Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
  • F04D27/001—Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring
• • 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
• • 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
  • F05D2270/3015—Pressure differential pressure

Definitions

• the invention relates to a method for determining the operating point of a Fan according to the preamble of claim 1, a method for Determination of the operating point of a fan and a fan according to the preamble of claim 8.
• EP-B 0 419 798 describes a generic method and a Generic device for determining the volume flow of a Radial fan known.
• the radial fan has at least one Flow opening limiting and the associated radial impeller upstream inlet nozzle. At least partially at a measuring point in the area the inner circumference of the inflow nozzle in the area in front of it
• the throughflow opening is designed as a static pressure measuring device Arranged measuring device and a located in the area of the measuring point Nozzle wall opening connected.
• the object of the invention is a method according to the preamble of claim 1 and a corresponding fan according to the preamble of claim 9 develop a determination of the operating point in the installed state, d. H. without external measuring section and calibration as well as an assessment of the quality of the Enable determination and a high level of reliability and thus a high level Ensure operational security.
• the shaft power P M W is a good measure of the power of the fan impeller applied to convey the gas.
• the motor power P M M of the fan motor can also be measured and converted into the shaft power P M W.
• the setpoint value of the total pressure difference ⁇ p S t belonging to the volume flow V is then determined from an existing operating characteristic curve ⁇ p (V) and compared with the measured total pressure difference ⁇ p M t .
• the setpoint value of the shaft power P S W belonging to the volume flow V is also determined from an existing operating characteristic curve P W (V) and compared with the measured shaft power P M W.
• the operating point and its quality are determined on the basis of the agreement or deviation of the target values ⁇ p S t and P S W, the measured values ⁇ pMt and P M W. If one or both values agree well with their measured values, the operating point determined from the volume flow V and the total pressure ⁇ p M t is determined with high accuracy. A corresponding accuracy class is assigned.
• the advantage of the method according to the invention is that the operating point of the Fan determined in the installed state with specification of the accuracy classes can be. Unfavorable inflow conditions are considered when determining the Operating point recognized and generally lead to the determination of values less accuracy. Inadmissible operating points can also be used with this Procedures for determining the operating point are determined. It will also gradual failures and total failures of the measuring sensors to Example recognized by clogging measuring points. A false alarm is avoided and can be intercepted by qualified warnings.
• the setpoints ⁇ p S t and P S W are according to claim 2 with the aid of transmitted configuration values, such as the nominal diameter D of the fan or dimensions of the inlet nozzle, and measured state values, such as the external pressure Pa, the temperature T, the engine speed n or the speed of the fan wheel n * and determined from model characteristics.
• Model characteristic curves are characteristic curves that are recorded and standardized on a test bench using a fan model, ie they are standardized type characteristic curves. Model characteristics are stored for the pressure figure ⁇ ( ⁇ ), the efficiency ⁇ ( ⁇ ) and possibly the performance figure ⁇ (in) depending on the flow figure nie.
• the determination of the setpoints ⁇ p S t and P S w from the model characteristics ⁇ ( ⁇ ) and ⁇ ( ⁇ ) for a current installation state enables the use of a fan with an integrated, appropriately programmed microcontroller and a system interface.
• a state variable for example the density ⁇ of the conveyed gas
• a state variable for example the density ⁇ of the conveyed gas
• the shaft power P M W is also measured in the environment and the total pressure difference ⁇ p M t .
• the determination of the volume flow V and the state value is carried out in iteration steps.
• the comparison of the desired value for the shaft power P S W derived from the determined volume flow V with its measured value P M W enables the assignment of an accuracy class.
• the dependence of the nozzle coefficient ⁇ corresponding to this pressure difference ⁇ p M W on the Reynold number Re in iteration steps can be taken into account when determining the volume flow V from the measured pressure difference ⁇ p M W.
• at least one model characteristic curve ⁇ (Re) measured on a model inflow nozzle installed in a model fan is stored.
• an average nozzle coefficient ⁇ is inserted in the first iteration step.
• a Reynolds number Re can be determined from the volume flow V determined in the first iteration step and a second nozzle coefficient ⁇ can be read from the model characteristic curve ⁇ (Re).
