Tampereen suihkuvoimatekniikan klubi

Presents

New improvements of "Eunuch 2".

The turbine seize.

The air starter unit had caused us lots of trouble. Even more than the jet itself. So this time we decided to finally get rid of the extremely unreliable and noisy two-stroke engine. We replaced it by the electric motor from VW beetle that we used before. Only this time we took a 2.5KW transformer. The power from the transformer was finally enough and we built a starter system with it, a rectifier bridge, two mercury-wetted relays and a power resistor. We put the whole system on a wheeled trolley so the heavy transformer would be easier to move. It now has a switch box where full power for starting and half power for jet cooling can be selected. The system has also a 4000V 50mA neon sign transformer to be used as an ignitor if the system built in the moped should fail.

So when the spring started we rolled the bike out of the shed and started it. Surprisingly the system worked just fine at the first attempt. We took it to the parking lot where the annual university drag race is to be held just to ride the lane couple of times. And since the jet worked we took it there not later as at the evening before the race. For some reason the engine didn't get the revs as easilly as it should and suddenly it gave out a loud screech-bang - like sound. We noticed that the shaft couldn't be turned from the compressor wings and guessed that the turbine must have seized. There were only one night before the race so some of us started to dismantle the engine while others searched a new turbine-shaft assembly. We managed to get one at the morning of the race day and the engine started just in time.

Our investigation of the damaged unit revealed several cracks in the turbine. The cause of the incident was the axial bearings of the turbo. The axial clearance had grown too much and finally it allowed the turbine to move forward enough that it touched the turbine housing. The axial clearance should be carefully monitored when using turbo as a jet since the bearings wear much faster than usually.

Old steam engines meets Eunuch 2.

This time the jet didn't have any problems and we could start making some experiments. We found out that if a rapid braking is executed the fuel will splash forward in the tank and it might allow an air bubble to enter the fuel system. When the bubble arrives at the combustion chamber it will extinguishe the flame. The fuel pump is still running and the fuel keeps on spraying in the hot combustion chamber which vaporizes it creating a large cloud of smoke. It is however possible to re-start the engine if the driver is fast enough. The turbine-compressor assembly keeps on rotating for some time after flameout. If the spark igniter is activated fast enough the engine will restart. The time after which the engine can be started without external help is some seconds. In some conditions it might be considered quite a long time.

New! This link takes you to the "Kowan Teknolokian Museo" the official webpage of the organizers of the happening. http://www.narva.sci.fi/museo/kowatekn.html where more pictures of their machines are to be found. The pages are in Finnish, but follow the links containing keywords "KUVA" or "KUVIA" for the pictures.

Alastaro racing center.

The battery system was a bit impractical since it used separate batteries for oil system and fuel pump. Another problem wast that the oil pump batteries were connected in parallel and which isn't a good practice when using NiCd batteries. The oil system consumed also too much power because it run on full power all the time. The pressure was ket constant with a mechanical pressure regulator that let some of the oil to circulate straight back to the oil sump.

The electric system was redesigned to work with 100V batteries. Two of the NiCd battery packs in series is supplying the juice and a new electronic chopper regulator unit controls both the fuel and oil pumps. The fuel system still works on manual control but the extra voltage gives higher maximum fuel flow. The biggest improvement was done with the oils system. The system now has a pressure transducer which measures the pressure and automatically adjusts the pump speed to keep the pressure constant. The igniter was also modified so it could use the higher voltage from the main batteries.

The fuel system worked almost instantly after adding just a few smoothing capacitors.
The oil system didn't.
The problem was an American made oil pressure transducer which didn't work properly. After we replaced it to a cheapest one we could find the system started to work. The mechanical pressure regulator is still needed. When the oil is cold the pump should run on extremely low RPM and the control system doesn't operate properly at such a low pump speed. So by keeping the old regulator in place the cold oil has some extra flow and the system works fine. When the turbo runs and heats oil the regulator will close and the electronic regulator can handle the situation.

The two main goals, reduction of power consumption and simplification of electric system to use only one set of batteries, were both achieved. A set of batteries now lasts about one hour or four full tanks of fuel before it must be recharged or replaced.

