Cabin heat solutions?

[carusoam]

Hmmmmm…

ROP vs. LOP….

The excess gasoline can’t burn until it sees matching amounts of O2… that can’t happen until it leaves the exhaust pipe…

As far as fuel conversion goes for heat… LOP vs. ROP won’t make much of a difference… the closer to peak, the better the heat supply will be…

There is technically differences when some exhaust products are CO vs. CO2… CO gives off some more heat when it gets fully converted to CO2…

In an NA engine… above 8k’… operating at peak is OK for me…. WOT too….

 

A cursory check of the heating system is always a good idea…

Be on the look out for loose, damaged, or disconnected hoses, or any issues holding the exterior of the heat muff together…

 

PP thoughts only, 

-a-

[GeeBee]

No, the excess fuel continues to burn longer in the pipe. I used to play with the flame length at night in a Beech 18 when I got bored. Move the mixture rich, flame gets longer, move it lean, flame shortens. The combustion process does not end when the exhaust valve opens. Basically by running ROP you are "heating the pipes" with a longer exit flame. It is not just the temp of the exhaust, but the size of the flame. A bigger fire has more heat. EGT is just a measurement, a "snapshot" at a given place, but it does not measure the size of the flame. Which has more heat, a campfire or a bonfire that uses the same wood? In both cases, the "EGT" is the same. Only the size of the flame differs.

 

[carusoam]

39 minutes ago, GeeBee said:

No, the excess fuel continues to burn longer in the pipe. I used to play with the flame length at night in a Beech 18 when I got bored. Move the mixture rich, flame gets longer, move it lean, flame shortens. The combustion process does not end when the exhaust valve opens. Basically by running ROP you are "heating the pipes" with a longer exit flame. It is not just the temp of the exhaust, but the size of the flame. A bigger fire has more heat. EGT is just a measurement, a "snapshot" at a given place, but it does not measure the size of the flame. Which has more heat, a campfire or a bonfire that uses the same wood? In both cases, the "EGT" is the same. Only the size of the flame differs.

 

GB,

You’re making me think even harder… 

True for open ended exhaust pipes…. The excess fuel will certainly be converted… in a nicely visible way…

Operating in flaming dragon mode… will certainly show the flames exiting the short stacks….

 

LOP burns all of the gasoline leaving excess oxygen exiting the exhaust pipe…

ROP burns all of the oxygen leaving excess gasoline exiting the exhaust pipe…

Exhaust valves can’t stop the reaction once it has started…

Engine timing gets credit for starting the ignition cycle earlier or later…  the later the timing, and the more worn the ignition system… the more the flames will be visible exiting the exhaust stack…

 

I think I may have mixed up the thought process somewhere, or ran out of logic before I was done….   
 

With ROP…?

In real life….  Vs. flying 101…

Flying 101, magically has all the fuel converted 100%, before it gets to the exhaust valve… 

Somebody posted the complexities of the actual chemical reactions involved around here recently…

The rates of these reactions are also non-constant… leading to all kinds of results…

 

Where is Ross?  This is his kind of topic….   @Shadrach

Thanks! Great logic review… enjoyable conversation… 

Best regards,

-a-

 

[Shadrach]

1 hour ago, carusoam said:

GB,

You’re making me think even harder… 

True for open ended exhaust pipes…. The excess fuel will certainly be converted… in a nicely visible way…

Operating in flaming dragon mode… will certainly show the flames exiting the short stacks….

 

LOP burns all of the gasoline leaving excess oxygen exiting the exhaust pipe…

ROP burns all of the oxygen leaving excess gasoline exiting the exhaust pipe…

Exhaust valves can’t stop the reaction once it has started…

Engine timing gets credit for starting the ignition cycle earlier or later…  the later the timing, and the more worn the ignition system… the more the flames will be visible exiting the exhaust stack…

 

I think I may have mixed up the thought process somewhere, or ran out of logic before I was done….   
 

With ROP…?

In real life….  Vs. flying 101…

Flying 101, magically has all the fuel converted 100%, before it gets to the exhaust valve… 

Somebody posted the complexities of the actual chemical reactions involved around here recently…

The rates of these reactions are also non-constant… leading to all kinds of results…

 

Where is Ross?  This is his kind of topic….   @Shadrach

Thanks! Great logic review… enjoyable conversation… 

Best regards,

-a-

 

I’ve never experienced a lack of heat based on mixture setting in cruise. CHT may correlate to EGT and or heat exchanger temp in some cases but certainly not all. @GeeBee is talking about low compression radials (likely 6ish:1CR). They are not as thermally efficient as our higher compression flat engines. Most of the extra fuel when ROP does not burn as there is no O2 to support combustion. What GeeBee observed as a “bigger flame” was just a flame front that was moving so slowly that combustion was far from complete when the exhaust valve opened. This can be done lean or rich, it just requires a large enough surplus of air or fuel to slow the combustion event significantly (it’s why there is a second EGT rise on the lean side before the engine goes rough). 
 

