Midshaft rating for turbomachine engines
A turbomachine engine including a high-pressure compressor, a high-pressure turbine, a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine, and a power turbine in flow communication with the high-pressure turbine. At least one of the high-pressure compressor, the high-pressure turbine, and the power turbine comprises a ceramic matrix composite (CMC) material. The turbomachine engine includes a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between two hundred (ft/sec) 1/2 and three hundred (ft/sec) 1/2 . The low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). 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.
1. A turbomachine engine comprising:
a high-pressure compressor;
a high-pressure turbine;
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, wherein at least one of the high-pressure compressor, the high-pressure turbine, and the power turbine comprises a ceramic matrix composite (CMC) material; and
a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between two hundred (ft/sec) 1/2 and three hundred (ft/sec) 1/2 ,
wherein the low-pressure 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-pressure shaft.
2. The turbomachine engine of claim 1 , further comprising an engine core comprising the high-pressure turbine, the high-pressure compressor, and the combustion chamber, wherein the engine core has a core length (L CORE ) given by:
L
CORE
=
[
m
(
20
+
m
)
*
n
(
10
+
n
)
]
(
1
100
)
*
D
CORE
+
CIS
,
where m is a number of stages of the high-pressure compressor, n is a number of stages of the high-pressure turbine, and CIS is a constant.
3. The turbomachine engine of claim 1 , further comprising a high-pressure shaft coupled between the high-pressure turbine and the high-pressure compressor and an engine core comprising the high-pressure turbine, the high-pressure compressor, and the combustion chamber, wherein the high-pressure shaft is characterized by a high-pressure shaft rating (HSR LP ) given by:
HSR
LP
=
10
-
6
*
N
1
r
/
l
*
D
CORE
*
(
L
CORE
D
CORE
)
2
,
where N1 r/l is a redline speed of the low-pressure shaft, D CORE is a diameter of an exit stage of the high-pressure compressor, and L CORE is a core length of the engine core.
4. The turbomachine engine of claim 1 , further including an electric machine coupled to the low-pressure shaft.
5. The turbomachine engine of claim 1 , wherein the high-pressure turbine comprises an airfoil configured with a forward surface facing towards a hot gas stream and a rearward surface facing away from the hot gas stream, wherein the forward surface and the rearward surface each comprise the CMC material, and wherein the CMC material in the forward surface comprises a CVI type CMC material and the CMC material in the rearward surface comprises a MI type CMC material.
6. The turbomachine engine of claim 1 , wherein the high-pressure turbine comprises a CVI type CMC material and the power turbine comprises a MI type CMC material.
7. The turbomachine engine of claim 1 , wherein the CMC material includes a plurality of reinforcing fibers.
8. The turbomachine engine of claim 1 , wherein the power turbine comprises the CMC material.
9. The turbomachine engine of claim 8 , wherein the power turbine comprises at least one nozzle and at least one airfoil, wherein the at least one nozzle, the at least one airfoil, or both the at least one nozzle and the at least one airfoil comprise the CMC material.
10. The turbomachine engine of claim 8 , wherein the power turbine has three stages, four stages, five stages, or six stages, and wherein at least one stage of the three stages, the four stages, the five stages, or the six stages comprises the CMC material.
11. The turbomachine engine of claim 8 , wherein the power turbine has four stages and at least one stage of the four stages comprises the CMC material.
12. The turbomachine engine of claim 8 , wherein the CMC material is a first CMC material, and wherein the high-pressure turbine comprises the first CMC material or a second CMC material.
13. The turbomachine engine of claim 12 , wherein the high-pressure compressor comprises the first CMC material or the second CMC material or a third CMC material.
14. The turbomachine engine of claim 1 , wherein the high-pressure turbine comprises the CMC material.
15. The turbomachine engine of claim 14 , wherein the high-pressure turbine comprises at least one nozzle and at least one airfoil, wherein the at least one nozzle, the at least one airfoil, or both the at least one nozzle and the at least one airfoil comprise the CMC material.
16. The turbomachine engine of claim 14 , wherein the high-pressure turbine has one stage or two stages, and wherein the one stage or at least one stage of the two stages comprises the CMC material.
17. The turbomachine engine of claim 1 , wherein the high-pressure compressor comprises the CMC material.
18. The turbomachine engine of claim 17 , wherein the high-pressure compressor has eight stages, nine stages, ten stages, or eleven stages, and wherein at least one stage of the eight stages, nine stages, ten stages, or eleven stages comprises the CMC material.
19. The turbomachine engine of claim 17 , wherein the high-pressure compressor has nine stages and at least one stage of the nine stages comprises the CMC material.
20. The turbomachine engine of claim 17 , wherein the CMC material is a first CMC material, and wherein the high-pressure turbine comprises the first CMC material or a second CMC material.
21. The turbomachine engine of claim 1 , wherein the CMC material includes a ceramic matrix material comprising a non-oxide silicon-based material, an oxide ceramic material, or mixtures thereof.
22. The turbomachine engine of claim 21 , wherein the ceramic matrix material is SiC and the CMC material is reinforced with a plurality of SiC or C fibers.
23. The turbomachine engine of claim 21 , wherein the ceramic matrix material includes the non-oxide silicon-based material.
24. The turbomachine engine of claim 23 , wherein the non-oxide silicon-based material is selected from the group consisting of silicon carbide, silicon nitride, and mixtures thereof.
25. The turbomachine engine of claim 21 , wherein the ceramic matrix material includes the oxide ceramic material.
26. The turbomachine engine of claim 25 , wherein the oxide ceramic material is selected from the group consisting of silicon oxycarbides, silicon oxynitrides, aluminum oxide (Al 2 O 3 ), silicon dioxide (SiO 2 ), aluminosilicates, and mixtures thereof.
27. The turbomachine engine of claim 25 , wherein the oxide ceramic material includes oxides of element X, wherein X is selected from the group consisting of silicon (Si), aluminum (Al), zirconium (Zr), yttrium (Y), and combinations thereof.