Planing for next years speed weekend, (1/2 scale Argus)

[erik]

[racketmotorman]

Hi Erik

Thats a professional finish ...........

Beautiful

Cheers
John

[PyroJoe]

Looking good,
Have you considered how the starting air will be supplied?
Looks like Maddox is using a air tank.

[Viv]

Its definitely starting to get an awesome look about it I was just looking at it and wondering about the sound pressure and how it was going to impact the rider? the exhaust is going to be pretty close to his dangley bits

Viv

[racketmotorman]

Hi Viv

LOL, I think his "dangly bits" will end up being "mushed" by the shock waves , sorta like how they destroy gall stones in hospital , its the "computer" sitting on his shoulders that I'm worried about , it'll be bouncing from one side to the other trying to break its way thru the skull bone .....................man , that thing is gunna do damage to the human body ,..... I use to feel sick after operating my "little" 50 pounder for any length of time

Cheers
John

[Viv]

Hi John

I think we should advise them to step up the ear protection to ear plugs and ear protectors as well I am not sure a cod peace would be out of the question ether!

Viv

[PyroJoe]

Erik,
You and your team did good with the time you had. That is one big engine. I am curious to know if you had your fuel system split into a fueling rate to start the engine, and a fueling rate to throttle up.

From the looks of it, the starting air may have been a little weak. Plenty of time till next year, Will you give it a go for 2012?

[LinusN]

Hi
This is Linus, the 3rd member of Svarthålet Racing. I have deliberately stayed away from this forum, because these kind of forums just gives me even more ideas that keeps me awake at night =)

We have made several test runs with the engine by now, and have not yet managed to get it to run properly.
As best, it barely starts to oscillate, but develops almost no power at all and it seems like most of the fuel is combusted outside the engine instead of in the combustion chamber.
We have experimented with different configurations of fuel nozzles but the result is pretty consistent.
My theory is that not enough air is entering the combustion chamber from the front intake, and I plan to do some experiments with different thickness of the valves.

Here are some clips showing different attempts to get the engine running:
http://www.youtube.com/watch?v=qDXCSFc7K_Y
Everything is in Swedish, but I believe pulsejets sound about the same regardless of langage

Does anyone of the more experienced guys in here get any ideas of what to do?

You can also check out our blog for more information. it's in Swedish, but give Google a try to translate it.
http://translate.google.com/translate?j ... e/&act=url

[Viv]

Hi Linus

My first impression is how "soft" the first ignition pulse sounds, its a puff out of the exhaust pipe not a bang, lets see what other people think of that observation?

? what is happening at the valves when the engine fires? does any backfiring happen at the inlet at all?

? did you test the valve stack for a seal? did you try pressurizing the engine to see what air leaks out of the inlet?

? were is the spark plug located on the engine? same place as a real V1 or some were else?

With the above said it could be not enough air supplied to the atomizers for the fuel and the valves are not sealing enough for the first bang to generate enough energy for the next one.

Lastly did you try some thing simple like a small leaf blower blasting the inlet as well as the valve grid compressed air feed?

Viv

[racketmotorman]

Hi Linus

Did you try it without the inlet diffuser ??

What was your fuel injection rate and pressure ??

Where is your starting air plumbed to ??

Cheers
John

[LinusN]

The starting air was supplied through a 3/4" hose with 3 nozzles at the end, pointing in slightly different angles. The air flow was aimed directly at the center of the valve grid.

There is no backfiring at all, so I believe the valves are closing really tight (maybe too tight?).

Actually there are four spark plugs at different locations. The first one is about 8" from the valve grid, and that seems to be working best of them.

We had some really powerful ignition pulses to. Really powerful.

Have not tried without the diffuser, but I guess we can do that.

[racketmotorman]

Hi Linus

As you know , I'm more of a turbine builder than a PJ builder , but it won't hurt to have some different views of the subject

The drawings I have of the original Argus show the 3 starting air jets were positioned just "above" the top 3 fuel injector , this positioning of the start air jets would force compressed air through the 3 fuel sprays carrying fuel/air mix further into the combustion chamber, and combined with the start air would potentially aid in combustion , currently with your "external" start air supply there isn't the same "dynamics" .

The Argus also had pretty high fuel pressures , so very good atomisation , you'll be need the same fine spray , same as with turbine combustors , the finer the spray the better the combustion, typically ~ 30 - 80 Bar fuel pressure on commercial aircraft turbines.

The Argus also had starting problems in very cold conditions ........LOL, it didn't look very warm where you guys were , ..............they had to use acetylene gas for ignition and warming of the engine .....................I'd suggest using some propane , its "wider" mixture strength tolerance, compared to your current liquid fuel , would enable you to obtain combustion with less than ideal mixture strengths ,..... once the engine warmed up you wouldn't need it as there'd be more sources of heat for ignition .

With the diffuser , I feel its more for high speed conditions , the same conditions that normal jet engines experience which requires them to have inlet diffusers , I can't see why you would need it during static operation , it only adds another potential unknown during this early stage of your engines development .

Hope these thoughts/suggestions help

Cheers
John

[Viv]

Hi Linus

I think John is perfectly correct and has hit the nail on the head, the air jets are on the wrong side of the valve grid and are not atomizing the fuel correctly and pushing it far enough down the combustion chamber, the fact that the nearest spark plug to the valve grid works best would tend to prove this, on a traditional V1 its half way down the engine tube after the convergent section ( I think?).

Leave the valve leaf thickness alone for the moment as that's a lot of work to change and focus on the compressed air feed and fuel nozzles, its more important to get enough fuel air mix filling the engine for a good repeatable bang than it is playing with the valves, a big leaf blower will help to overcome stiff valves if its an issue at this stage, you need to get resonance and brief running first

The diffuser is a small beer issue as the engine is not running and I don't think it will stop it running or start it if removed, it would as John points out affect performance, remember these engines did not produce flight rated thrust until reaching 150 mph at the end of the launch ramp, there are pictures of them mounted on aircraft with out diffusers too.

Viv

[PyroJoe]

---POST NOT REQUIRED---

[racketmotorman]

Hi Linus

I'm curious as to your fuel injection system , I had a lot of troubles with my turboprop PJ when I started using petrol instead of LPG/propane , ended up having to use a 18GPH 80 degree semi solid pattern spray nozzle at ~110psi ( EFI fuel pump ) supplying ~1.1 litre/min , as well as propane to get the engine to "spoolup" to max pulse rate . .

According to my literature the Argus was using ~ 26 litres/min of fuel during flight , ..............what is your planned fuel burn rate ??

I'm not certain of your "scaling" as regards airflow rates compared to the original full sized Argus , but you'd be needing several litres per minute of fuel as a minimum .

With my reed valves ( ex Yamaha motorcycle blocks) , I found the 0.007" thick reeds showed witness marks that they were fully opening to the stops , the 0.010" thick ones didn't have the same witness marks marking me think they weren't fully opening , I even used "plastic" reeds at 0.017" thick but these experienced physical damage because they were used in the "high lift" steel reed blocks, the greater lift to the stops meant more force on the reed tips when they slammed home on the rubber coated seating , fracturing the "plastic" .

Cheers
John