CHTs too cold?

[N201MKTurbo]

I wonder if anybody has built a system to run an airplane on CNG or LNG?

[GeeBee]

Not a good idea, the only thing worse would be propane.

 

 

[N201MKTurbo]

13 minutes ago, GeeBee said:

Not a good idea, the only thing worse would be propane.

 

 

Why do you say that?

[PT20J]

4 hours ago, tmo said:

Is 8.5:1 (Lycoming O-360A1A, first from the list of Lycoming O-360 variants on Wikipedia) really high compression ratio? I know it's apples to oranges, but Mazda gasoline engines are 14:1; yes, not supercharged, with direct injection, and a clean sheet design, of course, but I thought 8.5:1 was average at best, even in the heyday of GA.

The Auto Fuel STC lists many engines, from Lycoming O-235 to O-540, including a bunch of O-360's. Even Lycoming themselves list automotive fuels as acceptable for many engines in their SI1070 - admittedly just the normally aspirated ones (but even the AEIO-540-D).

I understood the bigger issue was with the fuel delivery system and the difficulty to prove vapor lock would not happen.

I am purposefully ignoring the subject of ethanol in car gas; there are unleaded aviation fuels, like the HJELMCO 91/96 UL listed in the Lycoming SI, just not 100 octane. They are not popular, I'll grant you that, but if 100LL suddenly doubled in price...

On a total thread drift - how much lead is in leaded automotive fuels, as compared to 100LL? Enough to wonder about bringing them back (which I realize will not happen, but still)?

I'm not a Mazda owner, but 14:1 sounds high -- getting close to Diesel territory. According to Wikipedia (not always accurate) the Mazda engines have compression ratios ranging from 9.1:1 to 12.1:1. But, that's still quite a bit higher than most aircraft engines.

Automobile engines and aircraft engines lead very different lives. Auto's cruise at 10-15% power. Full power is rarely needed. They are designed for low emissions and fuel economy. They can run higher compression ratios because they don't need to put out high power for sustained periods. High compression ratios increase efficiency but reduce detonation margin. The reduced detonation margin is offset somewhat by combustion chambers designed for a fast burn which doesn't give the end gas enough time at high pressure and temperature to auto ignite. And, the knock sensor can always dial back the timing if necessary which wouldn't be a good thing in an airplane at takeoff.

It is apparently very difficult to economically create a 100/130 octane fuel without TEL.

It's probably much harder to make current engines certified for 100 octane fuel safely put out their rated power on fuel of lower octane.

Skip

[PT20J]

1 hour ago, N201MKTurbo said:

None of the electronic ignition systems out there now advance the timing more than the fixed timing we now have at full power.

I believe that the fixed timing is set for MBT (Maximum Brake Torque) at rated power. Everything else is a compromise. The compromise isn't bad at higher powers and ROP -- should only be a couple of percent power deviation over the ROP range. At lower powers (high altitudes for a normally aspirated engine) and LOP (increased burn time throws timing off optimum) more advance is beneficial.

A lot has made the effect of rpm because supposedly the burn time is constant so increased rpm gives a shorter amount of time (or crankshaft angle ) for the mixture to combust and therefore requires more advanced timing. I've been reading several textbooks lately and it turns out that this effect is not 1:1 since increased rpm increases the turbulence in the cylinder which has the effect of decreasing burn time. Over the narrow range of cruise power rpm used in airplanes, the effect is really very small. Which is another reason that the fixed timing works.

Skip

[carusoam]

So....

The IO550 in the O1... naturally limited to 2500rpm...

Is approved for using 100LL and 100 (no lead)

When was this fuel ever available?  1994 in Alabama?

Best regards,

-a-

[PT20J]

56 minutes ago, carusoam said:

So....

The IO550 in the O1... naturally limited to 2500rpm...

Is approved for using 100LL and 100 (no lead)

When was this fuel ever available?  1994 in Alabama?

