The Revolution in Jet Fan Design

Transkript

1 The Revolution in Jet Fan Design The Revolution in Jet Fan Design

2 Basic Jet fan principle Air flow forced by: shock impulse of the jet fan airstream Relation of thrust T (jet fans) and pressure Dp (axial fans)

3 Basic laws of physics in tunnels A short explanation: c z piston Dp wind ζ in ζ friction ζ out p T total = ( ζ in total, required, gros + ζ = friction with p p total + ζ piston dyn A tunnel + ζ out ρ = c 2 2 ) = p ρ 2 dyn + p Q A 2 wind

4 Losses by tunnel design Wall effect Impulse loss - Wall effect (Kempf) Distance of fan axis to one boundary ~9% losses ~13% losses ~15% losses D Z Traditional Jet Traditional Jet Traditional Jet Z 1.5 Z Z = = 1. 0 = 0. 7 D D D Thrust, still air Thrust, incl. losses Losses

5 Losses by tunnel design Exit portal profil Impulse loss - Profile at portal Profile Types at Exit Portal Picture Resistance Coefficient Uniform z = 1 Parabolic z = 1.55 to 2.0 Asymmetric z = 3.67 acc. to I.E. Idelchik - Handbook of hydraulic resistance

6 Increasing efficiency by reducing avoidable losses Traditional Jet To reduce losses by different friction effects, guide vans are often used to direct the airstream towards the tunnel centre and away from the ceiling or walls. But guides vanes have at least negative impact on the generated sound level. There for Witt & Sohn considered bending the silencers at an angle of 5-10 The Banana Jet design was created!

7 Increasing thrust efficiency Technical Increased thrust efficiency in the tunnel Coanda Kempf Traditional Jet Backgroung velocity by reduction of losses

8 Banana Jet advantages regarding the wall effect Reduction due to No wall effect (depending on type of installation) Loss of thrust, Traditional Jet 1 1 K 5-15% 1 1 K 15-25% K 20-35% 3 Loss of thrust, ~0% ~0% ~2-5% Reduction of required thrust - (5-15%) - (15-25%) - (18-30%)

9 Background velocity - Effects on the jet impuls Impulse loss - Background velocity Reduces gross outlet velocity (to increase average tunnel speed) c BG c BG c out, g c out, n Gross outlet vel. c out, g = Net outlet vel. c out, n - Background vel. c BG

10 Background velocity - Effects on the jet impuls Different profiles: Traditional Jet Fan Inhomogeneous air profile High velocity at wall/ ceiling Fan Homogeneous air profile Reduced velocity at wall/ ceiling (~80%) tunnel ceiling Traditional Jet road air velocity [%] tunnel ceiling road air velocity [%]

11 Effects - Geometry Losses by tunnel (case-to-case) Geometry e.g. curves, slope Obstacles close to the jet fan outlet niches, traffic signs, etc. Traditional Jet

12 Effects - Geometry The : NO losses by wall effect Reduced losses by obstacles

13 Effects- Portal Impulse loss - Profile at portal: Short distance of last jet fan battery to exit portal (< 100m) due to cost savings for cables tunnel ceiling tunnel ceiling portal portal Traditional Jet road road z = 1.08 to 1.25 z = 1.02 to 1.05

14 Why BJ gains higher efficiency - First summary 5 main effects (1) explain higher efficiency (2) : Flow/ friction losses due to Coanda effect No Impulse losses due to Background velocity Wall effect (Kempf) Tunnel discharge profile at portal Influence of tunnel geometry (1) no congestion, no piston, no chimney effect (2) compared to Traditional Jet Fan

15 Increasing efficiency Saving money Commercial aspect: Higher efficiency of the TVS (Tunnel Ventilation System): η TVS c ~ Σ BG P el Smaller fans or lower number of fans can be used Lower costs of investment, installation, operation, maintenance

