Northeast States CLEAN AIR ACADEMY

Transcript Northeast States CLEAN AIR ACADEMY

Advanced Mobile Source Training Course MS 201 - Diesel

Overview – Diesel Engine Technology • How the engine works – compression ignition combustion process, operating cycle, fuel/air mixture via fuel injection dynamic • Engine system components – fuel injection, common rail accumulator, unit injector, governor, altitude / temperature / cold start compensator, turbocharger, EGR • Fuel consumption • Emissions © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 2

Heavy-duty Engine Features

• Engine power • Specific power output – high torque • Operational safety • Production costs • Economy - fuel • Economy of operation • Reliability © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 3

Four-Stroke Diesel Engine Schematic (without auxiliary units)

1 2 10 11 3 12 7 8 5 15 6 9 14 13

Fig 1

1 Camshaft 2 Valves 3 Piston 4 Fuel Injection System 5 Cylinder 6 Exhaust-gas Recirculation 7 Intake Manifold 8 Turbocharger 9 Exhaust pipe 10 Cooling system 11 Connecting rod 12 Lubrication 13 Cylinder block 14 Crankshaft 15 Flywheel 4

4-Stroke Diesel Engine Cycle

Fig 2 a Induction stroke b Compression stroke c Ignition stroke d Exhaust stroke

1 Inlet-valve camshaft 2 Fuel injector 3 Inlet valve 4 Exhaust valve 5 Combustion chamber 6 Piston 7 Cylinder wall 8 Connecting rod 10 Exhaust-valve camshaft

TDC Top dead center / BDC Bottom dead center

a Crankshaft angle of rotation d Bore M Turning force s Piston stroke V c Compression volume V h Swept volume

Temperature Rise During Compression

Fig 3

TDC Top dead center BDC Bottom dead center

4-Stroke Diesel Engine Valve Timing

Fig 4

EO Exhaust opens EC Exhaust closes SOC Start of combustion IO Inlet opens IC Inlet closes IP Injection Point TDC Top Dead Center BDC Bottom Dead Center

Fig 5

EO Exhaust opens EC Exhaust closes SOC Start of combustion IO Inlet opens IC Inlet closes TDC Top dead center BDC Bottom dead center p U Ambient Pressure p L Charge air pressure p Z Maximum cylinder pressure V c Compressed volume V h Swept volume W M Useful work W G Work during gas exchange turbocharger / supercharger

Pressure vs. Crankshaft Rotation (p-a diagram) for Turbocharged / Supercharged Diesel Engine

Fig 6

EO Exhaust opens EC Exhaust closes SOC Start of combustion IO Inlet opens IC Inlet closes TDC Top dead center BDC Bottom dead center p U Ambient pressure P L Charging pressure P Z Maximum cylinder pressure

Overall Efficiency Diesel vs. Gasoline is Due to Three Factors • Higher compression ratio (giving a larger area on the p.V indicator diagram) • Greater excess air (made possible by heterogeneous internal air/fuel mixing) • Absence of throttle flap – and consequently no throttle-related losses in the part-load range • Figure 7 10 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Efficiency loss of motor-vehicle diesel engine at full power

Fig 7

Diesel engines vary greatly in size and application for which they are designed. Therefore, their levels of efficiency differ significantly as well. The best efficiency levels are achieved by large-scale slow-moving engines.

η th Theoretical efficiency (alters in relation to the compression ratio ‘E’ and the excess air factor ‘y’ η g Efficiency of the high-pressure work η m process Mechanical efficiency

Undivided Combustion Chamber (direct-injection engines) • Direct-injection into combustion chamber piston crown recess – nozzles • Figure 8

shaped • Fuel atomization, heating, vaporization, and mixing with air in rapid succession • Exacting demands on air and fuel induction • Intake port imparts air vortex • Combustion chamber shape imparts swirl • High injection pressure (2000 bar) and multi-hole © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 12

Direct injection

2 1 3

Fig 8

1 Multihole injector 2

piston recess 3 Glow plug 13

Basic Principles of Diesel Fuel Injection • Excess-air factor – λ (lambda) • Lambda levels within heterogeneous mixture • Start of injection • Start of delivery • Injection duration • Specific fuel consumption • Specific NOx, HC and PM • Injection pattern • Figure 9 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 14

