# US 12,215,633 B2 · Midshaft rating for turbomachine engines > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,215,633 B2 - Document ID: US12215633B2 - Status: Granted - Kind: B2 - Application number: 18/486,523 - Filed: 2023-10-13 - Published: 2024-04-11 - Granted: 2025-02-04 - Earliest claimed: 2021-05-24 - Assignees: General Electric Company - Applicants: General Electric Company - Inventors: Narayanan Payyoor; Weize Kang; Thomas Lee Becker; Richard Schmidt - Web page: https://patentgrep.com/patent/US12215633B2 ## CPC - F02C 7/36: Power transmission arrangements between the different shafts of the gas turbine plant, or between the gas-turbine plant and the power user ({F02C3/107 - F02C3/13 and} F02C7/32 take precedence; couplings for transmitting rotation F16D; gearing in general F16H) - F01D 25/16: Arrangement of bearings; Supporting or mounting bearings in casings (bearings per se F16C) - F02C 7/06: Arrangements of bearings (bearings F16C); Lubricating ({of turbo machines F01D25/18; of machines or} engines in general F01M) - F05D 2240/54: Radial bearings - F05D 2240/60: Shafts - F05D 2240/61: Hollow - F05D 2250/711: convex - F05D 2260/96: Preventing, counteracting or reducing vibration or noise - F05D 2300/603: Composites; e.g. fibre-reinforced - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A turbomachine engine includes a core engine having one or more compressor sections, one or more turbine sections that includes a power turbine, and a combustion chamber in flow communication with the compressor sections and turbine sections. The turbomachine engine also includes a 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. In one aspect, the shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). In another aspect, the shaft has a length L, an outer diameter D, and a ratio of L/D between twelve and thirty-seven. ## Claims ### Claim 1 A method of operating a turbomachine engine including a power turbine and a shaft that is coupled to the power turbine, the method comprising: driving the shaft, wherein the shaft is characterized by a midshaft rating (MSR) between two hundred (ft/sec)1/2 and three hundred (ft/sec)1/2; and operating the turbomachine engine up to a redline speed without passing through a critical speed associated with a first-order bending mode of the shaft. ### Claim 2 (depends on 1) The method of claim 1, wherein the MSR is between two hundred (ft/sec)1/2 and two hundred forty-five (ft/sec)1/2. ### Claim 3 (depends on 1) The method of claim 1, wherein the MSR is between two hundred twelve (ft/sec)1/2 and two hundred sixty (ft/sec)1/2. ### Claim 4 (depends on 1) The method of claim 1, wherein the MSR is between two hundred forty-seven (ft/sec)1/2 and two hundred eighty-seven (ft/sec)1/2. ### Claim 5 (depends on 1) The method of claim 1, wherein the redline speed is between fifty ft/sec and two hundred fifty ft/sec. ### Claim 6 (depends on 1) The method of claim 1, wherein the redline speed is between sixty ft/sec and ninety ft/sec. ### Claim 7 (depends on 1) The method of claim 1, wherein the redline speed is between seventy-five ft/sec and one hundred seventy-five ft/sec. ### Claim 8 (depends on 1) The method of claim 1, wherein the redline speed is between one hundred fifty ft/sec and two hundred fifty ft/sec. ### Claim 9 (depends on 1) The method of claim 1, wherein the shaft is supported between a first bearing and a second bearing, and the shaft has a length L defined between the first bearing and the second bearing, an outer diameter D, and a ratio of L/D between twelve and thirty-seven. ### Claim 10 (depends on 9) The method of claim 9, wherein the ratio of L/D is between sixteen and thirty. ### Claim 11 (depends on 9) The method of claim 9, wherein the ratio of L/D is between twenty-six and thirty-seven. ### Claim 12 (depends on 1) The method of claim 1, wherein the shaft is a low-speed shaft, and the turbomachine engine further includes a high-pressure compressor, a high-pressure turbine, and a high-speed shaft that couples the high-pressure compressor and the high-pressure turbine, and the method further comprises driving the high-speed shaft with the high-pressure turbine to rotate the high-pressure compressor. ### Claim 13 (depends on 12) The method of claim 12, wherein the turbomachine engine further includes a combustion chamber, and the method further comprises combusting fuel and air in the combustion chamber to generate combustion gases, and driving the high-pressure turbine and the power turbine with the combustion gases. ### Claim 14 (depends on 1) The method of claim 1, wherein the turbomachine engine further includes a fan assembly, and the shaft is coupled to the fan assembly, and the method further comprises driving, by the power turbine, the fan assembly via the shaft. ### Claim 15 (depends on 14) The method of claim 14, wherein the turbomachine engine further includes a power gearbox that couples the fan assembly to the shaft, and the method further comprises decreasing, with the power gearbox, a rotational speed of the fan assembly relative to the shaft. ### Claim 16 A method of operating a turbomachine engine including a fan assembly, a high-pressure compressor, a high-pressure turbine, a high-speed shaft that couples the high-pressure compressor and the high-pressure turbine, and a combustion chamber that is in flow communication with the high-pressure compressor and the high-pressure turbine, a power turbine that is in flow communication with the high-pressure turbine, and a low-speed shaft that is coupled to the power turbine and the fan assembly, the method comprising: combusting fuel and air in the combustion chamber to generate combustion gases; driving the high-pressure turbine with the combustion gases; driving the high-pressure compressor with the high-pressure turbine via the high-speed driving the power turbine with the combustion gases; shaft; driving the fan assembly with the power turbine via the low-speed shaft; driving the low-speed shaft, wherein the low-speed shaft is characterized by a midshaft rating (MSR) between two hundred (ft/sec)1/2 and three hundred (ft/sec)1/2; and operating the turbomachine engine up to a redline speed without passing through a critical speed associated with a first-order bending mode of the low-speed shaft. ### Claim 17 (depends on 16) The method of claim 16, wherein the MSR is between two hundred (ft/sec)1/2 and two hundred forty-five (ft/sec)1/2. ### Claim 18 (depends on 16) The method of claim 16, wherein the redline speed is between fifty ft/sec and two hundred fifty feet per second ft/sec. ### Claim 19 (depends on 16) The method of claim 16, wherein the low-speed shaft is supported between a first bearing and a second bearing, and the low-speed shaft has a length L defined between the first bearing and the second bearing, an outer diameter D, and a ratio of L/D between twelve and thirty-seven. ### Claim 20 (depends on 16) The method of claim 16, wherein the turbomachine engine further includes a power gearbox that couples the fan assembly to the low-speed shaft, and the method further comprises decreasing, with the power gearbox, a rotational speed of the fan assembly relative to the low-speed shaft.