Tunnel Ventilation System Design and Air Quality. Peter Gehrke and Andrew Purchase

Transcription

1 Tunnel Ventilation System Design and Air Quality Peter Gehrke and Andrew Purchase

2 Summary of Our Input Primarily - how does the choice of in-tunnel criteria and operational strategies affect the system design and required infrastructure? This affects: Exhaust/Supply fan capacity Numbers and size of jet fans Requirements for smoke ducts Requirements for ventilation tunnels Longitudinal or transverse ventilation Power usage Capital and maintenance costs

3 Background Experience - Road Tunnel Design M5 East Sydney (4km, design review) Cross City Tunnel Sydney (2km, parallel design) Lane Cove Tunnel Sydney (3km, tender design) Eastlink Tunnel Melbourne (2km, design reviewer) Clem7 (North South Bypass Tunnel) Brisbane (5km, system design) Airport Link Tunnel Brisbane (6km, system design) PR53 Highway Tunnel Puerto Rico (1km, system design) Victoria Park Tunnel Auckland (460m, system design)

4 Tunnel Ventilation System Design Factors Considered Vehicle emission factors Portal emissions Smoke control requirements Carbon monoxide (CO) Oxides of nitrogen (NO x /NO 2 ) Carbon Dioxide (CO 2 ) Sulphur Dioxide (SO 2 ) Visibility - particulate matter (PM) Volatile Organic Compounds (VOCs) Vehicle heat - temperature In-tunnel air velocity Controllability

5 Vehicle Emission Factors In Europe and Australia, emission factors are determined from PIARC tables correlated to vehicle classes. Post construction measurements indicate that PIARC, as applied in Australia, adequately predicts emissions. New Zealand has a Vehicle Emissions Prediction Model (VEPM). VEPM documentation outlines that the model is best suited for 1km resolution over a period of 1 hour and is not suitable for predicting instantaneous emissions. Emissions as a function of speed are provided but not as a function of grade. Tunnel ventilation design considers short time scales and also grades. VEPM applied to tunnels needs consideration. Risk that conservative emission inputs results in overdesign of systems.

6 Portal Emissions No portal emissions criterion eliminates pollutant dispersion at portals with exhaust fans and stacks required to disperse emissions. Consideration should be undertaken for individual projects. Some portals can effectively disperse pollutants PIARC/M5 East experience. Typically the piston effect can generate sufficient airflow for ventilation. For no portal emissions this often results in running jet fans against the traffic flow. There is significant energy usage required. From a sustainability perspective, consideration should be given to allowing portal emissions at night or when traffic volumes are low. Allowing portal emissions during traffic incident can in some cases reduce system capacity

7 Smoke Control Smoke control requirements can set ventilation sizing Emissions affects operating and capital costs (portal emissions) Smoke control affects capital costs (essential, but rarely used) Strategy Longitudinal or a smoke exhaust duct Operator response and traffic management Design fire size specific for each tunnel Vehicle types (cars, trucks, DGVs) Concession for deluge Quantify appropriate design fire size by risk assessment (don t just select the biggest fire). Design fire size affects number of jet fans, sizing of exhaust fans and ventilation pathways.

8 Background Experience - Road Tunnel Design System Examples Australian Road Tunnels Tunnel Geometry/System Supply/Exhaust (m 3 /s) 1 Jet Fans Power (MW) 2 In-Tunnel Criteria Eastern Distributor Sydney M5 East Sydney Cross City Sydney 3 Lane Cove Sydney 3 1.6km, twin bore, 3 lanes Stacks at each tunnel end Portal emissions allowed off peak 4km, twin bore, 2 lanes One centre stack Circulatory ventilation No portal emissions 2.2km, twin bore, 2 lanes Stack at one end Crossover ventilation Exhaust tunnel for traffic incidents No portal emissions 3km, twin bore, 3 lanes Stacks at each end Mid-tunnel supply /exhaust with ventilation tunnel No portal emissions 960 exhaust 46 (60kW) supply 1000 exhaust 1000 crossover 800 exhaust 400 crossover 450 exhaust tunnel 1100 supply 2600 exhaust 119 (mostly 12 45kW) 54 (60kW) (75kW) Notes: 1. Flow values are rounded installed capacity. Not all this capacity may be used at one time. 2. Power figures are estimated totals. 3. In-tunnel CO criterion was made more stringent by RTA based on M5 East air quality perceptions 17 CO 100ppm peak CO 87ppm 15 min NO 2 1ppm Vis 0.005m m -1 CO 87ppm 15 min NO 2 NA Vis 0.005m m -1 CO 87ppm 15 min CO 50ppm 30 min NO 2 1ppm? Vis 0.005m m -1 CO 87ppm 15 min CO 50ppm 30 min NO 2 1ppm? Vis 0.005m m -1

9 System Examples Australian Road Tunnels Tunnel Geometry/System Supply/ Exhaust (m 3 /s) 1 Jet Fans Power (MW) 2 In-Tunnel Criteria Eastlink Melbourne 2km, twin bore, 3 lanes Stacks at each end No portal emissions 1500 exhaust 120 (75kW) 17 CO 150ppm peak CO - 50ppm 15 min NO 2 1.5ppm Vis 0.005m m -1 Clem7/North South Bypass Brisbane 4.8km, twin bore, 2 lanes Stacks at each end Smoke exhaust duct No portal emissions 1500 exhaust 1000 extra exhaust vent available via (40kW) 6 smoke smoke duct CO - 70ppm flowing traffic CO 90ppm slow traffic NO 2 1ppm Vis 0.005m m -1 Airport Link Brisbane 6km, twin bore, 2/3 lanes Stacks at each end plus central stack Smoke exhaust duct No portal emissions 2300 exhaust 800 extra exhaust available via smoke duct 170 (30kW) 10 vent 9 smoke CO - 70ppm flowing traffic CO 90ppm slow traffic NO 2 1ppm Vis 0.005m m -1 Notes: 1. Flow values are rounded installed capacity. Not all this capacity may be used at one time. 2. Power figures are estimated totals. 3. In-tunnel CO criterion was made more stringent by RTA based on M5 East air quality perceptions

10 Effect of In Tunnel Criteria CO, NO x and visibility (PM) considered. A typical tunnel used as a base single bore long tunnel, longitudinally ventilated with no portal emissions. Criteria modified to estimate relative change in ventilation requirements - numbers of jet fans and exhaust stack capacity. Vehicle emissions were based on Australian factors (cleaner fleet than NZ), however relative changes would still be valid. Figures based on assessing requirements for all flowing traffic speeds. Traffic incidents causing prolonged exposure are not considered.

11 Carbon Monoxide (CO) CO criterion Design driver Exhaust rate (m 3 /s) Number of jet fans Estimated power (MW) 90ppm Max 5km/h ppm Max 5km/h ppm Max 5km/h ppm 30min exposure (excluding traffic incidents) 5km/h Notes: 1. Approximate values are provided to assess relative changes. 2. Power figures are estimated totals. 3. Only one tube assessed. 4. Fire cases and controllability not assessed.

12 Nitrogen Dioxide (NO 2 ) and Visibility NO 2 criterion Design driver Exhaust rate (m 3 /s) Number of jet fans Estimated power (MW) 1.5ppm Max 20-40km/h ppm Max 20-40km/h ppm Max 20-40km/h Visibility Criterion Design driver Exhaust rate (m 3 /s) Number of jet fans Estimated power (MW) 0.007m -1 20km/h m km/h m km/h Notes: 1. Approximate values are provided to assess relative changes. 2. Power figures are estimated totals. 3. Only one tube assessed. 4. Fire cases and controllability not assessed.