Progress of combustion in a direct-injection test engine with a multihole nozzle

a b

Fig 9

Special engines with glass inserts and mirrors allow the fuel injection and combustion process to be observed.

c d

The times are measured from the start of spontaneous combustion

a 200 μs b 400 μs c 522 μs d 1,200 μs

Excess-Air Factor

(Lambda)

• • • • λ = air mass / fuel mass stoichiometric 1 ratio λ = 1: intake air mass = to theoretical air mass required to burn all of the fuel injected λ < 1: intake air mass is less than the amount required and therefore the mixture is rich λ > 1: intake air mass is greater than the amount required and therefore the mixture is lean 1 The stoichiometric ratio indicates the air mass in kg required to completely burn 1 kg of fuel. For diesel fuel, this is ~ 14.5

Lambda Levels in Diesel Engine

• Always overall excess air • Full load λ = 1.15 to 2.0

• Idle λ > 10 • Heterogeneous mixture allows for combustion over complete range • Homogeneous mixtures not possible with FI • Spontaneous ignition and pollutant formation are due to localized λ values • Droplet (vapor envelope) λ = 0.3 to 1.5

Air-fuel ratio curve for a static fuel droplet

Fig 10

d Droplet diameter (approx. 2 – 20 μm)

Air-fuel ratio patterns for a moving fuel droplet

a 1 2 3 b 1 2 3 4 4

Fig 11 a Low relative velocity b High relative velocity

1 Flame zone 2 Vapor envelope 3 Fuel droplet 4 Air flow 19

Injection Timing Is Important for Emissions, Noise and Efficiency • High NOx under advanced injection • High HC under retarded injection • Advanced better for cold start • Retarded better for full load • Figures 12, 13 • Direct-injection commercial-vehicle engines: – No load: 4 – 12 o crankshaft before TDC – Full load: 3 - 6 o crankshaft before TDC to 2 o crankshaft after TDC © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 20

Distribution patterns for NOx and HC emissions plotted against start of ignition for a commercial vehicle without EGR

Fig 12

Example of an Application:

a N Optimum start of injection for emissions at no load, as NOx emissions are lower under these conditions a V Optimum start of injection for emissions at full load, as HC emissions are lower under these conditions

Start of injection versus engine speed and load for a car engine started from cold and at normal operating temperature

Fig 13

Specific fuel consumption b e in g/kWh vs. start of injection and injection duration

Fig 14

Engine: 6-cylinder diesel Commercial-vehicle engine With common-rail fuel-injection

Operating conditions: N = 1400 rpm, 50% power In this example, the injection duration is varied by variation of the injection pressure

Specific nitrogen oxides (NOx) emission in g/kWh vs. start of injection and injection duration

Fig 15

Engine: 6-cylinder diesel Commercial-vehicle engine With common-rail fuel-injection

Operating conditions: N = 1400 rpm, 50% power In this example, the injection duration is varied by variation of the injection pressure

Specific emission of unburned hydrocarbons (HC) in g/kWh vs. start of injection and injection duration

Fig 16

: 6-cylinder diesel Commercial-vehicle engine With common-rail fuel-injection

Operating conditions: N = 1400 rpm, 50% power In this example, the injection duration is varied by variation of the injection pressure

Specific soot emission in g/kWh vs. start of injection and injection duration

Fig 17

: 6-cylinder diesel Commercial-vehicle engine With common-rail fuel-injection

Operating conditions: N = 1400 rpm, 50% power In this example, the injection duration is varied by variation of the injection pressure

Injection Pattern Affects Emissions

• Pre-injection reduces NOx and noise • Positive pressure gradient main injection reduces NOx • Two-stage pressure gradient main injection reduces NOx and soot • Constant high pressure during main injection reduces soot • Post-injection immediate after main reduces soot • Retarded post-injection as reducing fuel raises exhaust gas temperature for particle filter regeneration • Figure 18 27 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Injection patterns Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7

Fig 18

Adjustments aimed at low NOx levels require starts of injection close to the TDC at maximum load (engines without EGR). The fuel delivery point is significantly in advance of the start of injection and is dependent on the injection system.

