Study of the influence of the characteristics of a steam turbine blade surface on the error of an optical-electronic chord length control system

The influence of surface characteristics of the working blade of steam turbine low-pressure cylinder and parameters of optoelectronic system elements on the chord length control error during turbine rotor barring is investigated. Experimental studies show that the spectral coefficient of diffuse reflection of the working blade surface in different sections of the surface of a worn and new blade can vary from 0.03 to 0.18, and thus confirm the need to take these changes into account in the system design. The algorithm for determining the chord length is improved, the algorithm includes the operation of morphological closure with a structural element in the form of a circle with a diameter equal to a quarter of the width of the working blade image, and allows for removal of pulse noise from the video camera. Studies on a computer model using the improved algorithm demonstrate that the signal-to-noise ratio at the input of the video probe receiver should not exceed 15 dB. Experimental studies of the system model in statics with a worn working blade with a chord length of 102.4 mm reveal that the standard deviation of the length estimates does not exceed 0.19 mm, which confirms the effectiveness of using the proposed version of the algorithm.

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