Compressor Blade Tip Timing Using Capacitance Tip Clearance Probes

2003 ◽  
Author(s):  
Craig Lawson ◽  
Paul Ivey
Keyword(s):  
Compressor Blade ◽  
Tip Clearance ◽  
Test Facility ◽  
Experimental Investigations ◽  
Blade Vibration ◽  
New Instrument ◽  
Timing Measurement ◽  
Measured Strain ◽  
Blade Tip ◽  
Capacitance Probe

Turbomachinery blade vibrations of sufficient amplitude cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. This paper provides new insights into the ability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device. Initial experimental investigations are reported where a compressor blade with mounted strain gauges is used in a low-speed compressor. Capacitance probe results are correlated with simultaneously measured strain gauge results. Finite Element simulations are also used. The performance of the capacitance system in measuring blade vibration is analysed. Measurements were facilitated by the commissioning of a new instrument dedicated compressor test facility and this test facility is described.

The Measurement of Turbomachinery Blade Vibration Through Tip Timing With Capacitance Tip Clearance Probes

2004 ◽  
Author(s):  
Craig Lawson ◽  
Paul C. Ivey
Keyword(s):  
High Cycle Fatigue ◽  
Tip Clearance ◽  
Cycle Fatigue ◽  
Dual Use ◽  
Blade Vibration ◽  
Timing Measurement ◽  
Probe System ◽  
Blade Tip ◽  
Capacitance Probe ◽  
Probe Sensor

Turbomachinery blade vibrations can cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. Much research and development has gone into investigating the ability of optical probes to achieve this. However, this paper looks at the potential for a dual use capacitance probe sensor to measure both tip timing and tip clearance. This paper provides new insights into the ability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device. This is done by correlating capacitance probe tip timing results with simultaneously measured blade-mounted strain gauge vibration results and precise rotational speeds. Thus the characterisation of the performance of the capacitance probe system when measuring blade vibration on a full-sized low-speed research compressor is analysed and reported.

On Possibilities of Using Relative Shaft Vibration Signals for Rotating Blades Monitoring

2018 ◽  
Author(s):  
Jindrich Liska ◽  
Vojtech Vasicek ◽  
Jan Jakl
Keyword(s):  
Steam Turbine ◽  
Operating Conditions ◽  
Vibration Monitoring ◽  
Monitoring Systems ◽  
Blade Vibration ◽  
Vibration Signals ◽  
Rotating Blades ◽  
Timing Measurement ◽  
Blade Tip ◽  
Shaft Vibration

Ensuring the reliability of the steam turbine is the key for its long life. For this purpose monitoring systems are standardly used. Early detection of any failure can avoid possible economical and material losses. A monitoring of rotating blades vibration belongs to the very important tasks of the turbomachinery state assessment. Especially in terms of the last stages of low-pressure part, where the longest blades are vibrating at most. Commonly used methods for blade vibration monitoring are based on contact measurement using strain gauges or non-contact approach based on blade tip timing measurement. Rising demand for low-cost monitoring systems has initiated development of a new approach in blade vibration monitoring task. The presented approach is based on usage of relative rotor vibration signals. Its advantage is in using of standardly installed sensors making this approach economically interesting for the turbine operators compared to the traditionally used methods, mentioned above. This paper summarizes the symptoms of blade vibration phenomenon in relative shaft vibration signals, the impact of operating conditions on the blade vibration amplitude and its comparison to blade tip-timing measurement results. In addition of several examples, the article also describes an evaluation of proposed method in operation of steam turbine with power of 170MW.

A Blade by Blade Tip Clearance Measurement System for Gas Turbine Applications

1994 ◽  
Author(s):  
A. G. Sheard ◽  
B. Killeen
Keyword(s):  
Gas Turbine ◽  
Measurement System ◽  
System Reliability ◽  
System Performance ◽  
Tip Clearance ◽  
Test Facility ◽  
Hostile Environment ◽  
Reliable Measurement ◽  
Blade Tip ◽  
Blade Tip Clearance

It is difficult to make a reliable measurement of running clearance in the hostile environment over the blading of a modern gas turbine. When engine manufacturers require the measurement to be made over every blade during live engine tests, system reliability, ruggedness and ease of operation are of primary importance. This paper describes a tip clearance measurement system that can measure clearance over every blade around a rotor. The measurement system concept is presented, and the system design described in detail. Commissioning of the measurement system on a compressor test facility, and the results obtained are discussed. An analysis of system performance during the commissioning trials concludes the paper.

