# Patent

## Title
Turbojet comprising a bleeding system for bleeding air in said turbojet

## Abstract

A turbojet comprising a high-pressure compressor with several compression stages in which the pressure rises in a direction of air flow, from a low pressure to a high pressure, passing through intermediate pressures, and a system to bleed air in the turbojet and deliver the air to an air system. The bleeding system comprises a first air intake to bleed air at low pressure, a second air intake to bleed air at an intermediate pressure, a first valve and a second valve having inlets connected to the first air intake, a compressor having an inlet connected to the second valve outlet, a high-pressure valve connected to the second air intake, and a control valve connected to the air system, and a controller to control the opening and closing of the valves depending on the pressures at the first and second air intakes.

## Background
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of the French patent application No. 1451235 filed on Feb. 17, 2014, the entire disclosures of which are incorporated herein by way of reference.
BACKGROUND OF THE INVENTION
The present invention relates to an aircraft turbojet comprising a system for bleeding air from said turbojet, an aircraft comprising at least one such turbojet, and a method for controlling such a turbojet.
FIG. 1 shows an aircraft bypass turbojet 10 equipped with a prior art bleeding system 100 that is intended to bleed air in the turbojet 10 and to deliver said air to an air system 60, such as the conditioned air system 60 of the aircraft cabin.
The turbojet 10 comprises:

    
    
        a fan 12 intended to generate a flow of air in the turbojet 10 in a direction of displacement 50 of air in the turbojet, in which case, as is known, the flow of air then moves downstream of the fan in a primary vein of the turbojet 10 or in a secondary vein thereof,
        a compressor 14 that comprises a low-pressure compressor 16 downstream of the fan 12 and a high-pressure compressor 18 arranged downstream of the low-pressure compressor 16,
        a turbine 20 that comprises a high-pressure turbine 22 downstream of the high-pressure compressor 18 and a low-pressure turbine 24 downstream of the high-pressure turbine 22.
    
    


The air pushed by the fan and traveling in the primary vein then passes in succession through the low-pressure compressor 16, the high-pressure compressor 18, the high-pressure turbine 22, and the low-pressure turbine 24 so as to be ejected to the outside.
Between the high-pressure compressor 18 and the high-pressure turbine 22, the air passes through a combustion chamber 26.
The high-pressure compressor 18 comprises a plurality of compression stages in which the pressure rises, from upstream to downstream in the direction of displacement 50, from a low pressure at the first stage to a high pressure at the last stage, passing through an intermediate pressure in the vicinity of the middle stage.
The bleeding system 100 comprises:

    
    
        a first air intake 102 intended to bleed the air at the intermediate pressure in the high-pressure compressor 18,
        a second air intake 104 intended to bleed the air at high pressure in the high-pressure compressor 18,
        a check valve 106 fluidically connected to the first air intake 102 that prevents the air from moving toward said first air intake 102,
        a high-pressure valve 108 fluidically connected to the second air intake 104 and controlled so as to be open or closed alternatively,
        a control valve 110 intended to control the pressure of the flow of air passing therethrough, the outlet of the high-pressure valve 108 and the outlet of the check valve 106 being fluidically connected to the same inlet of the control valve 110,
        a cooler 112 intended to cool the air passing therethrough, the outlet of the control valve 110 being fluidically connected to an inlet of the cooler 112 and an outlet of the cooler 112 being fluidically connection to the air system 60 of the aircraft,
        a controller 114 intended to control the high-pressure valve 108 and the control valve 110.
    
    


The air necessary for the cooling performed in the cooler 112 is bled through a system of pipes 116 arranged downstream of the fan 12 in the secondary air vein of the turbojet 10.
The air pressure at the outlet of the cooler 112 must be compatible with the air pressure that must be injected in the air system 60. In the case of a pressurized cabin, the air pressure typically must be between 137895.14 Pa (20 psia) and 206842.72 Pa (30 psia).
Thus, when the pressure at the first air intake 102 is above a first threshold, typically 275790.29 Pa (40 psia), the air necessary for operation of the bleeding system 100 is bled at the first air intake 102, and when the pressure in the bleeding system 100 is below a second threshold, typically 206842.72 Pa (30 psia), the air necessary for operation of the bleeding system 100 is bled at the second air intake 104.
To this end, a pressure sensor measures the value of the pressure at the first air intake 102 and another pressure sensor 111 measures the value of the pressure in the bleeding system 100. Such a pressure sensor 111 is installed, for example, downstream of the junction between the outlet of the check valve 106 and the outlet of the high-pressure valve 108.
The bleeding system 100 then operates as follows:

