होम [IEEE 2011 6th International Forum on Strategic Technology (IFOST) - Harbin, Heilongjiang, China...

[IEEE 2011 6th International Forum on Strategic Technology (IFOST) - Harbin, Heilongjiang, China (2011.08.22-2011.08.24)] Proceedings of 2011 6th International Forum on Strategic Technology - Affecting factors and numerical value calculation relating to vacuumizing time in Evacuated Tube Transportation

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साल:
2011
भाषा:
english
DOI:
10.1109/ifost.2011.6021014
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2011 The 6th International Forum on Strategic Technology

Affecting Factors and Numerical Value Calculation
Relating to Vacuumizing Time in Evacuated Tube
Transportation
Daryl OSTER2, Chen CHEN

Yaoping ZHANG', Jianyue YU, Maoxing SHEN
Institute of Evacuated Tube Transportation, Xijing

Et3.com Inc.

University

Crystal River, Florida 34423-1423, America

Xi'an 710123, China
IE-mail: tubetrans@hotmail.com

2E-mail: et3@et3.com

calculation based on some data. Calculation results will be

Abstract-It's necessary to evacuating air from the Evacuated
Tube Transportation (ETT) system before operation. As for the

used for reference to decide the section size of ETT, layout

airlock, the air would be evacuated at every turn. Start-up speed

pump stations, select right vacuum pumps as well as the initial

of ETT and switching effect of the airlock will mainly depend on

operation simulation[2, 3].

the time to taking out gas. This paper analyses relative factors to
affect the time to taking out gas (vacuumizing) and the function
relating to the time to take out gas, such as orifice conductance,
diameter of the tube, length of the tube, interval space between

IT.

two pumping station, effective vacuumizing speed and target
vacuum degree. Based on the numerical value calculation, some

The vacuumizing pipe between the ETT tube and the

Keywords-Evacuated Tube Transportation; Vacuumizing Time;

pump station need to be linked through orifice, and the

Airlock; Vacuum Degree
1.

ETT TUBE VACUUMIZING TIME

Orifice conductance

A.

suggestions to reduce the time to take out gas were put forward.

BASIC ANAL YSIS FOR

calculation formula of the orifice conductance is as following
[4-6].

INTRODUCTION

(1)

Evacuated Tube Transportation (ETT) will be "Space
Travel on Earth" and green transportation, clean, silent, low
cost, safe, faster than jets, and electric. The ETT car travels in

In the formula:

tubes on frictionless maglev. Air is removed from the tubes

(K);

that are built along a travel route. ETT can;  provide even 50
times more transportation per kWh than electric vehicles or

as

state trips, and will be developed to more than 6000 km/h for

possible.

In ETT high speed maglev transportation, vacuum pump

In addition, the airlocks which are used for transfer of ETT

orifice

the

orifice

diameter

20cm,

gas

Co =3623 (Lis) .

C1

from vacuum to the open atmosphere circumstance, need to be

=

3 • 81

/)1
L

rrA0
"V'M

In this formula: D-Tube diameter

vacuumized hourly.

(2)

( cm )

L-Tube

length (cm) ; M-Gas molar mass (g/mo]) . Suppose the

Vacuumizing time directly affects the operation effect of

tube diameter 400cm, one pump station every 2km (namely

the whole ETT system. Factors to affect vacumizing time

tube length L=100000cm), gas temperature T=293K ,

includes orifice conductance of pipe linking the tube and the

gas

molar mass M=29g/mo!' then the orifice conductance of ETT

pump, tube diameter, interval space between the pump stations,

tube

availability vacuumizing speed and target vacuum degree.
sets

the

In this paper, the tube section of ETT system is thought as

cars from the open atmosphere circumstance to vacuum or

factors,

Thus,

round, then the conductance as following [4-6 ]

vacuumize for the ETT tube so as to remove gas from the tube.

affecting

(g/mol).

Round section long pipe conductance

B.

intervals. Before ETT operation, pumps at pump stations

these

Suppose

orifice conductance

stations will be installed along a travel route at regular

analyzes

mass

temperature T=293K, gas molar mass M=29g/mol. then the

international travel[ I].

paper

Ao --Orifice area (cm\ T--Temperature

molar

conductance to link pump and ETT tube should be larger area

trains. Speed in initial ETT systems is 600� I OOOkm/h for in

This

M--Gas

up

C1 =7750.7 (Lis) .

vacuumizing time equation, and finishs initial numerical value

978-1-4577-0399-7111/$26.00 ©2011lEEE

246

August 22-24,2011

Because the tube and the vacuumizing pipe are linked in

Ill.

