Investigations Into Electrostatic Monitoring Technology For On-line Condition Monitoring Of Large Heat Engines’ Gas Path Components

As the main source of faults of gas turbines, aeroengines and other large heat engines, gas path components cause so grave consequences, posing a serious threat to the safety of the equipments and the operators, that the realization of on-line monitoring of gas path components has become urgent in the engines’ development and using. In recent years, an electrostatic monitoring technology has been attracting more and more attentions. This method is based on monitoring the charged particles in the gas path, and could effectively overcome the shortcomings of the traditional methods of poor real-time performance and difficulty of providing early warnings. The electrostatic monitoring technology has exploited an important new way to meet the requirement of high reliability of large heat engines. Electrostatic sensors are the key devices in electrostatic monitoring. And the probe-type electrostatic sensors have the advantages of small structure, convenient installation, and flexible layout, that make them more suitable for the complex structures of large heat engines. Therefore, in this paper, we selected the probe-type electrostatic sensors as our research objects, and used theoretical analysis, finite element simulation, combined with experimental verification to carry out the research. The main research contents are as follows:1. A theoretical measurement model of the probe-type electrostatic sensors was deduced. Then a thorough analysis of the signal’s generation principle, the spatial static sensitivity, the spatial dynamic sensitivity, the spatial filtering effect and the frequency response characteristics was made, which laid an essential theoretical foundation for further researches.2. A three-dimensional finite element mode with high-fidelity of the sensor and the gas path was established. Then, the induced charge on the sensor’s probe was obtained by means of simulation. After that, the spatial static sensitivity and the spatial dynamic sensitivity were studied in details. On one hand, by using the combined function of Gauss function and Lorenz function, a fitting formula of the spatial static sensitivity was obtained. On the other hand, the whole distribution of the spatial dynamic sensitivity was obtained, and its influence factors were studied. Then, calculating models of both the spatial filtering effect and the frequency characteristics were deduced from the fitting formula, which realized the numerical simulation and the analysis of the influence factors.3. A kind of probe-type electrostatic sensors with a built-in amplifier circuit was designed and made, and an experiment system was set up. The experiments showed that it is feasible to use the probe-type electrostatic sensors in electrostatic monitoring, the methods of wavelet noise deduction,waveform restoration and feature extraction are practical, and the conclusions about the sensing properties in the previous theoretical and simulation studies were reliable.4. A single probe-type electrostatic sensor’s spatial dynamic sensitivity distributes extremely uneven in the space, which can be solved by using a planar array. The using of the Tikhonov regularization algorithm and the Landweber iterative regularization algorithm in progressing the planar array’s signals was realized by simulation. It showed that the regularization algorithms can greatly improve the planar array’s response ability in the gas path’s central area, and notably homogenize the distribution of the spatial dynamic sensitivity.