Modular design of turboexpander components

Abstract

The generator includes a process gas inlet downstream of the flow control valve for admitting process gas into the electric machine, a rotor shaft including nodal locations defining nodal locations of a first bending mode of the rotor shaft, a turbine wheel coupled to the rotor shaft at the nodal locations, the turbine wheel configured to receive the process gas and rotate in response to expansion of the process gas entering the inlet of the turbine wheel and exiting the outlet of the turbine wheel, the rotor shaft configured to rotate with the turbine wheel, and a stationary stator, wherein the generator generates alternating current upon rotation of the rotor within the stator, and the turbine wheel is selected from a plurality of turbine wheels based on an operating condition of the generator.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 17 / 930,153, filed September 7, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a modular design of turboexpander components. [Background technology]

[0003] The efficient and effective movement of gas from production areas to consumption areas utilizes an extensive and sophisticated transportation system. Gas transported via pipelines can be pressurized and can travel long distances through the pipeline at high pressure. For example, natural gas transported through pipelines travels at high pressure within the pipeline. Natural gas is one of the primary energy sources for many of our daily needs and activities. Natural gas is an attractive fossil fuel due to its abundance and relative cleanliness. As another example, hydrogen can also be transported at high pressure using pipelines. Hydrogen is a rapidly expanding global energy storage market. Hydrogen is used in many manufacturing processes, from oil refining to food processing. Hydrogen is also used as a fuel source for gas turbines and in a wide range of fuel cells to generate electricity in the industrial and consumer transportation sectors. Other gases can also be transported through pipelines at high pressure, including propane, oxygen, and carbon dioxide. Summary of the Invention

[0004] An aspect of an embodiment is directed to an apparatus including a generator comprising: a rotor shaft, the rotor shaft having nodal locations defining nodal locations of a first bending mode of the rotor shaft; a turbine wheel coupled to the rotor shaft at the nodal locations, the turbine wheel configured to receive process gas and rotate in response to expansion of the process gas flowing into an inlet and out of an outlet of the turbine wheel, the rotor shaft configured to rotate with the turbine wheel; and a stationary stator, the generator producing alternating current upon rotation of the rotor within the stator.

[0005] In some embodiments, the generator comprises a first magnetic bearing at a first location and a second magnetic bearing at a second location, and the turbine wheel is coupled to the rotor shaft between the first magnetic bearing and the second bearing.

[0006] In some embodiments, a node of a first bending mode of the rotor shaft is proximate to the first location.

[0007] In some embodiments, the rotor shaft comprises a turbine wheel mounting interface that mates with a first turbine wheel having a first gas inlet size and a second turbine wheel having a second gas inlet size, the first gas inlet size being different from the second gas inlet size.

[0008] In some embodiments, the generator further includes a housing assembly including a main housing supporting the stator, an inlet funnel removably attached to a first flange of the main housing, and an inlet cone disposed within the inlet funnel and removably attached to the main housing.

[0009] Some embodiments include an exit funnel removably attached to the second flange of the main housing, and an exit cone disposed within the exit funnel and removably attached to the main housing.

[0010] In some embodiments, the turbine wheel is a first turbine wheel, the node of the first bending mode is a first node at a first nodal location, the rotor shaft comprises a second node of the first bending mode at a second nodal location on the rotor shaft, and the generator comprises a second turbine wheel coupled to the rotor shaft at the second nodal location.

[0011] In some embodiments, the turbine wheel includes a shroud.

[0012] In some embodiments, the generator includes a plurality of electrical outputs, each of the plurality of electrical outputs configured to receive a blanking plate.

[0013] In some embodiments, the rotor shaft includes a plurality of permanent magnets.

[0014] Aspects of an embodiment are directed to a method that includes identifying an operating condition of a generator, selecting a turbine wheel from a plurality of different turbine wheels based on the operating condition, coupling the selected turbine wheel to a rotor shaft of the generator, and providing the generator.

[0015] In some embodiments, the operating conditions include one or both of the process gas flow rate or the power output rating for the generator.

[0016] In some embodiments, the method also includes identifying a first bending mode node of the rotor shaft, and coupling the selected turbine wheel to the rotor shaft of the generator includes coupling the selected turbine wheel to the rotor shaft at a location juxtaposed with the node of the first bending mode.

[0017] In some embodiments, the method also includes selecting an inlet cone and an inlet funnel based on an operating condition, and coupling the selected inlet cone and inlet funnel to a main housing of the generator.

[0018] In some embodiments, the method also includes selecting an exit cone and an exit funnel based on an operating condition, and coupling the selected exit cone and exit funnel to a main housing of the generator.

[0019] Aspects of the embodiment include a system including a flow control valve for controlling the flow of a process gas and a generator. The flow control valve can control the mass flow rate of the process gas or other gas to an inlet of a turboexpander. The flow control valve can cooperate with a pressure control valve to control the pressure of the process gas input to the inlet of the turboexpander. The system also includes a process gas inlet downstream of the flow control valve for receiving the process gas into the generator, a rotor shaft having a nodal location, a nodal location defining a nodal location of a first bending mode of the rotor shaft, a turbine wheel coupled to the rotor shaft at the nodal location, the turbine wheel configured to receive the process gas and rotate in response to expansion of the process gas entering the inlet of the turbine wheel and exiting the outlet of the turbine wheel, the rotor shaft configured to rotate with the turbine wheel, and a stationary stator, wherein the generator generates alternating current upon rotation of the rotor within the stator.

[0020] In some embodiments, the generator comprises a first magnetic bearing at a first location and a second magnetic bearing at a second location, and the turbine wheel is coupled to the rotor shaft between the first magnetic bearing and the second bearing.

[0021] In some embodiments, a node of a first bending mode of the rotor shaft is proximate to the first location.

[0022] In some embodiments, the rotor shaft comprises a turbine wheel mounting interface that mates with a first turbine wheel having a first gas inlet size and a second turbine wheel having a second gas inlet size, the first gas inlet size being different from the second gas inlet size.

