Composition of AVTUR 2

[stanier]

In order to predict he bulk modulus of Avtur I need to get a handle on the % compostion of the fuel. Would anyonebe able to provide a typical range of % composition of paraffins, aromatics and napthalenes for this fuel?

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[PTH001]

I do have composition and propertied of Avtur (both F34 and F35) but you can get them from the internet. Try a search for Def Stan 91-87 for F34 (with FSII), Def Dtan 91-91 for F35, There is also some general useful info in Def Stan 01-5.

I have an authoratative bulk modulus for F34 as follows:

"Bulk modulus is potentially sensitive to temperature, unless you want the
isothermal bulk modulus. The isothermal BM is used when a relatively slow
compression process takes place. The adiabatic BM applies to conditions of
sudden change in pressure. This is used when calculating reaction speeds of
servomechanisms and the forces acting on pump components. The two are
related by the equation
BS/BT = y
where BS is the adiabatic BM and BT is the isothermal BM.
y is approximately equal to 1.15 for jet fuels.
The adiabatic BM for Jet A-1 at 25'C in MPa is approx.
1260 when the system pressure is 7Mpa
1340 when the system pressure is 14Mpa
1420 when the system pressure is 21Mpa
1510 when the system pressure is 28Mpa"

 

[BigInch]

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[stanier]

Thanks very much for the information.
PTH001 where do I find reference to "y" for other liquids? I noted in Chempak (

http://www.aft.com)

that BM changed with pressure. It is a matter I need to take up with the surge analysis software developers. They have probably ignored it as the change is not that drammatic and there are plnety of other approximations in that technology.

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[BigInch]

k Ratio of specific heats.

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[BigInch]

more specifically,
*********************************************
Isentropic bulk modulus = 1/compressibility
************************************************************
Boelhouwer, 1967; Rolling and Vogt, 1960
Beta = c^2 * rho
where:
Beta = isentropic (no heat transfer = constant entropy) bulk modulus in Pascal
c = speed of sound m/s
rho = density kg/m3
****************************************
isothermal bulk modulus, Kt
***********************************************
Kt = -V(partial P/partial V) at constant temp
Kt = Youngs_Modulus/3/(1-2 * Poisson_Ratio)
Kt = Ks/(1 + alpha * heat_capacity_ratio * Temp)
Kt = Cv/Cp * Ks
Kt = 1/(1/Ks + T * alpha^2/Cp)

Cp = heat capacity at constant pressure
Cv = heat capacity at constant volume
alpha = thermal expansion coefficient

Cp - Cv = V * alpha^2 * Temp * Kt

*******************************************
adiabatic bulk modulus, kappa or Ks at constant entropy
*******************************************
kappa Ks = -V dP/dV at constant entropy = gamma * p
kappa Ks = rho (partial P/respect to rho) at constant entropy
with adiabatic exchange of heat
rho = density

Ks = Kt (1 + alpha * gamma * T)
where alpha = coefficient of volumetric thermal expansion
gamma = Gruneisen parameter
T = temp

Ks = Cp/Cv * Kt
where
Kt = isothermal bulk modulus
Cp = heat capacity at constant pressure
Cv = heat capacity at constant volume

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