Patent Application
20100258675
The present invention relates to a ram-air duct for supplying ambient air in an aircraft, and to a process for controlling a mass flow of ambient air or cooling air through a ram-air duct.
Ram-air ducts with an air inlet and with a ram-air inlet duct extending downstream of the air inlet, with a ram-air active portion extending downstream of the inlet duct and also with a ram-air outlet duct extending downstream of the ram-air active portion, with an air outlet at the downstream end of said ram-air outlet duct, are employed in modern aircraft for the purpose of supplying various systems located on board the aircraft, such as an air-conditioning system for example, with ambient air. In the ram-air active portion there may be arranged, for example, heat-exchangers of an air-conditioning plant of the aircraft, which are perfused by supplied cold ambient air. During flight, ambient air flows through the air inlet into the ram-air inlet duct and into the ram-air active portion, whereas mechanical devices, such as, for example, injectors or fans arranged in the ram-air duct for the purpose of generating a flow of ambient air through the ram-air duct, are utilised when the aircraft is located on the ground.
In order to enable an adaptation of the flow of ambient air supplied through the ram-air duct to the differing requirements of the systems supplied with the ambient air in a manner depending on whether the aircraft is located in the air or on the ground and depending on the demand for flow of ambient air, in a region of the air inlet and also in a region of the air outlet of the ram-air duct a movable element, such as a flap for instance, is ordinarily provided, which permits an enlargement or a diminution or even a total closing of the flow cross-section of the air inlet or of the air outlet. A respective movable element may be, for example, an adjustable inlet-duct flap or outlet-duct flap which, depending on its position, enables a flow cross-section of the air inlet or air outlet that is desired in the given case.
In present-day modern passenger aircraft most ram-air ducts exhibit a similar structure or similar components.
If in flight the first flap and the second flap are moved out of their position closing the ram-air inlet duct (represented by continuous lines in
A conventional ram-air outlet duct is ordinarily equipped with an outlet-duct flap as shown in
The mass flow of ambient air through the ram-air duct can consequently be controlled by an appropriate positioning of the ram-air inlet-duct flap(s) and/or of the ram-air outlet-duct flap. For example, the mass flow of ambient air through the ram-air duct can be increased by opening the ram-air inlet-duct flap(s) and/or the ram-air outlet-duct flap if a control temperature, for example a temperature of a component of the air-conditioning plant of the aircraft registered by means of a suitable sensor, exceeds a predetermined threshold value. In similar manner, the mass flow of ambient air through the ram-air duct can be diminished by closing the ram-air inlet-duct flap(s) and/or by closing the ram-air outlet-duct flap if the control temperature falls below a predetermined threshold value. In conventional control processes the ram-air-duct flaps at the ram-air inlet and at the ram-air outlet are opened up and closed up synchronously with one another, and a linear dependence between an outlet parameter and an inlet parameter is conformed to.
The term ‘inlet parameter’ is understood here to mean a parameter or a value that characterises an inlet cross-section at the inlet of the ram-air duct, such as, for instance, the position of the movable element at the inlet of the ram-air inlet duct. In this connection, the position of the movable element may be specified as an opening angle of the movable element or as a spacing of a region, in particular an end region, of the movable element from a fixed region of the outer skin of the aircraft surrounding the inlet.
The term ‘outlet parameter’ is understood here to mean a parameter or a value that characterises an outlet cross-section at the outlet of the ram-air outlet duct, such as, for instance, the position of the movable element at the outlet of the ram-air outlet duct. In this connection, the position of the movable element may be specified as an opening angle of the movable element or as a spacing of a region, in particular an end region, of the movable element from a fixed region of the outer skin of the aircraft surrounding the outlet.
