I haven't actually made the combustor yet (apart from a cardboard mockup) but this is what I intend to try first.
The exploded * combustor diagram.
The main housing of the combustor (grey) is a piece of steel pipe 100mm in diameter and 250mm long. On either end is a flat flange with six equally spaced holes to allow attachment of end plates. Between the combustor housing and the turbocharger exhaust inlet (brown) is an adapter plate (blue).
The adapter plate has two rectangular holes that exactly match the two rectangular inlets on the turbocharger. The plate has studs attached to either side. Four studs on the turbocharger side match up with the four mounting holes on the turbocharger exhaust inlet. Six studs on the opposite side of the plate match up with the six holes on the end of the combustor housing. The adapter plate also has a special fitting (pink) that couples the end of the flame tube (purple) onto the plate. This fitting matches the circular end of the flame tube to the rectangular holes in the adapter plate. The flame tube is a slide fit into the circular part of the fitting and this locates the flame tube centrally inside the combustor housing.
The flame tube will be made from 57mm diameter exhaust tube approximately 230mm long and it will contain holes along its length to allow air to enter the tube in a controlled manner. I haven't yet worked out what I think will be a suitable pattern of holes. The idea is to have three regions of holes. The primary zone, which is closest to the fuel injector and spark plug, is where you need to achieve the correct air/fuel mixture for combustion. After the primary zone is the secondary zone. Here extra air is added to complete the combustion. Finally, just before the hot gases enter the turbocharger, there is the dilution zone. Extra air is added to help cool the combustion gases before they impinge on the turbine wheel. The flame tube will need a lot of tinkering to get right so it is designed to be easily removed from the combustor housing. As a first attempt I will try having 15-20% of the air passing through the primary zone, 30% through the secondary zone and the rest in the dilution zone.
At the other end of the combustor housing is the end plate (blue/green). In the center of the end plate is a threaded hole into which the fuel injector is screwed. The injector consists of a brass hose fitting with a copper tube soldered to the inside of it. The copper tube is squashed almost flat at one end. The flattened end will spray the LPG fuel down the center of the flame tube. Next to the injector is another threaded hole for a normal automotive spark plug. The spark plug gap is opened up to around 3mm. The ignition system I am using will actually generate sparks over 10mm long.
On the side and at one end of the combustor housing is attached a short tube 50mm in diameter. This is the inlet where air from the turbocharger compressor is introduced into the combustor housing. My current plan is to have the air inlet positioned near the adapter plate end of the combustor. Air entering here should help cool the hot end of the flame tube and also, as the air is not blowing directly onto the holes in the flame tube, it should not affect the shaped of the flame. The combustor housing is symmetrical apart from the air inlet. The end plate and adapter plate may be attached to either end allowing me to have the air inlet positioned near the fuel injector. This seems to be the more usual way of doing things so I wanted the option of doing things this way if the need arises. A short piece of rubber hose will duct the air between the turbocharger compressor outlet and the air inlet on the combustor housing.
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These are some pages I found useful, informative and inspirational.Yahoo groups DIYGasTurbines
Formally eGroups, now Yahoo, page on do it yourself gas turbine engine building. A great place to get information, ask questions and share ideas with other turbocharger based jet engine builders.Aardvark's jet engine projects
Bruce (a fellow Kiwi) has lots of information on his turbocharger gas turbine as well as his pulse jet projects. He also describes his gas turbine powered go-kart, his pulse jet kit sets and he even provides a FAQ for other turbocharger jet engine builders.Mike's home built turbojet engine
I found Mike's page very inspirational indeed. He built an engine using standard metal pipe fittings and easy to get components. Presented as a day by day account Mike gives a lot of useful information with photographs as well.Turbocharger based gas turbine engine
Another home made jet engine made from a Holset diesel engine turbocharger.The Berndt turbine project
Robert Berndt's beautifully made turbocharger gas turbine.Jan's hobby page
Kenneth Møller's home made jet and pulse jet engine
Even though these pages are different Kenneth and Jan's engine is a joint effort by the both of them. Their engine is built from a KKK truck engine turbocharger. Between them they give a lot of useful information and pictures about how they built their engine. Kenneth also provides a great archive of pulsejet plans and designs.Technologie-Entwicklung Baumgart
Thomas also has a turbocharger gas turbine engine as well as Solent gas turbine starter.Gas turbines
Patrick Arnold's self contained KKK turbocharger based engine.Nye Thermodynamics
Many interesting gas turbine projects including the NT/5 turbocharger gas turbine (with afterburner) and the NT/6 wood burning gas turbine engine!Chris's Turbines
Chris has a very nice engine and some fantastic afterburner shots! Also described is an engine he has made using a huge Schwitzer D6S turbocharger originally from a M-60 tank!Turbocharger turbine page
Another turbocharger based gas turbine as well as some information on gas turbine starters and APUs.Mitch's Jet Engine Page
Mitch is building an engine at school with a turbo from a 1985 Nissan 300Z.Britannica.com - Gas turbine engine
The Britannica online entry on gas turbine engines.Rolls Royce - How a gas turbine works
The Rolls Royce (who know a thing or two about jet engines) education page on how a gas turbine works.Howstuffworks - Gas turbine engine
Howstuffworks entry on gas turbine (and jet) engines.NASA Glenn Learning Technologies Project
Lots of information about jet engines on this NASA site including some rather interesting applets to play with.Quest for Performance: The Evolution of Modern Aircraft
Another NASA site not entirely about jet engines but a fasinating (and long) read. Part 2 give a lot of interesting information about jet engines.Fundamentals of aircraft power plants
U.S. Department of the Army field manual all about gas turbine power plants. Viewable online as well as downloadable.Back to page 4 contents