I'm fascinated by the web site of Professor Steven Dutch at the University of Wisconsin Green Bay. The portion of his site entitled "Science, Pseudoscience, and Irrationalism" has dozens of articles, most of which I find interesting. Some I agree with, others I don't but they are interesting reading.
To the point of this blog, he has an article debunking the "200 m.p.g. car" that the conspiracy theorists claim has been suppressed by the oil industry. His article aims to use rough and ready methods to show the impossiblity of a simple "gizmo" that, bolted onto the engine, would enable an ordinary car to achieve extraordinary gas mileage.
Dr. Dutch uses a 1000 kilogram mass car in his calculations, mine is about twice as massive. As it happens, my vehicle has a big (4.8 liter) engine and I think it's reasonable to estimate that internal friction and pumping and throttling losses are directly proportional to engine displacement.
Surprisingly, Dr. Dutch converges on about 40 miles as an estimate for what can be extracted from a gallon of gasoline for the car in his example. My car, being twice as massive, having at least twice as large an engine as the car Dr. Dutch analyzes and probably 40% larger "flat plate area" (the area presented to the oncoming air to develop drag), etc., should get half of that. My actual results are amazingly close to this.
What does it mean? Well, it means that in order to achieve major reductions in oil consumption without going to vehicles such as the scooter I discussed a couple of posts back, large-scale changes must be made in the technology of internal combustion engines or other propulsion methods must be employed. It means that I'm probably approaching the limit of what I can achieve by driving methods alone, though I'm sure that slight gains are still possible.
The other eye-opening aspect of Dr. Dutch's debunking of the 200 m.p.g. carburetor is his demonstration that exotic test methods and advanced mathematics aren't necessary to derive useful information about practical problems. His analysis utilized a car, a stopwatch, some easily available information (such as the cold cranking capacity of lead acid batteries), high school level physics and experience to come to a conclusion that my real-world tests seem to confirm.
1 comment:
What does it mean? Well, it means that in order to achieve major reductions in oil consumption without going to vehicles such as the scooter I discussed a couple of posts back, large-scale changes must be made in the technology of internal combustion engines or other propulsion methods must be employed.
This is woefully incorrect. The route to significant gains is in lighter vehicles, given that two thirds of the energy uses at the wheels is used to overcome weight.
There are two ways to decrease fuel consumption in automobiles:
1) Do less work
2) Work more efficiently
We are reaching the limits of the gasoline powered otto engine on item #2. We have barely begin to touch item #1. Roughly speaking halving the work will result in half the energy required, resulting in about a doubling of fuel economy. Safety would increase as well.
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