[0023] In some embodiments, the generator further includes a housing assembly including a main housing supporting the stator and an inlet funnel removably attached to the first flange of the main housing. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram of a power generation system coupled to a power grid, according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of an exemplary turboexpander system including a modular rotor assembly according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram of a graphical representation of a first exemplary rotor bending mode in accordance with an embodiment of the present disclosure. [Figure 4A] 4A-4D are schematic diagrams illustrating inventive wheel locations along a rotor shaft juxtaposed with one or both of the first bending mode node locations, according to an embodiment of the present disclosure. [Figure 4B] FIG. 4B is a schematic diagram illustrating an inventive wheel location along a rotor shaft juxtaposed with one or both of the first bending mode node locations, according to an embodiment of the present disclosure. [Figure 4C] FIG. 4C is a schematic diagram illustrating an inventive wheel location along a rotor shaft juxtaposed with one or both of the first bending mode node locations, according to an embodiment of the present disclosure. [Figure 4D] FIG. 4D is a schematic diagram illustrating an inventive wheel location along a rotor shaft juxtaposed with one or both of the first bending mode node locations, according to an embodiment of the present disclosure. [Figure 5A] FIG. 5A is a schematic diagram illustrating a turbine wheel design according to an embodiment of the present disclosure. [Figure 5B] FIG. 5B is a schematic diagram illustrating a turbine wheel design according to an embodiment of the present disclosure. [Figure 6A] FIG. 6A is a schematic diagram of an exemplary turbine wheel design according to an embodiment of the present disclosure. [Figure 6B] FIG. 6B is a schematic diagram of an exemplary turbine wheel design according to an embodiment of the present disclosure. [Figure 7A] FIG. 7A is a schematic diagram illustrating turboexpander housing components according to an embodiment of the present disclosure. [Figure 7B] FIG. 7B is a schematic diagram illustrating turboexpander housing components according to an embodiment of the present disclosure. [Figure 7C] FIG. 7C is a schematic diagram illustrating turboexpander housing components according to an embodiment of the present disclosure. [Figure 7D] FIG. 7D is a schematic diagram illustrating turboexpander housing components according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a schematic diagram of an exemplary electrical output on the main housing 702 including a blanking plate, according to an embodiment of the present disclosure. [Figure 9] FIG. 9 is a process flow diagram for providing a turboexpander for use according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] The same reference symbols in the various drawings indicate the same elements. The drawings are not to scale.

[0026] Natural gas, hydrogen, and other process gases are pressurized to facilitate efficient transportation in pipelines that are sometimes several miles long. Pipelines transport gas, for example, from production sites (e.g., wells) to processing facilities, and from processing facilities to local distribution networks, such as regional, city, or district networks or on-site industrial plant networks. For safe delivery and use through local distribution networks, process gases are reduced in pressure (often using pressure regulators) to lower levels. The pressure is then stepped down at pressure drop (PLD) stations for delivery to industrial, commercial, and residential end users. PLD stations use regulating valves to achieve the required pressure drop, but waste a significant amount of energy in the process. Additional regulating valves can be used elsewhere for pressure control, such as in pipelines between production and processing facilities, within subprocesses at processing facilities, and within end-user processes and piping. Turboexpander generators can be installed in parallel with regulating valves to recover wasted energy from the pressure reduction and generate electricity. The electricity can be directed to the power grid or elsewhere. Along the same lines, turboexpander generators can be installed at gas storage facilities upstream of one or more storage tanks, allowing high-pressure gas dispensed from tank trucks to be returned to the storage tanks through the turboexpander generator. Turboexpander generators are also relevant in other applications, such as hydrogen liquefaction processes, where cooled and pressurized gaseous hydrogen is expanded to a liquid state. The expansion can be performed through the turboexpander generator to recover waste energy from the expansion and generate electricity. As mentioned above, the electricity can be directed to the power grid or elsewhere, such as to power compressors or other components of the liquefaction process. In each application, by recovering lost energy from natural gas and hydrogen pressure reduction applications, turboexpanders can generate electricity while reducing CO2 emissions, increasing overall plant efficiency, offsetting electricity costs, and generating additional revenue.

[0027] The power grid that the turboexpander may supply (and draw power from) may be a national or regional power grid, a local power grid for a city or district, or a smaller grid, local grid, or microgrid, such as an on-site grid that supplies power to a building, campus, industrial manufacturing or processing plant, or neighborhood.

[0028] FIG. 1 is a schematic diagram of a power generation system 100 coupled to a power grid 140 according to an embodiment of the present disclosure. The power generation system 100 can be added at a PLD station to capture energy from gas expansion from the PLD process or in any of the other applications described above. The power generation system 100 includes a turboexpander 102 in parallel with a pressure control valve 130. The turboexpander 102 is axially arranged so that the turboexpander 102 can be mounted in series with a pipe. The turboexpander 102 acts as a generator by generating electrical energy from the rotational kinetic energy derived from the expansion of gas through a turbine wheel 104. For example, the rotation of the turbine wheel 104 can be used to rotate a rotor 108 within a stator 110, which then generates electrical energy.

[0029] FIG. 1 is a schematic diagram of a power generation system 100 coupled to a power grid 140 according to an embodiment of the present disclosure. The power generation system 100 can be added at a PLD station to capture energy from gas expansion from the PLD process. The power generation system 100 includes a turboexpander 102 in parallel with a pressure control valve 130. The turboexpander 102 is axially arranged so that the turboexpander 102 can be mounted in series with a pipe. The turboexpander 102 acts as a generator by generating electrical energy from the rotational kinetic energy derived from the expansion of gas through a turbine wheel 104. For example, the rotation of the turbine wheel 104 can be used to rotate a rotor 108 within a stator 110, which then generates electrical energy.

[0030] The turboexpander 102 may include a high-performance, high-speed permanent magnet generator. In one embodiment, the turboexpander 102 includes a radial-flow expansion turbine wheel 104. The turboexpander 102 may also include low-loss active magnetic bearings (AMBs) 116a,b. The rotor assembly may include a permanent magnet section of the turbine wheel 104 mounted directly to the rotor hub. The rotor 108 may be levitated by a magnetic bearing system that creates a frictionless (or near-frictionless) interface between moving and stationary components. The AMBs 116a,b facilitate lossless (or near-lossless) rotation of the rotor 108.

