1. 1
Proceedings of ASME Turbo Expo 2012: Power for Land, Sea and Air
GT2012
June 11-15, 2012, Copenhagen, Denmark
GT2012- 69295
EXPERIMENTAL INVESTIGATION OF TURBINE PHANTOM COOLING ON SUCTION SIDE WITH
COMBUSTOR-TURBINE LEAKAGE GAP FLOW AND ENDWALL FILM COOLING
Yang Zhang, Xin Yuan
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education
Tsinghua University
Beijing 100084, P.R. China
Email: zhangyange436@yahoo.com.cn
ABSTRACT
The film cooling injection on Hp turbine component
surface is strongly affected by the complex flow structure in
the nozzle guide vane or rotor blade passages. The action of
passage vortex near endwall surface could dominate the film
cooling effectiveness distribution on the component surfaces.
The film cooling injections from endwall and airfoil surface
are mixed with the passage vortex. Considering a small part
of the coolant injection from endwall will move towards the
airfoil suction side and then cover some area, the interaction
between the coolants injected from endwall and airfoil surface
is worth investigating. Though the temperature of coolant
injection from endwall increases after the mixing process in
the main flow, the injections moving from endwall to airfoil
suction side still have the potential of second order cooling.
This part of the coolant is called “Phantom cooling flow” in
the paper. A typical scale-up model of GE-E3
Hp turbine NGV
is used in the experiment to investigate the cooling
performance of injection from endwall. Instead of the endwall
itself, the film cooling effectiveness is measured on the airfoil
suction side. This paper is focused on the combustor-turbine
interface gap leakage flow and the coolant from fan-shaped
holes moving from endwall to airfoil suction side. The
coolant flow is injected at a 30deg angle to the endwall
surface both from a slot and four rows of fan-shaped holes.
The film cooling holes on the endwall and the leakage flow
are used simultaneously. The blowing ratio and incidence
angle are selected to be the parameters in the paper. The
experiment is completed with the blowing ratio changing
from M=0.7 to M=1.3 and the incidence angle varying from
-10deg to +10deg, with inlet Reynolds numbers of
Re=3.5×105
and an inlet Mach number of Ma=0.1.
NOMENCLATURE
C =actual chord length of scaled up blade profile
D =film hole diameter, mm
i =incidence angle
I =light intensity
L =length of film hole, mm
LE =leading edge
M =blowing ratio, ρcVc/ρ∞V∞
Ma =Mach number
PS =pressure side
PSP =pressure sensitive paint
Rein =Reynolds number
S =span of the scaled up two-dimensional blade
SS =suction side
V =velocity, m/s
X , Z =Cartesian coordinate system
 =film cooling effectiveness
Subscripts
aw =adiabatic
ax =axial chord
c =coolant fluid
mix =mixture condition
ref =reference value
sp =span wise
 =free stream condition
INTRODUCTION
As inlet temperature in modern gas turbine increases, the
higher thermal loading on the Hp turbine makes heavy
demands on nozzle guide vanes cooling. The introduction of
film cooling technique in first stage turbine stator of advanced
industrial gas turbine makes further improvement in
performance possible. With adequate cooling, the lifetime of
components may be extended because of lower thermal
stresses on the turbine. The endwall and airfoil junction
region is difficult to cool due to the complex secondary flow
structure and strong pressure gradient in the passage.
However, the real gas turbine operation experience shows that

