As previously mentioned, the theoretical boiler blast pressure was calculated using the TNT equivalent weight of the explosive (water). TNT equivalent weight was found from the internal energy of the water at the specified blast temperature. The sudden rise of the theoretical positive blast pressure (Figure 5.1 - Figure 5.9) for the various filling degrees of the boiler indicates the shock wave. With certain strongly damped pressure oscillations, the peak overpressure eventually recovers to ambient pressure. Following the positive phase of the blast wave, a negative pressure wave develops. On the other hand, the actual explosion scenario depicts a gradual pressure rise to the peak positive overpressure and the negative phase occurs concurrently. As a result, prolonged blast phase and much lower positive peak overpressure are observed in experimental blast waves compared to the theoretical prediction.
For 40% filling degree (Figure 5.1 - Figure 5.3), the theoretical blast duration of the positive phase ranges between 0.27 ms to 0.48 ms. Whereas the experimental blast duration for the stated filling degree ranges from 11.7 sec to 24.7 sec. When filling degree increases to 50% (Figure 5.4 - Figure 5.6), the predicted blast duration of the positive phase ranges between 0.24 ms to 0.47 ms and the experimental blast duration is decreased.
Finally, for 60% filling degree (Figure 5.7 - Figure 5.9), the predicted blast duration of the positive phase ranges between 0.25 ms to 0.46 ms. The ratio between actual blast pressure to expected blast pressure ranges from 20 to 50. So, the theoretical predictions of a boiler explosion do not reflect the actual blast scenario.
Theoretical prediction demonstrates that the positive phase duration of blast wave increases with the increase in standoff distance (Karlos and Solomon, 2013). However,
the duration of boiler blast. Table 5.1 shows the expected explosion pressure is significantly lower than the experimental blast pressure of the boiler. Different explosion temperatures, the non-uniform groove on the front plate of the boiler, and the failure surface are all factors that contribute to this behavior.
Table 5.1: Comparison of theoretical expected explosion pressure and actual explosion pressure of boiler blast.
Sample Designation
Idealized positive incident + dynamic pressure P1 (kPa)
Blast duration of positive phase (theoretical) Δt1 (sec)
Blast duration of positive phase (Experimental) Δt2 (sec)
Expected explosion pressure (Experimental) P2 (kPa)
Actual explosion pressure (Experimental) Pactual (kPa)
B40S8 1300 0.00027 24.7 0.014211 0.6142
B40S10 635 0.00036 11.7 0.019538 0.6015
B40S12 365 0.00048 20 0.00876 0.488
B50S8 1780 0.00024 16.5 0.025891 0.6681
B50S10 800 0.00037 16.9 0.017515 0.6049
B50S12 450 0.00047 18.4 0.011495 0.4907
B60S8 1850 0.00025 13.8 0.033514 0.6641
B60S10 1000 0.00035 19.1 0.018325 0.6314
B60S12 550 0.00046 18.3 0.013825 0.5036
P2=P1∆t×∆t1
2 =(blast pressure× blast duration)theoretical blast durationexperimental
-0.0004 -0.0002 0.0000 0.0002 0.0004 0
500 1000 1500 2000 2500 3000 3500 4000
0.0 1.0×104 2.1×104 3.1×104 4.2×104 5.2×104 6.3×104 7.3×104 8.4×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-6.27 -4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B40S8 Positive Pressure
Negative Pressure
(b)
Figure 5.1: Pressure Time-history of B40S8 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0008 -0.0004 0.0000 0.0004 0
500 1000 1500 2000
0.0 1.0×104 2.1×104 3.1×104 4.2×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
-2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62 16.71
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B40S10 Positive Pressure
Negative Pressure
(b)
Figure 5.2: Pressure Time-history of B40S10 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0010 -0.0005 0.0000 0.0005 0
250 500 750 1000
0.0 5.2×103 1.0×104 1.6×104 2.1×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55 60 65
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B40S12 Positive Pressure
Negative Pressure
(b)
Figure 5.3: Pressure Time-history of B40S12 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0004 -0.0002 0.0000 0.0002 0.0004 0
1000 2000 3000 4000 5000
0.0 2.1×104 4.2×104 6.3×104 8.4×104 1.0×105
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B50S8 Positive Pressure
Negative Pressure
(b)
Figure 5.4: Pressure Time-history of B50S8 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0008 -0.0004 0.0000 0.0004 0
500 1000 1500 2000 2500
0.0 1.0×104 2.1×104 3.1×104 4.2×104 5.2×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55 60 65
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B50S10 Positive Pressure
Negative Pressure
(b)
Figure 5.5: Pressure Time-history of B50S10 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0010 -0.0005 0.0000 0.0005 0
500 1000 1500
0.0 1.0×104 2.1×104 3.1×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55 60 65
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B50S12 Positive Pressure
Negative Pressure
(b)
Figure 5.6: Pressure Time-history of B50S12 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0004 -0.0002 0.0000 0.0002 0.0004 0
1000 2000 3000 4000 5000
0.0 2.1×104 4.2×104 6.3×104 8.4×104 1.0×105
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55 60 65
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
-2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62 16.71
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B60S8 Positive Pressure
Negative Pressure
(b)
Figure 5.7: Pressure Time-history of B60S8 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0008 -0.0004 0.0000 0.0004 0
1000 2000 3000 4000
0.0 2.1×104 4.2×104 6.3×104 8.4×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
-6.27 -4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53 14.62
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B60S10 Positive Pressure
Negative Pressure
(b)
Figure 5.8: Pressure Time-history of B60S10 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.
-0.0010 -0.0005 0.0000 0.0005 0
500 1000 1500
0.0 1.0×104 2.1×104 3.1×104
Pressure (psf)
Pressure (kPa)
Time (Seconds)
Checked based on reflected impulse [ir]
Idealized positive incident + dynamic pressure [Ps + CDq]
Idealised Total reflected pressure [Pr]
(a)
0 5 10 15 20 25 30 35 40 45 50
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6
-4.18 -2.09 0.00 2.09 4.18 6.27 8.35 10.44 12.53
Explosion Pressure (psf)
Explosion Pressure (kPa)
Time (Seconds)
Pressure time-history of B60S12 Positive Pressure
Negative Pressure
(b)
Figure 5.9: Pressure Time-history of B60S12 (a) Theoretical positive pressure along with reflected impulse and (b) Experimental positive and negative pressure.