Blade Tip Measurement Advanced Visualization Using a Three Dimensional Representation

Abstract

A microwave tip clearance sensor capable of measuring the hottest stages of industrial and aero gas turbines has been developed. This new microwave sensor has been integrated into a commercial package for online real-time monitoring of machine data. However, data analysis of large numbers of tip clearance probes makes standard industry graphic techniques cluttered. A method has been developed to reduce this data and visualize it in order to provide intuitive representations of the data from which a user can quickly draw the right conclusions about machine behavior. The main motivation for the development of a 3D graphical user interface is the density of information that can be shown to the user at one time. Tip clearance measurement is very data-rich, as every individual blade for each sensor mounted around the engine case is available. The result is that it may be difficult to find slight changes within hundreds of clearance trends. Only specialists with long experience in tip clearance measurement can synthesize all the data quickly enough using standard 2D plots. The 3D graphical user interface brings all of this data together to calculate the aggregated blade pattern, rotor positioning, and estimated case shape. All of these measurements are available to the user in a single visualization. Colors indicating alarm or clearance scale quickly draw attention to the most important data such as the minimum clearance point around the engine case where a rub may be likely to occur. This method is based about a case shape fitting algorithm that combines data from multiple sensors to make a case shape estimate based on fitting of a non-uniform rational B-spline (NURB). The scaling is also distorted in order to accentuate the graphics in a way that provides an intuitive understanding of the machine state. The method of applying this data accentuation is important so as to not be misleading. This innovative navigation interface presented in this paper capitalizes on modern advances in computer graphics to aid engineers and operators in understanding, access, monitoring, and analysis of tip clearance and air-gap measurements.