--- In [EMAIL PROTECTED], "harmonseaver" <[EMAIL PROTECTED]> wrote: > --- In [EMAIL PROTECTED], Christopher Witmer <[EMAIL PROTECTED]> wrote: > > What is the significance of diesel engine compression ratio in a > > cogeneration context? I have heard that with cogeneration, the higher > > the compression ratio the better. Can anyone tell me why? Is it because > > a higher compression ratio means more heat? And how high is "high" for > > readily available engines? I think my source said something to the > > effect that Cummins has some engines with relatively high compression > > ratios, beyond 20:1. Also, how easy is it to increase an engine's > > compression ratio? I seems to me that one could damage one's engine > > trying, if one was careless. > > I don't think it makes any difference in "cogeneration", per se, > the engines still run at the same operating temperature. Perhaps what > you are thinking of is that engines running on biomass gasifiers need > much higher compression, which is why diesels are used. Many diesels > have 25:1 compression, although some newer ones like the VW TDI's have > only about 18:1. > You can quite easily raise compression ratio by having the > cylinder head milled off a bit, although that needs to be done after > careful computation of the deck height of the pistons in the cylinder > and the actual volume of the compression chamber in the head. For some > gasoline engines, high compression pistons are available, although > those are probably only going to take it to 11:1 or 12:1. Even for > ethanol you want at least 13:1. > You can't raise it much more than that for a petrol engine, since > the piston crowns and connecting rods aren't strong enough. Bearings > also might be a problem. Better to use a diesel and convert it to > spark if necessary.
The easiest way to raise the 'effective' compression ratio is to add a turbo-charger. The standard practice, when raising the horsepower/efficiency output of an engine, is to lower the compression ratio, and compensate with a turbo-charger. It is the cylinder pressure that we are really after. 25-35 PSI in the intake manifold will drastically increase output. http://www.dieselinjection.net http://www.dieselinjection.net/articles.html These sites will tell you more than you ever wanted to know about high-horsepower Diesels. Motie ------------------------ Yahoo! Groups Sponsor ---------------------~--> Sell a Home for Top $ http://us.click.yahoo.com/RrPZMC/jTmEAA/MVfIAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