Since, by reason of the fact that in the open state the flap projects from the outer skin of the aircraft, the opening of the ram-air outlet-duct flap increases the aerodynamic drag and hence the fuel consumption of the aircraft, in connection with the control of the mass flow of ambient air through the ram-air duct a position of the flap that is as closed as possible should always be striven for. Recent aerodynamic investigations have shown, in addition, that an open ram-air outlet-duct flap generates a higher additional aerodynamic drag than an open ram-air inlet-duct flap or open ram-air inlet-duct flaps. In order to guarantee a sufficient mass flow of ambient air through the ram-air duct, in normal operation of conventionally designed ram-air ducts, and given compliance with a linear relationship between the outlet parameter and the inlet parameter, as shown in
The object of the present invention consists in specifying a ram-air duct for supplying ambient air in an aircraft, as well as a process for controlling a mass flow of ambient air or cooling air through a ram-air duct, which enable a diminution of the additional aerodynamic drag caused by the ram-air duct in flying operation of the aircraft.
This object is achieved by a ram-air duct with the features of Claim 1 and also by a process for controlling a mass flow of ambient air or cooling air through a ram-air duct, with the features of Claim 8.
In accordance with the invention, the idea underlying the solution to the task is to adapt the conventional, substantially linear dependence between the inlet parameter, for example the position of the ram-air inlet-duct flaps, and the outlet parameter, for example the position of the ram-air outlet-duct flap, in the control of the mass flow of ambient air in such a way that the ram-air outlet is opened only minimally over a control range that is as large or wide as possible and an increase in the amount of cooling air is realised on demand by an appropriate control of the ram-air inlet-duct flaps.
A ram-air duct according to the invention includes a ram-air inlet duct and a ram-air outlet duct which is arranged downstream of the ram-air inlet duct and in fluid communication with the ram-air inlet duct. The ram-air duct further includes a movable element which is arranged at an inlet of the ram-air inlet duct and adapted to set an inlet parameter E of the inlet, wherein a smaller inlet parameter corresponds to a smaller flow cross-section of the inlet and wherein a larger inlet parameter corresponds to a larger flow cross-section of the inlet. The inlet parameter is adjustable within a control range from a minimal inlet parameter up to a maximal inlet parameter. The ram-air duct further includes a movable element which is arranged at an outlet of the ram-air outlet duct and adapted to set an outlet parameter A of the outlet, wherein a smaller outlet parameter corresponds to a smaller flow cross-section of the outlet and wherein a larger outlet parameter corresponds to a larger flow cross-section of the outlet. The outlet parameter is adjustable within a control range from a minimal outlet parameter up to a maximal outlet parameter.
The outlet parameter and the inlet parameter are linked together by a function ƒ, so that an outlet parameter corresponding to a value f(E) of the function ƒ is assigned to each inlet parameter. Furthermore, a substantially linear function L is defined in such a way that the end values of the inlet parameter and of the outlet parameter at the lower ends of the respective control ranges are connected together with the end values at the upper ends of the respective control ranges by this linear function L.
In accordance with the invention, the function ƒ linking the inlet parameter and the outlet parameter together is chosen in such a way that the gradient of this function in the case of the minimal inlet parameter is less than the gradient of the aforementioned linear function and greater than or equal to zero (first condition).
The gradient of the function ƒ within a first inlet-parameter range, which extends from the minimal inlet parameter up to a relatively greater, first predetermined value of the inlet parameter, is preferentially less than the gradient of the linear function.
Within an inlet-parameter range in which the gradient of the function ƒ is less than the gradient of the linear function L the control of the flow of cooling air through the ram-air duct is effected more intensely by a change, of the inlet parameter than by a change of the outlet parameter. In other words, the movable element at the outlet is, in comparison with the conventional control in accordance with the linear function, retracted comparatively further than the movable element at the inlet, and the control of the amount of cooling air takes place substantially by means of the movable element at the inlet. A further advantage is that, by reason of the smaller outlet parameter in relation to the conventional control, the cooling air flows out of the ram-air outlet duct at a higher speed, generating an additional thrust.
By way of second further condition, the value of the function ƒ for each inlet parameter within the control range thereof may be less than the value of the linear function. By way of third further condition, the gradient of the function in the case of the maximal inlet parameter may be greater than the gradient of the linear function. The gradient of the function within a second inlet-parameter range, which extends from a second predetermined inlet parameter up to the maximal inlet parameter, is preferentially greater than the gradient of the linear function.
In further advantageous configurations, either the aforementioned first condition and the aforementioned second condition, or the aforementioned second condition and the aforementioned third condition, or the aforementioned first condition, the aforementioned second condition and the aforementioned third condition, may be satisfied.
