Abstract: A method for monitoring turbine blade vibrations comprises the step of transmitting a continuous wave of microwave energy toward a rotating row of blades. Each passage of an individual blade tip through the path of the continuous wave produces a signal indicative of the time at which each passage occurs. The signal is then monitored and analyzed to detect blade vibrations. The signal can be based on a standing wave or a reflected wave.

Abstract: A system and method are provided for monitoring synchronous blade vibration in a turbo-machine. At least three sensors capable of detecting the arrival of each blade are arranged about the cylinder which surrounds the tips of the blades. The location of the sensors is selected to minimize the influence of errors in the data. To this end, and to simplify the installation of the sensors into the cylinder, the sensors may be non-uniformly spaced. The location of each sensor for purposes of constructing Fourier transforms is determined using the arrival times at the blades at each sensor, expressed as a fraction of a rotor revolution. The transform matrix is constructed for a predetermined discrete set of M harmonics, so that M harmonics are analyzed simultaneously, the number of harmonics which can be simultaneously analyzed is related to the number of sensors used.

Abstract: A sensor produces a signal indicative of the actual arrival time of each turbine blade at the sensor. A first circuit is responsive to the sensor for producing digital data representing the actual arrival time of each blade at the sensor. A second circuit establishes expected arrival times for each blade at the sensor. A third circuit is responsive to the digital data for generating a plurality of data entries each representing the difference between the actual arrival time and the expected arrival time. A fourth circuit stores the data entries in a first string having a plurality of dummy entries at the beginning thereof and at the end thereof and inserts into the string space saver characters in the event that the data entry for a particular blade is not produced. A fifth circuit establishes a running average value, over a plurality of data entries, for each data entry. The running average value is representative of common mode vibration.

Abstract: A system for monitoring the vibration of a plurality of shrouded turbine blades carried by a rotor and configured in a row includes a stationary sensor for inducing eddy currents in each shroud segment as each shroud segment passes the sensor. A target is located on each shroud segment for causing variations in the induced eddy currents. The sensor is responsive to the induced eddy currents to produce an output signal containing information corresponding to the time of arrival of the target at the sensor. Another sensor is provided for producing a pulse once per rotor revolution. A blade vibration monitor is responsive to the output signal and the once per rotor revolution pulse to extract blade vibration information therefrom.

Abstract: The movement of a rotating part of a machine is monitored by deriving a signal representing the motion of the rotating part, at least temporarily storing the derived signal, and analyzing the stored signal, with temporary storage being performed only on portions of the signal derived during spaced time intervals during each revolution of the rotating part.

Abstract: A method of determining the untwist of turbine blades under dynamic conditions is comprised of the steps of producing a first pair of blade passing event signals in response to a blade tip's movement past a pair of fixed sensors. The signals comprising the first signal pair are compared to one another to establish a first differential value. Another data point containing blade vibrational information is produced. The first differential value and the other data point are evaluated to discriminate between blade untwist and synchronous vibration. Based on the magnitude of the blade untwist, inferences can be drawn regarding the status of the turbine blade lashing wires.

Abstract: An apparatus for detecting blade passing times includes a sensor for producing an input signal each time a blade passes the sensor. A zero crossing detector produces an output signal each time the input signal crosses a reference axis. A phase shifter shifts the phase of the input signal to produce a gating signal coinciding with the expected arrival time of the blade at the sensor. A gating device is responsive to the gating signal for conducting output signals which occur during the expected arrival time of the blade at the sensor.

Abstract: This invention relates to a method for measuring vibration in turbine blades and to an apparatus for mounting a sensing device for monitoring blade tip vibration in turbo-machinery. A guide tube is mounted through the cylinder covers of a turbine and extends to a position adjacent to the tip of the turbine blades. The guide tube is sealed at the cylinder covers and has a gate valve external of the turbine cylinder covers. A method for measuring vibration and turbine blades while the turbine is in full operation includes the steps of removing a dummy probe partially from the guide tube while the turbine is in operation. With the dummy probe still in a portion of the guide tube, the gate valve is closed.

Abstract: A nonsynchronous turbine blade vibration monitoring system is comprised of a maximum of two sensors circumferentially mounted along the turbine blade row for detecting the actual arrival times of the turbine blades at the sensors. Expected arrival times of the turbine blades at the sensors are determined and then compared to the actual arrival times in order to obtain turbine blade deflection data. Harmonic analysis is then performed on the blade deflection data to determine the level of vibration at each non-integral harmonic.

Abstract: System and method for characterizing the resonant responses of a plurality of rotating blades in a turbo machine. The system comprises a plurality of controllable fluid jets disposed about a blade row for exciting rotating blades with selectable frequencies of vibration. The sequential excitation of blades at a plurality of narrowly spaced frequencies and the simultaneous sensing of blade responses sufficiently resolves the resonant center frequencies and harmonics thereof in order to detect changes in characteristic blade resonances.