Effect of volume displacing cable in fuel vaporizer on fuel temperature

Hello,

I am replacing the cable in my Stanley's fuel vaporizer and wanted thoughts on the effect of cable length and diameter on steady state fuel temperature.

My vaporizer is made of 1/4" Schedule 80 pipe with an ID of about 0.300" The cable I removed was a 7x19 stranded with an OD of 3/16" I am tempted to increase the diameter of the cable. I never had any issues with the cable getting stuck, but have had some carbon buildup at my jets on occasion and am considering lowering my fuel temp. I am pretty sure the following will occur if I go to a larger OD cable:

1) Displacing more volume will speed up transients / reduce the time between fuel automatic closing and the flow stops coming out of the jets. I see no negative to this.

2) Increasing the cable diameter will provide a larger heat sink. When the steam automatic closes and the fire shuts off the larger mass cable will retain more energy for the next time the automatic turns fuel flow back on and should get things vaporizing quicker. This also seems like a good thing.

3) Increasing the cable diameter will make it more likely to get stuck - This sucks but I have never even had a tight cable, let alone be close to getting it stuck. I am thinking of moving from 3/16" diameter cable to 7/32" diameter so I think I still have plenty of room to the 0.300" ID of the vaporizer to not get stuck.


My Question:

Would we expect the output fuel at the jets to have a higher or lower temperature as the cable gets larger?

My thoughts - The volumetric fuel flow rate is set by the jet orifice size and fuel pressure. The volumetric flow rate shouldn't change as I increase the cable diameter provided it is not posing a larger restriction than the orifice. However, the velocity of the fuel flowing through the vaporizer should increase as I displace more volume with the larger diameter cable. (A given volumetric flow fate flowing through a fat tube will have a lower linear velocity than flowing through a tube of small cross sectional area) I believe the fuell will therefore have less time in the heat of the fire which leads me to believe it will pick up less energy / be cooler. That said - when I spoke with a Staley person I trust who has years of steaming under his belt, he believed a larger cable would increase fuel temperatures. I may just run an experiment monitoring fuel temp with a cable and without to understand the change, but am curious if anyone has already done so?

Thanks!
-Joe

Hi Joe,

While not always true, the rule of thumb for boilers is that the rate of heat transfer increases as you increase flow velocity. While the argument that it has more time to pick up heat sounds good, there is also the matter of faster flow being more turbulent and therefore having better contact with the tube surface. This is especially true if vapor bubbles are forming on the tube surface, they can act as an insulating layer and the more you can scour them loose with the liquid flow, the better the heating. I assume this holds true for vaporizers as well as boilers.

Ken

Hi Joe,
Interesting question and one I have thought about significantly with regard to boiler design. I have a technical presentation that I was prepared to give at the last SACA Meet and didn't have a chance. Some of the slides relate to your very question(s). The slides pertain to generating steam from water. However, the heat transfer concept also applies to petrol fuel.

First slide points out that when reducing the cross sectional area, the required pump or pumping power needs to increase to maintain the same fuel/flow rate. My assumption is that you're using 120 PSI fuel pressure or close to it? If not, I would recommend it to maintain your current BTU/hr.

Second slide provides empirical evidence that your fuel temperature will be hotter. Also, note that fuel density changes with temperature. Flow rate is a function of density. The info came from the internet and treat it as a comparison to show that heat transfer is exponential with increase in flow. This also results in increase turbulent flow, higher Reynolds Number, that maximizes heat transfer. My opinion, this will help to reduce carbon build up also.

Third slide provides my concept for boundary layer and heat transfer efficiency. Fill allows one to achieve faster flow with larger surface area from the generating tube/pipe.

As a last note, I wonder if this will improve or hinder any howling from the burner. I would recommend trial and keep in mind the pressure needed to maintain flow. There are many other variables involved and recommend concept validation as opposed to empirical validation. As I mentioned the temperature effect on fluid density, this is one of the main reasons that it is very difficult to design a generating tube.

Please let us know how you make out?

Kind regards,
Rick



Edited 1 time(s). Last edit at 04/06/2022 07:16AM by Rick.H.

