ashpowers
Veteran Member
Joined: February 2011
Posts: 207
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Post by ashpowers on Oct 18, 2014 16:30:04 GMT -5
As for leakage of oil past the turbine seal, knowing that the lubrication system is operating at the kind of pressures it is, I do have concerns about having too much volume flow to the rear bearing and this is creating a pressure differential at the rear seal that is allowing oil to pass through the seal. Looking back at images of the initial build of the bearing housing you can see the single entry port where the oil enters the rear bearing and the bore continues at what looks like the same or similar diameter back towards the face where it meets the NGV baseplate. All of that oil pressure being used without an oil "channel" like what is found in OEM bearing housings means that the oil is distributing outwards from that port in all directions. The seal on the shaft is probably no more than maybe 0.5" to 0.75" from that port and with such high oil pressure I can easily see how it can be forced past the seal, which as was already noted, it NOT a perfect seal.
Adding to that, the observation of the turbine wheel itself with large amounts of coked oil deposits.
Another thing I would suggest to do is to machine a steel sleeve for the bearing housing at least for the turbine shaft seal to ride on. Make its installation a press fit. The hardness of the steel will prevent the shaft seal from galling the surface as compared to aluminum - especially in the hot end of the engine where the aluminum is going to lose some of its hardness. The rotor shaft does move axially a small degree during operation - clearances in the thrust bearing change and thermal expansion of the shaft requires that the turbine shaft seal be able to freely move in an axial direction with it in order for it to properly locate itself and seal properly. Aluminum isk likely to gall over time.
If it were me, I would machine a complete steel sleeve for the bearing housing that runs full length, machine it a few thou small and then bring it to proper diameter through sanding with progressively finer paper until you have the correct dimensions and a polished surface. Steel will hold its surface properties much better than aluminum will and it will wear a lot less as well so the engine over time will maintain better bearing clearances as you put the miles on.
Lastly, I would machine oil delivery slots into the steel sleve over a 180-degree sweep - centered at the delivery port, located at the center of both bushings and with the width of the holes in the bushings... Just like how it is typically done in journal bearing turbchargers I work with all the time in my business. This will increase the oil delivery into the bearings, specifically to the interface between the rotor shaft and i.d. of the bushings through the radial holes in the bushings. It also will mitigate rotational dynamic instabilities since there is no longer intermittent delivery into the radial holes as they pass by the feed port, provide a larger surface area to deliver the oil to the bearings, more homogenously distribute the flow such that the local pressure of the oil at the point it interacts with the turbine shaft seal is lesser, and I would run the same Garrett recommended oil pressure as the turbocharger these bits came out of. You might even want to consider refining your lubrication system such that it is on-demand - dynamic pressure based on your P2 pressure. The oil pressure in a piston engine is, for the most part, dependent on the engine's RPM and turbo response is also related to piston engine RPM. You dont need as much lube to the bearings at lower loads. An adjustable oil pressure regulator based on P2 pressure would accomplish this. The thrust bearing only needs to produce a floating support equal to the axial thrust in the group. That support is not generated really so much by the oil pressure itself - the pressure just gets oil to the bearing and from there the dynamics of the oil take over and the planing of the bearing faces on the oil film are what provide the support. This is the same thing that occurs in the radial bearings as well. The higher oil pressure is just pushing more quantity which does help by way of keeping things cooler but increases in oil pressure have diminishing returns and your current configuration with just a single entry point can actually suffer from elevated oil pressure as it is creating a force bias that is placing more load on the bearing at the opposing side..... and again, as the radial holes in the bushing pass by the entry port, the oil pressure force on the bearing suddenly drops as one of the radial holes pass by the port, increases the oil pressure force on the shaft, and so on.. all kinds of varying forces on the different rotating parts at different times can't be good for stability and longevity.
I dont know if what I just went on and on about here (LOL) has anything to do with the high EGTs you are seeing or not. The only reason I bring it up is just an observation of how you built your rotorbearing system and the differences between yours and what I've seen in OEM turbos. It will be a little bit of work to make some of the changes I suggested but I can only see how it will bring its own benefits without any drawbacks.