The movable element at the inlet may include a ram-air inlet-duct flap. The movable element at the outlet may include a ram-air outlet-duct flap.
The inlet parameter may be a flow cross-section of the inlet or a parameter characterising the position of the movable element at the inlet. The inlet parameter may, in particular, be an opening angle of an inlet-duct flap or a spacing of a region, in particular an end region, of a ram-air inlet-duct flap from a fixed region of an outer skin of the aircraft surrounding the inlet.
The outlet parameter may be a flow cross-section of the outlet or a parameter characterising the position of the movable element at the outlet. The outlet parameter may, in particular, be an opening angle of an outlet-duct flap or a spacing of a region, in particular an end region, of a ram-air outlet-duct flap from a fixed region of the outer skin of the aircraft surrounding the outlet.
In the ram-air duct the inlet parameter and/or the outlet parameter can be set continuously within their respective control ranges. Alternatively, a stepwise setting of the inlet parameter and/or of the outlet parameter within their respective control ranges is conceivable. In this connection, for the inlet parameter within the control range thereof a plurality of discrete inlet parameters may have been predetermined, and for the outlet parameter within the control range thereof likewise a plurality of discrete outlet parameters may have been predetermined. The respective discrete outlet parameters and the respective discrete inlet parameters can be linked together by the function ƒ. The movable elements at the inlet and outlet are brought into such respective discrete positions that the throughput of cooling air remains minimal. An associated control temperature of the air-conditioning plant may lie within a range between a minimal and a maximal value. If an actual value of the control temperature exceeds the maximal value, the movable elements at the input and at the output are opened up by a respective step into a further discrete position, or opened. If the actual value of the control temperature falls below the minimal value, the movable elements are retracted by a respective step into a further discrete position, or closed. The magnitude and the location of the range of the control temperature of the air-conditioning plant are optimised in a manner depending on the particular given conditions of the plant or of the aircraft. This type of regulation with discrete inlet parameters and outlet parameters affords the further advantage that, by virtue of slighter wear and slighter attrition, the movable elements that are moved less frequently, for example ram-air-duct flaps, enhance the reliability of the air-conditioning plant and diminish the maintenance costs for users of the aircraft that are equipped with a ram-air duct of such a type.
The ram-air duct may further include a first control loop with an input and with an output for driving the movable element at the inlet, as well as a second control loop with an input and with an output for driving the movable element at the outlet. In this connection, at the output of the first control loop a control signal for setting a position of the movable element at the inlet may have been provided, and furthermore at the output of the second control loop a control signal for setting a position of the movable element at the outlet may have been provided. Lastly, a command variable that is common to both control loops is supplied to the input of the first control loop and to the input of the second control loop. This command variable is ascertained in a manner depending on a control temperature in the aircraft. This means that the positions of the movable elements at the inlet and at the outlet are dependent only on the command variable. This affords the further advantage that in the case of a fault, such as, for instance, the failure of an actuator, the movable elements can continue to control the throughput of cooling air without difficulty in terms of control engineering with the still functioning actuator. For the purpose of determining the command variable, in addition to the control temperature in the aircraft use may also be made of further parameters, such as, for example, a plant control temperature or a characteristic pressure in the ram-air duct.
Furthermore, a process is provided for controlling a mass flow of ambient air or cooling air through a ram-air duct. The ram-air duct includes a ram-air inlet duct and a ram-air outlet duct which is arranged downstream of the ram-air inlet duct and in fluid communication with the ram-air inlet duct. The ram-air duct further includes a movable element which is arranged at an inlet of the ram-air inlet duct and adapted to set an inlet parameter of the inlet, whereby a smaller inlet parameter corresponds to a smaller flow cross-section of the inlet and wherein a larger inlet parameter corresponds to a larger flow cross-section of the inlet. Furthermore, a movable element is present which is arranged at an outlet of the ram-air outlet duct and adapted to set an outlet parameter A of the outlet, wherein a smaller outlet parameter corresponds to a smaller flow cross-section of the outlet and wherein a larger outlet parameter corresponds to a larger flow cross-section of the outlet.
