Banana JetBanana Jet®®A revolutionary new concept in jet fan design

A revolutionary new concept in jet fan design

PatentPatenteded 10506841050684

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• Banana JetBanana Jet®® has been tested in 3 road tunnels

• Banana JetBanana Jet®® generated 30 – 45 % more thrustthan traditional jet fans

• The hypothesis is that 3 separate effects explain the better performance of Banana JetBanana Jet®®

• All stakeholders get major benefits by using Banana JetBanana Jet®® technology

50 – 75 %100 %Total*

15 – 30 %15 – 30 %Inlet / outlet portal losses

2 – 17 %2 – 20 %Losses in bends, installations, road signs, corners, lamps, etc.

0 – 5 %

0 %0 %

2 – 5 %

5 – 35 %

5 – 15 %15 – 25 %20 – 35 %

Wall effect / Impulse loss (acc. Kempf)- Roof / Wall mounting- Corner mounting- niche mounting

5 – 17 %8 – 20 %Background velocity losses

25 – 40 %30 – 50 %Wall friction losses due to Coanda effect

With Banana Jet®Traditional Jet Fans

* assuming an empty tunnel; traffic jam or piston effect not taken into account

Banana JetBanana Jet®® will generate 25 – 50 % more thrust

Losses for Traditional and Banana JetBanana Jet®® fans in % of total losses

Source: Witt & Sohn analysis

Banana JetBanana Jet®® is a major opportunity for all stakeholders

Advantages of Banana JetBanana Jet®®

• 30 – 45 % lower energy consumption for same effective thrust

• Directional, i.e. niche losses or other obstructions can be minimized

• Lower purchase price of fans for same effective thrust

• Reduced cable diameters/shorter cables and other installation savings

• Existing tunnels can easily be retrofitted with Banana JetBanana Jet®® technology

• Lower sound power level for same effective thrust

•• Banana JetBanana Jet®® optimises the air distribution in the tunnel cross section

• Easy to select new fans with 30 – 45 % higher effective thrust

The cost of cables for tunnel jet fans are considerableCable cost in €/m

Rated current in A

Emergency power supply

Switch gear

F90 cable (fire rated)

Normal cable

Assumption:Average cable length200 m

120

100

80

60

40

20

025 50 75 100

102

82

62

33

Source: Witt & Sohn analysis

Banana JetBanana Jet®® generate significant savings to the Installer and the Operator

Assumptions: Operating time 1000 hours/year, electricity cost € 0,1 per kWh, 10 % discount rateCost of el. Cable 25 – 58 €/m for cables incl. Installation and emergency power supply.

Trad. Norm. Banana Jet® Trad. Norm. Banana Jet® Trad. Norm. Banana Jet®

Operating cost

Cable cost

Purchase price

Source: Witt & Sohn analysis

Comparison of Life cycle cost with Traditional and Banana Jet®

The additional losses in a traffic jam with Banana JetBanana Jet®® are negligable

Traditional Jet Fan

Banana Jet®

Assumption: Outlet speed 33.5 m/s, Tunnel height 5.5 m

Difference in thrust in the traffic:Trucks (15 % of all vehicles): 0,3 – 0,5 %Cars : 0,5 – 1,0 %

Comparison air speed of Banana Jet® vs. Traditional Jet Fan

Source: Recknagel, Sprenger, Schrammeln

Trucks

Cars

33,5 m/s

23,2 m/s

23,2 m/s17,8 m/s

17,8 m/s

14,4 m/s

14,4 m/s

12,1 m/s

12,1 m/s

10,5 m/s

10,5 m/s

9,2 m/s

9,2 m/s

8,2 m/s

8,2 m/s

7,4 m/s

7,4 m/s

6,7 m/s

6,7 m/s

5,9 m/s

Jet Fan

[m]5

4

3

2

1

0

0 2 4 6 8 10 12 14 16 18 20 [m]

The Quick selection makes it easy to select Banana JetBanana Jet®®

57,02390184059,426002000160043,91860143047,121301640140032,2125596542,521851680125033,61695130534,317701360112025,0117590527,013801060100017,571555019,588568090012,345034513,654542080015,893071515,995073071012,271054512,27105456308,44303308,44253255606,02752106,43102405002,680602,68060400

m³/sNNm³/sNNmmFlow rateEquiv. thrustNominal thrustFlow rateEquiv. thrustNominal thrustSize

Asymmetric Banana Jet® Symmetric Banana Jet®

Banana Jet® quick selection table*, 50 Hz

*Assumption: 30 % improvement in effective thrust.