• the second iteration step is carried out with the second nozzle coefficient ⁇ .
• the values determined from the characteristic curves in the form of factors dependent on the operating state of the fan, in particular the factor k to take into account internal losses and / or the factor f can be upgraded or depreciated to take into account the compression of the gas extracted.
• the factors determined from the characteristic curves in the form of factors dependent on the operating state of the fan in particular the factor k to take into account internal losses and / or the factor f can be upgraded or depreciated to take into account the compression of the gas extracted.
• e.g. B. stored on several sizes of the type series of the fan characteristic curves for the factor k depending on the rotational speed u of the fan wheel and characteristic curves or calculation instructions for the factor f depending on the total pressure difference ⁇ p t . Taking this upward or downward valuation into account leads to an even more precise determination of the operating point and is necessary to assign a higher accuracy class.
• a measurement of two differential pressure differences .DELTA.p M w1 / 3 and .DELTA.p M w2 / 3 in the inflow nozzle according to claim 6 enables a check of the quality of the inflow and the measuring points.
• the quality of the inflow is checked by comparing the ratio of the pressure differences ⁇ p M w 1/3 to ⁇ p M w 2/3 with the known value of the square of the reciprocal ratio of the corresponding nozzle coefficients ( ⁇ 2/3 / ⁇ 1/3 ) 2nd
• the operating point can be determined with each of the two pressure differences ⁇ p M w1 / 3 and ⁇ p M w2 / 3 using the assigned flow coefficients ⁇ 1/3 and ⁇ 2/3 determined and stored on the model of a fan with an inflow nozzle . Differences that occur indicate faulty measuring points.
• measuring points can be the mean value for determination the operating point of the fan.
• the character of the inflow by comparing the in the center and at the Inlet nozzle measured pressure and when assigning a Accuracy class are taken into account. If the pressure in the center is less than on the inlet nozzle, the flow is swirling.
• a fan according to claim 9 is for performing a method according to the Claims 1 to 8
• a fan according to claim 10 is particularly for Implementation of a method according to claim 2 and fans according to the Claims 10, 11 and 12 are particularly suitable for carrying out processes according to claims 6, 7 and 8 suitable.
• a fan according to claim 9 with a motor, an impeller, a housing, an inlet nozzle, with at least one pressure measuring point and an associated device for processing the measured values has measuring points for measuring one or more differential pressure differences ⁇ p M w , measuring points for Measurement of the total pressure ⁇ p M t and possibly a power measuring device for measuring the shaft power P M W of the fan.
• the fan according to claim 10 simple measuring devices, namely a tachometer, a Temperature sensor and an absolute pressure sensor.
• the inflow nozzle has a further plane A2 Pressure measuring points on and according to claim 12 are in levels A1 to A3 in the Inlet nozzle of the radial fan and in level A4 in the housing of the fan Four pressure measuring points each arranged on a circumference.
• the four Pressure measuring points are, for example, connected to one another by a ring line connected.
• the ring lines are connected to corresponding pressure sensors.
• Figure 1 shows a side view of an arrangement of a Radial fan according to the invention with its motor, being through a housing of the radial fan and a bearing a vertical section through the axis of rotation is placed
• Figure 2 shows a section perpendicular to the axis of rotation through the Centrifugal fan.
• the inlet nozzle somewhat in FIG. 1 and stronger in FIG. 2 Dimensions stretched parallel to the axis of rotation of the fan wheel.
• Figure 1 shows a one-sided suction radial fan 1 with a bearing 2 and a motor 3.
• the bearing 2 is designed as a bearing block, with a Opening provided plates of a base frame 4 and the motor 3 via a Motor plate 5 attached to this base frame 4.
• a drive shaft 6 starting from the motor 3 is interrupted by a torque measuring device 7 flanged on both sides for measuring the shaft power P M W.
• the drive shaft 6 is guided behind the torque measuring device 7 through the bearing 8 of the bearing 2.