I can see perhaps having heat issues with the throttle back on approach when the engine is producing very little horsepower and therefore very little surplus heat heat energy. I can see no reason why running 1420 (~30LOP for me) would produce less cabin heat than 1350 (100 ROP).  The claim really doesn’t make any sense to me at all. However, I don’t profess to know everything about everything… There may be something I haven’t thought of.

[GeeBee]

You cannot argue with results. ROP produces more cabin heat and higher CHT's because the pipes are hotter. Throw more BTU potential on the fire, you get a bigger fire. Done it myself many times. As to why? I'll leave that to the speculators.

 

 

 

[Shadrach]

4 hours ago, GeeBee said:

You cannot argue with results. ROP produces more cabin heat and higher CHT's because the pipes are hotter. Throw more BTU potential on the fire, you get a bigger fire. Done it myself many times. As to why? I'll leave that to the speculators.

 

 

 

Im not doubting results, just your theory.  Fuel needs oxygen to combust. Once each O2 molecule is paired with a fuel molecule any surplus of either fuel (ROP) or Air (LOP) only serves to increase  or decrease the speed of the combustion event. More fuel after that does not add “BTUs” unless you add additional O2 to ignite it. ROP produce higher CHTS because it produces higher peak pressure cylinder pressure closer to TDC. A turbo aeroengine @ 70% power can produce very different CHTs depending on the mixture setting.  If it was really “BTU Potential” then going full rich should really help support cabin heat. 

Edited November 29, 2021 by Shadrach

[GeeBee]

You are assuming all combustion occurs in the cylinder. The exhaust stroke just pushes the continuing combustion process out, it does not stop because the exhaust valve opens. Hight octane gas engine especially so since the combustion process is retarded to prevent detonation.

As for a turbo engine, now you are talking a whole different kettle of fish, because it depends on waste gate position. With it fully closed, a richer mixture will result in higher CHT's in large part because you are increasing mass flow across the turbine increasing the speed of the turbine and the temp of the intake air.

 

 

[MIm20c]

The Ovation can get cold especially for the back seat passengers when running LOP in the winter.  I’m in agreement with GB that 20ish ROP is helpful for putting extra heat where it’s needed when flying high. The engine creates more power so the added speed is nice as well. 

[PT20J]

The Mooney heat system is a simple thermodynamic heat exchanger. In order to properly analyze it, the mass flow of the cabin air and the exhaust gasses would need to be known as well as the inlet and outlet temperatures of the two fluids. The exhaust temperatures LOP and ROP aren’t much different and are vastly higher than the cabin air passing through the exchanger. So, any heat transfer difference LOP or ROP must be due to the different mass flow through the exhaust. 

Now, what I would really like to know is why the heating airflow on my J drops off significantly with the cowl flaps open. Someone postulated in another thread that the decreased pressure within the lower cowling draws more hot air out the firewall mounted heat diverter valve. But I checked mine, and when the heat is full on, the valve directs all heated airflow into the cabin snd blocks off the outlet to the engine compartment. Yet, with the cowl flaps open more than 1/2 the heated air flow at the bottom of the console drops off to nil with the heat full on and the vent air full off. Close the cowl flaps without touching the heat control and it blasts out very hot air. 

Skip

[N231BN]

The Mooney heat system is a simple thermodynamic heat exchanger. In order to properly analyze it, the mass flow of the cabin air and the exhaust gasses would need to be known as well as the inlet and outlet temperatures of the two fluids. The exhaust temperatures LOP and ROP aren’t much different and are vastly higher than the cabin air passing through the exchanger. So, any heat transfer difference LOP or ROP must be due to the different mass flow through the exhaust. 
Now, what I would really like to know is why the heating airflow on my J drops off significantly with the cowl flaps open. Someone postulated in another thread that the decreased pressure within the lower cowling draws more hot air out the firewall mounted heat diverter valve. But I checked mine, and when the heat is full on, the valve directs all heated airflow into the cabin snd blocks off the outlet to the engine compartment. Yet, with the cowl flaps open more than 1/2 the heated air flow at the bottom of the console drops off to nil with the heat full on and the vent air full off. Close the cowl flaps without touching the heat control and it blasts out very hot air. 
Skip

Skip,

The inlet for the cabin heat is on the rear engine baffle, when the cowl flaps close they increase the air pressure in the cowling as 201/231 cowl inlets are too large for the exit area.

I once adjusted my cowl flaps so they close tight and in flight I could see the top cowl bulge up as I closed the cowl flaps, way too much pressure.

[PT20J]

Agree that the inlets are too large (Lopresti did better on his second try ).