The process includes the following steps:
In accordance with the invention, the function ƒ is defined in such a way that the gradient of the function ƒ in the case of the minimal inlet parameter is less than the gradient of the linear function L and greater than or equal to zero (first condition).
The function ƒ is preferentially determined in such a way that the gradient of the function ƒ within a first inlet-parameter range, which extends from the minimal inlet parameter up to a relatively greater, first predetermined value of the inlet parameter, is less than the gradient of the linear function L within this inlet-parameter range.
As a result, the same advantages are achieved as with the ram-air duct with the features according to the invention.
In step (d) the function ƒ can be defined in such a way that the value of the function ƒ for each inlet parameter within the control range of the inlet parameter is less than the value of the linear function L (second condition).
Furthermore, in step (d) the function ƒ can be defined in such a way that the gradient of the function ƒ in the case of the maximal outlet parameter is greater than the gradient of the linear function L (third condition).
In advantageous configurations of the invention, either the aforementioned first condition and the aforementioned second condition, or the aforementioned second condition and the aforementioned third condition, or the aforementioned first condition and the aforementioned third condition, or the aforementioned first condition, the second condition and the third condition may be satisfied.
In a further preferred embodiment, a first range for the inlet parameter can be defined in such a way that the latter is greater than or equal to the minimal inlet parameter and less than the maximal inlet parameter, wherein a value of the outlet parameter has been predetermined that is greater than the minimal outlet parameter and less than or equal to the maximal outlet parameter. Furthermore, the function ƒ can be chosen in such a way that for all values of the inlet parameter within the first range it is greater than or equal to the minimal outlet parameter and less than or equal to the predetermined value of the outlet parameter. This means that within the first range the outlet parameter is varied and controlled only between the minimal outlet parameter and the predetermined value of the outlet parameter. If the inlet parameter has the minimal inlet parameter, the outlet parameter can be controlled within a range that extends from the predetermined value of the outlet parameter to the maximal outlet parameter. This means that a mass flow of cooling air through the ram-air duct with maximally opened inlet is controlled by means of the movable element at the outlet.
In an alternative preferred embodiment, the function ƒ within the first range can be defined as a linear function or as a quadratic function.
In a still further preferred embodiment, the first range may be subdivided into a first subrange, which extends from the minimal inlet parameter up to a relatively greater, predetermined value of the inlet parameter, and a second subrange, which extends from the predetermined value of the inlet parameter up to the maximal inlet parameter. In this connection, the function ƒ within the first subrange may be defined as a constant function, wherein the outlet parameter is set, in particular, to its minimal value. Within the second subrange the function ƒ may be defined as a linear function. This means that within the first subrange the mass flow of cooling air is controlled only by means of the movable element at the inlet, and the movable element at the outlet is held at the minimal outlet parameter, bringing about a maximal additional thrust and a minimal additional aircraft drag.
In an alternative preferred embodiment, the first range may again be subdivided into a first subrange, which extends from the minimal inlet parameter up to a relatively greater, predetermined value of the inlet parameter, and into a second subrange, which extends from the predetermined value of the inlet parameter up to the maximal inlet parameter. In this connection, the inlet parameter within the first subrange and/or within the second subrange is controlled either in a manner depending on a pressure measured downstream of the ram-air inlet duct or in a manner depending on a pressure measured in the ram-air outlet duct.
If within the first and/or within the second subrange the inlet parameter is controlled in a manner depending on a pressure measured downstream of the ram-air inlet duct, the ram-air duct preferentially further includes a first pressure sensor which is arranged downstream of the ram-air inlet duct. In this connection, a control value of the pressure can be determined in a manner depending on one or more parameters which have been selected from the group that comprises the following: the outlet parameter, such as, for instance, position of the outlet-duct flap, the flying conditions, such as, for instance, altitude, airspeed, and the ambient conditions, such as, for instance, the ambient temperature.
