Post-Compressor Intercooling?

Moderator: Mike Everman

Post Reply
Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL

Post-Compressor Intercooling?

Post by Ash Powers » Mon Sep 06, 2004 5:18 pm

I have been pondering the idea of intercooling the compressor's charged air since the idea came to me of building a jet engine from a turbocharger (and then found all you wonderful freaks just like me, LOL) as I come from the automotive performance industry (specialize in the 300ZX twinturbo - go figure) and we use intercooling to improve the efficiency of the turbochargers and ultimately produce more power. I have a pair of stock 300ZX intercoolers that I sat aside for this project, but I could have sworn that I read somewhere that intercooling the charge would be counterproductive to this application. Despite this, I managed to get my hands on the "JetSpecs" application for calculating flametube design and turbine performance. One of the points of great interest is the compressor efficiency parameter. Let me briefly give some info to backup my opinion here:

In a dynomometer shootout involving the comparison of various aftermarket intercoolers (as well as a pair of units I engineered for the 300ZX), we took power output values as well as inlet and outlet temperature readings on the intercoolers. Here is a dynochart as well as thermal information I collected:

You can see that the average intercooler inlet temperature was around 250 degrees(F) - this is the same as the compressor outlet temperature since the compressor outlet feeds the intercooler inlet. The interesting point of data is that the average intercooler outlet temperature is around 130 degrees(F). Obviously this condenses the air which ultimately makes more power (since more O2 is available per volume of intake air).

Now, back to the JetSpecs program:

If you look down on the left after entering your values, you will see a calculated value for compressor temperature rise and compressor discharge temperature. Obviously this is in Celcius and not Fahrenheit, but 130F is 54C.

Now if I use the *actual* efficiency of my turbochargers (74%) for the compressor efficiency value, I get 152C as the discharge temperature and 31.27lbs of thrust.

However, in my research, we can achieve considerably lower charge temperatures by use of intercooling - temperatures as low as 54C! Now if I *tamper* with the compressor efficiency value and get the compressor discharge temperature down to 54C, the thrust increases to 54lbs with an incredible efficiency value of 375% due solely to intercooling.

I guess once I get all things sorted out and the engine performing up to max spec with kerosene and AB performing to spec, I think I'll make a few modifications to the setup and incorporate the intercoolers and some electric fans and then start taking some thrust measurements. If anyone has any input on the matter, or know of any other research pertaining to this, I would be highly appreciative of what you have to offer!

Post Reply