Aerospace Technic and Technology

One of the characteristic features of high loaded low-pressure turbine (LPT) with a low flow coefficient is the high-level flow deflection in the blade rows, which have sufficiently thin and strongly curved cross-section profiles. Such profiles are very sensitive to off-design flow angles, especially to positive incidence. Therefore, the effectiveness of a high loaded LPT strongly depends on the working conditions. At the same time, for various reasons, in the process of research tests or operating the engine, the operating conditions may differ greatly from the design ones. Therefore, the creation of a robust LPT design is an actual task. The article considers the computational approbation of the method of increasing the resistance to large off-design angles of attack of vane and blade rows of the intermediate stage of a high loaded LPT of an experimental engine by changing the shape of the leading edges. The turbine was previously tested as part of a full-scale engine, where it was determined that the operating conditions of the LPT and its efficiency are significantly different from the calculated ones. Numerical (CFD) analysis of the flow showed that one of the reasons for the low efficiency is the large angles of attack on the vane and blade rows of the second stage, which lead to the flow separation and an increase of the energy losses coefficients at final. The modernization of the profiles was carried out by reducing the radius and a local increase of the leading edges wedge angle without changing the basic profiles. According to the calculation results, it was allowed to significantly improve the stream. The intensity of the flow deceleration behind the shock wave at the point of transition from the circumference of the edge to the suction surface was reduced, this made it possible to eliminate or reduce the intensity of the flow separation in the vane row and significantly reduce the energy losses coefficient. A more favorable flow was also achieved in the blade row, where a slight decrease in the losses coefficient was also obtained. As a result, the efficiency of the stage and the whole LPT was increased at the off-design operating conditions. This approach can be recommended both to increase the efficiency of the turbine at the experimental development, and when designing new turbines to increase their robustness.

low pressure turbine; high loaded stage; incidence; flow separation; losses; robustness

Harvey, N. W., Cox, J. C., Schulte, V., Howell, R., Hodson, H. P. The Role of Research in the Aerodynamic Design of an Advanced Low-Pressure Turbine. Proc. Instn. Mech. Engr., 1999, vol. 213, Part A.

De Poli, P., Frola, G., Gallizio, M., Fattore, L., Mattone, M. Multi-disciplinary Integration and Robustness Evaluation Applied to Low Pressure Turbine Casing Design. ASME Pap. GT2006-90464.

Bertini, F., Credi, M., Marconcini, M., Giovannini, M. Path Towards the Aerodynamic Robust Design of Low Pressure Tutbines. ASME Pap, GT2012-69456.

Horlock, J. H. Axial flow turbines: Fluid mechanics and Thermodynamics. London, Butterworths, 1966. 286 p. (Russ. ed.: Khorlok, Dzh. Kh. Osevye turbiny: gazovaya dinamka i termodinamika. Moscow, Mashinostroenie Publ., 1972. 284 p.).

Vázquez, R., Cadrecha, D., Torre, D., Vázquez, R. High stage loading low pressure turbine. A new proposal for an efficiency chart. ASME Pap, GT2003-38374.

Deych, M. E., Filippov, G. A., Lazarev, L. Ya. Atlas profiley reshetok osevykh turbin [Atlas of axial flow turbine lattice of profiles]. Moscow, Mashinostroenie Publ., 1965. 96 p. (In Russian).

Venediktov, V. D., Granovskiy, A. V., Karelin, A. M., Kolesov, A. N., Mukhtarov, M. Kh. Atlas eksperimental'nykh kharakteristik ploskikh reshetok okhlazhdaemykh gazovykh turbin [Atlas of experimental characteristics of flat lattices of cooled gas turbines]. Moscow, TsIAM, 1990. 393 p. (In Russian).

Mamaev, B. I., Klebanov, A. G. Profil'nye poteri v turbinnoy reshetke [Profile losses in the turbine lattice]. Teploenergetika, 1970, no. 6, pp. 38-42. (In Russian).

Khomylev, S. A., Reznik, S. B., Ershov, S. V. Chislennoe issledovanie obtekaniya turbinnykh reshetok profiley: Chast' 2 Issledovanie kharakteristik vysokonagruzhennykh reshetok [Numerical study of flow in turbine profiles lattices: Part 2 Investigation of the characteristics of high-loaded lattices]. Aviatsionno-kosmicheskaya tekhnika i tekhnologiya Publ. – Aerospace technic and technology, 2008, no. 8 (55), pp. 46-50. (In Russian).

Khomylev, S. A., Rudenko, V. T., Lyusina, A. V. Chislennoe issledovanie vliya-niya formy peredney kromki na effektivnost' turbinnoy reshetki [Numerical study of the influence of the leading edge shape on the efficiency of a turbine blade]. Vіsnik Natsіonal'nogo tekhnіchnogo unіversitetu “Kharkіvs'kiy polіtekh-nіchniy іnstitut”, zb. nauk. pr. [Bulletin of the National Technical University "KhPI"]. Khar'kov, 2011, no. 5, pp. 45-50. (In Russian).

Khomylev, S. A., Reznik, S. B., Ershov, S. V. Rezul'taty aerodinamicheskogo usovershenstvovaniya profilya vysokonagruzhennoy turbinnoy reshetki [Results of the aerodynamic improvement of the profile of a high-loaded turbine blade]. Aviatsionno-kosmicheskaya tekhnika i tekhnologiya – Aerospace technic and technology, 2010, no. 7 (74), pp. 57-61. (In Russian).

Ershov, S. V. Programmnyy kompleks dlya rasche-ta prostranstvennykh techeniy vyazkogo gaza v re-shetkakh turbomashin [A software package for calculating the three dimensional flow of a viscous gas in turbomachine lattices]. Problemy mashinostroeniya, 2012, vol. 15, no. 34, pp. 52- 60. (In Russian).

Menter, F. R. Two-equation eddy viscosity turbulence models for engineering applications. AIAA J., 1994, vol. 32, no. 11, pp. 1299–1310.

Karelin, A. M. Postroenie reshetki turbinnykh profiley na osnove ratsional'nykh parametricheskikh krivykh. Lopatochnye mashiny i struynye apparaty [Construction of the turbine profile lattice on the basis of rational parametric curves. Blade machines and jet apparatus], Moscow, Trudy TsIAM, 1989, vol. 9, no. 1234, pp. 79-89. (In Russian).

Nguen, A. K., Lapshin, K. L. Kharakteristiki i struktura potoka turbinnoy stupeni s otritsatel'nym gradientom stepeni reaktivnosti [Characteristics and structure of the flow in a turbine stage with a negative gradient of the degree of reactivity] Nauchno-tekhnicheskie vedomosti SPbGPU, 2016, no. 2 (243), pp. 163-173. (In Russian).