Aircraft oils on cars

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You can not maintain an aircraft in flight, only on the ground. You're also thinking of only commercial aircraft and not all aircrafts. Military aircrafts in war time have a mission to accomplish and a maintenance light is not really a pilot concern on a multi-engine air vehicles. It is people like me that will have to deal with it when the aircraft come back from a sortie. I decide whether an aircraft is combat ready or not. Under the Army Spectrometric Oil Analysis Program (ASOAP) oil samples are analyzed for metal content, to prevent in-flight engine failures. If combustion by products are found then the engine is scheduled for an overhaul at the earliest opportunity. You admitted you don't know how jet oil could get contaminated and I have described one condition where it will happen. I have not discussed battle damage situations (direct or indirect) because it is beyond a normal flight plan. Just because you don't understand jet engine does not mean that it can not happen.

Maxima oil has twice the ZDDP of some (not all) oils in the same classification and this is a fact. If other AW additives are not shown via UOA or VOA then how do you know that Maxima does not also have twice as much? Redline is another well know brand that overkill on AW additives for a given classification, may be not 50% but not very far from it.
 
Originally Posted By: MolaKule


In an axial flow turbine, the flame of combustion is contained in the combustor cans or ring (annular) combustor at the rear of the engine with the support and thrust bearings in bearing cells (self-contained bearing assemblies with seals) and BEFORE the combustor chamber. The oil is under slight oil pressure for circulation/cooling purposes.

Now the PT6A turboprop engine uses both an axial and centrifugal compressors in a reverse flow configuration.

I suppose if a labyrinth seal is really worn some oil could migrate or flow out and into the compressor stage(s) and be sent to the combustor where it would be burned. But then again, we're talking about a maintenance problem here.


High-pressure bleed air has a pressure of about 160 psi and a temperature of more than 650° F when operating near sea level. This air is taken from the rear of the high-pressure compressor. Leaked oil is burned then suck/forced back into the sump by the scavenger pump.

http://www.exxonmobil.com/lubes/exxonmobil/emal/files/TTopic13_JetEng1.pdf

http://www.exxonmobil.com/lubes/exxonmobil/emal/files/TTopic14_JetEng2.pdf
 
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Leaked oil is burned then suck/forced back into the sump by the scavenger pump.


Concentrating on the sump/dry cavity area for a moment, how can this happen if a postive pressure in the dry cavity is greater than the sump pressure? The whole point of a differential pressure across the seals is to contain the the oil in the wet sump.

Why would you want to burn leaked oil and then force it back into the sump? Burned liquid oil would become a vapor or gas, a process called "phase change."
 
Do you find fuel dilution to be an issue in turbine engine oil systems? It is an issue with piston engine oils.
I understand burnt oil vapor being reintroduced through the scavenge system but you haven't described how hot combustion gasses get into the oil system. I'm talking about from the hot section into the oil system. The systems I've worked on only have one potential area for combustion gas to enter a sealed area, between the LPT and HPT and if you are getting 900*C gas into that area you've got major issues with the bleed air system, the engine is no longer going to function.

The only carbon buildup I've seen has been external leakage. I certainly don't see any common parts or situations between piston engines and turbines. Maybe it is different for rotary wing aircraft or GTC/APUs but I haven't seen it in anything based on the GE F110 series (or derivatives) or the Allison T-56.
 
Originally Posted By: MolaKule

Concentrating on the sump/dry cavity area for a moment, how can this happen if a positive pressure in the dry cavity is greater than the sump pressure? The whole point of a differential pressure across the seals is to contain the the oil in the wet sump.

Why would you want to burn leaked oil and then force it back into the sump? Burned liquid oil would become a vapor or gas, a process called "phase change."


Leaked oil is burned then vapor/gas get suck/forced back into the sump due to the low or no oil pressure and worn seals. Pump failure and low oil volume are the two main reasons. During the first Gulf war there was a high turbine engine failure rate due to powder sand particles wearing out the seals and other parts at an alarming rate. New seals were designed and upgraded but not until about almost a year later. We were replacing main rotor blades every weeks until it was upgraded with a polymer jacket due to the sand storms. The war does not stop for a sand storm.
 
Originally Posted By: tom slick
Do you find fuel dilution to be an issue in turbine engine oil systems?

I understand burnt oil vapor being reintroduced through the scavenge system but you haven't described how hot combustion gasses get into the oil system. I'm talking about from the hot section into the oil system.


Fuel dilution is not an issue with any of the turbine engine I have worked with.

