How about a Gas Turbine engine that uses Posititive Displacement pumps instead of centrifugal or axial fans normaly used. The kind I am thinking of is maybe a vane pump, or gear pump, but other positive displacement pumps might work. They could be used for both compressor and turbine, as most of them would work as either. Either the turbine would be bigger, or some gearing would make the turbine spin faster then the compressor to ensure gasses flow in the right direction.

This might make Gas Turbines more suitable for automotive use, as it would operate at lower rpm speeds, and would not suffer the lag associated with gas turbines in cars.

A seperate Power Turbine could be added, although might not be needed, as the compressors turbine and power turbine would always be spinning at the same speeds.

This design would also mean a regenerator, or heat exchanged could be added as with other Gas Turbines, making it more efficient.
-- Bal, Oct 18 2004

A Gear Pump http://www.pumpscho...ciples/external.htm
One sort of pump/fan that could be used [Bal, Oct 18 2004]

Chryslers 1950's Turbine Car http://www.aardvark...pjet/chrysler.shtml
A few companys experimented wit Turbine cars but they never took off [Bal, Oct 21 2004]

Is this similar to what you mean? http://www.halfbake...s_20Rotary_20Engine
See the links and comments contained within. [Ling, Oct 24 2004]

Starrotor http://www.starrotor.com
Very similar idea. Would appear to be in the oven, baking already! (Im just not quick enough) [Bal, Oct 26 2004]

I'll give it a vote if for no other reason that I was pondering the same idea last week. Maybe two roots blowers back-to-back, one geared higher than the other to accomodate the increased volume of the exhaust gases, with a combustion chamber in between.
-- riccoman, Oct 18 2004


Sounds pretty similar to the method of vaning used in old steamers, where the vane angles were changed as the steam entered a new chamber along the prop axis.

Bun, if only because I'm sure we can do better than the current methods of creating drivetrain power.
-- shapu, Oct 18 2004


Similar to a rotary engine, then.
-- unclepete, Oct 21 2004


No at all. It would still in principal be a gas turbine engine. This would mean a seperate combustion chamber that would be continuously fed with intake air, and be continuously burning, so more fuel can be burnt in a time period.
-- Bal, Oct 21 2004


Welcome to the bakery, Bal... and congratulations on your first idea not being eaten alive.
-- david_scothern, Oct 21 2004


Burning more fuel would be wasteful if you dont use the extra heat/expanding gasses it creates.

But this idea wouldn't let the high pressure "leak" between the turbine blades as axial & centrifugal turbines do, it would be sealed (for want of a better word) the same way as Piston & Rotary engines are.

Also, it would have the advantage of the regenerator to recycle any extra heat. I think this could be more efficient than previous attempts at turbine cars which were let down by fuel usage (The issues with lag would also be reduced).
-- Bal, Oct 21 2004


I'm probably all wet but I thought the term "turbine" applied to an engine where the inertia or kinetic energy of the working medium (gas or liquid) did the work. Instead of Positive Displacement Gas Turbine it should be called something like "Separate Combustion Chamber Rotary Engine". With separate components doing compression, combustion (gas generation) and power, over heating would be a severe problem in the power section, even worse than a Wankel engine where a rotor segment is only in the heat one fourth of the time..
-- hangingchad, Oct 25 2004


[Ling] Ah yes, the Starrotor also discussed in the Claw Pump thread is entertaining the same idea; a gas turbine with PD pumps for Compressor and Turbine. Theyve settled on the star pump often used in oil pumps, which I guess might not create the best torque in the turbine/expander. Although I like there sliding valves to vary pressure in the pumps.
-- Bal, Oct 26 2004


Great! I had an idea like this some time ago. The principle is the same.

My idea was a line-engine with one multi-cylinder crankshaft, with smaller pistons that pump air to the external combustionchamber, and larger pistons that produce power from the hot gasses coming from the combustion chamber.. (operated with valves like a steam engine) Preferable the pump pistons have an adjustable stroke to regulate the pressure balance. (Difficult to to do with a rotary compressor)

The "turbo-lag" effect will still be there. opening the throttle in a normal internal combustion engine gives you instant full pressure in the combustion chamber, and you can add the maximum amount of fuel. In the external combustion chamber version you cannot add more fuel than the amount of air inside will burn. At every revolution the pressure will rise a bit, and you can add more fuel. When shutting the fuel totally off, the engine will probably run idle as long as as the combustion chamber is red-hot. It will act like a hot-air engine.

The engine could run very (very!) slow, maybe it could even be selfstarting just by heating the combustion chamber from the outside, On the other side, when you rotate the crankshaft to create an airflow for starting, you don't build up pressure, you just create a vacuum...

Operating pressure would be much higher than in a gasturbine to get some reasonable torque.

If a red-hot-heat resistant pneumatic motor does exist (wich i don't know) a total rotary version would be possible i guess...

(btw, One big difference between a turbine- and a piston/rotary compressor If you block the airflow of a piston (or rotary) compressor it will run heavier. If you block the airflow of a turbine compressor it will run lighter and speed up...)

Baked, but not economically interesting i guess. But i like the idea!
-- windmill, Oct 27 2004


I was thinking of a similar idea recently, and there are two main advantages, an engine that only rotates is almost vibration free, and any continuous burn engine (turbines, boilers, bunsen burners etc) have the capability to run on anything that flows through a pipe and burns. The advantage here is that come the end of the world, you can still cruise around in your car on scavenged crankcase oil. Alternatively during wartime/fuel rations you can cruise around on similar things.
-- BLSTIC, Aug 27 2009



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