Sorry it took so long, here is some proofreading I did on your book:
Just minor misspellings/syntax issues (corrected). Excellent book overall, you make the concepts you present easy to understand.
————————You’re welcome, George.OK, I’ve finally managed to grab some time & go through the book – here are my corrections for grammar/spelling, suggestions & comments. Hope you find it useful.=================
On web site
“explaination” -> “explanation”
Comments:10 – “excellent combustion” – the exhaust having only 6% of fuel unburned is probably a massive underestimation as the paper doesn’t say if the tests were of the exhaust gases AFTER or BEFORE the catalytic converter. As they mention taking measurements on one truck (which also makes the measurements suspect; they should have taken measurements from several vehicles and given the range) and do not mention a cat at all it would be safe to assume AFTER. The catalytic converter gets to incredibly high temperatures and as such would combust the majority of unburned hydrocarbons that reach it (As perhttp://www.academicjournals.org/article/article1380014872_Metwalley%20%20et%20al%20pdf.pdf nearly all of it in lab conditions with a brand new cat, see figures 18 & 27). So, to put it politely, I’d say they f*ck*d up & the figures given are virtually worthless; the actual unburned HC straight out of the engine would be much higher.
Also there is an implicit assumption that all the burned hydrocarbons contribute to motive power, which we know is not true – as it is a chemical process, it take some time for what can be quite long hydrocarbon chains to be broken down into individual carbon and hydrogen atoms which is required to combine with oxygen to form CO2, H2O and heat. Most of this happens AFTER the piston has expanded, ergo is wasted energy, which you address later in the book – even measuring the gas straight out of the engine is misleading because of this.
In addition some of the energy is “used” to convert nitrogen in the air into various NOx species, which is the primary official reason for us having a catalytic converter, in order to break these down and prevent smog.
27 – the HP required to propel a 1700 pound car with drag coefficient of 0.32 graph is misleading, with the line being a lot higher than it should be, especially at high speeds. Whilst it is true that most of the energy that goes into propelling a car forwards at low speeds (below about 40 mph) is due to friction caused by the mass of the car pushing the wheels into the road, above this speed the engine is having to spend more of its energy on fighting air resistance than it does on actually moving the vehicle. So at high speed the HP required has virtually nothing to do with the mass of the vehicle – it’s all about the surface area of the car as viewed from the front (i.e. what the air is actually “hitting”) and the shape which determines how much drag there is due to turbulence. The perfect shape is a raindrop on its side (i.e. nearly spherical front with long tail), as shown by this being the shape water automatically forms when falling through the atmosphere (and similarly why a sperm is the same shape, to minimise energy loss in its race of life). What we really need is for the people who came up with this graph do the same test but with the car in a vacuum – you’d seal in the engine compartment & feed in air via a tube, then similarly have the exhaust going out another tube, & chuck the lot on a dyno and graph that. I’d be betting you see the line go up to begin with & then nearly flatten out.
So, as per http://en.wikipedia.org/wiki/Drag_coefficient, it’s all about the shape and size of the vehicle that determines fuel consumption on the highway.
The only energy you’re spending that is related to the mass of the vehicle is that required to overcome static friction initially (ever noticed that it takes a bit of an effort to get something moving, but it gets a lot easier after it starts & then remains constant? That’s due to static friction – electromagnetic bonds formed between the surface of the two objects when they’re at rest), which as per F=ma is constant regardless of your velocity (as the mass of your car is constant, and the acceleration caused by gravity is constant), plus a bit due to friction between the tyres and the road, which is something you can cut with low friction tyres, but obviously not too much or else it’s just like you’re driving on ice. Notice how a car on ice can move very long distances even when the engine is turned off & brakes applied? That’s even more evidence as to how little energy you need to keep a car moving once it’s in motion, regardless of its mass.
So, I’d be a bit cautious about making claims that the 135 mpg Peugeot is achieving a thermal efficiency of 60% – I’d be betting in reality that’s 20-30%, maybe even less. It only stands to reason as well if the Opel was able to get 375 mpg; otherwise you’d come to the conclusion that it was achieving a thermal efficiency of 375/135*60=167% – yay, we’ve achieved overunity!
=============Here’s some additional ammunition you might like to include – I did these calculations a few years ago back when I was in CSIRO when I was writing an article on comparative efficiencies between petrol and electric vehicles. The AEVA (Australian Electric Vehicle Association) had several members who converted bog standard petrol cars into EVs by ripping out the engine, gearbox and fuel tank and replacing them with an electric motor & battery pack of a similar overall mass. They didn’t make any optimisations like putting small electric motors in each of the wheels & using drive-by-wire which would allow them to save a fair bit of weight and friction by getting rid of the drive train, etc etc, so this means that in terms of energy requirements for distance travelled the vehicles are directly comparable with petrol vehicles on the road today (or a few years ago). As I’m Australian I use metric, not those weird imperial units you guys use 🙂
According to the AEVA in urban driving you need 130 Wh/km, on the open road 150, and on the highway 210 (presumably as speed 60, 80, 100-110 kph and increased air resistance); when the traffic is heavy it’s about 115 Wh/km (40kph). Anyway, when we take these figures & realise that petrol contains 34.92 MJ/L (US figures) => 9700 Wh/L, if we use the “open road” figures we should be able to get 65 km/L if the engine was as efficient as an electric motor. According to http://www.engineeringtoolbox.com/electrical-motor-efficiency-d_655.html the electric motor is around 90% efficient in a lab (I have my doubts; I’m guessing in practise and when you take into account losses in the battery feeding out energy really quicker it’d be under 80%), so that means the 100% efficient figure would be 75 km/L (or more). As per http://www.vangeyn.net/mpg/?km=75&submit=Convert that’s 175 mpg (which we already know is an underestimation based on the Shell Opel results), or 125 mpg for when the car is travelling at 100 kph+ (60 mph).
An internal combustion engine is effectively a Carnot Cycle, if we believe the physicists (http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/Thermodynamic_Cycles/Carnot_Cycle; although as you point out this ignores the work caused by the velocity, and thus pressure, of the explosion). As per https://answers.yahoo.com/question/index?qid=20110527202032AAzE7uc we can get to around 2500K (or more) inside the piston, with standard conditions being around 300K. If we put these into
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.htmlthen we get a maximum efficiency of 88% – so that means it SHOULD be possible to get the SAME efficiency in the petrol vehicle as we are in the EV.
So, based on these figures we’ve PROVEN based on real world figures that any decent modern petrol vehicle should be getting over 100mpg.
Peter______________ Thanks, George!
…, it looks very well thought out, researched, and understandable.