I can also say that all of these suggestions also are very likely to address the problem with the oil that is getting past the seal.
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Post by ernie wrenn on Oct 18, 2014 16:56:49 GMT -5
Damn! That is a lot said!
I agree with limiting the oil flow. The J-34 and your Viper has a "lost" oil supply to the rear bearing but so little oil is sent to the area, a small loss of oil is expected. This reduces the chance of a lip seal being lifted by the pressure.
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Post by racket on Oct 18, 2014 19:08:55 GMT -5
Hi Ash
Yep, I agree with you that we need reliability with our evaps , having them not too hot and not too cold , the commercial micro engines have pretty thin walled evaps , down in the 0.3mm WT range whilst still being required to cope with the same temp extremes .
I felt Anders may benefit from thinner WT due to those witness marks on the inside of the flametubes front wall , it appears as though there has been "liquid" impact which could have contributed to poor fuel burn at low power settings with high temps downstream .
Having a bellmouth inlet on the evap would mean it flowed its designed amount of air , ~10-12% of total flametube flow area , enough to cool the evap along with the fuel vapourisation and provide a rich gasious mixture exiting them that only needs a bit more air to get combustion going .
We don't want too much air going down the evap as it'd probably overcool it with possible fuel evaporation problems , but we don't want it so hot that the tubing shows signs of heat stress such as Anders tubes appeared to have , its a juggling act that will probably change from engine to engine depending on the air/gas flow patterns within the flametube as well as the radiation levels from different fuels etc etc etc ..... a trial and error approach required maybe .
Cheers John
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Post by racket on Oct 18, 2014 19:11:25 GMT -5
Hi Anders
Nice mountain views
Looks a bit cold with all that snow , .................LOL, you need to grow a bit more hair on your head ;-)
Cheers John
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Post by racket on Oct 18, 2014 19:34:39 GMT -5
Hi Ash/Ernie
Because of the very limited space in our shaft tunnels theres going to be some problems keeping oil out of the turbine wheel area , even a good quality turbo will pass some oil if the pump is supplying pressure and the turbo isn't on an IC engine but has been made into a GT and the rotor isn't turning .
Also we need lotsa oil at the turb end for cooling as we can't run heat shields like a turbo does , theres simply not enough room , ...........theres some tradeoffs in play , the lesser of evils is some leakage into the turb space , which for a machine built for limited run times, isn't a big problem , its preferable to having overheating at the turb bearing and seal .
Cheers John
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Post by racket on Oct 18, 2014 20:21:15 GMT -5
Hi Anders
I did some "numbers" for the "tighter" turb wheel and they work out OK , but the clipped wheel you're currently running would have a bit more "potential" if at some stage you want to really push the temperatures and/or fit "augmentation" , theres less chance of the exducer causing problems ..............theres considerably more exhaust swirl with the unclipped wheel if we have to use high gas speeds through the exducer to exit the required flow at the higher temps .