But my hot air intake is just inside the left cowling intake next to the air filter. Agree though that the pressure distribution must change so less flows into the inlet. It’s just not obvious.

Skip

[Will.iam]

4 hours ago, GeeBee said:

You are assuming all combustion occurs in the cylinder. The exhaust stroke just pushes the continuing combustion process out, it does not stop because the exhaust valve opens. Hight octane gas engine especially so since the combustion process is retarded to prevent detonation.

As for a turbo engine, now you are talking a whole different kettle of fish, because it depends on waste gate position. With it fully closed, a richer mixture will result in higher CHT's in large part because you are increasing mass flow across the turbine increasing the speed of the turbine and the temp of the intake air.

 

 

In my turbo ROP definitely cooler temps to the TIT which is a proxy of what the EGT’s are where as LOP I have to either go deeper LOP, slow the RPM’s so that more of the combustion finishes in the cylinder instead of going out the exhaust as the flame front is slower or lower the power.

[Shadrach]

10 hours ago, GeeBee said:

You are assuming all combustion occurs in the cylinder. The exhaust stroke just pushes the continuing combustion process out, it does not stop because the exhaust valve opens. Hight octane gas engine especially so since the combustion process is retarded to prevent detonation.

As for a turbo engine, now you are talking a whole different kettle of fish, because it depends on waste gate position. With it fully closed, a richer mixture will result in higher CHT's in large part because you are increasing mass flow across the turbine increasing the speed of the turbine and the temp of the intake air.

 

 

I’m assuming no such thing when it comes to the combustion event and stated just the opposite in my post.

As to your second paragraph, let’s start with “richer mixture”. What is a “richer mixture”? Relative to what? 

 

 

 

Edited November 29, 2021 by Shadrach

[GeeBee]

It does not matter what "richer" is "relative to," it only matters that the mass flow across the turbo is increased. An increase in fuel mass has a dramatic effect upon turbo speed. Ask all the diesel operators why their mileage dropped 15% when ultra low sulphur fuel was mandated. Reason, the fuel mass per gallon decreased and so did turbine speed. Turbo's are highly sensitive to mass flow, especially when the waste gate is closed or a fixed gate design.

[N231BN]

Agree that the inlets are too large (Lopresti did better on his second try ).
But my hot air intake is just inside the left cowling intake next to the air filter. Agree though that the pressure distribution must change so less flows into the inlet. It’s just not obvious.
Skip

I forgot the 201 has the inlet up front. With that kind of pressure increase into the heater you can see why the ram air door offers so little improvement in the 201.

[Shadrach]

9 hours ago, PT20J said:

Agree that the inlets are too large (Lopresti did better on his second try ).

But my hot air intake is just inside the left cowling intake next to the air filter. Agree though that the pressure distribution must change so less flows into the inlet. It’s just not obvious.

Skip

Do you see a change in MP when the cowl flaps are closed?

[201er]

16 hours ago, GeeBee said:

You cannot argue with results. ROP produces more cabin heat and higher CHT's because the pipes are hotter. Throw more BTU potential on the fire, you get a bigger fire. Done it myself many times. As to why? I'll leave that to the speculators.

I don't think ROP can produce more BTU than Peak EGT. There may be extra fuel, but there sure isn't extra oxygen to allow it to combust. So if anything, that extra fuel at ROP is providing cooling by being in the mix

[PT20J]

27 minutes ago, Shadrach said:

Do you see a change in MP when the cowl flaps are closed?

No.

Does you F have a similar effect? Where is the heat duct are intake on an F?

Skip

[Shadrach]

3 hours ago, GeeBee said:

It does not matter what "richer" is "relative to," it only matters that the mass flow across the turbo is increased. An increase in fuel mass has a dramatic effect upon turbo speed. Ask all the diesel operators why their mileage dropped 15% when ultra low sulphur fuel was mandated. Reason, the fuel mass per gallon decreased and so did turbine speed. Turbo's are highly sensitive to mass flow, especially when the waste gate is closed or a fixed gate design.

Perhaps I am misunderstanding.  It seems to me that "relative to" is indeed important. It also seems that you're suggesting that CHTs, EGTs and mass airflow to the turbo all increase as the mixture is enrichened from apparently anywhere on the useable mixture setting spectrum.  I believe this to be demonstrably false.  If you think "throwing more BTU potential" at your exhaust is a thing even in the absence of O2 to combust that BTU potential, have at it...  I will continue to believe that cabin heat availability is a function of the waste energy down stream of the cylinders and the heat exchanges ability to transfer it to the cabin.

Edited November 29, 2021 by Shadrach

[Shadrach]

22 minutes ago, PT20J said:

No.

Does you F have a similar effect? Where is the heat duct are intake on an F?

