Turbo jet plans

[endersworld]

New guy here, wanted some feedback on a project I'm working on.

Based on what I learned from my ramjet experiments I threw together this design for a turbine jet. Its currently under construction and should be complete and testing soon.

Jet body with turbine parts extracted




The bearing is from the pedal axle of a bicycle, and the turbines will be mounted on steel pedals that I have cut down and rounded. Attached to the rounded pedals will be brackets that the turbine blades will bolt to. This will allow me to adjust the angles of the blades, hopefully giving my simple design some leeway as to RPMs and the pressure in the combustion chamber.

Brackets and blades


Ill test combustion with the compressor and no exhaust turbine so I can calibrate the blades and the fuel mixture. I'm starting with propane or MAPP gas, then moving on to pressurized gasoline.

View through


Thanks for reading

[racketmotorman]

Hi Enders

I'd suggest you do a lot more research before going any further , the current design has virtually no chance of working , even if you get it to spin around the design is so fragile that wheels will explode.
There is a good book by Thomas Kamps ,Model Jet Engines , Traplet Publications , try their online shop

Cheers
John

[endersworld]

Thanks for the input, Ill look into those. I've already begun construction though, and it seems fairly sturdy so far.
i probably wont have a straight tube, but some sort of venturi before or after the fuel injection.

heres the turbine so far


the bars holding the brackets are a little thicker than in the 3d model

[racketmotorman]

Hi

Please STOP construction and start reading , this engine WILL fail in its current configuration !! ..................it is no where strong enough to cope with the massive forces involved .

How big will the turbine wheel be ??

What rpm do you plan on using??

Do you know what idle speed ??

Cheers
John

[endersworld]

I did do lots of research, here's something I used to plan


I'm really only going on basic principles, not getting into efficiency right now.

The complete turbine should be a little under 6 inches diameter, but the blades will only be 1.5 to 2 inches long. I plan on powering the compressor turbine externally first with a motor, so i can adjust the blade angles optimally. When I get the combustion chamber complete I will be able to determine the RPMs. I still need to finish my plans for a liquid fuel delivery system, because I want a readily available liquid fuel instead of a gas.

here's the bracket hub now completely welded


I just need to drill the bolt holes in each plate and weld the bolts to the bottom of the blades. Then I can bolt them to the hub and bolt the whole assembly to the bearing.
I would like this completed jet to have low rpms, somewhere in the range of 1500 to 4000. I'm not really sure if it can operate that low, but achieving high pressure combustion is my immediate goal.

here are some videos of the ramjet tests
http://www.youtube.com/watch?v=9fwfS1pW ... re=related
http://www.youtube.com/watch?v=lo-pgY4d ... re=related
http://www.youtube.com/watch?v=He0EKxru ... re=related
http://www.youtube.com/watch?v=_I1QouK0MRI

[racketmotorman]

Hi

A 6 inch diameter axial turbine engine would normally run up to an rpm of ~ 60,000 , with idling rpm of ~30,000 rpm ( 50% N1) .

A single stage axial compressor will produce a pressure ratio ( PR) of maybe ~1.6 :1 from a transonic wheel , whereas a "normal" axial stage will produce a PR of ~1.2 :1 or ~3 psi of pressure from a single stage .

Your turbine flow area is roughly the same as your compressor , you'll have "choking" of the flow with the compressor wheel surging long before you can get up to self sustain rpm of perhaps 20,000 rpm ....................you will never get the engine to run at 1,500 - 4000 rpm , turbine engines require extremely high rpm/blade speed to work , and this also require very fine balancing of the entire rotating assembly .

Please go to the GTBA Site for more info on axial engine design http://www.gtba.co.uk/ , before you go any further .

Also have a look at JATO Site http://jetandturbineowners.proboards.com/

And Yahoo DIY Gas Turbines http://groups.yahoo.com/group/DIYGasTurbines/ where you'll get information on making a gas turbine engine from a turbocharger .

Sorry to be so negative about your creation but its better for you to stop now than to continue and inevitably have failure

Cheers
John

[endersworld]

But its almost done, and I could stack more turbine hubs to make a multi-stage compressor. I don't expect this version to put out a lot of power, or even sustain itself. The main goal is to do away with the air compressor and create a more compact system.