[0031] The turboexpander 102 is shown with a process gas flow through the system, which cools the generator section and eliminates the need for auxiliary cooling equipment. In some embodiments, a non-flow-through overhung system can also be implemented. The power electronics 118 for the turboexpander, in some implementations, combines a variable speed drive (VSD) 206 and a magnetic bearing controller (MBC) 168 into a single cabinet. The VSD enables a consistent and clean delivery of generated power from the turboexpander 102 to the power grid 140. The VSD 206 adjusts the frequency and amplitude of the generated current to match the local grid. After expansion, the gas exits the turboexpander 102 along the same axial path for downstream processing.

[0032] The turboexpander 102 is shown as having a flow-through configuration. The flow-through configuration allows process gas to flow from the inlet side of the turboexpander 102 to the outlet side of the turboexpander 102. The gas flows to a radial gas inlet 154 to the turbine wheel 104 and to an axial gas outlet 156 from the turbine wheel 104. The gas then flows through a generator and out the outlet 156, where it recombines with the gas pipeline 170. Generally, the high-pressure process gas 120 is directed into the turboexpander 102 through a flow control system 126. The flow control system 126 includes flow or mass control valves and an emergency shut-off valve. The flow control system 126 can be electrically controlled from the power electronics 118 by control line 164. In an embodiment, the turboexpander housing 112 is hermetically sealed. As mentioned above, the turboexpander can be non-flow-through and overhung without departing from the scope of this disclosure. High-pressure process gas 120 is expanded by flowing through the turbine wheel 104, resulting in a pressure drop of the process gas. Low-pressure process gas 128 exits the turboexpander. The expansion of the high-pressure process gas 120 through the turbine wheel 104 rotates the turbine wheel 104, which in turn rotates the rotor 108. Rotation of the rotor 108 within the stator 110 generates electrical energy. The turboexpander 102 achieves the desired pressure drop and captures energy from the pressure drop to generate electricity. A pressure control valve 130, such as a conventional pressure regulator, can be installed in parallel with the turboexpander 102. The pressure control valve 130 can be used to control the pressure of the high-pressure process gas 120 flowing through the turboexpander. Any excess high-pressure process gas not directed to the turboexpander can be directed through the pressure control valve 130.

[0033] In some embodiments, a heater 122 can heat the high-pressure process gas 120 before allowing the gas to enter the turboexpander 102. For example, if the expansion of the gas through the turbine wheel 104 reduces the temperature of the process gas to a point where moisture in the gas would freeze at the turbine wheel or other downstream locations in the pipeline, the compressed process gas 120 can be heated by the heater 122. The heated high-pressure process gas 124 can then be directed to the turboexpander 102. Heating the process gas can prevent moisture from freezing as the gas expands and its temperature drops.

[0034] The turboexpander 102 includes a turbine wheel 104. The turbine wheel 104 is shown as a radial-inflow turbine wheel, although other configurations, such as an axial-flow turbine wheel, are within the scope of this disclosure. In this example, heated high-pressure process gas 124 is received from an inlet conduit 150 in the housing 112 and enters a radially oriented inlet 154 of the turbine wheel 104. In certain embodiments, the fluid flows through the inlet conduit 150 and is diverted by a flow diverter to the radial inlet 154, which directs the flow toward the radial inlet of the turbine wheel 104. After expansion, the low-pressure process gas exits the turbine wheel 104 through an axially oriented outlet 156 to an outlet conduit 152 in the housing 112.

[0035] The turbine wheel 104 may be attached directly to the rotor 108 or an intermediate common shaft, for example, by fasteners, a rigid drive shaft, welding, or other methods. For example, the turbine wheel 104 may be received on the end of the rotor 108 and held to the rotor 108 by a shaft. The shaft threads into the rotor 108 at one end and captures the turbine wheel 104 at the other end between the end of the rotor 108 and a nut threaded onto the shaft. The turbine wheel 104 and rotor 108 may be coupled without a gearbox and rotate at the same speed. In other examples, the turbine wheel 104 may be indirectly coupled to the rotor 108, for example, by a gear train, a clutch mechanism, or other methods.

[0036] The turbine wheel 104 extends outward from a hub and includes a plurality of turbine wheel blades 106 that react with the expanding process gases to rotate the turbine wheel 104. FIG. 1 illustrates a non-penetrating turbine wheel, in which the turbine blades 106 each have an exposed, generally radially oriented blade tip that extends between a radial inlet 154 and an axial outlet 156. As described in more detail below, the blade tips substantially seal against a shroud 114 inside a housing 112. In certain examples, the turbine wheel 104 is a shrouded turbine wheel.

[0037] In a configuration with an unshrouded turbine wheel 104, the housing 112 includes an inwardly extending shroud 114 that closely abuts the turbine wheel blades 106 and, at most, does not contact them during operation. The close proximity of the turbine wheel blades 106 and the shroud 114 substantially seals against the passage of process gas therebetween as the process gas flows through the turbine wheel 104. While some amount of process gas may leak or pass between the turbine wheel blades 106 and the shroud 114, this leakage is insignificant in the operation of the turbine wheel 104. In certain instances, the leakage can be balanced with other similar unshrouded turbine / shroud surface interfaces using conventional tolerances between the turbine wheel blades 106 and the shroud 114. The amount of leakage considered acceptable may be predetermined. The operating parameters of the turbine generator can be optimized to reduce leakage. In an embodiment, the housing 112 is hermetically sealed to prevent process gas from escaping from the radial inlet 154 of the turbine wheel 104.

[0038] The shroud 114 can be a specified distance away from the turbine wheel blades 106 and is maintained at that distance from the turbine wheel blades 106 during operation of the turboexpander 102 by using a magnetic positioning device that includes active magnetic bearings and position sensors.

[0039] The bearings 116a and 116b are positioned to rotatably support the rotor 108 and the turbine wheel 104 relative to the stator 110 and the shroud 114. The turbine wheel 104 is supported in a non-cantilevered manner by the bearings 116a and 116b. In an embodiment, the turbine wheel 104 may be supported in a cantilevered manner, and the bearings 116a and 116b may be positioned on an outlet side of the turbine wheel 104. In certain examples, one or more of the bearings 116a or 116b may include a ball bearing, a needle bearing, a magnetic bearing, a foil bearing, a journal bearing, or the like.