Legend continues on next slide

Fig 18 Legend 1 2 3 4 5 6 Pre-ignition (PI) phase Main injection (MI) phase Steep pressure gradient (common-rail system) Two-stage pressure gradient (UPS with two-stage solenoid valve) (dual-spring nozzle holder assemblies can produce a bath-tub needle lift curve [but not pressure gradient]. This reduces combustion noise but not always soot emission levels Gradual pressure gradient (conventional fuel injection) Gradual pressure drop (in-line and distributor injection pumps) © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 7 8 9 Steep pressure drop (UIS, UPS, slightly less steep with common rail) Advanced post injection (PO) Retarded post injection Ps Peak pressure Po Injector opening pressure b v Duration of combustion for main injection pressure Duration of combustion for pre-injection phase ZV Ignition lag for main injection phase without pre-injection 29

Engine System Components – Cylinder Charge Systems • Air filters (99.95% eff.) Maintenance interval ~ 60,000 miles otherwise backpressure of 20 mbar • Turbocharger with intercooler – increased engine power from same engine capacity. Lower PM and slightly lower NOx • Exhaust gas recirculation with intercooler – decreased NOx. Commercial engines with VTG TC for pressure differential • Swirl flap – impart swirl to inlet valve air for better in cylinder air/fuel mixing • Figures 19, 20, 21, 22 30 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Air Filters

1 5 4 3 2 6

Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 Fig 19a : 1 Air Outlet; 2 Air Inlet; 3 Filter Element; 4 Supporting Tube; 5 Housing; 6 Dual collector © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 Fig 19b : The arrows indicate the direction of the intake air 31

Commercial-vehicle turbocharger with twin-flow turbine

4 5 6 1 2 7 11 3 8 9 12 10

Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7

Fig 20a

: 1 Compressor housing 2 Centrifugal Compressor 3 Intake air 4 Compressed intake air 5 Lubricant inlet 6 Turbine housing 7 Turbine 8 Exhaust outflow 9 Bearing housing 10 Exhaust inflow 11 Shaft 12 Lubrication return outlet 32 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Turbocharger with wastegate

9 7 6 3 5 1 2 8 4

Fig 20b

: 1 Charge-pressure actuator 2 Vacuum pump 3 Pressure actuator 4 Turbocharger 5 Wastegate (bypass valve) 6 Exhaust flow 7 Intake air flow 8 Turbine 9 Centrifugal compressor 33

Power and torque curve for a turbocharged engine compared with a conventionally aspirated engine

Fig 21 a Conventionally aspirated engine under steady state conditions b Turbocharged engine under steady-state conditions c Turbocharged engine under dynamic conditions

Cylinder-charge control systems on a diesel engine 1 2 3 7 4 8 5 6 Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7

Fig 22

1 Air filter 2 Turbocharger / supercharger with intercooler 3 Engine control unit 4 Exhaust-gas recirculation and cooler 5 Swirl flap 6 Engine cylinder 7 Inlet valve 8 Exhaust valve 35 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Fuel Pre-Supply Components

• Fuel pre-supply pump. Supplies low pressure fuel to fuel filter and then to the fuel injection pump. Excess fuel than needed is supplied and returned to fuel tank – sometimes cooled – but often the excess fuel is used to pre-heat the fuel supply • Fuel filter. Removes suspended particles to ensure fuel meets minimum purity before passing through components where wear is critical. Water separator. Emulsified or free water may condense and must be prevented from entering the fuel-injection equipment • Figures 23, 24. 36 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Fuel-injection system with additional overflow restriction on fuel filter

7 5 3 6 4 2 1

Fig 23

1 Fuel tank 2 Presupply pump 3 Fuel filter 4 In-line fuel-injection pump 5 Nozzle-and-holder assembly 6 Overflow valve 7 Overflow restriction

___ Supply line ----- Return line

Diesel fuel filter with water separator

2 1 5 3 6 7

Fig 24

1 Inlet 2 Outlet 3 Filter element 4 Water drain plug 5 Cover plate 6 Housing 7 Supporting tube 8 Water accumulation chamber

8 4

Fuel-Injection Pump – Control Sleeve Type (many other types) • Minimize harmful exhaust gas emissions • Optimize fuel consumption under all operating conditions of commercial diesel engines • Varying ‘start of delivery’ and ‘injected fuel quantity’ independent of engine speed via electronic control • Precise fuel metering • Effective improvement of the starting and warm-up phases • Figures 25, 26, 27, 28 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 39