If the inlet parameter within the first and/or second subrange is controlled in a manner depending on a pressure measured in the ram-air outlet duct, the ram-air duct preferentially further includes a pressure sensor which is arranged in the ram-air outlet duct. In this connection, a control value of the pressure can be determined in a manner depending on one or more parameters which have been selected from the group that comprises the following: the outlet parameter, such as, for instance, a position of the outlet-duct flap, the flying conditions, such as, for instance, altitude or airspeed, and the ambient conditions, such as, for instance, an ambient temperature.
Preferred exemplary embodiments of a ram-air duct according to the invention and of the process according to the invention will be elucidated more fully in the following on the basis of the accompanying drawings. Shown therein are:
The ram-air inlet duct 20 exhibits at its upstream end a NACA inlet 22 recessed in the outer skin 42 of the aircraft. Furthermore, the ram-air inlet duct 20 includes a ram-air-duct flap which, in particular, is designed as a bipartite ram-air inlet-duct flap and includes a first movable element (first ram-air inlet-duct flap) 24, a second movable element (second ram-air inlet-duct flap) 24′ and also an actuator 26 for setting the positions of the first and second ram-air inlet-duct flaps 24, 24′. A diffuser 29 is arranged downstream of the ram-air inlet-duct flaps 24, 24′, in order to retard the flow of the ambient air supplied though the inlet 22 into the ram-air inlet duct 20. The actuator 26 is driven by a central control unit (not shown), i.e. it receives a control signal, whereupon the actuator simultaneously and synchronously sets the position of the ram-air inlet-duct flaps 24, 24′. In this connection, the ram-air inlet-duct flaps 24, 24′ can be positioned within a control range between a first or minimal position, in which the ram-air inlet-duct flaps 24, 24′ enable a minimal inlet parameter, and a second or maximal position, in which the inlet-duct flaps 24, 24′ enable a maximal inlet parameter. The term ‘inlet parameter’ is used here as a collective term for any parameters that are suitable to serve as characteristic parameter for the flow cross-section of the inlet of the ram-air inlet duct 20. The inlet parameter may be the flow cross-section of the inlet 22 itself, or even an angular position of a ram-air inlet-duct flap 24, 24′ or a spacing, in particular the spacing 28 shown in
In the example shown in
In flight, the flow of outside air through the inlet 22 and through the inlet cross-section enabled by the ram-air inlet-duct flaps 24, 24′ gets into the ram-air inlet duct 20. By reason of the retardation of the flow in the diffuser 29 of the ram-air inlet duct 20, some of the dynamic pressure of the flow is converted into static pressure. As a result, in the diffuser 29 and also at the input of the ram-air active portion 60 and at the input of the heat-exchangers 52, 54 a static overpressure, also designated as ram pressure, relative to the ambient pressure arises.
The ram-air outlet duct 30 exhibits an its downstream end an outlet 32, the flow cross-section of which can be set by means of a movable element, conventionally designed, as a rule, as a ram-air outlet-duct flap 34, within a control range between a minimal outlet parameter and a maximal outlet parameter. An actuator 46 which is likewise driven by the central control unit (not shown) serves for setting the position of the ram-air outlet-duct flap 34. An enlarged and schematically further simplified representation of the ram-air outlet duct 30 is shown in
Here the term ‘outlet parameter’ is used as a collective term for any parameters that may be representative of the size of the flow cross-section of the outlet 32. By way of outlet parameter, the flow cross-section of the outlet 32 itself, but also a position of the ram-air outlet-duct flap 34 determining the flow-cross-section of the outlet 32, for example, may be drawn upon. For example, the spacing 38 shown in
The ram-air outlet-duct flap 34 that has been opened up or opened generates, by reason of being flowed around by the outside air in the ram-air outlet duct, an overpressure relative to the ambient pressure, which has an effect at the output of the heat-exchangers 52, 54, in particular at the output of heat-exchanger 54. The differential pressure between the pressure at the input of heat-exchanger 52 and the pressure at the output of heat-exchanger 54 influences the mass flow of cooling air through the heat-exchangers 52, 54. The pressure ratios are influenced by the inlet parameter, in particular the position of the ram-air inlet-duct flaps 24, 24′, and the outlet parameter, in particular the position of the ram-air outlet-duct flap 34, and in principle can consequently be set independently of one another by the actuator 26 for setting the ram-air inlet-duct flaps 24, 24′ and by the actuator 46 for setting the ram-air outlet-duct flap 34.