Best regards,

-a-

Anthony, I think that the 100 means 100/130 (green) not no lead. The lead was understood until the 100LL was introduced. 

Skip

[carusoam]

38 minutes ago, PT20J said:

Anthony, I think that the 100 means 100/130 (green) not no lead. The lead was understood until the 100LL was introduced. 

Skip

I’ll have to pull the reference...

-a-

Looks like I mis-read this a decade ago... I thought that was a comma, not a dash...

 

[GeeBee]

18 hours ago, N201MKTurbo said:

Why do you say that?

It takes huge tanks. LNG requires 70% higher volume tank than a diesel tank for the same amount of range. As for Propane, huge fire risks and even worse detonation risk. My neighbor who used to be commander of the Miami-Dade bomb squad calls it "poor man's dynamite". It is a ubiquitous fuel but has very high energy content that is difficult to control when it leaks. The Santa Clara County transit system first bought propane powered busses. Within a month, 3 of them burned to axles. 

In aerial vehicles, the use of flammable gas? Well Hindenburg comes to mind.

 

[N201MKTurbo]

1 hour ago, GeeBee said:

It takes huge tanks. LNG requires 70% higher volume tank than a diesel tank for the same amount of range. As for Propane, huge fire risks and even worse detonation risk. My neighbor who used to be commander of the Miami-Dade bomb squad calls it "poor man's dynamite". It is a ubiquitous fuel but has very high energy content that is difficult to control when it leaks. The Santa Clara County transit system first bought propane powered busses. Within a month, 3 of them burned to axles. 

In aerial vehicles, the use of flammable gas? Well Hindenburg comes to mind.

 

LNG has more energy per pound than diesel, quite a bit more than gasoline. You need about 40% more volume than gasoline for the same energy. It has an octane rating of 120.

I have worked with cryogenic liquids quite a bit and think you could make light weight tanks insulated with EPS. The fuel wouldn’t last days, but it would last the flight with no loss. You could make long term tanks, but they would be heavier and much more expensive. 
 

Cost wise, it is about 25% the price of avgas.

 

The hard part would be getting LNG facilities at airports.

 

A bonus is the latent heat of vaporization is quite high, you could get free air conditioning, or a super duper oil cooler.

[GeeBee]

But you have a volume and weight problem. To obtain the same BTU you need 50% larger tank for LNG. So you have larger and heavier tanks. Look at the GGE tables for gasoline versus LNG. Gasoline has a about 114K btu/gal vs 75K btu/gal for LNG. We have not even discussed the weight of the tank. A wet wing like a Mooney is a pretty efficient way to store BTU's because it is an integral structure. LNG would require a separate tank and a fairly robust one at that to deal with the pressures.

 

[N201MKTurbo]

13 minutes ago, GeeBee said:

But you have a volume and weight problem. To obtain the same BTU you need 50% larger tank for LNG. So you have larger and heavier tanks. Look at the GGE tables for gasoline versus LNG. Gasoline has a about 114K btu/gal vs 75K btu/gal for LNG. We have not even discussed the weight of the tank. A wet wing like a Mooney is a pretty efficient way to store BTU's because it is an integral structure. LNG would require a separate tank and a fairly robust one at that to deal with the pressures.

 

As I stated LNG has more energy per pound than avgas. It does take about 40% more volume because of the lower density.

I propose a short term storage tank. It would consist of a thin polyethylene liner with about 1/2 inch of EPS (expanded polystyrene) insulation, with a thin aluminum shell. The tank would require some kind of tension pillars in the tank to take the pressure without bulging. They could be  polyaramide or similar fibers. I think you could make the tank weigh less than a pound. The pressure isn’t that high usually around 20 PSI. The problem would usually be getting it to boil off fast enough, you would probably need some electric heaters in the tanks. Just for those cold days. 

 

 

[carusoam]

Holy cow!

We could be on to something...

Sure, the volume increases...

And the octane value goes the right direction...

We may want to increase the compression ratio with that...