The starter unit which had caused us so much trouble did it again. We were trying to start the jet to test the new electric system when the RPM collapsed and the starter gave out unpleseant noise. Damage was not as bad as it sounded. One of the graphite brushes of the DC motor had weared out. We get a new set and replaced it. The next start did something even more spectacular. The DC motor puffed out a cloud of smoke. Something that is expected from the jet but not from the motor. This time one of the the stator coils had burnt it's insulation. So we had to change the whole stator and motor casing. The leaf blower had a small air bleed output in addition to the main blower output that goes to the jet. We had blocked the bleed hole earlier and now we opened it again. A small air tube about 1.5cm in diameter was attached to that hole and the other end put on an opening in the motor casing. Now the starter blows some cooling air through it's electric motor and we hope this time the device would finally become reliable.

When we arrived at Alastaro we were told to immediately unload the bike and get it running. So it took some 10 minutes to unload it from the van and start the engine. Since the engine was cold we used the carbon dioxide start which worked fine without flamesout or smoke. A puff of smoke was genereted when we shut down the engine. We tried to use raw terpentine in the engine. It burned nicely and the jet even gave out a bit more thrust than with diesel fuel. The terpentine contained pine resing and when we shut down the engine the melted resin solidified in the fuel pump axis seal seizing the pump. It seems that when the pump is running the friction heats the seal so that the resing melts but when the pump is stopped it stucks. So we had to take the pump apart and clean it to get it rotating again. The rest of the day we used the diesel fuel and the problems ended there. The pictures show our team members riding the bike during that day.

NEW Turbocharged Saunan Kiuas.

In Finland there is a traditional place for relaxing and washing, called the sauna. It is a room that is heated to 80-120 deg.Celsius and people sit there on wooden benches called Lauteet and throw water on the rocks in the kiuas. The water is instantly vaporized and the sauna is filled with hot steam called Löyly. The heat is generated by a special stove called the kiuas. In the most traditional version of the sauna, called the smoke sauna, it is only a pile of rocks with cavity in the pile. Wood is burned in the cavity and the smoke gets inside the sauna and out from a small hole in the wall. In modern sauna a kiuas is a steel box with a furnace on the bottom and room for rocks on the top. Wood is burned in the furnace and it heats the air in the sauna and the rocks in the kiuas. In cities a version with electric heating instead of the wood burning combustion chamber is used. Usually it takes about one hour and two loads of wood to get the sauna ready.

We decided to boost the process a little. An exhaust flange for a turbojet was welded on the place of the chimney on an old wood burning kiuas. The compressor outlet was connected to a steel pipe welded on the place where the ashtray of the kiuas was before. The hatch to the furnace was replaced with a stainless steel plate that is held in it's place with 8 bolts and car valve springs. A fuel nozzle was added to the side of the furnace and a flange for a spark plug was made from an old moped two-stroke engine. All other holes in the kiuas got steel plates welded on them. The fuel pump was similar than in Eunuch 2 and a 3-phase electric motor driven hydraulic pump was used for the oil.

At first we tried the system without the front hatch and used the same airstarter as with Eunuch 2. A big flame got out from the stove as expected and we put the spring loaded hatch to it's place. The startup is a noisy event. Since there is no flameholder in the furnace the volume is filled with diesel oil vapour and then ignitd. The bangs are extremely loud and the whole thing jumps and shakes. The spring loaded front hatch acts as a overpressure valve and keeps on banging open and back closed. After a while burning fuel is accumuleted on the bottom of the furnace and the interior starts to glow red hot. Now the ignition of the fuel is imminent as it sprays out of the nozzle. The banging and shaking ceases and the turbo starts accelerating. Soon the system is self sustaining and the airstarter can be removed. In a 1.5 minute the whole thing is bright red. The turbo and the inlet flange glow orange-yellow. A small leak of fire was soon noticeable at the spark plug holder, soon the aluminium melted and we shut down the system. A new plug holder was made of steel and the plug itself was lengthened to get it closer to the nozzle. Next we put some rocks on the kiuas, actually there should be pile of them and these few are just for testing. The startup was succesfull and since we used less fuel at the beginning and had better spark plug arrangement the bangs weren't as loud as on the first time. The system got red hot in the 1.5 min. time but the rocks didn't. Obviously the turbo-kiuas should be run several times to red glow and then let to cool down and heat the rocks.

Currently we are making the system more compact and easeir to transport.