- #1

bsodmike

- 82

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Hi,

I have been reading some online papers and have been struggling with the following equation as the author seems to introduce it without much detail. Since my background is primarily in electronic engineering, it is quite possible that this could be one of the elementary equations in thermodynamics.

[tex]P_i=\dfrac{q_C}{\lambda_{\text{tot}}\alpha_{\text{st}}}\rho_C\epsilon_{\text{Vi}}\eta_i[/tex]

What I know:

[tex]P_i[/tex]: indicated mean pressure; This is OK!

[tex]\alpha_{\text{st}}[/tex]: the ideal air-to-fuel ratio for gasoline; values vary between 14.3 and 14.8. This is also defined as the "stoichiometric air-fuel ratio"

[tex]\rho_C[/tex]: compressor air density; This is OK! Standard value of 1.2 kg/m^3 is used.

[tex]\eta_i[/tex]: Indicated efficiency, 0.38 is being used; This is OK!

Variables I have no idea about:

[tex]q_C[/tex]: A value of [tex]42.5\times10^6[/tex] is being used; have no idea.

[tex]\lambda_{\text{tot}}[/tex]: relative air ratio, it seems 1.8 is a typical value for constant-pressure (pulse factor = 1) turbochargers??!?

[tex]\epsilon_{\text{Vi}[/tex]:

Cheers

Mike!

I have been reading some online papers and have been struggling with the following equation as the author seems to introduce it without much detail. Since my background is primarily in electronic engineering, it is quite possible that this could be one of the elementary equations in thermodynamics.

[tex]P_i=\dfrac{q_C}{\lambda_{\text{tot}}\alpha_{\text{st}}}\rho_C\epsilon_{\text{Vi}}\eta_i[/tex]

What I know:

[tex]P_i[/tex]: indicated mean pressure; This is OK!

[tex]\alpha_{\text{st}}[/tex]: the ideal air-to-fuel ratio for gasoline; values vary between 14.3 and 14.8. This is also defined as the "stoichiometric air-fuel ratio"

[tex]\rho_C[/tex]: compressor air density; This is OK! Standard value of 1.2 kg/m^3 is used.

[tex]\eta_i[/tex]: Indicated efficiency, 0.38 is being used; This is OK!

Variables I have no idea about:

[tex]q_C[/tex]: A value of [tex]42.5\times10^6[/tex] is being used; have no idea.

[tex]\lambda_{\text{tot}}[/tex]: relative air ratio, it seems 1.8 is a typical value for constant-pressure (pulse factor = 1) turbochargers??!?

[tex]\epsilon_{\text{Vi}[/tex]:

**no clue!**A value of 0.97 has been used. Seems it is a percentage of sorts, an efficiency may be. The subscript "i" is typically used to indicate the word 'indicated' but "Vi" is not making much sense.__Summary:__Have you seen this equation before? Please let me know what [tex]\epsilon_{\text{Vi}[/tex] and I would greatly appreciate if you can confirm the other variables and my guesses/suggestions.Cheers

Mike!

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