Better fuel efficiency through vapor carburators?

[lamar]

I'm sure everybody has heard all the stories about high mileage carburators and the oil companies etc. But why has this problem not been solved? Approximately two thirds of the fuel we burn in our cars goes out the tail pipe. I've read that someone has used catalytic cracking to breakdown the fuel into a more user friendly vapor and got incredible mileage. Naturally I'm a bit of a sceptic but I'd like to hear what people have to say about the idea.

 

[Cliff_J]

The fuel delivery and combustion process aren't the issue so much as the design of the ICE itself.

The design of the diesel ICE offers better efficiency with its higher compression ratio to create higher average cylinder pressures and slower burning fuel to allow longer periods of high cylinder pressure, but still loses plenty of BTUs out the tailpipe and into the cooling system.

I think its a lost cause to search for better efficiency with the fuel itself like trying to gain aerodynamic efficiency by changing the type of carpet used on the floor of the car. But hey, I enjoy paying $$$ at the pump - NOT!

A high-output and cheap to manufacture fuel cell would double our efficiency instantly even from the existing fuel sources, and allow further flexibility into others. That's the answer, IMHO anyways.

Cliff

 

[Michael D. Sewell]

1.) ALL of the fuel I burn in my car goes out the tailpipe.
2.) Almost all of the fuel I put in my tank gets burned.
3.) I can prove it.
4.) So can you.

 

[faust9]

Originally posted by lamar
I'm sure everybody has heard all the stories about high mileage carburators and the oil companies etc. But why has this problem not been solved? Approximately two thirds of the fuel we burn in our cars goes out the tail pipe. I've read that someone has used catalytic cracking to breakdown the fuel into a more user friendly vapor and got incredible mileage. Naturally I'm a bit of a sceptic but I'd like to hear what people have to say about the idea.

This sounds like a "hoakey" explanation of EGR. EGR shows a minimal improvements in milage but it doesn't do it by altering the exhaust gasses into some magical vapor. Moreover, combustion is an oxidation process--how much energy would be required to reverse that process? Answer: A significant amount (more than required for the original reaction). Where is this extra energy coming from?

High milage carbs are around and fairly easy to manufacture. The problems associated with these are power and emissions.

 

[Michael D. Sewell]

All around the globe are thousands of racing teams who spend every waking moment thinking about how to get an extra horsepower out of an engine, and how to get a tenth of a mile per gallon more on their fuel mileage. At the same time, there are tens of thousands of mechanical engineers working for automobile manufacturers(maybe the most competitive industry in the world) who would dearly love to get any possible edge on the competition. A lot of people would have you believe that it has never dawned on any of these engineers to improve the efficiency of their products. What do you think these engineers do all day?

 

[russ_watters]

Originally posted by Michael D. Sewell
All around the globe are thousands of racing teams who spend every waking moment thinking about how to get an extra horsepower out of an engine, and how to get a tenth of a mile per gallon more on their fuel mileage. At the same time, there are tens of thousands of mechanical engineers working for automobile manufacturers(maybe the most competitive industry in the world) who would dearly love to get any possible edge on the competition. A lot of people would have you believe that it has never dawned on any of these engineers to improve the efficiency of their products. What do you think these engineers do all day?

Well put.

Lamar, there are certain fundamental restrictions on the efficiency of internal combustion engines. It is extrordinarily difficult to get an otto cycle engine above about 35% and the efficiency is directly related to compression ratio as you can see from THE EFFECIENCY EQUATIONS. Compression ratio is why the diesel cycle (similar to, but not exactly the same as the otto cycle) is a fair amount more efficient than the otto cycle.

One thing not talked much about though is tighter computer control over the combustion process. Its really not that expensive and though it only adds a few percent to the efficiency, it reduces the nastier emissions by a considerable amount.

 

[Ivan Seeking]

Since higher compression ratio's also produce more NOX's, two different environmental concerns come into conflict with each other here - efficiency and NOX pollution. I assume that we are forced to seek the middle ground on this point.

Does anyone know how efficiently the fuel is atomized in modern fuel injection systems as compared to the theoretical ideal, and to what degree does this impact the final fuel efficiency?

My preferred solution: Go Hydrogen.
https://www.physicsforums.com/showthread.php?s=&threadid=4127

 

[Cliff_J]

The lean burning of H2 in an IC engine with a high compression ratio (to give us high efficiency) will still result in the production of NOx. Given that H2 used on an existing ICE will suffer a 15% decrease in power output, it won't be until the technology of direct injection makes it way from the lab to a production line that we'll see a 15% increase in power output compared to a gasoline engine. Not bad, lots of promise once the compromise over higher efficiency of fuel spent/NOx produced is optimized.