16 Reducing electrical consumption INPUT: P el Traditional Jet INPUT: P el, TJ > P el, BJ OUTPUT: c BG, TJ = c BG, BJ INPUT: P el c BG η = η TVS OUTPUT INPUT c BG ~ P el η TVS, BJ > η TVS, TJ

17 Test in Tunnels - Results Comparative tests in 3 tunnels Uznaberg West Tunnel Switzerland Krohnstieg Tunnel Germany Collombey Tunnel Switzerland

18 Test in Tunnels - Results Test set-up: Fan : Modified to Traditional Jet Fan:

19 Test in Tunnels - Results Test set-up: same quantity same size same INPUT same performance

20 Test in Tunnels - Results Test procedure: Grid-measurement of air velocity 1) 1) acc. to Log-Tchebycheff-Method

21 Test in Tunnels - Results Hypothesis: With same INPUT the fan has higher effective thrust, i.e. produce higher tunnel air velocity, i.e. provides higher OUTPUT

22 Test in Tunnels - Results Results of air velocity profiles (3D) Ref. chart: velocity [m/s] Fan

23 Test in Tunnels - Results Results of performance in tunnel Tunnel air velocity c BG in m/s Uznaberg Collombey Effective thrust T in % of Traditional Jet Fan Trad. Jet Trad. Jet Krohnstieg Trad. Jet

24 Test in Tunnels - Results Reference: Bypass Schmerikon Location Switzerland, Kanton St. Gallen Length 1 x 1318 m + 2 x 940 m Traffic bidirectional + unidirectional Realized 2003 Tests Banana effect proven by independent measurements Design schedule Realized with Quantity of fans Thrust per fan N 966 (100%) 770 (80%) Thrust, total N (100%) (80%) P electric per fan kw P electric total kw (100%) (85%) Tunnel average velocity % Total thrust tunnel % Source: Witt & Sohn analysis

25 Test in Tunnels - Results Reference: Tunnel Aubing Location Motorway ring (Munich) Length 2 x 1950 m Traffic unidirectional Realized Tests Banana effect proven by independent measurements Design schedule Realized with Quantity of fans - 60 (100%) 48 (80%) Thrust per fan N Thrust, total N (100%) (80%) P electric per fan kw P electric total kw 1254 (100%) 1003 (80%) Tunnel average velocity % Total thrust tunnel % Source: Witt & Sohn analysis

26 CFD-Simulation Results vector diagrams 6.T/B : Round tunnel profile, 1 centre, size T/B : Square tunnel profile, 1 centre, size 1250

27 CFD-Simulation Results air velocity, empty tunnel 1.T/B : Square tunnel profile, 1 centre, size 710: TJ BJ 4.T/B : Square tunnel profile, 2 corner, size 710: TJ BJ 9.T/B : Square tunnel profile, 1 corner, size 1250: TJ BJ

28 CFD-Simulation Results air velocity, traffic jam 1.T/B : Square tunnel profile, 1 centre, size 710: TJ BJ 2.T/B : Square tunnel profile, 1 corner, size 710: TJ BJ Losses by cars: % -6% (compared to empty tunnel)

29 CFD-Simulation Prediction for -advantage Configuration Preliminary Thrust improvement [%] 1 towards TJ at different tunnel air speeds [ m / s ] 2 m / s 3 m / s 4 m / s 5 m / s 6 m / s 7 m / s 8 m / s 45 % 47 % 50 % 52 % 55 % 57 % 60 % 41 % 43 % 45 % 47 % 50 % 52 % 55 % 38 % 41 % 44 % 47 % 50 % 53 % 56 % 35 % 38 % 40 % 43 % 45 % 48 % 50 % 33 % 35 % 37 % 39 % 42 % 45 % 48 % 27 % 29 % 32 % 34 % 37 % 39 % 42 % 19 % 21 % 23 % 25 % 28 % 31 % 34 % 15 % 18 % 21 % 24 % 27 % 30 % 33 % 1 tolerances: + /- 10% Actual measurements of tested tunnel Bold Results of CFD analysis Rest Predicted values

