Internal Combustion EnginesDiesel Engines

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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. Schäfer (eds): “Internal Combustion Engines: basics, components, systems and perspectives”, SAE International, Warrendale, Pa.2004

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Combustion in DIESEL engines

• PHYSICAL DELAY + CHEMICAL DELAY = IGNTION DELAY

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REDUCE IGNTION DELAY:

• BETTER SPRAY, HIGHER PRESSURE OF INJECTION

• BETTER AIR FLOW IN THE ENGINE

• BETTER FUEL

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• Common - Rail

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• 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 PROPULSÃO DIESEL EM PESADOS

ANFITEATRO AM, 17H-18H30

FRIDAY, 11 DECEMBER 2015

Eng. José Manuel Meira Afonso

gestor da HYDRAPLAN

7 de dezembro – 16:30 às 18:00; sala FA2

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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

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Quish and Swirl

Squish & Swirl

http://www.renault.pt/gama/veiculos-de-passageiros/scenic/novo-scenic/motorizacoes-energy/

Internal Combustion EnginesDiesel Engines

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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.ª revolução: sistema Common Rail

Componentes de sistemas common rail

Bosch: 1,100 and 2,200 bar; Denso: 2500 bar; futuro: 3000 bar

Pressão de injecção…a caminho dos 3000 bar

Evolução do n.º de injecções por ciclo (FIAT MultiJet diesel technology)

Injecção 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. Schäfer (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

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Engine Maps

Engine efficiency map

53

Internal Combustion EnginesDiesel Engines

Tiago Farias

emissions

55

Controlo de emissões

(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 homologação NEDC

www.dieselnet.com (g/km)

Normas EURO Diesel e gasolina

PM e Nox….. Uma dor de cabeça!

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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…

59

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

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Pollutants in Diesel Engines

• EGR (Exhaust gas recirculation)

• Particle filters

• NOx traps

• CO and HC oxidation catalytic converters

• Particles (PM)

• HC, CO,

• NOx

• CO2

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Particle filters

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Filtro de partículas (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