• the radial fan 1 has a housing, one of which is shown in FIGS. 1 and 2
• Lid closure disc 9 and an opposite side wall 10 can be seen are a retracted inflow nozzle with an outer tube section 11 and an inner nozzle section 12 and an impeller with a cover disk 13, Blades 14, a hub disc 15 and a hub 16.
• this hub 16 is inserted through the bearing 8 drive shaft 6 with a snug fit.
• the pipe section 11 has an outer connecting flange 17, which the Inflow opening 18 is limited and its outer diameter too Nominal diameter of the radial fan is called, and an inner Connection flange 19 on which the inflow nozzle on the cover closure disk 9 is attached to.
• the nozzle section 12 of the inflow nozzle is, as in FIG. 2 can be seen more clearly at the inner end of the Pipe section 11 inserted a little into this and seamless with it welded.
• the inflow nozzle is when attaching its inner Connection flange 19 together with the cover plate 13 of the impeller and centered with the impeller.
• the nozzle section 12 of the inflow nozzle points from the pipe section 11 an inlet cone 20 and a circular arc section 21 which has a nozzle neck and forms a diffuser and its narrowest diameter is approximately in the middle located on.
• the axial extent of the inlet cone 20 is approximately half as large like that of the circular arc section 21.
• the inlet cone 20 connects tangentially the circular arc section 21.
• the inner end of the circular arc section 21 protrudes into the cover disk 13. Between circular arc section 21 of nozzle section 12 and cover plate 13 remains a small circumferential, by centering the inlet nozzle with the Cover plate 13 constant wide air gap 22 free.
• the housing of the radial fan has a rectangular outflow opening 23 on, which is arranged perpendicular to the inflow opening 18 and from the Lid closure disc 9 and the side wall 10 and one not to be seen Housing shell is limited.
• the cross-sectional areas of the rectangular The outflow opening 23 and the round inflow opening 18 are of the same size.
• the tube section 11 of the inlet nozzle are in one in its outer half Level A1 perpendicular to the inflow direction 24 four evenly distributed on the circumference Holes 25.
• the positions of the holes 25 are on the Blow-out direction 26 oriented.
• the through holes 25 are either parallel to Outflow direction 26 or arranged perpendicular to it.
• the through holes 25 can also be arranged so that an over an angle of 60 ° extending circumferential area of the inflow nozzle, measured against the Spiral opening starting from the longitudinal axis of the housing outlet crossing at right angles, radially with respect to the longitudinal axis of the nozzle extending radial axis or line remains free of perforations.
• a Bore 25 could be in the circumferential area in the direction of the spiral opening starting from the radial line mentioned above.
• the diameter of the through holes 25 is 2 to 4 mm, here 3 mm.
• the Bores 25 are sharp-edged and deburred to the inner wall.
• the Holes 25 are outside of pipe nipples 27, which are gas-tight with the Pipe section 11 are connected, overhanging.
• the outside diameter of the Pipe nipple 27 is 6 mm, for example.
• the four pipe nipples 27 are connected to each other by a ring line 28. From the ring line 28 leads a connecting line 29 to an outside of the inlet nozzle, namely on the base frame 5 below the storage 2 between the two plates in Pressure sensor 30 arranged in a protected position.
• nozzle section 12 In the nozzle section 12 are in a plane A2 parallel to the plane A1, which is in the Inlet cone 20 is located near the transition to the circular arc section 21, and in a plane A3 the narrowest diameter of the circular arc section 21 also four each, at the same angles on the circumference as the perforations 25 arranged through holes 31, 32.
• These through holes 31, 32 are each with pipe nipples, a ring line, a connecting line.
• the Pipe nipples, the ring and connecting lines are not shown.
• the connecting line of the through holes 32 of the plane A3 is also on the as Differential pressure sensor trained pressure sensor 30 connected.
• Nearby the pressure sensor 30 is another, also as a differential pressure sensor trained (not shown) pressure sensor to which the connecting line of the holes 31 of the level A2 and the connecting line of the Bores 32 of the A3 plane are connected.
• Absolute pressure sensor arranged for measuring the ambient pressure Pa.
• a switch box 34 in which a Microcontrollers, signal conditioning devices such as frequency converters and Amplifier, and a power supply, e.g. B. there is a battery, arranged.
