Numerical and experimental criterion of gas turbine engine hull dynamic strength in case of open rotor blade out

Аuthors

Ryabov A. A.^1*, Romanov V. I.^1**, Kukanov S. S.^2***, Shmotin Y. N.^3****, Gabov D. V.^2*****

1. Sarov Engineering Center, Science and technology park "Sarov", 3, Parkovaya str., Satis, Nizhny Novgorod region, 607328, Russia
2. United Engine Corporation “Saturn”, 163, Lenin av., Rybinsk, Yaroslavl region, 152903, Russia
3. United engine corporation (UEC), 16, Budyonny avenue, Moscow, 105118, Russia

*e-mail: alex.ryabov@saec.ru
**e-mail: romanov@saec.ru
***e-mail: kukanov@saec.ru
****e-mail: yuri.shmotin@npo-saturn.ru
*****e-mail: gabov_dv@npo-saturn.int

Abstract

The solution of safety issues of gas turbine engines (GTE) for modern and advanced passenger aircrafts in emergency situations is a very important task of improving the reliability of aeronautical engineering. One of the possible and most severe accidents is a fan blade out of a running engine. In this case, the broken blade hits the engine hull at high velocity and may rupture it, which is impermissible. Numerical study of the blade and engine hull collision [1— 8, 11, 12] shows that the process of dynamic deformation takes place under complex stress conditions and characterized by high velocities and strain levels. Thus, we need reliable dynamic strength criterions to validate the engines impact resistance. When the blade hits the engine hull, its body deformation is local. Hence, to develop the dynamic strength criteria, we can examine a collision of rectangular plates, where local deformation is very similar to that of a real engine in terms of a stress state, deformation levels and rates. The aim of this work is to investigate numerically the impact deformation and develop computational and experimental criterions of impact resistance.

In this work, we examine the mutual collision of a flying rectangular titanium plate of a constant thickness with a quiescent aluminum target plate of a constant thickness. The target size was sel ected so as to eliminate boundary conditions impact on local deformations. The studies are carried out in velocity ranges V₀ ~ 160...239 m/s at different impact angles: φ = 90° (normal impact),φ = 60° and φ = 45°.

Experimental studies show that in the case of normal impact, at the impact velocity of V₀ = 160,8 m/s, the target is deformed, but not ruptured. At the impact velocity of V₀ = 195,0 м/с, the flying plate ruptures the target and gets stuck in it. For the impact angle of φ = = 60°, for two cases of similar impact velocities: V₀ = = 199,6 m/s and V₀ = 201,3 m/s, the target did not penetrate in the first case and completely penetrated in the second case. At the impact angle of φ = 45° in the range of velocities V₀ = 210,8...218,8 m/s the target did not penetrate.

The problem of numerical simulation of is formulated in Lagrangian representation, the equation of motion is based on the principle of virtual operation. The equations of state are recorded in the form of the flow theory with kinematic and isotropic hardening. The mutual collision of the plates is investigated numerically by solving a non-stationary contact problem with variable boundaries. Numerical simulation is based on the finite element method and explicit time integration scheme, implemented in LS-DYNA [9].

The results of numerical simulations and their comparison to the experimental data show that the duration of the active deformation processes equals t_a = 50...150 µs for all cases of loading V₀ = 160...239 m/s in the range of angles φ = 45°...90°. Maximum deformation rates develop at the impact side and reach ε = (5...7) 10³ с-1. During the mutual collision, in all cases the stress state close to triaxial compression П ~ —1,0 [10]) at the target impact side occurs, with biaxial extension П ~ +0,80 [10]) on the opposiste side.

The flying plate kinetic energy is not the criterion of target rupturing. With equal or similar kinetic energy of the hitting plate, the target destruction is largely determined by the conditions of the initial contact interaction («perimeter», «line», «point») that affecting the localization of the target deformations.

In all considered cases the target destruction starts fr om the impact side and is characterized by the local shear (cut) in the contact zone of the plate and the target. The deformation intensity stands for the measure of this shear and can be considered as the dynamic strength criterion. For the considered material, we determine the design and experimental criterion of dynamic strength as ε_i= 24...25%.

Keywords:

gas-turbine engine, fan blade out, simulation experiment, finite element method, finite elements method, dynamic stress analysis, criterion of dynamic resistance

References

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