Three Laws of Car Fuel Economy

Okay, the price of car fuel is going through the roof. What are we going to do about it? Drive less?--That's a very good way to stop global warming. Not a good way to be at Aunt Martha's picnic this weekend.

We could get a super-efficient car (like mine--gets 65 mpg) or get a super-efficient engine (like the one under development--see the full theory at http://www.ernsblog.com/), but you would probably miss the picnic. How about some ways to really cut the cost of gasoline TODAY?

That brings me to a new set of rules. You might say they are Rogers' Laws of Car Fuel Economy. These were mostly known before. They may not actually work for everybody's car, depending on how the car was engineered. A well-engineered car should follow the rules to a "T."

Here are the rules. By following them, you should be able to cut your fuel costs by 20% or more, starting today!

Three Laws of Car Fuel Economy
Ernest Rogers May, 2008

1. In highway driving, for each 5 mph that you slow down, your mileage will increase by 10%.
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2. For any trip with a present average speed of (mph) and fuel consumption of (mpg), if you speed up to save time, the extra fuel you will use can be estimated by—

Extra gallons = (mph /mpg) x (minutes saved /35)

In words, if you divide your normal speed by your usual mpg, then multiply by minutes you want to save (by speeding up) and divide by 35, that’s the amount of extra fuel you can expect to use. It is a handy rule to see the fuel cost for speeding to save time.
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3. Very efficient drivers use pedals less and can get 30% better mileage than inefficient drivers.

New engine cycle is 60% efficient

Analysis of a new engine design is complete! Here are some facts about it:


1. Utilizes a new thermodynamic cycle

2. Will run on most fuels interchangeably with very low emissions

3. Initial design is a compact engine, 130 hp

4. Over 60% efficient over most of its operating range

5. Which means it can help to stop global warming!


We are now looking at ways to fund construction of the small prototype engine. Any suggestions or offers of assistance are welcome. I may be reached at Ernsdesk@aol.com


The engine design is built around a new "thermodynamic cycle." This is a simplified model of how the engine works, which ignores all the messy details of a real engine such as friction, heat loss, and inertia. The cycle is described as a sequence of operations on a captive ideal gas. The new engine cycle is a combination of two old cycles, the Atkinson (or Miller) cycle and the Diesel cycle: the Atkinson-Diesel cycle.

Oh, no, you can't use this ideal cycle formula to design the exact engine and determine its efficiency, but it gives direction to the analysis. A separate program is used for the actual engine design.

I wanted to post the complete description of the cycle and derivation of the cycle efficiency here, but the equations didn't come over in the document. Send me an email if you would like a copy of the complete Atkinson-Diesel cycle description.

LATEST MILEAGE NEWS

LATEST MILEAGE NEWS

Mileage of the Beetle and drag reducer have been significantly increased by lowering rolling resistance of the car's tires. Currently, mileage is close to 65 miles per gallon at 65 miles per hour.

This car is now about as good as it gets. Further steps available to reach even higher fuel economy are:

1. Adding an electric drive (e.g., hybrid conversion)
2. Redesign the car body for lowest drag
3. Incorporate an improved engine.

I am beginning to work on all of these. These steps are much harder than the past modifications to the Beetle. I hope to be able to report on progress later this year.

Ernie Rogers

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CAN WE BUILD MORE EFFICIENT ENGINES?

Stop global warming


Yes, I think we can. The present internal combustion engine was mostly developed in a time when fuel cost and efficiency were not imperatives. We need to go back to the early days of engine devleopment and reassess the way designers handled branches in the design road. We may have overlooked some better choices way back when the discovery of oil in Oklahoma and Texas seemed to say that there would be cheap gasoline forever.

One of these early branches in the road was a choice between four-stroke cycle engines and two-stroke cycle engines for automobiles. At the time, we used carburetors to feed fuel to the cylinders. In this context, the four-stroke engine is a far better choice. (More efficient and less polluting.)

But, the trend today is toward injection of fuel directly into the cylinders. With this modern option, the two-stroke cycle actually provides a far more efficient engine. Here are some other choices that need to be reviewed:

1. Engines are only designed for either gasoline or diesel, and nothing else.
2. Compression ratios are lower than one would choose for best efficiency.
3. Engine design principles are not based on a need to reduce weight.

Some people are looking at the exciting possibilities still left to be explored. A possible outcome may be radically new engine types in the near future.

Ernie Rogers

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MPG Update

I changed fuel in the last few weeks. Currently, I am using Philips diesel from the North Salt Lake Refinery, used in this intermountain region. I seem to have better mileage with this fuel, now getting 62 mpg.

This is a point for reflection-- what further change in driving or car properties should I make to increase my mileage a little more? Any suggestions?

Ernie Rogers

Ernie's Alaskan Adventure

This summer, my grandson, Kai Rogers, and I drove to Alaska--Salt Lake City to Anchorage, 3,000 miles. Of course, we went in the thrifty, fuel-sipping Beetle TDI diesel.