[racketmotorman]

Hi
If you want to finish it, go ahead, but you're wasting your time and energy doing it , ...............an axial compressor is a very complex piece of equipment , making one is beyond the most experienced home turbine builder , just looking at the pic of your blading , there doesn't appear to be any "twist" in them to cater for varying blade speeds between root and tip

What do you mean by your statement about....... "creating a more compact system" ??

Theres plenty of plans available for making homebuilt turbine engines that can work , your design isn't one of them , I'd strongly suggest you change your development direction , I've been playing with homebuilt engines for ~20 years and have built a few http://www.youtube.com/my_videos?feature=mhee so have a fair idea what will or won't work .

Cheers
John

[multispool]

Thread title says plans, Just wondering what planning has been done?
Would be interested in what calculations you have done?

Don't forget that with an axial Compressor stage, the pressure rise is created by diffusion, which is something that needs calculating for any chance of working.

Basically it won't run with such a low pr, so shouldn't present a danger....

[endersworld]

The blades are incomplete, they still need to be sanded to the same size and twisted. Ive updated my plans a little after comparing the blade/hub assembly to the jet body I was going to use.



The hub was larger than I expected, and would have only allowed me to have 2 inch blades. The larger diameter shroud will let me have blades more like 4 or 5 inches long, and the cone shape into the smaller combustion area should increase pressures from the turbine.

By more compact system I meant not use an external air supply, like the heavy, loud air compressor from the ramjet tests.

Thanks for all the feedback by the way, its helping me consider what forces I can expect to be dealing with.
John, can you post direct link to one of your videos, the one you put before led to my video page list.

[racketmotorman]

Hi

Heres Links to some of my creations

http://www.youtube.com/watch?v=q_MRUxWEOZ0

http://www.youtube.com/watch?v=F-fci_AlNMU

http://www.youtube.com/watch?v=VX5U8DlBzzk

http://www.youtube.com/watch?v=8Y8jpaDTkEY

http://www.youtube.com/watch?v=NR0rsTbkOS4

http://www.youtube.com/watch?v=WfWztBRW8W4

If you try to "force" the air exiting a "large" low pressure compressor stage into a "small" combustor all that will happen is the compressor will surge .

4 or 5 inch blades on an axial compressor would normally mean a mass flow up in the 30 lbs/second range , requiring your turbine wheel to produce a couple of hundred horsepower to drive just that single stage

The full sized turbine engines can use small combustors because of their high pressure ratios , you will need an over sized combustor and turbine stage to drive your low pressure ratio compressor .....................you need to do more research/reading on the subject .

Many years ago I wrecked a couple of expensive large turbos trying to make a working gas turbine engine , eventually I had to do more research to stop me making the same mistakes you are , so please take advice from someone who has had to pay the price for their lack of knowledge .

Cheers
John

[endersworld]

How did you do the transmission for those vehicles? With the rpms being so high. Was it a friction clutch to chain drive, or was the output geared down then transferred to the chain and rear tire? I put a 7 horse rototiller motor on a bicycle, it uses a centrifugal clutch pulley and a pulley attached to the drive train of the bicycle.
It gets me around 40-50 mph.




what is surging?
If its at a constant rpm will the surging only be on starting?

The exact dimensions of the blades will probably be 1 inch by 4 inches. If I don't alter the combustion chamber as it is now, there would be approximately 141 cubic inches of space and the bearing will be in there taking up about 1/4 of that space.

[racketmotorman]

Hi

Heres a Link to my bikes construction http://www.ivcity.com/john/index.html , when a freepower turbine is used downstream of the gas producer there isn't a need for a clutch and/or multi speed gearbox as the freepower wheel acts as a torque convertor with gases as the driving "fluid" .

Thread build of the kart .... http://jetandturbineowners.proboards.co ... &thread=40 it used standard karting sprockets and gearing .

Surging is where the compressor supplies air intermittently due to there being too much restriction downstream .

Combustors are designed for a "Combustion Intensity" .............BTU's/cubic foot/atmosphere/hour , somewhere ~2million is a good figure to start at.