Numerical Investigation of Tip Clearance Flow Induced Flutter in an Axial Research Compressor

2016 ◽  
Author(s):  
Daniel Möller ◽  
Maximilian Jüngst ◽  
Felix Holzinger ◽  
Christoph Brandstetter ◽  
Heinz-Peter Schiffer ◽  
...  
Keyword(s):  
Early Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Blade Vibration ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Clearance Flow ◽  
Fluctuation Pattern ◽  
Blade Tip ◽  
Pass Through

A flutter phenomenon was observed in a 1.5-stage configuration at the Darmstadt transonic compressor. This phenomenon is investigated numerically for different compressor speeds. The flutter occurs for the second eigenmode of the rotor blades and is caused by tip clearance flow which is able to pass through multiple rotor gaps at highly throttled operating points. The vibration pattern during flutter is accompanied by a pressure fluctuation pattern of the tip clearance flow which is interacting with the blade motion causing the aeroelastic instability. The velocity of the tip clearance flow fluctuation is about 50% of the blade tip speed for simulation and experiment and also matches the mean convective velocity inside the rotor gap. This is consistent for all compressor speeds. From this investigations, general guidelines are drawn which can be applied at an early stage during compressor design to evaluate the susceptibility to this kind of blade vibration.

Experimental Investigations Into Pressure Field in Tip Clearance of Shrouded Rotor Blades

2002 ◽  
Author(s):  
Krzysztof Kosowski ◽  
Marian Piwowarski
Keyword(s):  
Pressure Distribution ◽  
Pressure Pulsation ◽  
Pressure Field ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Pressure Pulsations ◽  
Blade Tip ◽  
Shrouded Rotor ◽  
Blade Tip Clearance

The experimental investigations into the pressure field in the shroud clearance were performed on a one-stage air model turbine of impulse type. Measurements of pressure distribution were carried out for different rotor eccentricities, different values of axial gap and of rotor-stator misalignment, different rotor speeds and different turbine load. The experimental investigations proved that: a) the pressure in the blade tip clearance is not stationary but it pulsates, b) the effect of nozzle trailing edge can be observed in the blade shroud clearance, c) for a given turbine output, the rotor-stator eccentricity and rotor-stator misalignment appear the most important parameters influencing the pressure distribution in the shroud clearance. Aiming to investigate the pressure pulsation transmission through the leakage flow in the blade shroud clearances, pulsations of different amplitudes and frequencies were excited in the turbine inlet duct and corresponding changes of pressure were measured along the shroud width, followed by appropriate harmonic analysis. The investigations were performed for forced pulsations with frequencies ranging from 1Hz to 8 Hz. In all the examined cases, the frequency of pressure pulsations remained unchanged, while the amplitude of the pulsation decreased gradually along the tip clearance. The frequency of these pressure pulsations in the tip clearance was equal to the frequency of the pressure pulsation at the turbine stage inlet and to the frequency of pressure pulsation at the turbine flow passage’s exit.

Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part II — Wake–Tip Clearance Vortex Interaction

2007 ◽  
Author(s):  
Ronald Mailach ◽  
Ingolf Lehmann ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Pressure Sensors ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Lower Velocity ◽  
Blade Row ◽  
Blade Tip ◽  
Tip Clearance Vortex

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part II of the paper the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes the tip clearance vortices are separated into different segments. Along the mean vortex trajectory these parts can be characterised by alternating patches of higher and lower velocity and flow turning or subsequent counterrotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

Experimental Investigation of the Flow in the Pipe Diffuser of a Centrifugal Compressor Stage Under Selected Parameter Variations

2009 ◽  
Author(s):  
Uwe Zachau ◽  
Reinhard Niehuis ◽  
Herwart Hoenen ◽  
David C. Wisler
Keyword(s):  
Centrifugal Compressor ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Facility ◽  
Experimental Investigations ◽  
Pressure Side ◽  
Compressor Stage ◽  
Diffuser Flow ◽  
Parameter Variations

On a centrifugal compressor test facility various experimental investigations have been carried out contributing a valuable gain in knowledge on the fundamental flow physics within passage type diffusers. An extensive measurement series using various steady, unsteady and laser optical measurement techniques has been performed to detect the unsteady, highly three dimensional diffuser flow under various realistic operating conditions. Zachau et al. [1] presented the test facility and the results gathered under nominal conditions. As a follow-up the results of investigated parameter variations are now presented, covering bleed variations, impeller tip clearance and impeller-diffuser misalignment studies. The data is compared to the benchmark created from the nominal baseline data sets and evaluated with respect to the compressor stage performance. Zachau et al. [1] found that under nominal conditions the flow in the pipe diffuser separates on the pressure side in the first half of the pipe. In the last 30% of the pipe hardly any deceleration of the flow takes place. From this, special attention is given to the investigated parameter variations regarding a first proposal for a diffuser design change, which consists in shortening the diffuser. The results for each parameter variation are evaluated in detail in direct comparison to the nominal baseline configuration underlining the conclusion made earlier that the diffuser flow always separates on the pressure side with negligible deceleration in the last third of the diffusing pipe.

