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mgb_phys
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That explains it - I though DISI was the same as the spark-less gasoline in a diesel cycle engines. Those DO have better efficency and lower NOx
It's mainly done in a locomotive because of the difficulty of making a transmission that has enough torque to start a 1000 ton moviong train and also move it at 125mph. Fully electric locos are mainly because of the much higher power density you get with electric motors. An intercity high speed train is 5MW, about twice the power of a diesel loco but the motors fit under body. The maintenance is also a lot lower as well as noise, smoke etc.jack action said:The locomotives use that system and I always wondered why it was never implemented in a personal vehicle (I'm sure there are drawbacks I'm not aware of, but with today's EV, I think it is a pretty similar technology).
Even with perfect sealing a Wankel engine is fundementally limited in the compression ratio it can achieve just form geometry. A piston engine is only limited by the strength of the metal so you can make small economical diesels with 20:1 compression getting half that in a Wankel is real feat of engineering.And, if we assume that R&D is the solution to EV, how come we don't assume that it would be the answer to make a better rotary engine? It is easy to say that the only viable rotary engine is the one from the RX-8 and that it is not as good as traditional piston engines,
jack action said:First, I see a lot of people giving excuses for EV concerning their high cost or lack of practicality by saying that development is underway and all problems will be solved in the future. To me that sounds like "magic thinking" where there is a way that exists which has no drawback and only advantages. I've never seen this in any engineering field and if such a way exists, with all the time and money spent on EV, it would have been obvious by now. It is not.
jack action said:And, if we assume that R&D is the solution to EV, how come we don't assume that it would be the answer to make a better rotary engine?
jack action said:Finally, although I'm no expert on the subject - and neither a radical opponent - when talking about nuclear energy being safer than anything else, I'm a little skeptical. Never heard of Three mile Island or Tchernobyl? But I'm sure there are good excuses and it will never happen again.
If we recall the goal is transportation, not just to store energy, then we see that other issues like the efficiency of the motor are also important.jack action said:The problem with any engine (no matter the type) in a vehicle is to store the energy efficiently. Mechanically, you can wind up a spring, speed up a flywheel, compress a fluid, etc. Electrically, you need a battery. But no matter how you look at it (volume, mass, safety, cost, power, etc.), storing it in a liquid fuel that you will burn is pretty hard to beat.
jack action said:Let me add my 2¢ and stir the pot a little bit.
First, I'm a big fan of the IC engine in personal vehicle and I don't believe it will be efficiently replaced soon. Although, there is a lot of propaganda to make it the devil's machine. IMHO, the way it is overused is more responsible of the problems we have.
jack action said:Now, without endorsing everything he said, I would like to bring some defense to sr241 (He seems lonely in its corner!).
First, I see a lot of people giving excuses for EV concerning their high cost or lack of practicality by saying that development is underway and all problems will be solved in the future. To me that sounds like "magic thinking" where there is a way that exists which has no drawback and only advantages. I've never seen this in any engineering field and if such a way exists, with all the time and money spent on EV, it would have been obvious by now. It is not.
jack action said:And, if we assume that R&D is the solution to EV, how come we don't assume that it would be the answer to make a better rotary engine? It is easy to say that the only viable rotary engine is the one from the RX-8 and that it is not as good as traditional piston engines, but a lot more R&D went into the last one. A LOT more.
jack action said:Finally, although I'm no expert on the subject - and neither a radical opponent - when talking about nuclear energy being safer than anything else, I'm a little skeptical. Never heard of Three mile Island or Tchernobyl? But I'm sure there are good excuses and it will never happen again.
jack action said:It seems that there is not only sr241 that says stuff based on dreams on this thread. It's not because a theory is popular that it is true. You have to keep an open mind to make a discussion viable.
The "question" exists unitl it is proven with a demonstration that it works as claimed because as other similar engines have demonstrated, it doesn't work as claimed. Really, it is incorrect to say "Anyoon uses" since until it is sucessfully demonstrated it doesn't "use" anything.sr241 said:for sealing Anyoon uses flourosilicone rubber ( can withstand above 400c) which is used in space shuttle nozzle bushes. and typical piston ring temp in engine is 220C refer "Engineering Fundamentalsof the Internal Combustion Engine byWillard W. Pulkrabek chapter ten page315"
So there is no question of lasting of seals
There are two obvious problems:what is wrong with calculating Carnot efficiency between 2000k and 300k it is said 85% if you have new method for calculating Carnot efficiency please give me I will send it to laughter therapists (they will use it for those having difficulty in laughing).
No one was injured by TMI. It is a good example of just how safe the nuclear power industry is in the West that despite massive failures, virtually no release of radioactive material happened.jack action said:Finally, although I'm no expert on the subject - and neither a radical opponent - when talking about nuclear energy being safer than anything else, I'm a little skeptical. Never heard of Three mile Island or Tchernobyl? But I'm sure there are good excuses and it will never happen again.
sr241 said:what is wrong with calculating Carnot efficiency between 2000k and 300k it is said 85% if you have new method for calculating Carnot efficiency please give me I will send it to laughter therapists (they will use it for those having difficulty in laughing).
mheslep said:I say required because setting all of the century's improvements aside for moment and looking only at the problem of individual transportation from A to B, and seen only as a self-contained engineering project, the internal combustion engine is a mistake, a disaster. No I'm not talking about all the environmental issues. I refer only to the engine itself and what's required on an auto-mobile.
(...)
