ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 236
|
Post by ripp on Dec 15, 2021 1:09:34 GMT -5
Cheers Ralph
|
|
|
Post by racket on Dec 31, 2021 1:44:42 GMT -5
|
|
|
Post by racket on Dec 31, 2021 22:07:04 GMT -5
A "cold head" with lotsa carbon/soot then an overheated outer wall A saw tooth heat mark at the Secondary holes indicating swirl potentially centrifuging the fuel against the outer wall where it is severely burning the stainless . Swirl impacting the overlap joint in the flametube , there is also a buildup of carbon in the "corner"
|
|
ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 236
|
Post by ripp on Jan 1, 2022 5:38:27 GMT -5
A "cold head" with lotsa carbon/soot then an overheated outer wall A saw tooth heat mark at the Secondary holes indicating swirl potentially centrifuging the fuel against the outer wall where it is severely burning the stainless . Swirl impacting the overlap joint in the flametube , there is also a buildup of carbon in the "corner" Hi John, You said: I'm seriously considering going back to vapouriser and "aircaps" like I had in the 12/118 as I'm not burning fuel in the first half of the flametube :-( I think the CC needs an air curtain / air waterfall in the headboard to keep the fuel away from the walls and to better atomize it. it may be worth a try. Allison 250 Combustion Liner:https://www.ebay.com/itm/334043668244?epid=19041369336&hash=item4dc68ddf14:g:qVAAAOSwm~Ngy2bE Cheers Ralph
|
|
|
Post by racket on Jan 1, 2022 16:16:17 GMT -5
Hi Ralph
The endwall is full of holes, ~200 of them , which should be mixing air with fuel , but unless the droplet size is small enough, the time taken to vapourise them means the air has carried them too far down the flametube before they combust, and due to the swirl within the flametube I feel the fuel is being thrown to the outer wall , generally our inner wall is the hottest running wall , but on this engine its the outer wall , so somethings wrong .
Due to the "design" of the fuel fan spray , some fuel is going to contact the walls , unlike a single can flametube with a single spray nozzle which can be "easily" designed to minimise this , currently my front wall and Primary Zone side wall are running cold enough for the fuel to build up carbon/soot , I need to get combustion going quicker .
I'll see what the next test run produces , if its still not right right I'll scrap this combustor and make a new design, it'll be quicker than persevering with this setup , I need an easily repeatable setut , this one is getting too complex and "messy" , I need simplicity .
Cheers John
|
|
|
Post by racket on Jan 3, 2022 0:08:10 GMT -5
Hi Guys New upgraded and simplified fuel pumps/valves I've been doing some flow vs pressure testing but I don't seem to be getting the results I hoped for , maybe I need to upgrade the wiring Cheers John
|
|
|
Post by racket on Jan 5, 2022 0:46:40 GMT -5
Hi Guys
LOL........The wiring certainly needed an upgrade , when it was originally put together the load was <10 Amps , now its closer to 25-30 amps , so thicker wires and shorter runs , BUT , the performance is still not that great for 2 pumps .
With the valve to the engine closed and the dump valve operated to produce backpressure on the pumps , I was able to get a flow from the dump at 20 psi of >6,000 ml/min , 40 psi 5400 ml/min , 60 psi 4800ml/min , 80 psi 3800ml/min and 100 psi 3,000 ml/min .
With a backpressure of 60 psi the pumps had 11.6 Volts going to them from the relay only a foot away from the pumps, but only producing a flow of 288 lph , a single genuine 044 is suppose to flow 200lph at 5Bar (72.5 psi) , I guess these chinese knockoffs are a tad underpowered :-(
With the dump closed and all the fuel going into the engine I measured a flow of 4300ml/min - 258 lph through the injectors at 76 psi
Hopefully they'll be good enough for the next test run , otherwise they'll be OK for the afterburner at more modest pressures .
Cheers John
|
|
|
Post by enginewhisperer on Jan 5, 2022 14:54:22 GMT -5
those manifolds with the banjo style fittings into the pumps might be restricting flow a bit too.
Most fuel pump ratings are at 13.8 or 14v too, so running straight from a battery will always be a bit limited.
|
|
|
Post by racket on Jan 5, 2022 16:44:15 GMT -5
Hi Andrew
Yep , theres some restrictions , but that would show up more at low pressures when flows are high , at high pressures with only half the flow any restriction would be minimised , the voltage is certainly going to change things , but its only a couple of volts , one would have thought the motors would simply have pulled max amps to compensate , I'm currently running a 25 Amp fuse for the pair of them and its surviving OK , so I might experiment with lower amp fuses to see just how many amps are being consumed .
More fiddling required :-)
Cheers John
|
|
|
Post by enginewhisperer on Jan 5, 2022 22:52:53 GMT -5
my dual genuine 044 pumps in the race car pull around 12.5 amps each at ~60psi and 13-14v
With most motors the rpm is limited by the voltage, so they'll pull more current as you increase pressure, but the flow rate will drop. Depending on the internal leakage in the pump stage, they might need a lot of rpm just to maintain pressure, so the effect of low voltage on flow rate at full pressure might be pretty severe.
|
|
|
Post by racket on Jan 6, 2022 1:46:58 GMT -5
Hi Andrew
Thanks for the details , food for thought .................have you ever done any flow vs pressure testing ??
Cheers John
|
|
|
Post by enginewhisperer on Jan 9, 2022 15:10:20 GMT -5
I just based my setup on the published specs, and two 044s give a decent amount of safety margin. I haven't seen the pressure drop under full load which is good!
The plan is to change the dual 044 setup out for a single Ti / Walbro "535" (F90000295) pump to simplify things.
|
|
|
Post by racket on Jan 9, 2022 15:44:15 GMT -5
Hi Andrew
Yep , a nice pump , I did have a look at them , but an intank unit , which meant I couldn't go with it :-(
The graphs for the Walbro are enlightening .
Cheers John
|
|
|
Post by wannabebuilderuk on Jan 9, 2022 17:36:56 GMT -5
Hi Andrew Yep , a nice pump , I did have a look at them , but an intank unit , which meant I couldn't go with it :-( The graphs for the Walbro are enlightening . Cheers John That's not the attitude john! I'm sure you could rig up some box to sit it in which is fed from your fuel tank haha
|
|
|
Post by enginewhisperer on Jan 10, 2022 1:53:48 GMT -5
yeah it's not overly convenient! I plan to do a "surge tank inside the main tank" setup to run the Walbro pump, and will feed the surge tank from an external pump with the pickup in a "sump" at the bottom of the main tank.
|
|