As far as economics go... we can afford some scaled up wings when our fuel costs go so low...

+1 for throwing the polymer guys a bone... EPS = expanded polystyrene

We would want to improve on that as well... with an additive package to improve stability, and solubility with its environment...  in its raw form... it is the environmentally challenged coffee cup! 

PP thoughts only, mostly not a styrene coffee cup user...

Best regards,

-a-

[carusoam]

Additional reference for 100 vs 100LL...

two different fuels... 100 is the green colored one...

Two different densities...

At least three references spread throughout the POH for the M20R...

 

[GeeBee]

On 12/24/2020 at 5:40 PM, N201MKTurbo said:

As I stated LNG has more energy per pound than avgas. It does take about 40% more volume because of the lower density.

I propose a short term storage tank. It would consist of a thin polyethylene liner with about 1/2 inch of EPS (expanded polystyrene) insulation, with a thin aluminum shell. The tank would require some kind of tension pillars in the tank to take the pressure without bulging. They could be  polyaramide or similar fibers. I think you could make the tank weigh less than a pound. The pressure isn’t that high usually around 20 PSI. The problem would usually be getting it to boil off fast enough, you would probably need some electric heaters in the tanks. Just for those cold days. 

 

 

These questions

Do you think you could certify that design under FAR 23?

Do you think you could have self serve LNG refueling at midnight in Barstow, CA?

Why is it if I have a 100,000 tons of gasoline I can bring the ship right into port and offload it. But if I have 100,000 tons  of LNG I am offloading 3 miles offshore to a floating platform?

 

[carusoam]

There seems to be one guy that knows about shipping LNG.... if I knew how to spell Sharif Suhki’s name, I would have included it with a wiki link...

Compared to the number of people that know about gasoline...

One thing for sure... gasoline like its liquid form...  LNG does not...

 

Waiting for part 23 to get another update, to include LNG...  how many lifetimes would that take?

Best regards,

-a-

[N201MKTurbo]

8 minutes ago, GeeBee said:

These questions

Do you think you could certify that design under FAR 23?

Do you think you could have self serve LNG refueling at midnight in Barstow, CA?

Why is it if I have a 100,000 tons of gasoline I can bring the ship right into port and offload it. But if I have 100,000 tons  of LNG I am offloading 3 miles offshore to a floating platform?

 

My point was that it is a viable fuel that could run our engines at full power. 

Certainly, our current AVGAS is the simplest solution. I stated above that the refueling stations would be the biggest challenge. 

It would be more challenging than filling up with gasoline, but not to much more. Cooling a warm tank would vent a fair amount of gas. Not how sure how the environmentalists would handle that. The vent gas could be recovered and re-liquified.

Not my problem how they get it to the filling stations. Most major cities have LNG filling stations now, so it isn't tin hat craziness. 

Retrofitting it into our Mooneys would be a challenge. I was working on a Cherokee 6 recently and it would be easy to retrofit it into that airframe with its removable main and tip tanks.

[N201MKTurbo]

31 minutes ago, GeeBee said:

These questions

Do you think you could certify that design under FAR 23?

Do you think you could have self serve LNG refueling at midnight in Barstow, CA?

Why is it if I have a 100,000 tons of gasoline I can bring the ship right into port and offload it. But if I have 100,000 tons  of LNG I am offloading 3 miles offshore to a floating platform?

 

I don't see anything here that couldn't be accomplished with LNG.

