Smoke Toxicity, Linings and Enclosure Fires

Paper, Order, or Assignment Requirements

 
-the order consist of a given table of average concentrations of gases released and the O2 content during the first 9 minutes of the fire were measured in an experimental simulation
– a set of questions and calculations are asked to be answered
– CFAST, CFD and FDS fire models are needed to be used
– a spread sheet is needed to be developed
– please follow the instructions in the given question paper in terms of word limit for each question
– some hints are given which might be useful

VQB5612 –  Scientific Principles for Fire Professionals

Assignment 3 – Smoke toxicity, linings and enclosure fires

 

Scenario 1. A 25 kg cube of expanded polyurethane foam (200kg/m3) sitting on the floor catches fire on the top surface (ignited by an errant welder) and burns to completion with flaming combustion in a warehouse. The warehouse dimensions are 70m x 30m x 10m.

 

Average concentrations of gases released and the O2 content during the first 9 minutes of the fire were measured in an experimental simulation and are given below in Table 1.

 

Table 1.

Time

(min)

1 2 3 4 5 6 7 8 9
CO (ppm) 0 0.62 1.86 3.72 9.92 14.88 24.80 37.20 62.00
HCN

(ppm)

0 0.007 0.022 0.045 0.119 0.179 0.298 0.446 0.744
CO2

(%)

0 0.0013 0.0039 0.0078 0.0208 0.0311 0.0519 0.0778 0.1297
O2

(%)

21 21.00 20.99 20.98 20.96 20.94 20.90 20.84 20.74

 

TASKS:

 

  1. Calculate and graph the Heat Release Rate (HRR) over time based on the data of gases measured above and an assumed Effective Heat of Combustion. This is Curve 1. (Hints: Assume that all the CO produced from the fire remains in the building. As discussed in the lecture the link between HRR, mass loss and toxic species production.). What is the total MJ released during the 9 minutes?
  2. Situation 2. If the material was located on a wall as a lining 25mm thick and ignited at the bottom.Qualitatively estimate the HRR and draw in an approximate HRR curve. This is Curve 2. Compare the curve 1 and 2, discuss. (Word limit 150)

 

  1. Situation 3. Recalculate the HRR Curve 1 if the material was timber instead of polyurethane and theCO levels in Table 1 occur. (hint: would the mass of timber burnt be the same) This is Curve 3. Compare the curve 1 and 3 and discuss. What products are now likely to occur that were not generated by the polyurethane? How would the visibility change? (Word limit 150)

 

  1. Situation 4. Assume the combustion of the block of is in limited oxygen supply conditions, how does this change the burning and toxic products and the numbers in the Table, discuss.(Word limit 150)

 

  1. If the polyurethane is used as wall lining with a metal face in a Class 7 building, which test is required to be undertaken according to the NCC BCA Vol 1 (Clause C1.10)? Briefly describe the method (150 words max) and discuss any limitations of the test method (Word limit 150)

 

  1. You are asked by a client to use the zone model CFAST to predict the values of the test in Table 1 for Scenario 1. Can you do it? Briefly discuss the inputs required and limitations of the model. The client asks if CFAST is a two layer zone model. What is your response(Word limit 200)

 

  1. You are then asked by a client to use the zone model CFAST to predict the gas species CO, CO2, and O2 for Scenario 2. Can you do it? Discuss the inputs required and limitations of the model.(Word limit 150)

 

  1. You are asked by a client to use the CFD model FDS to predict the values in Table 1 for Scenario 2. Can you do it? Discuss the inputs required and limitations of the model.(Word limit 150)

 

METHODOLOGY:

 

 

  1. It is compulsory that the students generate spread sheets using the information in the table.

 

  1. Discuss the approach you’ve adopted, explain your assumptions and reference input data values. Show calculations which were not based on the spread sheets. Discuss your results.

 

  1. If you use spread sheets capture screen images of your spread sheets with all the input and output values and units clearly identified and attach them to your returned assignment submission in addition to the spread sheet itself.

 

Hints:

 

  • The hint that the all the CO remains in the building is the guide.

  • As discussed in the class there is a link between mass loss of the fuel and toxic species produced.

  • Step 1. Given the levels of CO in the building can you figure out the mass loss of the fuel at each time step?

  • Step 2. If you know the mass loss of the fuel can you figure out the HRR at each time step?

  • You can also use oxygen consumption based on the same principle but the equations for the cone and room calorimeters assume a flow rate through a duct. The assignment question is not flow rate scenario.”