Calculation of heat-transfer coefficient on a turbine blade airfoil in abnormal modes

Аuthors

Shcherbakov M. A.^1*, Vorobyov D. A.^1**, Maslakov S. A.^2***, Ravikovich Y. A.^2****

1. Lyulka Desing Bureau, 13, Kasatkina str., Moscow, 129301, Russia
2. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: sherbakovma@mail.ru
**e-mail: den_vorobyow@mail.ru
***e-mail: smaslakov@yandex.ru
****e-mail: yurav@mai.ru, yr@mai.ru

Abstract

This article comprises results of studies aimed at defining the area of applicability of criterion dependences for obtaining the distribution of the heat-transfer coefficient on a rotor blade airfoil of small-size uncooled turbine. Design and abnormal turbine operating modes have been studied.
The value of heat-transfer coefficient on a specific section of the airfoil is calculated using known criterion dependences or by means of simulating the heat flux into the blade using ANSYS CFX.
The rotor blade was divided by mid-radius into two major sections in the network of calculating the heat-transfer coefficient using criterion dependences. The parameters of gas flow corresponding to average values of the parameters at these sections have been used for further calculations. Criterion dependences corresponding to the parameters of flow at the specific section were used during calculation for each section.
A 3D finite-element model was created in order to сarry out the calculation using ANSYS CFX. The number of elements was 21.8 million.
SST turbulence model was used and the following properties of a real gas were specified: composition and dependences of its properties on the temperature. The total pressure and total temperature were set for the inlet boundary condition and the static pressure was set for the outlet condition.
The following method was used for defining the local heat-transfer coefficient. Two calculations have been carried out for the model:

• for the first calculation all the walls are adiabatic;
• for the second one — the temperature is set for walls, where the heat-transfer coefficient should be defined.

The usage of these two methods for defining the heat-transfer coefficient demonstrates the difficulties connected with usage of criterion dependences.
Visualization of the flow patterns obtained from three-dimensional calculation in the program ANSYS CFX, revealed a complex system of vortices The obtained flow picture is unusual for turbine blades and this fact also influences significantly on the usage of criterion dependences. Due to the abovementioned «abnormal» factors, in most cases the values of heat-transfer coefficient obtained using criterion dependences are much higher than the ones calculated using ANSYS CFX. The results obtained using ANSYS CFX have higher degree of confidence, because they were obtained using a verified method.

Keywords:

heat-transfer coefficient, computational fluid dynamics, axial flow turbine, gas-turbine engine operating conditions

References

1. Lokai V.I., Bodunov M.N., Zhuikov V.V., Shchukin A.V. Teploperedacha v okhlazhdaemykh detalyakh gazoturbinnykh dvigatelei letatelnykh apparatov (Heat transfer in the cooled parts of aircraft gas turbine engines), Moscow, Mashinostroenie, 1986, 215 p.
   
2. ANSYS, Inc., ANSYS CFX-Solver Theory Guide, 2006, 312 p.
3. Shcherbakov M.A. Aviatsionno-kosmicheskaya tekhnika i tekhnologiya, 2011, no. 7 (84), pp. 165-169.
4. Avduevskii V.S., Galitseiskii B.M., Glebov G.A., Koshkin V.K. Osnovy teploperedachi v aviatsionnoi i raketno-kosmicheskoi tekhnike (Heat-transfer principles for aircraft and rocket-and-space equipment), Moscow, Mashinostroenie, 1992, 528 p.
5. Shcherbakov M.A., Yun A.A., Marchukov E.Yu., Krylov B.A. Vestnik Moskovskogo Aviatsionnogo Instituta, 2010, vol. 17, no. 5, pp.116-120.