[0040] Bearings 116a and 116b may be a combination radial and thrust bearing that radially and axially supports rotor 108. Other configurations may also be utilized. Bearings 116a and 116b do not have to be the same type of bearing.

[0041] In embodiments in which the bearings 116a and 116b are magnetic bearings, a magnetic bearing controller (MBC) 168 is used to control the magnetic bearings 116a and 116b. Position sensors 117a, 117b may be used to detect the position or change in position of the turbine wheel 104 and / or rotor 108 relative to the housing 112 or other reference point (e.g., a predetermined value). The position sensors 117a, 117b may detect axial and / or radial displacement. The magnetic bearings 116a and / or 116b may respond to information from the position sensors 117a, 117b and adjust the detected displacement, if necessary. The MBC 168 may receive information from the position sensors 117a, 117b, process the information, and provide control signals to the magnetic bearings 116a, 116b. The MBC 168 may communicate with various components of the turboexpander 102 via a communication channel 162.

[0042] The use of magnetic bearings 116a, 116b and position sensors 117a, 117b to maintain and / or adjust the position of the turbine wheel blades 106 allows the turboexpander 102 to operate at high efficiency as the turbine wheel blades 106 remain in close proximity to the shroud 114. The use of active magnetic bearings 116a, b in the turboexpander 102 eliminates physical contact between rotating and stationary components and eliminates the lubrication system. In some embodiments, brush seals can be used to prevent gas leakage. The magnetic bearings 116a, b and position sensors 117a, b allow the rotor to remain in close proximity to the brush seals.

[0043] The turboexpander 102 may include one or more backup bearings. For example, during startup and shutdown, or in the event of a power outage affecting the operation of the magnetic bearings 116a and 116b, the bearings may be used to rotatably support the turbine wheel 104 during such periods. The backup bearings may include ball bearings, needle bearings, journal bearings, etc. As previously described, the turboexpander 102 is configured to generate electricity in response to the rotation of the rotor 108. In certain examples, the rotor 108 may include one or more permanent magnets. The stator 110 includes multiple conductive coils. Electric current is generated by the rotation of the magnets within the coils of the stator 110. The rotor 108 and the stator 110 may be configured as a synchronous permanent magnet multi-phase alternating current (AC) generator. The electrical output 160 may be, for example, a three-phase output. In certain examples, the stator 110 may include multiple coils (e.g., three or six coils for a three-phase AC output). As the rotor 108 rotates, a voltage is induced in the stator coils. At any instant in time, the magnitude of the voltage induced in the coil is proportional to the rate at which the magnetic field surrounded by the coil changes with time (i.e., the rate at which the magnetic field passes through the two sides of the coil). When the rotor 108 is coupled to rotate at the same speed as the turbine wheel 104, the turboexpander 102 is configured to generate electricity at that speed. Such a turboexpander 102 is referred to as a "high-speed" turbogenerator. For example, in an embodiment, the turboexpander 102 can generate up to 280 kW at a continuous speed of 30,000 rpm. In an embodiment, the turboexpander can generate approximately 350 kW at a higher rotational speed (e.g., approximately 35,000 rpm).

[0044] In some embodiments, the design of the turbine wheel 104, rotor 108, and / or stator 110 may be based on desired parameters of the output gas from the turboexpander 102. For example, the design of the rotor and stator may be based on the desired temperature of the gas 128.

[0045] The turboexpander 102 may be coupled to power electronics 118. The power electronics 118 may include a variable speed drive (VSD) 206 (or variable frequency drive) and a magnetic bearing controller (MBC) 168 (described above).

[0046] The electrical output 160 of the turboexpander 102 is connected to a VSD 206, which can be programmed to specific power requirements. The VSD 206 can include an insulated gate bipolar transistor (IGBT) rectifier that converts the variable frequency high voltage output from the turboexpander 102 to direct current (DC). The rectifier 210 can be a three-phase rectifier for three-phase AC input current. An inverter then converts the DC from the rectified AC to supply to the power grid 140. A power conditioner can convert the DC to 380 VAC to 480 VAC at 50 to 60 Hz and supply it to the power grid. The specific output of the VSD 206 depends on the power grid and application. Other conversion values ​​are within the scope of this disclosure. The VSD 206 samples the grid voltage and frequency and then matches its output to the power grid 140 by changing the inverter's output voltage and frequency to match the sampled power grid voltage and frequency.

[0047] The turboexpander 102 is also connected to an MBC 168 within the power electronics 118. The MBC 168 constantly monitors position, current, temperature, and other parameters to ensure that the turboexpander 102 and active magnetic bearings 116a and 116b are operating as needed. For example, the MBC 168 is coupled to position sensors 117a, 117b to monitor the radial and axial positions of the turbine wheel 104 and rotor 108. The MBC 168 can control the magnetic bearings 116a, 116b to selectively vary the stiffness and damping characteristics of the magnetic bearings 116a, 116b as a function of spin speed. The MBC 168 can also control synchronous cancellation, including auto-balancing control, adaptive vibration control, adaptive vibration cancellation, and unbalanced force cancellation control.

[0048] The pressure drop system converts shaft power from the process flow. The turboexpander can support islanding operation. The turboexpander can continue to provide power to a location if the electrical grid supplying the location is interrupted. This disclosure describes components that can facilitate load matching between shaft power generated by the process gas flow at the pressure drop station and load demand. In this way, the turboexpander can support microgrid functionality for islanding operation.

[0049] The turboexpander 102 described above includes exemplary implementation-specific features. Some features may be modified, added, removed, or redesigned without departing from the scope of this disclosure. For example, other types of bearings, such as ball bearings, fluid film bearings, etc., may be used instead of or in addition to the AMB. Different rotor and stator designs may be used, such as brushless DC, induction, etc. Other types of stator cooling architectures may be used, such as non-flow-through and overhanging architectures.

