seat 65, the flow opening increases, and the nozzle inlet pressure recovers. The recovery magnitude is approximately the product of the reference pressure increase and the compensation ratio, which, when the ratio is set according to the criteria, offsets most of the inward shift in landing point caused by the shortened flight time. When the hovering altitude returns to its rated value, the differential diaphragm assembly 7 returns to its original equilibrium position, and the nozzle inlet pressure returns to its rated value. Throughout the entire process, only the valve core and diaphragm assembly move; no electrical signals are required.

[0102] If the outlet pressure of the ground-based liquid supply equipment 5 changes, for example, when the pump switches gears and the reference pressure and inlet pressure change simultaneously, the nozzle inlet pressure will follow a portion of this change according to the compensation ratio, while the remaining portion will be absorbed by the throttling at the valve orifice. Therefore, the ground-based liquid supply equipment should preferably be operated in constant pressure mode. If variable pressure operation is necessary, a throttling element similar to the damping orifice 91 can be added to the reference channel 10 so that the reference pressure only follows the slow-changing component.

[0103] Example 7: Calibration and adjustment steps for the compensation ratio.

[0104] Before the device leaves the factory and after replacing the sizing ring, calibration should be completed on the ground; actual flight is not required. Install the mechanical pressure regulating valve 6 according to its operating condition, connect the inlet to an adjustable pressure water pump, connect the outlet to a nozzle 3 of the same diameter, connect the feedback channel 9 as actually is, and modify the reference channel 10 to connect an independently adjustable hydraulic source to simulate the reference pressure.

[0105] First, adjust the reference pressure to the value corresponding to the rated working height, that is, the outlet pressure of the ground liquid supply equipment minus the static pressure of the liquid column corresponding to the rated working height. Then, turn the threaded adjusting seat 67 to make the nozzle inlet pressure drop to the rated value, and tighten the locking nut 68. This step adjusts the offset component.

[0106] Secondly, keeping the inlet pressure constant, adjust the reference pressure up and down several levels, each equivalent to 1 meter of hydrostatic pressure, and record the nozzle inlet pressure at each point. Divide the change in nozzle inlet pressure by the change in reference pressure; the resulting slope is the actual compensation ratio. Finally, compare the measured slope with the design slope calculated using the effective area method: a relative deviation within 2% indicates normal assembly; if it exceeds 2%, check for assembly problems such as diaphragm periphery clamping, connecting plate slippage, and valve stem jamming. After confirming normal assembly, if the difference between the design slope and the target compensation ratio selected based on the landing point criterion exceeds 5%, replace it with a sizing ring of the adjacent specification (12) and repeat the previous step.

[0107] Here, it's necessary to distinguish between two different quantities. The inner diameter of the sizing ring is a geometric dimension, while the effective area of ​​the diaphragm is the equivalent area in terms of force. Its value is determined by the arithmetic mean of the inner diameter of the sizing ring and the outer diameter of the connecting plate, as given in Example 1, and is unrelated to the actual measurement in this step. The measured slope in this step is only used for verification: if the difference between the measured slope and the area calculated by this method is within 2%, the diaphragm assembly is considered normal; if the difference is too large, it usually means that the diaphragm is not properly clamped at the periphery or there is slippage between the connecting plate and the diaphragm. Assembly problems should be ruled out first, rather than rewriting the effective area based on the measured value.

[0108] Two points need to be checked during calibration. First, adjust the reference pressure back and forth within the set range. The difference between the nozzle inlet pressure in the upward and downward directions under the same reference pressure is the hysteresis. Hysteresis mainly comes from the friction between the valve stem 63 and the guide sleeve 64 and the diaphragm hysteresis. It should be controlled within 1% of the rated inlet pressure. If it is too large, the guide sleeve clearance and the coaxiality of the valve stem should be checked.

[0109] Secondly, vary the inlet pressure within the actual range and observe the drift of the nozzle inlet pressure. This drift reflects the balance of the valve core. A significant deviation indicates that the balance piston section of the valve core 62 does not match the diameter of the valve seat 65.

[0110] For comparison, the present invention is compared with three comparable control schemes under the same set of operating conditions in terms of structure and effect. The effect values ​​are also calculated by the aforementioned formula and are not actual measured data.

[0111] Comparative Example 1 uses a conventional pressure-reducing valve connected in series upstream of the nozzle. This design has only one diaphragm, and the spring chamber is vented to the atmosphere via a breather hole, resulting in a zero compensation ratio. Structurally, it has one less diaphragm and one less reference channel than this invention. However, under conditions of a rated depression angle of 15 degrees, a rated working height of 60 meters, and a hovering height fluctuating by 4 meters above and below, the landing point drifts approximately 8.6 meters across the entire width, and the drift direction is consistently outward.