2. 2
the corner region on the suction side is cooled sufficiently
rather than over heating. Given the truth that the coolant
injection from the suction side film cooling holes could not
cover the corner region, an assumption is that some coolant
on the endwall is influenced by the passage vortex, moving
towards the suction side surface. The goal of this paper is to
investigate the possibility of this assumption and to
investigate the behavior of this kind of “phantom cooling
flow”.
As for the film cooling research using PSP technique,
Wright and Blake et al. [1] used the PSP to investigate the
effects of the upstream wake and vortex on platform film
cooling. It was determined that the upstream wake had only a
negligible effect on the platform film cooling effectiveness.
The film cooling effectiveness could be significantly reduced
with the generation of a vortex upstream of the blade passage.
Wright et al. [2] used the PSP technique to measure the film
cooling effectiveness on a turbine blade platform due to three
different stator-rotor seals. Three slot configurations placed
upstream of the blades were used to model advanced seals
between the stator and rotor. PSP was proven to be a valuable
tool to obtain detailed film cooling effectiveness distributions.
Gao et al. [3] studied turbine blade platform film cooling with
typical stator-rotor purge flow and discrete-hole film cooling.
The shaped holes presented higher film-cooling effectiveness
and wider film coverage than the cylindrical holes,
particularly at higher blowing ratios. The detailed film
cooling effectiveness distributions on the platform were also
obtained using PSP technique. Results showed that the
combined cooling scheme (slot purge flow cooling combined
with discrete-hole film cooling) was able to provide full film
coverage on the platform.
The measurements were obtained by Charbonnier et al.
[4] applying the PSP technique to measure the coolant gas
concentration. An engine representative density ratio between
the coolant and the external hot gas flow was achieved by the
injection of CO2. Zhang et al. [5] used the back-facing step to
simulate the discontinuity of the nozzle inlet to the combustor
exit. Nitrogen gas was used to simulate cooling flow as well
as a tracer gas to indicate oxygen concentration such that film
effectiveness by the mass transfer analogy could be obtained.
An experimental study has been performed by Wright and
Gao et al. [6] to investigate the film cooling effectiveness
measurements by three different steady state techniques:
pressure sensitive paint, temperature sensitive paint, and
infrared thermograph. They found that detailed distributions
could be obtained in the critical area around the holes, and the
true jet separation and reattachment behaviour is captured
with the PSP. Zhang et al. [7] measured film cooling
effectiveness on a turbine vane endwall surface using the PSP
technique. Using PSP, it was clear that the film cooling
effectiveness on the blade platform is strongly influenced by
the platform secondary flow through the passage.
The studies of incidence angle effect on flow field and
heat transfer were also preformed by researchers. Gao et al. [8]
studied the influence of incidence angle on film cooling
effectiveness for a cutback squealer blade tip. Three incidence
angles were investigated 0 deg at design condition and ±5 deg
at off-design conditions. Based on mass transfer analogy, the
film-cooling effectiveness is measured with PSP techniques.
It was observed that the incidence angle affected the coolant
jet direction on the pressure side near tip region and the blade
tip. The film-cooling effectiveness distribution was also
altered. Lee et al. [9] studied the effects of incidence angle on
the endwall convective transport within a high-turning turbine
rotor passage. Surface flow visualizations and heat/mass
transfer measurements at off-design conditions were carried
out at a fixed inlet Reynolds number for the incidence angles
of -10 deg, -5 deg, 0 deg, +5 deg, and +10 deg. The results
showed that the incidence angle had considerable influences
on the endwall local transport phenomena and on the
behaviors of various endwall vortices. In the negative
incidence case, convective transport was less influenced by
the leading edge horseshoe vortex. In the case of positive
incidence, however, convective transport was augmented
remarkably along the leading edge horseshoe vortex, and is
much influenced by the suction-side corner vortex.
As for the investigations about combustor- turbine
leakage flow, researchers had made significant contributions.
With the investigations on a thorough and profound level, the
influence of slot shape, position as well as width had been
analyzed in a series of literature materials. [10-12] Oke, Rohit
A. [13]had investigated the film cooling flow introduced
through two successive rows of slots, a single row of slots and
slots that have particular area distributions in the pitchwise
direction. Wright et al. [14] used a 30 deg inclined slot
upstream of the blades to model the seal between the stator
and rotor. 12 discrete film holes were located on the
downstream half of the platform for additional cooling.
Rehder, H.[15] experimentally investigated the influence of
turbine leakage flows on the three-dimensional flow field and
endwall heat transfer. In the experiment pressure distribution
measurements provided information about the endwall and
vane surface pressure field and its variation with leakage flow.
Additionally streamline patterns (local shear stress directions)
on the walls were detected by oil flow visualization. Piggush,
J.D.[16] investigated the leakage flow and misalignment
effects on the endwall heat transfer coefficients within a
passage which had one axially contoured and one straight
endwall. The paper documented that leakage flows through
such gaps within the passage could affect endwall boundary
layers and induce additional secondary flows and vortex
structures in the passage near the endwall.
Past research has shown that the PSP technique is a
useful tool in film cooling research. Many studies have
investigated the suction side film cooling at off-design
condition, indicating the incidence angle could change the
component surface heat transfer. Few studies, however, have
considered the cooling function of endwall film cooling flow
on the airfoil suction side at off-design condition. To help fill
the vacancy, the current paper discusses the effect of
incidence angle on the phantom cooling (in this paper it
means the coolant moving from endwall to the suction side)
on the nozzle guide vane suction side.