[0050] 2 is a schematic diagram of an exemplary turboexpander system 200 including a modular rotor assembly according to an embodiment of the present disclosure. The turboexpander system 200 includes a turboexpander 102 and power electronics 118. The turboexpander 102 receives heated, high-pressure process gas 124, which rotates a turbine wheel 104. The rotation of the turbine wheel 104 rotates a rotor 108, which supports multiple permanent magnets. The rotation of the permanent magnets on the rotor 108 induces current through coils or windings on a stator 110.

[0051] Some turbomachines have overhung impellers, where the impeller is positioned outside the bearing span. Typically, two nodes of the rotor's first bending mode are located between the bearing spans. By moving the impeller within the bearing span and onto one of these nodes, the impeller experiences little or no displacement, resulting in limited impact on the rotor dynamics of the rotor assembly. Once the impeller is positioned on the node, it can be interchangeable with other impeller designs to suit specific applications and turbomachine bearing adjustments (including magnetic bearing adjustments). The present invention is also applicable to tuned damping of rolling element bearings. In either case, this allows a single machine and bearing design to be adapted to various applications.

[0052] The generator system acts as a brake for the rotor 108. This braking torque converts shaft power generated by the process gas flow into electrical power that can be applied, for example, to the power grid. In the event of a grid fault, inverter failure, or other fault condition, the braking torque is lost, and the rotor 108 may spin up toward an undesirable overspeed. To prevent overspeed, electrical power can be diverted to a brake resistor assembly 202, which can temporarily absorb electricity until the process gas flow is reduced or eliminated (e.g., by the flow control system 126) or until the fault condition is resolved. The flow control system 126 can include one or a combination of flow control valves, mass control valves, or emergency shut-off valves. The flow control system 126 can be controlled by the power electronics 118 or other electrical, mechanical, or electromagnetic signals. For example, a fault condition can signal the flow control system 126 to close or partially close, thereby eliminating or limiting the gas supply to the turboexpander 102. Restricting or eliminating gas flow to the turboexpander slows the rotation of the turbine wheel, which in turn slows the rotor. In the example shown in Figures 1 and 2, control lines 164 from power electronics 118 can be used to open or close flow control system 126.

[0053] The fault condition may include a grid fault, a VSD fault, an inverter fault, or any other fault condition that removes or reduces the braking torque of the rotor 108.

[0054] The brake resistor assembly 202 is electrically connected to the electrical output 160 (e.g., the output of a generator) of the turboexpander 102. The brake resistor assembly 202 may have a tuned impedance to allow efficient transfer of power from the turboexpander 102 to the brake resistor assembly 202.

[0055] In embodiments, the contactor 204 can connect the output current of the turboexpander 102 to the brake resistor assembly 202 when there is a fault condition in the VSD 206 or the power grid 140. The contactor 204 is an electrically controlled switch for switching in a power circuit. The contactor 204 can accommodate three-phase current output from the generator to pass DC current to the brake resistor assembly 202. In some embodiments, the contactor 204 is directly connected to the turboexpander 102 (three-phase) electrical output 160. In some embodiments, the brake resistor assembly 202 and / or the contactor 204 are not part of the power electronics but are connected to the turboexpander 102 electrical output 160 outside of the power electronics 118.

[0056] The VSD 206 provides an energization signal 220 to the coil of the contactor 204, causing the contactor 204 to connect the turboexpander's electrical output 160 to the brake resistor assembly 202. Depending on the implementation choice, the contactor 204 may be a normally closed (NC) contactor or a normally open (NO) contactor. For example, in an exemplary implementation using an NO contactor, during normal operating conditions, the turboexpander's 102's electrical output 160 is connected to the VSD 206, supplying three-phase AC current to the VSD 206. Under a fault condition, the VSD may actuate the contactor, connecting it to the turboexpander's 102's electrical output 160. In some implementations, the energization signal 220 to the contactor may be provided by another source that may respond to a fault condition (e.g., another component of the power electronics 118 or another component external to the power electronics 118). In this implementation, the contactors can operate independently of the VSD 206 if a failure in the VSD 206 is the cause of the fault condition.

[0057] If an NC contactor is used, the VSD 206 (or other source) provides an energization signal 220 to the contactor 204 to keep the contactor switch open during normal operating conditions. A fault condition may result in the removal of the energization signal 220 to the contactor, causing the contactor switch to close and complete the circuit between the electrical output 160 of the turboexpander 102 and the brake resistor assembly 202.

[0058] In some embodiments, the brake resistor 202 may be disconnected from the electrical output 160 of the turboexpander 102 when operating conditions return to normal.

[0059] The electrical output of a turboexpander can depend on the rotational speed of the rotor, which is based on the process gas flow rate and the configuration of the turbine wheel. A single turboexpander can be used to accommodate different power ratings or process gas flows by using a modular design of the turbine wheel as well as modular designs for various structural components of the turboexpander. This disclosure describes several design considerations for achieving modularity in turboexpanders to accommodate different applications. This disclosure describes rotor designs for turbine wheel interchangeability.

[0060] Placing the turbine wheel on the high-speed rotor at the node of the rotor shaft defined by the rotor shaft's first bending mode reduces the turbine wheel's effect on the rotor dynamics of the rotor assembly because the turbine wheel experiences little or no displacement during operation. Reducing or eliminating turbine wheel displacement during operation allows for turbine wheel interchangeability with minimal adjustments to bearing tuning, including magnetic bearing tuning and tuned damping of rolling element bearings. In either case, this allows a single machine and bearing design to be adapted to a variety of applications. The node of the rotor shaft's first bending mode can be theoretically predicted using finite element analysis or numerical analysis techniques.

[0061] The modularity of the turbine wheel design and the design of other turboexpander components allows for different applications with different process or mass flows to be used on the same machine. Different applications can be supported by changing one or more modular components. Standardization of the turboexpander housing and other component designs helps improve the reliability of the entire machine. In addition, standardization also reduces manufacturing and operational costs, since the same machine can be used in different applications by changing a few parts, as opposed to using an entire new machine. Modularity and standardization also support the use of similar control files across machines.