Comparative measurements were carried out in 3 tunnels

Uznaberg West Tunnel

Switzerland

Collombey Tunnel

Switzerland

Krohnstieg TunnelGermany

Transition pieces were used to make Banana JetBanana Jet®® into traditional jet fans

Banana Jet®

Traditional jet fan

Fans prepared for measurements in the Collombey tunnel

Banana JetBanana Jet®® generated 30 - 45 % more thrust and . . .

Comparison of air speed and thrust in the tunnels Banana JetBanana Jet®® vs. Traditional jet fan

Collombey Tunnel

Uznaberg Tunnel

Krohnstieg Tunnel

Source: HBI & Witt Measurements Speed in m/s Relative thrust in %

. . . the air speed distribution showed a marked improvement

-3.0

-2.0

-1.0

0.0

1.02.0

3.0

4.0

5.0

6.0

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8.0

9.0

10.011.0

12.0

20 m, Banana Jet

-2.0

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5.0

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20 m, Trad. Jet Fan

-2.0

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40 m, Banana Jet

-2.0

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8.0

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40 m, Trad. Jet Fan

-2.0

-1.0

0.0

1.0

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4.0

5.0

6.0

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8.0

9.0

60 m, Banana Jet

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

60 m, Trad. Jet Fan

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

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6.0

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8.0

120m, Banana Jet

-1.5

-0.5

0.5

1.5

2.5

3.5

4.5

5.5

6.5

120 m, Trad. Jet Fan

Example: Uznaberg West tunnel, air speeds at the cross section at different distances behind the fans

Major differences:- Lower average air speed with trad. fans - High air speed along the roof with trad. fans- „Hole“ in the middle of the tunnel with trad. fansSource: HBI Measurements, Uznaberg West Tunnel

The hypothesis is that 3 effects give Banana JetBanana Jet®® the advantage over traditional jet fans

• “Wall effect“, also called “Kempf principle“• The jet will touch the ceiling at high speed just a few metres behind the fan• Mr. Kempf determined in the 60‘s a correlation between the proximity to theceiling/ wall and the effective thrust a jet fan could generate

• The plots of the air speed along the tunnel clearly show that Banana JetBanana Jet®® fans have a much lower air speed and therefore no significant losses due to this effect

• Coanda effect• The Coanda effect makes the jet becoming „glued“ to the ceiling/ wall•• Banana JetBanana Jet®® generate lower air speed along the perimeter of the tunnel,

so the friction losses are lower

• Background velocity correction• The background velocity reduces the effective increase in air speed and

therefore the effective thrust• The thrust for Banana JetBanana Jet®® must be corrected less than for traditional jet fans,

because the air speed under the ceiling, even at large distances, is lower.

The jet will touch the wall/ceiling just a few meters behind the fan

Wall effect

Depending on the proximity to the wall the effective thrust is reduced

Kempf formula :

Wall effect

1.27dz0.144

dz0.0192xK

2

+−

=

DZDZDZ

Illustration and formula of Kempf‘s wall effect

Complicated geometries create large thrust losses for Traditional Jet fans

Illustration of expected losses in thrust with different mounting positions

Roof or wall mounting Corner mounting Mounting in niches

Thrust reduction in Trad. Jet fans Thrust reduction in Banana JetBanana Jet®® fans

5 – 15 %~ 0 %

15 – 25 %~ 0 %

20 – 35 %2 - 5 %

Wall effect

Source: HBI Measurements, Uznaberg West Tunnel

Significant air speed profile differences behind trad. jet fans and Banana JetBanana Jet®®