3. 3
FILM COOLING EFFECTIVENESS MEASUREMENT
THEORY AND DATAANALYSIS
The PSP techniques are mainly based on a physical
process called oxygen quenched photoluminescence which
could be generally described as: After excited by a suitable
light source the active part of PSP will emit light, yet this
process will be interrupted by collisions with oxygen
molecules. The result is that the PSP molecules may relax
back to their unexcited state without emitting visible light if
the local oxygen partial pressure is high. Given that the local
oxygen partial pressure is related to the local pressure of gas
which contains oxygen, such as air, the emitted light intensity
is directly related to the local pressure of surrounding air. A
high spectral sensitivity CCD camera and light emitting diode
(LED) lights are used in the study to receive the emitted light
and to excite the Ruthenium-based paint respectively. The
paint is excited at 450 nm and the camera is fitted with a 600
nm band pass filter. In the current study, the main stream is
air containing approximately 21% oxygen and the cooling
flow is pure nitrogen in which the partial pressure of oxygen
was 0%. The film effectiveness can be expressed by oxygen
concentration, which can be measured by the PSP:
2
mix aw
N c
C C T T
C C T T
  
 
 
  
 
(1)
Where C
and mixC represents the oxygen concentration of
the main stream and the air/nitrogen mixture (0% to 21%)
respectively. Therefore the film effectiveness is between 0%
(far upstream and downstream) and 100% (inside the hole).
   
 
2 2
2
O Oair mix air mix
air O
air
P PC C
C P


  (2)
Figure 1. CALIBRATION SYSTEM.
In order to measure the film cooling effectiveness, four
images taken at the same main stream temperature are
required for the PSP film cooling test. A dark image is taken
without LED light and the main stream flow. A reference
image is taken without main stream, but with LED light on.
An air injection image and a nitrogen injection image are
taken with both the main stream flow and LED light on, while
the coolant gas is air and nitrogen respectively. The reference
divided by the nitrogen-injection image and the air-injection
image could be obtained with these four groups of images.
The reference data derived from the air-injection image
contains the change in oxygen concentration due to the
change in pressure which is not the contributor to film cooling
effectiveness computation. The other reference data derived
from the nitrogen-injection image yields the absolute oxygen
concentration. With these two groups of reference ratios the
film cooling effectiveness could be obtained with the mass
transfer/heat transfer analogy.
Figure 2. CALIBRATION CURVE FOR PSP.
Before the test, PSP should be calibrated to obtain the
curves representing relationship between light intensities and
local partial pressure of oxygen. Fig.1 shows a sketch of the
PSP calibration system. The PSP coated copper coupon was
used to simulate the experimental surface, with three
thermocouples installed underneath the front surface to
measure the surface temperature during the calibration. The
sample coupon was located inside a sealed chamber where a
partial or total vacuum could be created. The sample was
heated by a heater at the back side of the coupon which could
keep the sample at a desired temperature with an accuracy of
better than 0.5 K. The camera was located facing the sample
coupon through a transparent window. Given the experiment
environment was at a pressure of approximately 1atm and at a
temperature between 298 K and 308 K, the PSP was
calibrated under two temperatures 298 K and 308 K and
pressures from vacuum to 1atm. The calibration was also
done at a low temperature of 276.5 K to completely
investigate the influence of temperature. The calibration
results are presented in the curves indicating the relationship
between intensity ratio and pressure ratio (Fig.2). As shown
in the figure, the three curves representing different
temperature are close to each other nearly collapsing into one
curve, which indicates that the influence of temperature is
little. The dimensionless temperature downstream of the
cooling holes could be obtained using the light intensities, as
defined in Eq.(3):
c
T T
T T



 

(3)
The adiabatic wall temperature is reflected by the film
cooling effectiveness which is used as a dimensionless
parameter, defined as Eq. (4) for low speed and constant
property flows.
aw
c
T T
T T
 




(4)