    
    
        when the pressure at the first air intake 102 is above a first threshold, the controller 114 orders the closure of the high-pressure valve 108,
        the air is then bled at the first air intake 102, passes through the check valve 106 and supplies the control valve 110,
        when the pressure in the bleeding system 100 is below the second threshold, the controller 114 orders the opening of the high-pressure valve 108,
        the air is then bled at the second air intake 104, passes through the high-pressure valve 108 and supplies the control valve 110, and the check valve 106 prevents the air from returning to the turbojet 10,
        the controller 114 controls the control valve 110 in accordance with the air pressure that is to be obtained,
        the air at the outlet of the control valve 110 passes through the cooler 112, then supplies the air system 60.
    
    


Such a layout is not always satisfactory in terms of energy consumption.
SUMMARY OF THE INVENTION
One object of the present invention is to propose a turbojet comprising a bleeding system that does not demonstrate the disadvantages of the prior art and that in particular allows a reduction of consumption.
To this end, a turbojet comprising a high-pressure compressor with a number of compression stages in which the pressure rises, from upstream to downstream in a direction of displacement of the air, from a low pressure to a high pressure passing through a succession of intermediate pressures, and a bleeding system intended to bleed air in said turbojet and to deliver said air to an air system are proposed, characterized in that the bleeding system comprises:

    
    
        a first air intake intended to bleed the air at low pressure in the high-pressure compressor,
        a second air intake intended to bleed the air at an intermediate pressure in the high-pressure compressor,
        a check valve of which the inlet is fluidically connected to the first air intake and which prevents the air from moving toward the first air intake,
        a first valve of which the inlet is fluidically connected to the outlet of the check valve,
        a second valve of which the inlet is fluidically connected to the outlet of the check valve,
        a compressor of which the inlet is fluidically connected to the outlet of the second valve,
        a high-pressure valve fluidically connected to the second air intake,
        a cooler intended to cool the air passing therethrough, the outlet of the high-pressure valve being fluidically connected to an inlet of the cooler, and the outlet of the cooler being fluidically connected to the inlets of the first valve and of the second valve,
        a control valve intended to control the pressure of the flow of air passing therethrough, the outlet of the first valve and the outlet of the compressor being fluidically connected to the same inlet of the control valve, and an outlet of the control valve being fluidically connected to the air system,
        a low-pressure sensor intended to measure the value of the pressure at the first air intake and to transmit information concerning this pressure to the controller,
        an intermediate pressure sensor intended to measure the value of the pressure at the second air intake and to transmit information concerning this pressure to the controller, and
        a controller intended to control the opening and closing of the high-pressure valve, the first valve, the second valve and the control valve depending on the pressure at the first air intake and the pressure at the second air intake.
    
    


This particular arrangement makes it possible to reduce the consumption of fuel, and in addition this arrangement makes it possible to reduce the thermal stresses exerted on the cooler, since the air passing therethrough is no longer air at high pressure, but air at intermediate pressure.



BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being provided in conjunction with the accompanying drawings, in which:
FIG. 1 shows an aircraft bypass turbojet equipped with a bleeding system according to the prior art,
FIG. 2 shows an aircraft bypass turbojet equipped with a bleeding system in accordance with a first embodiment of the invention,
FIG. 3 shows an aircraft bypass turbojet equipped with a bleeding system in accordance with a second embodiment of the invention, and
FIG. 4 shows an aircraft comprising a bypass turbojet according to the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 and FIG. 3 show the turbojet 10 equipped with a bleeding system 200, 300 according to the invention that is intended to bleed air in the turbojet 10 and to deliver said air to an air system 60, such as the conditioned air system 60 of the aircraft cabin.
The turbojet 10 comprises the same elements as that in FIG. 1, in particular a low-pressure compressor 16 and a high-pressure compressor 18. These elements bear the same references.
The high-pressure compressor 18 comprises a number of states of compression in which the pressure rises, from upstream to downstream in a direction of displacement of the air 50 in the turbojet, from a low pressure at the first stage to a high pressure at the last stage, passing through a succession of intermediate pressures at each of the intermediate stages.
The bleeding system 200 of FIG. 2 comprises:

