Integral rocket-ramjet open loop fuel control system

• US 4,263,781 A
• Filed: 07/25/1979
• Issued: 04/28/1981
• Est. Priority Date: 07/25/1979
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Harner, Kermit I., Patrick, John P.
• Primary Examiner(s): Garrett, Robert E.
• Application Number:
  US06/060,443
• Time in Patent Office: 643 Days
• Field of Search: 60/245, 60/250, 60/243, 60/270 R
• US Class Current: 60/243
• CPC Class Codes: F02C 9/28 Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed F02C9/30 - F02C9/38, F02C9/44 take precedence
• CPC Class Codes: F05D 2270/122 Speed or Mach number

Abstract

In an integral rocket-ramjet having a combustor which initially serves as a rocket combustion chamber for booster propellant, and after the booster propellant is expended, serves as a ramjet combustor where fuel and air are burned, a fuel control system is described for the ramjet stage by which ram burner light-off is automatically initiated upon transition from rocket to ramjet propulsion. The fuel control regulates fuel flow to the combustor over the entire flight regime and responds to operating conditions to provide a light-off schedule, to stabilize the shock wave in the air inlet, to provide a maximum fuel-to-air ratio limit, to limit the maximum vehicle Mach number, and to prevent lean burner blowout by providing a minimum fuel-to-air ratio limit. Mach number limiting is performed in closed loop fashion, while the other functions are scheduled or open loop controls. Fuel flow to combustion chamber pressure ratio is used to provide fuel-to-air ratio limits, actual combustion chamber pressure being measured to provide the desired fuel flow signal.

Claims

1. In an integral rocket-ramjet vehicle having a combustion chamber, a source of ramjet fuel and an inlet supplying air to said combustion chamber, a fuel control for modulating the flow of fuel from said source to said combustion chamber upon termination of the rocket phase of vehicle operation, comprising:

means responsive to termination of the rocket phase of operation for producing a first signal indicative of desired fuel-to-air ratio upon ignition of said fuel in said combustion chamber, and indicatived of a maximum fuel-to-air ratio after ignition of said fuel;

means responsive to selected vehicle operating conditions for producing a second signal indicative of a desired fuel-to-air ratio for limiting inlet operating pressures and thereby maintaining optimum performance of said inlet;

means for measuring vehicle velocity and producing therefrom a third signal indicative of desired fuel-to-air ratio to maintain vehicle velocity below a preselected limit;

least select means for receiving and selecting the one of said first, second and third signals which produces the lowest fuel-to-air ratio; and

fuel scheduling means includingd valve means responsive to said selected fuel-to-air ratio signal for metering the desired amount of fuel from said source to said combustion chamber.

2. A fuel control as in claim 1 and further including:

means for scheduling a minimum fuel-to-air ratio for said vehicle;

most select means receiving the fuel-to-air ratio signal selected by said least select means and said minimum fuel-to-air ratio signal and selecting the signal which produces the highest fuel-to-air ratio;

and means for feeding the fuel-to-air ratio signal selected by said most select means to said fuel scheduling means.

3. A fuel control as in claim 1 including igniter means for initiating combustion of said fuel in said combustion chamber, and in which said means responsive to the termination of the rocket phase of operation includes:

means responsive to the admission of air from said inlet to said combustion chamber for producing an ignition signal;

a timing means;

means for producing a pressure signal indicative of the altitude of said vehicle;

means for initiating said timing means and producing a timing signal upon the occurrence of said ignition signal;

and scheduling means responsive to said timing signal and to said pressure signal for producing said first signal, said first signal scheduling a reduced fuel-to-air ratio with a magnitude and time duration as a function of said pressure signal and adapted to provide optimum fuel flow to said combustion chamber during the ignition phase, said first signal then increasing in magnitude to schedule a maximum fuel-to-air ratio.

4. A fuel control as in claim 3 and including time delay means,

means for feeding said ignition signal to said time delay means whereby said ignition signal is delayed in time;

and means feeding said time delayed ignition signal to said igniter means.

5. A fuel control as in claim 4 and including a shut-off solenoid for said valve means whereby said valve means is closed during the rocket phase of operation;

and means for feeding said ignition signal to said shut-off solenoid to open said valve means upon occurence of said ignition signal.

6. A fuel control as in claim 1 in which said means for producing said second signals comprises:

means for producing a signal indicative of vehicle Mach number;

means for producing a signal indicative of vehicle angle of attack;

means responsive to said vehicle Mach number signal and said vehicle angle of attack signal for scheduling a fuel-to-air ratio signal optimally biased for inlet air temperature;

means for measuring the temperature of the air in said inlet and producing an inlet temperature signal indicative thereof; and

means for multiplying said air inlet temperature biased fuel-to-air ratio signed by said inlet temperature signal.

7. A fuel control as in claim 1 in which said means for producing said third signal comprises:

means producingd a pressure signal indicative of the altitude of said vehicle;

means responsive to said pressure signal for scheduling a Mach number reference signal;

means for producing a signal indicative of actual vehicle Mach number;

means for comparing said Mach number reference signal with said actual vehicle Mach number signal to produce a Mach number error signal;

and gain means for converting said Mach number error signal into said third signal.

8. A fuel control as in claim 2 in which each of said fuel-to-air ratio signals is scheduled as the ratio of fuel flow to combustion chamber pressure;

means for measuring actual combustion chamber pressure and producing a signal indicative thereof;

means for multiplying said fuel-to-air ratio signal selected by said most select means by said actual combustion chamber pressure signal to produce a desired fluel flow signal; and

means for feeding said desired fuel flow signal to said scheduling means to actuate said valve means in responsed thereto.