4. 4
Based on 95% confidence interval the uncertainties of
the dimensionless temperature and the film cooling
effectiveness are estimated as 3% at a typical value of 0.5.
However, the uncertainty rises with the effectiveness
approaching zero, resulting in an uncertainty of
approximately 20% when the value is 0.05.
EXPERIMENTAL FACILITY
The schematic view of the test rig is shown in Fig. 3. and
Fig.4. The test section consists of a four-blade linear cascade
whose geometry is typical of a first stage high pressure nozzle
guide vane, GE-E3
, with endwall surface [17]. The inlet cross
section of the test section is 318 mm (width) and 129 mm
(height). Turbulence intensity is recorded 100 mm upstream
of the middle passage using a hot-wire probe. Turbulence
intensity at this location is found to be 9.5% due to the
presence of the grid. The bottom and sides on the test section
are machined out of 15 mm thick organic glass plate whereas
a 10 mm thick organic glass plate is used for the top for better
optical access to the endwall surface. Flow conditions in
adjacent passages of the center blade are ensured to be
identical by adjusting the trailing edge tailboards for the
cascade. During the experiment, the cascade inlet air velocity
is maintained at 35 m/s for all the incidence angle cases,
which corresponds to a Mach number of Ma=0.1 at inlet. A
two times scaled model of the GE-E3
guide vanes is used with
a blade span of 129 mm and an axial chord length of 78.8 mm.
There is no radius at the interface between the vane and the
endwall. Only a leading edge fillet is used in the test cascade.
Figure 3. SCHEMATIC OF CASCADE TEST RIG.
Figure 4. SCHEMATIC OF THE TEST SECTION WITH ROTATABLE
CASCADE.
Figure 5. FILM COOLING HOLE AND LEAKAGE GAP CONFIGURATION
Figure 6. THE GEOMETRY OF THE ENDWALL WITH UPTREAM
COMBUSTOR-TURBINE LEAKAGE GAP.
Past studies in the open literature have shown that the
passage cross flow sweeps the film coolant from pressure side
to suction side due to the pressure gradient in the passage [18].
To reflect this phenomenon more apparently, all of the film
cooling holes are positioned in straight lines. Studies on the
flat plates show that coolant from compound angle holes
covers wider area due to jet deflection. Four rows of
compound angle laidback fan-shaped holes are arranged on
the endwall to form full covered coolant film. Fig.5 shows the
holes configurations and the blade geometric parameters. The
first row is located upstream of the leading edge plane. The
following three rows are evenly positioned inside the vane
channel, with the last one located at 65% axial chord
downstream of the leading edge. Fig.5 and Fig.6 show that
the width of the slot is 1.5 mm, and the length is 9.1 mm,
turning 60 deg before being expelled onto the passage end
wall. The slot is located 35.2 mm upstream of the blade
leading edge, and the slot covers 1.5 passages of the linear
cascade. In the experiment both of the film cooling holes and
upstream slot are used. (Fig.7) Due to the large pressure
gradient on the endwall, it is difficult to control the local
blowing ratios for every single hole with one common coolant
plenum chamber.
The research by Kost F., Mullaert [19] indicates that both
the leakage flow of endwall upstream slot and the film
cooling ejection are strongly influenced by the endwall
pressure distribution. The leakage flow and the film cooling
ejection will move towards the low pressure region where
high film cooling effectiveness is captured. The influence the
pressure distribution could also explain why the suction side
is cooed better than the pressure side. Another important
factor is the passage vortex moved by the pressure gradient in

