Variable cooling of secondary circuit of fuel nozzles

Abstract

A system includes an injector including a scheduling valve assembly and a nozzle in fluid communication with the scheduling valve assembly. The injector includes two fluid circuits, a primary circuit and a secondary circuit, between the inlet of the injector and two respective outlets for staged flow output. A cooling circuit is in fluid communication with the inlet of the injector. The cooling circuit is in thermal communication with the secondary circuit for selectively cooling the secondary circuit at low flow and no flow conditions of the secondary circuit. A separate valve is connected in fluid communication in the cooling circuit for controlling flow through the cooling circuit. The separate valve is configured for active control regardless of pressure at the inlet of the injector. The scheduling valve assembly is configured for passive control of the primary and secondary circuits based on pressure at the inlet of the injector.

1 . A system comprising:
 an injector including a scheduling valve assembly and a nozzle in fluid communication with the scheduling valve assembly, wherein the scheduling valve assembly is configured for regulation of flow from an inlet of the injector to the nozzle, wherein the injector includes two fluid circuits between the inlet of the injector and two respective outlets for staged flow output from the nozzle, wherein a first one of the two fluid circuits is a primary circuit, and wherein a second one of the two fluid circuits is a secondary circuit;   a cooling circuit in fluid communication with the inlet of the injector, wherein the cooling circuit is in thermal communication with the secondary circuit for selectively cooling the secondary circuit at low flow and no flow conditions of the secondary circuit;   a separate valve connected in fluid communication in the cooling circuit for controlling flow through the cooling circuit, wherein the separate valve is configured for active control regardless of pressure at the inlet of the injector, wherein the scheduling valve assembly is configured for passive control of the primary and secondary circuits based on pressure at the inlet of the injector, and wherein the cooling circuit is connected in fluid communication to empty into the primary circuit at a position in the primary circuit that is downstream of the scheduling valve assembly; and   a pressure matching orifice in the primary circuit downstream of the inlet of the injector and upstream of a point where the cooling circuit empties into the primary circuit so flow from the cooling circuit is accepted into the primary circuit.   
     
     
         2 . The system as recited in  claim 1 , wherein a valve spool of the scheduling valve assembly is biased to a closed position by one or more biasing members of the scheduling valve assembly, wherein the valve spool is configured to regulate flow from the inlet of the injector to each of the primary and secondary circuits, and wherein the valve spool includes a scheduling surface configured to vary flow area through the secondary circuit based on position of the valve spool within the scheduling valve assembly. 
     
     
         3 . The system as recited in  claim 2 , wherein the separate valve is a solenoid valve that has an inlet, an outlet, and a solenoid valve member configured to control flow through the solenoid valve from the inlet to the outlet based on electrical power applied to an armature of the solenoid valve. 
     
     
         4 . The system as recited in  claim 3 , wherein the inlet of the solenoid valve is connected in fluid communication with the inlet of the injector, and wherein the outlet of the solenoid valve is connected in fluid communication with the cooling circuit, and wherein the cooling circuit is in thermal communication with the secondary circuit. 
     
     
         5 . The system as recited in  claim 3 , wherein the solenoid valve is a binary valve configured for binary operation either allowing or disallowing flow through the cooling circuit without an intermediate flow condition between allowing or disallowing flow. 
     
     
         6 . The system as recited in  claim 3 , wherein the solenoid valve is a modulating valve configured to vary flow between fully allowing and fully disallowing flow through the cooling circuit with intermediate flow conditions between allowing and disallowing flow. 
     
     
         7 . The system as recited in  claim 1 , further comprising a check valve in fluid communication upstream of where the primary, secondary, and cooling circuits connect to the inlet of the injector. 
     
     
         8 . (canceled) 
     
     
         9 . The system as recited in  claim 1 , wherein loss of electrical power to the separate valve allows the valve spool to position itself at a position determined by mechanical components and to regulate fuel flow as per a scheduling surface. 
     
     
         10 . The system as recited in  claim 1 , wherein the injector is a first injector in a plurality of injectors each connected in fluid communication with a single manifold for supplying fuel to each injector in the plurality of injectors including the primary, secondary, and cooling circuits of the first injector. 
     
     
         11 . (canceled) 
     
     
         12 . The system as recited in  claim 10 , wherein each injector in the plurality of injectors is as recited in  claim 1  including a respective separate valve as recited in  claim 1  connected thereto. 
     
     
         13 . The system as recited in  claim 12 , further comprising a controller electrically connected to the separate valves for individual control thereof. 
     
     
         14 . The system as recited in  claim 12 , further comprising a controller electrically connected to the separate valves for ganged control thereof. 
     
     
         15 . The system as recited in  claim 10 , wherein
 the secondary circuit outlets to a spray outlet of the first injector.