    
    
        a first air intake 202 intended to bleed air at low pressure in the high-pressure compressor 18,
        a second air intake 204 intended to bleed air at an intermediate pressure in the high-pressure compressor 18,
        a check valve 206 of which the inlet is fluidically connected to the first air intake 202 and which prevents the air from moving toward the first air intake 202,
        a first valve 215 of which the inlet is fluidically connected to the outlet of the check valve 206, and controlled so as to be open or closed alternatively,
        a second valve 216 of which the inlet is fluidically connected to the outlet of the check valve 206, and controlled so as to be open or closed alternatively,
        a compressor 218 of which the inlet is fluidically connected to the outlet of the second valve 216,
        a high-pressure valve 208 fluidically connected to the second air intake 204 and controlled so as to be open or closed alternatively,
        a cooler 212 intended to cool the air passing therethrough, the outlet of the high-pressure valve 208 being fluidically connected to an inlet of the cooler 212, and the outlet of the cooler 212 being fluidically connected to the inlets of the first valve 215 and of the second valve 216,
        a control valve 210 intended to control the pressure of the flow of air passing therethrough, the outlet of the first valve 215 and the outlet of the compressor 218 being fluidically connected to the same inlet of the control valve 210, and an outlet of the control valve 210 being fluidically connected to the air system 60 of the aircraft, and
        a controller 214 intended to control the opening and closing of the high-pressure valve 208, the first valve 215, the second valve 216 and the control valve 210 depending on the pressure at the first air intake 202 and the pressure at the second air intake 204.
    
    


The second air intake 204 is located on a stage arranged upstream in relation to the last stage of the high-pressure compressor 18.
The air necessary for the cooling performed in the cooler 212 is bled here by means of a system of pipes 116 arranged downstream of the fan 12 in the secondary air vein of the turbojet 10.
The air pressure at the outlet of the control valve 210 must be compatible with the air pressure that must be injected in the air system 60. In the case of a pressurized cabin, the air pressure typically must be between 137895.14 Pa (20 psia) and 206842.72 Pa (30 psia). The controller 214 thus controls the opening of the control valve 210 in accordance with the pressure to be delivered.
Typically, in a turbojet 10 in takeoff mode, the pressure of the air at the first air intake 202, that is to say the low pressure, is approximately 206842.72 Pa (30 psia), and during idling the pressure of the air at the second air intake 204, that is to say the intermediate pressure, fluctuates around 103421.36 Pa (15 psia).
Thus, when the pressure at the first air intake 202 is above a first threshold, typically approximately 137895.14 Pa (20 psia), the air necessary for operation of the bleeding system 200 is bled at the first air intake 202, when the pressure at the first air intake 202 is below the first threshold and above a second threshold, typically approximately 103421.36 Pa (15 psia), the air necessary for operation of the bleeding system 200 is bled at the first air intake 202 and compressed by the compressor 218, when the pressure at the first air intake 202 is below the second threshold and the pressure at the second air intake 204 is above the first threshold, the air necessary for operation of the bleeding system 200 is bled at the second air intake 204, and when the pressure at the second air intake 204 is below the first threshold and above the second threshold, the air necessary for operation of the bleeding system 200 is bled at the second air intake 204 and compressed by the compressor 218.
More particularly, the pressure at the outlet of the bleeding system 200 must be equal to or greater than 137895.14 Pa (20 psia) and, depending on the values of the pressures at the first air intake 202 and at the second air intake 204, the air coming from one or other of the air intakes 202, 204 will be bled with or without compression in order to reach at least 137895.14 Pa (20 psia).
The position of the second air intake 204 is selected such that the air pressure at the outlet of the compressor 218 can always be above the first threshold.
A low-pressure sensor 203 measures the value of the pressure at the first air intake 202 and an intermediate pressure sensor 205 measures the value of the pressure at the second air intake 204, and each of the sensors 203 and 205 transmits the information concerning the pressure measured by said sensor to the controller 214 so that said controller controls the opening and closing of the appropriate valves.
Thus, when the pressure at the first air intake 202 is above the first threshold, the controller 214 orders the opening of the first valve 215, the closing of the second valve 216, and the closing of the high-pressure valve 208.
A method for controlling the turbojet 10 thus comprises:

    
    
        a first control step during which the controller 214 orders the opening of the first valve 215, the closing of the second valve 216, and the closing of the high-pressure valve 208 when the pressure at the first air intake 202 is above a first threshold,
        a second control step during which the controller 214 orders the closing of the first valve 215, the opening of the second valve 216, and the closing of the high-pressure valve 208 when the pressure at the first air intake 202 is below the first threshold and above a second threshold,
        a third control step during which the controller 214 orders the opening of the first valve 215, the closing of the second valve 216, and the opening of the high-pressure valve 208 when the pressure at the first air intake 202 is below the second threshold and the pressure at the second air intake 204 is above the first threshold, and
        a fourth control step during which the controller 214 orders the closing of the first valve 215, the opening of the second valve 216, and the opening of the high-pressure valve 208 when the pressure at the second air intake 204 is below the first threshold and above the second threshold.
    