5. 5
the cascade. It could lead the coolant to move towards the
suction side.
In the current study, five coolant cavities are used for the
slot and four rows of holes respectively. The coolant supplied
to each cavity is controlled by a shared rotameter. During the
test, the tail boards, and the CCD camera are moved with the
rotatable plate to the same relative position as that at
incidence angle of 0deg. (Fig.8) In this study, three different
positions were chosen for the incidence angles of i = -10 deg,
0deg and +10 deg. The blowing ratio of the coolant is varied,
so the film cooling effectiveness can be measured over a
range of blowing ratio varying from M=0.7 to M=1.3 based
on the mainstream flow inlet velocity.
Figure 7. INJECTION CONFIGURATION AND THE COOLANT MOVING
FROM ENDWALL SURFACE TO SUCTION SIDE
Figure 8. TEST RIG WITH EXCITATION LIGHTS AND THE CCD CAMERA
RESULTS AND DISCUSSION
slot M=0.7 i= 0deg
Z/Zsp
X/Xax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(a)
slot M=1.0 i= 0deg
Z/Z
sp
X/X
ax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(b)
slot M=1.3 i= 0deg
Z/Z
sp
X/Xax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(c)
Figure 9 ． FILM COOLING EFFECTIVENESS DISTRIBUTION ON THE
SUCTION SIDE AT DIFFERENT BLOWING RATIO ( I=0DEG )
The film cooling effectiveness distributions at different
blowing ratios are shown in Fig.9-Fig.14., where three typical
blowing ratios are chosen to be M=0.7, M=1.0, and M=1.3.
The same trend could be found in the figures that the area
coverage of coolant film is lager at higher blowing ratio.
Although valuable insight can be obtained from the
distribution maps (Fig.9, Fig.10 and Fig.11), the spanwise
averaged plots (Fig.12, Fig.13 and Fig.14) offer additional
insight and provide clear comparisons for large amounts of
data. The effectiveness is averaged from the bottom endwall
junction to the top boundary of corner region on the suction
side (red lines in Fig.9, Fig.10 and Fig.11) along the axial
chord direction. The height of the corner region relative to the
span height is 0.18. The data on the endwall surface is deleted
from the averaged results. The start points of the plots
correspond to the corner region left boundary.
Fig.12, Fig.13 and Fig.14 indicate that increasing the
injection rate increases the film cooling effectiveness. The
lowest film cooling effectiveness appears at M=0.7. The
average film cooling effectiveness is higher with the
increasing in axial chord, as shown in Fig.12, Fig.13 and

6. 6
Fig.14. The main passage vortex is moving towards the
suction and finally becomes the suction side wall vortex in the
corner region. The coolant moving from endwall to suction
side is strongly influenced by the passage vortex and its trace
is limited by the vortex boundary. As the vortex lifting the
endwall the cooled area on the suction side becomes wider.
The higher film cooling effectiveness is caused by the wider
cooled area and the direction of the passage vortex.
Fig.9 shows the film cooling effectiveness distribution
on the suction side at different blowing ratio, while the
incidence angle is controlled to be i=0deg. With the blowing
ratio increasing, the area protected by the coolant is getting
larger. (The top boundary of the triangle is nearer to the red
line)Though the coolant could cover the main part of the
corner region, the unprotected area near the top boundary is
still apparent. This phenomenon represents that the moving
direction of the passage vortex in the turbine cascades
dominant the moving direction of the coolant traces. The
momentum of the coolant injection is not strong enough to
take the cool air outside the passage vortex. The similar case
could be observed near the leading edge where the coolant
could only cover a triangular area and then the coolant is
taken by the passage vortex.
slot M=0.7 i= -10deg
Z/Zsp
X/X
ax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(a)
slot M=1.0 i= -10deg
Z/Z
sp
X/X
ax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(b)
slot M=1.3 i= -10deg
Z/Z
sp
X/X
ax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(c)
Figure 10． FILM COOLING EFFECTIVENESS DISTRIBUTION ON THE
SUCTION SIDE AT DIFFERENT BLOWING RATIO ( I=-10DEG )
With the blowing ratio increasing, the original
momentum of the coolant increases. Higher blowing ratio
leads more coolant moving towards suction side that the peak
position of average film cooling effectiveness is higher. As
the coolant leaving the slot and the film cooling holes, the
trace of the injection flow is led by the passage vortex moving
along the suction side. The vortex is strong on the
downstream part of the airfoil, which causes the boundary of
coolant to move according to the triangular vortex geometry.
The film cooling effectiveness distributions indicates that the
phantom cooling function of leakage flow and the cooling
holes is limited. The injection could cover the downstream
part (axial chord is larger than 0.6) of suction side and even
over cool this area, while the upstream part (axial chord is
between 0.4 and 0.6) is still exposed to the hot environment.
To increase the blowing ratio could partly improve the
cooling effectiveness, but the film cooling performance in the
upstream suction side corner region is not satisfied.
Fig.10 and Fig.11 indicate the film cooling effectiveness
distributions at off-design conditions. At negative incidence
angle, as shown in Fig.10, the main difference from the
design condition is that, at low blowing ratio the cooled area
is smaller. This phenomenon shows that the negative
incidence angle leads the passage vortex to move backward
slightly. The top boundary of the triangle region is not close
to the red line in the figures. This change is also obvious at
higher blowing ratio cases. When the blowing ratio is M=1.3,
the boundary of the injection is also not close to the top red
line. This indicates that the effect of the incidence angle is not
sensitive to the blowing ratio. Fig.11 shows the similar trend
that the positive incidence angle could apparently change the
geometry of the cooled area. When the incidence angle is
i=+10deg, the cooled triangular area becomes obviously
larger. The top boundary of the triangle could be above the
red line, which means the cooled area is wider.
Fig.12, Fig.13 and Fig.14 compare the laterally average
film cooling effectiveness at different blowing ratio. The
computing area is between the top and bottom red lines in the

