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, a high-pressure turbine, and a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine;
a power turbine in flow communication with the high-pressure turbine;
a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) from two hundred (ft/sec) 1/2 to three hundred thirty (ft/sec) 1/2 , wherein low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec), and 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; and
a high-pressure shaft coupled to the high-pressure compressor and the high-pressure turbine, the high-pressure shaft characterized by a high-speed shaft rating (HSR) from 1.5 to 6.2, wherein the high-pressure shaft is further characterized by an inlet area high-speed shaft rating (HSP_A IN ) from 1,038 in 2 to 5,017 in 2 , 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-pressure shaft, L CORE is a length of the engine core, D CORE is a diameter of the engine core, and k is a constant with a value of 10 6 inch-RPM, and
HSP_A IN is given by:
(
L
CORE
D
CORE
)
2
*
A
IN
R
HUB
,
IN
R
TIP
,
IN
*
R
TIP
,
EX
R
TIP
,
IN
,
where R HUB,IN /R TIP,IN is an inlet radius ratio of the high-pressure compressor, R TIP,EX /R TIP,IN is a high-pressure compressor tip radius ratio, and A IN is an area at an inlet of the high-pressure compressor.
2 . The turbomachine engine of claim 1 , wherein an exhaust gas temperature of the turbomachine engine at redline speeds of the high-pressure shaft is between 1,063° C. and 1,282° C.
3 . The turbomachine engine of claim 1 , wherein the high-pressure compressor includes eight stages, nine stages, ten stages, or eleven stages.
4 . The turbomachine engine of claim 1 , wherein the high-pressure turbine includes one stage or two stages.
5 . 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.
6 . The turbomachine engine of claim 1 , wherein HSP_A IN is a function of a high-speed shaft operating parameter (HSP X1 ), and HSP X1 is given by:
HSP
X
1
=
A
ex
*
1
0
0
0
FN
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, and FN T/O is a sea-level static thrust of the turbomachine engine at takeoff flight conditions corresponding to a maximum thrust rating for the turbomachine engine.
7 . The turbomachine engine of claim 6 , wherein HSP_A IN is less than
MAX
(
4
2
0
0
(
HSP
X
1
)
1.5
,
2
8
5
0
-
5
0
0
*
(
HSP
X
1
)
)
.
8 . The turbomachine engine of claim 6 , wherein HSP X1 is from 0.4 to 2.79.
9 . The turbomachine engine of claim 6 , wherein A EX is from 11 in 2 to 95 in 2 .
10 . The turbomachine engine of claim 6 , wherein FN T/O is from 12,674 lbf to 107,480 lbf.
11 . The turbomachine engine of claim 1 , wherein N2 R/L is from 10,580 RPM to 35,788 RPM.
12 . The turbomachine engine of claim 1 , wherein L CORE /D CORE is from 2.1 to 4.3.
13 . The turbomachine engine claim 1 , wherein A IN is from 85 in 2 to 703 in 2 .
14 . The turbomachine engine of claim 1 , wherein R HUB,IN /R TIP,IN is from 0.4 to 0.6.
15 . The turbomachine engine of claim 1 , wherein R TIP,EX /R TIP,IN is from 0.75 to 1.00.
16 . The turbomachine engine of claim 1 , wherein R TIP,EX is from 4.73 in. to 15.83 in.
17 . The turbomachine engine of claim 1 , wherein R TIP,IN is from 5.68 in. to 16.32 in.
18 . The turbomachine engine of claim 1 , wherein the high-pressure shaft is characterized by a second high-pressure shaft rating (HSR LP ) in a range from 1.1 to 1.6 and given by:
HSR
LP
=
1
0
-
6
*
N
1
r
l
*
D
CORE
*
(
L
CORE
D
CORE
)
2
,
where
N
1
r
l
is the redline speed of the low-pressure shaft.
19 . 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 including one stage or two stages, and a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine;
a power turbine in flow communication with the high-pressure turbine;
a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) from one hundred fifty (ft/sec) 1/2 to three hundred thirty (ft/sec) 1/2 , wherein low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec), and 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; and
a high-pressure shaft coupled to the high-pressure compressor and the high-pressure turbine, the high-pressure shaft characterized by a high-speed shaft rating (HSR) from 1.5 to 6.2, wherein the high-pressure shaft is further characterized by an inlet area high-speed shaft rating (HSP_A IN ) from 1,038 in 2 to 5,017 in 2 , 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-pressure shaft, L CORE is a length of the engine core, D CORE is a diameter of the engine core, and k is a constant with a value of 10 6 inch-RPM, and
HSP_A IN is given by:
(
L
CORE
D
CORE
)
2
*
A
IN
R
HUB
,
IN
R
TIP
,
IN
*
R
TIP
,
EX
R
TIP
,
IN
,
where R HUB,IN /R TIP,IN is an inlet radius ratio of the high-pressure compressor, R TIP,EX /R TIP,IN is a high-pressure compressor tip radius ratio, and A IN is an area at an inlet of the high-pressure compressor.
20 . The turbomachine engine of claim 19 , wherein HSP_A IN is a function of a high-speed shaft operating parameter (HSP X1 ), and HSP X1 is given by:
HSP
X
1
=
A
ex
*
1000
FN
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, and FN T/O is a sea-level static thrust of the turbomachine engine at takeoff flight conditions corresponding to a maximum thrust rating for the turbomachine engine, and
wherein HSP_A IN is less than
MAX
(
4
2
0
0
(
HSP
X
1
)
1.5
,
2
8
5
0
-
5
0
0
*
(
HSP
X
1
)
)
.