[0112] Comparative Example 2 involves a scheme without any pressure regulating valve, with a compensation ratio of 1. Under the same conditions, the landing point drifts by approximately 5.1 meters across the entire width. Comparative Example 3 involves installing an altitude sensor, controller, and onboard booster pump on the aircraft. The target jet pressure is calculated based on the measured altitude and supplemented by the onboard pump. This scheme can also reduce landing point drift when the controller is properly tuned, but it adds a pump, motor, sensor, controller, and power supply lines to the aircraft, and introduces three failure paths not present in this invention: sensor failure, controller crash, and power outage.

[0113] Under the same conditions, the present invention reduces the full-width drift of the landing point to about 0.6 meters. The airborne part is an additional diaphragm, a sizing ring and a reference channel compared to the first comparative example, and an additional valve and a thin tube compared to the second comparative example.

[0114] Example 8: Multiple nozzles connected in parallel and matched with orifice diameter.

[0115] When two jets need to be generated simultaneously, a flow divider can be connected after the outlet of the mechanical pressure regulating valve 6, and two nozzles 3 can be connected to it. The pressure tap 32 is still located only on the inlet section 31 of one of the nozzles, and the other is connected to a pipe of the same specification and length. After parallel connection, the total flow rate increases, the friction loss increases, and the valve inlet pressure decreases. The aforementioned pressure margin should be recalculated.

[0116] If the two nozzles have different depression angles, their corresponding landing point stationary compensation ratios will also be different, and only one of them can be set. In this case, it is advisable to equip each nozzle with a mechanical pressure regulating valve 6, with the two valves sharing the same reference pipe 11. The reference channel 10 is connected to the reference chambers 82 of the two valves via a distribution block.

[0117] The nozzle diameter and compensation ratio are independent of each other. The diameter determines the absolute values ​​of the flow rate and range, while the compensation ratio determines the rate of change of the range with height. When changing the nozzle diameter, if a reference tube is used to take the pressure, the reference pressure is not affected and the compensation ratio does not need to be changed; if a local pressure is taken, the friction loss changes with the flow rate, and the offset component needs to be readjusted by turning the threaded adjusting seat 67 back to the rated value.

[0118] Example 9: Installation, use and maintenance of the device.

[0119] During installation, first fix the base 21 under the fuselage of aircraft 1 and confirm the center of gravity. Then, install the pitch adjustment seat 22, which already has the nozzle 3 and mechanical pressure regulating valve 6 installed, onto the trunnion 23. When laying the tethered supply tube 4 and reference tube 11 on the ground, they should be coiled in the same direction and secured every 2 meters with a binding clip 113 to prevent tangling. After the lower end connector 112 of the reference tube 11 is connected to the tee connector 52, first fill and vent the reference tube separately, and then connect the tethered supply tube 4.

[0120] Before the first operation, a functional confirmation should be performed at low altitude: stabilize the aircraft at an altitude of 2 meters and record the nozzle inlet pressure, then rise to 4 meters. The pressure should drop by about 20 kPa multiplied by the compensation ratio; if it does not drop or rises instead, it is likely due to residual air column in the reference tube or blockage of the reference channel 10.

[0121] Routine maintenance focuses on three areas. The diaphragm is a consumable part; it should be inspected at least once a year for cracks in the folds, and both diaphragms should be replaced together. Dust easily accumulates inside the splash guard of the breather 84; if blocked, the isolation chamber 83 cannot breathe freely, and the diaphragm assembly's movement becomes sluggish. It is advisable to blow it clean after each operation.

[0122] The damping orifice 91 has a small diameter and may be partially blocked by impurities in the water, resulting in a slower response of the device to changes in height. The feedback channel 9 can be removed to clear the blockage and backflushed. The reference tube 11 is easily flattened during extension and retraction. Right-angle bends should be avoided. If there are obvious indentations on the tube wall, the entire section should be replaced, as air bubbles will remain at the flattened area, slowing down the establishment of the reference pressure.

[0123] Regarding the selection of components: The first diaphragm 71 and the second diaphragm 72 can be made of nitrile rubber or fluororubber with a fabric reinforcement. The thickness and number of fabric layers of the two diaphragms should preferably be the same to avoid nonlinearity introduced by stiffness differences. The connecting disc 73 and the valve stem 63 should preferably be connected by threads with anti-loosening measures to facilitate the disassembly and assembly of the diaphragms.

[0124] The valve body 61 can be made of aluminum alloy to reduce the load and can be hard anodized. The sealing surfaces of the valve seat 65 and the valve core 62 can be made of stainless steel with a polytetrafluoroethylene soft seal. The moored supply hose 4 should preferably be a high-pressure hose with an inner liner, and the reference hose 11 can be a pressure-resistant nylon hose with a diameter of 4 mm to 6 mm, with a pressure rating not lower than the highest outlet pressure of the ground supply equipment.