7. 7
contours. As the blowing ratio increasing, the averaged
effectiveness apparently improves. Meanwhile the average
effectiveness increases with increasing axial chord. The well
protected region is the downstream part of the corner region.
On the downstream part of the corner region, the coolant
strongly interacts with the secondary flows such as the
passage vortex and wall vortex. The main flow pushes the
coolant towards suction side, which forces the protected area
to be wider. On the other hand, the main flow further mixes
the coolant and the hot gas on the endwall, which leads the
injection flow to lift off the endwall surface and then move to
suction side. These two factors cause the average film cooling
effectiveness increase a lot on the downstream part of the
corner region.
The phenomenon captured in this experiment has close
relationship with the flow field in the turbine cascade. The
past literature could provide some important support material.
The research by Rehder, H. and Dannhauer, A [15] indicate
that the leakage flow has apparent influence on three
dimensional flow field of the turbine passage. The flow
visualization experiment shows that the moving trace of the
passage vortex is from pressure side to the suction side. The
passage vortex, as well as the pressure gradient in the cascade
could simultaneously force the coolant on the endwall to
move onto the airfoil suction side. The similar results could
be found in the research report by Papa, M et al. [20]. They
captured the phantom cooling phenomenon on the rotor blade
suction side and the coolant was ejected form a upstream slot.
The paper indicates that the coolant from the endwall would
move towards the suction side and then form a triangular
cooled area. Though the passage vortex and the pressure
gradient in the rotor passage are stronger than that of the
NGV, the mechanism of the suction side phantom cooling is
similar. The comparable results provide a reasonable explain
to the phantom cooling phenomenon in this experiment.
Fig.15-17 compare the laterally average film cooling
effectiveness in the corner region at different incidence angle.
The boundaries of the computing area are indicated with top
and bottom red lines along the junction line in Fig.9, Fig.10
and Fig.11. The subplot (a) in Fig.9, Fig.10 and Fig.11 show
the film cooling effectiveness distributions in corner region at
different incidence angle when the blowing ratio is controlled
to be M=0.7. When the incidence angle is i=+10 deg, the
cooled area is apparently beyond the red boundary in the
contour, while the cooled area is restricted in the corner
region (red lines) in the case of i=0 deg and i=-10 deg. At low
blowing ratio, at positive incidence angle the cooled area is
relatively larger. The subplot (b) in Fig.9, Fig.10 and Fig.11
show the film cooling effectiveness distributions in corner
region at different incidence angle when the blowing ratio is
controlled to be M=1.0. When the incidence angle is i=-10deg,
an apparent unprotected area could be found near the top
boundary of the corner region, while this area is covered by
the coolant at the incidence angle of i=0deg and i=+10deg.
The subplot (c) in Fig.9, Fig.10 and Fig.11 show the film
cooling effectiveness distributions in corner region at
different incidence angle when the blowing ratio is controlled
to be M=1.3. Similar to the lower blowing ratio cases, the
high film cooling effectiveness area at i=+10 deg is obviously
larger than the other two incidence angle cases. The
downstream part of the corner region is fully covered by the
coolant when the incidence angle is i=+10 deg.
slot M=0.7 i= +10deg
Z/Z
sp
X/X
ax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(a)
slot M=1.0 i= +10degZ/Z
sp
X/Xax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(b)
slot M=1.3 i= +10deg
Z/Z
sp
X/Xax
0.45 0.5 0.55 0.6 0.65 0.7
0.6
0.7
0.8
0.9
1
1.1
0
0.1
0.2
0.3
0.4
0.5
(c)
Figure 11． FILM COOLING EFFECTIVENESS DISTRIBUTION ON THE
SUCTION SIDE AT DIFFERENT BLOWING RATIO ( I=+10DEG )