Stick with your current setup , your "top end" temperatures aren't excessively hot, after all , yours is a race bike wanting max power , cool temperatures only give mediocre power :-)
Cheers John
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Post by Johansson on Oct 19, 2014 11:07:24 GMT -5
Hi Anders, Lovely to see all the internal bits looking so good. I think that your test with a straight pipe will fix many of your current issues. The one big change since your earlier straight nozzle test with lower temps is the 90 degree exhaust pipe. This is what I was getting at back when you had issues with the power turbine section on. Flows don't like to turn 90 degrees and we usually pay for that with high pressure losses. I still think that the exhaust out of your power turbine section may be an issue. It would be relatively simple to check with the addition of a few static pressure taps to see if there was exhaust back pressure at the exit plane of the turbine. The hot spot could easily be the local stagnation pressure (and thus local heat transfer coefficient) being higher due to the presence of the downstream bend. I tried to find anything on a swirling flow in a 90 degree bend with no luck, but I did find a plot of cross-sectional stagnation pressures in a bent circular pipe and it does show that early on in the turn, the flow sets up strong local regions of stagnation pressure that could easily match your setup if the flow swirl cause the high pressure region to rotate in the passage. Unfortunately, I wasn't able to find it free online, but if anyone can get this book from the library, www.amazon.com/Internal-Flow-Applications-Cambridge-Technology/dp/0521036720it is shown on page 469. The next item that I feel needs to be discussed is the ability of immersion thermocouples to resolve the temperatures in higher speed flows. As in anything we do with these engines, there is a lot going on, even with the simple thermocouple. You can calibrate a TC at static conditions, but the flow error is not something that people will be to calibrate for you...we are going to have to work this out. We need to take into account radiation effects if we use unshielded TCs. I have a nice book from the MIT press, "Aerodynamic Measurements - Robert C. Dean Jr" that I am trying to go through now to build a spreadsheet to help out with this...more to come. Chris Hi Chris, Wow, lots of food for thought in your post! Hope you don´t mind that I shortened the quoted post down a bit. A static pressure reading after the power turbine would be useful, I´ll make sure to add one once the bike is up and running. I did have rather high TOT´s at idle even during the bench tests with the short jet nozzle fitted, so I don´t think that the bend is the only cause for the high temp readings. It might very well be one cause though so it will be interesting to run the engine with an unbent jet nozzle and see how it behaves. The radiation shielded thermocouple was a clever idea, but since "everyone" are using unshielded ones I get the feeling that I should be able to too. As you point out the problem will be to figure out just how much of the temp that is radiating heat from the turbine wheel. Anders, I also was thinking about the oil leakage on your turbine wheel. I have seen comments in the past, on several posts, that make it seem like the piston ring "seals" the oil, which in fact it does not. The piston ring is primarily there to minimize the leakage of hot gas from the turbine side, it is a dynamic seal and should not have to block oil in a properly running system. In a properly operating system, the static pressure in the bearing housing is lower than the static pressures on the back side of the turbine or compressor wheels. So, the question comes up....what caused the oil in your bearing housing to escape into the turbine? My guesses are: 1. The oil drain is slightly insufficient, allowing the oil froth to back up till the oil level was just above the piston ring at start up or low speed conditions. At higher pressures, I have a hard time thinking that the gas leakage through the piston ring wouldn't keep this at bay. 2. Ash might be onto something...if you are somehow building pressure in the oil tank, this would inhibit the leakage across the piston ring and allow such oil leakage. Are you sure your vent is sufficiently sized? To me the fracture of the weld joint looks more like damage due to pressurization rather than thermal expansion...since there is more deformation in the center of the plate...bowed out. Even small amounts of pressurization can produce large seperation forces when acting over a large enough area. Can't wait to see you ripping down the road again! Chris I do think that you and Ash have a point about the oil tank, I use an AN4 hose for tank venting which isn´t exactly flowing tons of air. In one of the test videos the engine suddenly started to smoke after a high P2 run, what if the piston ring was leaking air into the oil passages that choked the oil tank vent? With a pressurized oil tank the scavenge pumps weren´t capable of extracting the oil from the bearings making the oil leak out past the seal, and when the pressure in the oil tank was high enough it simply blew a weld. The signs on the floor sort of confirms this, there was a spray of oil coming from the cracked weld. As you guys pointed out the tank looks like it has been subjected