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6 Dec 2008, 10:45 (Ref:2348759) | #1 | ||
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Heat at Air Intake
Hi guys, not a whacky idea this time, I promise
Exhaust gasses and intake gasses are normally quite hot due to all of their movement through the various systems they go through (including combustion!), and as density changes at an almost inverse exponential rate against temperature, is it a good thing they're warm? Sure the increased pressure might be good, but is the decreased density good for combustion? Would it be possible to pass the exhaust from a turbo for example through a water/oil coolant system to make sure that it doesn't get too hot? Air in >> Combustion >> Exhaust >> Turbo >> Coolant System >> Air System Of course there would need to be some regulation to make sure too much kinetic energy isn't robbed, but is this just too much effort for too small a gain? Is it even viable in the first place? Thoughts please! |
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6 Dec 2008, 14:39 (Ref:2348898) | #2 | ||
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WTF are you on about. explanation please ? Cooling the exhaust gasses "after" the turbo I can't see what that would do, as for the induction that's why sodding great air/water inter coolers are made !
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
6 Dec 2008, 14:44 (Ref:2348902) | #3 | ||
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Unless this is some sort of EGR* system, why would you do that?
*Exhuast Gas Recirculation, which can be used to reduce emissions. |
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6 Dec 2008, 16:10 (Ref:2348967) | #4 | ||
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For best exhaust performance you want to keep the heat in the exhaust - look at F1 and Top Fuel cars - they do NOT lag their exhaust pipes. There might be a tiny benefit in lagging a closed wheel car as it MIGHT reduce the under bonnet temperatures sufficiently to give another horsepower or two, but I'm not a believer.
Exhausts scavenge better with higher temperatures. Lagging also increases the chances of the exhaust material becoming too hot and it softening/deforming. |
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6 Dec 2008, 16:42 (Ref:2348999) | #5 | ||
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Which is exactly the reason we stopped lagging Manifolds years ago,got pee'd off with having to keep welding them up again!!
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6 Dec 2008, 17:51 (Ref:2349048) | #6 | ||
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I see from your profile that you are at Brunel University(or was) studying "Motorsport Engineering" . Looks like you've been studying the Beano !!, but I'll give you the benefit of the doubt if you can explain what you mean .
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
6 Dec 2008, 18:00 (Ref:2349059) | #7 | |||
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6 Dec 2008, 19:14 (Ref:2349113) | #8 | |||
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The concept is based upon what was stated before as an EGR system whereby the exhaust gasses were passed through the turbo (or more likely a supercharger), cooled and used in the combustion process again. My question was whether if the reused exhaust gasses were then further cooled whether that would generate more power or less. |
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6 Dec 2008, 19:29 (Ref:2349123) | #9 | ||
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You could wrap your air intake pipes, with a small copper pipe and run compressed CO2 or freon ( as Air Con ) though the copper pipe too dramatically cool the air intake pipes and lower the air temp going into the manifold.
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6 Dec 2008, 19:41 (Ref:2349129) | #10 | |||
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6 Dec 2008, 20:00 (Ref:2349142) | #11 | |||
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6 Dec 2008, 20:08 (Ref:2349144) | #12 | |||
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6 Dec 2008, 20:45 (Ref:2349158) | #13 | ||
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Does all of the oxygen get used in the cylinder though?
Say you have an air intake limit, would there be any benefit in running some of the exhaust gasses back through the combustion process at a cooled temperature so they essentially burn up all of the available oxygen, using the air that has already been taken in. I apologise if this seems like a ridiculously stupid concept if it is, engines are by no means my strong or favourite point of motorsport (a lot more interested in composite and bodywork technology), and my knowledge is very limited by engineering standards. |
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6 Dec 2008, 21:33 (Ref:2349189) | #14 | |||
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6 Dec 2008, 21:46 (Ref:2349196) | #15 | ||||
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Maybe you'd like to expand on your idea - are you actually proposing anything that isn't being done now, apart from cooling the exhaust gases? |
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6 Dec 2008, 22:30 (Ref:2349226) | #16 | |||
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This was a brave attempt to update the 2 stroke and even passed the emissions tests that were in place at that time. I have one in the workshop as a keepsake!. I'm sorry if you think I'm a bit sharp with you ,but this is a discussion forum that's just like a worldwide debaters club where "most people" will agree to disagree. I would think that most things have been thought and tried out on the ICE as we know it especially in the last decade, and wouldn't think that any "startling" revelations will come in the near future. |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
6 Dec 2008, 22:57 (Ref:2349234) | #17 | ||
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littlefarny,
