The following is a turbojet build log by Kenneth Moller and Jan Petersen.
You can also find some truly fabulous build logs in the pulse-jets.com forum.
After studying Springer's and other's Jet engine project , Jan Petersenand I, decide to try start building a low-cost Jet-engine late Feb.97.
|After problems getting a turbocharger for a reasonable price, we finally got a KKK truck charger,in god condition for (kr200 / $40).Next we experiment a lot with a AUDI oil-sump pump, but ran in problem, so we decide to get the oil tank build, and because I know one who could TIG weld one in stainless-steel, the test stand was made of same material . A spring loaded sledge that run on four small bearing make it possible to measure the trust.The flame tube was also made of S/Steel, and once again I was able to obtain some 3" tubes for a sum of (kr50 / $10).So until now the budget is very fine.|
|The combuster was made of ordinary 4" steel tubes and welded on a 3mm plate for connecting to the turbo chargerThe top of the combuster is made (once again) of a S/Steel ring that fit into the combuster and tapped with 3 bolts.On this ring the flame holder is CO2 welded so it easily can be removed. On top we fitted a thick 8mm Alu plate that gives enough room to hold a automotive spark-plugs, and in center a hole for the gas nozzle.We use a high voltage transformer (10kV) from an old house heating unit, to ignite, and a large radial air-blower to start the engine,all found on a re cycling station for free.|
A 11 Kg propane cylinder feed the system. The regulator for the propane , high pressure hose and fittings cost (dk500 / $100),expensive but a good safety investment. "Some time ago a propane cylinder explosure totally rasure a hole building block near by, because of a non legal regulator !"
The Audi pump was changed with a Escort MkII pump and fitted on a brass plate where two 10mm copper tubes where solded on,for connection to the hose. After trying with a 75 Watt motor, we soon discover we need more power, so a 0.5 Hp motor came in place. Now we have a stable pressure but the coupling between the motor and pump is to wear.
Today we finish the oil pump and assembled the hole turbine for the first run. After an hour we were ready. The ignition function very well after we have made a little hole in the nozzle so that a bit of gas streams backwards to the spark plugs. With the radial blower the turbine ran very slowly, but after ignition it starts to accelerate.Every time we disconnect the air blower the engine stops ! We have no EGT(exhaust gas temp.) sensor and no RPM counter, so it was a little delicate to run with to much pressure for longer time. After cooling down the turbine wheels, we tried to boost with high pressure in short intervals too extend a reasonable EGT.Now we got a further acceleration and soon we could hear the compressor start working with a loud wizzle. After disconnection of the blower it runs. !!!! Yeah..With no rews and EGT sensors we only runs for shorter times (about 30sec.) but have made about 10 starts.
We have start to made a RPM sensor out of a infrared diode (from an remote cont.)After cutting the diode to 3mm thins the diode and photo transistor only measuring 10mm sq. We reflect the light on the bolts holding the compressor wheel, since we got 6 pulses every rews, it can feeds a ordinary freq. counter and readout RPM/10. It's go fine with a drilling machine driving the turbine with 2600 RPM, so hopefully also with 60000 RPM or more.
The final finish was made today , and a control board was made to all the instruments, we also modify the flame holder by reversing it (it contain only holes in the half of the length) and we run a test only on the combuster, but it did not work, so back to the future.! It took a lot of work, so when we finally fix it and get on with the new RPM counter, it also don't work, no read out.! Now matter, the jet should run today but it would not.... great flame out's ! Could it be our modification that have mismatch the hole burning. It have been late and we interrupt for today, a real bad bad day.
We have got the RPM counter working by adding a amplifier to the photo transistor, it consist of a op amp (LM358) in a self adjusting coupling so it compensate for fault light influence, and it works great.Schmatic Also the diode is deliver more power (80mW). We have tested to 60000 RPM with a small DC motor and a disc, we need a larger discs to exceed 100.000 . It measure up to a range of 6 cm. We decided to test the engine with the new RPM counter. The result... it suddenly run ? . But we have figure it out .! The oil is too cold or to thick, with a temp. of 40 deg. cel. the turbine began to run much smoother, so all the problems we had the last couple of days where solved. Success, and we run it for more than an hour.
