Modeling of Cyclic Life for Compressor Rotor of Gas Turbine Engine Taking Into Account Production Deviations

Abstract The regional aircraft with a turbofan gas turbine engine, created in Russia, is successfully operated in the world market. Further increase of the life and reduction of the cost of the life cycle are necessary to ensure the competitive advantages of the engine. One of the units limiting the engine life is the compressor rotor. The cyclic life of the rotor depends on many factors: the stress-strain state in critical zones, the life of the material under low-cycle loading, the regime of engine operation, production deviations (within tolerances), etc. In order to verify the influence of geometry deviations, the calculations of the model with nominal dimensions and the model with the most unfavorable geometric dimensions (worst cases) have been carried out. The obtained influence coefficients for geometric and weight tolerances are then used for probabilistic modeling of stresses in the critical zone. Rotor speed and gas loads on the blades for different flight missions and engine wear are determined from the corresponding aerodynamic calculations taking into account the actual flight cycles (takeoff, reduction, reverse) and are also used for stress recalculations. The subsequent calculation of the rotor cyclic life and the resource assessment is carried out taking into account the spread of the material low-cycle fatigue by probabilistic modeling of the rotor geometry and weight loads. A preliminary assessment of the coefficients of tolerances influence on stress in the critical zone can be used to select the optimal (in terms of life) tolerances at the design stage. Taking into account the actual geometric and weight parameters can allow estimating the stress and expected life of each manufactured rotor.

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Gas turbine engine disk cyclic life prediction

Journal of Aircraft ◽

10.2514/3.44456 ◽

1975 ◽

Vol 12 (4) ◽

pp. 360-365 ◽

Cited By ~ 12

Author(s):

S. A. Sattar ◽

C. V. Sundt

Keyword(s):

Gas Turbine ◽

Life Prediction ◽

Gas Turbine Engine ◽

Cyclic Life ◽

Turbine Engine

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Characterizing Compressor Rotor Unclamp in a Gas Turbine Engine

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2012-68882 ◽

2012 ◽

Cited By ~ 1

Author(s):

Cory Alban ◽

Masha Tolstykh ◽

Devin Hilty ◽

Andrew Bollman

Keyword(s):

Gas Turbine ◽

Robust Design ◽

Extended Period ◽

Gas Turbine Engine ◽

Tip Clearance ◽

Transient Condition ◽

Element Analysis ◽

Turbine Engine ◽

Compressor Rotor ◽

Secondary Air

In the aerospace industry, many gas turbine compressors rely on a tie bolt to mechanically hold together all rotating components in the compressor rotor. Maintaining this clamp load is essential to the performance of the engine. In the event of an unclamp, the engine will experience a reduction in tip clearance due to a change in rotational dynamics; increased temperatures and pressures in secondary air systems; and a decrease in critical component life. Accordingly, designers must be aware of the variables effecting compressor rotor clamp loads observed for component assembly and operational missions. During testing, an axial gas turbine engine unexpectedly experienced a compressor rotor unclamp which led to an increase in turbine temperature and front sump buffer air temperature and pressure. Further investigation revealed a thermal expansion mismatch between the tie bolt and inner gas path rim during a specific transient condition. Because of this thermal effect, the rotor will experience an unclamped condition which will result in ingesting compressor discharge air into the drum. The compressor rotor will remain unclamped until the engine is operated at a lower power setting or shut down for an extended period. This paper documents and explains the transient condition at which the engine experienced unclamp through review of test data, characterizes the design space around the tie bolt by using heat transfer and structural finite element analysis codes, and shows how robust design tools were used to find an optimized solution that eliminated the risk of thermally driven unclamp through robust design and assembly choices.

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The Use of Probabilistic Methods in Determining Turbine Disc Cyclic Life Uncertainty

Volume 3C: Heat Transfer ◽

10.1115/gt2013-94972 ◽

2013 ◽

Cited By ~ 1

Author(s):

David T. Williams ◽

Peter Smout ◽

Matteo Bianchi ◽

Martin B. Joinson

Keyword(s):

Gas Turbine ◽

Gas Turbine Engine ◽

Operating Conditions ◽

Probabilistic Methods ◽

Thermal Modelling ◽

Cyclic Life ◽

Turbine Engine ◽

Monitoring Process ◽

Turbine Disc ◽

Air System

Gas turbine discs are classified as Critical Parts since, in the event of their primary failure, high energy debris can be released potentially resulting in hazardous consequences to the aircraft. Critical Parts are monitored during the life cycle of a gas turbine engine to ensure that integrity is established and maintained. The predicted safe cyclic life for an engine disc must be calculated as part of this monitoring process. For calculating the life of a turbine disc, a thorough understanding of material properties, operating conditions, metal temperatures and the resultant stress field is required. These inputs are obtained variously by component or whole engine testing or by predictive methods. These methods evolve over time, and materials may need to be changed, so for legacy engine designs, it’s important that the monitoring process recognises this and reacts appropriately. This paper describes the application of probabilistic methods to determine the uncertainty of turbine disc cyclic life for a two shaft low by-pass ratio gas turbine engine designed originally in the 1950s but predicted to be in service to beyond 2030. For the subject gas turbine the original material used to manufacture the turbine discs was declared technically and commercially obsolete. A new material was selected, requiring a new cyclic life to be determined. Rather than run an engine test to measure temperatures of the new discs, an analytical approach was adopted involving air system and thermal modelling and robust design techniques. These included Monte-Carlo analyses and the linking of thermal modelling and cyclic lifing codes using optimisation tools. It is shown how a probabilistic approach to air system and thermal modelling has enabled: (i) a quantitative judgment on the value of an air system survey (ii) the uncertainty of thermal predictions and the resultant variation in life to be quantified. These methods and results have then been used to release a safe cyclic life of a turbine disc for operation in an aircraft without the use of a dedicated thermocouple test.

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