[0062] First, the rotor shaft can be designed to allow for modular turbine wheel configurations. That is, the rotor shaft can be designed so that different turbine wheel configurations can be fixed to the rotor shaft without affecting the rotor shaft's frequency response or the control of the magnetic bearings that support the rotor's frictionless rotation within the stator. A rotating rotor can exhibit bending modes. Modes of vibration are characterized by modal frequencies and mode shapes. Each mode is numbered according to the number of half-waves of vibration. For example, if a vibrating rotor clamped at both ends displays a half-sine mode shape (one peak on the vibrating rotor), the rotor is vibrating in mode 1 (or, in this case, the first bending mode). One-dimensional systems in a given mode have nodes, or locations along the rotor where the vibration (or sinusoidal) displacement is always zero. The nodes correspond to the points on the mode shape where the mode shape is zero.

[0063] This disclosure describes designing a turboexpander and various components so that the turbine wheel can be collocated with a node of the rotor. FIG. 3 is a schematic diagram of an exemplary rotor bending mode graphical representation 300 according to an embodiment of the disclosure. In FIG. 3, a first bending mode sine wave 304 is graphically mapped to a rotor shaft 302. A node 306 is identified as the point along the first bending mode sine wave 304 where the first bending mode sine wave 304 intersects the center of the rotor shaft 302 (0 inches of shaft radius). The first bending mode shape is adjusted so that the center of mass of the wheel is located on node 306, with magnetic bearing support locations 308a and 308b located on the outside of the wheel. A bearing target or section of the rotor can be adjusted to properly locate the wheel on node 306.

[0064] As seen in FIG. 3 , nodes exist at two locations along rotor shaft 302 (e.g., at first node location 306 and second node location 310). Turbine wheels or other types of wheels can be located on either side of rotor shaft 302, with both magnetic bearings located on the outside of both wheels. FIGS. 4A-4D are schematic diagrams illustrating inventive wheel locations along the rotor shaft juxtaposed with one or both of the node locations, according to an embodiment of the present disclosure. The placement of the wheels on the nodes can be achieved by directing the process fluid flow toward or away from the center of the machine. FIGS. 4A-4D show turboexpanders 400, 420, 430, and 440. Each of turboexpanders 400, 420, 430, and 440 includes a rotor shaft 302 supported by magnetic bearings 308a and 308b. Rotor shaft 302 has two nodes 404a and 404b. For example, FIG. 4A shows a first configuration of turboexpander 400. In turboexpander 400, process gas flows toward the center of rotor shaft 302. Wheel 406 is located at node 404a. FIG. 4B shows a second configuration of turboexpander 420. In turboexpander 420, process gas exits the center of rotor shaft 302. Wheel 408 is located at node 404a. FIG. 4C shows a third configuration of turboexpander 430. In turboexpander 430, two wheels may be used. Process gas flows toward the center of rotor shaft 302. First wheel 406 may be located at node 404a, and second wheel 408 may be located at node 404b. FIG. 4D shows a fourth configuration of turboexpander 440. In turboexpander 440, two wheels may be used. Process gas exits the center of rotor shaft 302. A first wheel 406 may be located at node 404b and a second wheel 408 may be located at node 404a.

[0065] Locating the wheels at the nodes of the rotor shaft 302 allows the turboexpander to use an integrated aero design, as opposed to an overhung machine, where the aero sections are bolted to the end of the machine. Magnetic bearings support the integrated aero design. Locating the turbine wheels at the nodes of the rotor shaft facilitates the integrated aero design without compromising the magnetic bearings. The turbine wheel location does not affect balance or vibration, allowing the magnetic bearings to support the rotation of the rotor within the stator, while also accommodating variations in turbine wheel selection. Simply put, a heavier or lighter turbine wheel does not affect the magnetic bearing support of the rotor shaft as it rotates. Any first mode vibration or oscillation of the rotating rotor shaft is not sensitive to mass or inertia at the nodes.

[0066] For magnetic bearing control, the frequency response of the first bending mode can affect the control of the magnetic bearing. Placing the turbine wheel near the node mitigates the effect of turbine wheel changes on frequency response and magnetic bearing control. Furthermore, the turbine wheel is not a magnetic component. Therefore, placing the turbine wheel near the rotor shaft node and magnetic bearing does not affect the functionality of the magnetic bearing.

[0067] 5A-B are schematic diagrams illustrating turbine wheel designs according to embodiments of the present disclosure. FIG. 5A is a schematic diagram of a first turbine wheel design 500 for a 125 kW power-rated turboexpander according to an embodiment of the present disclosure. FIG. 5B is a schematic diagram of a second turbine wheel design 550 for a 280 kW power-rated turboexpander according to an embodiment of the present disclosure. Exemplary dimensions of the first turbine wheel design 500 and the second turbine wheel design 550 are shown to highlight both the differences and similarities in certain dimensions between the two. For example, both the first turbine wheel design 500 and the second turbine wheel design 550 include the same dimensions for R1, R2, and R3. The common dimensions of R1, R2, and R3 allow both turbine wheels to be secured to a common rotor shaft and fit within the housing of the turboexpander. The turbine wheel designs 500 and 550 are designed with common interfaces to enable interchangeability between the wheels. The common interfaces include a shaft interface, a common tie bolt, and a common brush seal interface. This commonality between turbine wheel designs provides consistent moment stiffness to the invariant portion of the rotor so that the rotor shaft nodes can be juxtaposed with any turbine wheel design.

[0068] Differences between turbine wheel designs 500 and 550 include dimensions to accommodate process flow gases to generate higher rotational speeds to generate more power. For example, first turbine wheel design 500 is designed for a 125 kW output. First turbine wheel design 500 includes a process gas inlet opening T1, an expansion chamber thickness T2, and a process gas outlet T3. Second turbine wheel design 550 includes a process gas inlet opening T1', an expansion chamber thickness T2', and a process gas outlet T3', where T1'>T1, T2'>T2, and T3'>T3. Both first turbine wheel design 500 and second turbine wheel design 550 can be fixed to the same rotor shaft 302, but can generate different rotational speeds from the same process gas flow, thereby generating different power ratings. In some embodiments, second turbine wheel design 550 can accommodate a higher process gas flow rate than first turbine wheel design 500, yet still fit onto a common rotor shaft 302.