23.2430   Fuel systems.

(a) Each fuel system must—

(1) Be designed and arranged to provide independence between multiple fuel storage and supply systems so that failure of any one component in one system will not result in loss of fuel storage or supply of another system;

(2) Be designed and arranged to prevent ignition of the fuel within the system by direct lightning strikes or swept lightning strokes to areas where such occurrences are highly probable, or by corona or streamering at fuel vent outlets;

(3) Provide the fuel necessary to ensure each powerplant and auxiliary power unit functions properly in all likely operating conditions;

(4) Provide the flightcrew with a means to determine the total useable fuel available and provide uninterrupted supply of that fuel when the system is correctly operated, accounting for likely fuel fluctuations;

(5) Provide a means to safely remove or isolate the fuel stored in the system from the airplane;

(6) Be designed to retain fuel under all likely operating conditions and minimize hazards to the occupants during any survivable emergency landing. For level 4 airplanes, failure due to overload of the landing system must be taken into account; and

(7) Prevent hazardous contamination of the fuel supplied to each powerplant and auxiliary power unit.

(b) Each fuel storage system must—

(1) Withstand the loads under likely operating conditions without failure;

(2) Be isolated from personnel compartments and protected from hazards due to unintended temperature influences;

(3) Be designed to prevent significant loss of stored fuel from any vent system due to fuel transfer between fuel storage or supply systems, or under likely operating conditions;

(4) Provide fuel for at least one-half hour of operation at maximum continuous power or thrust; and

(5) Be capable of jettisoning fuel safely if required for landing.

(c) Each fuel storage refilling or recharging system must be designed to—

(1) Prevent improper refilling or recharging;

(2) Prevent contamination of the fuel stored during likely operating conditions; and

(3) Prevent the occurrence of any hazard to the airplane or to persons during refilling or recharging.

[Jerry 5TJ]

A clean-burning LNG powered Mooney.  I like it!

Of course even after you get the vacuum insulated fuel tanks FAA certified (...) the LNG inside is still boiling away at a stable -130C at 100 psi.  (Just to pick a point on the LNG phase state diagram). Even with fabulous insulation the wing skins are likely to be very cold.  Encounter rain and the wing will be iced over instantly.  Self-induced SLD, so to speak.  

Maybe a set of TKS panels can be modified to seep natural gas vapor past combo VG/igniters and spread flames over the wing skins to deice them.   And augment thrust.  High temperature paint will be needed.  Should be spectacular at night and you won’t need position lights. 

When parked on the ramp the vented gaseous methane can be used for engine preheat or to run a BBQ grill for real $100 burgers.  

[r0ckst4r]

40 minutes ago, Jerry 5TJ said:

A clean-burning LNG powered Mooney.  I like it!

Of course even after you get the vacuum insulated fuel tanks FAA certified (...) the LNG inside is still boiling away at a stable -130C at 100 psi.  (Just to pick a point on the LNG phase state diagram). Even with fabulous insulation the wing skins are likely to be very cold.  Encounter rain and the wing will be iced over instantly.  Self-induced SLD, so to speak.  

Maybe a set of TKS panels can be modified to seep natural gas vapor past combo VG/igniters and spread flames over the wing skins to deice them.   And augment thrust.  High temperature paint will be needed.  Should be spectacular at night and you won’t need position lights. 

When parked on the ramp the vented gaseous methane can be used for engine preheat or to run a BBQ grill for real $100 burgers.  

Love the igniter/TKS panel idea lol.  Like a flying phoenix!

[N201MKTurbo]

2 hours ago, Jerry 5TJ said:

A clean-burning LNG powered Mooney.  I like it!

Of course even after you get the vacuum insulated fuel tanks FAA certified (...) the LNG inside is still boiling away at a stable -130C at 100 psi.  (Just to pick a point on the LNG phase state diagram). Even with fabulous insulation the wing skins are likely to be very cold.  Encounter rain and the wing will be iced over instantly.  Self-induced SLD, so to speak.  

Maybe a set of TKS panels can be modified to seep natural gas vapor past combo VG/igniters and spread flames over the wing skins to deice them.   And augment thrust.  High temperature paint will be needed.  Should be spectacular at night and you won’t need position lights. 

When parked on the ramp the vented gaseous methane can be used for engine preheat or to run a BBQ grill for real $100 burgers.  

Most LNG tanks are operated at 1 bar. 14 PSI. Most are insulated with fiberglass, not a vacuum barrier like a Dewar flask. 