Still doesn't change my view that the combustion engine is twisted joke of an engineering solution to the problem of moving things around, as compared to elegance of the electric motor.
xxChrisxx said:Just like the car replaced the work horse. And horses were used for pleasure. The EV will be the work horse of tomorrow, leaving petrol engines for pleasure.
I am also a realist, we can't continue to burn oil at the rate we are. I also understand the concept of diminishing returns. The IC is 120 years old, it's coming to the end of it's development life, there is only so much you can get out of a concept.
(...)
the power generation, and delivery systems are both more efficienct for moving you along the road. Not only that but the characteristics of an electric motor make it acutally better than an IC engine for general driving. They have 100% torque from 0 RPM up to about 80% max 'revs'.
Between 1832 and 1839 (the exact year is uncertain), Robert Anderson of Scotland invented the first crude electric carriage, powered by non-rechargeable primary cells.
Electric vehicles were among the earliest automobiles, and before the preeminence of light, powerful internal combustion engines, electric automobiles held many vehicle land speed and distance records in the early 1900s. (...) and at one point in history out-sold gasoline-powered vehicles.
Mech_Engineer said:The only thing holding electric vehicles back is energy storage.
mheslep said:which is about where we are today - average car can do nearly 400 miles, average EV 100 miles. Start adding to that story the ability to charge over night
xxChrisxx said:Currently there simply are no drawbacks for electric vehicles apart from:
infrastructure.
energy storage.
cost.
Thats it's,
(...)
Conversely EV will have their flaws too. Suc has hot battery packs, and the stuff listed above.
xxChrisxx said:No it's not becuase its popular that it's true. It's true becuase it's true. End of.
xxChrisxx said:Saying you should 'ban the electric car' becuase you should be developing something else it's utterly stupid. It's product lifecycle 101. To be good and sucessful you need a product or technology on each strange of the cycle. To try to artificially extend one at the expense of a new product with more potential it's simply stupid.
Mech_Engineer said:I'm not understanding this obsession with rotary engines? They are in the end an internal combustion engine, nothing special. If they were capable of higher compression ratios they might have a chance, but they just aren't (9:1 compression is a real challenge, diesels hit 20+ without trouble).
What "R&D" are you hoping to do on a rotary engine that wouldn't benefit any number of standard piston engines?
mgb_phys said:Even with perfect sealing a Wankel engine is fundementally limited in the compression ratio it can achieve just form geometry. A piston engine is only limited by the strength of the metal so you can make small economical diesels with 20:1 compression getting half that in a Wankel is real feat of engineering.
Yes piston engines have had a lot longer R&D, but all that R&D has also benefited rotary engines. Mazda weren't exactly workign with stone age tools to design their engine.
There are two obvious problems:
1. The high temp of a combustion engine isn't anywhere close to 2,000 K. The maximum flame temperature (in air) of gasoline is about 1,300k. That gives a maximum Carnot efficiency of 77%, assuming the Th would really be equal to the maximum flame temperature (which it wouldn't).
2. This engine isn't a Carnot engine: Carnot efficiency assumes no losses anywhere, ideal gases, etc., and isn't possible.
At that time there was only one advantage: range.jack action said:So EV are 175 years old. They were 'replaced' by the 'new and improved' ICE technology about 75 years later, even if they already had all the advantages of low RPM torque and better efficiency over the ICE. A good thing that, back then, nobody said "The EV is 75 years old, it's coming to the end of it's development life, there is only so much you can get out of a concept." or we wouldn't be here having this discussion about your 'new' concept.
People did not choose ICE over EV for personal use just for the fun of it, there were major advantages.
Battery swaps require 60 seconds currently in http://www.betterplace.com/company/video-detail/tokyo-electric-taxi-project-opening/" .energy storage, infrastructure, hot battery packs, limited range, 'filling up' measured in hours instead of minutes,
Cost per mile including vehicle depreciation is about the same as a combustion vehicle with a leased battery.cost.
Battery heater.Oh yah, and you forgot battery performance variation with outside temp (I live in Canada, what can I say).
Theoretical limit of Carnote efficiency for IC engines can be overcame by injecting water for cooling by using this method even 100% efficiency is possible.
sr241 said:just tell me if recover all heat given to system does that gives 100% efficiency. here Carnot efficiency does not hold. for 100% Carnot efficiency you either need T_hot to be infinity or T-cold to be 0 kelvin. if you have theoretical support against the above said then I will appreciate you.
sr241 said:not all the heat of system heat that is given to it. An isentropic system is reversible
sr241 said:in water injection a new working medium(water) is introduced in 3rd stage of cycle. when hot gas and water become in equilibrium inside engine, temperature will be lower than hot gases and pressure will be higher due to phase change of water. so there will be huge reduction in cooling losses . Due to higher expansion ratio these steam and gases can do more work so exhaust losses too will be greatly lower.
sr241 said:second law states that "It is impossible for any system to operate in such a way that the sole result would be an energy transfer by heat from a cooler to a hotter body." So more than 100% efficiency is impossible, however it does not states near 100% efficiency is impossible.
Theoretical limit of Carnote efficiency for IC engines can be overcame by injecting water for cooling by using this method even 100% efficiency is possible.
Both of these conditions are impossible to achieve. Th cannot be infinity; Tc cannot be 0 K. So 100% efficiency is impossible, as others have been saying.sr241 said:for 100% Carnot efficiency you either need T_hot to be infinity or T-cold to be 0 kelvin. if you have theoretical support against the above said then I will appreciate you.