GA/Experimental Turbines

[CRAN]

I thought folks might be interested to see these new experimental turboshaft engines being developed, light, efficient and with a rather long TBO.

http://www.innodyn.com/aviation/products.html

If you consider an Innodyn 185TE powered R22 for example, 40kg (88lb) of extra payload, runs on jetfuel and it's a turbine! Fuel efficiency is roughly equal to a Lycoming ~ so i'm told.

CRAN
:cool:

[Dave_Jackson]

Innodyn states that their turbine is a fixed shaft engine.
The following quote might be of value.


"There are really only two varieties, free- and fixed-shaft turbines.

In a fixed-shaft engine, the power turbine, compressor and transmission are linked solidly by a shaft (except for the freewheeling unit, of course). It works okay...most of the time. However, if a heavy load on the main rotor (like a sudden application of pitch) drags down the N2 (power turbine) rpm, it also therefore drags down the compressor rpm. Not good. The governor will call for more fuel, and that's the only way to get the rpm to come back up. Once you reach the max fuel-flow limit, look out!

In a free-turbine engine, the output from PT (power turbine) is connected to the transmission but NOT the compressor. However, there is another turbine stage *behind* (airflow-wise) the power turbine. It is THIS turbine section that is connected by shaft, forward to the compressor. What this means is, if the MR rpm gets bogged-down by that aforementioned large application of collective pitch, the compressor rpm can actually increase speed to get the N2 rpm to come back up.

There aren't too many fixed-shaft turbines around anymore. Free turbines work better in helicopters, where the output shaft rpm must be held constant to a fairly tight tolerance over a wide range of power demands."

[Freewheel]

Dave,

Your point is, of course, well made however I contend that the advantages sought from a turbine against a piston are primarily, and in varying order;


* Power to Weight Ratio
* Installed weight and size
* Altitude Performance
* Soothing the pilot's ego, if he/she's a turbine snob


The circumstances mentioned apply also to Piston engines, and can, though unlikely, apply to free turbine engines also.

What you're referring to is mismanagement of controls, not necessarily a factor that should dissuade somebody from contemplating the engine, aside from ensuring that it's powerful enough to support a small, light, reliable SAS, or a rotor system that is easy to fly, eh CRAN?

[The Nr Fairy]

If you take 88lb (40kg) from behind the mast, where the current Lycoming is, what effect will that have on the CG ? A "SWAG" seems to put it well forward of the limit.

Anyone ?

[boomerangben]

If you are taking the R22 as an example, I'm sure that Frank would choose a large power margin for an engine and providing the FCU on one of this turbines is clever enough, I would have thought a single spool turbine would be adequate.

To solve the CoG problem, how about making the R22 a twin turbine? :E :E

[CRAN]

Nr is correct it would put the CG fowards but it is not difficult to engineer the CG backward in a helicopter!

On the subject of one or multi-spool engines, it's not my field so i'm not going to be drawn into a hand-waving discussion, other than to say that the situation with a single spool engine is no worse than that of a piston engine in a helicopter. If the engine is adequately sized and govened then there will be no difficulty in applying it to light helicopters. In bigger machines then of course you would wish to use multispool engines, due to the removal of the need for a clutch and the efficiency benefits. However in small machines in which cost is the driver then there ARE three relevant benefits to operating a single shaft engine in a helicopter excluding cost and simplicity, firstly an increased surge margin (compared to a similar spec two-spool engine), secondly generally there is an improvement in of-design efficiency and finally there is a reduced lag in torque response - all the bits are allready spinning at the correct speed, you just need to propogate the temperature change through the engine.

From a pilots point of view it would be interesting to hear from Flying Lawyer and md600 driver about how they find the engine response in their Gazelle's, since the Astazou is a single spool unit.

CRAN