Control of aircraft bleed air stage mixing

• US 5,161,364 A
• Filed: 04/01/1991
• Issued: 11/10/1992
• Est. Priority Date: 04/01/1991
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Rtx Corporation)
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Kos, Joseph M., Bruun, Eugene R.
• Primary Examiner(s): Casaregola, Louis J.
• Application Number:
  US07/678,502
• Time in Patent Office: 589 Days
• Field of Search: 60/39.02, 60/39.07, 60/39.093, 60/39.29, 137/606, 454/71, 454/72, 454/73, 454/74
• US Class Current: 60/772
• CPC Class Codes: B64D 13/04 Automatic control of pressure
• CPC Class Codes: F02C 6/08 the gas being bled from the gas-turbine compressor
• CPC Class Codes: F02C 7/14 of fluids in the plant , e.g. lubricant or fuel F02C7/185 takes precedence
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A gas turbine engine bleed air system in which air flow from a high pressure and a low pressure compressor stage of a gas turbine engine are mixed together by controlling the pressure at the outlet of a proportional valve. The pressure is controlled by modulating the flow area of the proportional valve through which the high pressure air flows in order to achieve a scheduled pressure value. The scheduled pressure value is determined as a function of a temperature error at a location downstream of the proportional valve in the bleed air system.

Claims

1. A bleed air system for receiving high pressure and low pressure compressed air from a gas turbine engine to provide a temperature regulated flow of mixed bleed air substantially equal to a desired mixed air temperature value at the output of a mixing conduit, comprising:

first means, for mixing in the mixing conduit, the low pressure compressed air with a modulated flow of high pressure compressed air provided by a proportional valve, said proportional valve modulating the flow of high pressure air in response to a valve area command signal;

means for providing a sensed pressure signal indicative of the actual pressure of the mixed air flow;

means for providing a sensed temperature signal indicative of the actual temperature of the mixed air flow; and

controller means for receiving said sensed pressure signal, said sensed temperature signal, and the desired mixed air temperature value, for providing a pressure reference signal, where the value of said pressure reference signal is set as a function of the difference between said sensed temperature signal and the desired mixed air temperature value, and for calculating said valve area command signal in response to the difference between said pressure reference signal and said sensed pressure signal.

2. The bleed air system of claim 1, wherein said first means further comprises:

a check valve, disposed to receive the low pressure compressed air, and discharge the air into the mixing conduit when the air pressure of the mixed bleed air flow in the mixing conduit is less than or approximately equal to the air pressure of the low pressure compressed air, such that the air exiting said check valve will mix in the mixing conduit with air from said proportional valve, when said proportional valve and said check valve are both not fully closed.

3. The bleed air system of claim 1, wherein said controller means further comprises:

a first compensator, having an integrator, for an outer control loop on temperature with said sensed temperature signal as a temperature feedback signal; and

a second compensator, having a proportional plus integral path, for an inner control loop on pressure with said sensed pressure signal as a pressure feedback signal.

4. An apparatus for mixing together the high pressure and low pressure compressed air from a gas turbine engine, to create a temperature regulated mixed air flow, comprising:

a mixing conduit, having provision to receive compressed air from two or more sources;

first sensing means, for sensing air pressure in said mixing conduit, and for providing a pressure signal indicative therefore;

a first conduit;

second sensing means, for sensing air temperature in said first conduit, and for providing a temperature signal indicative thereof;

means for coupling said mixing conduit to said first conduit, such that the air flow from said mixing conduit enters said first conduit;

means for calculating and providing a valve command signal as a function of said pressure signal and said temperature signal; and

valve means, disposed to receive high pressure compressed air, for modulating in response to said valve command signal the flow area through which the high pressure compressed air passes, and for providing a regulated flow of high pressure compressed air into said mixing conduit, such that the flow area is modulated in response to said valve command signal to mix the low pressure and high pressure air within said mixing conduit in order to create the temperature regulated mixed air flow in said first conduit.

5. The apparatus of claim 4, further comprising:

a check valve, disposed to receive the low pressure compressed air, and allow the low pressure air to exit into said mixing conduit while the air pressure in said mixing conduit is approximately equal to or less than the air pressure of the low pressure compressed air.

6. The apparatus of claim 4, wherein said means for coupling further comprises:

a pressure regulating valve, disposed to receive air from said mixing conduit, and control the pressure of the air that is discharged into said first conduit.

7. An apparatus for mixing together the high pressure and low pressure compressed air from a gas turbine engine, to create a temperature regulated mixed air flow, comprising:

a check valve disposed to receive the low pressure compressed air;

a proportional valve, disposed to receive the high pressure compressed air, having a variable flow area responsive to a valve area command signal and through which the high pressure compressed air is discharged;

a mixing conduit, having a plurality of inlets, a first of said plurality of inlets for receiving air from said check valve, a second of said plurality of inlets for receiving air from said proportional valve, such that the air from each of said plurality of inlets is mixed to together within said mixing conduit and discharged as a temperature regulated flow of bleed air;

means for sensing the air pressure of said temperature regulated flow of bleed air, and for providing a pressure signal indicative thereof;

means for sensing the temperature of said temperature regulated flow of bleed air, and for providing a temperature signal indicative thereof; and

controller means for computing said valve area command signal as a function of said temperature signal and said pressure signal, such that said valve area command signal takes on a value that drives the temperature of the temperature regulated flow of bleed air towards a desired reference temperature value.

8. A method of providing a temperature regulated flow of bleed air by mixing together a low pressure bleed air flow and a high pressure bleed air flow from a gas turbine engine and discharging the temperature regulated flow of bleed air to systems requiring bleed air, comprising the steps of:

modulating in response to a command signal value, the flow area of a proportional valve through which the high pressure bleed air flows;

combining the modulated high pressure bleed air flow and the low pressure bleed air flow in a mixing conduit;

sensing the temperature of the mixed air flow in the mixing conduit;

sensing the pressure of the mixed air flow in the mixing conduit; and

computing said command signal value in response to the sensed temperature and pressure values.