Intake restricor getting cooled during engine running

[tarun garg]

Hi
Whenever our engine runs at a high rpm for a prolonged time, the intake restrictor, which is made of aluminium get cooled, just like a refrigerator. This is surprising and am not clear what causes this immense cooling. Could it be that the restrictor is too small and that is causing sudden expansion of the air fuel mixture.

Thanks for your help....

[TorqueWrench]

That is normal as far as I have found. The cooling, as far as I know (and I know someone will correct me if I am wrong), this all comes down to PV=znRT.

I have been doing some steady state comparisons of restrictor designs and have noticed a theoretical 50 degree drop in fluid temperature at the end of the throat and beginning of the expansion.

In other words, your restrictor is most likely fine.

[jrickert]

This is normal. I have seen subzero temps with some restrictor designs in CFD

[MalcolmG]

Sounds like a good argument for making your restrictor out of a material with a negative coefficient of thermal expansion - ie carbon fibre http://fsae.com/groupee_common/emoticons/icon_wink.gif

[jordan.k]

Originally posted by MalcolmG:
Sounds like a good argument for making your restrictor out of a material with a negative coefficient of thermal expansion - ie carbon fibre http://fsae.com/groupee_common/emoticons/icon_wink.gif

The only problem is creating a composite part out of carbon fiber with a resin with a positive coeffecient of thermal expansion.

[Wesley]

Sound's like you're running a carburetor upstream of the restrictor - super low pressure in the restrictor is vaporizing the fuel, heat of vaporization is cooling the throat down even more significantly.

[billywight]

The low temps seen are due to the very low pressures at the throat of the restrictor. The CFD plot below is a contour of fluid temperature (blue represents 245 K, red is 295 k).

http://img233.imageshack.us/img233/766/tempd.jpg