초록 ▼

A method for obtaining an estimate for a process quantity of a turbomachine comprises measuring (301) first process quantities and calculating (302) an estimate for a second process quantity, for example mass flow, on the basis of the measured first process quantities and a reference table of interr

A method for obtaining an estimate for a process quantity of a turbomachine comprises measuring (301) first process quantities and calculating (302) an estimate for a second process quantity, for example mass flow, on the basis of the measured first process quantities and a reference table of interrelations between process quantities prevailing in reference inlet conditions corresponding to a pre-defined inlet fluid temperature, a pre-defined inlet fluid pressure, and pre-defined fluid properties at the inlet. The reference table and the measured first process quantities represent such a set of data values that the estimate is obtainable on the basis of different sub-sets of the data values. Hence, the estimation task is over-posed in the sense that there is more data than necessary for obtaining the estimate. In the calculation of the estimate, more weight is given to such a part of the data which has a smaller error contribution.

대표청구항 ▼

1. A turbomachine (100) comprising: a chamber (101) having an inlet (102) and an outlet (103) for fluid to be moved,an impeller (104) placed in the chamber for moving the fluid,equipments (105-107) for measuring first process quantities related to the turbomachine, anda processor (108) for calculati

1. A turbomachine (100) comprising: a chamber (101) having an inlet (102) and an outlet (103) for fluid to be moved,an impeller (104) placed in the chamber for moving the fluid,equipments (105-107) for measuring first process quantities related to the turbomachine, anda processor (108) for calculating an estimate for a second process quantity related to the turbomachine on the basis of measured values of the first process quantities and a reference table of interrelations between process quantities prevailing in reference inlet conditions which correspond to a predefined inlet fluid temperature, a pre-defined inlet fluid pressure, and predefined fluid properties at the inlet, characterized in that the reference table and the measured values of the first process quantities represent such a set of data values that the estimate is obtainable on the basis of different sub-sets of the set of data values, and the processor is arranged to give, in the calculation of the estimate, more weight to a first sub-set of the set of data values which has a smaller error estimate than to a second sub-set of the set of data values which has a greater error estimate in order to increase the accuracy of the estimate, the error estimate related to each sub-set being proportional to a scalar product of a vector of squares of sensitivities of the estimate with respect to the data values of that sub-set and a vector of variances of the data values of that sub-set. 2. A turbomachine according to claim 1, wherein the processor is arranged to use, for giving to the first sub-set more weight than to the second sub-set, variances or other error indicators of both the data values represented by values of the reference table and the data values represented by the measured values of the first process quantities. 3. A turbomachine according to claim 1, wherein the processor is arranged to calculate the estimate with different values of the data values so as to obtain changes of the estimate corresponding to changes of the data values, a ratio of the change of the estimate to the change of each data value representing the sensitivity of the estimate with respect to that data value. 4. A turbomachine according to claim 1, wherein the turbomachine is a turbo compressor for moving gas, the pre-defined fluid properties at the inlet corresponding to a pre-defined value of a gas-constant. 5. A turbomachine according to claim 4, wherein the first process quantities are: torque directed to the impeller,rotational speed of the impeller,pressure rise of the gas,inlet pressure of the gas, andinlet temperature of the gas, and wherein the reference table contains tabulated values of isentropic efficiency and tabulated values of rotational speed in the reference inlet conditions as functions of mass flow and pressure ratio in the reference inlet conditions, and wherein the second process quantity is the mass flow in the actual operating conditions. 6. A turbomachine according to claim 4, wherein the first process quantities are: torque directed to the impeller,rotational speed of the impeller,pressure rise of the gas,inlet pressure of the gas, andinlet temperature of the gas, and wherein the reference table contains tabulated values of mass flow and tabulated values of rotational speed in the reference inlet conditions as functions of torque and pressure ratio in the reference inlet conditions, and wherein the second process quantity is the mass flow in the actual operating conditions. 7. A turbomachine according to claim 1, wherein the turbomachine is a pump for moving liquid, the pre-defined fluid properties at the inlet corresponding to a predefined a density of the liquid. 8. A turbomachine according to claim 1, wherein the processor is arranged to control the rotational speed of the impeller on the basis of the estimate of the second process quantity. 9. A turbomachine according to claim 1, wherein the processor is arranged to control at least one from the following list on the basis of the estimate of the second process quantity: one or more inlet guide vanes, one or more outlet guide vanes, one or more diffuser guide vanes. 10. A turbomachine according to claim 1, wherein the turbomachine comprises an electrical motor (112) for rotating the impeller and the impeller is directly connected to a shaft (113) of the electrical motor. 11. A turbomachine according to claim 10, wherein the turbomachine comprises a static frequency converter (110) for supplying electrical power to the electrical motor (112). 12. A turbomachine according to claim 1, wherein the processor is arranged to produce start and stop commands for one or more other turbomachines so as to keep the estimate on a desired range. 13. A method for obtaining an estimate for a process quantity related to a turbomachine that comprises a chamber having an inlet and an outlet for fluid to be moved and an impeller placed in the chamber for moving the fluid, the method comprising: measuring (301) first process quantities related to the turbomachine, andcalculating (302) an estimate for a second process quantity related to the turbomachine on the basis of measured values of the first process quantities and a reference table of interrelations between process quantities prevailing in reference inlet conditions which correspond to a pre-defined inlet fluid temperature, a pre-defined inlet fluid pressure, and pre-defined fluid properties at the inlet, characterized in that the reference table and the measured values of the first process quantities represent such a set of data values that the estimate is obtainable on the basis of different sub-sets of the set of data values, and, in the calculation of the estimate, more weight is given to a first sub-set of the set of data values which has a smaller error estimate than to a second sub-set of the set of data values which has a greater error estimate in order to increase the accuracy of the estimate, the error estimate related to each sub-set being proportional to a scalar product of a vector of squares of sensitivities of the estimate with respect to the data values of that sub-set and a vector of variances of the data values of that sub-set. 14. A method according to claim 13, wherein the first sub-set is given more weight than the second sub-set by using variances or other error indicators of both the data values represented by values of the reference table and the data values rep-resented by the measured values of the first process quantities. 