Gas turbine engine fuel return valve and system

A fuel return valve, comprising:

• a servo control valve including a servo fuel inlet, a servo fuel outlet, a first servo fuel control pressure port, and a second servo fuel control pressure port, the servo control valve configured to selectively control relative fluid pressures at the first and second servo fuel control pressure ports;
• a flow-level select and shut-off valve including first and second cold fuel inlet ports, first and second hot fuel inlet ports, a return-to-tank outlet port, a control pressure inlet port, a first control pressure port, a second control pressure port, and a valve element movable to at least a shut-off position, a mid-flow position, and a max-flow position, the control pressure inlet port in fluid communication with the servo fuel inlet, the first control pressure port coupled to and in fluid communication with the first servo fuel control pressure port, the second control pressure port coupled to and in fluid communication with the second servo fuel control pressure port,
• wherein the flow-level select and shut-off valve is configured such that:
• the valve element is in the shut-off position when the fluid pressure at the first servo fuel control pressure port is greater than the fluid pressure at the second servo fuel control pressure port, whereby the first and second cold fuel inlet ports and the first and second hot fuel inlet ports are both fluidly isolated from the return-to-tank outlet port,
• the valve element is in the mid-flow position when the fluid pressure at the first servo fuel control pressure port is equal to the fluid pressure at the second servo fuel control pressure port, whereby only the first cold fuel inlet port and only the first hot fuel inlet port are in fluid communication with the return-to-tank outlet port, and
• the valve element is in the max-flow position when the fluid pressure at the first servo fuel control pressure port is less than the fluid pressure at the second servo fuel control pressure port, whereby both the first and second cold fuel inlet ports and both the first and second hot fuel inlet ports are in fluid communication with the return-to-tank outlet port.

A fuel return flow control system, comprising:

• a servo control fuel source;
• a cold fuel return flow source;
• a hot fuel return flow source;
• and
• a fuel return valve in fluid communication with the servo control fuel source, the cold fuel return flow source, and the hot fuel return flow source, the fuel return valve comprising:
• an electrohydraulic servo control valve including a servo fuel inlet, a servo fuel outlet, a first servo fuel control pressure port, and a second servo fuel control pressure port, the servo fuel inlet in fluid communication with the servo control fuel source, the electrohydraulic servo control valve configured to selectively control relative fuel pressures at the first and second servo fuel control pressure ports;
• and
• a flow-level select and shut-off valve including first and second cold fuel inlet ports, first and second hot fuel inlet ports, a return-to-tank fuel outlet port, a control pressure inlet port, a first control pressure port, a second control pressure port, and a valve element movable to at least a shut-off position, a mid-flow position, and a max-flow position, the control pressure inlet port in fluid communication with the servo control fuel source, the first control pressure port coupled to and in fluid communication with the first servo fuel control pressure port, the second control pressure port coupled to and in fluid communication with the second servo fuel control pressure port, the first and second cold fuel inlet ports in fluid communication with the cold fuel return flow source, and the first and second hot fuel inlet ports in fluid communication with the hot fuel return flow source,
• wherein the flow-level select and shut-off valve is configured such that:
• the valve element is in the shut-off position when the fuel pressure at the first servo fuel control pressure port is greater than the fuel pressure at the second servo fuel control pressure port, whereby the first and second cold fuel inlet ports and the first and second hot fuel inlet ports are both fluidly isolated from the return-to-tank fuel outlet port,
• the valve element is in the mid-flow position when the fuel pressure at the first servo fuel control pressure port is equal to the fuel pressure at the second servo fuel control pressure port, whereby only the first cold fuel inlet port and only the first hot fuel inlet port are in fluid communication with the return-to-tank fuel outlet port, and
• the valve element is in the max-flow position when the fuel pressure at the first servo fuel control pressure port is less than the fuel pressure at the second servo fuel control pressure port, whereby both the first and second cold fuel inlet ports and both the first and second hot fuel inlet ports are in fluid communication with the return-to-tank fuel outlet port.