Final Checks...the engine is ready to go!

[thecheat]

Could I suggest a Y junction, with a increased dia on the bottom? Then you could rig up two blowers, should only cost you a few bucks to try! As, I seriously doubt you'll get enough air moving through there with one leaf blower!

Maybe something like this would work?
http://littlewonder.com/sho-blower.asp

[Arman_awn]

Thanks my friend, you're right. this MONSTER needs two blowers instead of one to work. I'll be after that, and I'll inform you about any step forward in my work.

Thanks,

Arman.

[Irvine.J]

Have you tried this motor and it didnt work? Perhaps show us the video anyway? You could try making a long slender cone to make a smaller nozzle, make it long like an extra 1.5 feet or so, should give you more speed/better performance?

[larry cottrill]

You could try making a long slender cone to make a smaller nozzle, make it long like an extra 1.5 feet or so, should give you more speed/better performance?

Number47 & Arman -

What you've suggested here (long blower nozzle) is all right in principle, BUT REMEMBER: You MUST cover the entire engine inlet with high-speed air! It won't do any good to get extremely fast air in a narrow blast down the center - that DOESN'T make proper use of your diffuser! The ideal (probably unattainable for us amateurs) is to have the EXACT SAME VELOCITY all the way across the diffuser inlet. The closer you can get to that, the better. Also, the air going in must have virtually NO TURBULENCE, or you will get separation from the diffuser wall and lessen its performance.

L Cottrill

[Arman_awn]

I have an idea i want to share it with you:

What if we deliver the exhaust gases of a turbojet (turbocharge based turbojet) to the diffuser of the ramjet?

is it possible to use the exhaust gases of the ramjet to spin the turbo turbine and then deliver the compressed air(coming from the turbo's comp) to the diffuser?

I have to remind you that those two ideas are completely different...

[larry cottrill]

What if we deliver the exhaust gases of a turbojet (turbocharge based turbojet) to the diffuser of the ramjet?

That has been done - it's called an afterburner. Its only main difference from a pure "ramjet" is that you are driving it with fairy high temperature air.

is it possible to use the exhaust gases of the ramjet to spin the turbo turbine and then deliver the compressed air(coming from the turbo's comp) to the diffuser?

That is using the ramjet as a turbojet combustor. Its only main difference from a pure "ramjet" is that you are driving it with fairly high pressure air. Of course, a more conventional turbo combustor design would be more efficient under that set of conditions.

There is nothing "wrong" with either idea. However, in both cases, you are no longer using the ramjet as a ramjet. At least by using a big cold air blower, you are simulating a ramjet's operation in normal air (though not at a high altitude, of course).

L Cottrill

[Arman_awn]

FIRST IDEA:
___________________________________
Dear Larry, delivering the exhaust gases of a turbocharger based turbojet engine to the "diffuser" of a ramejt is not surely called an "afterburner". I know you have come up with the same misunderstanding most of the people do when I talk about this idea.

You should notice that in an afterburner the EGs(exhaust gases) are not compressed, but you know there is an element called "diffuser" in front of a ramjet, so if there's a ramjet right behind where the EGs of a turbojet expand, firstly, those gases will be "well" compressed due to their high speed (sometimes beyond the speed of sound) and then, they are delivered to the cc and are ignited.

When the AB is lit, the engine is alwayse "thirsty", because no or poor compression has been done before re-combustion of the gases. But if the EGs are compressed once more, the fuel consumption rate falls rapidly and there will be MUCH MORE boost from this type of "After Ramjet(!)" than a conventional type of AB.

_____________________________________
SECOND IDEA:
You've mentioned that using the conventional type of turbo combustor desing is more efficient than that desing I've proposed. But listen to me:
Under the static conditions (zero speed) you seem to be right, but let me clerify that I want to build a "self-sustaining" ramjet...So the fuel efficiency of the engine is not considered that important at the expense of the ability to start and sustain at static conditions. Apparantly, this type of combustor which is a ramjet engine in fact, is open at both ends. only a portion of the exhaust gases are guided through the turbine in order to provide the power to turn the compressor for the next cycle. As the speed increses, the pressurized air being fed from the turbo's compressor provides only part of the entire engine's compression, the remainder part of the compression comes from the job the diffuser has done, it has compressed the intake air by the forward movement of the engine, as a result of the appearance of Ram effect.
Perhaps this type of engine requires two flame holders or liners inside each other (they are seprate from the combustion chamber). One to slow down the incoming air from the diffuser, and one to hold the compressed air coming from the turbo's compressor...

Forgive me for my long long text book! I'll be really glad to hear your opinions about the things I've pointed to.

Thanks,

Arman.

[Johansson]

First answer:

If you restrict the exhaust of a turbojet the EGT will rise since the pressure drop over the turbine decreases. The thrust will rise because less energy is converted to shaft power by the turbine, so the engine needs more fuel to keep the revs constant. That extra fuel will overheat the turbine if the back-pressure gets too high.

The answer to the first question is that the engine will probably melt before you can get any useful pressure from the turbojet.

Second answer:

A ramjet with its trail of fire will not be a very good combustor, the engine will probably melt before it gets self-sustaining.

//Anders

[Johansson]

Any progress with the ramjet?

//Anders