Joe
I do not have the years of running time a lot of Stanley owners do but I have repaired and built many burners, both condensing and non condensing burners.
I have repaired and rebuilt vaporizing tubes on different Stanley’s and Locomobile’s.
I have found mutable problems.

You did not say what year the Stanley was. Is it a long spiral wound vaporizing tube as on condensing cars or straight tubes as on non condensing cars.

Most problems are the pilots are running two hot on non condensing cars.
A lot are just the fact the pilot tubes are just two close to the burner or pilot burner. I first make new tubes mounted as high as I can above the pilot burner on non condensing cars.
On condensing cars the vaporizing tube can be raised higher or lower off the plate.

Another problem I have found is people just go and buy 3/16 cable or SS cable with out knowing what to ask for. A lot of Cables are made with fiber fillers, that’s not good. You want fiber free 3/16 aircraft cable.

A lot of burners problems are carbon build up in the tube where you just can’t remove the cable, or pass enough fuel.

I always bought my cable from the supplier that makes the sling for my cranes and hoisting equipment, and can supply mill certification sheets.

It’s ease enough to change out the cable go for it, you can always go back to 3/16

Rolly

The car is a 1923 740. It has a single looped vaporizer that heads to the branch forks. I have both 3/16" and 7/32" cable so I will make them both up. I like the idea of displacing as much volume as possible for transients.

Not sure what, if any, effect it will have on the fuel temp at the jet. I think I will just run a test with and without a cable to see which way the temperature trends. I can make arguments for both ways - best to just find out for sure.

-Joe

It has been my experience that the 740 and 750 had slotted burner plates. They tend to run higher fuel pressure then the 735. depending on slot width. Do you have a slotted burner? And what fuel pressure are you running?
Rolly

I run a slotted (Baker style) burner. I am always playing with fuel pressures and orrifice size to get max power and not howl. Last year I finished up with a #57 Jet at 140 PSI.

-Joe

I have not played with Backer slotted burners for over 25 years now. I sold my 1920 and now only have my EX with a drilled burner.

I have made my own patterns for flat plate burners and cast them in Ductile iron 85-55-06, Cumberland foundry in Rhode Island does the nicest job. I have not found any hard spots drilling or slotting there castings.

I have found slotted Backer type burners to be a problem, most are cast very thin and the slots are cut much two wide, 0.025 to 0.035, with out high pressure as your using the flame can drop through. The air tubes are two small and the tube wall thickness two thin making them holler. I cast a few with 0.250 plat thickness and some thicker and keeping the slots 0.020 never had the flame drop through.

Rolly

The speed of mixture flow through the burner plate holes/slots must be greater than the speed of advance of the flame front downwards into the holes - seems like simple physics - if only I knew what that was.

Hole/slot diameter/width and thickness of plate and burner pressure control the rate of gas flow.

Mike

Joe, Mike & Rolly,
After hearing your responses, I wonder if the slotted area in the cast burner plate exceeds the area of the fire tubes in the boiler. I know a lot of car and other vehicle owners have fired their burners in atmosphere (not under the boiler, fire tubes). The flames will scream. When back under, in position, the flames are lazy. It gets less lazy after the boiler heats up. Interesting observation.

EX car (non-condensing) exhaust pulls burner exhaust gas through the boiler. A condensing car doesn't seem to have that feature.

Another question is does the radiator on a condensing car pull enough vacuum to overcome the lack of the exhaust draw feature. Joe, you're not the first person I've heard of who plays with fuel pressure and nozzle orifice size (jet) on a condensing car or any car trying to improve flow through the boiler fire tubes.

Last question on the howling, I initially thought that the gases exceed the speed of sound to make the noise. After some research, the gasses do not...I stand corrected. A lot to learn about these cars and fun doing it. Part of the research was re-watching Jay Leno you tube video on his Stanley Vanderbilt. He made nice fun of the howling with a wolf howl impression. The question is if one increases the fuel press/jet to exceed the flow ability of the fire tubes, does this set up the natural frequency of the mixing tube to create the howl. Especially when the fire tubes are cooler and not up to temp.