ETT

SYSTEM VACUUMIZING TIME NUMERICAL VALUE

series, then the conductance of the vacuumizing obeys the

CALCULATING

following fonnula:

As for ETT system, there are 4 cases to need to pump out

1

1

gas: (a) Vacuumizing from nonnal pressure to low pressure

1

-=
+C
Co
C1

(3)

-

before operation; (b) When getting back vacuum situation
after examining, repairing and contingency; (c) Pumping out
gas from airlock for pressure balance when vehicles enter into

By relating vacuum theory, the availability vacuumizing

or go out the airlock; (d) Pumping out gas after pressure rises

speed obeys the following formula:

1

1

due to ETT system leak or materials deflating. This paper
calculates only for former three cases, namely vacuumizing

1

-=-+Se
So
C

(4)

By the above supposing and calculation, Co =

from normal pressure Po to required pressure intensity. In this
case Po

3623 (Lis),

=

1.0133 Pa.

C1 =

A.

of the pump station So =1800Lls, then we can calculate out

thus it should be considered as slightness structure and the

7750.7 (Lis), then the conductance of the ETT system
C = 2468.9 (Lis). Suppose the nominal vacuumizing speed
the availability vacuumizing speed Se =

C.

Calculating vacuumizing time of the main tube
ETT tube length is much more than the ETT tube diameter,

pressure intensity distribution is asymmetry, as shown in Fig.

1 041 (Lis).

2.

Vacuumizing time equation
As shown in Fig.

Pressure intensity distribution

1, P-the target vacuum pressure

•

intensity of ETT tube (unit: Pa); V-the volume of EIT tube;

x

I I

because the availability vacuumizing speed of the pump
stations much less than the conductance

C,

ETT tube

s,

the vacuumizing
Fig.2 Structure oftaking out gas from ETT system

time can be calculated by the following fonnula[4-7]:

Tn order to predigest calculation, this paper supposes the
pressure along the tube is distributed equably, one vacuum

Container to be vacuumized

(Err tube)
V

C

p

pump station every 2km, ETT tube diameter D =

Se

{2,4,6}

(unit: m), then the loading volume relating to one vacuum
3
pump station V
(unit: m ); Taking

1

=

the

{6280,25120,56520}

availability

Se =

vacuumlZlng

{1 00,200,500,1 OOO}

(unit:

vacuum degree separately III 0,

So
Vacuum pump

pressure

P=

(atm),

namely

the

Taking

target

III 00, III 000 atmosphere

target

{10133,1013.3,l01.33}

Lis);

speed

pressure

in

the

tube

(unit: Pa). By formula (4), we

can calculate the vacuumizing time at different cases (as
Fig.1 Schematic oftaking out air from ETT system

Po
v
t=-lnSe
P
In formula

(5), Po

shown in TABLE 1, TABLE 2 AND TABLE

(5)

3).

TABLE 1. VACUUMIZING TIME FOR OPERATION VACUUM I/IOATM
IN ETT TUBE (MINUTE)

is the atmospheric pressure intensity

�

100

200

500

1000

2

2410.0

1205.0

482.0

24l.0

4

9640.2

4820.1

1928.0

964.0

6

21690.5

10845.2

4338.1

2169.0

D(m)

outside the ETT tube. We can see that the vacuumizing time is
directly proportional to the EIT tube volume, inverse ratio to
the availability vacuumizing speed.

TABLE 2. VACUUMIZING TIME FOR OPERATION VACUUM 1/100
ATM IN EIT TUBE (MINUTE)

247

�

100

200

500

1000

2

4819.9

2410.0

964.0

482.0

4

19279.6

9639.8

3855.9

1928.0

6

43379.1

21689.6

8675.8

4338.1

TABLE 4. VACUUMIZING TIME FOR OPERATION VACUUM 1110

D(m)

ATM IN EIT AIRLOCK (MINUTE)

�
2

TABLE 3. VACUUMIZING TIME FOR OPERATION VACUUM 111000
ATM IN EIT TUBE (MINUTE)

�

100

200

500

1000

2

7230.3

3615.2

1446.1

723.0

4

28921.5

14460.7

5784.3

2892.1

100

200

500

1000

24.10

12.05

4.82

2.41

D(m)

4

96.40

48.20

19.28

9.64

6

216.90

108.45

43.38

21.69

TABLE 5. VACUUMIZING TIME FOR OPERATION VACUUM 11100

D(m)

ATM IN EIT AIRLOCK (MINUTE)

�

100

200

500

1000

2

48.19

24.10

9.64

4.82

Further more, supposing the interval space 2km between

4

192.97

96.39

38.55

19.28

two contiguous pump stations, tube diameter 3m, availability

6

433.79

216.89

86.75

43.38

6

65073.4

vacuumizing

speed

32536.7

1000Lls,

by

13014.7

the

D(m)

6507.1

software

Matlab

simulation computing, we can get the relation curve between
TABLE 6. VACUUMIZING TIME FOR OPERATION VACUUM 111000

vacuum degree and vacuumizing time ofETT.

