Aircraft engine blade tip monitoring using pulsed eddy. Calibration methods for eddy current measurement systems. Eddy current sensor system for blade tip clearance. Eddy current transducer installation part 2thrust position. The eddy current method is based on the principle of generating circular electrical currents eddy currents in a conductive material. To monitor the vibration of blades in rotating machinery, the contactless method called blade tip timing btt is widely used.
Rotating bladed disk, blade tip timing, eddy current sensors, blade tip clearance, coupled mechanical and electromagnetic problem. Present industrial standard sensors used in tip timing systems such as optical, capacitance, hall effect etc. Spc371r1afe spring loaded probe spc629 spc4161 spc624diffinc spc623diffinc spc621 flangetube well spc620mtl. Maintaining turbine clearance control of aircraft gas turbines. Portable and lightweight, our eddy current array flaw detection solutions including an extensive series of compatible test probes are designed for high frequency surface to low frequency subsurface inspections for weld, aerospace including rotary and general purpose inspections. Although probe tip to tip clearances are not normally an issue on most machines, it should be noted that proximity probe probes radiate an rf field larger than the probe tip itself. Analysis of eddycurrent losses over conductive substrates. Type coil tip angle length drop frequency shaft size connector part id item n. Meyer, fellow, ieee abstract in this paper, a closedform integral representation for the eddycurrent losses over a conductive substrate is presented. The efficiency and reliability of turbomachinery will be improved by blade tip clearance btc and blade tip timing btt monitoring. Hood technology has built a large number of optical and eddy current sensors for testing on many different platforms. The mm sensors have a range up to 7mm whereas the 6mm sensors have a range of about 3mm. Blade vibration and clearance are important diagnostic features for condition monitoring, including the detection of blade cracks. The system provides an output voltage that is directly proportional to the distance between the probe tip and the observed conductive surface.
Evaluation and improvement of eddy current position. Get more information about eddy current brakes pdf download by visiting this link. A transmitreceive pulsed eddy current probe that could detect changes in the blades coordinates was employed for this purpose. Many different sensing principles have been utilized for tip clearance and tip timing measurements. To properly calibrate an eddy current probe, several possibilities exist. In this study, the influence of tip clearance size on the steady flowfield and aerodynamic damping is. Abstract blade tip timing is a contactless method used to monitor the vibration of blades in. Assessment of eddy current testing for the detection of. The measurement of the tip clearance and the time of arrival of every single blade in rotating turbo machinery is the starting point to characterize the performance of a rotating turbine. Various sensing strategies have been proposed over the years to measure blade tip clearance. A new combined sensor that can measure tip timing, tip clearance and dynamic pressure was developed at the university of oxford for use in gas turbine engine health monitoring. To overcome this downside, eddy current sensors are a good. Influence of the tip clearance on a compressor blade. And the future work will focus on the high temperature issues.
General surface probes, aerospace probes, dedicated inspection probes and accessories. Direct or indirect measurement of blade parameters time, clearance, vibration, pitch angle, etc is generally performed through optical, capacitive, and eddy current sensors 3. Proximity sensors, probes and transducer systems bently. A major advantage the eddy current sensor over the other. The spatial penetration of a blade tip into the hf electromagnetic field induces eddy currents in the blade tip.
Eddy current technique is an important electromagnetic nondestructive evaluation technique. During steady state operations, aircraft engine blade tip clearance and inter blade spacing remain constant. Rao nondestructive evaluation division metallurgy and materials group indira gandhi center for atomic research kalpakkam 603 102, tn, india email. As an example, model cmss65 and 68 should never be installed with less than one 1 inch of probe tip to tip clearance. Specifications are liable to change without notice. Non destructive testing eddy current testing, wirbelstrom.