Burnt oil vapor at 600F is more than enough to destroy the lubrication system of any engine. But, to answer your question of how hot gases from the combustion chamber gets into the oil you need to look at the M1 Abram Tank. Due to packaging and performance requirements the exhaust gases are routed to reduce IR signature and eliminate smokes (some of this is classified information). So, the forward/turbine module sits right in front of the gear reduction module and on top of the accessories gear box module and surrounded by armor. The reduction gear box is nested inside the exhaust manifold. A heat shield is provided around the gearbox and cooling air is provided between the heat shield and the gearbox, to reduce the heat input from the exhaust gases to the gearbox.

Most of the oil contamination with combustion gases originated at the reduction gear box due to extreme heat and worn bearings/seals.
 
Ok, maybe I should have been more specific.

In an AXIAL flow jet turbine operating normally (such as the P&W100 or PW6000 or JT15, GE F101 or CFM56-5, or RollsRoyce Trent or RB211 or Williams FJ44-1A), how do the combustor gasses get into the lubrication system, barring any catastrophic failures.
 
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On rare occasion, full reverse thrusting at slow speed will force the combustion gases (and debris) back into the intake which will then seep pass the seals and bearings.
 
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full reverse thrusting at slow speed will force the combustion gases (and debris) back into the intake which will then seep pass the seals and bearings.


Please define intake? Do you mean the reverse thrust gasses will flow around the nacelle and re-enter the compressor stage, or that the oil aireator will ingest dirty gasses?
 
okay, you win. you have described in minute detail how a turbine engine's oil and a piston engine's oil see the same types of conditions
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maybe you should try gear oil or hydraulic oil next, both can be high grade synthetics, roughly the same viscosity as motor oil, and as you have proved you don't really need to pay any attention to their chemical compositions as long as they are synthetic.
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Originally Posted By: MolaKule

Please define intake? Do you mean the reverse thrust gasses will flow around the nacelle and re-enter the compressor stage, or that the oil aerator will ingest dirty gasses?


Full reverse thrust at slow speed will pretty much blanket the intake nacelle with reverse thrust gasses and debris. The engine is now compressing exhaust gas that were generated moment earlier. This usually increases the intake air temperature of about 400F, so the compressed air temperature at the last compression stage is now above 1000F. The compression pressure also increases accordingly. The engine can take the additional stress for a very short period, but most of the damages to the compressor blades, seals and bearings are done by the debris (sand, rocks, ice chunks, etc.) Have you ever seen a helicopter hover in ground effect? In a sandy environment you will see two sand vortexes looping through the main rotor blade. The same principle applies to reverse thrust on jet engine, albeit at a faster speed.

On a fixed test stand you can vaporize most of the oil in the sump in less than a minute with full reverse thrust. In the commercial world the FAA regulates the use of reverse thrust at most airport but not in the military.
 
Originally Posted By: tom slick

maybe you should try gear oil or hydraulic oil next, both can be high grade synthetics, roughly the same viscosity as motor oil, and as you have proved you don't really need to pay any attention to their chemical compositions as long as they are synthetic.
thumbsup2.gif



I recycle all my used oil through my diesel pickup truck as fuel so I do not waste any thing. The reason I blend my own oil is because I do know the chemical compositions and not because of the internets. Not counting colleges, I have gone through many training classes from engine manufacturers and spent thousands of hours under the worst conditions working on them to get my CW4. Unlike you, I don't just listen to internet experts.
 
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Interesting discussion and I am glad you recycle your oil by burning.


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The engine is now compressing exhaust gas that were generated moment earlier. This usually increases the intake air temperature of about 400F, so the compressed air temperature at the last compression stage is now above 1000F.


At reverse thrust, the exhaust gas temperature from a JT9D turbofan exhaust nozzle with an intake air temp of 59 F, is around 400 F, and there will be a lot of turbulent mixing with the 59 F air as the air comes around to the Fan, so I seriously doubt the intake air temp to the fan or first stage compressor is 400 F.

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The compression pressure also increases accordingly.


The pressure at the last vane in the HPC is only 316 psia. Warmer air is less dense air. So how would you get 1000 psia at this point?

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On a fixed test stand you can vaporize most of the oil in the sump in less than a minute with full reverse thrust.


With the PW4077 test stand, we never did vaporize anything.

As to helicopters, yes a lot of crud is kicked up on landing and takeoff, but most of the particles are usually swept out and bypassed, and we do have oil filters for trapping most particles, assuming they would get by the seals.

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The reason I blend my own oil is because I do know the chemical compositions and not because of the internets.


Then maybe you can guide us through ester production and the exact additive components in the 254 or similar JTO's.
 