Also, there are researchers working on devices to reduce NOX emissions by 90% or better via a fuel powered chemical scrubber. They are retrofitting this device to existing ICE engines like on a bus to cut down on its output, same could easily be applied to an H2 vehicle espcially since the size could be much smaller. I don't remember the details, but it was on a science channel show like 'TechKnowledge' or one like it.

I've also read of a place that uses a metal hydride as the storage mechanism for H2, offering a greater density per volume than even liquid H2. It is low pressure and should the container become ruptured its not flammable even if in direct contact with a flame. It suffers from high cost and is can be easily destroyed by exposure to components in regular air. Some place was using in a Corvette they retrofitted to run on H2. I'll see if I can dig up some links.

Cliff

 

[Cliff_J]

Here's a couple relevant to what I posted:
http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/pdfs/fcm03r0.pdf
http://www.unitednuclear.com/h2.htm

Also, why no support for E85 and biodiesel as interim fuels that can readily replace fossil fuels and utilize the same infrastructure? They definitely would be accepted with open arms from our shrinking agriculture industry, reduce our dependence on foreign oil, and require no expensive fuel cells or public education about the safety of H2. Instant green IMHO.

Cliff

 

[Ivan Seeking]

Great links! Thanks.

Again, if anyone is interested in this - Hydrogen powered cars, and a Hydrogen Economy in general - please see the link that I provided.

https://www.physicsforums.com/showthread.php?s=&threadid=4127

There are many other good links contained within the thread. I feel that H2 cars, and H2 production generally are some of the most important emerging technologies. As for options like biodiesel, in principle I support anything that could help reduce our need for oil, but I also feel that we need a coordinated effort to get hydrogen off the ground...so to speak. In this sense I prefer to see a focused effort for H2. As for E85, there seems to be a lot of problems with cars that run this stuff. At the least I have heard such talk from technical people. I'm not sure of any specifics. I know that home produced ethanol for farms has or had [at least] really taken off. In the long run though, I worry about the implicit wisdom of putting food in competition with energy.

 

[Freddie]

To: Lamar
Why has the problem not been solved? Goood question! Answer: (A) You pay for all the unburned fuel going out the tailpipe. (B)This represents positive cash flow for refiners and petroleum companies. (C) They get very upset at people who want to increase fuel efficiencies by factors of 2, 3. 5, etc. (D) What happens to good hearted people who want to cut BIG OILs cash flow by factors of 2, 3, 5, etc? In the 1920s a lot of work was done to improve gasoline mileage. For some strange reason, it is very difficult to locate records of this work. On the Internet, "This page is not available" comes up many times. I wonder why? Nevertheless, there is a lot of valuable information on the internet. It will just never be implemented in the United States. Think perhaps China, Russia, India, etc. Good luck.
Freddie

 

[megashawn]

Ok, hopefully no one will beat me up.

I had heard that buy running your fuel through a copper tube, and wrapping this tube around the heater core water line will heat the fuel, causing it to expand, thereby burning it more effiecently. I don't know the technical reasons why.

Anyhow, something similar to this is used with propane conversions, where they use hot water from the cooling system to expand the propane before it is fed to the engine.

 

[Freddie]

Megashawn: No one will beat you up. But, if there was a whiff of publicity re large capital investment to commercialize, Poof - you would vanish!
If you have droplets of fuel, the droplets cannot vaporize and burn in the short time available in the cylinder. So maybe a little of the outer layer of the droplet vaporizes and burns and the rest goes out the exhaust to heat your catalytic converter. Vaporizing fuel was the basis for many improvements. Your reference to propane vaporization is astute.
The big jump in fuel economy is the introduction of water vapor into the cylinder to:
1. Lower peak temperatures thereby reducing heat losses.
2. Extending the time during which cylinder pressure is relatively high. This is significant because high pressure early in the cycle does very little while moderate pressure when the crank is at 90 degrees does a lot.Vizualize a sine curve.
I read a reference which stuck with me but I cannot relocate, but the reference was to an Oldsmobile 88 idling at 80 rpm. Typical "normal" idle speeds are about 500 rpm and up. My personal belief was that this was an example of water vapor introduction.
There are many references on the Internet which can be found, also many books available giving more details on specifics. Try "unusual engines" on Google and be prepared to give up several hours, days, weeks, depending on your interests
Good luck
Freddie

 

[megashawn]

I've heard of water injection, is this what your talking about? That is one of the greatest developments for engines in sometime.

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

 

[ShawnD]

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

Turbo is when more air is forced into the cylinder to give higher compression.

