The Operational Technique of Increasing Service Life Time of the Major Components of the Fighter Aircraft Engine Rotors

The operational technique for the major components of the fighter aircraft engine rotors has been introduced basing on the real conditions of their cyclic loading in each flight or ground test and a priori information on their previous operation. It has been confirmed that the obtained technical solutions not only conform to the current methods of accounting for the depletion of the life cycle of the Afterburning Turbofan Engine (ATE) but also introduce additional opportunities to consider individual characteristics and conditions of their cyclic loading throughout the overall operating time. A method for estimating the depletion of the life cycle in accordance with the Total Accumulated Cycle (TAC) has been proposed. It allows us to compare the actual operating time of the ATE in hours and the accumulated value of cyclic damage to the engine and its major components (within the TAC parameter) during the previous operation.

An improved Jacobian-Torsor model for statistical variation solution in aero-engine rotors assembly

Rotor assembly is one of the core components of aero-engine, which basically consists of multistage revolving components. With the influence of parts’ manufacturing errors and practical assembly technology, assembly variations are unavoidable which will cause insecurity and unreliable of the whole engine. Statistical variation solution is a feasible means to analyze assembly precision. When using the three-dimensional variation analysis in rotor assembly, two key issues cannot be well solved, which involve the variation expression (the over-positioning problem of multiple datums) and the variation propagation (revolving characteristic of the rotors). To overcome the deficiency, extended Jacobian matrix and updated torsor equation were derived and unified, which eventually resulted in the improved Jacobian-Torsor model. This model can both provide rotation regulating mechanism by introducing the revolution joint, and characterize the interaction between essential mating features. Multistage rotational optimization of four-stage aero-engine rotors assembly has been performed to demonstrate this solution in statistical way. Results showed that the proposed model was applicable and conducive to precision prediction and analysis in design preliminary stage.

Validation of LCF Life of Turbine Rotor Assembly of a Turbo-Shaft Engine Through Cyclic Spin Test

Gas turbine rotors are high speed rotating components which operate under high temperatures. These turbine rotors undergo repeated cycles of low speeds to high speeds and therefore low stresses to high stresses which lead to low cycle fatigue failure. This low cycle fatigue leads to initiation of cracks at high stress areas like bolt holes, blade slots or disc bore. During design the life obtained through numerical methods is verified by cyclic spin tests. This particular paper talks about the spin testing of turbine rotor assembly of a turbo-shaft engine to validate its low cycle fatigue life obtained through analysis. These three stage turbine rotors were indigenised for cost savings. The life of the indigenously designed rotors were required to be the same as the turbine rotors being supplied by the engine OEM’s. Since the test rig which was used to validate the life of the rotors had a limitation of applying uniform temperatures, there was a need to develop a test schedule that simulates the operating conditions of the actual engine rotors. The work was carried out in two phases. In the first phase FEA tools were utilised to find out stress and strain levels of the turbine rotors by applying actual engine load conditions. Since rotor assembly was tested under uniform temperature in the test rig a combination of centrifugal load and temperature that would result in the same factor of safety levels of the rotors as in the actual engine conditions was arrived at in an iterative manner. Once the right combination was achieved the life of the engine rotors under test conditions was estimated numerically. In the second phase cyclic spin test was carried out on the turbine rotor assembly at equivalent load conditions. At regular intervals dimensional and NDT checks were carried out on the rotor assembly to find out crack initiation. The life of the rotor assembly which was estimated with the help of FE tool was validated through spin test.

Three-Dimensional Structural Evaluation of a Gas Turbine Engine Rotor

Engine rotors are one of the most critical components of a heavy duty industrial gas turbine engine, as it transfers mechanical energy from rotor blades to a generator for the production of electrical energy. In general, these are larger bolted rotors with complex geometries, which make analytical modeling of the rotor to determine its static, transient or dynamic behaviors difficult. For this purpose, powerful numerical analysis approaches, such as, the finite element method, in conjunction with high performance computers are being used to analyze the current rotor systems. The complexity in modeling bolted rotor behavior under various loadings, such as, airfoil, centrifugal and gravity loadings, including engine induced vibration is one of the main challenges of simulating the structural performance of an engine rotor. In addition, the internal structural temperature gradients that can be encountered in the transient state as a result of start-up and shutdown procedures are generally higher than those that occur in the steady-state and hence thermal shock is important factor to be considered relative to ordinary thermal stress. To address these issues, the current paper presents the steady-state & quasi-static analyses (to approximate transient responses) of two full 3-D industrial gas turbine engine rotors, SW501F & GE-7FA rotor, comprising of both compressor & turbine sections together. Full 3-D rotor analysis was carried out, since the 2-D axisymmetric model is inadequate to capture the complex geometries & out of plane behavior of the rotor. Both non-linear steady-state & transient analyses of a full gas turbine engine rotor was performed using the general purpose finite element analysis program ABAQUS. The paper presents in detail the FEA modeling technique, overall behavior of the full rotor under various loadings, as well as, the critical locations in the rotor with respect to its strength and life. The identification of these critical locations is needed to help with the repair of the existing rotors and to improve and extend the operational/service life of these rotors.