Flow Resistance of Fires in Road Tunnels - Validation (CFD Simulation and Experimental Investigation for ASTRA)

Reproduction of this report is only authorized if done in its entirety. This document consists of 29 pages. Page 1. TEST REPORT. TUNNEL FIRE TESTING Report number: 24-32301178 Petitioner reference: OST – Eastern Switzerland University of Applied Sciences CHE-205.856.647 MWST Made by: David Garcia Alvarez & Sinai Arguello Arias. Date: February 12th, 2025 P a g e 2 | 31 Contents 1. Introduction .............................................................................................................. 4 2. Testing Facilities........................................................................................................ 4 Test Tunnel. Main characteristics ..................................................................................... 4 3. Ventilation Systems. Longitudinal Ventilation ........................................................... 8 Passive Fire Protection System ......................................................................................... 8 Equipment ....................................................................................................................... 8 Data Acquisition and Control System ................................................................................ 8 Structure ......................................................................................................................................... 8 Data transmission ........................................................................................................................... 9 Central control station .................................................................................................................... 9 4. Fire Scenario ............................................................................................................. 9 Fire load ........................................................................................................................... 9 Fire location .................................................................................................................... 10 5. Initial conditions ..................................................................................................... 10 Tunnel Conditions ........................................................................................................... 10 Service Gallery Conditions ............................................................................................... 10 6. Instrumentation ...................................................................................................... 11 Air velocity measurement at pk. 522 ............................................................................... 11 Temperature measurement at pk. 522 ............................................................................ 13 Pressure drop measurement ........................................................................................... 13 Heat Release Rate (HRR) Measurement ........................................................................... 14 7. Instrumentation Diagrams ...................................................................................... 16 Overall Diagram .............................................................................................................. 16 Air velocity and temperature measurement at pk. 522 .................................................... 17 Measurement of pressure drop along the tunnel ............................................................. 18 8. Test Protocol ........................................................................................................... 19 Test 1 .............................................................................................................................. 19 Test 2 .............................................................................................................................. 19 Test 3 .............................................................................................................................. 19 P a g e 3 | 31 9. Results. ................................................................................................................... 20 Test 1 .............................................................................................................................. 20 Heat Release Rate of TEST 1 ......................................................................................................... 22 Test 2 .............................................................................................................................. 23 Heat Release Rate of Test 2 .......................................................................................................... 25 Test 3 .............................................................................................................................. 26 Heat Release Rate of Test 3 .......................................................................................................... 28 Annex 1: Intrumentation list. ............................................................................................ 29 Annex 2: HRR Intrumentation. .......................................................................................... 31 P a g e 4 | 31 1. Introduction This report details the works, equipment and measurements of air velocity, temperature, and pressure drop within the San Pedro de Anes Test Tunnel as part of the project "Strömungswiderstand von Bränden in Strassentunneln - Validierung" (Aerodynamic Resistance of Fires in Tunnels - Validation) directed by OST - Eastern Switzerland University of Applied Sciences and Riess Ingenieur GmbH. OST intended to carry out full scale fire tests at the San Pedro de Anes test tunnel in order to validate their CFD study proposing the following theories:  The tunnel fire causes a significant airflow resistance in the tunnel.  The airflow resistance consists of two contributions: A local pressure drop at the fire and an increased pressure drop downstream of the fire (due to temperature/density stratification).  The airflow profile downstream of the fire shows the velocity maximum close to the tunnel ceiling.  The temperature profile downstream of the fire resembles the velocity profile.  Extension of the thermally stratified flow. During the testing, measurements were taken at designated locations within the tunnel and service gallery. The following sections will present the methodology employed for the measurements, the data collected, and any observations made during the testing process. 