Rick

Rick I’m not sure just how to answer your questions. I’m not sure I have the correct answers.
If you want to burn more fuel then the burner was designed for you need more air.
The condensing cars the exhaust duct goes down behind the boiler. The angle of the duct on the bottom creates a vacuum on the exhaust if it’s cut right depending on the speed.

Another question is does the radiator on a condensing car pull enough vacuum to overcome the lack of the exhaust draw feature.
First it’s not a radiator. It’s a condenser. And I have never tested it with a vacuum gauge when I had my 1920 Stanley, but I do not believe it dose, I think there is back pressure. Most seams to collect a lot of oil. I had an oil drain system on my 1920. I know some have oil separators before the condenser.

On the howling issue, I have road with Brent Campbell in his 30 HP cars at 70 MPH no howling. One day we were on a country park road 30 mph road near his house in Mass doing 70 MPH no windshield on Big Red I was trying to keep an eye on the pressure gauge to see if it dropped it didn’t. all I asked Brent was if he ever rolled the tires off the rims. He answered not on this car.

On two burner plates I made patterns for I increased the radius on the bottom of the casting pattern to get larger air tubes in. this was experiential as I did not know just how much more air would pass through the larger tubes, or how to calculate the answers.
One was for my 1920 the other was for my 1906 EX. My EX does not howl and on a few occasions on a flat road I have healed 50 MPH with out dropping pressure. Not good for the engine or the car made for 15 MPH. But lots of fun.

Years ago a friend of mine repaired Trumpets Trombones and other brass interments, he said if you change the brass thickness anywhere you change the sound. Same for any air passing through a tube.

I used heaver wall thickness on the air tubes in my burners. Was that the answer or was the larger tube diameter allowing more air at a slower speed moving through?

Rolly

I designed and built the new gear box on Brent’s Ray Stanley Special to drive an alternator.

I made a video clip of starting the burner on my H5 fired off the boiler.
Unfortunately It's too big to post on here but it does prove that the howl is in the burner and not in the fire tubes of the boiler.

The howling seems to be associated with yellow flames but dies down once the fire has stabilised. I suspect the improved vapourisation once the pilot is hot helps drag more air in than when the pilot is still a bit cool, causing a faster air flow and stopping the fire sneaking back down the holes.

I once tried putting a shield in front of the air intakes after experiencing a strong backfire when travelling fast. All it did was to make the burner howl, even when stationary - evidently again due to slower air flow.

Mike

Another way to improve the air flow through the burner and amount the air tube can handle is to add Venturi’s to the mouth of the air tubes.

Passing air or gas down a tube, the volume and speed tend to concentrate in the center of the tube. A Venturi allows more gas to flow moving to fill the tube airier allowing slower speed and more volume or increasing the speed with more volume depending on the demand.

Not only did I increase tube diameter bur added Venturi’s to my burners.

Rolly

There was a long debate about this on the Steam Car Club of GB forum in 2010 - I posted this comment at that time which adds to what I said yesterday about flames and so on. There seemed to be a general conclusion that the howling occurs in the mixing tubes. There are a couple of pages of debate still online on that site. Unfortunately the video which I hoped would still be there, has disappeared.

Thus was my comment:-

---------------------------

"The resonance is in the mixing tubes and the mixing chamber rather in the boiler pipes.

The resonance is set off by high frequency vibration of the flame which is trying to burn back down through the holes in the burner plate against the flow of gas, gets so far, goes out and is pushed back up by the gas. Initially this flame vibration is random over all the 6 or 7000 flame holes but in the right conditions when by chance enough flames are trying to push the gas back at the same time this causes a minor hiccup in the total gas flow through the venturis - a pulse if you like. If the frequency of this pulse matches the natural resonant frequency of the mixing tubes (which is matter of physics and determined by the length of the tube) a wave of pressure is set up in the mixing tubes which has the effect of synchronising all the flame pulses together across the entire burner, augmenting the pulses in the mixing tubes and howling away.