to pressure, and the loud bang that actually rocked the bike shouldn´t have been as violent if the weld simply cracked from thermal expansion. This won´t be an issue later since I will fit a large diameter hose from the oil tank to the gearbox for oil draining, a large vent will be placed on the gearbox so there won´t be any risk of tank pressurization after that modification. As for leakage of oil past the turbine seal, knowing that the lubrication system is operating at the kind of pressures it is, I do have concerns about having too much volume flow to the rear bearing and this is creating a pressure differential at the rear seal that is allowing oil to pass through the seal. Looking back at images of the initial build of the bearing housing you can see the single entry port where the oil enters the rear bearing and the bore continues at what looks like the same or similar diameter back towards the face where it meets the NGV baseplate. All of that oil pressure being used without an oil "channel" like what is found in OEM bearing housings means that the oil is distributing outwards from that port in all directions. The seal on the shaft is probably no more than maybe 0.5" to 0.75" from that port and with such high oil pressure I can easily see how it can be forced past the seal, which as was already noted, it NOT a perfect seal. Adding to that, the observation of the turbine wheel itself with large amounts of coked oil deposits. Another thing I would suggest to do is to machine a steel sleeve for the bearing housing at least for the turbine shaft seal to ride on. Make its installation a press fit. The hardness of the steel will prevent the shaft seal from galling the surface as compared to aluminum - especially in the hot end of the engine where the aluminum is going to lose some of its hardness. The rotor shaft does move axially a small degree during operation - clearances in the thrust bearing change and thermal expansion of the shaft requires that the turbine shaft seal be able to freely move in an axial direction with it in order for it to properly locate itself and seal properly. Aluminum isk likely to gall over time. If it were me, I would machine a complete steel sleeve for the bearing housing that runs full length, machine it a few thou small and then bring it to proper diameter through sanding with progressively finer paper until you have the correct dimensions and a polished surface. Steel will hold its surface properties much better than aluminum will and it will wear a lot less as well so the engine over time will maintain better bearing clearances as you put the miles on. Lastly, I would machine oil delivery slots into the steel sleve over a 180-degree sweep - centered at the delivery port, located at the center of both bushings and with the width of the holes in the bushings... Just like how it is typically done in journal bearing turbchargers I work with all the time in my business. This will increase the oil delivery into the bearings, specifically to the interface between the rotor shaft and i.d. of the bushings through the radial holes in the bushings. It also will mitigate rotational dynamic instabilities since there is no longer intermittent delivery into the radial holes as they pass by the feed port, provide a larger surface area to deliver the oil to the bearings, more homogenously distribute the flow such that the local pressure of the oil at the point it interacts with the turbine shaft seal is lesser, and I would run the same Garrett recommended oil pressure as the turbocharger these bits came out of. You might even want to consider refining your lubrication system such that it is on-demand - dynamic pressure based on your P2 pressure. The oil pressure in a piston engine is, for the most part, dependent on the engine's RPM and turbo response is also related to piston engine RPM. You dont need as much lube to the bearings at lower loads. An adjustable oil pressure regulator based on P2 pressure would accomplish this. The thrust bearing only needs to produce a floating support equal to the axial thrust in the group. That support is not generated really so much by the oil pressure itself - the pressure just gets oil to the bearing and from there the dynamics of the oil take over and the planing of the bearing faces on the oil film are what provide the support. This is the same thing that occurs in the radial bearings as well. The higher oil pressure is just pushing more quantity which does help by way of keeping things cooler but increases in oil pressure have diminishing returns and your current configuration with just a single entry point can actually suffer from elevated oil pressure as it is creating a force bias that is placing more load on the bearing at the opposing side..... and again, as the radial holes in the bushing pass by the entry port, the oil pressure force on the bearing suddenly drops as one of the radial holes pass by the port, increases the oil pressure force on the shaft, and so on.. all kinds of varying forces on the different rotating parts at different times can't be good for stability and longevity. I dont know if what I just went on and on about here (LOL) has anything to do with the high EGTs you are seeing or not. The only reason I bring it up is just an observation of how you built your rotorbearing system and the differences between yours and what I've seen in OEM turbos. It