A Study of Multiple Techniques to Simulate Blade Out Event

Successful demonstration of safety of aircraft engines during extreme events such as Foreign Object Damage and Containment are mandatory for FAA (Federal Aviation Administration) certification. According to FAA every engine has to undergo fan blade out tests and engine has to contain this event without leading to major hazard to aircraft and loss of life. The fan blade out containment test involves the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact and which in turn can cause damage to the aircraft. The current trend in the industry is to minimize tests through analytical simulations and demonstrate compliance to regulations and flight-safety requirements. Accurate simulations of such events save significant effort, time and cost. This paper presents the various simulation techniques to demonstrate fan case containment when subjected to fan blade out event. The modeling is carried out with simplifications and assumptions to minimize problem size and maximizing the accuracy in simulation. Various simulation techniques analyzed in this study are used to assess the modeling approach and parameters influence on the event simulation. The effect of rotor imbalance on blade failure and blade kinetic energy are also studied in this paper. LS-DYNA has the capability to perform implicit and explicit methods which is used to analyze the blade out event in this study.

The Blade Releasing Method for Test of Engine Casing Containment

When designing aviation gas turbine engines, check for fan casing penetrability is envisaged by normative documents. Modern calculated methods of forecasting casing containment capabilities use a set of a priori limitations, and these methods can not give a reliable assessment of this event. Experimental checkup of casing containment capability of aero engines is one of the most important tasks with respect to ensuring flight safety. When the engine blade is released in the aircraft, serious damages of the frame may occur, as well as engine mount release, fire, e.t.c., which cause catastrophic effects. To decrease expenses for the engine operational development and to solve the mentioned problems it is purposeful to carry out stage-by-stage tests of the engine components on a spin rig. One of these problems, namely, localization of blade rupture inside the engine casing, is solved by carrying out fan casing containment test on the spin rig. The blade releasing method is proposed for casing containment test on the spin rig. It’s necessary to make calculations to determine conditions of the controlled blade-off under effect from centrifugal loads at a specified speed. The developed blade releasing method at tests has the following stages: 1. The computational modelling performed to determine the parameters of the cropped section of the blade: the dimensions of the edges and central part of the blade for achieving of the minimal safety factor. 2. Cutting of the blade. 3. Balancing of a rotor with the undercut blade. 4. The casing with the working wheel is set on the spin rig. 5. Testing: 5.1. The specified speed of rotation of a rotor achieved. 5.2. The central part of the undercut blade section heated up. The safety factor of the blade decreases when the temperature rises. The central part of the undercut blade section extended at the rise of the temperature and centrifugal force transferred to the edges of the blade. The blade edges broke. Then centrifugal force transferred to the central part of the blade and the blade released on the specified speed. 5.3. The analysis of the test results. The results of calculations of the rotor blade release conditions using finite element analysis and fan casing containment test are presented in this paper.

Cast-in-Pair Blade Release Simulation and Comparison to Experiments With a Full Scale Rig

This paper deals with the simulation of a Low Pressure Turbine (LPT) blade release and the subsequent impact onto the casing. The blade design is a cast-in-pair novel configuration where two airfoils are attached to a single firtree. This design solution was implemented in the first stage of the Low Pressure Turbine of the TP400-D6 engine using a directionally solidified M247 alloy. Due to the novelty of the design configuration a case containment test was carried out for certification versus CS-E810 EASA airworthiness requirement. The test was full scale reproducing engine-operating temperature and red line rotational speed. The objective of the present work is the simulation of the blade release failure event including the interaction with the trailing blades and the severe impact onto the casing. The simulation is compared and validated against the results of the full-scale rig. Material behaviour under impact working condition is characterised through Hopkinson bar tests, ballistic tests and triaxial traction tests. Johnson-Cook constitutive and failure material models are generated for the blade casting, the case forge material and the shroud seal segment. This material model is a temperature and strain-rate dependant flow stress model. Containment simulation is carried out with LS-DYNA implicit/explicit solver. Simulation work includes meshing and boundary conditions effects on model fidelity. Case damage progression is linked to each of the different airfoil portions as contact occurs. The friction contribution to the case and blades interface and to the case final form is also revised. In addition, the importance of the trailing blades and the interaction with the released blade is assessed. Interaction effect comprises both the resulting damage between airfoils and the change in primary release trajectory. Finally, simulation results are compared to the full scale rig results. Case-impacted final geometry and internal energy from simulation are checked against test evidences.