Originally Posted By: MolaKule


At reverse thrust, the exhaust gas temperature from a JT9D turbofan exhaust nozzle with an intake air temp of 59 F, is around 400 F, and there will be a lot of turbulent mixing with the 59 F air as the air comes around to the Fan, so I seriously doubt the intake air temp to the fan or first stage compressor is 400 F.


You have misread my post. The air at the last stage of compression before combustion can be as high as 650F at sea level depending on the engine. On a bucket or target type reverser the exhaust is blown toward the intake nacelle and the temperature there is not 59F. How do you get temperature of 59F when outside air temperature is over 120F such as in Arizona or Iraq? Jet exhaust temperature can be as high as 2800F so how much do you think it will cool off traveling 30ft? The recycle (reheat) exhaust air will add to the temperature at the last stage of compression and it could reach 1000F. This will cause a power surge at slow speed.


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The pressure at the last vane in the HPC is only 316 psia. Warmer air is less dense air. So how would you get 1000 psia at this point?


where did I said 1000psia? I said the pressure will increase accordingly which means that it will be higher than without reverse thrust.

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With the PW4077 test stand, we never did vaporize anything.

As to helicopters, yes a lot of crud is kicked up on landing and takeoff, but most of the particles are usually swept out and bypassed, and we do have oil filters for trapping most particles, assuming they would get by the seals.


Again, you either have misread my post or don't know what hover in ground effect means. The vortex you see with helicopter IGE is the same principle as the reverse thrust exhaust going back into the intake nacelle. The helicopter main rotor blade is the jet engine fan. The ground is the reverser bucket. The vortex of sand and dirt is the same as the vortex of the jet exhaust gas going in and out of the jet engine.

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Then maybe you can guide us through ester production and the exact additive components in the 254 or similar JTO's.


The Army spent over 5 million dollars training me to be an expert in my MOS and you want to know how for free? How about joining the military and they will teach you everything you need to know about jet engine and how to operate them. You will then spend years taking them apart and putting them together under all kind of conditions and not just in a hangar. You will then get to review and approve all engine qualification data including the lubricant used. Then you can witness all airworthiness qualification testing including the lube test. Then you can get out into the civilian life and get a job as a subcontract for jet engine manufacturers testing/repairing their engines in real life. And along the way the lub manufacturer like Mobil will come by whenever they can to make sure you know what is up with their latest oil and sell you several pallets for your business. By then you should pretty much know what is the composition of the oil you are using.
 
I was using the 59F temp and the JT9D as a starting point for discussion since you would not stop going off on tangents. We could use engineering STP if you like.

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The helicopter main rotor blade is the jet engine fan. The ground is the reverser bucket. The vortex of sand and dirt is the same as the vortex of the jet exhaust gas going in and out of the jet engine.



Yes I understand the principles of reverse thrust since I helped design the translation sleeves for Boeing Nacelles, so you need not be condencending to me or anyone else.

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You have misread my post. The air at the last stage of compression before combustion can be as high as 650F at sea level depending on the engine. On a bucket or target type reverser the exhaust is blown toward the intake nacelle and the temperature there is not 59F. How do you get temperature of 59F when outside air temperature is over 120F such as in Arizona or Iraq? Jet exhaust temperature can be as high as 2800F so how much do you think it will cool off traveling 30ft? The recycle (reheat) exhaust air will add to the temperature at the last stage of compression and it could reach 1000F. This will cause a power surge at slow speed.


Let's try to stay on topic here. Using the JT9D as our basis for discussion, and using 59 F as the ambient temperature, the last HPC stage temp and the combustor inlet temp will be about 850 F, the flame temp out of the combustor will be 1970 F, the HP turbine inlet temp will be about 1900 F, the LP turbine inlet temp will be about 850F so the nozzle temp will be 400 F. Energy is extracted by the LP turbine so the temp drops across the LP turbine due to thermodynamic principles. So if the nozzle air temp is 400, there is no way the fan inlet temp can be 400 F after mixing. AGain, you are assuming that most if not all of the exhaust gasses get back to the fan stage.

I will use the Artic, (you used Arizona and IRAQ) the mixing would still produce a relatively cool air into the intake. The inlet air temp into the nacelle will be higher than 59 but not 400 F.

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The Army spent over 5 million dollars training me to be an expert in my MOS and you want to know how for free? How about joining the military and they will teach you everything you need to know about jet engine and how to operate them. You will then spend years taking them apart and putting them together under all kind of conditions and not just in a hangar. You will then get to review and approve all engine qualification data including the lubricant used. Then you can witness all airworthiness qualification testing including the lube test. Then you can get out into the civilian life and get a job as a subcontract for jet engine manufacturers testing/repairing their engines in real life. And along the way the lub manufacturer like Mobil will come by whenever they can to make sure you know what is up with their latest oil and sell you several pallets for your business. By then you should pretty much know what is the composition of the oil you are using.


