BFTO
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Post by BFTO on May 17, 2018 0:44:36 GMT -5
Nah havent measured the fuel pressure, only the flow at around 1,5L/min from the Bosch 044. will do that and see what we get before installing the flame holder.
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Post by racket on May 17, 2018 4:17:37 GMT -5
1.5 lpm is probably a tad too much fuel "theoretically", but if combustion efficiency in the relatively short A/B is a bit poor , then your 1.5 lpm mightn't be far off whats required .
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BFTO
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Post by BFTO on May 17, 2018 6:52:40 GMT -5
1.5 lpm is probably a tad too much fuel "theoretically", but if combustion efficiency in the relatively short A/B is a bit poor , then your 1.5 lpm mightn't be far off whats required . 1,5lpm was at ambient pressure, so with a little bit of pressure in the EBK i thought that would be OK. Will elaborate more with the fuel next time. A little video 0,5bar
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CH3NO2
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Post by CH3NO2 on May 17, 2018 8:35:42 GMT -5
Good idea to have a fail safe leash.
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BFTO
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Post by BFTO on May 17, 2018 8:42:36 GMT -5
Good idea to have a fail safe leash. Haha, yes after this mishap we installed it.
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CH3NO2
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Post by CH3NO2 on May 17, 2018 10:06:25 GMT -5
Wow. Its a good thing you caught it so quickly.
The failure was exactly as Anders predicted with PWM's in general. I think he mentioned that the PWM should have its own power supply isolated from all other devices that can induce noise on the power supply.
I'll be sure to get a similar leash and carefully research a quality PWM.
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BFTO
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Post by BFTO on May 17, 2018 12:25:12 GMT -5
Wow. Its a good thing you caught it so quickly. The failure was exactly as Anders predicted with PWM's in general. I think he mentioned that the PWM should have its own power supply isolated from all other devices that can induce noise on the power supply. I'll be sure to get a similar leash and carefully research a quality PWM. We removed both PWM and installed needle valves instead, full control now and the fail safe lash is probably overkill now but feels good Video from 0,5-1,5bar and then down to 0,5bar to try and light the AB.
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Post by Johansson on May 17, 2018 13:02:18 GMT -5
A dead simple way of lighting the afterburner is to run the engine at idle or just above, then start the afterburner pump and grab a handful of throttle (not doable with your needle valve, you need something quicker) to send a tongue of fire through the turbine that lights the AB fuel.
We had much trouble with spark igniting the jetkick afterburner until we figured this out, no need for a separate hot streak system and if the manouver is done at the right rpm the engine will quickly pick up RPM´s and settle down the EGT to normal levels so no damage done to the turbine.
Cheers! /Anders
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BFTO
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Post by BFTO on May 17, 2018 13:12:31 GMT -5
A dead simple way of lighting the afterburner is to run the engine at idle or just above, then start the afterburner pump and grab a handful of throttle (not doable with your needle valve, you need something quicker) to send a tongue of fire through the turbine that lights the AB fuel. We had much trouble with spark igniting the jetkick afterburner until we figured this out, no need for a separate hot streak system and if the manouver is done at the right rpm the engine will quickly pick up RPM´s and settle down the EGT to normal levels so no damage done to the turbine. Cheers! /Anders I think that is doable with the needle valve, will try that next time. I need maybe 90deg of motion to raise the P2 from 0,5-1bar, so a fast flick with the wrist will maybe do it. From 0-0,5bar is like 10 turns
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CH3NO2
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Post by CH3NO2 on May 23, 2018 12:25:59 GMT -5
Hi BFTO,
When your PWM failed to wide open throttle, do you have an idea of what the cause may have been?
Tony
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BFTO
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Post by BFTO on May 23, 2018 12:58:52 GMT -5
Hi BFTO, When your PWM failed to wide open throttle, do you have an idea of what the cause may have been? Tony The pump ground to the chassi through the fuel tank mount and the PWM dont like that and run at 100% (our 044-pumps is mounted inside the fuel tank). And when we isolated the tank from the chassi with plastic/rubber the 100% problem was gone but when we installed the AB pump it took a while to discover that we had some issues still. When we switched on the fuel pump to the engine via PWM pontensiometer and started to regulate the flow, the AB-fuel pump was switch on even when the switch/PWM was OFF on a low setting so we didnt hear that for some time but it created a bit of a smokeshow. I think the steel braided hoses was the problem and we throw the PWMs in the bin, didnt want something so sensitive in this build. The needlevalve works so much better and is much more accurate. When we only had one pump and isolated the tank the PWM worked fine but was to sensitive for my taste.
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CH3NO2
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Post by CH3NO2 on May 23, 2018 15:45:18 GMT -5
That sounds alot like a ground loop issue. Are you familiar with ground loops and how to deal with them? They are often solved by running heavy gauge ground wires from every accessory to one common ground point.
Another possibility is the two PWM's are introducing so much noise into the power supply that they are interfering with eachother. If you have an oscilloscope you may be able to see HF AC riding on the DC power lines. It may be possible to put LC noise filters on each of the PWM's to filter out the back emf trash.
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BFTO
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Post by BFTO on Jun 17, 2018 14:34:58 GMT -5
That sounds alot like a ground loop issue. Are you familiar with ground loops and how to deal with them? They are often solved by running heavy gauge ground wires from every accessory to one common ground point. Another possibility is the two PWM's are introducing so much noise into the power supply that they are interfering with eachother. If you have an oscilloscope you may be able to see HF AC riding on the DC power lines. It may be possible to put LC noise filters on each of the PWM's to filter out the back emf trash. Not familar with ground loops, but we dont need PWMs anymore. 18L of diesel was burnt today on 3 runs Still have some problem to light the AB when its cold, after the AB is glowing its not a problem to light it. We need to go down to around 0,25bar P2 to make it light and then introduce more fuel as the power setting is raised. Tested the hot streak way but didnt make flames to light the AB, probably the valve isnt fast enough. Got to 1bar P2 with the AB but the EGT was at around 650deg, didnt want to go any higher. The glowing red AB probably transfer some heat but I think the nozzle is to tight to, will open the nozzle a bit to lower the temps next time. But she screams quite good now at 1bar but needs around 1,5bar where all the thrust begins. 1,5Bar without AB the 100kg stand on 20mm wheels is moving in gravel. To next test:
- Open the nozzle a few mm.
- Install one more sparkplug to the AB, got two more outputs on the ignition coil so a easy fix.
- Install a one way valve on the AB fuel line.
- Weld in 253MA flatbars in AB to make a better flameholder.
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BFTO
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Post by BFTO on Aug 19, 2018 12:16:13 GMT -5
Did all the things above and the engine is working flawlessly with the AB now. The nozzle is 75mm and is running ~610deg at 1,5bar with AB screaming (can go to around 1,8-2,0 before the temps starting to get to hot) but ran out off fuel as always We start to feel finished with this extended project, will probably be a exhibition item. Got a invite this summer to run it on a local air show but the extreme dry weather made it a no go
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