• the microcontroller is connected to a via a BUS line Data processing device, for example a PC, connected.
• BUS line Data processing device for example a PC
• the speed sensor 36 can also be on the impeller of the radial fan 1 be arranged.
• the torque measuring device 7 is also via a line (not shown) and the interface connected to the microcontroller.
• Nominal diameter D of the radial fan 1 is 800 mm
• the diameter of the outer connecting flange 17 is 800 mm
• the inner diameter 788 mm the narrowest diameter of the nozzle section 11,577 mm
• the diameter of the Cover plate 12 of the impeller 629 mm the axial length of the tube section 10 the inflow nozzle 180 mm and that of the nozzle section 12 261 mm.
• the Circular arc section 20 corresponds to an arc of 72 ° with a radius of 150 mm.
• the angle between the pipe section 10 and the inlet cone 19 of the Nozzle section 11 is 36 °.
• the area ratios A1: A2: A3 are 1: 0.81: 0.52
• Static pressure tapping points are located in the center of levels A1 to A3, only the static pressure tapping point 37 of level A1 in FIG. 2 is located, arranged.
• the static pressure tapping point 37 is on as one three struts attached static pressure probe.
• the memory of the microcontroller contains standardized type characteristics ⁇ ( ⁇ ), ⁇ ( ⁇ ), if necessary. also ⁇ ( ⁇ ), also called model characteristics, for the type series of Radialventialtors 1.
• ⁇ is the flow number
• ⁇ ( ⁇ ) the pressure number
• ⁇ ( ⁇ ) the Efficiency
• ⁇ ( ⁇ ) the delivery number.
• the type curves were made Test bench characteristics that are required for a geometrically similar model radial fan, for example with the nominal diameter of 400 mm.
• the memory of the microcontroller contains the Reynold number Re dependent dimensionless nozzle coefficients ⁇ (Re) for differential pressures between the Levels A1 and A3 and between levels A2 and A3, and thus characteristic curves for the inlet nozzle.
• These flow coefficients ⁇ (Re) were obtained from measurements in an Model radial fan built-in geometrically similar built-in nozzle.
• the microcontroller memory also contains configuration values such as the Nominal diameter D (800 mm), the installation situation, the gas type and the Solid loading.
• a radial fan according to the invention can in the Levels 1, 2, 3 and 4 instead of four holes only one hole each to be appropriate. This perforation should, for example, to avoid Constipation due to condensation, at levels 1, 2 and 3 in the upper one Half of the inlet nozzle should be arranged.
• the measured values for the pressure difference ⁇ p M w1 / 3 , optionally the pressure difference ⁇ p M w2 / 3 , the total pressure difference ⁇ p M t and, if appropriate, the shaft power P S W and the measured values of the state values are first, for example of the external pressure Pa, the temperature T, the speed n of the motor 3 or the fan wheel n *.
• the measured value for the shaft power P M W is calculated from the measured torque M M if the torque measuring device 7 is present.
• a second pressure difference ⁇ p M w2 / 3 is also measured, the ratio of the pressure differences ⁇ p M w 1/3 / ⁇ p M w 2/3 with the square of the reciprocal ratio the corresponding mean nozzle coefficients ( ⁇ 2/3 / ⁇ 1/3 ) 2 are compared.
• a match within + -10% indicates a sufficiently undisturbed flow in the inflow nozzle and functioning measuring points, ie here free bores 25, 31, 32.
• the volume flow V is determined according to equation (1) from the differential pressure difference ⁇ p M w 1/3 .
• V ⁇ 1/3 A3 ⁇ ((2 / ⁇ ) ⁇ p M w 1/3 )
• ⁇ 1/3 is the nozzle coefficient for the flow conditions between the planes A1 and A3 in the inflow nozzle
• a 3 is the cross section of the inflow nozzle in the measuring plane A3
• ⁇ is the density of the gas conveyed.
• a 3 is known as one of the configuration values.
• the density ⁇ can be determined when air is conveyed from the temperature T measured in the inlet nozzle and the measured external pressure Pa.