Skip

Both heat and vent seem to be constant regardless of cowl flap position. Heat inlet is on the forward pilot side cylinder baffle assembly. I have yet to encounter a scenario where the heater was inadequate.  Prior to insulating the cabin, it was impossible to distribute comfortably in really cold weather. Keeping rear passengers warm in sub freezing temps meant cooking the front seaters.  It's much better since insulating. If there is a weak spot it is the rear seat foot wells.  I've often pondered ways to fabricate an under seat rear passenger foot duct. 

 

Edited November 29, 2021 by Shadrach

[PT20J]

Ross @Shadrach, here’s the setup on the J. The main difference seems to be the location of the intake relative to the cowling opening.

[GeeBee]

5 hours ago, Shadrach said:

Perhaps I am misunderstanding.  It seems to me that "relative to" is indeed important. It also seems that you're suggesting that CHTs, EGTs and mass airflow to the turbo all increase as the mixture is enrichened from apparently anywhere on the useable mixture setting spectrum.  I believe this to be demonstrably false.  If you think "throwing more BTU potential" at your exhaust is a thing even in the absence of O2 to combust that BTU potential, have at it...  I will continue to believe that cabin heat availability is a function of the waste energy down stream of the cylinders and the heat exchanges ability to transfer it to the cabin.

When the waste gate is closed, the turbo acts like a turbine engine without combustion cans because the combustion takes place in the ICE. How do you accelerate a turbine engine? Increase the fuel flow. It is that simple, you throw more fuel at it and it accelerates because the mass flow picks up. Forget BTUs, forget TIT, forget EGT, all those are parameters to be observed for sure, but when the waste gate is closed, turbine speed is controlled by mass flow and mass flow alone. If for instance you increase prop rpm, the MP will go up, not down, why? Mass flow increase accelerates the turbine. The Cessna T210 POH has a nice section on this aspect and if you flown high enough to have the waste gate fully closed, you will find decreasing fuel flow with the mixture will slow the turbo (and thus MP) and increasing fuel flow will increase the fuel flow.

Ever see those guys with diesels pouring out black smoke after "chipping" their engine? What is happening there? They have boosted the MP by accelerating the turbo with more fuel, a lot of fuel, enough to make black smoke. It is all about mass through the turbine.

[Shadrach]

38 minutes ago, GeeBee said:

When the waste gate is closed, the turbo acts like a turbine engine without combustion cans because the combustion takes place in the ICE. How do you accelerate a turbine engine? Increase the fuel flow. It is that simple, you throw more fuel at it and it accelerates because the mass flow picks up. Forget BTUs, forget TIT, forget EGT, all those are parameters to be observed for sure, but when the waste gate is closed, turbine speed is controlled by mass flow and mass flow alone. If for instance you increase prop rpm, the MP will go up, not down, why? Mass flow increase accelerates the turbine. The Cessna T210 POH has a nice section on this aspect and if you flown high enough to have the waste gate fully closed, you will find decreasing fuel flow with the mixture will slow the turbo (and thus MP) and increasing fuel flow will increase the fuel flow.

Ever see those guys with diesels pouring out black smoke after "chipping" their engine? What is happening there? They have boosted the MP by accelerating the turbo with more fuel, a lot of fuel, enough to make black smoke. It is all about mass through the turbine.

So to be clear, you are saying that "richer mixtures" continue to burn in the exhaust manifold which increases pressure/mass air flow across the turbine yet generate lower TIT readings? 

[GeeBee]

 No, does not matter if it burns or not. Its all about mass. Which water wheel goes faster, the one with a trickle or a full stream?

[N201MKTurbo]

19 hours ago, PT20J said:

The Mooney heat system is a simple thermodynamic heat exchanger. In order to properly analyze it, the mass flow of the cabin air and the exhaust gasses would need to be known as well as the inlet and outlet temperatures of the two fluids. The exhaust temperatures LOP and ROP aren’t much different and are vastly higher than the cabin air passing through the exchanger. So, any heat transfer difference LOP or ROP must be due to the different mass flow through the exhaust. 

Now, what I would really like to know is why the heating airflow on my J drops off significantly with the cowl flaps open. Someone postulated in another thread that the decreased pressure within the lower cowling draws more hot air out the firewall mounted heat diverter valve. But I checked mine, and when the heat is full on, the valve directs all heated airflow into the cabin snd blocks off the outlet to the engine compartment. Yet, with the cowl flaps open more than 1/2 the heated air flow at the bottom of the console drops off to nil with the heat full on and the vent air full off. Close the cowl flaps without touching the heat control and it blasts out very hot air. 

Skip

Skip,

It may have to do with the airflow in the cowl cooling the outside of the heat muff. With the flaps closed it slows the airflow around the outside of the muff and also increases the lower cowl temperature from the cylinder heat.

Putting some header wrap tape around your muff may eliminate the effect.

 

Is it Muff or Cuff? I like Muff....

Edited November 29, 2021 by N201MKTurbo