They can provide highly accurate blade tip timing data in both analogue and digital forms and in realtime. A plurality of vane sectors define a stator ring including a blade shroud. To effectively monitor the vibration of blades in a rotating machine, a non contacting method called blade tip timing btt has been used. A passive blade detection sensor exploits the electrically conductive trait of typical turbo machinery components such as fan, compressor and turbine blades. Buckley pdf, 429 kb eddy current testing at level 2, international atomic energy agency, vienna, 2011 pdf 5. The system provides a blade shroud that is isolated from the component case and can move radially to maintain blade clearance. Modelling and experimental validation of active and passive eddy current sensors for blade tip timing. The system can measure both static position and dynamic vibration data. Aug 17, 2017 a new combined sensor that can measure tip timing, tip clearance and dynamic pressure was developed at the university of oxford for use in gas turbine engine health monitoring. If a defect appears in the effective area, the eddy current have to take a different way, this changes the impedance of. Different types of probes have been proposed and are currently used to monitor these parameters.
We study the effects of tip clearance and blade velocity on the measurement. The combined sensor uses a pressure sensor in the centre and is enclosed by an eddy current sensor forming a compact single package. Astm e3052 standard practice for examination of carbon steel welds using eddy current array. The electrically conductive blade allows eddy currents to flow briefly as it passes. This model is demonstrated by simulating the effect of tip clearance, blade geometry, and blade velocity on the output of the eddy current. Investigation on the turbine blade tip clearance monitoring. Pdf blade tip timing is a contactless method used to monitor the vibration of blades in rotating machinery. Blade tip sensors are commonly used for monitoring bladed disks in rocket and gas engines, as well as in steam turbines. The illustrations shown are for reference only and may not be to scale.
The quantity of interest in most forms of eddy current inspection is z, the change in probe impedance induced by a flaw. Evaluation and improvement of eddy current position sensors. Tipclearance measurements on an engine high pressure turbine using an eddy current sensor. In order to provide strong validation for the current study, it was decided to. Each eddy current probe available from ndts has a unique code. The firstofitskind experimental data from transient thermal measurements. The past investigations using eddy current testing in blade tip. The measurements shown in the tables are metric with the equivalent imperial size in brackets i. One way to reduce an aircraft engines emissions and improve engine performance is through active clearance control acc. While eddy current sensors of various forms are knownincluding passive types where. The investigation encompasses development and validation of an integrated sensor design to provide tip clearance measurements.
The sensing strategies used for the purpose of measuring are based on microwaves sensing system, capacitance probe, laser, optics and eddy currents. Evaluation and improvement of eddy current position sensors in magnetically suspended flywheel systems timothy p. Eddy current losses in transformer windings and circuit wiring. The first involves a capacitancebased blade tip clearance measurement system 2 developed under phase i and ii sbir.
The coil red causes a magnetic field, which initiate eddy current. This catalogue features the standard range of ge eddy current probes and accessories. Thus, quantitative inversion of eddy current signals to obtain flaw sizes requires methods for calibrating eddy current measurement systems. The sensors were flush mounted with the inner wall of the casing, the cold blade tip clearance was estimated to be approximately3. Progress in largeeddy simulation of a rotor tipclearance flow. The work provides experience in eddy current sensor design in different application, not only in turbine.
An introduction to eddy current testing from the ndendt resource center. Several eddy current sensor installations have been in continuous operation for over 2 years in gas turbine engines and steam turbines with no degradation in signal quality. Online monitoring of dynamic tip clearance of turbine. The combined sensor uses a pressure sensor in the centre and is enclosed by an eddy current sensor forming a. The drawings below represents schematically how does eddy current works. Existing simulations for eddy current sensors have not considered the particular case of a blade rotating past the sensor. Blade tip clearance btc measurement and active clearance control acc are becoming crucial technologies in aeroengine health monitoring so as to. Two types of eddy current sensors were deployed to detect foded blades and dynamic fod events, mm and 6mm. A highfrequency hf electromagnetic field is emitted by a coil of the eddy current sensor. Simulating eddy current sensor outputs for blade tip timing nidhal. A numerical method for blade tip timing using an eddy current sensor is described in section the simulation of blade tip timing using an ecs, where mesh details and. The sensors are rugged and are often used in contaminated environments.