• the volume flow V could also be determined from the pressure difference ⁇ p M w 2/3 with the corresponding nozzle coefficient ⁇ 2/3 .
• the dependence of the nozzle coefficients ⁇ 1/3 and ⁇ 2/3 on the Reynolds number Re can be taken into account by starting the determination of the volume flow V with an average nozzle value ⁇ , calculating a Reynolds number Re from the determined volume flow V and the associated nozzle coefficient ⁇ is taken to determine the volume flow V again.
• the configuration values inlet cross-section A D , nominal diameter D and the viscosity ⁇ of the pumped gas, here the air are required. After a few iteration steps, the values for the volume flow V and the corresponding nozzle coefficient ⁇ correspond.
• the inlet cross-section A D and the circulation speed u of the fan wheel calculated from the state value of the speed n of the motor 3 or the fan wheel n * and the flow rate ⁇ and the pressure characteristic from the model characteristic curve can be calculated using the configuration value Find ⁇ ( ⁇ ).
• the values of the model characteristic curves can be upgraded or downgraded in order to determine the operating point precisely.
• the measured dependency of an upgrade or depreciation factor k ( ⁇ or> 1) on a variable dependent on the circulation speed u of the fan wheel, the nominal diameter D and the viscosity ⁇ is used.
• an upgrade or depreciation factor f is used depending on the measured total pressure difference ⁇ p M t .
• a value for the efficiency ⁇ ( ⁇ ) can be read from the model characteristic curve from the determined volume flow V and the pressure figure ⁇ derived from it. This value may also be upgraded or depreciated by the factors k and f.
• the nominal value for the shaft power P S W results from the volume flow V, the total pressure difference ⁇ p M t, the value for the efficiency ⁇ ( ⁇ ) and, if applicable, the factor k and f. This value P S W is compared with the measured shaft power P M W to assess the quality of the operating point determination.
• the measured torque M M is converted into the shaft power P M W.
• a good agreement ( ⁇ 2% deviation) indicates a high accuracy class.
• a measuring device for the motor power P M M with devices for measuring the current I M absorbed by the motor 3, the supply voltage U and the power factor can also be used cos ⁇ be used.
• the measured value for the motor power P M M is the current consumption l M of the motor 3, the voltage U, the power factor cos ⁇ and the efficiency ⁇ m of the motor 3 are calculated and converted into the shaft power P M W with the aid of an efficiency ⁇ a which is also stored. Because the efficiencies ⁇ m are only approximately known, only a lower accuracy class can be assigned if only the measured and setpoint values P M W and P S W match.
• a method for determining the operating point and a state variable, namely the density ⁇ of the conveyed gas, differs from the method described above in that the determination of the volume flow V and the density ⁇ using one of the pressure differences ⁇ p M w 1/3 or ⁇ p M w 2/3 and the total pressure difference ⁇ p M t is carried out in several iteration steps.
• an initial density ⁇ is calculated, for example calculated from the temperature T and the external pressure Pa.
• the dependence of the nozzle coefficient ⁇ 1/3 or ⁇ 1/3 on the Reynolds number Re is taken into account by iteration in each iteration step.
• the result is a volume flow V, a corresponding flow figure ⁇ , factors k, f and the density ⁇ , from which the air humidity can be calculated if necessary.
• the shaft power P S W is determined from the available values and compared with the measured shaft power P M W and an accuracy class is assigned.
• a radial fan according to the invention with a nominal diameter of 800 mm is in a system that sucks up the dust from a planing and grinding line, built-in.
• the radial fan's inlet nozzle is straight Pipe section with a diameter of 800 mm and a length of 5 m flanged.
• In front of the outflow opening 23 is a rectangular channel and over it a transfer element a pipe leading to a filter (with control flap) connected.
• the radial fan has a measuring device for the motor power P M M with devices for measuring the current J, the voltage U and the power factor cos ⁇ on.
• the configuration value efficiency ⁇ m of the motor 3 and the efficiency ⁇ a are stored in the microcontroller to determine the measured shaft power P M W.
• the volume flow V is determined in accordance with equation (1a) from the differential pressure ⁇ p M W1 / 3 , the density ⁇ required for this being calculated from the measured temperature T and the measured external pressure Pa.