[0125] Regarding abnormal operating conditions: When the supply pipe 4 is bent or blocked, the valve inlet pressure drops sharply, the valve core 62 opens to its maximum degree, the device loses its regulating ability, and the range is shortened. This can serve as a direct indication of pipeline obstruction. When the reference pipe 11 leaks, the reference pressure drops, and the nozzle inlet pressure drops accordingly according to the compensation ratio. The range is also shortened but will not rise uncontrollably, which is a safety-biased failure.

[0126] The breathing port 84 should open downwards and be fitted with a splash guard to prevent extinguishing liquids or rainwater from entering the isolation chamber 83. If liquid accumulates in the isolation chamber 83, additional hydraulic coupling will occur between the two diaphragms, and the compensation ratio will be distorted. Therefore, a drain plug should be installed at the lowest point of the isolation chamber 83.

[0127] Regarding alternative forms of the reference tube: If it is not advisable to install a separate thin tube in the mooring section, the reference tube 11 can be made into an inner tube coaxial with the mooring supply tube 4, with the lower end opening inside the outlet 51 and the upper end leading to the reference channel 10. The coaxial arrangement eliminates the need for the binding piece 113 and avoids tangling, but at the cost of occupying a portion of the flow area and requiring the entire hose to be pulled out during maintenance.

[0128] Another approach is to co-extrude the reference tube 11 and the tethered supply tube 4 into a double-lumen hose, with the smaller lumen serving as the reference tube. This design offers the best retraction and extension performance but requires a specialized mold. Regardless of the approach used, as long as there is no flow in the smaller lumen during operation and the lower end is connected to the outlet side of the ground-based supply equipment, the expression for the reference pressure remains the same as described above.

[0129] Regarding low-temperature operating conditions: When the ambient temperature is below zero degrees Celsius, the reference pipe 11 is most prone to freezing due to the lack of flow. Once ice blockage occurs, the reference pressure will be frozen at the value at the moment of freezing, and the device will degenerate into a normally rated pressure reducing valve without providing incorrect compensation direction. This freezing value should meet the condition described later, which is not lower than the value taken under rated operating conditions. To reduce the risk, the reference pipe 11 can be bundled together with the tethered supply pipe 4 to utilize the heat of the main pipe fluid for insulation, or antifreeze can be added to the extinguishing fluid. Before winter operations, the main pipe should be circulated for several minutes, and then the vent plug should be opened to confirm a continuous flow of fluid before venting.

[0130] Regarding alternative implementations, the differential diaphragm assembly 7 can also be replaced by two pistons of different diameters, rigidly connected, with a low-friction slip ring sealing between the piston and the cylinder. The advantage is a larger stroke, but the disadvantage is that friction introduces a dead zone at the pressure setpoint, which is detrimental to small-amplitude height tracking. Therefore, the diaphragm is preferred.

[0131] A manual shut-off valve can also be added between the reference channel 10 and the reference chamber 82. Closing this valve during operation seals the reference chamber 82 at the reference pressure at the moment of closure, preventing the reference pressure from changing with altitude. The device temporarily degenerates into a constant-value pressure-reducing valve for debugging and comparison. It is not permissible to connect the reference chamber 82 to the atmosphere here: according to the aforementioned force balance relationship, when the reference pressure drops to atmospheric pressure, the pressure in the feedback chamber 81 and the tension of the pressure regulating spring 66 push the differential diaphragm assembly 7 in the same direction towards closure, preventing the establishment of balance and causing the valve to shut off. Therefore, whether it is manual sealing in this section or low-temperature ice blockage in the preceding section, the frozen reference pressure must not be lower than the value under rated operating conditions; otherwise, the same shutdown situation will occur. The shutdown itself will not cause accidental release of the extinguishing liquid, which is a relatively safe failure mode. This device is not limited to the type of aircraft 1; it can be used for rotary-wing UAVs, unmanned helicopters, and other aircraft that receive continuous extinguishing liquid supply from ground-based equipment via tethered supply lines and release the extinguishing liquid during flight.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly compensated and pressure-stabilized aviation fire extinguishing liquid release device, comprising an airborne bracket for mounting on an aircraft, a nozzle disposed on the airborne bracket, and a tethered supply pipe connecting the nozzle to a ground-based liquid supply system, characterized in that, An airborne mechanical pressure regulating valve that rises and falls with the aircraft is connected in series upstream of the nozzle. The mechanical pressure regulating valve includes a valve body, a valve core, a pressure regulating spring, and a differential diaphragm assembly. The differential diaphragm assembly includes a first diaphragm and a second diaphragm that are rigidly connected. The effective area of ​​the second diaphragm is larger than that of the first diaphragm. An isolation cavity is formed between the two diaphragms and the atmosphere through a breathing hole. The side of the first diaphragm away from the isolation cavity is a feedback cavity that is connected to the inlet side of the nozzle through a feedback channel. The side of the second diaphragm away from the isolation cavity is a reference cavity that is connected to a reference pressure tapping part through a reference channel. The reference pressure tapping point is connected to the outlet side of the ground liquid supply equipment by a continuous liquid column, so that the reference pressure in the reference chamber decreases as the flight altitude of the aircraft increases; The resultant force of the pressure on the inlet side of the mechanical pressure regulator acting on the valve core is zero in the direction of movement of the valve core; The differential diaphragm assembly is drivenly connected to the valve core. The force exerted by the reference pressure on the second diaphragm is in the opposite direction to the sum of the force exerted by the pressure in the feedback chamber on the first diaphragm and the spring force of the pressure regulating spring, so that the inlet pressure of the nozzle decreases as the reference pressure decreases.

2. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, It also includes a reference pipe laid in parallel with the tethered supply pipe. The lower end of the reference pipe is connected to the outlet side of the ground supply equipment. The upper end of the reference pipe is a closed end that is only connected to the reference channel. The reference pressure tapping part is the upper end of the reference pipe. The reference pipe has no continuous flow when the nozzle releases the extinguishing liquid in a steady state.

3. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The reference pressure tapping point is the pipe section on the tethered liquid supply pipe located on the inlet side of the mechanical pressure regulating valve. The reference channel is led out from this pipe section and connected to the reference cavity along the outer wall of the valve body of the mechanical pressure regulating valve. The outlet diameter of the nozzle is fixed and the ground liquid supply equipment operates at a constant outlet pressure.

4. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The rated operating height is set as the vertical distance from the nozzle outlet to the horizontal target surface, the rated depression angle is the downward tilt angle of the nozzle axis relative to the horizontal plane, the outlet velocity is the outlet velocity of the nozzle at the rated inlet pressure when it is at the rated operating height and the rated depression angle, and the jet flight time is the time taken for the extinguishing liquid to travel from the nozzle to the horizontal target surface in this state. The ratio of the effective area of ​​the second diaphragm to the effective area of ​​the first diaphragm is 1.2 to 5.0, and the relative deviation between the ratio of the effective areas and the set value is no greater than 5%. The set value is the square of the quotient, which is the ratio of the product of the outlet flow velocity and the product of the gravitational acceleration and the jet flight time.

5. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The first diaphragm and the second diaphragm are rigidly connected by a connecting disc with a fixed outer diameter. The periphery of the second diaphragm is pressed against the valve body by a replaceable sizing ring. The effective area of ​​the second diaphragm is defined by the inner diameter of the sizing ring and the outer diameter of the connecting disc. The valve body is equipped with multiple sizing rings with different inner diameters.

6. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The pressure regulating spring is a tension spring. One end of the pressure regulating spring is attached to the differential diaphragm assembly, and the other end is attached to a threaded adjusting seat screwed onto the valve body. The threaded adjusting seat protrudes from the valve body and is equipped with a locking nut. The product of the full adjustment stroke of the valve core and the stiffness of the pressure regulating spring shall not exceed 2% of the spring force of the pressure regulating spring under rated operating conditions.

7. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The pressure tapping port of the feedback channel is a pressure tapping hole opened on the inner wall of the nozzle inlet section and flush with the inner wall, and the feedback channel is provided with a damping hole.

8. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The valve core is a lift-type valve core that mates with the valve seat. The valve core is connected to the differential diaphragm assembly via a valve stem. The valve stem passes through the isolation cavity and is guided by a guide sleeve fixed to the valve body. The valve core is provided with a balance piston section, and the valve body is provided with a balance cylinder bore that slides and seals with the balance piston section and is isolated from the outlet cavity downstream of the valve core. The balance cylinder bore is connected to the inlet side of the mechanical pressure regulator through a pressure-feeding through hole opened in the valve core. The cross-sectional area of ​​the balance cylinder bore is equal to the sum of the area enclosed by the diameter of the valve seat and the cross-sectional area of ​​the valve stem, so that the effective pressure-bearing area of ​​the valve core acting on the pressure on the inlet side of the mechanical pressure regulator in two opposite directions on the valve stem axis is equal.

9. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, A vent valve is provided on the pipe section between the mechanical pressure regulating valve and the nozzle. The opening pressure of the vent valve is 1.1 to 1.3 times the rated inlet pressure of the nozzle, and is lower than the lowest allowable working pressure among the pipe section, the nozzle, and the feedback chamber.

10. The aviation fire extinguishing liquid release device according to claim 1, characterized in that, The airborne support includes a base fixed to the aircraft and a pitch adjustment mount rotatably supported on the base about a horizontal axis, with the nozzle and the mechanical pressure regulating valve both mounted on the pitch adjustment mount.

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