2. Testing Facilities Test Tunnel. Main characteristics It is a false tunnel built in concrete, with dimensions equivalent to a two-lane road tunnel, and has two ventilation stations, a lower gallery for emergency and electrical services, and three emergency exits. It also has a removable false ceiling for reproducing different ventilation conditions. The main technical data are: Length: 600 m Width: 9.50 m Height: 8.12 m Cross-section (without ceiling): 66 m2 Minimum radius: 400 m Longitudinal gradient: 1 % Transversal gradient: 2 % Emergency gallery: 4 m width by 2.50 m height Emergency exits: 4 (one each 150 m) P a g e 5 | 31 Cross-section of the experimental tunnel P a g e 6 | 31 Test tunnel layout P a g e 7 | 31 South tunnel entrance with false ceiling installed and jet fans North tunnel entrance with jet fans P a g e 8 | 31 3. Ventilation Systems. Longitudinal Ventilation  6 jet fans of 45 KW (6 fans installed in the tunnel) Passive Fire Protection System The tunnel is equipped with a passive fire protection system consisting of a 5 cm layer of fire-resistant concrete (Meyco Fireshield from the BASF chemical company). This protection’s main characteristics are as follows:  Installed in the middle section of the test tunnel between pk. 335 and pk. 415  Allows for the execution of high-heat-release fires, with fires of over 200 MW having been carried out Equipment The tunnel also incorporates the following additional equipment:  600 m3 water storage tank.  150 mm diameter pressure pipe on the outside of the tunnel at pk. 300. Supplied by a pressure group working at a maximum pressure of 4 bar and with a capacity of 180 m3/h.  100 mm diameter pressure pipe inside the tunnel, with hydrants every 50 m. Supplied from different tanks and fed by a pressure group at 12 bar and with a capacity of 72 m3/h.  Spill collection system with a 50 m3 settling tank.  250 W luminaires every 15 m, on both sidewalls Data Acquisition and Control System The tunnel's data acquisition and control system is a crucial component of the facility, serving both to control and regulate various systems, including ventilation, fire suppression equipment, and lighting. Additionally, it acquires and records data and images during testing. Its main characteristics are: STRUCTURE The tunnel employs a decentralized system comprising 13 Monitoring and Control Stations (EMCs) strategically positioned within the service gallery at intervals of 40-50 meters. Additionally, two dedicated units oversee the control of the ventilation stations. All units maintain communication with the central control station via a closed-loop fibre optic ring. P a g e 9 | 31 Structure of the Monitoring and Control System DATA TRANSMISSION The communication system utilizes a robust and reliable fibre optic network, employing the MODBUS TCP/IP protocol for efficient data exchange between the EMCs and the central station. The additional unused fibre optic lines provide flexibility for future expansion or integration of other equipment. CENTRAL CONTROL STATION Redundant System based on two independent computers connected through a local network, with a 6 KVA uninterruptible power supply. SCADA-type software (iFIX professional) is used for data presentation and archiving. 4. Fire Scenario Fire load The fire load was designed to mimic a liquid spill on the road surface, according to the information provided by the CFD simulations performed by OST East Switzerland University with a Heat Release Rate defined between 5 MW. For tests 1 and 2, one diesel fuel pool of 4 m2 and dimensions 2500 x 1600 x 500 mm was used. For test 3 a second diesel fuel pool of 2.16 m2 sized 1800 x 1200 x 500 mm was added to increase the heat release rate to a maximum of 15 MW. The following amounts of fuel were used for each test:  Test 1: 147 l  Test 2: 150 l  Test 3: 230 l P a g e 16 | 31 7. Instrumentation Diagrams Overall Diagram Diagram of all the instrumentation installed along the tunnel. P a g e 17 | 31 Air velocity and temperature measurement at pk. 522 Grid installation at pk. 522 P a g e 18 | 31 Measurement of pressure drop along the tunnel Pressure drop measurement equipment in the tunnel and service gallery P a g e 19 | 31 8. Test Protocol The three tests were performed on June 12th of 2024 inside the San Pedro de Anes Tunnel. For each test, the time resolution of data acquisition was 1 s, following the protocol described in this section. Test 1 Table 7. Test 1 protocol STEP ACTIVITY 1 Measurements were taken without ventilation air flow for 7 min. 2 One jet fan, the closest to the south entrance, was switched on. 3 Data was recorded for 10 min to until the ventilation velocity was stable 4 The fuel pool was ignited and a fire of 5 MW approx. was produced. 5 The data was recorded until fire extinction. 6 End of the test. The tunnel ventilation was left on for 1.5 hours for air renewal purposes. Test 2 Table 8. Test 2 protocol STEP ACTIVITY 1 Measurements were taken without ventilation air flow for 5 min. 2 Two jet fans, the closest to the south entrance, were switched on. 3 Data was recorded for 10 min to until the ventilation velocity was stable 4 The fuel pool was ignited and a fire of 5 MW approx. was produced. 5 The data was recorded until fire extinction. 6 End of the test. The tunnel ventilation was left on for 1.5 hours for air renewal purposes. Test 3 Table 9. Test 3 protocol STEP ACTIVITY 1 Measurements were taken without ventilation air flow for 5 min. 2 Two jet fans, the closest to the south entrance, were switched on. 3 Data was recorded for 10 min to until the ventilation velocity was stable 4 The fuel pools were ignited and a fire of 10 -15 MW approx. was produced. 5 The data was recorded until it was decided to extinguish the fire. 6 End of the test. The tunnel ventilation was left on for 1.5 hours for air renewal purposes. P a g e 20 | 31 9. Results. The tables 5 to 7 detail the exact times at which each relevant event occurred during the testing process for all tests performed, they allow for the reconstruction of the testing sequence and identification of any potential inconsistencies that might arise during analysis. The graphs obtained after data processing are also shown in this section. Test 1 Table 10. Time stamps for Test 1. Event Time (hh:mm:ss) Star test1 9:07:31 Start ventilation 1 jet fan 9:14:37 Fire start 9:27:29 Fire extinguished 9:55:15 End test 1 10:01:24 Table 11. Length of Test 1 sections Test Section Length (min) Measurements without flow 0:07:06 Measurements with stable flow 0:12:52 Fire 0:27:46 Measurements until fire burnt out 0:06:09 Velocity at pk. 522 during Test 1 P a g e 21 | 31 Average velocity at pk. 522 during test 1 Temperature at pk. 522 during Test 1 P a g e 22 | 31 Pressure drop measured during Test 1 HEAT RELEASE RATE OF TEST 1 The Heat Release Rate (HRR) data has been plotted with the ignition time of the fire pool in Test 1 (occurring at point pk. 255 at 9:27:29) set as the reference point (time zero) on the time axis of the graph. Heat Release Rate curve of Test 1 P a g e 23 | 31 Test 2 Table 12. Time stamps for Test 2. Event Time (hh:mm:ss) Star test 2 11:57:07 Start ventilation 2 jet fan 12:02:29 Fire start 12:12:28 Fire extinguished 12:48:37 End test 2 12:56:06 Table 13. Length of Test 2 sections Test Section Length (min) Measurements without flow 0:05:22 Measurements with stable flow 0:09:59 Fire 0:36:09 Measurement until fire burnt out 0:07:29 Velocity at pk. 522 during Test 2 P a g e 24 | 31 Average velocity at pk. 522 during Test 2 Temperature at pk. 522 during Test 2 P a g e 25 | 31 Pressure drop measured during Test 2 HEAT RELEASE RATE OF TEST 2 The Heat Release Rate (HRR) data has been plotted with the ignition time of the fire pool in Test 2 (occurring at point pk. 255 at 12:12:28) set as the reference point (time zero) on the time axis of the graph. Heat Release Rate curve of Test 2