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I keep forgetting to talk about the compressor wheels.. Posted by John Williams [Email]  (#1982) [Profile/Gallery]
(more from John Williams) on Wed, 7 Dec 2005 21:37:05
In Reply to: Re: It's all about pressure ratios, Vigge, Wed, 7 Dec 2005 11:33:12 Members do not see ads below this line. - Help Keep This Site Online - Signup |
These compessor wheels compress air, they push the air with blades, just like an airplane propellor... Its a known fact airplanes loose thrust at higher elevation. A turbo fan or ducted fan that has enough thrust to fly at sea-level, can not even get off the ground in Denver, not enough thrust.
The turbine comprssor wheels are also effected by the thinner air and do not push as much of it to the same pressures as they do at sea-level.
Every enine guy I talk to mentions the oxygen content and how I have less of it... I have less per volume... If I can burn 1 gallon of fuel per hour at sea-level, I will burn about .8 gallon a mile high... About a 20% loss in effeciency. The turbo trys to get back some of this loss and reach a higher manifold pressure, but falls short in its ability to make the same amount of pressure at the manifold that it can at sea-level... It definetly helps to get some of the power back, how much is the question...
So, not only do I have a combustion engine that is loosing power because it is running with a pressure drop, less oxygen per volume, it has a compresor that is pumping less air than it will at sea-level... All the factors combined could give me the amounts corrected in sae... I just wish I could prove it...
P.S. everything that works on paper does not work in real life... I have seen this over and over and although its not the norm, it does happen... We designed an airfoil for my racing plane that was supposed to be great on paper, all the math worked, the airfoil was more efficient in the turns and good in the straights, it did very well in the computer simulation program... Real life, did not go that fast.... There was another airfoil the naca 012-66 that is not supposed to be that great for our size and weight of aircraft and the reynolds numbers... For some reason it works very well in real life, its been the dominate airplane for the last 5 years.... Maybe we are missing something in all of our theory, principles, math and programing that we are not accounting for in the loss calculation....
John
posted by 64.48.194...
, Thu, 1 Dec 2005 10:47:40, Tue, 6 Dec 2005 20:13:50, Wed, 7 Dec 2005 06:04:12, Wed, 7 Dec 2005 21:37:05 <-- Viewing This Message, Fri, 9 Dec 2005 14:00:12, Wed, 7 Dec 2005 21:12:55, Fri, 9 Dec 2005 13:44:33, Sat, 10 Dec 2005 10:06:48, Sat, 10 Dec 2005 16:32:03, Sun, 11 Dec 2005 04:05:03, Sun, 11 Dec 2005 09:31:34, Sun, 11 Dec 2005 14:41:26, Mon, 12 Dec 2005 13:21:10, Fri, 2 Dec 2005 08:11:38, Thu, 1 Dec 2005 15:50:21, Thu, 1 Dec 2005 16:58:28
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