• the dependence of the nozzle coefficient ⁇ 1/3 on the Reynolds number Re determined in the model characteristic curve is taken into account by an iterative determination of the volume V and the nozzle coefficient ⁇ 1/3 , starting with an average nozzle coefficient ⁇ 1/3 .
• the flow figure ⁇ is determined from this volume flow V with the aid of configuration and status values and the pressure figure ⁇ ( ⁇ ) from the model characteristic curve. This value is upgraded or depreciated by the determined factors k and f and used to determine the target value of the total pressure difference ⁇ p S t . .
• This total pressure difference ⁇ p S t is compared with the measured total pressure difference ⁇ p M t .
• the deviation of the two values is 0.8%.
• a value for the efficiency ⁇ ( ⁇ ) is additionally read from the model characteristic curve from the flow rate value ⁇ determined above and upgraded or depreciated by the factors k and f.
• the nominal value of the shaft power P S W is calculated from this value and the power factor from the measured current consumption I M using the operating voltage U. cos ⁇ , the efficiency of the motor ⁇ m and the efficiency ⁇ a determined value for the shaft power P M W compared.
• the measured shaft power P M W is 5.6% above the nominal value of the shaft power P S W derived from the volume flow V.
• the somewhat higher value of the measured shaft power P M W could be due to the additional solids conveyance due to the planing and grinding dust.
• the determination of the measured shaft power P M W via the current consumption M is less precise because of the only approximately known efficiency.
• a radial fan 1 according to the invention also with a nominal diameter of 800 mm is in a drying system to convey exhaust air to one Heat exchanger installed.
• the installation situation leads to a swirl-free attachment and Outflow of the exhaust air, which has a variable water vapor content and a variable Temperature T.
• the speed n * of the fan wheel is one Humidity control set via a frequency converter.
• the radial fan 1 has a torque measuring device 7 and on its motor 3 Current measuring device.
• the ratio of the pressure differences ⁇ p M w 1/3 / ⁇ p M w 2/3 with the known square of the reciprocal ratio of the corresponding nozzle coefficients ( ⁇ 2/3 / ⁇ 1/3 ) is first checked to check the flow and the measuring points. 2 compared. The two values agree within 10%. From this it can be concluded that the measuring points are working and the inflow, as assumed by the installation situation, is swirl-free.
• the volume flow V and the necessary density ⁇ are determined from the pressure difference ⁇ p M w 1/3 with the aid of the measured total pressure difference ⁇ p M t in iteration steps, taking into account the dependency of the nozzle coefficient ⁇ 1/3 on the Reynolds number Re iteratively in each iteration step becomes.
• a value for the density ⁇ calculated from the temperature T and the ambient pressure Pa is started.
• a value for the volume flow V and the nozzle coefficient ⁇ 1/3 is determined iteratively from ⁇ p M w 1/3 .
• the flow figure ⁇ is determined from the volume flow V and the value of the pressure figure ⁇ ( ⁇ ) is derived from the model characteristic curve.
• the revaluation or depreciation factors k and f are determined.
• a value for the density ⁇ is calculated, with which the second iteration step is carried out. After a few iteration steps, there are no more deviations in the values of the volume flow V and the density ⁇ .
• the shaft power P S W is calculated from the derived value for the efficiency ⁇ ( ⁇ ), the already known factors k and f and the total pressure difference ⁇ p M t and with the shaft power P determined from the torque M M , ie with the measured shaft power P M W compared.
• the measured value P M W is only 3.5% higher than the calculated value P S W. This suggests an exact determination of the volume flow V and the total pressure difference ⁇ p M t .
• the determination of the operating point corresponds to an accuracy class of 0.
• the measured shaft power P M W is determined with the aid of a device for measuring the current consumption P M M from the current consumption of the motor 3 of the radial fan 1, the state values of the operating voltage U and the power factor cos ⁇ and the configuration values efficiency ⁇ m of the motor 3 and efficiency ⁇ a .
• This measured value P M W is about 10% above the calculated value P S W.
