21.11.2014 Views

Untitled - Aerobib - Universidad Politécnica de Madrid

Untitled - Aerobib - Universidad Politécnica de Madrid

Untitled - Aerobib - Universidad Politécnica de Madrid

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

186 CHAPTER 6. LAMINAR FLAMES<br />

In or<strong>de</strong>r to perform the numerical calculation of the flame velocity the following<br />

values given by Hirschfel<strong>de</strong>r were applied. These same values were also used by<br />

Gilbert and Altman in his work:<br />

ρ 0 = 9.17 × 10 −4 gr/cm 3 ,<br />

T 0 = 423 K,<br />

T f = 1933 K,<br />

λ = 0.00067<br />

cal<br />

cm s K ,<br />

c p = 0.6623 cal<br />

gr K ,<br />

L = 1.33.<br />

(6.222)<br />

With them, the reduced activation temperature results to be<br />

θ a =<br />

The numerical integration of Eq. (6.218) gives<br />

When the prece<strong>de</strong>nt values are taken into (6.221)<br />

which, when taken into (6.212), finally results<br />

37 000<br />

= 9 632. (6.223)<br />

1.933 × 1.9872<br />

I K<br />

1 − θ 0<br />

= 270.9 × 10 −5 . (6.224)<br />

Λ −1/2 = 8.2962 × 10 −2 , (6.225)<br />

u 0 = Λ−1/2<br />

3.97<br />

≃ 209 cm/s. (6.226)<br />

The agreement between this value and the 200 cm/s given by experimental results is<br />

better than it could be expected consi<strong>de</strong>ring the dubiousness of many of the numerical<br />

values used.<br />

Influence of pressure<br />

As shown in Eq. (6.212) the flame velocity varies with pressure in accordance with<br />

the following law<br />

u 0 ∼ p1/2<br />

ρ 0<br />

∼ p −1/2 , (6.227)<br />

in agreement with the predictions of theory for first-or<strong>de</strong>r reaction flames Eq. (6.75)<br />

and as verified by the experiments carried-out by Adams and Stocks [36].

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!