Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D17/00—Regulating or controlling by varying flow
  • F01D17/02—Arrangement of sensing elements
  • F01D17/06—Arrangement of sensing elements responsive to speed
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
  • G05D13/02—Details
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D17/00—Regulating or controlling by varying flow
  • F01D17/02—Arrangement of sensing elements
  • F01D17/08—Arrangement of sensing elements responsive to condition of working-fluid, e.g. pressure
  • F01D17/085—Arrangement of sensing elements responsive to condition of working-fluid, e.g. pressure to temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K13/00—General layout or general methods of operation of complete plants
  • F01K13/02—Controlling, e.g. stopping or starting
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K3/00—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein
  • F01K3/02—Use of accumulators and specific engine types; Control thereof
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C9/00—Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03B—MACHINES OR ENGINES FOR LIQUIDS
  • F03B15/00—Controlling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2260/00—Function
  • F05D2260/80—Diagnostics
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2260/00—Function
  • F05D2260/81—Modelling or simulation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2270/00—Control
  • F05D2270/01—Purpose of the control system
  • F05D2270/02—Purpose of the control system to control rotational speed (n)
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2270/00—Control
  • F05D2270/01—Purpose of the control system
  • F05D2270/05—Purpose of the control system to affect the output of the engine
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2270/00—Control
  • F05D2270/30—Control parameters, e.g. input parameters
  • F05D2270/301—Pressure

Definitions

• the present invention relates generally to a method performed by a controller for controlling rotational speed of a turbine and to the controller and a turbine control system for performing said method, and more particularly to a method for optimization of power output in a turbine control system.
• a turbine wheel design is typically optimal for its chosen design point.
• the design point is characterized by several parameters, most notably pressures and temperatures of a fluid and a desired power output.
• pressures and temperatures of a fluid and a desired power output.
• the design is often considering so-called “off-design” operating points that are meant to help the designer to understand the range of operating conditions that may occur.
• the operating point of a turbine is defined by the rotational speed and the fluid velocity in the turbine. Those two parameters are dependant on the pressure difference over the turbine, thus the operating point can be tracked by collecting data pressure and temperature in the inlet and outlet of the turbine.
• a turbine is further designed to have its best efficiency at a certain design point. That design point is selected based upon the most common temperatures and flows of the gas flowing through the turbine. Flowever, if the flows and temperature vary, the turbine will need to operate “off-design” i.e. at a point where it does not have its highest efficiency.
• the controller then manipulates the speed of a working fluid pump, the pitch of turbine variable inlet guide vanes when present, and combinations thereof, in response to the determined superheated temperature to maintain the superheated temperature of the ORC working fluid in front of the radial inflow turbine close to a predefined set point.
• the superheated temperature can thus be maintained in the absence of sensors other than pressure and temperature sensors.
• An object of the present invention is to provide a method and a controller for controlling rotational speed of a turbine in a turbine system to improve the power output without losing efficiency.
• Another object is to provide a turbine control system for controlling rotational speed of a turbine to improve the power output without losing efficiency.
• a third object is to provide a computer program comprising non-transitory computer readable code means to be run in a control node for controlling the rotational speed of a turbine in a turbine system to improve the power output without losing efficiency.
• a fourth object is to improve the durability of a turbine thus to extend the lifespan of the turbine. Furthermore, the invention provides a solution suitable in anything that has a turbine installed, which means, it is suitable in many fields.
• a method for controlling rotational speed of a turbine in a turbine system.
• the turbine system comprises the turbine, a pressure sensor, a filter and a drive unit, the method comprises collecting sensor data from the pressure sensor and the drive unit, comparing the collected sensor data with reference values to determine that the collected sensor data is valid, calculating the current operating point of the turbine system based on the collected sensor data and system parameters of the turbine system, determining a current optimal rotational speed of the turbine based on the current operating point of the turbine system, checking the validity of the current optimal rotational speed by using the filter to sort out rotational speed values having predefined properties and controlling the drive unit to drive the turbine at the determined current optimal rotational speed.
