Florian Dreier

Interferometric Sensor System for Blade Vibration Measurements in Turbomachine Applications

In order to improve the safety, lifetime, and energy efficiency of turbomachines, the dynamic behavior of the rotor has to be analyzed. Blade vibrations have to be monitored during operation to optimize the rotor design and to validate numerical models. However, measuring the vibration amplitude and frequency of the blades is a challenging task for metrology, since the blades to be measured are rotating quickly, and noncontact measurements are demanded. To solve this problem, we present a measurement system consisting of four laser Doppler sensors that have been mounted around the circumference of the rotor. These sensors measure simultaneously and contactlessly the in-plane velocity and the out-of-plane position of laterally moving objects. By analyzing the variation of the blade tip velocities, the vibration amplitude and frequency of the blades were estimated. Blade vibration measurements down to amplitudes of only 20 μm in tangential direction have been carried out. We achieved a standard uncertainty of approximately 400 nm for these experiments.

Monitoring of Blade Vibrations and Tip Clearance at Non-Metallic Rotors in Turbo Machines

In order to improve the safety, the lifetime and the energy efficiency of turbo machines, the dynamic behaviour of the rotor has to be analysed and optimized. Thus, rotor unbalances, dynamic deformations and blade vibrations as well as blade tip clearance changes have to be monitored during operation to optimize the rotor design and to validate numerical models. However, these are great challenges for metrology, since small, robust and non-contact measurement techniques are required offering both micrometer accuracy and microsecond temporal resolution which is not fulfilled with currently available measurement techniques. To solve this problem, we present in this contribution a miniaturized fiberoptic laser Doppler probe that measures simultaneously the in-plane velocity and the out-of-plane position of laterally moving objects. Experiments have been carried out demonstrating the capability of this sensor to measure engine order blade vibrations instantaneously. Assuming a single engine order and a known vibration frequency, only one laser Doppler probe is necessary to measure the vibration amplitude. Thus, in contrast to blade tip timing, only one optical access to the blade tip is sufficient to measure the vibration amplitude. Furthermore, the novel sensor performs even at composite materials such as strongly absorbing carbon-fiber-reinforced plastic (CFRP) which became more popular in rotors of turbo machines.© 2012 ASME

Miniaturized nonincremental interferometric fiber-optic distance sensor for turning process monitoring

For in-process shape monitoring of rotating objects such as workpieces in a turning machine, contactless and compact sensors with high temporal resolution are necessary. For this challenging task, we developed a miniaturized and robust nonincremental interferometric fiber-optical distance sensor with dimensions of only 30×40×90 mm 3 , which enables attaching the sensor head directly to the mount of a turning tool bit. We present the results of in-process 3-D shape measurements of turning parts at a metal working lathe. To proof the accuracy of the measurement results, comparative measurements with tactile and optical sensors were performed. A maximal deviation between the different measurement methods of 2.2 μm was achieved for the determination of the mean height of a radial step.

Novel Dynamic Rotor and Blade Deformation and Vibration Monitoring Technique

Monitoring rotor deformations and vibrations dynamically is an important task for improving both the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently high measurement rate and high accuracy, which is hardly possible to achieve with currently available measurement techniques. To solve this problem, in this paper, we present a novel nonincremental interferometric optical sensor that measures simultaneously the in-plane velocity and the out-of-plane position of laterally moving objects with micrometer precision and concurrently with microsecond temporal resolution. It will be shown that this sensor exhibits the outstanding feature that its measurement uncertainty is generally independent of the object velocity, which enables precise deformation and vibration measurements also at high rotor speed. Moreover, this sensor does not require an in situ calibration and it allows a direct measurement of blade velocity variations in contrast to blade tip timing systems. For application under harsh environmental conditions such as high temperatures, a robust and miniaturized fiber-optic sensor setup was developed. To demonstrate the capability of this sensor, measurements of tip clearance changes and rotor blade vibrations at varying operating conditions of a transonic centrifugal compressor test rig at blade tip velocities up to 600 m/s are presented among others.

Messung dynamischer Deformationen und Schwingungen schnell drehender Rotoren

Zusammenfassung Zur Steigerung der Betriebssicherheit und der Energieeffizienz von Motoren und Turbomaschinen ist die genaue Kenntnis des dynamischen Verhaltens des Rotors im Betrieb erforderlich. Dies ist eine große Herausforderung für die Messtechnik, da die Form der schnell bewegten rauen Objektoberfläche mit Mikrosekunden Zeitauflösung und gleichzeitig mit Mikrometerpräzision erfasst werden muss. In diesem Beitrag wird dargestellt, wie diese anspruchsvolle Messaufgabe mit einem nicht-inkrementellen Laser-Doppler-Distanzsensor, der eine geschwindigkeitsunabhängige Messunsicherheit bietet, gelöst werden kann. Abstract In order to improve the safety and the energy efficiency of motors and turbo machines it is necessary to precisely know the dynamic behavior of the rotor during operation. This is a great challenge for metrology since it requires measuring the shape of the fast moving rough object surface with both high temporal resolution in the microsecond range and micrometer precision. This paper describes how this task can be solved employing a non-incremental laser Doppler distance sensor whose measurement uncertainty is independent of the object velocity.

Dynamic Rotor Deformation and Vibration Monitoring Using a Non‐Incremental Laser Doppler Distance Sensor

Monitoring rotor deformations and vibrations dynamically is an important task for improving the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently a high measurement rate and high accuracy, which can not be fulfilled by most commercially available sensors. To solve this problem, we developed a non‐incremental laser Doppler distance sensor (LDDS), which is able to measure simultaneously the in‐plane velocity and the out‐of‐plane position of moving rough solid objects with micrometer precision. In addition, this sensor concurrently offers a high temporal resolution in the microsecond range, because its position uncertainty is in principle independent of the object velocity in contrast to conventional distance sensors, which is a unique feature of the LDDS. Consequently, this novel sensor enables precise and dynamic in‐process deformation and vibration measurements ...

A Laser-Optical Sensor System for Simultaneous Tip Clearance and Vibration Monitoring of Compressor Rotor Blades

In order to improve the efficiency and increase the life-time of compressors and turbines, online monitoring of operating parameters is an essential tool. One aim is to predict critical events like stall or flutter by observing blade vibrations and deformations. Due to superior material properties ceramic, carbon-fiber and glass-fiber reinforced composite blades become more and more popular. Hence, conventional measurement systems like capacitive probes are not able to deliver the necessary precision or, in the worst case, are not able to measure at all. Therefore, we developed a fiber-coupled, laser-optical sensor, named laser Doppler distance sensor (LDDS), which overcomes this drawback. The sensor is able to resolve the circumferential blade tip velocity as well as the radial expansion of each blade. Moreover, conventional blade tip timing measurements are possible as well.Our aim is to provide a universal stall prediction and monitoring sensor system that is applicable to all types of blades.Copyright