Eddy current probe catalog introduction 6 every section in this probe catalog begins with a short description of the different eddy current products available. Us6927567b1 passive eddy current blade detection sensor. Formation of fatigue damage in engine disk slots and. Eddy current technique is an important electromagnetic non. If you cannot find a probe or accessory to meet your inspection requirements, please contact your local. Some industries are currently using capacitive sensing system for blade tip clearance measurement. Proximity sensors, probes and transducer systems bently nevada. Pdf simulating eddy current sensor outputs for blade tip timing.
Eddy current is the swirling current produced in a conductor, which is subjected to a change in magnetic field. Eddy current probe tip to tip clearances although probe tip to tip clearances are not normally an issue on most machines, it should be noted that eddy current probes radiate an rf field larger than the probe tip itself. Development of a combined eddy current and pressure sensor. Tai services will supply all materials, labor and test equipment needed for the inspection. This is achieved by the use of a coil connected to an alternating current generator driving an alternating magnetic field primary field. Simulating eddy current sensor outputs for blade tip timing. Pdf blade tip clearance btc measurement and active clearance control acc are becoming crucial technologies in aeroengine health. Blade tip clearance btc measurement and active clearance control acc are becoming crucial technologies in aeroengine health monitoring so as to improve the efficiency and reliability as well as to ensure timely maintenance. The objective of this project is to develop large eddy simulation capability for flows through an axial flow rotor with tip clearance, and to gain a physical understanding of the unsteady flow characteristics in the endwall region downstream of the rotor. Modelling and experimental validation of active and. An eddy current sensor for use as a dynamic proximity sensor, particularly for monitoring of blade tip timing and clearance in turbomachinery, has a common coil for use in both generating a magnetic field in a proximate region and detecting the effect of eddy currents generated by said field in electrically conductive objects passing through that region. Their use in this application is well established and measurement accuracy is high. Eddy current technique is an important electromagnetic nondestructive evaluation technique that is widely used in power, aerospace, petrochemical and other industries for detection of surface.
Eddy current sensors in tip timing eddy current sensors are most commonly used for non contact proximityand displacement measurements. Tipclearance measurements on an engine high pressure turbine. Calibration of eddy current measurement systems is an important factor for attaining the accuracy and precision of measurement that quantitative nondestructive evaluation requires. A permanent magnet is placed strategically adjacent to a wire coil to generate a single pulseantipulse signal when a blade passes in front of the sensor. Modelling and experimental validation of active and passive. The effect of sensor characteristics on blade tip timing measurements n.
The mathematical methods employed in solving the relevant problems are. Electronic pulsewidthmodulated pwm variable frequency drives vfd may be costeffective replacements for aging or highmaintenance eddy current drives that are used with variable torque loads, such as centrifugal fans or pumps. This requires detailed modeling of eddy current sensors in the blade tip timing application. Jansen ohio aerospace institute, brook park, ohio prepared for the. Although eddy probe tip to tip clearances are not normally an issue on most machines, it should be noted that eddy probes radiate an rf field larger than the probe tip itself. The proposed development program will focus on the use of throughthecase eddy current sensors to measure blade tip clearance in real time. Verification and design of high precision eddy current sensor. Modelling and experimental validation of active and passive eddy. Several types of sensors such as eddy current, capacitance and optical probes are used to realize this objective. Simulating eddy current sensor outputs for blade tip.
Us6935836b2 compressor casing with passive tip clearance. Blade tip timing and blade tip clearance measurement. The doubleleakage tip clearance flow, its interaction with the tip clearance core vortex of the adjacent blade, and the resulting large mixing loss are the main flow mechanism of the large rotor tip gap in the compressor. Meyer, fellow, ieee abstract in this paper, a closedform integral representation for the eddycurrent. When the changing flux links with the core itself, it induces emf in the core which in turns sets up the circulating current called eddy current. Eddy current transducer installation part 1radial vibration. A passive clearance control system for a gas turbine engine component. A new high temperature eddy current sensor has been developed for application in turbo machinery tiptiming and tip clearance measurements to assess blade. The effect of sensor characteristics on blade tip timing.