• the step of checking the validity of the current optimal rotational speed further comprises the step of applying limits, dead bands and rate of change limitations to the current optimal rotational speed.
• the method further comprises continuously or at a specified rate repeating the steps of the method.
• the current optimal rotational speed is determined based on an empirically validated model.
• the sensor data is transmitted from the turbine system to the controller through a first interface.
• a controller for controlling the rotational speed of a turbine in a turbine system.
• the turbine system comprises the turbine, a pressure sensor, a filter and a drive unit and the controller comprises processing circuitry and a non-transitory computer-readable medium, configured to store instructions, which when executed by the processing circuitry, cause the controller to collect sensor data by means of the pressure sensor and the drive unit, compare the collected sensor data with reference values to determine that the collected sensor data is valid, calculate the current operating point of the turbine system based on the collected sensor data and system properties of the turbine system, determine a current optimal rotational speed of the turbine based on the current operating point of the turbine system, check the validity of the current optimal rotational speed by using the filter to sort out rotational speed values having predefined properties and control the drive unit to drive the turbine at the determined current optimal rotational speed.
• a turbine control system for controlling the rotational speed of a turbine, comprising a turbine system, a communication system and a controller as defined above, wherein the turbine system comprises a turbine, a drive unit, a pressure sensor, a filter and a second interface, wherein the turbine system communicates with a first interface of the controller through the communication system and the second interface.
• a computer program comprising non- transitory computer readable code means being adapted, if executed on processing circuitry, to implement the method described above.
• the turbine will output the most optimal power depending on the operating conditions and the turbine design itself, i.e. the method aims to minimize the loss caused by different operating conditions by means of adjusting the rotational speed of the turbine wheel.
• the speed of the turbine wheel may be instantaneously adjusted to its most efficient value.
• the design point is at, or close to, the maximum allowed operating rotational speed.
• This invention will therefore also improve durability by operating at lower, on average, speed and thus extend service life and cost. All else being equal, the service life is directly proportional to the rotational speed of the turbine in cases of roller bearings. For example, a 20% reduction in rotational speed would incur a 20% longer service life which could lead to a substantial saving in service cost for a fleet of machines globally. Furthermore, a reduction in rotational speed is almost always beneficial to lubrication systems for roller bearings. In some cases, the improvement is larger than from the rotational speed factor alone in terms of service life.
• FIG. 1 is a flow chart showing an example of a method for controlling rotational speed of a turbine in a turbine system
• Fig. 2 describes an example of a turbine control system.
• Fig. 3 describes an exemplary structure of a controller for controlling rotational speed of a turbine in a turbine system.
• Fig. 4 describes an example of comparison of turbine model with experimentally fitted data for a few variations of the input state to the turbine.
• Fig. 5 describes an example of empirical fit to net power output.
• Fig. 6 describes functional relationship of current optimal rotational speed limited to dependence on pressure ratio between inlet and outlet of the turbine.
• Fig. 1 shows an example of a method for controlling rotational speed of a turbine in a turbine system, which is shown in Fig. 2.
• the method is performed by a controller 101 for controlling rotational speed of a turbine 122 in a turbine system 105.
• the method comprises collecting S100 sensor data from sensors in the turbine system 105.
• the sensors may be pressure sensors 130 and drive sensors in the drive unit 126.
• the drive train can provide information including, but not limited to, turbine rotational speed, active and reactive power, voltage, current and temperatures that may be used to further optimize the turbine rotational speed.
• the sensors may further be temperature sensors 128.
• the temperature sensors 128 and pressure sensors 130 may be arranged at the inlet side of the turbine, the drive sensors are arranged in the drive unit 126.
• the collected sensor data may be real-time data or processed data, such as calculated or estimated data.
• the method further comprises comparing S102 the sensor data with reference values to determine whether the collected sensor data is valid or not.
• the reference values may be previously collected sensor data and/or theoretically determined values.
