The mark II turbojet is similar to the mark I in the respect that the basis for the project was a turbocharger. The turbocharger that I bought was, and still is the biggest I have ever seen in person!
The engine used a much more complex combustion system than the previous attempt, consisting of a flame tube, with much more distinct 'zones', and a set of swirl vanes to promote flame recirculation. The fuel was delivered into the chamber by no less than three methods. The first point of entry was a small propane jet which was lit by the spark ignitor and served only to initiate liquid fuel ignition. When the second fuel input device, an atomisor nozzle rated at 0.5gph was lit the gas jet was switched off. The atomisor nozzle provided a means of keeping a constant flame in the chamber which preheated the vapourisor tubes. This type of nozzle, which was designed to be used in an oil fired furnace, is only designed to be run at about 90psi. If the fuel pressure was lowered by too much then the spray pattern suffered and poor combustion took place. To run my jet from one of these nozzles alone would require one with a rated flow of about 10gph to give full rpm. If I dropped the fuel pressure enough to run the jet at idle with such a large nozzle the fuel spray resembled a garden sprinkler instead of the mist which is seen when running at 90psi. I decided to use a small nozzle at constant pressure to give the preheating effect on the vapourisor tubes at startup, and a set of 6 vapourisor tubes. The tubes carry air from the compressor into the core of the primary burning zone of the flameholder, fuel is injected from a manifold into the mouth of the tubes which mixes with the air, and vapourises due to the heat, providing a very combustable mixture. This mixture is inserted into the primary zone where it heats the gasses flowing through the engine. The engine was started using a home made blower. The blower was basically a big wooden box containing six 1000watt vacuum cleanser motors. The blast of air from my blower never failed to impress, it was also extremely noisy!
This is the base of the combustion chamber showing the gas jet entering the flameholder. The brass fitting on the left is the check valve to prevent air back flowing down the pipe when the combustion pressure rises.
These are two of the oil fired boiler injector nozzles.
This is the aluminium base of the flameholder. It incorporates a set of guide vanes, and an adjustable stainless steel collar which varies the flow of air into the primary zone of the flameholder. This reduces the development time as adjustments to air apportioning can be done quickly without the use of a drill and welder!
This is the combustion chamber air casing, during construction. It has adouble skin which forms an air jacket for the charge air from the compressor to pass down into the combustion chamber. This gives a cooler, safer chamber when running, but most importantly it means that the cold air is being added to the chamber from all sides at once. This gets rid of the associated problems with dumping all the air into one side of the chamber such as uneven combustion duw to the flame being fed from one side more than the other.
This shot shows the combustion chamber mounted on the turbo, the blue silicone hose seals the compressor discharge pipe to the chamber inlet pipe. The pipe going to the top centre of the turbo centre section is the oil feed and the object entering the exhaust pipe is the EGT thermocouple.
This view shows the top of the assembled combustion chamber and it's associated pipework. The pvc pipe carries the propane to the gas ignition jet, and the stainless overbraided hose is the main liquid fuel supply to the atomisor nozzle. The vapourisor manifold had not been fitted when this photograph was taken.
This is the fuel pump, also from an oil fired furnace, fitted to it's motor. It provides constant pressure governed by an internal adjustable pressure relief valve.
This is the turbocharger in pieces prior to inspection. The shaft can be seen at the bottom with it's hydrodynamic bearing cartridge fitted with the compressor on the left, turbine on the right.
This is the assembled rig ready for test running.
This illustration shows how the flame should behave in a gas turbine combustion chamber.
Unfortunately, due to the noise level of the engine testing was rather antisocial in a residential area like the one in which live, couple this with the purchase of my Lucas APU, and my lack of time to spend on the project I decided that I would be better off working on a smaller project. I sold the engine complete and will post updates on it's final development when they arrive.