Conventionally, the inlet parameter, in particular the positions of the ram-air inlet-duct flaps 24, 24′, and the outlet parameter, in particular the position of the ram-air outlet-duct flap 34, are set simultaneously and synchronously in a linear dependence relative to one another.
The outlet parameter A is characterised by the position of the ram-air outlet-duct flap 34 and, in the example shown in
Conventionally, linear actuators are employed at the ram-air-duct input and output, and the linear relationship L shown in
Therefore the conventional, linear dependence between the inlet parameter or the position of the ram-air inlet-duct flaps 24, 24′ and the outlet parameter or the position of the ram-air outlet-duct flap 34 in the control of the ram-air-duct flaps is modified in such a way that the ram-air outlet-duct flap 34 is opened as little as possible, i.e. minimally, starting from the minimal inlet parameter Amin, over a control range that is as long as possible and that, at the same time, over a control range that is as long as possible the ram-air inlet-duct flaps 24, 24′ undertake the control of the amount of ambient cooling air over a control range that is as long as possible, starting from the inlet parameter Emin or the minimal inlet-duct-flap position.
In comparison with the conventional ram-air-duct flap control with the linear relationship according to curve L in
i) the gradient of the function ƒ, which specifies the relationship between the outlet parameter and the inlet parameter in accordance with the equation A=ƒ(E), in the case of the minimal inlet parameter Emin and preferentially also within a first inlet-parameter range adjoining the minimal inlet parameter Emin (in
ii) The values of the function ƒ within the entire control range, i.e. within the entire range of the inlet parameter between the minimal inlet parameter Emin and the maximal inlet parameter Emax, are less than the value of the linear function L. In other words, the outlet parameter or position of the outlet-duct flap 34 pertaining to a respective inlet parameter or position of the inlet-duct flaps 24, 24′ within the entire control range according to the invention is less than the outlet parameter that was set in accordance with the conventional control algorithm, i.e. the linear relationship L.
iii) The gradient of the function ƒ in the case of the maximal inlet parameter Emax and preferentially also within a second inlet-parameter range extending from the maximal inlet parameter Emax towards smaller inlet parameters is greater than the gradient of the function L that connects together the end values (Emin, Amin) and (Emax, Amax) and that describes the conventional linear relationship between the outlet parameter and the inlet parameter.
In
An advantage of the control principle described previously herein consists in the fact that in normal operation of a flying aircraft the control of the amount of cooling air takes place within range B1. This means that in normal operation of the aircraft the ram-air outlet-duct flap 34 is located in a position with a smaller opening angle relative to the surface of the aircraft than in the case of a conventional flap control. This contributes distinctly towards a reduction of the additional aircraft drag. In addition, a thrust is also generated that at least partly compensates the additional drag generated by the ram-air duct 10. The ram-air-duct flaps 24, 24′, 34 are brought into the control range B2 only if an extremely high throughput of cooling air is required, i.e. if the air-conditioning plant has to achieve a particularly great cooling power and/or warmer ambient temperatures prevail. The positions of the ram-air-duct flaps 24, 24′, 34 for the transitions between ranges B1 and B2, i.e. in particular the maximal inlet parameter Emax, the predetermined outlet parameter Apredet and the maximal outlet parameter Amax, are determined and defined separately for each aircraft and each system.
In particular, within range B1 the position of the ram-air outlet-duct flap 34 is set as master default from the minimal position Amin up to the predetermined position Apredet, and the ram-air inlet-duct flaps 24, 24′ are opened by way of slave control from the minimal up to the maximal inlet parameter by means of the conformity with a physical law preset by the function ƒ, so that the pressure in the ram-air outlet duct 30 is kept as high as possible, the outlet-duct flap 34 is closed as far as possible, and the speed of the out flowing air is maximised. In connection with the definition of the conformity with a physical law (the function ƒ), care is taken to ensure that the ram-air inlet-duct flaps 24, 24′ are not opened further without demand (demand for cooling air) or benefit (cooling power), so that the additional aircraft drag is not increased unnecessarily thereby. The conformity with a physical law is determined, optimised and defined separately for each aircraft and each system. At least the following three possibilities for defining such a suitable conformity with a physical law are conceivable:
1.According to a defined conformity with a physical law, for each position of the ram-air outlet-duct flap 34 a position of the ram-air inlet-duct flaps 24, 24′ is defined, i.e., a function ƒ is defined that links together the position of the inlet-duct flaps and the position of the outlet-duct flap.
