Internal Combustion EnginesDiesel Engines
Tiago Farias
Diesel injection, impacts on efficiency, emissions, power
CICLO A 4 TEMPOS
Intake Compression Expansion ExhaustInjection
Combustion
3
Combustion in DIESEL engines
Combustion of a spray: Injection
Dispersion/mixture with air
Evaporation
Auto-ignition
Burn of fuel
Needs TIME!
Effective work
Real Diesel Cycle
Lost work
What about the hid? Diesel
What about the hid? Diesel vs SI, same Rc
What about the hid? Diesel , fast engine
What about the hid? Diesel vs SI
11
Combustion in DIESEL engines
Combustion of a spray: Injection
Dispersion/mixture with air
Evaporation
Auto-ignition
Burn of fuel
Needs TIME!
Typical values
Engine typeMax. Speed
(rpm)Mean piston speed (m/s)
Racing engine (Formula 1) 18 000 25
Small engines (two-stroke) 20 000 19
Motorcycle engines 13 500 19
Car SI engines 7 500 20
Car Diesel engines 5 000 15
Truck Diesel engines 4 200 14
Larger high-speed Diesel engines 2 200 13
Medium high-speed engines (Diesel) 1 200 10
Crosshead engines (two-stroke Diesel) 200 8
Maximum rotational speed and mean piston speed (approx.) at rated revs of modern enginesTaken from :R. Van Basshuysen and F. Schfer (eds): Internal Combustion Engines: basics, components, systems and perspectives, SAE International, Warrendale, Pa.2004
15
Combustion in DIESEL engines
PHYSICAL DELAY + CHEMICAL DELAY = IGNTION DELAY
16
REDUCE IGNTION DELAY:
BETTER SPRAY, HIGHER PRESSURE OF INJECTION
BETTER AIR FLOW IN THE ENGINE
BETTER FUEL
17
Common - Rail
18
Common Rail HDi: Grupo PSA
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Common Rail HDi: PSA
Medium engine, l = 15cm, bore = 12 cm Vc = 1,7 litre (bus)Ue = 12 m/sNmax= 12*60/2/0,15 = 2400 rpm
Large engine, l = 35 cm, bore = 25 cm Vc = 17 litre (ship)Ue = m/s Nmax= 10*60/2/0,35 = 860 rpm
Small engine, l = 7,7 cm, bore = 8,6 cm Vc = 0,45 litre (car)Ue = m/sNmax= 14*60/2/0,077 = 5400 rpm
SISTEMAS DE PROPULSO DIESEL EM PESADOS
ANFITEATRO AM, 17H-18H30
FRIDAY, 11 DECEMBER 2015
Eng. Jos Manuel Meira Afonso
gestor da HYDRAPLAN
7 de dezembro 16:30 s 18:00; sala FA2
23
Combustion in DIESEL engines
Combustion of a spray: Injection
Dispersion/mixture with air
Evaporation
Auto-ignition
Burn of fuel
Needs TIME!
Swirl
SQUISH
Swirl
Quish and Swirl
28
Quish and Swirl
Squish & Swirl
http://www.renault.pt/gama/veiculos-de-passageiros/scenic/novo-scenic/motorizacoes-energy/
http://www.renault.pt/gama/veiculos-de-passageiros/scenic/novo-scenic/motorizacoes-energy/
Internal Combustion EnginesDiesel Engines
Tiago Farias
Diesel injection, impacts on efficiency, emissions, power
32
Combustion: Diesel engines
Diesel combustion
C10H18 + a (O2+3,76N2) -> 10 CO2 + yreH2O + zre N2+ a HC + b CO + c NOx (NO;NO2) + particles
CO2 emissions ~ 3.17 kg CO2 /kgfuel
- Particles
- HC unburned
- CO incomplete combustion
- NOx N2 + O2 + high Temp.
36
Combustion in DIESEL engines
Combustion of a spray: Injection
Dispersion/mixture with air
Evaporation
Auto-ignition
Burn of fuel
Needs TIME!
Physical delay: dispersion, evaporation, mixture with air
Chemical delay: Arrhenius term
Cetane number: measures how fast combustion takes place.
2. revoluo: sistema Common Rail
Componentes de sistemas common rail
Bosch: 1,100 and 2,200 bar; Denso: 2500 bar; futuro: 3000 bar
Presso de injecoa caminho dos 3000 bar
Evoluo do n. de injeces por ciclo (FIAT MultiJet diesel technology)
Injeco Diesel: cada vez mais complexa
Lambda in Diesel Engines
Thermal limite vs smoke limit
Lambda in Diesel Engines Thermal limite vs smoke limit
For same speed:If l decreases:
- more fuel is injected- Be, pe increases- efficiency increases, - temperature increases, and increases more forsmall S/V (large engines)
If l starts approaching one- difficulties in burning all fuel
Lambda in Diesel Engines Thermal limite vs smoke limit
Minimum l depends on:- S/V- Turbocharging pressures- Engine cooling system- How you use the engine (constant load)- The engine materials
For large engines, the thermal limit appears first (low S/V)
For small engines, with high squish and swirl, the smoke limit is the limit
Typical valuesEffective mean pressure of modern enginesTaken from :R. Van Basshuysen and F. Schfer (eds): Internal Combustion Engines: basics, components, systems and perspectives, SAE International, Warrendale, Pa.2004
Engine typeEffective Mean Pressure (bar)
up to
Motorcycle engines 12
Racing engines (Formula 1) 16
Car SI engines (without turbocharger) 13
Car SI engines (with turbocharger) 17
Truck Diesel engines (with turbocharger)
22
Car Diesel engines (with turbocharger)
20
Larger high-speed Diesel engines 30
Medium-speed Diesel engines 25
Crosshead engines (two-stroke Diesel)
15
Internal Combustion EnginesDiesel Engines
Tiago Farias
Engine Maps
Engine efficiency map
53
Internal Combustion EnginesDiesel Engines
Tiago Farias
emissions
55
Controlo de emisses
(HC, CO, NOx, PM)
NEDC ciclo de velocidade Europeu
0
25
50
75
100
125
0 100 200 300 400 500 600 700 800 900 1000 1100 1200
t (s)
v (
km
/h) ECE
EUDC
Ciclo standard de homologao NEDC
www.dieselnet.com (g/km)
Normas EURO Diesel e gasolina
PM e Nox.. Uma dor de cabea!
58
Pollutants in Diesel Engines
EGR (Exhaust gas recirculation)
Particle filters
NOx traps /SCR
CO and HC oxidation catalytic converters
Particles (PM)
HC, CO,
NOx CO2
Control combustion or
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Emissions: Diesel engines
Diesel combustion
C12H23 + a (O2+3,76N2) -> 12 CO2 + yreH2O + zre N2+ a HC + b CO + c NOx (NO;NO2) + particles
CO2 emissions ~ 3.16 kg CO2 /kgfuel
- Particles
- HC unburned
- CO incomplete combustion
- NOx N2 + O2 + high Temp.
EGR Exhaust Gas Recirculation
EGR Exhaust Gas Recirculation
65
Pollutants in Diesel Engines
EGR (Exhaust gas recirculation)
Particle filters
NOx traps
CO and HC oxidation catalytic converters
Particles (PM)
HC, CO,
NOx CO2
66
Particle filters
67
68
Filtro de partculas (FAP - Peugeot)
SCR Selective Catalytic Reduction
DPF + SCR
72
SCR Selective Catalytic Reduction
Internal Combustion EnginesDiesel Engines
Tiago Farias
Diesel injection, impacts on efficiency, emissions, power