    


These four steps are alternative and the controller 214 performs one or the other after having compared the value of the pressure measured by the low-pressure sensor 203 and the value of the pressure measured by the intermediate pressure sensor 205 in relation to the first threshold and the second threshold.
The air coming from the first air intake 202 then passes in succession through the check valve 206, the first valve 215 and the control valve 210 and is guided to the air system 60.
Thus, when the pressure at the first air intake 202 is below the first threshold and above the second threshold, the controller 214 orders the closing of the first valve 215, the opening of the second valve 216, and the closing of the high-pressure valve 208.
The air coming from the first air intake 202 then passes in succession though the check valve 206, the second valve 216, the compressor 218 and the control valve 210 and is guided to the air system 60.
Thus, when the pressure at the first air intake 202 is below the second threshold and the pressure at the second air intake 204 is above the first threshold, the controller 214 orders the closing of the second valve 216, the opening of the first valve 215, and the opening of the high-pressure valve 208.
The air coming from the second air intake 204 then passes in succession through the high-pressure valve 208, the cooler 212, the first valve 215, the control valve 210 and is guided to the air system 60. The check valve 206 then prevents the air coming from the cooler 212 from returning toward the first air intake 202.
Thus, when the pressure at the second air intake 204 is below the first threshold and above the second threshold, the controller 214 orders the closing of the first valve 215, the opening of the second valve 216, and the opening of the high-pressure valve 208.
The air coming from the second air intake 204 then passes in succession through the high-pressure valve 208, the cooler 212, the second valve 216, the compressor 218, the control valve 210 and is guided to the air system 60. The check valve 206 then prevents the air coming from the cooler 212 from returning toward the first air intake 202.
The displacement of the second air intake from high pressure to intermediate pressure makes it possible to save fuel during the descent and during idling. Thus, for each displacement upstream of the second air intake 204 by one compression stage, the saving can be up to 0.3%.
In the embodiment of the invention in FIG. 2, the compressor 218 is driven by an electric power source of the aircraft.
FIG. 3 shows a bleeding system 300 in which the compressor 218 is driven with the aid of a bleed of air performed within said bleeding system 300.
The bleeding system 300 thus also comprises:

    
    
        a compression valve 302 of which the inlet is fluidically connected to the outlet of the second valve 216, and
        a turbine 304 of which the inlet is fluidically connected to the outlet of the compression valve 302 and which is intended to drive the compressor 218.
    
    


The controller 214 is then also provided in order to control the opening and closing of the compression valve 302.
The operation of the bleeding system 300 is thus identical to that of the first embodiment when the pressure at the first air intake 202 is above the first threshold and when the pressure at the first air intake 202 is below the second threshold and the pressure at the second air intake 204 is above the first threshold. The controller 214 thus orders the closing of the compression valve 302.
By contrast, when the pressure at the first air intake 202 is below the first threshold and above the second threshold or when the pressure at the second air intake 204 is below the first threshold and above the second threshold, the controller 214 orders the closing of the first valve 215, the opening of the second valve 216, the opening of the compression valve 302, and, as appropriate, the closing or opening of the high-pressure valve 208.
In each of the two cases, the air coming from the first air intake 202 or from the second air intake 204 passes through the second valve 216 and the compressor 218 as described above, whereas some of the air is bled at the outlet of the second valve 216 in order to pass through the compression valve 302 and then supply the turbine 304.
During the second control step and during the fourth control step, the controller 214 also orders the opening of the compression valve 302.
The controller 214 orders the opening of the compression valve 302 in order to distribute the air between the compressor 218 and the turbine 304. In accordance with one particular embodiment, 66% of the air coming from the second valve 216 passes through the compressor 218 and 33% passes through the turbine 304.
While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