BTW I have a dewar in my garage from when I used to work on the stuff all the time. It could use a suck down. It holds 25L I usually buy 5L of LN2 at a time. It used to last for about 2 months, now it only lasts for about 2 weeks. This is an open top Dewar and operates at ambient pressure. I seal the top with a Styrofoam coffee cup. The liquid stays at 77K at ambient pressure. So even with a poor vacuum the boil off rate is quite slow. If you fill a Styrofoam coffee cup with LN2, it will take about an hour for it to all boil off. If you put a coffee cup lid on it, it will last twice as long. You can hold the cup in your hand and it isn't cold at all.

Seeing that I'm on the subject, Stupid LN2 trick:

Make a support structure out of stiff wire to suspend a metal shot glass over the top of a Styrofoam cup. Fill the shot glass with LN2. you will notice a milky white liquid condensing on the outside of the shot glass and dripping into the coffee cup. That is liquid oxygen! It condenses above LN2 temperature. Wait till all the LN2 boils off, refill if you like, but when you are done sneak up on the coffee cup with a bar- b- que starter. It is better if you do this with a welding glove on. Light the lip of the cup on fire. The cup will disappear in front of your eyes in a bright flash of light.

 

FYI

LNG = Liquid Natural Gas

LN2 = Liquid Nitrogen

[GeeBee]

3 hours ago, N201MKTurbo said:

I don't see anything here that couldn't be accomplished with LNG.

23.2430   Fuel systems.

(a) Each fuel system must—

(1) Be designed and arranged to provide independence between multiple fuel storage and supply systems so that failure of any one component in one system will not result in loss of fuel storage or supply of another system;

(2) Be designed and arranged to prevent ignition of the fuel within the system by direct lightning strikes or swept lightning strokes to areas where such occurrences are highly probable, or by corona or streamering at fuel vent outlets;

(3) Provide the fuel necessary to ensure each powerplant and auxiliary power unit functions properly in all likely operating conditions;

(4) Provide the flightcrew with a means to determine the total useable fuel available and provide uninterrupted supply of that fuel when the system is correctly operated, accounting for likely fuel fluctuations;

(5) Provide a means to safely remove or isolate the fuel stored in the system from the airplane;

(6) Be designed to retain fuel under all likely operating conditions and minimize hazards to the occupants during any survivable emergency landing. For level 4 airplanes, failure due to overload of the landing system must be taken into account; and

(7) Prevent hazardous contamination of the fuel supplied to each powerplant and auxiliary power unit.

(b) Each fuel storage system must—

(1) Withstand the loads under likely operating conditions without failure;

(2) Be isolated from personnel compartments and protected from hazards due to unintended temperature influences;

(3) Be designed to prevent significant loss of stored fuel from any vent system due to fuel transfer between fuel storage or supply systems, or under likely operating conditions;

(4) Provide fuel for at least one-half hour of operation at maximum continuous power or thrust; and

(5) Be capable of jettisoning fuel safely if required for landing.

(c) Each fuel storage refilling or recharging system must be designed to—

(1) Prevent improper refilling or recharging;

(2) Prevent contamination of the fuel stored during likely operating conditions; and

(3) Prevent the occurrence of any hazard to the airplane or to persons during refilling or recharging.

You did not answer the second and third question.

 

[N201MKTurbo]

3 minutes ago, GeeBee said:

You did not answer the second and third question.

 

I thought I did.

"Not my problem how they get it to the filling stations. Most major cities have LNG filling stations now, so it isn't tin hat craziness."

They expect us as pilots to do complex operations. Do you think operating a LNG filling station is beyond a pilots capabilities?

Edited December 26, 2020 by N201MKTurbo

[GeeBee]

No but I suspect the fire Marshalls are going to have something to say about self serve LNG.

[carusoam]

Depends on where you live...

In NJ, we don’t have SS gas stations... yet...

-a-