Got a "Napier Gazelle" but need help

[racket]

Hi Ben

Congratulations :-)

Cheers
John

[gidge348]

Well done Ben, can't wait to see the video.


Ian...

[TwoGears]

Hello guys,

I'm having trouble to get my turbine run again.

Two seconds after the starter reached its max. rpm and I switched on the ignitors
I open the HP-lever (like when the engine worked). But then the ignitors suddenly
stop to work and don't ignite the fuel. Therefore the turbine is drowning.

I cleaned everything now but no change.

What we changed from the last successful start:
Fuel:
We now use a defined mixture of Diesel, Petrol and oil (84,5% Diesel / 15% Petrol / 0,5% Oil)
When we brought the engine to run properly we had the same substances but likely
another mixture because.
I tested it for burning with a spray bottle and a lighter and it immediately inflamed.
Why I use this as fuel? --> Because I didn't find any kerosene supply so far -_-

Temperature:
When the engine worked the ambient temperature was about 12°C now it's around 4-5°C
Could this also be a hard fact for drowning instead of working?


Nothing else changed since the last time I brought you the news
that the engine finally is working.
I also removed the ignitors and cleaned them yesterday, still the same situation.

I run out of ideas what's the problem here.

And YouTube seems to not like the videos my friend made with his iPhone
I'm keeping up converting into different formats and try them.

After the bad thing the good is following. It seems the oil is flowing properly now.
The level sinks when I start, then there is a little foaming and after shut-off the
level is rising but not as much as before. In average it always keeps the same level.

[cursorkeys]

First, huge congrats on getting it to idle. It took me months to get my GTD-350 to run so you've beaten me

Your fuel is a bit of a brew but it should still burn like you said. Are you using a LP fuel pump? On my GTD-350 the thing that stymied me was that the torch ignitors do not get fed by the engines fuel pump so without some supply pressure you get seriously erratic ignitor performance.

The temperature shouldn't be an issue in that range for JET-A1, diesel, parafin etc...

Can you hear your ignitors cracking? Do you know if they are torch ignitors or not (is there a fuel supply to the ignitor plug assembly)?


I don't think it's the issue here but I'd still try to get hold of some proper fuel. I know 'kerosene' doesn't mean the same thing in many countries but the proper fuel would be called 'JET-A1' or 'AVTUR' almost universally and it has the proper corrosion inhibitors, lubricity etc... Your local airport should sell you some without any hassle. If you have problems then you should be able to order a 205 litre barrel from any aviation services company.

[TwoGears]

Thanks for the compliment but I think it's a little early since I just managed
to get the engine there once. Nobody knows how long it'll take me to get it to
idle stage the next time but there will be a beer and a cheers involved then

I've sent some inquiries to a few fuel suppliers and airports around. Before
I buy a barrel of aviation fuel I'll first wait for their answers.

My ignitors are definitely spark-ignitors. They almost look like the ones from
the Williams WR27-1 engine of your? page: www.cursorkeys.com/index.php?page=ignitor-replacement
I have no pump between the fuel tank and the fuel filter. But the tank is placed
a little above the turbine for bubble-free supply.
Before the first idle-run came up and after I cleaned them, the ignitors always
worked properly on every start attempt.
When I replaced the fuel they started to blow-out when I opened the HP-lever
and the fuel was injected. Therefore the engine drowned. I can't really think
of any reason why this happens suddenly?
I managed to drown the engine a countless number of times before the first idle-run
but there were never a problem with the ignitors.

However, I run the contactors for the starter and the ignition system from a
20 Amp. power supply. I just had car batteries back then and those were way to
weak for powering everything. It worked properly so far but maybe there is something
wrong with the power supply now. At the next starting attempt I'll connect everything
to the truck batteries I've got now. They should do the job.
If the ignitors still get blown-out and stop to crack, I don't know any more reasons
as the fuel.

I'm also looking for an ignitor plug replacement since mine doesn't really look
that healthy anymore

Thanks for the help so far.