 

[russ_watters]

To: Lamar
Why has the problem not been solved? Goood question! Answer: (A) You pay for all the unburned fuel going out the tailpipe. (B)This represents positive cash flow for refiners and petroleum companies. (C) They get very upset at people who want to increase fuel efficiencies by factors of 2, 3. 5, etc. (D) What happens to good hearted people who want to cut BIG OILs cash flow by factors of 2, 3, 5, etc? In the 1920s a lot of work was done to improve gasoline mileage. For some strange reason, it is very difficult to locate records of this work. On the Internet, "This page is not available" comes up many times. I wonder why? Nevertheless, there is a lot of valuable information on the internet. It will just never be implemented in the United States. Think perhaps China, Russia, India, etc. Good luck.
Freddie

Please keep this nonsense out of the engineering forum. Do you have any idea how many engineers there are in the world? How easy do you really think it would be to keep such technology off the internet? A halfway competent physicist can build an H-bomb (the CIA did a test to find that out). How much harder do you think it is to make a new carburetor? The idea that there is some secret technology out there that is being suppressed is absurd.

Have a look at the efficiency equations I posted. They don't leave a whole lot of room for 100mpg cars.

I had heard that buy running your fuel through a copper tube, and wrapping this tube around the heater core water line will heat the fuel, causing it to expand, thereby burning it more effiecently. I don't know the technical reasons why.

Yes. Pre-heating reduces the activation energy needed inside the cylinder. You can also recover heat from exhaust gas for the same purpose. But here's the catch: it takes energy to pump the gas through the extra piping and extra money to build the engine and the benefit is maybe an extra percent or two of efficiency.

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

A turbocharger and supercharger both increase the airflow to the engine - turbocharger by using exhaust gas to spin a turbine (losing some energy in the process), and a supercharger by using the drive or cam shaft to run the blower (using some energy in the process). In practice, neither result in higher efficiency, just higher peak power output.

Also, water injection isn't nearly as exciting as its made out to be. It can give a few percent more power or a few percent more efficiency. It doesn't overcome the laws of thermodynamics.

The fact of the matter is that 100mpg is possible with existing technology, but it'll never happen because people don't want it. They want horsepower, air conditioning, power windows, and space. Those things and fuel economy are mutually exclusive. An in-line two seater that looked like a glider fuselage could easily achieve 100mpg (they were sold in the '60s as a matter of fact) - but no one would ever buy it.

 

[Cliff_J]

A turbo or supercharger increases volumetric efficiency - the ability to get air/fuel mixture into the combustion chamber. More mixture, more power. It doesn't change the efficiency of the system in terms of the energy input/output ratio but instead just the amount you can input/output.

Where is this increase in efficiency from water injection coming from? My understanding is using water as a means of controlling detonation (heat control) which means any gains are the result of some other factor (like high compression ratios) and not from the water injection itself. A better formulated fuel could be used in the same engine with the same result without any water in that case, its just the water allows the usage of a lower grade fuel.

Oh, and if you're talking about getting 100mpg the same way the grassroots approach is to building electric cars where every compromise is optimized for efficiency, I'll pass. I've been in a couple fender benders, I wouldn't want to be the guy with no legs having a Zinardi bar named after me. Build a hybrid motorcycle instead, at least it'd be fun.

Cliff

 

[Freddie]

ShawnD:
You are right re the turbo. It put more air into the cylinder, which = more oxygen, which can burn more fuel to give more power. I don't see any effect on efficiency.
Re water vapor, which does affect efficiency, you also get reduced NOx as a side benefit of reduced peak temperatures.
Megashawn: You are referring to a specific technique to vaporize the fuel (copper tube). Numerous techniques have been used. The reason it works is that liquid fuel cannot access enough Oxygen to burn properly. In vapor form it can and does burn readily. The droplets of liquid fuel are the nasty critters you want to get rid of (unless you are an oil company).
Freddie

 

[Arctic Fox]

I thought about designing something that would create large amounts of ozone to feed into the intake. This, along with changing over from gasoline to *propane. Being as my vehicle is already fuel injected, I don’t see any other choice for me.

*That’s a spicy meatball!* :D

 

[Freddie]

My apologies to all. I just discovered that I do not have permission to access this page. And I don't know the routines that I need to get authorized. So thanks to all who participated in what I thought was a worthwhile discussion. Just goes to show ya.
Freddie

 

[russ_watters]

My apologies to all. I just discovered that I do not have permission to access this page. And I don't know the routines that I need to get authorized. So thanks to all who participated in what I thought was a worthwhile discussion. Just goes to show ya.
Freddie

Sounds like you accidentally hit the "edit" button instead of the "quote" button.