8. 8
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/X
ax

slot i=0deg M=1.3
slot i=0deg M=1
slot i=0deg M=0.7
Figure 12． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT BLOWING RATIO ( I=0DEG )
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/X
ax

slot i=-10deg M=1.3
slot i=-10deg M=1
slot i=-10deg M=0.7
Figure 13． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT BLOWING RATIO ( I=-10DEG )
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/X
ax

slot i=+10deg M=1.3
slot i=+10deg M=1
slot i=+10deg M=0.7
Figure 14． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT BLOWING RATIO ( I=+10DEG )
Fig.15 shows that the positive incidence angle improves
the average effectiveness in the corner region, and the
improvement is obvious along the axial chord. The higher
film cooling effectiveness indicates that the passage vortex is
moving upstream on the suction side in the positive incidence
angle condition. Higher effectiveness means stronger
influence of the passage vortex and wall vortex, which shows
that the positive incidence angle could effectively lead the
passage vortex moving from pressure to suction side earlier
and then becomes the wall vortex at an upstream position on
the suction side. And the effects of the incidence angle will
not decrease as the increasing of axial chord because of the
stronger wall vortex at downstream part of the suction side.
The same trend could be found in Fig.16 and Fig.17, but the
difference among the three curves is larger, especially for the
highest blowing ratio M=1.3. The average effectiveness curve
representing the case of i=0deg is close to the curve of
i=+10deg case in Fig.15. However, the difference of these two
curves is apparent in Fig.17. As the blowing ratio increasing,
the advantage of positive angle is more apparent. The higher
momentum of the coolant injection flow could provide more
coolant moving from endwall to the suction side.
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/X
ax

slot M=0.7 i= -10deg
slot M=0.7 i= 0deg
slot M=0.7 i=+10deg
Figure 15． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT INCIDENCE ANGLE ( M=0.7 )
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/Xax

slot M=1.0 i= -10deg
slot M=1.0 i= 0deg
slot M=1.0 i=+10deg
Figure 16． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT INCIDENCE ANGLE ( M=1.0 )

9. 9
0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66
0.16
0.19
0.22
0.25
0.28
0.31
0.34
0.37
X/X
ax

slot M=1.3 i= -10deg
slot M=1.3 i= 0deg
slot M=1.3 i=+10deg
Figure 17． LATERALLY AVERAGED FILM COOLING EFFECTIVENESS AT
DIFFERENT INCIDENCE ANGLE ( M=1.3 )
Though the Fig. 15-Fig. 17 show that the positive
incidence angle could cause better film cooling performance,
this positive influence is obvious in the upstream part (axial
chord between 0.5 and 0.6) of the corner region while at the
downstream part the positive incidence angle is not a
beneficial factor . At low blowing ration case the positive
incidence angle hinder the film cooling rather than improve it.
When the blowing ration is M=0.7, the film cooling
effectiveness at downstream part is lower than that of the
other two cases, as shown in Fig. 15. The positive incidence
angle could make the passage vortex reach the suction side
earlier, thus the suction side wall vortex forming at smaller
axial chord position. The coolant on the suction side could be
driven by the wall vortex moving towards the mid span region,
which cause the cooled corner region ends at upstream part.
The coolant leaves the corner region early and the
downstream part is uncovered by the coolant. The high film
cooling effectiveness region is beyond the red boundary line
in Fig. 11(a). As the blowing ration increases, the
disadvantage of positive incidence angle is made up by the
more supply of the coolant. Though the film cooling
effectiveness decreases at downstream part when the
incidence is i=+10 deg, the absolute effectiveness is still
higher than the other two cases, as shown in Fig.16 and Fig.
17.
CONCLUSIONS
An experimental study has been performed to investigate
the incidence angle effect on Phantom cooling with
combustor-turbine gap leakage flow and endwall film cooling.
Film-cooling effectiveness has been measured on the suction
side surface at three incidence angles using pressure sensitive
paint. The effectiveness distribution was presented for suction
side corner region. In general, the incidence angle affects the
coolant distribution on the suction side corner region
apparently. The results show that with blowing ratio
increasing, the film cooling effectiveness increases on the
airfoil. As the incidence angle varies from i=+10 deg to i=-10
deg, at every blowing ratio the film cooling effectiveness
decreases in the suction side corner region.
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