homemade jet engine

[salah]

It seems that most of the homemade jet staff is based on auto turbocharger design'
Is there any homemade jet engines that are not based on turbochargers?

Thanks in advance,

[racket]

Hi Salah

Try the GTBA www.gtba.co.uk/

The reason turbochargers are used is simple , they're already gas turbines that use an IC engine as the combustor.

We use turbocharger rotors in our "Micro" type engines because they're perfect for the job , the compressor wheels are developed to a high level of efficiency and the turbine wheels are constructed of the same heat resistant metal as commercially produced micro UAV engines.

Cheers
John

[salah]

That is clear. But how much thrust or HP we can actually get?
What I mean is ,if the turbocharger of small Berkins generator gives about 100 wat of power ,can we actually get at least half that power when the turbocharger is removed and used as part of homemade turbojet.?

Unless it is made for fun!

[salah]

Sorry I meant 100 k watt of power.

[racket]

Its possible to produce ~25% of the power of the IC engine that the turbo came off .

My TV84 turbo came off a 475 HP Detroit Diesel engine , when made into a gas turbine with a freepower turbine for power production it produced ~115 HP

Cheers
John

[salah]

I plan for low pressure ratio 3.5 which mean my temp in the compressor outlet could reach 430 K ,but what would be the temp in the combustion and turbine inlet.

What happens if the inlet flow D is increased and the compressors press ratio as low as 3-4.?
What would happen to the temp increase in the combus and turbine inlet?
I need turbine inlet temp not to be more than 700 C,
Thank you in advance.

[racket]

Hi

With a T I T of 700 C your power production will be severely limited .

Combustion temperature in the Primary zone will be up ~2,000 C but the dilution zones will bring that down to your design T I T .

Its simply a case of adding or reducing fuel flow to change temperatures and pressure ratios when running a fixed "restriction" downstream.

Cheers
John

[salah]

Hi John
I would really appreciate it if you could post some pictures on your homemade installation assuming it is not a matter of national security.
And how come you end up with HP rather than thrust. Unless you have made a turboshaft.
And if possible the HP equations calculations.
Seems to much ,but I hope you will find to answer.
Thank you.

[racket]

Hi Salah

Checkout Anders build jetandturbineowners.proboards.com/thread/53/landspeed-bike-diy-gas-turbine for a homebuilt turboshaft , my TV84 bike build was started more than two decades ago , so no "digital" pics to share.

You could have a look at my 2 shaft kart build for a turbocharger based engine jetandturbineowners.proboards.com/thread/40/2-shaft-turbine-kart-build

As a very rough guide , we should be able to produce ~1 hp for every 1 pound of thrust from a pure thrust engine if a freepower turbine wheel is fitted.

There will be a lot of variables that can affect the outcome of any build so its impossible to give accurate data about what can or cannot be expected from using a particular turbocharger.

Cheers
John

[salah]

Hi guys
There is an expression that I keep reading in aerodynamics or turbojet staff it says :it is better to move large countities of air by low amounts than low countities by large amounts .

I got the idea that it means simply that for example (thrust of propeller) it is better to have large propeller D running at low rpm than small propeller D running at high rpm.

Now if that is the case, why don't we increase the inlet area (which mean large rotor D and higher mass flow and at the same time with low exit flow velocity ?
Would it give more thrust than smaller inlet D with high exit velocity?

[racket]

Hi Salah

Increasing inlet size is certainly the easiest way to larger power outputs , but we're already using very large turbocharger compressor wheels for our gas producers, there simply isn't any bigger ones readily available at reasonable costs , once into BIG industrial sized turbos you can buy a car for the cost of one of their compressor wheel .

Also weight starts to become an issue , it increases much faster than the mass flow increase, past a certain point it becomes easier/cheaper to buy an old aero engine .

Cheers
John

[salah]

Hi guys
I was out of coverage for a while.
And I can not seem to understand the ups of 2 and 3 spool jet stuff.
what I mean is why it is not possible for the single-shaft turbojet shaft to be geared down to lower rpm values (using gears) and then connected to propeller as turboprop or fan as turbofan or helicopter shaft?
Why does it have to be 2 or 3 shafts

[racket]

Hi Salah
Generally the gas producer runs faster than the freepower , so gearing from a single shaft is always at high rpm than if theres a freepower attached , this makes it a bit more difficult , but not impossible .

Because the single shaft produces all of its power in the last 10% of its rpm range it'd be necessary to have it spinning fast all the time and the load would need to be "adjusted" until the rpm are high enough to cope with it , for a prop that means a variable pitch required , for a land vehicle lotsa gear ratios whereas with a freepower we often only need a single ratio .

Cheers
John

[salah]

Hi guys
in the HP output of jet engines I found in one of the articles I have read so far that the HP can be found as:
Net HP =mass flow*1.005*(TIT-Temp of air out of compressor)*compression effiecincy.

Yet in same article in another example the HP was found as
net HP =mass flow*1.005*(TIT-exhaust temp)
I got confused little since the values of HP in the diffefent equations did not match .
Your help is of high concern

[racket]

Hi Salah

The horsepower produced by the turbine wheel can be calculated from the temperature drop across the turb stage .

If theres say a 100 deg C drop between T I T and TOT , we multiply that by 0.28 for our temperature level of hot gases , this gives us 28 , multiply that by 1400 and divide by 550 ( both constants) , this will produce a horsepower output of ~71 HP per pound of mass flow per second , there will then need to be an allowance for other losses such as transmission losses .

Cheers
John