• This deviation and the less precise determination of the measured shaft power P M W with the aid of a current measuring device would assign the operating point determination to an accuracy class of 2 in the case of an exclusive determination of the measured shaft power P M W with the aid of a current measurement I M and a determination of the motor power P M M lead.
• the ratio of the pressure differences ⁇ p M w 1/3 / ⁇ p M w 2/3 is compared with the square of the reciprocal ratio of the corresponding nozzle coefficients ( ⁇ 2/3 / ⁇ 1/3 ) 2 .
• the ratio of the pressure differences ⁇ p M w 1/3 / ⁇ p M w 2/3 is slightly higher than its nominal value, but is within the tolerance range of + -10% deviation. From this it can be concluded that the measuring points are working. A completely swirl-free flow cannot be assumed due to the upstream manifold.
• the volume flow V is determined from the pressure difference ⁇ p M w 1/3 , the dependence of the nozzle coefficient ⁇ 1/3 being taken into account by iteration steps as in the previous examples.
• the flow figure ⁇ , the pressure figure ⁇ ( ⁇ ), the up or down valuation factors k and f and finally the total pressure difference ⁇ p S t are derived from the volume flow V.
• the measured value for the total pressure difference ⁇ p M t is (by about 8.9%) significantly below this calculated value ⁇ p S t .
• the measured value of the shaft power P M W, determined from the current consumption l M, is (by about 6.5%) lower than that from the volume flow V, the flow figure ⁇ , the efficiency ⁇ ( ⁇ ), the factors k and f and the measured total pressure difference ⁇ p M t calculated setpoint for the power P S W.
• An accuracy class of 2 is assigned to the determined operating point with the calculated volume flow V and the measured total pressure difference ⁇ p M t due to the inaccuracy due to the changed flow profile. Since both setpoints ⁇ p S t and P S W are higher than their measured values, the flow can be described by characteristic curves shifted to lower values. A higher accuracy of determining the operating point with V and ⁇ p M t is likely.
• a current measuring device In front of the inflow nozzle of a radial fan 1 according to the invention with a Nominal diameter of 800 mm and a current measuring device is one for one Swirl-free inflow, sufficiently long inflow pipe arranged.
• the ratio of the pressure differences ⁇ p M w1 / 3 / ⁇ p M w2 / 3 is compared with the square of the reciprocal ratio of the corresponding nozzle coefficients ( ⁇ 2/3 / ⁇ 1/2 ) 2 .
• the ratio of the pressure differences ⁇ p M w 1/3 / ⁇ p M w 2/3 is about 20% lower than its setpoint. From this, a fault can already be concluded.
• volume flow V which is determined from the pressure difference ⁇ p M w 1/3 and taking into account the dependence of the nozzle coefficient ⁇ 1/3 on the Reynolds number Re, the nominal values of the total pressure difference ⁇ p S t and the shaft power P M W are calculated.
• a comparison with the measured values ⁇ p M t and P M W shows that the two calculated values ⁇ p S t and P S W are below the corresponding measured values ⁇ p M t and P M W.
• an increased volume flow V can be inferred from the model characteristics. This determination of the operating point from volume flow V and measured total pressure difference ⁇ p M t is assigned an accuracy class of 3.
• the volume flow V is also determined from the pressure difference ⁇ p M w 2/3 .
• This volume flow V and the values derived therefrom for the total pressure difference ⁇ p S t and the power P S M agree well with the corresponding measured values ⁇ p M t and P M W.
• the accuracy class from 0 to 1 is assigned to this determination. This information is saved with a corresponding warning and displayed if necessary.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Positive-Displacement Air Blowers (AREA)
• Measuring Volume Flow (AREA)
• Control Of Electric Motors In General (AREA)

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• 1997
  • 1997-06-23 DE DE19726547A patent/DE19726547A1/de not_active Withdrawn
• 1998
  • 1998-04-25 AT AT98107573T patent/ATE263926T1/de not_active IP Right Cessation
  • 1998-04-25 DE DE59811133T patent/DE59811133D1/de not_active Expired - Fee Related
  • 1998-04-25 EP EP98107573A patent/EP0887555B1/fr not_active Expired - Lifetime
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