[0069] 6A-B are schematic diagrams of exemplary turbine wheel designs according to embodiments of the present disclosure. A first turbine wheel design 600 is shown in FIG. 6A. The first turbine wheel design 600 can be similar to the first turbine wheel design 500 described above. A second turbine wheel design 650 is shown in FIG. 6B. The second turbine wheel design 650 can be similar to the first turbine wheel design 500 described above. The first turbine wheel design 600 and the second turbine wheel design 650 are "shrouded" turbine wheels. The first turbine wheel design 600 includes a shroud 602 that protects the turbine wheel blades from wear as the rotor rotates. The second turbine wheel design 650 includes a shroud 652 that protects the turbine wheel blades from wear as the rotor rotates. In some embodiments, turbine wheels can be constructed without a shroud. The turbine wheel blades can be designed to ablate during operation. The turbine wheel may also be configured to receive modular shrouds that can be assembled onto the turbine wheel prior to installation.

[0070] Both the first turbine wheel design 600 and the second turbine wheel design 650 may be fabricated using additive manufacturing techniques such as three-dimensional (3D) printing.

[0071] 7A-D are schematic diagrams illustrating turboexpander housing components according to embodiments of the present disclosure. FIG. 7A is a schematic diagram illustrating a fully assembled turboexpander 102 according to embodiments of the present disclosure. The turboexpander 102 can include a housing assembly 700. The housing assembly 700 can include a main housing 702, an inlet funnel 722, and an outlet funnel 742. The main housing 702 is shown in FIG. 7B. FIG. 7B is a schematic diagram illustrating the main housing 702 of the housing assembly 700 according to embodiments of the present disclosure. The main housing 702 can house the rotor shaft 108, magnetic bearings 708a and 708b that support the rotor shaft 108, and the stator components 110, in addition to other components used to support rotation of the rotor within the stator and facilitate the flow of electrical current to the electrical output 160 of the turboexpander 102. The main housing 702 can include design features that direct the flow of process gas in a specific manner, forcing the gas into the turbine wheel in a controlled manner toward the center of the main housing 702. For example, the main housing 702 can be designed to include the shroud 114, as described above. In some embodiments, the gas flow can be directed outward, away from the center of the turboexpander 102, without departing from the scope of this disclosure. The design of the main housing 702 can also facilitate the flow of process gas without the use of seals, as described above.

[0072] The main housing 702 may also include attachment or connection points for the inlet cone 704 and the outlet cone 706. The inlet cone 704 and the outlet cone 706 may be selected based on process gas flow conditions without having to modify the casting of the main housing 702. The inlet cone 704 and the outlet cone 706 may be modular. Each design of the inlet cone 704 and the outlet cone 706 may include a common interface for mating, connecting, or otherwise securing the inlet cone 704 and the outlet cone 706 to the main housing 702. The design of the inlet cone 704 and the outlet cone 706 interface may include standard sizes and attachment points for attaching the inlet cone 704 and the outlet cone 706 to the main housing 702. Inlet cones of different radii of curvature, aspect ratios, and / or other design considerations may be selected based on process gas flow conditions and secured to the main housing 702 using a common interface. Similarly, exit cones of different radii of curvature, aspect ratios, and / or other design considerations may be selected and secured to the main housing 702 based on process gas flow conditions.

[0073] The housing assembly 700 also includes an inlet funnel 722, shown in Figure 7C, and an outlet funnel 742, shown in Figure 7D. The inlet funnel 722 is attached to the main housing 702 at an interface flange 712. The outlet funnel 742 is attached to the main housing 702 at an interface flange 714. The modularity of the inlet funnel 722 and the outlet funnel 742 allows the funnels to be modified for different flow conditions and interface flange dimensions.

[0074] For example, FIG. 7C is a schematic diagram illustrating an inlet funnel 722 according to an embodiment of the present disclosure. The inlet funnel 722 has an inlet funnel flange 724 that can mate with the interface flange 712. A plurality of bolts (e.g., bolts 726a and 726b, among others) can be used to secure the inlet funnel 722 at the inlet funnel flange 724 to the inlet funnel interface flange 712 of the main housing 702. FIG. 7D is a schematic diagram illustrating an outlet funnel 742 according to an embodiment of the present disclosure. The outlet funnel 742 has an outlet funnel flange 744 that can mate with the interface flange 714. A plurality of bolts (e.g., bolts 746a and 746b, among others) can be used to secure the outlet funnel 742 at the outlet funnel flange 744 to the outlet funnel interface flange 714 of the main housing 702.

[0075] Returning briefly to FIG. 7B , the main housing 702 includes electrical outputs 160. The electrical outputs 160 utilize power connections to power electronics, brake resistors, loads, the power grid, or other elements. The power connections are made using one or more three-phase connectors. A blanking plate 710 is used for lower power levels where not all connector positions are populated. FIG. 8 is a schematic diagram 800 of an exemplary electrical output 160 on the main housing 702 including a blanking plate 710 in accordance with an embodiment of the present disclosure. The blanking plate 710 may be used when the turboexpander is operating for an application that does not require all power connections to be used. For example, in certain scenarios where lower power outputs are used, one or more blanking plates 710 may be used to electrically isolate unused electrical outputs of the turboexpander from connecting the electrical outputs to a load.

[0076] 9 is a process flow diagram 900 for providing a turboexpander for an application according to an embodiment of the present disclosure. First, the location of the nodes of a first bending mode of the rotor shaft is identified (902). The first bending mode of the shaft may have two nodes, one adjacent to each end of the rotor shaft, as shown in FIGS. 3 and 4A-4D. The node locations indicate where the turbine wheels are coupled to the rotor shaft.

[0077] Turboexpanders can be assembled to meet the requirements of the particular application in which they are used. For example, power output from a turboexpander is related to the rotational speed of the rotor, which depends in part on the velocity of the process gas flow to the turbine wheel, as well as the size and design considerations of the turbine wheel itself. During assembly of a turboexpander, a turbine wheel can be selected based on the turboexpander's application, e.g., the process gas flow conditions and desired power output expected from the turboexpander. Simply put, a turbine wheel can be selected from a plurality of turbine wheels based on the turboexpander's application (904). The selected turbine wheel can be coupled to the rotor shaft at a nodal location (906).

