Diesel injection, impacts on efficiency, emissions, power Tiago Farias

Transcription

1 Internal Combustion Engines Diesel Engines Diesel injection, impacts on efficiency, emissions, power Tiago Farias

2 CICLO A 4 TEMPOS Combustion Intake Compression Injection Expansion Exhaust

3 Combustion in DIESEL engines Combustion of a spray: Injection Dispersion/mixture with air Evaporation Auto-ignition Burn of fuel Needs TIME! 3

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6 Real Diesel Cycle Effective work Lost work

7 What about the h id? Diesel

8 What about the h id? Diesel vs SI, same Rc

9 What about the h id? Diesel, fast engine

10 What about the h id? 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! 11

12 Typical values Maximum rotational speed and mean piston speed (approx.) at rated revs of modern engines Taken from : R. Van Basshuysen and F. Schäfer (eds): Internal Combustion Engines: basics, components, systems and perspectives, SAE International, Warrendale, Pa.2004 Engine type Max. Speed (rpm) Mean piston speed (m/s) Racing engine (Formula 1) Small engines (two-stroke) Motorcycle engines Car SI engines Car Diesel engines Truck Diesel engines Larger high-speed Diesel engines Medium high-speed engines (Diesel) Crosshead engines (two-stroke Diesel) 200 8

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15 Combustion in DIESEL engines PHYSICAL DELAY + CHEMICAL DELAY = IGNTION DELAY 15

16 REDUCE IGNTION DELAY: BETTER SPRAY, HIGHER PRESSURE OF INJECTION BETTER AIR FLOW IN THE ENGINE BETTER FUEL 16

17 17 Common - Rail

18 18 Common Rail HDi: Grupo PSA

19 19 Common Rail HDi: PSA

20 Medium engine, l = 15cm, bore = 12 cm Vc = 1,7 litre (bus) Ue = 12 m/s Nmax= 12*60/2/0,15 = 2400 rpm Small engine, l = 7,7 cm, bore = 8,6 cm Vc = 0,45 litre (car) Ue = m/s Nmax= 14*60/2/0,077 = 5400 rpm Large engine, l = 35 cm, bore = 25 cm Vc = 17 litre (ship) Ue = m/s Nmax= 10*60/2/0,35 = 860 rpm

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22 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

23 Combustion in DIESEL engines Combustion of a spray: Injection Dispersion/mixture with air Evaporation Auto-ignition Burn of fuel Needs TIME! 23

24 Swirl

25 SQUISH

26 Swirl

27 Quish and Swirl

28 28 Quish and Swirl

29 Squish & Swirl

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31 Internal Combustion Engines Diesel Engines Diesel injection, impacts on efficiency, emissions, power Tiago Farias

32 Combustion: Diesel engines Diesel combustion C 10 H 18 + a (O 2 +3,76N 2 ) -> 10 CO 2 + y re H 2 O + z re N 2 + a HC + b CO + c NO x (NO;NO 2 ) + particles CO 2 emissions ~ 3.17 kg CO 2 /kg fuel - Particles - HC unburned - CO incomplete combustion - NOx N2 + O2 + high Temp. 32

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36 Combustion in DIESEL engines Combustion of a spray: Injection Dispersion/mixture with air Evaporation Auto-ignition Burn of fuel Needs TIME! 36

37 Physical delay: dispersion, evaporation, mixture with air Chemical delay: Arrhenius term Cetane number: measures how fast combustion takes place.

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40 2.ª revolução: sistema Common Rail

41 Componentes de sistemas common rail Bosch: 1,100 and 2,200 bar; Denso: 2500 bar; futuro: 3000 bar

42 Pressão de injecção a caminho dos 3000 bar

43 Injecção Diesel: cada vez mais complexa Evolução do n.º de injecções por ciclo (FIAT MultiJet diesel technology)

44 Lambda in Diesel Engines Thermal limite vs smoke limit

45 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 for small S/V (large engines) If l starts approaching one - difficulties in burning all fuel

46 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

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48 Effective mean pressure of modern engines Taken from : R. Van Basshuysen and F. Schäfer (eds): Internal Combustion Engines: basics, components, systems and perspectives, SAE International, Warrendale, Pa.2004 Typical values Engine type Effective 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

49 Internal Combustion Engines Diesel Engines Engine Maps Tiago Farias

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53 53 Engine efficiency map

54 Internal Combustion Engines Diesel Engines emissions Tiago Farias

55 Controlo de emissões (HC, CO, NOx, PM) NEDC ciclo de velocidade Europeu 125 EUDC v (km/h) ECE t (s) 55

56 Normas EURO Diesel e gasolina Ciclo standard de homologação NEDC (g/km)

57 PM e Nox.. Uma dor de cabeça!

58 Pollutants in Diesel Engines Particles (PM) HC, CO, NO x CO 2 Control combustion or EGR (Exhaust gas recirculation) Particle filters NOx traps /SCR CO and HC oxidation catalytic converters 58

59 Emissions: Diesel engines Diesel combustion C 12 H 23 + a (O 2 +3,76N 2 ) -> 12 CO 2 + y re H 2 O + z re N 2 + a HC + b CO + c NO x (NO;NO 2 ) + particles CO 2 emissions ~ 3.16 kg CO 2 /kg fuel - Particles - HC unburned - CO incomplete combustion - NOx N2 + O2 + high Temp. 59

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62 EGR Exhaust Gas Recirculation

63 EGR Exhaust Gas Recirculation

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65 Pollutants in Diesel Engines Particles (PM) HC, CO, NO x CO 2 EGR (Exhaust gas recirculation) Particle filters NOx traps CO and HC oxidation catalytic converters 65

66 66 Particle filters

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68 68 Filtro de partículas (FAP - Peugeot)

69 SCR Selective Catalytic Reduction

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72 72 DPF + SCR

73 SCR Selective Catalytic Reduction

74 Internal Combustion Engines Diesel Engines Diesel injection, impacts on efficiency, emissions, power Tiago Farias