2. For a position of the ram-air outlet-duct flaps that has been preset in the given case by way of master control variable, the position of the ram-air inlet-duct flaps 24, 24′ is controlled in a manner depending on the pressure behind the ram-air inlet duct 20. To this end, a pressure sensor is arranged behind, i.e. downstream of, the ram-air inlet duct 20. The control value for the pressure is determined in a manner depending on the position of the ram-air outlet-duct flap 34 and can additionally be determined from the flying conditions and ambient conditions, such as, for instance, altitude, airspeed and ambient temperature.
3. For a respective position of the ram-air outlet-duct flap 34 as master default, the position of the ram-air inlet-duct flaps 24, 24′ is controlled in a manner depending on the pressure in the ram-air outlet duct 30. To this end, a pressure sensor is positioned in the ram-air outlet duct 30. The control-pressure value for the pressure is determined in a manner depending on the position of the ram-air outlet-duct flap 34 and may additionally be determined from the flying conditions and ambient conditions, such as, for instance, altitude, airspeed and ambient temperature.
By way of fixed conformity with a physical law, in particular the following possibilities for defining the function ƒ within range B1 are conceivable and are particularly easy to implement in terms of control engineering:
A) Within the entire range B1, i.e. within the control range of the outlet parameter between the minimal outlet parameter Amin and the predetermined outlet parameter Apredet, and also within the control range of the inlet parameter from Emin to Emax, a linear conformity with a physical law lin1, as shown in
B) Within the entire range B1, i.e. within the control range of the outlet parameter between Amin and Apredet and within the control range of the inlet parameter between Emin and Emax, a quadratic conformity with a physical law quad, as shown in
C) Within range B1 an intermittent linear conformity with a physical law is implemented, as shown in
D) In a modification of the quadratic conformity with a physical law described above under B), any other functional conformity with a physical law is conceivable that can be implemented in terms of control engineering and that presets a function ƒ with gradient increasing towards high inlet parameters, such as, for instance, a cubic or an exponential conformity with a physical law.
It can be particularly advantageous to control the positions of the ram-air-duct flaps 24, 24′, 34 in accordance with the conformities with a physical law described above not continuously but intermittently or in stepwise manner. In this connection, the inlet-duct flaps 24, 24′ and the outlet-duct flap 34 are set only to respective discrete positions. A discrete position Ei of the inlet-duct flaps 24, 24′ is assigned to a respective discrete position Ai of the ram-air outlet-duct flap 34 via the conformity with a physical law (for example, the function ƒ). The ram-air-duct flaps 24, 24′, 34 are brought into such a position that the throughput of cooling air remains minimal. In this connection, the control temperature of an air-conditioning plant may be located within a range between a minimal and a maximal value. If the actual value of the control temperature exceeds the maximal value, the ram-air-duct flaps 24, 24′, 34 are opened up further by one step to the respective next discrete position. If the actual value of the control temperature fails below the minimal value, the ram-air-duct flaps 24, 24′, 34 are retracted by a respective step to the next-smaller discrete position.
An advantage of this stepwise control consists in the fact that the ram-air-duct flaps 24, 24′, 34 are moved or operated less frequently, which may entail a slighter wear and a slighter attrition and may also enhance the reliability of the air-conditioning plant and reduce the maintenance costs for customers. The magnitude and the location of the range or the ranges of the control temperature of the plant are determined and optimised in a manner depending on the properties of the air-conditioning plant.
In the embodiments described above with reference to
The ram-air-flap control described above contributes towards diminishing the overall drag and, as a result, the fuel consumption of an aircraft and, as a result, contributes towards increasing the range of the aircraft.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 017 040.5 | Apr 2009 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| 61167930 | Apr 2009 | US |
