Covering the basics through advanced operation of spark-ignition and diesel engines.
Written by one of the most recognized and highly regarded names in internal combustion engines this trusted educational resource and professional reference covers the key physical and chemical processes that gov...
- werkelijk p.V diagram wijkt af van theoretische
vergelijkingskringloop
- spoellus:
onderstellen stationaire
stroming, onsamendrukbaar
fluïdum
vanuit punt A (atmosfeer) tot
punt C (cilinder)
c 2A cC2
p A + ρ A + ρ A gh A = p C + ρC + ρ C gh C + Δp l
2 2
↓
c2
∼ k ⋅ρ
2
• bij aanzuigen pC < pA
• pC ≈ pA bi j open gasklep en n <
• pC << pA bi j gesloten gasklep en n > (ottomotor)
(gelijkaardige redenering voor uitlaat !) pC > pA
- in cilinder op elk ogenblik pA dx = dWi
F
of dWi = pdv
en Wi = ∫ pdV en Wi = p i ⋅ VS
werk. kringloop slide1.
,2.1. COMPRESSIE, VERBRANDING, EXPANSIE
- bij IS : mengsel verse lading en restgas 70 à 180 °C
en 0,2 à 1 bar bij zelfaanzuiging otto
zelfaanzuiging diesel ≈ 1 bar
opgeladen motoren 1,5 à max 4 bar
(1,5 → PW ; 4 → scheepsdiesels)
- vanaf IS compressie volgens polytrope transf pVm = Cte
voor nabijgelegen punten 1 en 2 → p1 V1m = p 2 V2m
log p1 − log p 2
m= verloop zie figuur
log V2 − log V1
1) verandering van 6 over de cyclus
cp-cV = R
R
→ 6 cV - c V = R → κ = 1+
cV
c p = 6 cV
cV - ↑ met T ↑
- cV groter voor 3-atomige gassen dan voor 2-
atomige
dus cV ↑ met 8 ↓ (voor 8 > 1)
dus 6 ↓ met T ↑
6 ↓ als omzetting naar 3-atomige gassen (CO2,
H2O, verbranding)
werk. kringloop slide2.
, 2) herhaling enkele basisformules thermodynamica
dQ = dU + dW
met dQ > 0 als warmte naar gas
dW > 0 als arbeid afgegeven
dW = pdV-dR
inwendige irreversibele wrijvingsverliezen als warmte aan
het gas toegevoerd waardoor entropie toeneemt
TdS = dQ + dR
Vorige formules dan :
dQ = dU + pdV-dR
dQ + dR = dU + pdV
TdS = dU + pdV
werk. kringloop slide3.
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