Aerodynamic Characteristics of High Speed Train Pantograph

with the Optimized Panhead Shape

Yeongbin Lee, Joohyun Rho, Minho Kwak, Jaeho Lee, Kyuhong Kim, and Dongho Lee

School of Mechanical and Aerospace Engineering

Seoul National University, Institute of Advanced Aerospace Technology

San 56-1, Shinlim-dong, Gwanak-Gu

Seoul, Republic of Korea

aerocfd1@snu.ac.kr, http://hypersonic.snu.ac.kr

Abstract: - One of the most important reasons which restrict the speed increasing is the limitation of power transmission

between the pantograph and the contact lines. It is due to an unexpected aerodynamic characteristics that is vortex

shedding behind the pantograph. It causes an acoustic noise and structural vibration. The aerodynamic characteristics as

shapes of pantograph are the main issue. For removing those problems, a new pantograph shapes had been proposed for

the Korea high speed train. In this research, the optimized shape was selected through the previous research and then

alanyzed by experimental test. The pantograph with the optimized panhead shape was compared with the basic

pantograph system as the commercial high speed train(KTX-II) in korea for aerodynamical advantages. The optimized

panhead shape showed the increasement of the aerodynamic performance of entire pantograph system on the high speed

train.

Key-Words: - Aerodynamics, High speed train, Pantograph system, Optimized panhead shape, Wind tunnel experiment

1 Introduction A high speed train (HST) has been rapidly developed all

over the world. Researchers realized that one of the most

important reasons which restrict the speed increasing of

electric locomotives is the capability of power

transmission between the pantograph and the contact

lines. The Korean high speed train named HEMU-400X

is being devleoped for 400 km/h as maximum speed.

There are many problems encountered when it runs. The

problems are an aerodynamic drag, instability caused by

a structural vibration, acoustic noise and so on [1,2].

When vehicles travel at high speed, power transmission is

influenced by aerodynamic characteristics of the

pantograph. A favorable aerodynamics performance of

the pantograph system ensures perfect track capability,

the stable contact between of panhead and the contact

lines. It can help to reduce an wear and acoustics noise

[3,4]. However, it is difficult to prevent the diffusion of

such problems, because the pantograph system is located

on train roof. Therefore, several researchers have studied

the aerodynamic characteristics around the pantograph

and made an effort to solve the problems [3,5,6].

General pantograph system is shown in Fig.1 and that is

for Korea high speed train(HST-350X). It consists of

many subparts and is so complex. Thus, it is so difficult to

analyze the aerodynamic characteristics of each subpart

and to find what are grave importance.[7] Through the

researches, the panhead part was known the most

important device to determine the aerodynamic

characteristics of high speed pantograph system as shown

in table 1.

Table 1 Aerodynamic load on pantograph [7]

Sub part Fx Fy Fz [kgf]

(1) Lower arm 5.3 0.0 12.5

(2) Strut road 4.2 0.0 7.2

(3) Upper arm 3.2 0.0 - 9.2

(4) Balance road 0.8 0.0 - 2.7

(5) Plunger 12.8 0.0 0.0

(6) Panhead 94.5 0.0 13.5

Fig.1 Pantograph system

Proceedings of the 7th IASME/WSEAS International Conference on FLUID MECHANICS and AERODYNAMICS

ISSN: 1790-5095 84 ISBN: 978-960-474-106-9

Fig.2 Panhead aerodynamic acoustic noise [8]

General panhead shapes are square or circular cylinder.

After this blunt body, the flow is separated and/or

developed to be turbulent. In some flow condition, the

Karman vortex street is founded. This complex flow

induces a structural vibration due to an unexpected

increasement of lift and drag force. It may causes a

damage for the panhead and unstability of the current

supply by electric wire. For resolving these problems, an

optimized stream lined shape should be needed. And the

passive flow control strategy using holes was studied as

shown in Fig.2[8,9]

In this research, the optimized shape is selected firstly

and then analyzed by wind tunnel experiments for

investigating an aerodynamic characteristics as the given

panhead shapes. The pantograph system with optimized

panhead shape compared with basis pantograph system

as the KTX-II train(commercial korean high speed train)

in the point of aerodynamical advantages. The

experimental results showed that the aerodynamic

performance of entire pantograph system was increased

by the optimized panhead shape increase on high speed

train.

2 Experimental model and setup

2.1 Experimental model Robust optimized panhead shapes have been designed by

previous researches for favorable aerodynamic

characteristics of the pantograph system as shown in Fig.

3 [10]. For optimization of the shape, CFD studies were

also conducted by In-house code was 2-D Navier-Stokes’

solver including Roe’s FDS scheme for spatial

discretization and LU-SGS with dual time stepping for

time integration. All analysis and optimization are carried

out with Integrated Super Computing System (ISS) in

Tohoku University.

Fig.3 Sectional shape of optimized panhead

Fig.4 Wind tunnel test model (1/4 scale)

Fig.5 Model and DAQ system

Two scaled models (1:0.25) were examined to know the

performance improvement. One was a basis model as the

KTX-II pantograph system which will be served in

commercial service. And the other was pantograph with

optimized sectionnl shape as shown in right side of Fig. 4.