Your 141 cubic inches is way too small , I use that sort of volume for a compressor wheel with only ~10 square inches of inlet area , the combustor's cross sectional area needs to be ~3 times the compressors inlet area , so ~30 square inches for my combustor's flametube , this provide air velocities slow enough for combustion to take place when air pressures are low .

We need a certain temperature rise across the combustor to make our engines work , in most cases this is at least 400 deg C just to idle the engine

Please join the Yahoo DIY Gas Turbines Group , there is a huge amount of information on the Site that you can access .

Cheers
John

[endersworld]

Those machines you've built are incredible, pneumatic turbine powered... I had only really considered these jets for their thrust output.



I just finished welding all the blades to the bolts, and this thing is really kind of cool looking now.



The next step is to duct the turbine, power it up and observe the airflow. Still need to clean up the blades shape them better.

Before I even started this I wanted to mount a turbine directly to a gas motor and not use an exhaust turbine. Does this have any potential? I could use either a small 2 stroke or a 5-7 horse motor. There would be no need for bearings or moving parts, except for the motor. This would not be a true gas turbine though and would add weight and complexity to the system as a whole.

[racketmotorman]

Hi
Our DIY engines make acceptable thrust , the one in my bike video produced ~110 lbs of thrust as a pure jet , but with a freepower turbine downstream , I used a third stage Allison C20 heli engine turbine wheel , produced 115 rear wheel horsepower on the dyno . http://www.youtube.com/watch?v=CplnY9TG7NE.

Our current bike build uses the 10/98 "micro" engine with ~40% more airflow 98mm comp inducer vs 89 mm for the Garrett TV84 turbo , and should produce ~150 RWH in a bike weighing ~150 Kg - 330 lbs compared to the first bikes ~280Kgs- 600 lbs ........................this bike will use the Allison C20 4th stage turbine wheel for the freepower turbine ...............its ~8.5 " diameter and will spin to ~32,000 rpm , the 10/98 gas producer spins its 5.55inch diameter compressor to ~70,000rpm at full power .....................the compressor wheel consumes ~230 HP .

A 7hp IC engine will spin your "fan" and blow some air , but it won't produce much pressure , pressure requires lotsa horsepower at the airflow rates that we use in a turbine engine .

The TV84 in the bike video consumes ~1.8 lbs/sec of air , thats ~24 cu ft/sec - 1400 CFM , the 10/98 engine close to 2000 CFM , your MASSIVE wheel could be flowing several thousand CFM if designed correctly ..................that is going to need huge amounts of HP.

Heres some maths for you to digest ..............assuming your axial compressor wheel is 10" dia with a 2" dia hub , thats a flow area of ~75 sq inches or ~0.5 square feet ,..................now axial compressors have inflow airspeeds of say 500 ft/sec , so ~250 cubic feet /second of air -15,000 CFM or ~19 lbs/sec mass flow .

If your compressor wheel attains a nominal 1.2:1 pressure ratio then there would be a 15.4 deg C rise in the air temp if the compressor is 100% efficient , your will be lucky to be 60% effic . , this will mean a temperature rise of ~26 deg C , to "convert " that 26 degrees into horsepower we do a bit of simple maths and it comes out at 15.7 hp/lb/sec , multiplied by our 19 lbs/sec and we get a horsepower requirement of 298 horsepower .

A 10inch wheel with a 1,500 ft/sec tip speed will rotate at ~35,000 rpm , assuming you wish to run the wheel at 5,000 rpm , pressures go up at the square of blade speed , you will get only 2% of the max pressure rise , 2% of a 1.2 pressure ratio is ~2.5% of ambiant 14.7psi or ~0.36 psi or ~8" of water , this is about what a leafblower turns out , now there will be a temperature rise of ~3 degrees , but you'll never get to this point because the power requirement is too great for a 7hp engine to spin even if airflow rates were reduced to half , you'd need to adjust your blading to a fine pitch setting and reduce flow appreciably .

This is not a workable proposition , please change your direction and start using much smaller components , this current design isn't workable , and I'm not going to waste anymore time explaining why , get yourself some turbocharger bits which have some hope of working .

Cheers
John