• the reference values typically define a range of values within which the collected sensor data must fall in order to be determined as valid. If it is determined that the collected sensor data is not valid, step S100 is repeated and new sensor data is collected and then compared with reference values in step S102 to determine the validity.
• the method further comprises calculating S104 the current operating point of the turbine system 105 and determining S106 a current optimal rotational speed of the turbine 122 based on the current operating point of the turbine system 105.
• the current optimal rotational speed is determined from an empirically validated model of the turbine 122.
• the empirically validated model will be closer defined and described in conjunction with Fig. 4 to Fig. 6.
• the underlying functional relationship of the model used may be arbitrarily complicated but must depend on different system variables that are accurately measured by sensors used by the present method.
• Such sensor may for example be temperature sensors 128, pressure sensors 130, different sensors in the drive unit 126 or other sensors capturing different properties of the turbine system 105.
• Fig. 4 describes an example of comparison of turbine model with experimentally fitted data for a few different variations of the input state to the turbine 122, in this case variations of the input temperature to the turbine.
• the experimental data is created by using a CFD (Computational Fluid Dynamics) model to simulate optimal speed for a turbine at different operation conditions. In this example the simulation varies the input temperature to the turbine. The dotted line is the simulated optimal speed taken into account the different simulated operating temperatures.
• Fig. 5 an empirical fit to net power output is shown.
• the CFD simulated optimal speed curve in Fig. 6 will be used as a basis when performing the empirical test.
• the empirical test is performed on the turbine system 105 which also may be seen as a module, i.e.
• module M38 is tested for different rotational speeds at a constant pressure ratio Pin/Pout.
• the net power output is measured at intervals of 1000 rpm.
• a curve is plotted with straight lines between the measured values and any known curve fitting technique may be used to a obtain an optimal curve fit.
• the highest net power output was found at 16000 rpm and when using the obtained optimal curve fit the highest net power output is at 15790 rpm.
• Fig. 6 describes functional relationship of current optimal rotational speed limited to dependence on pressure ratio between inlet and outlet of the turbine.
• Fig.6 many empirical tests are summarized for different pressure ratios and also for different modules, i.e. M38 and M6.
• M38 and M6 There is also shown a fitted curve, one point of which (encircled) is the optimal point found during the empirical test described in conjunction with Fig. 5.
• the dotted line in Fig. 6 represents the current optimal rotational speed and is based on the obtained empirically validated model.
• Fig. 6 is described in combination with Fig. 5 in details as follows: The optimal rotational speed is calculated from a detailed simulation model of the turbine, this is carried out using CFD.
• there are other components and processes outside the turbine that can affect the optimal speed, e.g.
• the approach here is to use the CFD model as guide to determine the optimal rotational speed, but validate the model of the optimal rotational speed by using a real machine. This allows it to verify that the model is good enough to optimize the speed for the module as a whole.
• the model used for a new generation of machines will be slightly different even if the turbine model itself is identical, because the fitted data would be different.
• step S108 the validity of the current optimal rotational speed is checked in step S108. This is done by applying a filter 132 to the determined current optimal rotational speed, which filter 132 sorts out rotational speed values have predefined properties, i.e. values that are outside a specified range. Such a range may be defined by applying limits, dead bands and rate of change limitations to the determined current optimal rotational speed values. If the optimal current rotational speed is determined to be valid in step S108 the method continues with step S112, in which the drive unit 126 is controlled to drive the turbine 122 at the determined current optimal rotational speed.
• the above steps (S100-S112) mat be performed continuously or at a specified rate.
• the refreshment rate may var between 0,5 to 30 seconds and is preferably set to once per second, which will give a responsive system.
• the above described functional relationship may be tracked by the controller 101 , in which a computer program 132, stored there on implements the method.
• the controller 101 may also have stored thereon the turbine model used to determine the current optimal rotational speed
• the turbine control system 100 comprises a controller 101 , a turbine system 105 and a communication system 103.