ATM IN EIT AIRLOCK (MINUTE)

1BOO ,---,---,-----,,--,1600

.�

100

200

500

1000

D(m)

Basic Parameters:
1.0n8 vacuum pump station every 2km;
2.Round En tube with diameter 3m;
3.Availability vacuumizing speed olthe
vacuum pump station 8e=1000Us.

c

�

�

1200

2

72.30

36.15

14.46

7.23

4

289.21

144.60

57.84

28.92

6

650.73

325.36

130.14

65.07

=
c

1

1000

->

800

.

TV.

CONCLUSIONS

According to the above analysis and calculation, we can
get some conclusions as following:

600

(1) Vacuumizing time of ETT system is direct ratio to the

400 O'----1,-:: 0"-=00,---2:-:cO0
"-= 0,---30
:-:c 0"-=0

100
::-:' 00
4c::'00'-=0,---5""00:-:c0,---6c::'00:-:c0----=7:::" 00:-:c0----=S-='00:-:c0- ---=g-="00C:-0 '--Target pressure intensity 01 En tube in operation (Pa)

square of the tube diameter, therefore, with the precondition to

-

meet the transportation demand, it is useful approach for
shortening vacuumizing time to reduce ETT tube section

Fig.3 Relation between vacuum degree and vacuumizing time ofETT in

diameter as possible.

operation

(2) Vacuumizing time ofETT system is inverse ratio to the
B.

Calculating vacuumizing time of the airlock

availability vacuumizing speed of the vacuum pumps, namely
availability

Airlock is a transition space for Maglev int%

Suppose the airlock length 20m and ETT tube diameter

D:::

{2,4,6}

target

::: {lOO,200,500,lOOO}

vacuum

vacuumizing time

(3) The interval space between two contiguous vacuum

(unit: m), then the relative loading volume of

pump stations is direct ratio to the vacuumizing time, namely

{314,1256,2826}

the interval space more small, vacuumizing time shorter.

(unit:

in ETT tube. Vacuumizing time changes not too when the

the airlock vacuum pump is V:::
(unit:
3
m ); Taking the availability vacuumizing speed of the vacuum
pump Se

vacuumizing speed bigger,

shorter.

ut ETT tube.

Lis);

degree separately 1110,

atmosphere pressure (atm). By the formula

Taking the

11100,

(4),

(4)

vacuum degree in the tube is 0.1�O.OO1 atm; the required

111000

vacuumizing time would go up fleetly when the vacuum

we can get

vacuumizing time at difference cases as shown in TABLE

Vacuumizing time is exponential to the vacuum degree

degree in the tube is more added.

4,

By the above calculation example, for the ETT system

TABLE 5 AND TABLE 6.

with the tube diameter 2m, pump stations interval space 2km,

248

required vacuum degree O.latm, availability vacuumlZlng
speed of the vacuum pump station 1000 Lis, the vacuumizing

REFERENCES

time from normal pressure to required vacuum degree will be
about 241 minutes, and the vacuumizing time for the relative
airlock

with

length

20m

will

be

7.23

minutes.

Such

vacuumizing speed is too slow for the transportation which

[1]

http://www.et3.com. 2011-5-10

[2]

Zhang Yaoping, Daryl Oster. 2004. A New Industrial Era Coming---­
Primary Dialogue on Evacuated Tube Transportation [M]. Beijing:
Tsinghua University Press.

has been pursuing high speed and convenience, thus it is
necessary to design and manufacture vacuum pumps or

[3]

Zhang Yaoping. Evacuated Tube Transportation and Vacuum Industry

[4]

Da Daoan. Vacuum Design Manual [M]. Beijing: National Defence

[5]

Zhao Jijiu, Yin Zhaoshen [M]. Partical Accelerator Technology. Beijing:

Development [.I]. Shengyang: Vacuum, 2006. 43(2): 56-59.

vacuum pump stations with vacuumizing speed much more
than 1000 Lis. In addition, the interval space between two

Industrial Press, 1991.

contiguous vacuum pumps should be less than 2km, maybe
lkm better.

Higher Education Press. I "ed, November 2006, p.241.
[6]

Gao Benhui, Cui Suyan [M]. Vacuum Physics. Beijing: Science Press.
1,\ ed, December 1983, p. 209.

[7]

ACKNOWLEDGMENT

Wang Yuzhi. Vacuum Technology [M]. Chengdu: Sichuan People Press,
1981.

This work is supported by National Natural Science
Foundation of China (Project No.: 50678152), and Scientific
Plan Fund of Shaanxi Province (No. 2009K09-24).

249