Total fuel for the trip to Alaska, 3,000 miles, was 52 gallons. Not bad --- about 57 miles per gallon. On the return trip we did a little better, getting 58 miles per gallon.

I had hoped to do better. Here in the western states, my summer mileage is consistently about 60 miles per gallon. We surmise that the reason is the difference in climate. It would be necessary to use a little different diesel fuel blend in northern Canada and Alaska to insure that the fuel doesn't solidify if the weather were to suddenly turn cold. Cold-weather fuel contains a little less energy than what we use down around Utah in the summer time.

You can follow the link to my car's web page to see some pictures and hear more about the trip.

Ernie

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World is running out of oil--then what?

I think it is no secret now, when I tell you that the world is running out of oil. (See Hubbert's peak.) Up until now, most of our oil has been used to make energy (or as fuels). This has got to stop because the day is coming when oil will be more valuable than energy, and will be needed for other uses. (Should I mention global warming?) That brings up a new and timely idea.

If we think of using oil to make energy as a reaction:

Oil --> energy.

We should remind ourselves that the reaction is reversible, at least in principle:

Energy --> oil

There is an inefficiency involved in going either way. The existence of this reversible reaction has the effect of placing a link between the cost of energy and the cost of oil. Some examples:

1) The cost of oil can not be substantially lower than the cost of equivalent energy from other sources (allowing for inefficiency), otherwise energy production will shift to use of more oil. (Which just supposes that economics has more sway than common sense.)

2) The cost of oil can not be substantially higher than the cost of equivalent energy from other sources (allowing for inefficiency), in the long run, because man's inventiveness will allow oil to be made from energy.

The question then follows as to whether there are or can be practical means for making oil from energy.

We may say that we live in an exciting time, when the world has to face a transition from the "industrial age" when we have powered everything with fossil fuels. The daily advance of news on this, this summer, is quite surprising. The underlying question is, what will replace oil? Wind turbines, etc., make electricity, not oil. The question hasn't been very important until now, when we can see that we really are going to run out. There are maybe three answers to the question--

1) Biomass to oil, fuel, etc. An example is NREL's research on using the Fischer-Tropsch (or F-T) process to convert trash to oil--not the best approach. The direct conversion with pressure and heat is better (sorry, don't have the reference, now in pilot plant operation). There are many others, including my favorites: growing biomass at sea for conversion to methane, and producing "biodiesel" from low-value crop materials.

2) The darling of industry, converting coal (or natural gas, oil shale, etc.) to liquid fuels. This is already in use in one two-step process: "coal gasification" to synthesis gas, then coversion to long-chain hydrocarbons with the F-T process. This produces a very good-quality diesel fuel, or about anything else you want. Pretty rough on the environment, so only half a solution.

3) Efficient conversion of electricity or other high-quality energy directly to hydrocarbons. Most of the good alternate energy approaches produce electricity. Okay, I will list the best of these: wind, tide /wave, PV, and solar-thermal. A unique exception, a dish solar concentrator, can also produce high-quality heat (10,000 suns) at the focus.

Number three is exactly what I was talking about. It is the only one that makes sense but doesn't rely on photosynthesis. Notice that I have excluded hydrogen from consideration, as a replacement for oil and other liquid fuels. I know further that hydrogen can be made from electricity, and in turn can be used to make hydrocarbons, by the F-T process. This looks way too expensive and inefficient to get very far, in my judgement.

I was searching around on the internet last night, looking for new ideas on making synthetic oil or hydrocarbons--Ideas that would fall within #3. I found nothing! This topic, producing hydrocarbons from electricity or heat directly, is of great importance for the future of man. Though it may be a little early yet, this will be a major problem soon. When we (the world) turn our attention to it, solutions will quickly emerge. I see two paths:

1) Use of heat. Two reactions at high temperature have been mentioned in the past:

H2O --> HO + H --> H2 + O2
CO2 --> CO + O --> CO + O2

Removing the oxygen, the products together are "synthesis gas," which can be used to make alcohols or long-chain hydrocarbons by the F-T process. Or, either of the gases singly, with water or CO2, can be used to the same end.

There are surely many other known processes that I am unaware of.

2) Use of electricity to make hydrocarbons directly. This seems to be a largely unexplored field, having been at an economic disadvantage for the last century. Here, two approaches come to mind: plasma chemistry, driven by electrical power. A subset of this are the thermal processes mentioned in 1).

A second approach is well known, but not worked on currently, I think-- that is organic electrochemistry for making fuels. In principle, electrochemical reactions carried out in cells can make hydrocarbons and other organic materials. A few industrial processes already exist that do this sort of thing.

Michael Faraday reported an experiment that should be a point of beginning for research. He passed an electric current through a solution containing carbonate ion, and discovered that organic compounds were formed. (Formic acid or formaldehyde?)

I hope I have shed some warm light on Hubbert's peak.

Ernie Rogers