[0078] The inlet cone and inlet funnel of the turboexpander can also be selected from a number of options based on the turboexpander's application and operating site conditions (910). For example, the inlet cone and inlet funnel can be selected based on a desired pressure drop at a pressure drop station. Alternatively, the inlet cone and inlet funnel can be used to adjust the process gas flow rate to a desired level for a selected turbine wheel. The inlet cone and inlet funnel can be secured to the turboexpander's main housing (912).

[0079] Similarly, the turboexpander's exit cone and exit funnel may be similarly selected from a number of options based on the turboexpander's application and operating site conditions (914). The exit cone and exit funnel may be secured to the turboexpander's main housing (916).

[0080] The assembled turboexpander can be provided to a work site 918. The site of operation can be, for example, a pressure let-down station or a hydrogen liquefaction process station.

[0081] Accordingly, the specification and drawings should be regarded in an illustrative rather than a restrictive sense. Moreover, the foregoing use of embodiment and other exemplary language does not necessarily refer to the same embodiment or the same example, but may refer to different, separate, and potentially the same embodiment. In the foregoing specification, a detailed description has been given with reference to certain exemplary embodiments. However, it will be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the present disclosure as set forth in the claims.

Claims

1. A rotor shaft having node positions, wherein the node positions define the positions of the nodes of the first bending mode of the rotor shaft, A turbine wheel coupled to the rotor shaft at the node position corresponding to the first bending mode of the rotor shaft, A turbine wheel is configured to receive process gas, flow into the inlet of the turbine wheel, and rotate in response to the expansion of the process gas flowing out from the outlet of the turbine wheel, and the rotor shaft is configured to rotate together with the turbine wheel. A stationary stator, wherein a generator generates an alternating current when the rotor shaft within the stationary stator rotates, A generator including, and a device including.

2. The apparatus according to claim 1, wherein the generator is provided with a first magnetic bearing at a first position and a second magnetic bearing at a second position, and the turbine wheel is coupled to the rotor shaft between the first magnetic bearing and the second magnetic bearing.

3. The apparatus according to claim 2, wherein the node of the first bending mode of the rotor shaft is close to the first position.

4. The apparatus according to claim 1, wherein the rotor shaft includes a turbine wheel mounting interface that fits a first turbine wheel having a first gas inlet size and a second turbine wheel having a second gas inlet size, and the first gas inlet size is different from the second gas inlet size.

5. The aforementioned generator, The main housing supporting the stator, An inlet funnel detachably attached to the first flange of the main housing, and an inlet cone disposed within the inlet funnel and detachably attached to the main housing, The apparatus according to claim 1, further comprising a housing assembly having

6. An outlet funnel is removably attached to the second flange of the main housing, The system further comprises an outlet cone disposed within the outlet funnel and removably attached to the main housing, The apparatus according to claim 5.

7. The turbine wheel is a first turbine wheel, and the node of the first bending mode is a first node at the first node position. The rotor shaft has a second node of the first bending mode at a second node position on the rotor shaft, The generator comprises a second turbine wheel coupled to the rotor shaft at the second node position. The apparatus according to claim 1.

8. The apparatus according to claim 1, wherein the turbine wheel includes a shroud.

9. The apparatus according to claim 1, wherein the generator has a plurality of electrical outputs, and each of the plurality of electrical outputs is configured to receive a blanking plate.

10. The apparatus according to claim 1, wherein the rotor shaft comprises a plurality of permanent magnets.

11. Identifying a first bending mode of the rotor shaft, Identifying the node position of the first bending mode on the rotor shaft, To understand the operating status of the generator, Based on the aforementioned operating conditions, a turbine wheel is selected from a plurality of different turbine wheels, The selected turbine wheel is coupled to the node position of the rotor shaft of the generator, To provide the aforementioned generator, Includes, A method for coupling the selected turbine wheel to the rotor shaft of the generator, comprising coupling the selected turbine wheel to the rotor shaft at a position juxtaposed with the node of the first bending mode.

12. The method according to claim 11, wherein the operating conditions include one or both of the process gas flow rate or power output rating of the generator.

13. Selecting an inlet cone and an inlet funnel based on the operating conditions, The selected inlet cone and inlet funnel are coupled to the main housing of the generator, The method according to claim 11, further comprising:

14. The outlet cone and outlet funnel shape are selected according to the aforementioned operating conditions, To connect the selected outlet cone and outlet funnel to the main housing of the generator, The method according to claim 11, further comprising:

15. A flow control valve that controls the flow of process gas, It is a generator, A process gas inlet for receiving process gas into the generator, A rotor shaft having node positions, wherein the node positions define the positions of the nodes of the first bending mode of the rotor shaft, A turbine wheel coupled to the rotor shaft at the node position corresponding to a first bending mode of the rotor shaft, wherein the turbine wheel is configured to receive process gas, flow into the inlet of the turbine wheel, and rotate in response to the expansion of the process gas flowing out from the outlet of the turbine wheel, and the rotor shaft is configured to rotate together with the turbine wheel. A stationary stator, wherein the generator generates an alternating current when the rotor shaft within the stator rotates. A system equipped with a generator.

16. The system according to claim 15, wherein the generator comprises a first magnetic bearing in a first position and a second magnetic bearing in a second position, and the turbine wheel is coupled to the rotor shaft between the first magnetic bearing and the second magnetic bearing.

17. The system according to claim 16, wherein the node of the first bending mode of the rotor shaft is close to the first position.

18. The system according to claim 15, wherein the rotor shaft includes a turbine wheel mounting interface that fits a first turbine wheel having a first gas inlet size and a second turbine wheel having a second gas inlet size, the first gas inlet size being different from the second gas inlet size.

19. The aforementioned generator, The main housing supporting the stator, An inlet funnel is removably attached to the first flange of the main housing, The system according to claim 15, further comprising a housing assembly having

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