剥離を伴う航空エンジン用低圧タービン翼面境界層の遷移 挙動に関する研究 *岩手大学 工学部 船 﨑 健 一† 岩手大学 工学部 谷 口 英 夫 岩手大学大学院 博士前期課程 斎 藤 拓 (株)グローバル・ニュークリア・フュエル・ジャパン 酒 井 宏 Studies on Transitional Behavior of Separated Boundary Layer on the Suction Surface of an LP Turbine Airfoil for Aeroengines Ken-ichi Funazaki, Faculty of Engineering, Iwate University Hideo TANIGUCHI, Faculty of Engineering, Iwate University Taku SAITO, Graduate Student, Iwate University Hiroshi SAKAI, Global Nuclear Fuel-Japan Co, Ltd. 1 INTRODUCTION In modern high bypass turbofan engines, low-pressure turbine (LPT) stages are required to provide very huge power output to drive large fan for propulsion and additional booster stages very efficiently. Due to the relatively low-speed rotation, the aerodynamic loading of the LPT stages is usually quite high and inevitably the blade count in the LPT stage tends to be very large for maintaining the stage efficiency as high as possible. As a result, LPT section is one of the heaviest parts of the engine, which could amount to about one-third of the engine’ s total weight. The current design trend of aeroengines is therefore to decrease the number of blades in LPT stages in order to achieve a drastic reduction of engine weight, manufacturing and maintenance costs and total sfc (specific fuel consumption) of aircraft. However, the reduction of the blade number surely induces an increase of the aerodynamic loading on each blade, resulting in the appearance of large separation or separation bubble on the blade suction surface due to the strong adverse pressure gradient, particularly under low Reynolds number conditions. Since this separated flow around the blade causes a significant loss in engine efficiency, there have been a number of relevant studies on separated boundary layer on high-lift LPT blades. Mayle 1) classified the boundary layer transition on LPT blade into three modes in his pioneering paper, describing that separated-flow transition mode could be the most important one for LPT. Nevertheless, it is still necessary to investigate the separated boundary layer because of relatively few studies dealing with its transitional behavior in detail under realistic flow conditions such as Reynolds number and freestream turbulence. Since boundary layer transition and separation depend strongly on these two factors and their interaction 2,3) , it is quite obvious that understanding of the separated boundary layer subjected to such flow disturbance and development of an accurate method to predict its transition is crucial for lighter and more efficient aeroengines. The objective of this paper is to investigate the influence of Reynolds number and freestream turbulence intensity (FTI) on the process of boundary layer transition over the suction side of LPT airfoil. Detailed boundary layer measurements are performed by use of a *〒020-8551 盛岡市上田 4-3-5 †E-mail: [email protected]〔特集〕注目研究 in 年会 2011 479 ながれ30(2011)479-487
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剥離を伴う航空エンジン用低圧タービン翼面境界層の遷移
挙動に関する研究
*岩手大学 工学部 船 﨑 健 一†
岩手大学 工学部 谷 口 英 夫
岩手大学大学院 博士前期課程 斎 藤 拓
(株)グローバル・ニュークリア・フュエル・ジャパン 酒 井 宏
Studies on Transitional Behavior of Separated Boundary Layer on the
Suction Surface of an LP Turbine Airfoil for Aeroengines
Ken-ichi Funazaki, Faculty of Engineering, Iwate University
Hideo TANIGUCHI, Faculty of Engineering, Iwate University
Taku SAITO, Graduate Student, Iwate University
Hiroshi SAKAI, Global Nuclear Fuel-Japan Co, Ltd.
1 INTRODUCTION
In modern high bypass turbofan engines,
low-pressure turbine (LPT) stages are required to
provide very huge power output to drive large fan for
propulsion and additional booster stages very efficiently.
Due to the relatively low-speed rotation, the
aerodynamic loading of the LPT stages is usually quite
high and inevitably the blade count in the LPT stage
tends to be very large for maintaining the stage
efficiency as high as possible. As a result, LPT section is
one of the heaviest parts of the engine, which could
amount to about one-third of the engine’s total weight.
The current design trend of aeroengines is therefore to
decrease the number of blades in LPT stages in order to
achieve a drastic reduction of engine weight,
manufacturing and maintenance costs and total sfc
(specific fuel consumption) of aircraft. However, the
reduction of the blade number surely induces an increase
of the aerodynamic loading on each blade, resulting in
the appearance of large separation or separation bubble
on the blade suction surface due to the strong adverse
pressure gradient, particularly under low Reynolds
number conditions. Since this separated flow around the
blade causes a significant loss in engine efficiency, there
have been a number of relevant studies on separated
boundary layer on high-lift LPT blades. Mayle1)
classified the boundary layer transition on LPT blade
into three modes in his pioneering paper, describing that
separated-flow transition mode could be the most
important one for LPT. Nevertheless, it is still necessary
to investigate the separated boundary layer because of
relatively few studies dealing with its transitional
behavior in detail under realistic flow conditions such as
Reynolds number and freestream turbulence. Since
boundary layer transition and separation depend strongly
on these two factors and their interaction2,3)
, it is quite
obvious that understanding of the separated boundary
layer subjected to such flow disturbance and
development of an accurate method to predict its
transition is crucial for lighter and more efficient
aeroengines.
The objective of this paper is to investigate the
influence of Reynolds number and freestream turbulence
intensity (FTI) on the process of boundary layer
transition over the suction side of LPT airfoil. Detailed
boundary layer measurements are performed by use of a *〒020-8551 盛岡市上田 4-3-5