 

[Freddie]

Greetings to all:
I have found a really neat website for anybody interested in Internal Combustion engines and related Thermodynamics. Go to http://kahuna.sdsu.edu/testcenter/testhome/indexclosedcycles.html
HOWEVER: This presents an Introduction to some important concepts and thus leaves out some other concepts. I would like to see your comments and if more than 1 or 2 people are interested, I have some comments which may or may not be interesting.
Freddie

 

[Freddie]

better fuel efficiency thru vapor carburetion

The website reference got mangled in copying. The one I was trying to reference was:

http://kahuna.sdsu.edu/testcenter/testhome/indexclosedcycles.html
insert: /testhome/indexclosed cycles.html

This is for an Internal Combustion spark ignition engine.
With reference to all the racing car drivers trying to improve efficiency, etc., water injection kits are readily available on many web sites and have been for many years. There is no secret. Regarding the efficiency equations, I don't see the reference to the effect of steam. I must have misread the equations because steam properties have been well understood since the mid-1800s or earlier. Of course there are those who believe that steam engines never really existed, and water vapor has no effect in creating motive power. I know at least one of you who will not drive his car in the rain because water vapor (or droplets) in the airstream will wreck his engine. Hey, it's OK with me. I somehow got the impression that Physics Forum was a friendly exchange of information. It is really depressing to be sadly disillusioned. But for some of you younger guys out there, Steam Engines really existed.
Freddie

 

[Cliff_J]

Freddie, my engine has 10.5:1 compression. That puts the temp of the intake charge after compression over 500F even assuming 80% volumetric efficiency. After this, the charge is ignited.

The work needed to compress the mixture and heat it (causing the water to form steam) will not be recovered during the power stroke.

Any water will be steam well before the fuel ignites - it will happen to absorb some of the heat in that process from its latent heat during transition so the charge will be cooler when ignited and less prone to detonation. Since there is a lower chance of detonation, you can run a higher compression ratio and this will give you higher efficiency. Its an indirect effect, not a direct one.

No one said there is no steam, its just it is not a factor since its factored into the system before the combustion occurs.

Cliff

 

[russ_watters]

That's a pretty good looking site. No, it doesn't say anything in the efficiency equation about steam because in the specific engine they are showing, steam isn't injected. If you add steam, you need to also use the equations for an open steam cycle. But its even more complicated than that: since the energy required to turn the water into steam comes from the combustion, some of the energy added by the water injection is energy taken away from the regular otto cycle.

FYI, steam engines are only slightly more efficient than gas engines - and their bulk more than outweighs the benefit for a car. To really get a thermodynamic efficiency boost, we need to start using Brayton cycle engines...

And you're right that this stuff isn't a secret. Feel free to use the info available on the net to get yourself a water injection system. Let us know how it works...

 

[Freddie]

The work needed to compress the mixture and heat it (causing the water to form steam) will not be recovered during the power stroke.

The work needed to compress the mixture and heat it will not be recovered duting the power stroke

Looks to me like you are violating the 2nd law. How can you tell when it does not apply?

 

[russ_watters]

Looks to me like you are violating the 2nd law. How can you tell when it does not apply?

No, freddie - the work required to turn the water into steam is now part of the steam. It can be reclaimed only by turning the steam back into water - and in this case it is lost when the steam is sent out through the tailpipe of the car. This is called an open cycle.

I encourage you to start learning thermodynamics. The Carnot cycle is the place to start. HERE is an overview presentation of a college level Thermo 1 course.

 

[Freddie]

Russ:
"Some of the energy added by the water injection is energy taken away from the regular Otto cycle" Exactly right. But the mechanical energy involved is trivial. The tradeoff is that you are taking energy from a high temperature source (initial combustion) and using it to create steam which carries a much lower, but useable pressure out to where the crank angle provides reasonable torque. I don't see anyone talking about the fact that the crank provides a sinusoidal output for a constant input.This seems to be either totally ignored or buried somewhere or considered too obvious to mention. You know that you can have detonation, with very high temperatures and pressures and very little contribution to torque output because of the crank position.
Nest item: "It can only be reclaimed by turning the steam back into water". No, Russ, the purpose of an engine is to turn heat and pressure into work. This happens as the piston moves down and the steam pressure decreases in accordance with the appropriate curves. If the stroke is long enough, you may get condensation. In general, you will be exausting steam at a much lower temperature and pressure because the work was extracted from it. As it leaves the cylinder, it may certainly condense to water.

 

[GOD__AM]

Yes. Pre-heating reduces the activation energy needed inside the cylinder. You can also recover heat from exhaust gas for the same purpose. But here's the catch: it takes energy to pump the gas through the extra piping and extra money to build the engine and the benefit is maybe an extra percent or two of efficiency.

Never the less this pre-heating of the fuel is used widely on snow mobiles.

 

[russ_watters]

Never the less this pre-heating of the fuel is used widely on snow mobiles.

I didn't know that, but it makes good sense.