15. A method according to claim 13, wherein the estimate is calculated with different values of the data values so as to obtain changes of the estimate corresponding to changes of the data values, a ratio of the change of the estimate to the change of each data value representing the sensitivity of the estimate with respect to that data value. 16. A method according to claim 13, wherein the turbomachine is a turbo compressor for moving gas, the pre-defined fluid properties at the inlet corresponding to a pre-defined value of a gas-constant. 17. A method according to claim 16, wherein the first process quantities are: torque directed to the impeller,rotational speed of the impeller,pressure rise of the gas,inlet pressure of the gas, andinlet temperature of the gas, and wherein the reference table contains tabulated values of isentropic efficiency and rotational speed in the reference inlet conditions as functions of mass flow and pressure ratio in the reference inlet conditions, and wherein the second process quantity is the mass flow in the actual operating conditions. 18. A method according to claim 16, wherein the first process quantities are: torque directed to the impeller,rotational speed of the impeller,pressure rise of the gas,inlet pressure of the gas, andinlet temperature of the gas, and wherein the reference table contains tabulated values of mass flow and rotational speed in the reference inlet conditions as functions of torque and pressure ratio in the reference inlet conditions, and wherein the second process quantity is the mass flow in the actual operating conditions. 19. A method according to claim 13, wherein the turbomachine is a pump for moving liquid, the pre-defined fluid properties at the inlet corresponding to a predefined a density of the liquid. 20. A method according to claim 13, wherein the rotational speed of the impeller is controlled on the basis of the estimate of the second process quantity. 21. A method according to claim 13, wherein at least one from the following list is controlled on the basis of the estimate of the second process quantity: one or more inlet guide vanes, one or more outlet guide vanes, one or more diffuser guide vanes. 22. A method according to claim 13, wherein start and stop commands are produced for one or more other turbomachines so as to keep the estimate on a desired range. 23. A turbomachine system comprising an inlet (202) and an outlet (203) for fluid to be moved and at least two turbomachines (200, 220, 230) each of which comprises: a chamber connected between the inlet and the outlet,an impeller placed in the chamber for moving the fluid, andequipments for measuring first process quantities related to that turbomachine, the turbomachine system further comprising a processor (208) arranged to calculate for each of the turbomachines an estimate for a second process quantity related to that turbomachine on the basis of measured values of the first process quantities and a reference table of interrelations between process quantities prevailing in reference inlet conditions which correspond to a pre-defined inlet fluid temperature, a pre-defined inlet fluid pressure, and pre-defined fluid properties at the inlet, characterized in that the reference table and the measured values of the first process quantities represent such a set of data values that the estimate is obtainable on the basis of different sub-sets of the set of data values, and the processor is arranged to give, in the calculation of the estimate, more weight to a first sub-set of the set of data values which has a smaller error estimate than to a second sub-set of the set of data values which has a bigger error estimate in order to increase the accuracy of the estimate, the error estimate related to each sub-set being proportional to a scalar product of a vector of squares of sensitivities of the estimate with respect to the data values of that sub-set and a vector of variances of the data values of that sub-set, and the processor is arranged to start and stop one or more of the turbomachines so as to keep the estimates related to running turbomachines on a desired range. 24. A computer program for obtaining an estimate for a process quantity related to a turbomachine that comprises a chamber having an inlet and an outlet for fluid to be moved, an impeller placed in the chamber for moving the fluid, and equipment for measuring first process quantities related to the turbomachine, the computer program comprising computer executable instructions for controlling a programmable processor to calculate an estimate for a second process quantity related to the turbomachine on the basis of measured values of the first process quantities and a reference table of interrelations between process quantities prevailing in reference inlet conditions which correspond to a pre-defined inlet fluid temperature, a pre-defined inlet fluid pressure, and pre-defined fluid properties at the inlet, characterized in that the reference table and the measured values of the first process quantities represent such a set of data values that the estimate is obtainable on the basis of different sub-sets of the set of data values, and the computer program comprises computer executable instructions for controlling the programmable processor to give, in the calculation of the estimate, more weight to a first subset of the set of data values which has a smaller error estimate than to a second sub-set of the set of data values which has a greater error estimate in order to increase the accuracy of the estimate, the error estimate related to each sub-set being proportional to a scalar product of a vector of squares of sensitivities of the estimate with respect to the data values of that sub-set and a vector of variances of the data values of that sub-set. 25. A computer program according to claim 24, further comprising computer executable instructions for controlling the programmable processor to control the rotational speed of the impeller on the basis of the estimate of the second process quantity. 26. A computer program according to claim 24, further comprising computer executable instructions for controlling the programmable processor to produce start and stop commands for one or more other turbomachines so as to keep the estimate on a desired range. 27. A computer program product comprising a computer readable medium, characterized in that the computer readable medium is encoded with a computer program according to claim 24.