Midshaft rating for turbomachine engines
A turbomachine engine includes an engine core including a high-pressure compressor, a high-pressure turbine, and a combustion chamber. The engine core has a length (L CORE ), and the high-pressure compressor has an exit stage diameter (D CORE ). A power turbine is in flow communication with the high-pressure turbine. A low-pressure shaft is coupled to the power turbine and characterized by a midshaft rating from one hundred fifty (ft/sec) 1/2 to three hundred thirty (ft/sec) 1/2 . The low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second. The turbomachine engine is configured to operate up to the redline speed without passing through a critical speed associated with a first-order bending mode of the low-pressure shaft. A high-pressure shaft is coupled to the high-pressure compressor and the high-pressure turbine and is characterized by a high-speed shaft rating from 1.5 to 6.2, and a ratio of L CORE /D CORE is from 2.1 to 4.3.
1. A turbomachine engine comprising:
an engine core including a high-pressure compressor including eight stages, nine stages, ten stages, or eleven stages, a high-pressure turbine, and a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine, the engine core having a length (L CORE ), and the high-pressure compressor having an exit stage diameter (D CORE );
a power turbine in flow communication with the high-pressure turbine;
a low-speed shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between one hundred fifty (ft/sec) 1/2 and three hundred thirty (ft/sec) 1/2 , wherein the low-speed shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec), and wherein the turbomachine engine is configured to operate up to the redline speed without passing through a critical speed associated with a first-order bending mode of the low-speed shaft; and
a high-speed shaft coupled to the high-pressure compressor and the high-pressure turbine, the high-speed shaft characterized by a high-speed shaft rating (HSR) between 1.5 and 6.2, and a ratio of L CORE /D CORE is between 2.1 and 4.3, wherein HSR is given by:
HSR
=
1
k
*
N
2
R
/
L
*
D
C
O
R
E
*
(
L
C
O
R
E
D
C
O
R
E
)
2
,
where N2 R/L is a redline speed of the high-speed shaft, and k is a constant with a value of 10 6 inch-RPM.
2. The turbomachine engine of claim 1 , wherein an exhaust gas temperature of the turbomachine engine at redline speeds of the high-speed shaft is between 1,063° C. and 1,282° C.
3. The turbomachine engine of claim 1 , wherein the high-pressure turbine includes one stage or two stages.
4. The turbomachine engine of claim 1 , wherein at least one of the high-pressure compressor, the high-pressure turbine, or the power turbine comprises a ceramic matrix composite (CMC) material.
5. The turbomachine engine of claim 1 , wherein N2 R/L is between 10,580 RPM and 35,788 RPM.
6. The turbomachine engine of claim 1 , wherein L CORE /D CORE is a function of a high-speed shaft operating parameter (HSP X ), wherein HSP X is given by:
H
S
P
X
=
(
A
e
x
)
2
*
P
S
T
D
*
O
P
R
T
/
O
F
N
T
/
O
*
(
N
S
t
g
/
10
)
2
,
where N Stg is a number of stages in the high-pressure compressor, A EX is an area of an exit stage of the high-pressure compressor, P STD is standard pressure, OPR T/O is an overall pressure ratio of the turbomachine engine at takeoff flight conditions corresponding to a maximum thrust rating for an engine core configuration, and FN T/O is a sea-level static thrust of the turbomachine engine at takeoff flight conditions corresponding to the maximum thrust rating for the engine core configuration, and
wherein L CORE /D CORE is less than MAX(4.8-0.088*(HSP X ), 3.18-0.015*(HSP X )) or less than
4
.
0
8
(
HSP
X
-
8
)
0
.
1
4
.
7. The turbomachine engine of claim 6 , wherein HSP X is between 3.8 in 2 and 69.1 in 2 .
8. The turbomachine engine of claim 6 , wherein A EX is between 11 in 2 and 95 in 2 .
9. The turbomachine engine of claim 6 , wherein P STD is approximately 14.7 psi.
10. The turbomachine engine of claim 6 , wherein OPR T/O is between 26.3 and 82.
11. The turbomachine engine of claim 6 , wherein FN T/O is between 12,674 lbf and 107,480 lbf.
12. The turbomachine engine of claim 6 , wherein A EX is given by
A EX =π*(R TIP,EX 2 −R HUB,EX 2 ), where R TIP,EX is a radius of a tip of a high-pressure compressor blade of the exit stage of the high-pressure compressor, and R HUB,EX is a radius of a hub of the high-pressure compressor at the exit stage.
13. The turbomachine engine of claim 12 , wherein R TIP,EX is between 4.73 in. and 15.83 in.
14. The turbomachine engine of claim 12 , wherein R HUB,EX is between 4.31 in. and 14.85 in.
15. The turbomachine engine of claim 1 , wherein the high-speed shaft is characterized by a second high-speed shaft rating (HSR LP ) given by:
H
S
R
L
P
=
1
k
*
N
1
r
/
l
*
D
C
O
R
E
*
(
L
C
O
R
E
D
C
O
R
E
)
2
,
where
N
1
r
l
is the redline speed of the low-speed shaft, and k is a constant with a value of 10 6 inch-RPM.
16. The turbomachine engine of claim 15 , wherein HSR LP is between 0.8 and 1.6.
17. A turbomachine engine comprising:
an engine core including a high-pressure compressor, a high-pressure turbine, and a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine, the engine core having a length (L CORE ), and the high-pressure compressor having an exit stage diameter (D CORE );
a power turbine in flow communication with the high-pressure turbine;
a low-speed shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between two hundred (ft/sec) 1/2 and three hundred thirty (ft/sec) 1/2 , wherein the low-speed shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec), and wherein the turbomachine engine is configured to operate up to the redline speed without passing through a critical speed associated with a first-order bending mode of the low-speed shaft; and
a high-speed shaft coupled to the high-pressure compressor and the high-pressure turbine, the high-speed shaft characterized by a high-speed shaft rating (HSR) between 1.5 and 6.2, and a ratio of L CORE /D CORE is between 2.1 and 4.3, wherein HSR is given by:
HSR
=
1
k
*
N
2
R
L
*
D
CORE
*
(
L
CORE
D
CORE
)
2
,
where N2 R/L is a redline speed of the high-speed shaft, and k is a constant with a value of 10 6 inch-RPM.
18. The turbomachine engine of claim 17 , wherein L CORE /D CORE is a function of a high-speed shaft operating parameter (HSP X ) given by:
HSP
X
=
(
A
e
x
)
2
*
P
STD
*
OPR
T
O
F
N
T
O
*
(
N
Stg
1
0
)
2
,
where N Stg is a number of stages in the high-pressure compressor, A EX is an area of an exit stage of the high-pressure compressor, P STD is standard pressure, OPR T/O is an overall pressure ratio of the turbomachine engine at takeoff flight conditions corresponding to a maximum thrust rating for an engine core configuration, and FN T/O is a sea-level static thrust of the turbomachine engine at takeoff flight conditions corresponding to the maximum thrust rating for the engine core configuration, and
wherein L CORE /D CORE is less than MAX(4.8−0.088*(HSP X ), 3.18−0.015*(HSP X )) or less than
4
.
0
8
(
HSP
X
-
8
)
0.14
.
19. The turbomachine engine of claim 18 , wherein HSP X is between 3.8 in 2 and 69.1 in 2 .
20. The turbomachine engine of claim 18 , wherein an exhaust gas temperature of the turbomachine engine at redline speeds of the high-speed shaft is between 1,063° C. and 1,282° C.