ICE chamber temp after supercharger?

[mos68x]

Hello, I'm new to the forum so please forgive me if I am killing a dead horse.

I'm working a project that seems to keep changing every 5 min. I have a 1.8 motor that I have previously done bottom-end work and head work to exceed $3500 and I need help in finding that elusive formulea to find the perfect setup for a "new" fuel for the engine, hydrogen. Among many other things to change in my projected setup, one is the boosting method and the other is static compression ratio.

I have run across a NACA survey file that goes into great detail on the flame temps, propogation, and limits of hydrogen being used in an ICE.

http://naca.larc.nasa.gov/reports/1958/naca-report-1383/

What I want to do is use 12:1 static compression to take full advantage of hydrogen's high octane effect and supercharge it as well, so say only 8 psi to start with for equation's sake.
The problem that I am having is that I cannot find one single formula that averyone seems to agree on for calutating tempurature increase for given pressure increase. I have to keep the intake charge less than 515C so that I do not have auto-ignition before spark ignition, besides trying to avoid detonation from cyl temps.

I have been using a formula similar to the following to get an idea where to start from at least:
dT = T1 * [((P2/P1)^.285)-1]
I cannot find the exact post I found this on since I'm a little tired, but I did put it into my Excel beforehand.

I have used it to find a generalization of temp after supercharging, but I am not sure if I can use the same formula to calc the temp increase from the static CR.

I have used the ECR formula to find cyl PSI numbers so that I can start with some sort of numbers.
((boost psi / 14.7) + 1) x static compression = effective compression
SCR: 12:1
boost PSI: 8
ECR: 18.53:1
chamber PSI: 420.6

pressure ratio: (8+14.7)/14.7)
temp ratio: ((8+14.7)/14.7)^(0.4/1.4)=1.132
tempR: 1.132*529.6R(70F)=599.6R(140F)

And to continue to the chamber after the supercharger temp I get 1095F(590.6C) with the same formula and without any cooling at all.

Can someone confirm/deny this work for me? I'm tired so please forgive any incoherent thought.

 

[JimCasey]

Marks' Handbook page 4-9

Reversible adiabatic isentropic, which is pretty nearly what you have:

T2/T1=(P2/P1)^(k-1/k)
T2/T1=(22.7/14/7)^(.4/1.4)
T2/T1=1.13
For initial temp of 100F, the pressure would escalate to 174F. This disregards heat added due to inefficiency in the turbo compressor, heat transfer from the turbine to the impeller to the gas, etc. I have seen reports in gearhead literature where turbochargers are claimed to have an outlet temp areound 300F.

Use an intercooler. H2 may have a high octane but it also has a really low ignition energy.

 

[mos68x]

Thanks for the help Jim, but there is a problem with the formula as you have already mentioned, the lack of the efficeincy rating for the supercharger. i'll be using a whipple supercharger and has an eff as high as 80%, how do you properly feed this into the eqation?
i was tired when i typed the first one, i guess i forgot to mention that peoblem too.

 

[pmover]

i will highly recommend obtaining the book "Internal Combustion Engine Fundamentals" written by J.B. Heywood. ISBN 0-07-028637-X.
a well-written & informative book with sufficient technical information to keep you busy for a long time. in fact, too much information for me to type in the posting. see chapters 9 (heat transfer) and the chapter for spark ignited engines (most likely case you are working on) or compression ignited engines.

good luck!
-pmover

 

[mos68x]

yes hydrogen can have a low(er) ignition energy requirement, however it depends on the pressure that it is at when required to ignite.
the auto-ignition point at ambient pressure is about 515C rising from there (see NACA Report:

http://naca.larc.nasa.gov/reports/1958/naca-report-1383/

)

my goal is to get as much compression as i can, and still be within the limits of the starter and about 500C after full compression.

 

[mos68x]

i think i might actually keep the CR where is it right now (9:1) so that i can get more boost and still keep it cool. but that depends on how much boost the SC can produce for the 1.9L i have