30 CFD-Simulation Preliminary Configuration Reasons for -advantage Losses by the 3 sides of the niche reduced Losses by the 2 sides of the corner reduced Niche acts as BJ Coanda effect reduced BJ reduces interaction between both fans Less interaction of both fans Niche acts as BJ Coanda effect reduced Air is not travelling down the side walls Mainly Coanda effect Coanda effect + less interaction of both fans

31 Commercial benefits Cost SAVINGS Case A: Smaller size / same quantity of fans Less CONSTRUCTION costs Less INVESTMENT costs Less RUNNING costs Smaller POWER SUPPLY PLANT

32 Commercial benefits Cost SAVINGS Case B: Less quantity/ same size of fans Less CONSTRUCTION costs Less INVESTMENT costs Less RUNNING costs Smaller POWER SUPPLY PLANT Less INSTALLATION costs Less MAINTENANCE costs

33 Benefits General Contractor Cost SAVINGS: 1. CONSTRUCTION: Smaller cross section/ excavation No performance losses by Obstacles (e.g. traffic signs, lights) Use of niches!!!! Standard Jet CAR HDV BANANA Jet with niches CAR HDV

34 Benefits E&M Contractor 2. INVESTMENT: Smaller size or reduced quantity (FANS and CABLES) in % of total costs Fans (2) Uznaberg Collombey Krohnstieg Savings for Fan & Cables ~ 30 % Uznaberg Standard Jet ~ 13 % ~ 15 % ~ 22 % ~ 34 % ~ 10 % ~ 11 % ~14 % ~ 23 % Cables (1) Collombey ~ 41 % ~ 29 % Krohnstieg ~ 25 % ~ 18 % (1) E90-cable costs: /m (incl. installation) (2) discount rate: 10%

35 Benefits E&M Contractor 2. INVESTMENT: Shorter/smaller SILENCER Same total SOUND level(*) Table: Sound pressure levels, 3m, 45, ff [db(a)]: Savings for shorter silencers ~ 15 to 40 % w/o. silencers silencer s attenuation increased level (battery) with silencers ~93 2.0D: (1) ~86 ~92 1.5D: (1) ~86 ~91 1.5D: (1) ~86 (*) : with same total thrust (1) : experienced values

36 Benefits Client 3. RUNNING costs: Less unit power consumption or reduced quantity in % of total costs Uznaberg Collombey Standard Jet Savings for Running costs ~ 30 % ~ 53 % ~ 44 % ~ 38 % ~ 33 % Krohnstieg ~ 53 % ~ 35 % (1) basis: operation time: 1000h p.a. energy cost: 0,1 kw/h

37 Benefits all parties Total SAVINGS (investment + running) running costs cable costs investment costs Traditional Jet Traditional Jet Traditional Jet Savings of 20 years Total Project Costs ~ 30 %

38 Benefits E&M Contractor 4. Installation (mounting): E.g. directly under ceiling No wall effect (Kempf) ceiling Traditional Jet ceiling Less space consumption Simple mounting structure Less quantity of fans (Case B)

39 Benefits Environment 5. Environment: Pollution: 550g CO 2 / kwh (1) (or higher) ~ 30 % CO 2 -reductio (in line with reduced power consumption) Fulfilment of latest UN-report, part 3 (climate crisis) (1) based on 60% fossil, 30% nuclear, 10% renewable (German Energy Mix/ Power Generation Standards)

40 References 6. References - worldwide: Country Tunnels Country Tunnels Australia 4 Russia 1 Austria 1 Singapore 1 Chile 3 Spain 5 China 2 Sweden 1 France 4 Swizerland 8 Germany 13 U.A.E. 1 Norway 9 UK 1 Portugal 1 Venezuela 1 Total

41 Banana Jet advantages - Summary 20-60% higher effective thrust with Banana Jets (same fan size) Easy selection Comfortable integration into tunnel concept Great benefits (cost savings) for all parties Helps to reduce CO 2 Proven in over 50 tunnels WORLDWIDE Patent No