Our new RPM counter were mounted today and the engine started. We began heating the oil to about 35 deg.cel. (we need some thinner oil) with a pressure of 3 bar. After acceleration to 20.000 RPM the engine run by itself. With higher oil temperature (we measured 60 deg.cel.) the oil pressure lower to 2 bar. and RPM raised to 31.000. But we have too low gas pressure to go further, so we measuring the lowest self running RPM to 18000 with 60 deg.cel. oil temp. With lower oil viscosity the engine will run much better. We were surprised about the low RPM, so our concern over to high rews in the past were eliminated. It would be interesting to measure the trust, but we haven't yet fitted the spring on the sledge, but our guess is (4-5Kg/50N).
Yesterday we re designed our flame-holder, and have build it today. With a combuster-test we notice a much cooler outlet, so we were excited to see the performance.! It works much better, than the old one, with 45000 RPM we mess only 764 deg.C EGT, and notice that when the engine excite about 35000 RPM the EGT lower from around 800 deg.C. down to 764 deg. So with more revs we will hopefully get a further decrising in EGT. We couldn't reach higher revs because the propane only aloud 2 bar of gas-pressure. Only a few experiment have been made with the diesel inj. system, but hopefully we will get more time for this system soon.
|17/8-97 Sorry for the long delay, but today Sunday we made our first run on diesel fuel.|
The last couple of weeks we have made some experiments with home made injector jets for diesel, but the didn't perform proberly, so we decide to buy a Danfoss injector jets for central hous heating systems. It's only cost 90Kr./15$ and could be ordered with flow from around 1 Liter to 100 Liter or more /h. We got one with a flow of (10.4 Liter/3USG)/h and it perform excellent with a very good atomisation.The high pressure pump also comes from a oil burner system, and are driven from a DC motor powered from a variable power supply. On our first attemp we have mounted a simple gas nozzle that ignite with the old sparkplug, and then by running the pump we ignite the diesel. Later we discover that the diesel have so good atomisation that it could be ignited directly by the sparkplug. The first combuster test was wery promising, but with full throttle it produce a little to mutch flame out. Mounted on the engine it's soon become a problem so we made a few modification on the flame holder, and came out with a reasonable result. On the first attemp we nearly got affrait of it! It accelerate tremendes , from 3000 to over 15000 rev in a second !!. Finaly we came out with a top rev of 35000 and a EGT of 800 deg.C.
Next we will try to seal the hole compressor system because we lost to mutch air pressure, so mabe that give us more rev and lower EGT.
I have nearly forgot to mentiod that we have change the oil. Now we use automatic transmission oil that have a wery low viscosity and therfor reduce the friction in the hydropnomatic bearings, it's cost about the same as normally mineral oil, so it's a good alternativ to full syntetic oil.Sametime we have rearrange the drainline on the turbocharger so that it now point directly downward, that have solve our problem with oil leak into the hot turbine and eliminate the great smoke cloud that sometime appear.
The development continue, stay tuned...!
|We are currently working on the new project but have no images to show, therefore I will try to explain about our plans and status right now. |
The major problem our jet engine is the physically volume and the heavy weight.
We have got another KKK charger and are in the situation that we could use the old one to improve new designs and run performance test.
Its possible to start at year zero, and make a completely new design without having to scrap the old engine
and finally by changing to diesel fuel we could design the engine for that system from the beginning.
|We will try to build a compact engine by mounting the combustion chamber axially to the turbine so it point parallel to the exhaust cone. The length of the combustion-chamber will be 42cm. and the clou is that we make it square, so the turbo are sitting on the one end of the square tube, inside we use a ordinary round flame holder. The problem is that the flame holder must have a 90 deg angle at the end for connecting to the turbo, and that make it a bit tricky to manufacture. The exhaust tube or cone will be as long as the combustor-chamber and give enough room for an eventually afterburner. That means that the engine will have this overall dimension. |
The lubrication system will be of much smaller dimension, with a smaller pump driven with at 12 V DC motor, and the liquid oil mass will only be 0.5-1 Liter with a copper-tube cooler of up to 2 meter length maybe arranged in front of the compressor. We have also made some test with a electric starter motor couplet to the compressor nut through a silicone hose, and that seems weary promising, up to 10000 rev with a tiny high-power scale racer motor, so maybe with a gear ratio of 3:1 we could make a electric miniature starter.
