| Twin Turbo's
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Original turbo in the background, identical turbo
foreground. This second turbo was acquired for the twin turbo jet project. Like the first, it was sourced cheap through ebay.
This turbo was in good condition like the first except that it had
excessive carbon build-up in the body such that on turning the shaft a
horrible crunching sound could be heard. I resorted to using Redex, a
chemical engine cleaner that removes carbon deposits. I filled the body
with this and left to soak overnight, intermittently heating the body (
cartridge/bearing housing ) of the turbo with
a blow torch to aid the chemical in it's cleaning duties. A few more
applications saw rid of the carbon and a nice clean free shaft! |
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Combustor Cap
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Injection end of the combustion chamber. Shows
propane torch head, spark plug for igniting the propane pilot light
and fuel inlet hose. Lower pictutre shows the torch head connected to a propane/butane
gas canister. A half-size canister ( 500ml ) will be used in practice.
This can be removed once the engine is running. |
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Pilot Light
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As I will be using Diesel for fuel I wanted the most
reliable ignition device. Spark ignition is used by many but is not so
reliable when using liquid fuels. Using a propane pilot light
practically guarantees ignition first time. |
Ignition device
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This is used for igniting the propane pilot light.
It consists of a gas cooker/barbeque piezo spark generator connected
to a length of auto ignition lead. |
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Combustion Chamber
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Combustion chamber stripped of paint. Finishing off
the faces of the flanges. This involves working the mating surfaces on
a some wet and dry on a flat surface. Final jointing will use some
form of high temperature silicone gasket. |
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Oil
Tank
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Oil tank and experimental cooling system. The tank
is based on a small fire extinguisher and extended in the middle
section with a piece of hand rolled steel plate. The oil tank acts as
a buffer between the oil exiting the turbos under gravity and the oil
pump pickup point. It also allows the oil, which will be very hot and
frothy, to settle out before being pumped round again. Failure to
allow the oil bubbles to settle out will result in audible pump
cavitation and loss of efficiency. The amount of oil used depends on
the efficiency of the cooling system and the duration of runs. I took
a guess on an oil capacity of about 2 litres as I wanted to minimise
on weight and bulk and reckoned this would be adequate with good
cooling. Total capacity of the tank is about 1.8 litres and with
the oil in the pipe-work, more than 2 litres.
Cooling using the engines fuel source is common practice in aircraft
and I thought I would employ the idea here. The cooler is aluminium
from a motorcycle which will be immersed in the oil. It will
effectively sit between the fuel tank and fuel pump and means that the
cooler is on the low pressure side of the fuel system, so no chance of
the fuel leaking into the oil. The Diesel fuel
will be drawn through, hopefully providing a good sink for the heat of
the oil. Only testing will tell if it actually works! ;o). |
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Oil Tank Filler Pipe
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Oil tank filler stub and screw cap made from the top
of a motorcycle fork stanchion tube. The small hole in the top of the
cap is for venting of the hot oil vapours. The twin oil inlets are 28mm with
compression couplings. For the purposes of ease of bending, I will use
28mm to 22mm reducing sets with 22mm copper tubing when connecting to the turbo outlets,
with the option of using 28mm pipe if less flow restriction is needed. Still some
tidying up to do on the welding as I had to spot the joints to help
minimise
distortion. |
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Oil/Fuel System
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Finished oil/fuel system showing the model aero engine
( not including the cooling shroud ) and
fuel pump. Throttle control ( red lever on ball valve ) on right hand
side connected to the underside of a manifold through which the fuel
flows. This will control fuel flow back to the tank and conversely
control fuel flow to the nozzle. This will most likely be used only on
initial startup to allow the jet engine to start and idle. Once
idling, the fuel pressure and therefore jet engine speed will be
controlled by throttling the engine. On the exit of the manifold
is a pressure relief valve so that fuel flows only above a set
pressure to help stop nozzle dribble into the combustion chamber at
idle fuel pressures. On the top of the manifold is a plug that will be
replaced with another pressure regulating valve controlling fuel to
the afterburner. |
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Oil/Fuel System 2
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Oil pump ( power steering ) driven by same engine.
