Research On Radiation Temperature Measurement Methods Of Gas Turbine Blade

Gas turbines exhibit such advantages as lightweight,compact size,fast start-up and high degree of automation,for which they have been extensively applied in a variety of different military and civilian fields such as aerospace,shipbuilding and power generation.The most-preferred method of improving gas turbine power and efficiency is to increase the turbine inlet temperature.Nevertheless,this would lead to an increase in the thermal load applied to the various components of the turbine.Turbine blades are regarded as one of the most significant components which would be subject to the harshest working environment in the gas turbine.Turbine blades operate in an environment characterized by high temperature,high pressure,and high speed.Temperature is known as an important parameter as it can indicate the status of the turbine blades,which makes it necessary to perform on-line temperature measurement.Standing out from a variety of different methods,radiation thermometry has been commonly used due to its fast response,wide temperature range,and resistance to temperature interference.However,since the target in a typical turbine is surrounded by a hemisphere of potentially higher or lower effective temperature than the target itself,the radiation from the surrounding environment will lead to a non-negligible error when the temperature of the blade is measured using this type of thermometer.Therefore,the focus and sticking point of research lies in how to develop an effective method to analyze and rectify the error.The error caused by the reflected radiation of the hot parts of the turbine is not negligible.However,the existing methods used to construct the reflected radiation model are not matching with the complicated environment of actual temperature measurement,which gives rise to the pressing need to find a solution to this problem.When measuring the turbine blade temperature with single-wavelength or ratio pyrometer,an effective method to rectifying the reflected radiation has yet to be proposed.The current approach to data processing of multispectral radiation thermometry is incapable to ensure accuracy in describing the temperature characteristics exhibited by the turbine blade,which could result in a significant error.Therefore,a suitable data processing method was proposed in this paper to resolve this problem.The main content of this paper titled "Research on Radiation Temperature Measurement Methods of Gas Turbine Blade" involves the following points:(1)Research into the radiation characteristics of environment for the temperature measurement of turbine blade.The existing method to construct the radiation reflection model fails to match the complicated environment of actual temperature measurement,in consideration of which a method based on the triangular elements division and the double contour integral was proposed.Firstly,the surface of the turbine blades was divided by the triangular elements to construct the discretization analysis model.Secondly,the double contour integral method was used to calculate the view factor,and the reflected radiation model was constructed to facilitate the calculation of radiation heat transfer between the hot parts and the temperature measurement target.The finite volume method based on finite element method was applied to perform simulation of temperature distribution for the rotor blade and guide vane of the gas turbine.Based on the reflected radiation model,an analysis was conducted of the influence exerted by reflected radiation on the temperature measurement of the rotor blade pressure surface.A study was performed on the method used to calculate the characteristics of high-temperature gas radiation.The statistical narrow-band correlation k-distribution model was applied to facilitate the calculation of the temperature measurement error caused by high-temperature gas,which provides a valuable reference for the selection of turbine blade radiation temperature.(2)Research on the approach to radiation measurement of turbine blades based on effective emissivity.There is a lack of effective methods of data processing for the reflected radiation to be corrected at the time of measuring the temperature of turbine blade with single wavelength or ratio pyrometer.A single wavelength and a colorimetric temperature measurement method based on effective emissivity were proposed.The effective emissivity was used to rectify the temperature measurement error caused by the reflected radiation of the hot parts.In the meantime,the complexity of data processing was reduced.An analysis was carried out of the influence exerted by the turbine blades relative position and wavelength selection on the calculation of the effective emissivity and the temperature measurement error.As demonstrated by the experimental results,the proposed method based on the calculation of effective emissivity is capable of reducing the temperature measurement error caused by reflected radiation and improving the accuracy of measurement for the target with high-temperature background.(3)Research on the multispectral radiation temperature measurement of turbine blades.The existing methods of multispectral data processing are incapable to ensure accuracy in describing the characteristics of the ambient environment,which could result in a significant measurement error.A study was performed of the emissivity characteristics exhibited by the turbine blade.Besides,in combination with the reflected radiation model,a mathematical model of multispectral temperature measurement with the effects of reflected radiation taken into consideration was constructed.A method of multispectral data processing based on an improved quantum genetic algorithm was proposed,which could ensure effectiveness in reducing the multispectral temperature measurement error.In order to validate the effectiveness and adaptability of the proposed method,the temperature of three samples with different thermal barrier coating thickness was measured at a high temperature.(4)Turbine blade temperature measurement experiment and uncertainty analysis.The turbine blade temperature was measured online and the reflected radiation model was constructed according to the surrounding environment.Based on the calculation of effective emissivity,the data obtained from the single wavelength and colorimetric temperature measurement data was processed.Multispectral temperature measurement was performed to process the obtained multispectral data.Then,a comparison was drawn between the obtained results and the traditional method of data processing.As revealed by the experimental results,the proposed modeling method and single wavelength,colorimetric and multispectral data processing methods can be effective in improving the accuracy of temperature measurement for turbine blades.Moreover,an analysis was conducted of the uncertainty of the temperature measurement results obtained by using these three methods.