The model height was 275 mm from upper base fairing as

shown in left side of Fig 4. Total weight was about 5.5kg

and it made of Al alloy and heat treatment iron.

2.2 Experimental Setup The experiments were performed in a closed-type low

turbulence wind tunnel in Postech, Korea. The dimension

of the closed test section is 1.5 m (height) ×1.8 m (width)

×4.6 m (length) and the maximum wind speed is about

75m/s with a turbulence intensity being less than 0.2%.

The blockage ratio of the experimental model is about

2.5%. The data acquisition program is made use of

LABView with multi-purpose DAQ system which has

E-6110 board from National Instruments Company as

shown in Fig. 5. The aerodynamic forces were measured

by 2 axis load cell. The data were measured 18 times

which were performed 10 times in preliminary test and 8

times in main test because of hysteresis and accuracy.

The experimental Reynolds number range was controlled

from 2 × 105 to 6 × 105 and characteristic length was

defined the panhead length (145mm).

3 Experimental results These figures show the experimental results of the

panhead and the pantograph systems in basis model and

the optimized one. As the results of the basis panhead

shape and the optimized panhead shape [Fig. 6~9], the

Proceedings of the 7th IASME/WSEAS International Conference on FLUID MECHANICS and AERODYNAMICS

ISSN: 1790-5095 85 ISBN: 978-960-474-106-9

Fig.6 Basis panhead drag (forward direction)

Fig.7 Optimized panhead drag (forward direction)

Fig.8 Basis panhead lift (forward direction)

Fig.9 Optimized panhead lift (forward direction)

Fig.10 Basis pantograph bidirectional mean drag

Fig.11 Optimized pantograph bidirectional mean drag

Fig.12 Basis pantograph bidirectional mean lift

Fig.13 Optimized pantograph bidirectional mean lift

Proceedings of the 7th IASME/WSEAS International Conference on FLUID MECHANICS and AERODYNAMICS

ISSN: 1790-5095 86 ISBN: 978-960-474-106-9

Fig.14 Mean drag distribution (forward direction)

Fig.15 Mean drag distribution (backward direction)

Fig.16 Mean lift distribution (forward direction)

Fig.17 Mean lift distribution (backward direction)

optimized panhead shape has lower drag and lift than

basis shape. The basis panhead shape is the parallel

square cylinder. Because of blunt body shape, it makes

the larger vortex shedding from the panhead. It caused the

unsteady lift force fluctuation, the structural instability

and severe acoustic noise. Contrary to the basis shape, the

optimized panhead shape showed to prevent the large

vortex shedding.

The optimized shape reduced the drag about 40% and

maximum amplitude of lift about 25% than basis panhead

shape.

In addition, the flow diection effect was studied because a

train would move bidirectionally. As the flow direction is

backward shown in [Fig. 10~13], the mean drag and lift

force value(averaged for eight test cases) measured

similar to forward flow case when panhead was basis

shape. This result arise from the non-directional shape of

the square cylinder.

In case of the optimized panhead shape, mean drag force

measured lower than the basis panhead shape in

backward flow. But, the mean lift is higher. It is

disadvantage for streamlined body shape. The leading

edge of the optimized shape showed good aerodynamic

performance for any angles of attack. But, sharp trailing

edge is not good. That is to say, the optimized panhead

shape has the weakness when the pantograph system is in

the backward flow. However, it will not be important

issue because the korean high speed train use only

forward direction because of using intensify the push-pull

type.

From the present results of the mean drag and lift force

distribution as flow direction [Fig.14~17], the panhead

shape effect has over half porting of whole drag and lift

production. The present work showed that an important

key to make a decision the aerodynamic performance

because the pantograph system is consisted of various

parts. Therefore, the efficient way to design a whole

pantograph system is optimized a panhead shape.

4 Conclusion The experiments were performed to know aerodynamic

characteristics of pantograph system using wind tunnel.

The optimized panhead shape is chosen through

reviewing the previous research results. Then the

aerodynamic characteristics of pantograph with the

optimized panhead shape was compared with basis

pantograph system for performance advantage of

commercial high speed train.

From this work, the panhead shape was important on

whole performance of the pantograph system.

Considring flow conditions, the optimized panhead shape

showed the low mean drag and lift force than basis

panhead shape. Therefore the optimized panhead shape

Proceedings of the 7th IASME/WSEAS International Conference on FLUID MECHANICS and AERODYNAMICS

ISSN: 1790-5095 87 ISBN: 978-960-474-106-9

increases the aerodynamic performance of entire

pantograph system on the high speed train.

Acknowledgements:

This work was supported by the BK 21 Project, GCOE,

NSL(S10801000121-08A0100-12110) and Railroad

Technology Development Program.

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Proceedings of the 7th IASME/WSEAS International Conference on FLUID MECHANICS and AERODYNAMICS

ISSN: 1790-5095 88 ISBN: 978-960-474-106-9