Our experiment with diesel fuel on the first engine have given us some good experience that will be transform to the second.
For the diesel injection we are using a small diesel pump that have prove to be ideal for our use, and also the hose and fittings for the high pressure system we have managed to overcome in a cheap way, we simply use normally air fittings and hose with a diameter of 4mm, that managed the pressure of 15-18 bar quite well. Same time we have got control over the ignition, and are designing it for a normally spark plug that have proven to ignite the atomisated diesel extremely well. Also the injector jets are been delivered from DANFOSS, we now have 7 different with flow of 1.4 - 10.4 - 12.8 - 13.9 - 17.3 liter/h and a spray of 80 deg.
Our plans from now is to build the new square-tube combuster_chamber and fit it to the old 14.1 version and from there develop it to perform as well as possible. That seems to be the best choice now, since the old combuster-chamber would need a fully redesign if it should run well on diesel. If that goes well we build the new engine and move the new combuster-chamber to that engine.
Soon we will update with some images of the new 14.2 combuster-chamber.
Note the oil tank arranged under the turbine, that aloud us to fasten the tank directly to the drain line. the oil pump and motor will be installed behind the oil tank, (not shown on the drawing).High pressure diesel pump, fuel tank and motor will be mounted on top of the engine, the diesel tank will have a volume of about 5 liter (W25 x L20 x H10 cm)
The hole engine will be mounted in a tube frame, so It easily can be implemented in a vehicle.
The current status are as following.
We have build a new combuster chamber for developing use only. It's made well long (~50cm) and are of ordinary round s/s tube, but equipped with the 90 deg. angle tube we intend to use on the rectangular combuster chamber.
The first tests running on the axial blower was pretty disappointing, the tube angle glowing bright yellow and we have seriously flame out problems. There was trouble with the fuel pump since it produce a oscillating flow , so there was thing to manage.
We found a failure on the pump, so after fixing it, we then have a stable pressure from 4-18 bar.
Next we fastened the combuster chamber on the engine, well knowing we would get problem, and that 's what we got. It was impossible to get self sustaining, the exhaust temp. was far to high, and there was also some nice explosions of unburned fuel collected in the combuster chamber.
It's a mystery, since the old combuster designed for gas, and running on diesel, was performing quite well.
I have lately got some good inputs from Peter(UK) to optimizing the combuster, so there will be some modifications soon, we maybe also found the major fault...? Our guess is ...! the injector jet we currently use is a S injector and the injector we used in the past was a H type, the different are unknown, but maybe by changing the injector we would solve the problems.
That's where we are now.
so stay tuned.
