Small Turbojet Engines (Discussion) 1

[Wittenborn]

Greetings.

I am in need of small, tubojet/fan engines for a preliminary aircraft design. I have noticed that there is a large void in the thrust output category, between 50 lbs thrust (model airplane turbines) and about 700 lbs thrust (Williams FJ22... as yet to be proven).

As of now, I have not found any jet engines within the 300 - 500 lb thrust range. Does anyone have any thoughts as to why we haven't brought jet engine technology down to even smaller levels?

Home experimenters have built turbine engines from such things as automotive turbo-chargers, and even the radio controlled industry has produced small turbine engines with 10 - 20 lbs of thrust...

Just a topic for discussion....



Regards,
Grant Wittenborn
Aerospace Engineer

http://www.darcorp.com

 

[Miper]

On-purpose engines of the type you mention are being seriously considered and preliminary designs are complete. Their efficiency rivals the latest piston/propeller engines, and their weights are considerably less. Several designs were presented in a forum at the recent EAA convention in Oshkosh by Jerry Merrill of Advanced Propulsion, Inc. Airplanes using these engines look very good, the only drawback being somewhat longer takeoff distances because of the inherent differences between propellers and ducted fans.

NASA also has a very small program to study piston engine/ducted propeller combinations in terms of aircraft cost and design integration advantages, and several serious efforts are currently underway in this area.

 

[FredGarvin]

Two factors that have as of today, stood in the way of development that I see (IMO):

1. Market need. An engine development program is a VERY expensive endeavor on any scale. There must be a need.

2. The problems that arise when dealing with small engines arise quite quickly. Going smaller is not an easy thing to do. One caveat to that is that one would want to reduce the overall engine size with the thrust output to keep it competetive in a commercial or military scenario. One could derate an existing engine to a lower thrust output, but you'd have a much worse thrust to weight ratio and SFC because of it.

Depending on what you need, you may find something if you look into target drone engines used by the military.

 

[Miper]

1. There is a market need today for an engine that burns widely available jet fuel instead of aviation gasoline, which is already unavailable in large parts of the world and is very costly.

2. Very small engines are, indeed, difficult to design; and derating an existing engine leads to terrible inefficiencies due to the off-design operations. Nevertheless, if an on-purpose small turbofan is properly designed for the flight regime of today's faster piston engines, the efficiencies can be excellent.

Cruise missile and target drone engines are typically made for a very short life.

 

[tbuelna]

Mr. Wittenborn:

You can try these two:

http://www.agilis.com/engines.html

http://www.m-dot.com/page7.html

I don't know if either company has anything like a real "production" engine.

Good Luck.
Terry

 

[Wittenborn]

Thanks Terry,

Both are good leads. Agilis sounds the most promising of the two, as they contend that they will be ready to deliver small, 1,000 lb thrust engines but Q4 2004. 1,000 pounds of thrust currently seems to be the lower limit of thrust for production engines.



Regards,
Grant Wittenborn
Aerospace Engineer

http://www.darcorp.com

 

[jdsewell]

Pratt & Whitney Canada PW600F Turbofan: 1000 - 3000 lbs. thrust. Eclipse aviation advertises the Eclipse 500 will operate with a PW610F medium bypass turbofan with a 900 lbs. thrust developed from the 600 family. PWC doesn't show any info on their website (not much on the PW600 family really). Eclipse has a cutaway nice jpeg though.