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1

Non-uniformity of the combustor exit flow temperature in front of the gas turbine

Błachnio J., Pawlak W.

Acta Mechanica et Automatica

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2014

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Vol. 8, no. 4

209--213

EN

Various types of damages to gas-turbine components, in particular to turbine blades, may occur in the course of gas turbine operation. The paper has been intended to discuss different forms of damages to the blades due to non-uniformity of the exit flow temperature. It has been shown that the overheating of blade material and thermal fatigue are the most common reasons for these damages. The paper presents results from numerical experiments with use of the computer model of the aero jet engine designed for simulations. The model has been purposefully modified to take account of the assumed non-homogeneity of the temperature field within the working agent at the turbine intake. It turned out that such non-homogeneity substantially affects dynamic and static properties of the engine considered as an object of control since it leads to a lag of the acceleration time and to increase in fuel consumption. The summarized simulation results demonstrate that the foregoing properties of a jet engine are subject to considerable deterioration in pace with gradual increase of the assumed non-homogeneity of the temperature field. The simulations made it possible to find out that variations of the temperature field nonhomogeneity within the working agent at the turbine intake lead to huge fluctuation of the turbine rpm for the idle run.

2

The assessment of changes in the microstructure of a gas turbine blade with a non - destructive thermographic method

Kułaszka A., Błachnio J., Zasada D., Jóźwik P.

Journal of KONES

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2012

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Vol. 19, No. 2

271-281

EN

Diagnostic methods applied nowadays to examine condition of a gas turbine blade have been discussed in the Introduction section. What follows in the body of the paper is presentation of findings on the assessment of changes in the microstructure of a gas turbine blade with a non-destructive thermographic method. A laboratory experiment performed on new turbine rotor blades made of the EI 867WD alloy has been described. The experiment consisted in holding the blades at different temperatures in the exhaust-gas environment produced by an aircraft engine supplied with jet fuel. The pulsed thermography method has been used to determine and analyse the temperature distribution upon the examined area while cooling-down after the earlier uniform warming it up with a heat pulse. Diffusion and effusion of heat in the alloy have been examined. Both phenomena are determined with thermal properties and other physical properties such as size, shape, weight, structure, chemical composition, thickness of the protective coating of the blade. Examination of the microstructure of the blade material has shown the increased thickness of the coating, grain size, and in particular disadvantageous modification in the strengthening gamma' phase against temperature. Finding the relationship between parameters of thermal responses of blade materials to heat pulse against the average size of precipitates of the gamma' phase and thickness of the aluminium protective coating enables inferences on changes in the blade material's condition. With this relationship as the basis and knowing permissible changes to the microstructure one can determine the 'fit-for-use' and 'unfit-for-use' (i.e. serviceable and unserviceable) conditions of the blades. Assuming the material criterion, i.e. some disadvantageous change in the morphology of precipitates of the gamma' phase in the EI 867WD alloy under examination, the 'fit-for-use' (serviceability) thresholds for blades affected with different temperatures have been defined.

3

Zarys metody do oceny trwałości lotniczych napędów hydrostatycznych.

Ułanowicz L.

Zagadnienia Eksploatacji Maszyn

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2005

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Vol. 40, nr 4

45-62

PL

W artykule zaprezentowano metodę, w której szacowanie trwałości napędu hydrostatycznego prowadzi się wychodząc z dwóch punktów widzenia. Pierwszym jest ocena trwałości ograniczonej, w wyniku której określa się okres bezpiecznej trwałości. Drugim ocena trwałości monitorowanej oparta na wykorzystaniu systemu okresowo przeprowadzonych pomiarów procesu degradacji parametrów kontrolowanych napędu hydrostatycznego. Przebieg zmian parametrów kontrolowanych napędu hydrostatycznego traktowany jest jako proces losowy przebiegający pod oddziaływaniem czynników eksploatacyjnych. Trwałość ograniczona związana jest z osiągnięciem przez parametr kontrolowany napędu wartości dopuszczalnej. Trwałość monitorowana związana jest z procesem zmian parametru decydującego o stanie technicznym napędu hydrostatycznego oraz okresowością jego kontroli. Określono związek tolerancji uprzedzających parametru kontrolowanego, będącej zbiorem wartości parametrów zawartych między poziomami dopuszczalnym i granicznym, z okresowością sprawdzeń, przy zapewnieniu zadanego poziomu nieuszkadzalności. Wyznaczono rozkłady charakterystyk zmian parametrów napędu dla wybranego czasu badań i na tej podstawie ustalano parametry rozkładu czasu poprawnej pracy. W tym przypadku model trwałościowy napędu jest specyficznym rozkładem zmiennej losowej, w którym wariancja zależy od czasu. Dla oszacowania trwałości napędu wyznaczono funkcję gęstości prawdopodobieństwa, wartość oczekiwaną m eta(t) i średnie odchylenia kwadratowe sigma eta(t) parametru kontrolowanego. Zaprezentowano przykład oszacowania trwałości ograniczonej i trwałości monitorowanej pomp hydraulicznych NP-34M-IT z samolotu Su-22 i wzmacniaczy hydraulicznych BU-51MS z samolotu MiG-21.

EN

The paper has been intended to introduce a method of estimating life of a hydrostatic drive. The method offers two standpoints to start with: one resolves itself to the limited-life evaluation to result then in the safe-life determination, whereas the second one provides the monitored-life evaluation based on a system to periodically measure degradation of controlled parameters of hydrostatic drives and assemblies thereof. The course of changes in controlled parameters of the hydrostatic drive is treated as a random process going on due to operational/maintenance factors. The limited life is directly related to the controlled parameter's reaching the admissible value, whereas the monitored life - to the process of changes in the parameter decisive to the health/maintenance status of the hydrostatic drive and periodicity of inspections thereof. What has been determined furthermore is a relationship between the controlled parameter and the periodicity of checks, i.e. the relationship that constitutes a set of values of this parameter, enclosed between the admissible and boundary limits, with some pre-set level of fail-safety provided. Distributions of characteristics of changes in the parameters of the drive for some selected testing time interval have been found to give grounds for finding parameters of correct-running time distribution. Such being the case, a specific random-variable distribution constitutes a life model, within which variance is time-dependent. To estimate the drive's life, we have found the probability density function, the expected value m eta(t) and mean square deviations sigma eta(t) of the controlled parameter. Examples of how to find estimates on both the limited and monitored lives for hydraulic pumps NP-34M-IT of the Su-22 and the control amplifier BU-51MS of the MiG-21 have been presented.