for Typical Vehicle Types Vehicle Type Peak Fire Heat-Release Rates [MW (MBTU/hr)] Passenger Car 5 - 10 (17 - 34) Multiple Passenger Cars (2 ~ 4 vehicles) 10 - 20 (34 - 68) Bus 20 - 30 (68 - 102) Heavy Goods Truck 70 - 200 (239 - 682) Tanker 200 - 300 (682 - 1,024) Source: NFPA 502, 2011 - Table A.11.5.1 Table 3.
Ingason (2006) has evaluated design FHRR, but the author finds these FHRR very unlikely.
The train FHRR assessment presented in this paper has taken into consideration the new technology train: R-142.
In Scenario 3, 3.785 liters of gasoline was able to reach a maximum ignition FHRR of 1.5 MW within 20 seconds and extinguished by 42 seconds.
The red curve represents the total FHRR including accelerant and combustible of the trains.
Because the gasoline is much more, it is able to sustain a FHRR of 2 MW for about 30 seconds and then and explosion occurs at about time 75 seconds.
Also, it should be noted that the sharp peaks, while the igniter is burning, are not considered as design FHRR, but rather the FHRR after the igniter is consumed, and a more stable(self sustained) FHRR is established.
The station train fire, using 5 liters of accelerant placed strategically in a corner of a car (scenario 5), will grow and the train FHRR will fluctuate between 1.5 and 3.2 MW.
Under the original design FHRR (14MW), a double-track tunnel section would require 121kcfm past the train to control the smoke and the tunnel ventilation fan plant would need to draw 400kcfm (Figure 2).
If the tunnel FHRR to be considered is unjustifiably very large, it could lead to an over design.
This paper has demonstrated the importance of establishing the appropriate FHRR has on the design and constructability of a rail and road tunnel project.
From a ventilation point of view, it was shown that there is no direct numerical correlation between the FHRR and required ventilation airflows, but we must rely on computer simulations to establish credible FHRR scenarios and assess the tunnel configurations throughout the system.