The surrounding plumbing to and from the pump has been changed
slightly from the original design to incorporate larger/better routed
piping. The external pressure regulating valve has also been removed
to be replaced by an internal one that was made by modifying the
integral pressure relief valve inside the pump. The pump outlet feeds the oil filter from which the supply splits to
the two turbos. The red levered ball valve controls the amount of oil
bypass to lower the oil pressure for starting. |
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Schematic Diagram
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Oil system schematic showing the purpose and
positions of all the major components |
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Manifold/Divider
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These pictures show the rough layout and initial construction of
the combustion chamber to turbo manifold. The bottom picture is the
1:1 working plan ( well used! ). The single combustor will serve the
two turbos via the manifold. The pipe is 3" I.D, wall thickness
5mm. The turbo turbine inlets are 2" I.D, therefore I need to reduce the pipe diameter to meet. Slots
were cut in order to draw the resulting 'petals' together ( this is
going to be a very
laborious process! ). The manifold is of heavy construction because it
will be used to provide mounting of the two turbos. Making the
manifold is going to be the single hardest job of the project... |
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Manifold/Divider 2
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Further work. Pulling together the 'petals' in order
to meet the required 2" turbine inlet diameter. Originally the
divider was to turn the gases 90 degrees to the inlets of the turbos,
but I have decided to angle the turbos slightly as in the Current
Build pictures on the
main page. This will
allow better gas flow, result in a smaller 'footprint' to the engine,
and have the jet pipes meet more easily and smoothly into a single
larger jetpipe/afterburner. |
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Manifold/Divider 3
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Further work. Having welded the 'petals' together,
taking a small ring segment out of the manifold ( top picture left ) was
the next step. This is to help bring the turbos closer together and
provide more of an angle to them so that the exhaust pipes will meet
better. Still some tidying up to do on the welds, joining the two main
halves and opening up the inlet to mate with inlet flange. |
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Turbine Flanges
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8mm Mild steel with 10mm Allen head stainless bolts.
These flanges will be welded to the outlets of the manifold. |
Manifold Flange
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Made from 6mm mild steel. Ready to be welded to the inlet of
manifold/divider. Internal diameter 4.5", slightly smaller than the
flametube diameter at 5". |
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Manifold/Divider 4
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Two halves of the root of the manifold cut back,
made symmetrical and 'tack' welded
together. |
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Manifold/Divider 5
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These pictures show the positioning of the manifold
flange. The 'petals' will need to be splayed out to meet the inlet
flange which is the next job to be done. |
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Manifold/Divider 6
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Petals splayed out to meet the combustion chamber
flange. The area of the inlet is the equivalent to that of the two
outlets combined. The bottom picture shows all the bits of the manifold with the
turbine cones almost finished having been 'tweaked' with the angle
grinder. Also shown is my home made bending tool used in conjunction
with a propane blowtorch to help with the bending process..! ;o) |
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Manifold/Divider 7
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Almost there! Tough job but the main part is over,
just some fettling to do. The 'webbing', i.e. raised internal joint
where the two halves meet, was the hardest part. |
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More Flanges!
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Flanges, flanges, flanges...! A couple more to be
made, 3mm mild steel, one for welding onto the combustor for mounting
the manifold flange and one that will have a ring welded on as a slip
joint for the flame tube. Shown is work in progress with the thicker
manifold flange sandwiched between the two pieces to be worked as a
guide. |
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Manifold/Divider 8
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The manifold flange is finished and faced off which
is now nice and flat ( top two pics). Next comes the welding of the
individual manifold cones onto the divider. I tacked them in place
with an epoxy glue so that I couldn't nudge them out of place before
properly tack welding them. The epoxy will have to be thoroughly
cleaned off before welding proper. |
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Manifold/Divider 9
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Welding of the cones done! Just some tidying up to
do. Next comes welding of the turbine flanges ( bottom picture ) that
will allow the two turbos to be bolted on. The flanges have had a
locator/sealing ring welded on to mate with the recess on the turbo's
turbine scroll. |
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