A self contained cooling system, as suggested by Au Engle, would add a lot of weight. You could limit that by not recompressing the refridgerant in a total loss system, CO2 or freon (aren't those banned now?) that expands into the atmosphere to cool, but why not use something to do two jobs? (The Lesson According to St.Colin of Chapman). Fuel needs to vapourise in the intake tract, so use the fuel passing to the injectors to cool the EGR gas. If it's under high pressure, the fuel won't vapourise before the injector, but will do so quicker when it is injected as it will be hotter. The total heat passing through the inlet will be the same, but applied more effectively. John |
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6 Dec 2008, 23:08 (Ref:2349240) | #18 | ||
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http://www.princeton.edu/~ota/disk1/...514/951405.PDF
Although a little out of date this report probably puts things in perspective as to the way things are in relation to engine and car designs pros's and cons. I know its off thread but it makes interesting reading. I hope you have plenty of time ! Last edited by GORDON STREETER; 6 Dec 2008 at 23:12. |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
7 Dec 2008, 00:06 (Ref:2349272) | #19 | ||
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Any increase in temperature if the inlet charge will result in a lower density of the inlet charge. Any decrease in the density of the inlet charge will result in a lower power output from the cylinder, as there will be less fuel and air in the cylinder to combust. This forum is dedicated to racing technology so most probably the priority of most people here is looking for opportunities to increase power output from the engine for racing puposes, rather than how to cool exhaust gases for some unproven improvement in emmissions. Once combustion has taken place in the cylinder, the polutants are already present in the exhaust, and cooling the exhaust gas after combustion will sadly not remove or reduce the level of these pollutants. The main reason in any case for EGR is to deal with emmissions of unburnt hydrocarbons (fuel), not levels of carbon monoxide and NOx (nitrous oxides). NOx emmissions peak at an air/fuel ratio of 16:1 and are thus a feature of lean, part throttle economy mixtures seen in most road cars today but rarely, if ever, in race cars, as the elevated in cylinder temperatures which cause the production of NOx - an unavoidable consequence of burning lean mixtures - would rapidly damage a race engine at full load and full throttle, where they spend much of their time. Correctly tuned engines, particularly if they are injected and have a well mapped ECU and lambda sensor oxygen monitoring of the exhaust gasses, will output relatively low levels un-burnt hydrocarbons with air fuel ratios in the range of 12:1 to 18:1. Perversely, hydrocarbon emmissions are at the lowest level at an air/fuel ratio of 16:1 - exactly when NOx levels peak. Carbon monoxide output is at it's worse at low air fuel ratios but fall rapidly between 12:1 amd 14.7:1 - the chemically correct 'perfect' or stoichiometric ratio. CO falls further as the air/fuel ratio increases towards about 17:1 and then decreases very slowly. Even in the greenest road car, the EGR system is bypassed on full throttle - i.e. EGR is only operational on part throttle at low load when sufficient vacuum exists in the inlet manifold, so in a race conditions, with lots of WOT operation, EGR would have very little impact. Race engines are generally tuned (if the regs allow) for an air/fuel ratio that delivers the most power - which is somewhat less than 14.7:1, so the main undesirable product emmitted from the exhaust of a race car is carbon monoxide. NOx will be very low from a race engine and hydrocarbons will be no worse than a lean burn engine running at a 20:1 air/fuel ratio. Currently most successful way to reduce all of these emmissions is a 3-way catalytic converter - but they only work properly on all three problem emmissions with air/fuel ratios of between 14.6 and 14.8:1. So if you want to find a solution to a problem, the problem is how to convert the predominent pollutent from race engines - carbon monoxide - into something less poisonous, and preferably not carbon dioxide as that is a 'greenhouse gas', in case you needed reminding! One further objective would be that the conversion of carbon monoxide should not increase back-pressure in the exhaust system. Good luck! Last edited by phoenix; 7 Dec 2008 at 00:12. |
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7 Dec 2008, 00:20 (Ref:2349275) | #20 | |||
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I guess you are mainly considering petrol racing engines? |
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7 Dec 2008, 00:45 (Ref:2349285) | #21 | ||
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One of the silliest (although it got round the emission problem) systems was fitted to various Jap vehicles where it simply diluted the exhaust gasses by pumping air into the exhaust manifold. It certainly did the aftermarket exhaust boys a favor by flogging new silencers when they exploded !
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
7 Dec 2008, 01:04 (Ref:2349289) | #22 | ||
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Adam. Diesel engines are a different kettle of fish. Petrol engines run on "average" about 10% EGR whereas a diesel is 30 + % and can run up to 50%.
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
7 Dec 2008, 08:06 (Ref:2349408) | #23 | |
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oops
Last edited by phoenix; 7 Dec 2008 at 08:09. |
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7 Dec 2008, 08:07 (Ref:2349409) | #24 | ||
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In petrol engines, NOx emmissions are very low at air/flow ratios commonly used for maximum power, and EGR systems are bypassed at full throttle and load - so is EGR relevent to (petrol powered) motorsport? IMHO - no. |
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7 Dec 2008, 10:53 (Ref:2349467) | #25 | |||
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I agree that heat exchange between the fuel and the EGR isn't likely to help much. |
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