• the controller 101 is arranged to perform the method according to steps S100-S112, which were described above in conjunction with Fig. 1.
• the controller 101 may be arranged as an independent unit.
• the controller 101 may also be part of an independent system outside the turbine system 105, for example be provided in a cloud computing service and with a communication channel to the turbine system 105 to exchange data with the turbine system 105.
• the controller 101 may be integrated in the turbine system 105 or be arranged as part of the turbine system 105.
• the controller 101 comprises at least one processing circuitry 118 and at least one non-transitory computer readable medium 120, the non-transitory computer readable medium 120 containing instructions executable by the processing circuitry 118.
• the instructions executable by said processing circuitry 118 may be arranged as a computer program 132 stored in the non-transitory computer readable medium 120.
• the processing circuitry 118 and the non-transitory computer readable medium 120 may be arranged in an arrangement.
• the arrangement may alternatively be a microprocessor and adequate software and storage therefore, a Programmable Logic Device, PLD, or other electronic component(s)/processing circuit(s) configured to perform the actions, or methods, mentioned above.
• the non-transitory computer readable medium 120 may be a memory.
• the memory may be realized as for example a RAM (Random-access memory), ROM (Read-Only Memory) or an EEPROM (Electrical Erasable Programmable ROM).
• the computer program 132 may be carried by a separate computer-readable medium, such as a CD, DVD or flash memory, from which the program could be downloaded into the at least one memory.
• the computer program 132 may comprise computer readable code means, which when run in the controller 101 causes the controller to perform the steps described in the method as illustrated in Fig. 1.
• the computer program 132 may comprise computer readable code means, which when run in the turbine system 105 or in a separate unit causes the turbine system 105 or the separate unit to perform the steps described in the method as illustrated in Fig. 1.
• the controller 101 may comprise an interface 116 for communicating with the turbine system 105 via the communication system 103.
• the interface 116 can be software, a mix of software and hardware in the form of hardwired connections, different field bus solutions and communication protocols.
• the controller 101 further comprises at least one functional unit, the functional units are shown in Fig.3.
• the controller 101 may comprise a collecting unit 102 for collecting sensor data from the temperature sensor 128, the pressure sensor 130 and the drive unit 126, a first checking unit 104 for comparing the collected sensor data with reference values to determine that the collected sensor data is valid, an evaluating unit 106 for calculating the current operating point of the turbine system 105 based on the collected sensor data and system parameters of the turbine system 105, a first determining unit 108 for determining a current optimal rotational speed of the turbine based on the current operating point of the turbine system 105, a second checking unit 110 for checking the validity of the current optimal rotational speed an adjusting unit 114 for controlling the drive unit 126 to drive the turbine at the determined current optimal rotational speed.
• the controller 101 further comprises a second determining unit 112 for determining the current optimal rotational speed by applying limits, dead bands and rate of change limitations to the current optimal rotational speed.
• the turbine system 105 comprises a turbine 122, a drive unit 126, a pressure sensor 130 and a filter 132. At least one sensor may further be arranged in the drive unit 126. In some embodiments, a temperature sensor 128 may also be arranged in the turbine system 105. As described above, the temperature sensor 128 and the pressure sensor 130 may be arranged at the inlet side of the turbine. The number of sensors may be adapted depending on which empirically validated model of the turbine that the method used.
• the turbine system 105 may comprise a second interface 124 arranged for communicating with the controller 101 through the communication system 103.
• Data exchanged through the second interface 124 from the turbine system 105 to the controller 101 may comprise of sensor data and system status.
• Data exchange through the first interface 116 from the controller 101 to the turbine system 105 may comprise commands and setpoints.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Control Of Turbines (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

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• 2020
  • 2020-07-03 SE SE2050842A patent/SE544489C2/en unknown
• 2021
  • 2021-06-23 EP EP21736768.9A patent/EP4176162A1/de not_active Withdrawn
  • 2021-06-23 WO PCT/SE2021/050620 patent/WO2022005367A1/en not_active Ceased

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