will be a little bit of work to make some of the changes I suggested but I can only see how it will bring its own benefits without any drawbacks. I can also say that all of these suggestions also are very likely to address the problem with the oil that is getting past the seal. Hi Ash, Between the rear bearing and the turbine seal there is a drain channel where the scavenge pumps suck away the oil coming out that way, the piston ring seal seats in the steel NGV housing so no aluminum in contact with it. The engine has not been smoking at all earlier so this is something that has happened lately, but I think I could decrease the cold oil pressure a bit to make life easier for the scavenge system. Your ideas about improving the bearing arrangement sound good to me but since the bearings work fine with no signs of wear I will leave them as they are for now. Getting the tank welded up and better vented will probably solve the leaking turbine seal, I will measure the roundness of the seal bore just to be sure it is ok. Hi Ash Yep, I agree with you that we need reliability with our evaps , having them not too hot and not too cold , the commercial micro engines have pretty thin walled evaps , down in the 0.3mm WT range whilst still being required to cope with the same temp extremes . I felt Anders may benefit from thinner WT due to those witness marks on the inside of the flametubes front wall , it appears as though there has been "liquid" impact which could have contributed to poor fuel burn at low power settings with high temps downstream . Having a bellmouth inlet on the evap would mean it flowed its designed amount of air , ~10-12% of total flametube flow area , enough to cool the evap along with the fuel vapourisation and provide a rich gasious mixture exiting them that only needs a bit more air to get combustion going . We don't want too much air going down the evap as it'd probably overcool it with possible fuel evaporation problems , but we don't want it so hot that the tubing shows signs of heat stress such as Anders tubes appeared to have , its a juggling act that will probably change from engine to engine depending on the air/gas flow patterns within the flametube as well as the radiation levels from different fuels etc etc etc ..... a trial and error approach required maybe . Cheers John Hi John, What if I fit a new set of evap tubes with the pressed imprints you have made on yours? Getting bellmouthed tubes with <0.5mm wall thickness will probably be difficult, welding them in place won´t be easy and I don´t trust silver solder since they are sitting directly in the NGV outer wall. The wall thickness of my evaps is 0.9mm. Hi Anders Nice mountain views Looks a bit cold with all that snow , .................LOL, you need to grow a bit more hair on your head ;-) Cheers John I had to use a hat since it became a bit cold later in the day. Hi Anders I did some "numbers" for the "tighter" turb wheel and they work out OK , but the clipped wheel you're currently running would have a bit more "potential" if at some stage you want to really push the temperatures and/or fit "augmentation" , theres less chance of the exducer causing problems ..............theres considerably more exhaust swirl with the unclipped wheel if we have to use high gas speeds through the exducer to exit the required flow at the higher temps . Stick with your current setup , your "top end" temperatures aren't excessively hot, after all , yours is a race bike wanting max power , cool temperatures only give mediocre power :-) Cheers John Hi John, Then I´ll use the old turbine wheel and try to get my hands on a good TOT gauge. I can buy an Autometer EGT gauge that should be as accurate as they get since they are relatively expensive and used in many dragracing applications. Cheers! /Anders
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Post by finiteparts on Oct 19, 2014 15:43:27 GMT -5
Hi Anders,
I don't think that you would have to choke the vent line to build pressure in the system. If the restriction in the vent line was enough to require a certain pressure ratio to "drive" the flow out of the line, then as the inlet pressure to the oil tank increased (due to higher leakage through the piston ring), the internal pressure of the tank would similarly rise to meet the required ratio. You could actually calculate that in the same way as the was done for the 90 degree bend, but you would use all the flow elements (elbows,fittings, etc) and sum their contributions to the overall pressure loss.
Another idea on the thermocouples for the final engine setup. Since you really don't care about the actual gas temperature, you care about the amount of heat transfer to the metal parts and their ultimate temperature, you could measure that more directly. Drilling a passage close to the leading edge of a NGV, you could braze in several 0.040" typeK TCs. You would then be reading the average metal temperatures near the leading edge. Just thought that I would throw that idea out there, since it reduces the uncertainties due to flow errors, conduction errors and radiation errors on what the real gas temperature is.
Also, is anyone else having problems seeing the photos on the first 6 pages of this thread? The pictures on page 7 and onward load fine, but nothing on page 1-6. I tried in Google Chrome, Firefox and IE8, on two computers, cleared histories, etc....with no luck.