scholarly journals Blade by Blade Tip Clearance Measurement

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
A. G. Sheard
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Measurement System ◽  
Measurement Techniques ◽  
Tip Clearance ◽  
Initial Development ◽  
Real World Applications ◽  
Blade Tip ◽  
Capacitance Probe ◽  
Blade Tip Clearance

This paper describes a capacitance-based tip clearance measurement system which engineers have used in the most demanding turbine test applications. The capacitance probe has survived extended use in a major European gas turbine manufacturer's high-temperature demonstrator unit, where it functioned reliably at a turbine entry temperature in excess of 1800 degrees Kelvin. This paper explores blade by blade tip clearance measurement techniques and examines probe performance under laboratory conditions in support of high-temperature installations. The paper outlines the blade by blade tip clearance measurement technique and describes the experimental facility used to study tip clearance measurement. The paper also fully describes the method used to calibrate the measurement system in order to ascertain measurement accuracy. The paper clarifies how the practical problems were overcome associated with making blade by blade tip clearance measurements in both compressor and turbine environments. Since its initial development, gas turbine development programmes have routinely used the clearance measurement system. The inherent robustness of the system has resulted in reliable in-service measurement of clearance in real world applications.

scholarly journals Mounting Troubles

2011 ◽  
Vol 133 (03) ◽  
pp. 46-49
Author(s):  
Lee S. Langston
Keyword(s):  
Fuel Consumption ◽  
Compressor Blade ◽  
Tip Clearance ◽  
Jet Engines ◽  
Successful Resolution ◽  
Blade Tip ◽  
Leading Edges ◽  
The 1960S ◽  
Blade Tip Clearance

This article analyzes the problems encountered in developing the first jumbo jet, the Boeing 747. In the 1960s, the jumbo jet—a wide-body aircraft with two aisles and up to 10 seats per row—was the logical next step in the progression of the airliner. For the Pratt & Whitney JT9D, which was causing the 747 trouble, the engine skin casing was both bending and ovalizing—exhibiting non-circular distortion—under thrust loading that could be as high as 43,500 pounds on takeoff. The ovalizing distortion resulted in turbine and compressor blade rubbing against the interior of the engine case and necessitated power-robbing increases in blade tip clearance gaps. The result was a serious reduction in thrust, and increased fuel consumption as much as 7 percent above guaranteed rates. Boeing chose to mount the JT9D engines well forward of the 747 wing leading edges. The successful resolution of ovalization problems encountered in mounting the JT9D to the first Boeing 747s has provided guidance for future installations of large fan commercial jet engines.

Blade Tip Clearance Flow and Compressor NSV: The Jet Core Feedback Theory as the Coupling Mechanism

2007 ◽  
Author(s):  
Jean Thomassin ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
High Speed ◽  
Feedback Mechanism ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Coupling Mechanism ◽  
Blade Vibration ◽  
Potential Core ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip

This paper investigates the role of tip clearance flow in the occurrence of non-synchronous vibrations (NSV) observed in the first axial rotor of a high-speed high-pressure compressor (HPC) in an aero-engine. NSV is an aero-elastic phenomenon where the rotor blades vibrate at non-integral multiples of the shaft rotational frequencies in operating regimes where classical flutter is not known to occur. A physical mechanism to explain the NSV phenomenon is proposed based on the blade tip trailing edge impinging jet like flow, and a novel theory based on the acoustic feedback in the jet potential core. The theory suggests that the critical jet velocity, which brings a jet impinging on a rigid structure to resonance, is reduced to the velocities observed in the blade tip secondary flow when the jet impinges on a flexible structure. The feedback mechanism is then an acoustic wave traveling backward in the jet potential core, and this is experimentally demonstrated. A model is proposed to predict the critical tip speed at which NSV can occur. The model also addresses several unexplained phenomena, or missing links, which are essential to connect tip clearance flow unsteadiness to NSV. These are the pressure level, the pitch-based reduced frequency, and the observed step changes in blade vibration and mode shape. The model is verified using two different rotors that exhibited NSV.

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