The dynamic experiment proved the measuring range, resolution, response speed of designed sensor can meet the requirement of turbine blade tip clearance measurement. Sensing systems based on optics, capacitance, eddy current and microwave are present for tip clearance measurement. This section gives a short description on how to build a probe part number. Experimental investigation of high temperatureresistant. The question arises of what level of detailing is necessary for accurate aerodamping predictions. Eddy current sensor system for blade tip clearance measurement based on a speed adjustment model. This paper is intended to provide insight into these phenomena so that improved high frequency. Eddy current sensors were the first noncontact sensors developed and dealt with in the institute in early 1990s. Todays highperformance eddy current proximity sensors deliver continuous condition monitoring. Is it costeffective to replace old eddycurrent drives. It is usually used to measure blade tip clearance in kaplan turbines as well as runner band clearance.
Among other things, it explains i why eddy current losses increase so dramatically with more wind. Author links open overlay panel nidhal jamia a michael i. This is achieved by managing the clearance between the gas turbine casing and the tips of the rotating blades, referred to as turbine tip clearance. The cmss 785 system is an eddy current type noncontact displacementvibration system, used for measuring shaft vibration, axial position, rotating speed and phase. The development of a hot section eddy current sensor for. Aircraft engine blade tip monitoring using pulsed eddy current. Eddy current probes all specifications are subject to change without notice. Verification and design of high precision eddy current. The signal feeds directly into a digital signal processor that is capable of processing 12 signals simultaneously including signals from other types of sensors. Hood tech blade vibration monitoring capabilities overview. Completely from experimental perspective, the present study aimed to address the walltogas temperature ratio effect on turbine blade tip heat transfer. A new high temperature eddy current sensor has been developed for application in turbomachinery tip timing and tip clearance measurements to assess blade vibrations.
Underwater eddy current proximity sensor users manual. The flutter cfd calculations conducted in industry generally use a singlerow, singlepassage approach with a minimum of detailing to reduce the computational time as much as possible. Online monitoring of dynamic tip clearance of turbine blades. The results showed the sensor was able to perform at these extreme environments without losing accuracy. In assessing the et inspection technique, pnnl used a range of specimens from four different sources. Pdf blade tip clearance and time of arrival immediate. Laser based optic probe can measure the blade tip clearance. This study details development of a high temperature eddy current sensor system for hot section applications.
High temperature eddy current sensor system for turbine. Eddy current sensor ecs offers an attractive option for btc measurement due to its robustness, whereas current approaches have not considered two issues sufficiently. Based on their approach, the tip clearance measurements and the blade tip timing were simultaneously measured, leading to lower cost and time requirements. Techniques for blade tip clearance measurements with capacitive probes alexander steiner hytron gmbh, georg schr. As an example, model cmss65 and 68 probe should never be installed with less than one 1 inch of probe tip to tip clearance. The stator ring and the control ring are coupled together and mounted within the component by a plurality of radial. During steady state operations, aircraft engine blade tip clearance and interblade spacing remain constant. Pdf blade tip clearance btc measurement and active clearance control acc are becoming crucial technologies in aeroengine health monitoring so as. Different types of sensors are used to measure the tip clearance values in gas turbine engine. Noncontacting blade tip sensors the type of sensor selected depends upon a number of factors including, environment, standoff distance, resolution, duration of test and whether blade tip clearance monitoring is required. The sensor is designed to withstand temperatures of order 1500 to 1600k. Analysis of eddycurrent losses over conductive substrates with applications to monolithic inductors and transformers ali m. Pdf eddy current sensor system for blade tip clearance.46 42 1019 284 66 173 1306 701 823 1223 189 1095 682 285 1588 1065 1322 1693 342 569 1398 753 1491 1502 658 406 817 1256 851 1194 951 355 156 20 1472 929 1163 394 1064 1015 504 633 1478 77 455 1454