~ Chris
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Post by racket on Oct 19, 2014 16:17:01 GMT -5
Hi Anders With your tank breathers , may I suggest you don't vent the gearbox to atmosphere , if for any reason the gearbox drainage doesn't work it'll fill with oil and dump overboard ,this happened to me with my first bike build , I then fitted the gearbox breather with plumbing back to the oil tank "air space" where the gearbox then vented out of the oiltank breather , problem solved , no more dumping oil when I forgot to turn on the gearbox scavenge pump. As for TOT instruments , I've been very happy with my YCT units www.instrumentchoice.com.au/instrument-choice/environment-meters/ic-yc-821-2-channel-k-type-temperature-meter coupled up to a pair of sheathed thermocouples 0.9 mm WT for the evaps is pretty reasonable , maybe you only need a more heat resistant material and perhaps a bellmouth to get a bit more airflow into them to prevent any temp stress , the "D'ing" of the tube does help with promoting turbulence within the evap as the air/fuel is forced from side to side, hopefully preventing a "laminar??" flow which might not be helpful for either the evaporation of the fuel or cooling the evap walls , full sized engines use "turbulence pins" in the mouth of their evaps. A bellmouthed evap tube fitted into a "bellmouthed" hole in the NGV wall would be a reasonably "easy??" TIG welding job with your skill level . Cheers John
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Post by Johansson on Oct 20, 2014 13:30:29 GMT -5
Hi Anders, I don't think that you would have to choke the vent line to build pressure in the system. If the restriction in the vent line was enough to require a certain pressure ratio to "drive" the flow out of the line, then as the inlet pressure to the oil tank increased (due to higher leakage through the piston ring), the internal pressure of the tank would similarly rise to meet the required ratio. You could actually calculate that in the same way as the was done for the 90 degree bend, but you would use all the flow elements (elbows,fittings, etc) and sum their contributions to the overall pressure loss. Another idea on the thermocouples for the final engine setup. Since you really don't care about the actual gas temperature, you care about the amount of heat transfer to the metal parts and their ultimate temperature, you could measure that more directly. Drilling a passage close to the leading edge of a NGV, you could braze in several 0.040" typeK TCs. You would then be reading the average metal temperatures near the leading edge. Just thought that I would throw that idea out there, since it reduces the uncertainties due to flow errors, conduction errors and radiation errors on what the real gas temperature is. Also, is anyone else having problems seeing the photos on the first 6 pages of this thread? The pictures on page 7 and onward load fine, but nothing on page 1-6. I tried in Google Chrome, Firefox and IE8, on two computers, cleared histories, etc....with no luck. ~ Chris Hi Chris, That is true, I´ll make sure to make a proper vent for the tank (or leave the tank lid off in case I don´t have time) before I do another test run. Hmm, that could prove problematic since I have the entire NGV cheramic coated so any temp reading will probably be unreliable at best. The first pictures were on a different server and disappeared when I changed web hotel for the homepage, I should be able to figure out which pics that disappeared and upload them on my Photobucket account when I have a couple of spare hours. Cheers! /Anders Hi Anders With your tank breathers , may I suggest you don't vent the gearbox to atmosphere , if for any reason the gearbox drainage doesn't work it'll fill with oil and dump overboard ,this happened to me with my first bike build , I then fitted the gearbox breather with plumbing back to the oil tank "air space" where the gearbox then vented out of the oiltank breather , problem solved , no more dumping oil when I forgot to turn on the gearbox scavenge pump. As for TOT instruments , I've been very happy with my YCT units www.instrumentchoice.com.au/instrument-choice/environment-meters/ic-yc-821-2-channel-k-type-temperature-meter coupled up to a pair of sheathed thermocouples 0.9 mm WT for the evaps is pretty reasonable , maybe you only need a more heat resistant material and perhaps a bellmouth to get a bit more airflow into them to prevent any temp stress , the "D'ing" of the tube does help with promoting turbulence within the evap as the air/fuel is forced from side to side, hopefully