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Suggest topic for paper presentation

  1. Jul 24, 2004 #1
    hello

    I am doing B.E. in Instrumentation & Control at L.D.College of Engineering ,Ahmedabad,India.
    As a part of my course there is a subject for which i have to give seminar on any topics related to my course...
    this topic should be new & easily understable..
    So if anyone has information for it..
    Plz give ur suggestion

    RAHOOL
     
  2. jcsd
  3. Jul 25, 2004 #2
    Rahool:
    Suggestion: 1. Measure peak temps and pressure in cylinder of internal combustion engine. 2. Repeat measurements with introduction of water spray into the intake airstream. This has enormous economic importance but may be dangerous politically.
    Good luck.
    Freddie
     
  4. Jul 25, 2004 #3

    russ_watters

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    Not to mention dangerous to the engine. There is a reson it isn't done and it has nothing to do with politics.
     
  5. Jul 26, 2004 #4
    Russ is right. If you run your garden hose output directly into your running engine, you can wreck it. On the other hand, if you drive your car during a rainshower, you may observe that it seems to run "better",whatever that means. I should have been more specific. like "a spray of very fine water droplets, or even water vapor, in carefully controlled quantities." I will try to be more precise in future posts. Thanks, you Hawkeyes.
    Freddie Suggest topic for paper presentation
     
    Last edited by a moderator: Feb 17, 2008
  6. Jul 28, 2004 #5
    Russ is right. If you run your garden hose output directly into your running engine, you can wreck it.

    Well that's not what Russ was getting at. Water injection cools intake air making it denser and increases the air capacity that the cylinder chamber can hold in each downstroke. It's like adding a supercharger or nitro to the mix. If the engine isn't designed for the increase in chamber pressure from the resulting larger fuel-air burn you'll damage the engine. I definitely wouldn't do it to my weak Neon.

    On the other hand, if you drive your car during a rainshower, you may observe that it seems to run "better",whatever that means.

    It's the same effect that happens during a cold winter day but much less extreme than pumping a spray directly into the air flow.
     
  7. Aug 6, 2004 #6
    Properly done, water "injection" reduces peak cylinder temperatures and pressures by creating steam. The steam carries the existing pressure further out in the cycle where it has greater effect on the crank. What you want is high pressure when the crank is at 90 degrees. What we have now is high pressure early in the cycle which produces high stresses, but only moderate torque.
    High mileage = cutting the cash flow of BIG OIL. This can be seriously unhealthy. Not for the tinkerer or racing enthusiast, but don't think of commercializing it.
    Freddie
     
  8. Aug 10, 2004 #7
    Water droplets in the intake

    Neutroncount
    Water injection cools intake air making it denser and increases the air capacity that the cylinder chamber can hold in each downstroke. It's like adding a supercharger or nitro to the mix. If the engine isn't designed for the increase in chamber pressure from the resulting larger fuel-air burn you'll damage the engine. I definitely wouldn't do it to my weak Neon.

    So you are saying that the WWII bombers flying at 30,000 feet used water injection to make the way below zero intake air COLDER? Of course the "water" injection had to have a lot of alcohol to keep from freezing up in the first place.I think you are confusing water injection with two other guys.
    Freddie
     
  9. Aug 11, 2004 #8
    ehh, how on earth did you make this link??

    He was comparing it to 2 otherways of increasing the amount of air in the cilinders and the effect they can have on an engine that isn't strong emough to handle the increased compression.
    No one said anything about bombers using waterspray's.
    They did use compressors to compensate for the lower air density at higher altitudes.
    Thus letting them take a normal amount(compared to the amount taken in at sealevel) of air in instead of the amount they would be albe to take in should they be purly athmospheric.

    Waterspray is being used on a production car, the Subaru Impreza WRX (from 2003-).
    Although i'm not sure if it is only used to extra-cool the inter-cooler or werther the spray is also going into the cylinders.
     
  10. Aug 11, 2004 #9

    russ_watters

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    So what from the first part of the post implies the high mileage (fuel economy) that suddenly appears in the second part? You have gotten several good explanations on this - do you have any data to show for your idea or is this all conspiracy theory?
    Besides the engine block being hot, when you compress air, it heats up via the ideal gas law. In any case, we're not arguing that it doesn't work - just that it isn't the miracle you think it is.
     
  11. Aug 11, 2004 #10
    If you can take the heat losses of a single power stroke and convert some of these losses to high pressure steam, you will get more power to the crank. Now, believe it or not, but more power to the crankshaft, without using more fuel, translates to better gas mileage. The fact that water turns to steam obeys all the laws of thermodynamics and I agree that it is definitely not a miracle. I have not personally run dynamometer tests using water injection. Most of the testing I am aware of was done in the 1920s. There is some data available via Google, etc. I am also aware of the rudiments of economics regarding large powerful industries. I am really interested in the above referenced Subaru Impreza and would love to hear more about it.
    Freddie
     
  12. Aug 12, 2004 #11

    russ_watters

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    That's all true[edit]. The question is how much do you get? The answer is: very, very little. 5-10% would be my guess.

