Siin eelnevalt ironiseeriti natuke aga kui vajutad linki siis saad aru ka miks.
http://www.ekoautoilijat.fi/tekstit/kuva..._Camry.htm
http://www.ekoautoilijat.fi/tekstit/kuva..._Volvo.htm
Moottori laskuri
Kaikki oikeudet pidätetään. Copyright Xylogas OY
Emme vastaa arvojen oikeellisuudesta, käyttö omalla vastuulla.
männän iskunpituus: +- = mm
Kierrosluku rpm: +- = rpm
m/s (maksiminopeus kierron puolivälissä. Puukaasulle turvalliset arvot n. 15m/s)
Männän halkasija: +- = mm
Sylinteri luku määrä: +- = kpl
L (moottorin tilavuus)
Kaasun koostumus ja siitä saatava teoreettinen teho:
Kaasun vetypitoisuus: +- =
Kaasun häkäpitoisuus: +- =
Kaasun metaanipitoisuus: +- = (maakaasu, biokaasu)
Kaasun propaanipitoisuus: +- = (nestekaasu)
Kaasun heksaanipitoisuus: +- = (~bensa, FAO:heating value of a stoichiometric mixture of petrol and air (about 3800 kJ/m³ ))
Kaasun lämpöarvo: kJ/m³
Stoikiometrisen seoksen lampöarvo: kJ/m³ (tehontiputus vertaamalla tämä vs 3800kJ/m³ ~0.65)
Kaasun osuus stokiometrisessä seoksessa: %
moottorin täytösaste: +- = täysteholla (FAO:0.7-0.9,gengas.nu:0.94 ottokone, 0.82 dieselsytytys, ahto yli 1)
Laitteiston vastus: +- = mm /H2O (Mittaa imusarjasta kaasu pohjassa. 1mm/hg= 12.9mm/H2O)
Moottorin hyötysuhde: +- = (bensakoneet 20% paikkeilla, diesel jopa 35%, ks teksti alla.)
Tahtikerroin: (0.5 = nelitahtinen, 1= kaksitahti)
Moottorin stokiometrinen lämpöteho: kW
Teoreettinen akseliteho: kW
Moottorin puristussuhde r X:1 +- = :1 (ks teksti alla.)
kaasuvakio g +- =
mekaniikka hyötysuhde +- =
Teoreettinen hyötysuhde: %
Engine efficiency
h = 1 - 1/rvg-1
The compression ratio of the engine is rv. Actually, this is a volume ratio.rv = Vbottom/Vtop
The g parameter is the ratio of the specific heats. In practical terms, the higher the g, the higher the efficiency.
A gas such as helium or argon, composed only of atoms, has the highest g possible, 1.67, O2 and N2 molecules has a g of 1.4.
Fuel vapor has g less than that of air. The mixture of air and gasoline vapor inducted into the engine has a g of about 1.35.
As this mixture is compressed and heated during the compression stroke, its g drops to about 1.33. Upon combustion
(when the piston is near its top position), the fuel is oxidized to CO2 (and some CO) and H2O, and g drops further.
It drops into the 1.20-1.25 range. The overall, effective g for the whole cycle for use in the efficiency equation above is about 1.27.
The rule of thumb is: the greater the complexity of the molecules, the lower the g. The lower limit is 1.
Argon and helium atoms only translate, air molecules translate and rotate (about 2 of their axes).
Molecules of fuel vapor have a lot of opportunity to vibrate, even at room temperature. The products of combustion vibrate.
However, only the translation of the molecules PUSHES the piston.
A lean engine has a cooler combustion process and more air relative to fuel. Thus, its g is higher, and its h is greater.
Plug g = 1.27 into the efficiency equation above, assume rv = 10, and you get h = 0.46. Multiply this by about 0.75 to account
for real cycle effects (such as the time it takes to burn, heat losses to the coolant, and exhaust valves that open before the
piston fully reaches bottom position) and you have h = 0.35. This is the efficiency of using the chemical energy of the fuel
to push the pistons. Multiply this by the mechanical efficiency of the engine which accounts for the mechanical friction in
the engine and for the air pumping work that has to be done, and you have the final, or overall efficiency of the engine.
Of course the mechanical efficiency varies with driving conditions. The higher the RPM of the engine, the greater the friction loss.
The more closed the throttle, the higher the pumping loss. For typical US driving, the resultant overall efficiency of the engine
is about 20%. Add the tranny and real axle mechanical friction losses and the drain of a few essential accessories, and you arrive
at a 15% fuel-to-wheel efficiency for the typical auto driven in the US.
We need new cycles put into practical use. An example is the Atkinson cycle. This has a smaller compression ratio than expansion ratio.
This means TC is reduced since the burnt gas cool as they expand, making the cycle efficient. We throw away less waste heat via the exhaust.
Run the engine at optimum conditions, meaning low friction and low pumping work. Try to approach the "pushing-the-pistons" efficiency of 35%.
This already is happening in some stationary piston engines -large, slow, piston engines used at pipeline compressor stations.
There are indications that thermal efficiency reaches a maximum at a compression ratio of about 17:1 for gasoline fuels in an SI engine [23]
Compression Octane Number Brake Thermal Efficiency
Ratio Requirement ( Full Throttle )
5:1 72 -
6:1 81 25 %
7:1 87 28 %
8:1 92 30 %
9:1 96 32 %
10:1 100 33 %
11:1 104 34 %
12:1 108 35 %
Modern engines have improved significantly on this, and the changing fuel specifications and engine design should see more improvements,
but significant gains may have to await improved engine materials and fuels.
Stoichiometric combustion ( air-fuel ratio = 14.7:1 for a typical non-oxygenated gasoline ) is neither maximum power - which occurs around
air-fuel 12-13:1 (Rich), nor maximum thermal efficiency - which occurs around air-fuel 16-18:1 (Lean).
A 12:1 CR gasoline engine at 1500 rpm would have a flame speed of about 16.5 m/s, and a similar hydrogen engine yields 48.3 m/s, but such
engine flame speeds are also very dependent on stoichiometry.
puukaasu vain kaksiatomisia molekyylejä = korkeampi puristushyötysuhde, vetyä mahdollisesti korkea palonopeus, korkea oktaaniluku = korkea puristus
palaessa moolit vähenee = pidempi työtahti ~Atkins.
Laenatud Soome foorumist. Loodan,et nad ei pahanda.