Identification of boundary conditions for elements of the flow-through part of a turbine in a gas-turbine engine

Abstract In this work, massively parallel wall-modeled Large Eddy Simulations (LES) are conducted to simulate flow through a single stage power turbine sector of a gas-turbine engine under realistic operating conditions. The numerical framework in the current work uses finite volume based compressible CharLES solver that utilizes a moving Voronoi diagram based grid generation. To test grid sensitivity and evaluate the capability of the solver in predicting turbomachinery flows, three grids of varying resolution are used to simulate flow through the baseline gas-turbine under design operating conditions. After assessing the flow solution quality and establishing simulation parameters, LES simulations are conducted to investigate the performance of gas-turbine at off-design conditions. The conditions include the rotor design point at 100% speed, and off-design points at 75%, and 50% speeds subject to high temperatures from the combustor exit flow. The results showed that the internal flow becomes highly unsteady as the rotational speed of rotor deviates from the design point leading to reduced aerodynamic performance. This study demonstrates that the current framework is able to robustly simulate the unsteady flow in a three-dimensional moving rotor environment towards the design of variable speed gas-turbine engines for US Army Future Vertical Lift program.

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ТЕПЛООБМЕН ВО ВРАЩАЮЩЕМСЯ ГЛАДКОМ КРУГЛОМ КАНАЛЕ И ВЛИЯНИЕ НА ЕГО ИНТЕНСИВНОСТЬ ВИХРЕВОГО ТЕЧЕНИЯ

Aerospace technic and technology ◽

10.32620/aktt.2019.2.03 ◽

2019 ◽

pp. 30-35

Author(s):

Андрей Иванович Шманенко ◽

Сергей Иванович Сербин

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Boundary Conditions ◽

Gas Turbine ◽

Average Nusselt Number ◽

Gas Turbine Engine ◽

Turbine Engine ◽

Nusselt Numbers ◽

Static Channel ◽

Rotating Channel

The paper deals with the analysis of heat transfer intensity in a rotating smooth channel, which simulates a cooling channel of rotating blade of the gas turbine engine. A circle cross-section channel with a diameter of 6 mm and length of 80 mm was chosen as the base variant. The calculations of heat transfer in rotating and stationary channels were carried out, which allows estimating the influence of vortex flow on the intensity of heat transfer. Rotation of the channel was simulated by means of domain rotating. The rotation speed of the test channel is 7400 rev/min. Axis of rotation is at a distance of 0.49 m from the inlet section of the channel. Pressure and temperature were specified as inlet boundary conditions: 1040000 Pa and 733 K, respectively. The mass flow rate of 0.02 kg/s was specified as outlet boundary conditions. The computations were performed by solving the Reynolds-averaged Navier-Stokes equations (RANS method) using an SST (Shear Stress Transport) turbulence model. The air ideal gas was used as the working medium. The calculation was performed taking into consideration the Buoyancy effect. Verification of heat exchange calculation model in the rotary channel of the gas turbine engine rotor blade according to experimental data is carried out. The boundary conditions at the input and output of the channel were set in such a way that the flow parameters in the calculation corresponded to the experimental characteristics. The resulting numerical calculations of the temperature distribution and Nusselt Numbers are qualitatively and quantitatively consistent with the experiment. The distribution of Nusselt Numbers on the front and back walls for rotating and non-rotating channels, as well as the dependences of the relative tangential velocity on the relative channel length, were estimated. It has been shown that average Nusselt Number on the leading wall of the rotating channel is the same with the wall of the static channel, but detail Nu distribution over rotating leading wall undergoes considerable modification. Average Nusselt Number on the trailing wall of the rotating channel is higher than on the wall of the static channel, but the detail Nu distribution pattern on the rotating trailing wall generally follows the static result.

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