Gas turbine engine heat management system
A heat management system of a gas turbine engine for cooling oil and heating fuel, includes an oil circuit having parallel connected first and second branches. The first branch includes a fuel/oil heat exchanger and a first fixed restrictor in series and the second branch includes an air cooled oil cooler and a second fixed restrictor. The first and second fixed restrictors limit respective oil flows through the first and second branch differently, in response to viscosity changes of the oil caused by temperature changes of the oil during engine operation to modify oil distribution between the first and second branches.
1. A heat management system of a gas turbine engine for cooling oil and heating fuel, the heat management system comprising an oil circuit having a first branch and a second branch connected in parallel, the first branch including a fuel/oil heat exchanger for transferring heat from an oil flow through the first branch to a fuel flow, and a first fixed restrictor for restricting the oil flow through the first branch, wherein the first fixed restrictor includes a diaphragm having a flow orifice, the second branch including an air cooled oil cooler for air cooling an oil flow through the second branch and a second fixed restrictor for restricting the oil flow through the second branch, wherein the second fixed restrictor includes a plurality of holes extending through a body, the plurality of holes being smaller in diameter and longer in axial length than the flow orifice of the first fixed restrictor such that the second fixed restrictor has a total flow contact area greater than a total flow contact area of the first fixed restrictor so that in response to an oil viscosity increase, a flow resistance increase of the second fixed restrictor is greater than a flow resistance increase of the first fixed restrictor to modify oil flow distribution between the first and second branches.
2. The heat management system as defined in claim 1 wherein the first fixed restrictor is disposed downstream of the fuel/oil heat exchanger and the second fixed restrictor is disposed downstream of the air cooled oil cooler.
3. The heat management system as defined in claim 2 wherein the first branch further comprises a pressure relief valve disposed downstream of the fuel/oil heat exchanger and in parallel connection with the first fixed restrictor.
4. The heat management system as defined in claim 1 comprising an oil pump disposed upstream of the oil circuit.
5. The heat management system as defined in claim 1 comprising an engine oil manifold disposed downstream of the oil circuit.
6. The heat management system as defined in claim 1 wherein the fuel flow is directed from an engine fuel supply to an engine fuel control unit.
7. The heat management system as defined in claim 1 wherein the first fixed restrictor is a calibrated diaphragm restrictor.
8. A heat management system of a gas turbine engine for cooling oil and heating fuel, the heat management system comprising an oil circuit having connected a first branch and a second branch in a parallel configuration, the first branch including a fuel/oil heat exchanger for transferring heat from an oil flow through the first branch to a fuel flow, and a first fixed restrictor disposed downstream of the fuel/oil heat exchanger for restricting the oil flow through the first branch, the second branch including an air cooled oil cooler for air cooling an oil flow through the second branch and a second fixed restrictor disposed downstream of the air cooled oil cooler for restricting the oil flow through the second branch, wherein the first fixed restrictor includes a diaphragm having a flow orifice and the second fixed restrictor includes a plurality of holes extending through a body, the plurality of holes being smaller in diameter and longer in axial length than the flow orifice of the first fixed restrictor, such that the second fixed restrictor has a total flow contact area greater than a total flow contact area of the first fixed restrictor so that a flow resistance increase of the second fixed restrictor is greater than a flow resistance increase of the first fixed restrictor in response to an oil viscosity increase.
9. The heat management system as defined in claim 8 wherein the first branch comprises a pressure relief valve disposed downstream of the fuel/oil heat exchanger and in parallel connection with the first fixed restrictor.
10. The heat management system as defined in claim 8 wherein the flow orifice of the first fixed restrictor has an annular edge having an edge tip angle of less than 90 degrees.
11. The heat management system as defined in claim 8 wherein each of the holes of the second fixed restrictor has a diameter smaller than an axial length of the hole.