Anything which alters the rate of gas flow will change the howling frequency by altering the battle between the flame going down inside the plate and the gas going up. This is why putting the boiler on top or putting in bigger jets or higher fuel pressure makes a difference. The degree of fuel vaporisation also matters as this too changes the flame properties. If Jeff manages to get my video up you can actually see that when the burner is howling there are tiny flashes of yellow among the generally clear flame which I suspect are globlets of unvaporised fuel which have got through the burner plate hole as liquid and so have a local shortage of oxygen as they burn. That must be why a cold burner howls more than a hot one. There is also the possibility that the well known propensity of paraffin to cause more howling than petrol is due to a difference in the speed of the flame front as it tries to go down the burner holes.

It's a very interesting subject!

Edited to add

Think of it as a trombone - the flames are the player's lips making a vibration while the mixing tubes are the slide and flared cone in which the vibration resonates. There is a further point - howling can warble, going up an octave and back down - this is known to the musician as overblowing which has just the same result."

--------------------------------

Mike



Edited 1 time(s). Last edit at 04/12/2022 02:34PM by Mike Clark.

I have original drawings and photographs of the original insides of the Backer burner showing the air tubes and deflection plated. Why there not with the attached photos I can’t say.
These are photos of a Backer boiler and burner.

Rolly

this is a post from the late Pat Farrell.

Baker Burner Howl
Posted by: SSsssteamer (Moderator)
Date: August 26, 2009 10:51PM

For the last 20 years, rather than the Stanley burners, I have been running Baker Burners in my Stanleys. The Bakers are supposed to give you more heat than a Stanley burner. But, the Bakers also give you more of a howl. My burner pan on my 1916 Stanley Mt Wagon burned out in the back where the super heater passes through. I shortend the 30 hp Baker burner pan up by about two inches. The wall above the grate went from about 5.5", down to about 3.5 inches high. The critter howls so bad now that I can hardly stand it. Before, once it got hot, it hardly howled at all. On my 1914 Stanley, after about 20 years of rust and heat, the burner pan wasn't worth trying to fix it for the extra holes that had rusted and burned through its pan. I made a new burner pan out of 20 gauge 310 Stainless steel that is good up to about 2100 degrees F and it is also rust proof. I raised the burner wall by 1/2" inch. It went from about 4" to about 4 1/2" tall above the burner grate. Before the burner howled more than it should. Now it doesn't howl except only when firing up. No one has ever mentioned that a deeper burner pan reduces burner howl. Apparently the depth of the burner pan is directly related to the amount of howl that the Baker burner will make. I also lengthened my super heater from 6 feet to about 10 feet and it made a lot of difference too. Now it has noticably more power on the hard hills. My super heater is made out of 1/2" schedule 40 stainless steel pipe. I found that I got a smoother bend by bending the pipe cold than by putting heat to it. I used a re-bar bender to do my bending. My pattern is a zig-zag with 4 runs. It fit just right in my 23" diameter burner. I have followed the Stanley directions by finally mounting the super heater firmly to the boiler retaining ring. By leaving it unsecured to rattle about, that is what runined both of my burner pans.


Rolly

I finely found my file and photos and drawing of the original baker burner pan and air tube layout. I have these in Cad drawings as well as in PDF format. They were on a memory stick files from one of my old computers.
I have another paper on the way sound is generated in the air tubes posted on the forum years ago by a musical guy. It is also on one of my old memory stick files somewhere.

Rolly

Quote
Rick.H
Another question is does the radiator on a condensing car pull enough vacuum to overcome the lack of the exhaust draw feature.

Sorry, this was a brain fart. On a condensing steam car, the radiator or condenser pulls the steam exhaust from the engine (in theory at least). The concept I was exploring if it could pull the burner exhaust. Probably not gonna work. I was thinking too far ahead...the following is my distraction.

I have wondered if a device like a turbo charger put into a condensing Stanley will make a difference? The configuration would be such that the turbine (sometimes call buckets) would be in the engine, steam exhaust area getting energy from the steam flow. Then the compressor would be in the burner hot gas exhaust after the boiler to help draw through the fire tubes. I cannot verify but think this is what Doble did when developing his last car, the F. Jim Crank's book eludes to this concept. I think this concept would eliminate howling from a Baker Burner.