preventing a "laminar??" flow which might not be helpful for either the evaporation of the fuel or cooling the evap walls , full sized engines use "turbulence pins" in the mouth of their evaps. A bellmouthed evap tube fitted into a "bellmouthed" hole in the NGV wall would be a reasonably "easy??" TIG welding job with your skill level . Cheers John Hi John, That is a good pointer, I have the chance to do this properly now when I will clean out the tank and fix the cracked weld. I have severe problems finding anything better than 316L (ss2348, 1.4404) as 10mm thin walled tube, so that´ll have to do. I´ll make a jig to make the dents in the sides of it and a bellmouth. Perhaps this will decrease the temps somewhat since the ejection marks in my FT might be indications that the kero isn´t perfectly vaporised when it exits the tubes. Fingers crossed. I will try to borrow an industrial oven to test the thermocouples against each other, chances are that it has a high quality temp controller that I can use as a reference for the temps. Cheers! /Anders
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Post by racket on Oct 20, 2014 16:43:28 GMT -5
Hi Anders
If you can get your TOT systems checked for accuracy in that crucial 600-900 C range it'd be good , you really need to have confidence in the temperature you're reading is correct if you want to run the engine right up to its temperature limits to make the best power safely.
I got so frustrated with my TV84 jetpipe numbers I constructed a long (0.75 metre) diffusing jetpipe to slow down the gases to reduce dynamic pressures and temperatures to a more "static" state as well as giving the gases time to mix within the rather large volume of the diffuser so that there'd be less temp variations , it did help even things out with regards to pressures , there only being an understandable ~1psi difference between static and total pressures at the end of the diffusing section before the jet nozzle started doing its thing , but temperatures were still all over the place, so I knew it was instrument problems not positional problems causing the big differences in reading .
The 316L tubing should be OK if the "cooling" is adequate , the D'ing and a bellmouth should make that possible , ....................how far from your evap inlets is the fuel manifold ?? we probably need a minimum of 4-5mm so that air can easily enter the evap .
Just a few minor changes and she'll be burning kero again :-)
Cheers John
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Post by Johansson on Oct 21, 2014 4:29:27 GMT -5
Hi John, It sounds like I will have access to an oven that can handle those temps, so as soon as I get the new thermocouples that Ernie suggested I will visit my friend and try them out. The evap tube material will hopefully arrive in a day or two, we have a large discount on such stuff at my work and I was allowed to buy it through my company so I will only pay 40 euros for a 6 meter long 10mm 316L tube. The fuel manifold is offset so it has a smaller diameter than the evap holes, so no blocking at all. Tonight I will start making the rear fairings for the bike, lots of stuff to get done before the bike is ready for racing. Cheers! /Anders
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ozbooster
Member
Joined: October 2013
Posts: 28
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Post by ozbooster on Oct 21, 2014 15:09:39 GMT -5
Anders if it helps at all here is a write up on building a simple aerodynamic fairing a guy in our dry lakes racing put together , i know its much more than your planning but the basics may help www.dlra.org.au/forum/viewtopic.php?f=18&t=1320
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Post by racket on Oct 21, 2014 17:33:14 GMT -5
Hi Anders
6 metres , enough for 3 engines, good price :-)
Cheers John
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Post by Johansson on Oct 22, 2014 4:08:05 GMT -5
Anders if it helps at all here is a write up on building a simple aerodynamic fairing a guy in our dry lakes racing put together , i know its much more than your planning but the basics may help www.dlra.org.au/forum/viewtopic.php?f=18&t=1320Thanks for the link! For this I will do a simple styrofoam plug, coat it with glass fiber and grind the foam away from the inside. I don´t have the time or patience to do it the "proper" way, and the result will most likely look just as good on the outside. Hi Anders 6 metres , enough for 3 engines, good price :-) Cheers John Yup, lots of material for any later versions of the engine.
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