## Claims

1. A method for controlling a turbojet, the turbojet including a high-pressure compressor with a number of compression stages in which pressure rises, from upstream to downstream in a direction of displacement of air, by passing through a succession of pressures, and a bleeding system configured to bleed air in said turbojet and to deliver said bled air to an air system, the bleeding system comprising: a first air intake configured to bleed air at low pressure in the high-pressure compressor, a second air intake configured to bleed air at an intermediate pressure in the high-pressure compressor, a check valve having an inlet fluidically connected to the first air intake and preventing bled air from moving toward the first air intake, a first valve having an inlet fluidically connected to an outlet of the check valve, a second valve having an inlet fluidically connected to the outlet of the check valve, a second compressor having an inlet fluidically connected to an outlet of the second valve, a high-pressure valve fluidically connected to the second air intake, a cooler configured to cool air passing therethrough, an outlet of the high-pressure valve being fluidically connected to an inlet of the cooler, and an outlet of the cooler being fluidically connected to the inlet of the first valve and the outlet of the cooler being fluidically connected to the inlet of the second valve, a control valve configured to control a pressure of a flow of air passing therethrough, an outlet of the first valve and an outlet of the second compressor each being fluidically connected to an inlet of the control valve, and an outlet of the control valve being fluidically connected to the air system, a low-pressure sensor configured to measure a first pressure value at the first air intake and to transmit information concerning the first pressure value to a controller, an intermediate pressure sensor configured to measure a second pressure value at the second air intake and to transmit information concerning the second pressure value to the controller, and the controller being configured to control an opening and closing of each of the high-pressure valve, the first valve, the second valve and the control valve depending on the first pressure value at the first air intake and the second pressure value at the second air intake, and wherein, the method comprises:
a first control step during which the controller orders the opening of the first valve, the closing of the second valve, and the closing of the high-pressure valve when the first pressure value at the first air intake is above a first threshold,
a second control step during which the controller orders the closing of the first valve, the opening of the second valve, and the closing of the high-pressure valve when the first pressure value at the first air intake is below the first threshold and above a second threshold,
a third control step during which the controller orders the opening of the first valve, the closing of the second valve, and the opening of the high-pressure valve when the first pressure value at the first air intake is below the second threshold and the second pressure value at the second air intake is above the first threshold, and
a fourth control step during which the controller orders the closing of the first valve, the opening of the second valve, and the opening of the high-pressure valve when the second pressure value at the second air intake is below the first threshold and above the second threshold.

2. The method as claimed in claim 1, wherein the turbojet comprises a compression valve having an inlet fluidically connected to the outlet of the second valve and a turbine having an inlet fluidically connected to an outlet of the compression valve and configured to drive the compressor, and the method further comprises ordering an opening of the compression valve during the second control step and during the fourth control step.

3. The method as claimed in claim 1, wherein the first threshold is 20 psia.

4. The method as claimed in claim 1, wherein the second threshold is 15 psia.

5. A turbojet comprising:
a high-pressure compressor with a number of compression stages in which pressure rises, from upstream to downstream in a direction of displacement of air, by passing through a succession of pressures, and
a bleeding system configured to bleed air in said turbojet and to deliver said bled air to an air system, the bleeding system comprising:
a first air intake configured to bleed air at low pressure in the high-pressure compressor,
a second air intake configured to bleed air at an intermediate pressure in the high-pressure compressor,
a check valve having an inlet fluidically connected to the first air intake and preventing bled air from moving toward the first air intake,
a first valve having an inlet fluidically connected to an outlet of the check valve,
a second valve having an inlet fluidically connected to the outlet of the check valve,
a second compressor having an inlet fluidically connected to an outlet of the second valve,
a high-pressure valve fluidically connected to the second air intake,
a cooler configured to cool air passing therethrough, an outlet of the high-pressure valve being fluidically connected to an inlet of the cooler, the cooler configured to receive air from the high-pressure valve, and an outlet of the cooler being fluidically connected to the inlet of the first valve and the outlet of the cooler being fluidically connected to the inlet of the second valve,
a control valve configured to control a pressure of a flow of air passing therethrough, an outlet of the first valve and an outlet of the second compressor each connected to an inlet of the control valve, and an outlet of the control valve being fluidically connected to the air system,
a low-pressure sensor configured to measure a first pressure value at the first air intake and to transmit information concerning the first pressure value to a controller,
an intermediate pressure sensor configured to measure a second pressure value at the second air intake and to transmit information concerning the second pressure value to the controller, and
the controller being configured to control an opening and closing of each of the high-pressure valve, the first valve, the second valve and the control valve depending on the first pressure value at the first air intake and the second pressure value at the second air intake,
wherein the inlet of the control valve is configured to receive air from one of the outlet of the first valve and the outlet of the second compressor, depending on the controlled opening and closing of each of the high-pressure valve, the first valve, and the second valve.

6. The turbojet as claimed in claim 5, further comprising:
a compression valve having an inlet fluidically connected to the outlet of the second valve, and
a turbine having an inlet fluidically connected to an outlet of the compression valve and configured to drive the second compressor,
the controller being configured to control an opening and closing of the compression valve.

7. An aircraft comprising the turbojet as claimed in claim 5.