Mike and Rolly, I totally agree with your concepts regarding howling along with the late Pat Farrell's information...fun evaluation.

Rick

David Nergaard SACA-NE has a route blower mounted on top of his boiler. Exhaust steam drives the blower (adds a little back pressure on the engine) he also runs a oil separator on the exhaust steam line, to turn a fan to help out the condenser, if I remember correctly from the SACA-NE newsletter he gets 186 miles out of a tank of water. I road from RI to Connecticut and back again, around 100 miles and we added no water on that trip. I believe he has written it up in the Bulletin as well.

Rolly

Rolly,

I'm familiar with Nergaard's blower modification. My thought is to drive a fan to draw exhaust gas, not a condenser fan. Thank you for the reference.

Not that condensing is not important, just better to improve boiler heat transfer...go faster!

Picture with Dave and me at Canandaigua, NY a few years back.

Thanks,
Rick

Maybe I’m having a senior moment hear but a good condenser can draw a 29.5 inch vacuum on the low pressure cylinder. My Steamboat Tryall vacuum gauge read close to 30 inches. All the time. Steam collapsing back to water is great stuff.

Or are you referring to boiler flue exhaust gas. ???? trying to improve combustion chamber pressure. In a good wind over the stack my wood burning boiler in my 25 foot boat would really cook. My late friend Rod Teel (a SACA Member) and I came across lake Winnipesaukee in a heavy blow, half the front of the boat was standing out of the water. We were going as fast as it ever had. What a ride. I was burning hard wood as fast as I could feed the boiler. He was steering.

Rolly

Sorry Rolly,
I should clarify:

Exhaust gas is from fuel combustion. Better to improve the flow of the hot, burnt gas through the boiler quicker than...

Steam exhaust from the engine to the condenser (condensing Stanley) Than improve the condenser performance with a roots blower driving a radiator fan.

My suggestion is to use the roots blower (Dave Nergaard's sys) to drive a compressor in the hot gas path. My opinion...

Beautiful picture of the boat!

Very best,
Rick

Most oil fired fuel air blower or vaporized burners don’t really need much help unless there is long exhaust duck or lots of small tubes in the boiler. Small tubes are not the best design, keeping the boundary layer wet is where the heat transfer takes place A lot of this has to do with proper flue configuration and size with combustion gases. True boiler tube design and gas flow is a science; you just don’t calculate for heat transfer.
I have spent hours calculating boiler design on two ASME code boilers I had approved by Hartford boiler insurance. The only thing I had problems with was plate thickness on ligament spacing plate thickness and flat plate deflection on a round plate, you need trig. Never had it in school, took me a while to figure it out. The other thing that effects plate thickness is if you have a tapped plug hole, the plate must have five full threads for the plug used. Code.

The non condensing Stanley used the engine exhaust into the exhaust duck, but a hole and flap was cut into the other end to adjust just how much the exhaust actually pulled on the burner. My EX the hole is mostly opened. I have seen other cars that have had fires start in the exhaust duct. In fact I was a guest in a no condensing car the so much engine oil had collected under the car when stopped at a light, a car stopped nested to us and asked if the under side of the car was supposed to be on fire. It took all three fire extinguishers to put out the fire. This duct should be blown out with a steam lance ever now and then.

Rolly

Hopes this helps some what.

Hi Rolly,
You peaked my interest,

Quote
Rolly
The non condensing Stanley used the engine exhaust into the exhaust duck, but a hole and flap was cut into the other end to adjust just how much the exhaust actually pulled on the burner. My EX the hole is mostly opened.

Please explain this configuration?

Thanks,
Rick

Rick I hope these photos are self explanatory.

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27-Flash vs Mono Tube Design.png	223 KB	open | download	Rick.H	04/06/2022	Read message
28-Heat Transfer Coefficient.png	81.5 KB	open | download	Rick.H	04/06/2022	Read message
35-Mono Tube to Drum.jpg	609 KB	open | download	Rick.H	04/06/2022	Read message
Burner casting pattern.JPG	166.9 KB	open | download	Rolly	04/08/2022	Read message
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