Again you attempt to change topics and go off on tangents. Just admit, "I am not a formulator or tribiologist and know little about esters and additive chemistry, but I am a first-rate jet engine mechanic with a lot of training and expereince," of which I have no doubt. Your hatred of the internet as an information souce is understood.
 
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Originally Posted By: MolaKule
I was using the 59F temp and the JT9D as a starting point for discussion since you would not stop going off on tangents. We could use engineering STP if you like.

Yes I understand the principles of reverse thrust since I helped design the translation sleeves for Boeing Nacelles, so you need not be condencending to me or anyone else.


Apparently not according to your previous post about the air being filtered, etc.

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Let's try to stay on topic here. Using the JT9D as our basis for discussion, and using 59 F as the ambient temperature, the last HPC stage temp and the combustor inlet temp will be about 850 F, the flame temp out of the combustor will be 1970 F, the HP turbine inlet temp will be about 1900 F, the LP turbine inlet temp will be about 850F so the nozzle temp will be 400 F. Energy is extracted by the LP turbine so the temp drops across the LP turbine due to thermodynamic principles. So if the nozzle air temp is 400, there is no way the fan inlet temp can be 400 F after mixing. AGain, you are assuming that most if not all of the exhaust gasses get back to the fan stage.

I will use the Artic, (you used Arizona and IRAQ) the mixing would still produce a relatively cool air into the intake. The inlet air temp into the nacelle will be higher than 59 but not 400 F.


You are using a specific example whereas I was using turbine engines in general. Why use the JT9D instead of any engine in a worst case scenarios? If every thing is working per design then we would not have this discussion. You asked since you don't know how the oil could get contaminated and I have given you a situation where it could. Engine designs do make a different in the health of the engine. For example, if you use compressed air for reverse thrust air then the temperature will be lower. If you use exhaust air then it will be hotter. Have you ever seen a blue flame coming out of the exhaust of a jet engine? Do you think the temperature of that blue flame is 400F degrees? 650C (1,200F)is a pretty typical maximum value for turbojet engines without reheat. With reheat temperatures as high as 2,500C are possible. F-14 Tomcat full reheat temperature at 4' from the nozzle is given as 1,300C (2,372F) in the flight manual.

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Again you attempt to change topics and go off on tangents. Just admit, "I am not a formulator or tribiologist and know little about esters and additive chemistry, but I am a first-rate jet engine mechanic with a lot of training and expereince," of which I have no doubt. Your hatred of the internet as an information souce is understood.


You are the one keeping changing the the original topic from aircraft oil usage in car, to how does oil get contaminated, to how to formulate ester based oil, etc. I have never claimed to be a formulator or a tribiologist only a CW4 in Army Aviation. I do know the chemistry of the oil and if you go back earlier in this thread (post #941851) I have given some of the additives in jet oil. The reason I know about the composition of the oil and not how to make them is because, as I have stated earlier, I get the data package from the oil manufacturer for the oil used in our engines. For engine performance qualification and airworthiness qualification the manufacturer have to submit a data package of how to manufacture the engine and the specs of every thing needed to run it. That is why there is a mil-spec for turbine oil and the oil manufacturers have to meet that spec. We just don't get an MSDS or a PDS from the oil manufacturers. We get all of their qualification test data and the list of chemical compositions. The list is proprietary information otherwise I would have posted them here verbatim.

Any other off topic item you would like to discuss?
 
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Originally Posted By: azsynthetic
Originally Posted By: MolaKule

Concentrating on the sump/dry cavity area for a moment, how can this happen if a positive pressure in the dry cavity is greater than the sump pressure? The whole point of a differential pressure across the seals is to contain the the oil in the wet sump.

Why would you want to burn leaked oil and then force it back into the sump? Burned liquid oil would become a vapor or gas, a process called "phase change."


Leaked oil is burned then vapor/gas get suck/forced back into the sump due to the low or no oil pressure and worn seals. Pump failure and low oil volume are the two main reasons. During the first Gulf war there was a high turbine engine failure rate due to powder sand particles wearing out the seals and other parts at an alarming rate. New seals were designed and upgraded but not until about almost a year later. We were replacing main rotor blades every weeks until it was upgraded with a polymer jacket due to the sand storms. The war does not stop for a sand storm.

The erosion on the rotors and on the props of aircraft in ideal conditions shows up pretty quick. Though I am not an expert it is just an observation. As I like to say dirt is the true enemy of machinery.
 
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