The Green Turbofan is a efficient green energy solution based on the GE90-115B turbofan engine made by General Electrics.

GE90-115B turbofan. The GE90-115B turbofan is a milestone in turbofan design. It is twice mentioned in the Guiness Book of Records.

It is basically a stripped down GE90-115B turbofan. See picture 1, 1a and 1b. As the picture 1 shows, the combustors etc. have been removed. It is just the fan fitted with tip turbines

Picture 1 Picture 1a
Cross section view of the Green Turbofan Front view of the Green Turbofan
Picture 1b
Tip turbine

How does the Green Turbofan work?

The Green Turbofan is placed inside a long pipe. See picture 2.

Picture 2

 Flowchart Green Turbofan generating energy

Next, the air flow of a Siemens STC-SV centrifugal compressor is directed at the tip turbines of the Green Turbofan, making it rotate at high speed. A large volume of air is sucked in by the Green Turbofan at high speed. The air is compressed by forcing it over the inlet body, building up pressure and temperature. Next, the compressed air expands through an nozzle, into turbine of an generator, producing electricity. To reduce pipeline turbulence aerodynamically shaped objects can be placed inside the pipe.

Maybe it is possible to increase efficiency by using the Venturi effect (like it used in a ejector) and increase the air flow. Airflow A is split up (picture 2a) and pressure is build up at the nozzles. The high pressure, split up airflow A becomes the motive fluid, that draws in air (airflow B and C, which both mix with airflow A) and creates two larger airflows of intermediate pressure, each driving a generator. For instance the airflow in picture 2 is strong enough to power a 100 MW generator, the two air flows in picture 2a might be strong enough to power two 51 MW generators.

Picture 2a
Flowchart Green Turbofan generating energy using venturi effect

Feasibility and efficiency potential

The total air mass flow of the GE90-115B is approximately 3.000 lbs/sec or 1.360 kg/sec. Overall Pressure Ratio: 42:1 = 42 bar. Its bypass ratio is 9:1 (for 1 kilogram of primary air, 9 kilograms of bypass air are generated). The primary air stream driving the turbines of both turbofan and the compressors, has a compression ratio of 42 bar and an air flow of ± 136 kg/s. The bypass airflow is ± 1.224 kg/sec. For full specs of the GE90-115B click here.

Now, the Siemens STC-SV centrifugal compressor has an air flow of 133 m3/s = 133 kg/s, and an discharge pressure of 1.000 bar. Although its air flow is 3 kg/s less than the primary air flow of the GE90-115B turbofan, one should realize that the primary air flow of the GE90-115B turbofan has to drive the turbines of the fan and the compressors and has a lower pressure ratio. The GE90-115B turbofan has a pressure ratio of 42 bar vs the 1000 bar of Siemens STC-SV compressor.

Also the turbines driving the fan and compressors of the GE90-115B are a combination of reaction and impulse turbines. The tip turbines on the Green Turbofan are 100% impulse turbines, which some consider to be most efficient. For more information on impulse and reaction turbines see  https://en.wikipedia.org/wiki/Turbine and Pelton wheel.

It seems very plausible that a 133 kg/s air flow should be capable to give the Green Turbofan the same speed (rpm) as the GE90-115B turbofan and consequently produce an air flow of ± 1.224 kg/sec. This is about twenty times the air flow of the Kawasaki L20A gas turbine, which has an air flow of 58 kg/s.

Does this mean the Green Turbofan can drive the same generator as Kawasaki L20A gas turbine? If so, the Green Turbofan could drive generator producing 18.000 kW, over two times the power the electric motor of the Siemens STC-SV centrifugal compressor needs...

The potential of the Green Turbofan might even be greener. The General Electric GE90-115B has a thrust rating ranging from 360 to 510 kN. By-pass air is responsible for 90% of the thrust = 459 kN. If this thrust can be used to drive a 60 mHz (3600 rpm) generator, it could generate 173.047 kW = 173 MW*. This is 23 times the power the electric motor of the Siemens STC-SV centrifugal compressor consumes...

There might be another way to improve efficiency further by using a technique that is used in AA CAES plants (Advanced Adiabatic Compressed Air Energy Storage). Heat that was released by the STC-SV compressor during compression stages, can be stored in adiabatic containers and used to heat the air flow from the STC-SV compressor to the Green Turbofan (picture 3). During compression temperatures of 600°C are possible, so the airflow from the STC-SV compressor to the Green Turbofan can be heated to ~ 600°C! This might allow for a smaller compressor that consumes less energy, improving overall efficiency.

* A on-line calculator/converter was used to convert thrust (Nm) to power (kW).

Picture 3 - Green Turbofan using AA-CAES style heat recovery

Green Turbofan using AA-CAES style heat recovery

Feedback welcome

A crazy idea or do you think it just might work? Please give some feedback.

Thank for your time and visit!

Some videos you might enjoy

It is easy to spin a Turbofan by hand - click to watch video The GE90-115B is extremely well balanced and calibrated.
It needs very little energy to start.
You can turn the turbofan by hand.
(Click the picture to play the video).
Video shows how a jet engine is started by using a diesel powered compressor This video shows how a jet engine is started by a small gas turbine powered compressor.
Unfortunately, it only specifies the PSI (20), but does not specify the air volume.
(Click the picture to play the video).
Air cylinder rocket- MythBusters Fun - MythBuster Air Cylinder Rocket video
Air cylinder rocket busting through a brick wall and damaging another.
(Click the picture to play the video).


Technical specifications of the General Electric GE90-115B High Bypass Turbofan

General Electric GE90-115B high bypass turbofan
Type: Ultra High Bypass Ratio Dual Shaft Turbofan
Bypass Ratio: 9:1
Low Pressure Compressor: Single Stage fan, followed by 4
stage axial booster
High Pressure Compressor: 9 stage axial flow compressor
Burner: Double annular through-flow combustor
Turbine: Dual spool, 2 stage axial high pressure turbine, 6
stage axial low pressure turbine
Exhaust: Coaxial core and bypass jet exhaust
Thrust Rating: 115,300 lbs. of thrust
Weight: 18,260 lbs.
Thrust/weight: 6.3:1
Air mass flow: Approximately 3,000 lbs/sec
Fan Pressure Ratio: 2:1
Overall Pressure Ratio: 42:1
Maximum Turbine Inlet Temperature: 2,700F+
Specific Fuel Consumption: .25 lb/lbt/hr
Fuel Burn at takeoff: 3,750 gallons/hr

Source: www.turbokart.com

Technical specifications Siemens STC-SV centrifugal compressor

1000 bar Siemens STC-SV centrifugal compressor
Volume flows from 250 to 480,000 m3/h – 133 m3/sec (full power)
Discharge pressure up to 1,000 bar
7.5 MW electric drive, powered by Siemens SGT 200 gas turbine which consumes about 25 MW.

Technical specifications of a Kawasaki L20A gas turbine

Technical specifications of an Kawasaki L20A gas turbine