Modares Mechanical Engineering

Modares Mechanical Engineering

Numerical Simulation of the effect of passive control method by changing tip geometry on the performance of the axial turbine

Authors
sarallah Abbasi 1
Afshin Gholamalipoor 2
1 assistant professor, Arak University of Technology
2 دانشگاه صنعتی اراک
Abstract
Turbine tip leakage flow is one of the effective factors in reducing the efficiency and performance of axial turbines, which can also destroy turbine blades. Accordingly, it is important to identify and control the tip leakage flow. In this paper, we investigate the effect of tip clearance sizes and changes in tip shape as a passive control method on tip structure and total turbine flow performance. For this purpose, the flow loss in a two-stage axial turbine is performed using the CFX software. In order to ensure the accuracy of the results, the turbine performance curves were compared with the experimental results which good consistency have been observed. Considering the four cases for tip clearance size, the turbine performance curves and resulting pressure loss have been investigated. It was found that increasing the tip clearance size leads to reduced efficiency and increased losses in the axial turbine. In the following, we examine the application of the passive control method through the change of the tip geometry. In this regard, the shape of the blade tip is somehow considered that the tip clearance size is variable from leading edge to trailing edge. The results show that in these cases, tip leakage flow and the resulting vertices are weakened, which leads to a decrease in the rotor loss coefficient. Observing the flow contours results in lower temperatures in the blade region due to the formation of a weaker tipping leak flow, which helps cool the turbine blades.
Keywords
Axial turbine
tip leakage flow
passive control
Numerical simulation

Subjects

[1] B. Mischo, Axial Turbine Rotor Aero-Thermal Blade Tip Performance Improvement through Flow Control, PhD Thesis, Swiss Federal Institute of Technology Zurich, Zurich, 2008.
[2] M. Chahartaghi, M. Ghatee, A. Samaeeni, H. Karrabi, Numerical simulation of roughness effects on two stage turbine performance with full cooling, Modares Mechanical Engineering, Vol. 13, No. 13, pp. 143-156, 2014. (in Persian فارسی )
[3] G. S. Azad, J. C. Han, S. Teng, R. J. Boyle, Heat transfer and pressure distributions on a gas turbine blade tip, Turbomachinery, Vol. 122, No. 4, pp. 717-724, 2000.
[4] G. S. Azad, J. C. Han, R. J. Bunker, C. P. Lee, Effect of squealer geometry arrangment on a gas turbine blade tip heat transfer, Heat Transfer, Vol. 124, No. 3, pp. 452-459, 2002.
[5] C. De. Maesschalck, S. Lavagnoli, G. Paniagua, N. Vinha, Aerothermodynamics of tight rotor tip clearance flows in high-speed unshrouded turbines, Applied Thermal Engineering, Vol. 65, No. 2, pp. 343-351, 2014.
[6] Y. Kuahai, H. Liuxian, X. Yang, Y. Zhufeng, Influence of tip injection and film cooling for blade tip flow and heat, Applied Mechanics and Materials, Vol. 117, No. 1, pp. 643-646, 2012.
[7] M. Papa, R. J. Goldstein, F. Gori, Effects of tip geometry and tip clearance on the mass/heat transfer from a large scale gas turbine blade, Turbomachinery, Vol. 125, No. 1, pp. 90-96, 2003.
[8] A. A. Ameri, R. S. Bunker, J.C. Bailey, Heat transfer and flow on the first stage blade tip of a power generation gas turbine part 1: Experimental results, Turbomachinery, Vol. 122, No. 2, pp. 263-271, April 2000.
[9] A. A. Ameri, R. S. Bunker, J. C. Bailey, Heat transfer and flow on the first stage blade tip of a power generation gas turbine part 2: Simulation results, Turbomachinery, Vol. 122, No. 2, pp. 272-277, April 2000.
[10] A. K. Saha, S. Acharya, R. Bunker, Prakash, Blade tip leakage flow and heat trancfer with pressure-side winglet, Rotating Machinery, Vol. 6, No. 1, pp. 1-15, 2006.
[11] L. Key, T. Arts, Comparison of turbine tip leakage flow for flat tip and squealer tip geometries at high speed conditions, Turbomachinery, Vol. 128, No. 2, pp. 213-220, 2006.
[12] J. S. Kwak, J. C. Han, Heat transfer coefficients on the squealer tip and near squerler tip regions of a gas turbine blade, Heat Tranfer, Vol. 125, No. 4, pp. 669-677, 2003.
[13] M. H. Rahman, S. I. Kim, I. Hassan, Tip leakage flow and heat transfer on turbine blade tip and casing, part 1: Effect of tip clearance height and rotation speed, Computational Methods in Engineering Science and Mechanics, Vol. 14, No. 4, pp. 290–303, 2013.
[14] L. Wei, Q. Weiyang, X. Kaifu, L. Hualing, Numerical simulation of tip clearance controls in axial turbine rotor part 2: Passive control of five different tip platforms, Thermal Science, Vol. 17, No. 2, pp. 147-155, 2008.
[15] L. P. Timko, Energy Efficient Engine High Pressure Turbine Component Test Performance Report (NASA CR-168289), National Aeronautics and Space Administration, Washington D.C, 1984.
[16] M. Chahartaghi, M. Ghatee, A. Samaeenia, H. Karrabi, Study and numerical simulation of blades corrosion effects on a commercial axial turbine performance, Modares Mechanical Engineering, Vol. 14, No. 15, pp. 279-289, 2015. (in Persian فارسی )
Modares Mechanical Engineering
Volume 18, Issue 4
August 2018
Pages 62-70