News, mostly bad but also few improvements.First, we have got self-sustaining with the new combuster,Yeh... but first after solving different bugs, and regrettably... only on gas. Argh...We have made dramatic changes to the combuster inlet by blocking the inlet near the top and made a new in the bottom, increased the inlet area and skipped the PVC tube we first used, now we use a flex tube of larger diameter than the PVC tube and have overcoming the restriction in airflow caused by use of two 90 deg PVC tubes. So the conclusion of that must be.. don't restrict the compressor outlet by using smaller sq. area and avoid the use of bending tubes with to sharp edges. Sometime we realize that the oil sponsorship' by Statoil was useless, since it cause to mutch drag on the shaft, and have change back to automatic transmission oil again.All that have improved the performance of the combustion but not yet to our satisfaction, still to high EGT. The problem is the flame front that is far away from the primary zone, and appear in the middle of the chamber, and we have realize that, after trying blocking and opening holes, adding thimbles and turbulator ring's, we need a other design.We think the output speed from the injector jet's is so high that the combustion is moved down the liner caused by the enormous fuel pressure. That can't be compensated with our low pressure, so with that in mind we thought of making a vaporization system instead. So... today We made a experiment with vaporization..We took a 10mm tube, 20 cm long and fitted a short silicone hose to the one end. Made a small hole in the side and feeded a brass tube (2mm) into it and bend it 90 deg. The silicone hose was then connected to a blower through a adapter. The pump was connected to the brass tube and the pressure reduced to 3-4 bar. The tube was fixed in a old vice and heated with a propane blower, so...after heating to maybe 3-400 deg.C we started the pump and let the blower ignite the fog extended at the end. By adjusting the air we got a really nice flame, with right air/fuel ratio the flame was bright blue and burned completely starting at the end of the tube and extend 40-50 cm away.That seems to be a solution that's worth to try, so please stay in touch with more updates...who will be added in a few days when the whether aloud us to test.
Now there's really good news:
Today we took the combuster made for atomization use and transform it to work on vaporization.Yesterday we made a hollow endcone for the flame tube and fixed it today, same time we took a piece of s/steel tube, same as used for the test 21/11, 13mm sq. and 30 cm long, bend it 90 deg. at the one end so it could fit in center of the flame tube, pointing to the top (to hollow cone), fasten it half way down the liner (combuster well long 45cm) so we now have a central vaporization tube in center and pointing against the mass flow direction.
| On the vaporization tube inlet we took a pieces of brass, solded two 3mm brass tube on and fastened the plate with two 4mm screw so it easily can be removed to aloud the flame tube to be removed, because the two thin tubes stick about 10mm into the vaporization tube.The first tube is for diesel and the second for gas. |
The flame tube is shortened 7 cm to aloud air to surrounding the hollow endcone for cooling, there is no connection through the top plate more. Now we were excited to see who it will perform, so after connecting the diesel pump, gas and vacuum cleaner (the old radial blower, blow) we turn on the gas for heating the vaporization tube, and ignited it at the outlet, immediately the flame front disappear inside and to our amazement the combustion took place deep into the primary zone, a core with a length of under 10cm in the primary zone and the secondary zone completely combustion free, only hot gasses.We never seen combustion so concentrated in the primary zone, and when starting the diesel pump the flame front stay in same place. Only when making a very rich mixture the flame came closer to the outlet but newer exit the combustion chamber.
So... here is a drawing showing our current combuster design. The drawing is not correct scale, and the holes are not arranged correctly, but it shows the principal layout.
The air enter into the bottom of the combuster to ensure the highest pressure around the secondary zone. The gas inlet tube is only needed to preheat the tube to ensure that when the diesel enter, it immediately evaporate.
As described, the combustor have only been single tested, and we will probably continue with that until we have tested some optimations ideas, one of them is to make flaps into the evaporation tube to ensure the fuel hit the hot wall several times, and another is to try ignite the diesel without having to preheat the tube. The problem is where the spark plug should be placed. Maybe by making a small "external ignition Combuster"...?
|If anyone have plans for trying this design, the greatest problem must be the end cone. We took a round pieces of sheet and began hammer it out to shape, it took under 1/2 hour, so it was'nt so problematic as thought, but later we discover a soup spoon in the kitchen with exactly the same shape....! |
But peace must come in first place, so maybe it was the best solution.
Due to I have started studying, and my friend Jan is rebuilding his house, we haven't had the time in the last year to develop on our jetengine , but we are planning to continue , maybe later This year!.I you are thinking about making you own home made jet engine, the you should. It is very exciting project, but I will take a lot of you free time, but I can recommend it!
We have startet on our jet engine again.We have decided that we will replace the oil pressur bearing with ball bearing to reduce the resistance and make it easyer to make lubricate system.I Have contacted SKF (The inventor of the ball bearing), and asked them if they would like to sponsor some ceramic ball bearings for our project, and they would. So, now we are waiting to get them, and soon we will fit them on our turbo charger.!