Air speed at different heights at 20, 40 ,60 and 120 m behind the jet fans

Source: HBI Measurements, Uznaberg West Tunnel

Traditional Jet Fans Banana Jet® Fan

Tunnel height in m Tunnel height in m

20m- 40m- 60m- 120m- of distance behind the fans

Average speedBanana jet®

Average speedTrad. Jet fan

Wall effect

Banana JetBanana Jet®® has maximum speed at 2/3 height of the tunnel

Negligible higher friction in case of traffic jam with Banana JetBanana Jet®®

Comparison of average air speed distribution

Source: HBI measurements, Uznaberg West tunnel

Wall effect

Assumption: same average airspeed achieved

The Coanda effect makes the jet becoming „glued“ to the ceiling/ wall

Turbulence and low pressure areas provide the „glue“

Schematic illustration of the Coanda effect Coanda effect

Banana JetBanana Jet®® generate lower air speeds along the walls of the tunnel

Coanda effect

Source: HBI measurements Uznaberg tunnel, Witt calculation

Air speed around the perimeter of the tunnel

Ai r

spee

d in

m/s

Trad. Jet Fan Banana Jet®

Comparison of air speeds

Averagenormalized

Result:Much less

frictionlosses inthe tunnel

Assumption: Same average airspeed achieved

The background velocity reduces the effective air speed and therefore the effective thrust

Nominal air speed generated by the jet fan

Effective air speed generated by jet fan

Background velocity

Background velocity

The thrust for Banana JetBanana Jet®® must be corrected less than traditional jet fans

Air speed at 120 m behind the fans (20 m in front of the next pair of fans) Banana Jet® compared to traditional Jet Fan

Source: HBI measurements, Uznaberg West tunnel

Average air speed

in the tunnel

Background velocity

Banana JetTM

Trad. Jet Fan

Air speed in m/sAssumption: Same airspeed assumed in the tunnel

A simple calculation method means that Banana JetBanana Jet®® can easily be selected by the user

• The measurements in the 3 tunnels gave clear indications to whatextent each of the 3 effects contributed to the increase in effective thrust.

• A simple calculation method could be developed: No wall effect and the air speed for the calculation of friction and background velocity losses at 80 % of the average required air speed.

• Using this simple formula gave a very good prediction as to the actualair speed in the 3 tunnels studied.

• When extending this calculation method to standard tunnels, it can be seen that virtually all tunnels can significantly benefit from Banana JetBanana Jet®® technology.

Banana JetBanana Jet®® eliminates the wall factor and reduces the friction and background velocity effects

Source: HBI & Witt Measurements

Trad. Jet Fan Banana Jet® Trad. Jet Fan Banana Jet® Trad. Jet Fan Banana Jet®Trad. Jet Fan Banana Jet®

Analysis of losses with the two technologies

The measurements suggest a simple calculation method

Suggested calculation method

Step 1: Banana JetBanana Jet®® generate 30 % more effective thrust(First approximation)

Step 2: Total required thrust can be calculated by assumingBanana JetBanana Jet®® has

- No wall effect impulse loss (5 – 35 % more thrust)

- 20 % lower average air speed (for background velocitycorrection and wall friction loss)

All standard tunnels can significantly benefit from Banana JetBanana Jet®®

technology

Source: Witt simulation

Simulation of increased thrust in various tunnel types as a function of required air speed and tunnel length

Assumptions: Airspeed for calculation of friction and background velocity losses80 % of average air speed, no wall effect.

Tunnel typeFrition coefficentsAir speed in m/s 3 5 7 3 5 7 3 5 7Lenght in m

250 29% 30% 32% 25% 26% 28% 32% 33% 35%500 33% 34% 36% 30% 31% 33% 40 % (3) 41% 43%750 37% 38% 40% 33% 35% 36% 45% 46% 48%1000 40% 41% 43 % (1) 35 % (2) 37% 38% 48% 49% 51%1500 43% 45% 47% 38% 39% 41% 52% 53% 55%2000 42% 44% 46% 39% 41% 42% 54% 55% 57%3000 48% 50% 52% 41% 42% 44% 56% 58% 60%

"Country" tunnel, high fricitonWall: 0,025 Installations: 0,005

"Country"tunnel, low frictionWall: 0,015 Installations: 0,005

"Country" tunnel, medium fricitonWall: 0,015 Installations: 0,010

(1) Uznaberg (actual 47 %)(2) Collombey (actual 32 %)(3) Krohnstieg (actual 35%)