Propeller blade angle control system
A control circuit for changing the angle of propeller blades includes a propeller pitch change mechanism, and a fixed-displacement pump providing the supply of oil from an engine oil return system. A valve has an outlet port to direct oil from a cavity of the valve, and a pitch port in fluid communication with the pitch change mechanism. A spool of the valve is operable between a first position and a second position to respectively open and close the outlet port, and direct oil flow away from or to the pitch change mechanism.
1. An oil system of a turboprop gas turbine engine having a propeller of an aircraft, the propeller having a plurality of variable pitch propeller blades, the oil system comprising:
an engine oil return system having a supply of oil; and
a propeller blade angle control circuit communicating with the engine oil return system, including:
a propeller pitch change mechanism;
a fixed-displacement pump communicating between the propeller pitch change mechanism and the supply of oil; and
a valve disposed downstream of the pump, the valve having a valve body with a cavity therein, the valve body including an outlet port, an inlet port, and a pitch port, the inlet port fluidly communicating with the pump, the outlet port fluidly communicating with the engine oil return system via an oil cooling line, and the pitch port fluidly communicating with the propeller pitch change mechanism, the valve including a spool within the cavity displaceable between a first position and a second position within the valve body;
wherein in the first position, the spool permits communication through the outlet port to the oil cooling line, and in the second position the spool substantially blocks the outlet port to permit oil to flow through the pitch port to the propeller pitch change mechanism, the spool displaceable within the cavity to always leave the pitch port at least partially unblocked.
2. The oil system as defined in claim 1 , wherein the spool is in the second position during transient operation of the propeller pitch change mechanism.
3. The oil system as defined in claim 2 , wherein during transient operation of the propeller pitch change mechanism, the spool increases an opening of the pitch port while simultaneously blocking the outlet port.
4. The oil system as defined in claim 1 , wherein the spool is in the first position during steady-state operation of the propeller pitch change mechanism.
5. The oil system as defined in claim 4 , wherein in the first position the spool permits oil to flow through the outlet port and the pitch port.
6. The oil system as defined in claim 1 , wherein the spool is displaceable within the cavity to modify an opening of the pitch port.
7. The oil system as defined in claim 1 , wherein the outlet port includes a first outlet port and a second outlet port, the first outlet port remaining continuously unblocked, the spool in the first position permitting oil to flow through the second outlet port to the oil cooling line, and the spool in the second position substantially blocking the second outlet port.
8. A propeller blade angle control circuit, comprising:
a propeller pitch change mechanism;
a fixed-displacement pump located upstream of the propeller pitch change mechanism and providing a supply of oil from an engine oil return system to the propeller pitch change mechanism; and
a valve disposed between the pump and the propeller pitch change mechanism, the valve having a valve body with a cavity therein, the valve body including an outlet port, an inlet port, and a pitch port, the inlet port fluidly communicating with the pump, the outlet port fluidly communicating with the engine oil return system via an oil cooling line, and the pitch port fluidly communicating with the propeller pitch change mechanism, the valve including a spool within the cavity displaceable between a first position and a second position within the valve body;
wherein in the first position, the spool permits communication through the outlet port to the oil cooling line, and in the second position the spool substantially blocks the outlet port to permit oil to flow through the pitch port to the propeller pitch change mechanism, the spool displaceable within the cavity to always leave the pitch port at least partially unblocked.
9. The circuit as defined in claim 8 , wherein the spool is in the second position during transient operation of the propeller pitch change mechanism.
10. The circuit as defined in claim 9 , wherein during transient operation of the propeller pitch change mechanism, the spool increases an opening of the pitch port while simultaneously blocking the outlet port.
11. The circuit as defined in claim 8 , wherein the spool is in the first position during steady-state operation of the propeller pitch change mechanism.
12. The oil system as defined in claim 1 , wherein the spool is displaceable within the cavity to modulate or control a size of an opening of the pitch port and to control an opening of the outlet port.