[gidge348]

Nov 2, 2013 17:42:02 GMT -5 TwoGears said:

My ignitors are definitely spark-ignitors. They almost look like the ones from
the Williams WR27-1 engine of your? page: www.cursorkeys.com/index.php?page=ignitor-replacement
.

Hi Ben,
The torch igniters and spark igniters look the same the only difference is that "Torch Igniters" also have a fuel line running to them like this:




Does yours have a fuel line as well or just the power cable?

It is strange that the igniter cuts out when the fuel is added, are you using the factory wiring to the igniter box? Are there any strange relays or that attached to the igniter box? Even if the Igniter "blow out" you should still hear them firing?

[TwoGears]

I don't have any fuel lines leading to the ignitors, like at the picture, just the power cable.
I have two ignitors one at the left and one at the right side of the turbine.

Before I cleaned them you indeed could hear the firing eve if they were to dirty for
producing a proper spark. This was the fact until the first successful start. Afterwards
they stopped to fire multiple times when I opened the HP-lever. Sometimes they came again
but not for long, just 2-3 sparks.
It happened once that my buddy accidently left the ignition-system on and suddenly the igniters
started to fire again. The igniter box is directly connected to that 20-Amp. power supply.
I think this could be a problem if the power supply has gotten some damage and maybe
hasn't got enough power to even fire the igniters when fuel is on them.

As I said, I'll connect everything to the batteries next time and we'll see.

[TwoGears]

Okay then...
After some tests with the ignition-system today I found out some interesting facts.
The exciter boxes both seem to work fine. The problem comes with the igniters itself.
I found out that one of the igniters has double the resistance between the inner electrode
and the outer case than the other has. Exactly this igniter doesn't work properly while
the other one does on both exciters.

Now the one million dollar question... WHY has it double the resistance?

working igniter: 55 kOhms
non-working igniter: 116 kOhms

Along with this I also think the igniters are in a very bad condition
so are the contact caps on both the igniter and the cable coming from
the exciter.
I think replacing all these parts will also solve the problem with
drowning. But where to get igniters and cables with electrodes?

Here are some pictures from the removed igniters:
(click the thumbnails for original size images)

[gidge348]

Just looking at the pics I would say the problem is the connection between the HT lead and the igniter plug, they look pretty ratty....

Can you clean the plug, cable & connectors up some how, maybe in a lathe or grinder etc. looks to me like the leads could have been loose at one time?

Once everything is clean check the resistance again you could have a fried plug

[ernie wrenn]

X2 loose connection causing a carbon build up ... Clean them. Them female end will be the hard ones. small wire brush or Dremil Tool with a sanding mandrel.

[ernie wrenn]

X2 loose connection causing a carbon build up ... Clean them. Them female end will be the hard ones. small wire brush or Dremil Tool with a sanding mandrel.

[TwoGears]

Wow, that important that only two posts will do the job. I'll try my best then
But what do you mean with X2?

The isolation resistance is only measured between the electrode in the middle
and the outer casing. As you can see at the last pictures (inner and outer metal)

[gidge348]

Just checked the resistance on a "new" Nimbus igniter plug across the inner and outer casing and got a reading of 36.5 kOhms. So it looks like 116 is way over.

I still think it is worth cleaning the connectors and re-testing as they are obviously not right.

(X2 just means agree with previous post)


With finding parts, you may want to try www.jetartaviation.co.uk/ they seem to have a large collection of old british aero space stuff. If not maybe contact the tractor pull guys

[TwoGears]

Was it 36.5 Ohms or kOhms?
If it were just Ohms, i could throw mine into the trash. Still i wonder
how this is even possible. Silicon as an insulator shouldn't really react
with anything even not with kerosene or diesel as fuel.

However, I also contacted the tractor pulling guys. Maybe they'll writ back this time.

[gidge348]

Sorry, My bad kOhms not Ohms have changed post.

I am not sure about the insulator either, but you have nothing to loose cleaning them?