    One of my clients is an apartment building in Philly. They have a CoGen plant, which means they have a diesel generator that also produces steam. The steam come from waste heat from the engine block and from the exhaust stack. Sounds great, but in practice, its only economical when its really hot or really cold outside use the steam to heat or cool the building(you can use steam to make chilled water) to. It is certainly not economical to recover the heat to drive another turbine.

    The best way to recover heat from the engine would probably be to use it to preheat the fuel (you'd probably also need higher octane gas).

    [edit]All true, but that's not how water injection works. I think what you are forgetting is that when you inject water, the mixture of the water and exhaust gases has a lower temperature than the exhaust gases alone would have. Turning the water into steam absorbs some (a lot) of that energy. So a car that generates 220 horsepower with water injection is not using the same amount of fuel as the same car with 200hp and no water injection. Its using more. So now that I think about it, my efficiency number is probably high: you may gain 10% in power, but likely 3-5% efficiency.
     
    Last edited: Aug 12, 2004
  13. Aug 12, 2004 #12
    Russ Waters:
    I think a lot of people are interested in engines, but it looks look you and I are the only ones following up on this thread. From a textbook reference on automotive engines: Approx 15% to propel the car, 15% for power train and engine friction. All the rest are HEAT losses. If we could turn all the heat into propulsion we could get 70% /30% = 2.33 times the original gas mileage. Now a quote from a website:
    www.rallycars.com/Cars/WaterInjection.html
    "Water injection is used to lower in-cylinder temperatures and burn the air/fuel mixture more efficiently, thus helping avoid detonation" This is true, but this still leaves out an important detail. Do a simple thought experiment: Apply a constant pressure to a piston in a cylinder. If the piston is at top dead center, there is no torque produced. Likewise, at bottom dead center, piston pressure produces no torque. Somewhere near 90 degrees, you will achieve maximum torque out for a constant piston pressure.
    A major effect of water injection is to produce steam which carries a relatively high pressure out to a more effective crank angle. Instead of producing waste heat, you are producing mechanical power. Its the old idea of work smarter, not harder, which means you need to look very closely at what happens at ignition and during the power stroke. Your comments re the Diesel engine refer to the heat wasted by the Diesel and dumped externally, which may or may not be useful. The MAJOR problem with using water injection in a car is that the engine runs so cool that your heater has no heat source. You need to install a gasoline car heater, like the old VW bug used to use. But some people live in warm climates and would not consider this a problem.
    All of this has nothing to do with using water to cool an intercooler, etc. I don't know if that is referred to as water injection or what. This is the case for the Subaru Impreza.
    Now, you specifically ask "How much do you get?" Well, lets try 2.33 times for openers. Beyond that, I wouldn't consider giving a definite number. So I guess Russ is not going to dump 20 million bucks into R & D to commercilize the process. Hey, it's OK with me. I figure this site is just a friendly exchange of information. I sure wish I could figure out how the darn QUOTE system works, tho.
    Freddie
     
  14. Aug 13, 2004 #13
    Rahool:
    Forget the whole thing.
    My apologies to all. I just discovered that I do not have permission to access this page. I don't know what the procedure is. So you can just discount everything I said. Hey, if I'm not authorized, obviously, I don't know nuthin'.
     
  15. Aug 17, 2004 #14
    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/t...osedcycles.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.
    This all has a direct bearing on water injection, which may be hard to understand without some good mental pictures. Check it out.
    Freddie
     
  16. Aug 22, 2004 #15
    This thread overlaps one on the General Engineering forum titled Vapor Carburetion. It looks like a lot of people are interested in getting better gas mileage by adding the high priced miracle additive known as H2O.
    Freddie
     
  17. Aug 24, 2004 #16
    I think a lot of readers of this thread did not do the arithmetic! Russ says "Maybe 10% in power and 3 to 5% efficiency." I said that if all the wasted heat could be used, the improvement would be 70/30 = 2,33 times. Obviously, 2.33 is less than 10% or 5%. OR IS IT? 2.33 times is 230 PERCENT! I did NOT say this was attainable. I just pointed out that all that waste heat is NOT a desired product of an engine, and if it could be converted to mechanical power it would be worthwile. Especially at todays gas prices.
    As for what do all those racing enthusiasts do, they spend upwards of $1000 to install commercial water injection kits to give them a little extra power for racing. If I had the extra bucks, I would install water injection on my old 4 cylinder Dodge Caravan in a minute. The thermodynamics website referenced above got mangled. Go to the vapor carburetion thread (In Engineering Design) for a corrected website reference.
    Freddie
     
  18. Aug 25, 2004 #17

    russ_watters

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    Freddy stop spamming this OT vapor carb stuff. If you actually want to discuss it, we can discuss it in the other thread.
     
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