Control-sleeve in-line fuel-injection pump (cut-a-way view)

1 2 3 4 5 6 7 8 9 10 11 12

Fig 25

1 Pump barrel 2 Control sleeve 3 Control rack 4 Pump plunger 5 Camshaft (connection to engine) 6 Start of delivery actuator mechanism 7 Control-sleeve shaft 8 Actuator solenoid for control-rack travel 9 Control-rack travel sensor 10 Connector 11 Disc for preventing fuel delivery which is also part of the oil return pump 12 Presupply pump 40

Control-sleeve in-line fuel-injection pump Type H1000 (RP39) with control unit

Fig 26 External view

Control-sleeve adjusting mechanism

1 2 3 4 5 6

Fig 27

1 Pump plunger 2 Recess for control sleeve 3 Spill port 4 Control sleeve 5 Control rack (injected fuel quantity) 6 Control-sleeve shaft 42 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Operating cycle of control-sleeve in the fuel-injection pump

1 2 3 4 5 6 7 8 9 10 a 11

SMK1817Y

Fig 28 a Bottom dead-center b Start of delivery c End of delivery d Top dead center

1 Delivery valve 2 Plunger chamber 3 Pump barrel 4 Control sleeve 5 Helix 6 Control port (start of delivery) 7 Pump plunger 8 Plunger spring 9 Roller tappet 10 Drive cam 11 Spill port

h 1 Plunger lift to port closing h 2 Effective stroke h 3 Residual travel

Common Rail – Fuel Rail (high-pressure accumulator) • Maintain fuel at high pressure – permanently filled with high pressure ‘compressed’ fuel • Dampen pressure fluctuations caused by the pump and fuel-injection cycles • When fuel nozzle opens, the injection pressure remains constant • Fuel rail acts as a fuel distributor • Figures 29, 30, 31 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 44

Operating cycle of control-sleeve in the fuel-injection pump

1 2 4 10 3 5 6 8 7 4 9

Fig 29

1 High-pressure pump 2 element shut-off valve 3 Pressure-control valve 4 High-pressure delivery line 5 High-pressure accumulator (fuel rail) 6 Fuel-rail pressure sensor 7 Pressure-limiting valve 8 Flow limiter 9 Nozzle 10 Engine ECU Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 45 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

High-pressure accumulator (fuel rail)

2 3 1 6 6 6

Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7

6 7 4 5

Fig 30

1 Fuel rail 2 Inlet from high-pressure pump 3 Fuel-rail pressure sensor 4 Pressure-limiting valve 5 Return pipe from fuel rail to fuel tank 6 Flow limiter 7 Fuel line to nozzle 46 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Nozzle (principle of operation

3 4 5 a 1 2 6 10 11 8 9 b c 7

Fig 31 a Resting position b Nozzle opens c Nozzle closes

1 Fuel-return outlet 2 Solenoid coil 3 Solenoid armature 4 Valve ball 5 Valve-control chamber 6 Pressure shoulder of nozzle needle 7 Nozzle jet 8 Outlet restrictor 9 High-pressure connection 10 Inlet restrictor 11 valve plunger 47

Injector Nozzle – A Dynamic Environment • Open / close a billion times • Reliable seal at 2,050 bar pressure • Shock frequency up to 10,000 times per minute • Internal fueling / discharge cycles – 1 to 2 ms • Pressure and temperature of combustion chamber • Inject precise volume of 3 to 350 mm 3 fuel at velocity of 2,000 km/h through an opening <0.25 mm 2 • Valve / needle clearance is 0.002 mm 3 • Figure 32 48 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Dimensions of diesel fuel-injection technology The world of diesel fuel injection is a world of superlatives – The valve needle of a commercial vehicle nozzle will open and close the nozzle more than a billion times in the course of its service life. It provides a reliable seal pressures as high as 2,050 bar as well as having to withstand many other stresses such as: 1) The shocks caused by rapid opening and closing (on cars this can take place as frequently as 10,000 times a minute if there are pre and post-injection phases) 2) The high flow-related stresses during fuel injection and 3) The pressure and temperature of the combustion chamber 49 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Dimensions of diesel fuel-injection technology - 2 The facts and figures below illustrate what modern nozzles are capable of: The pressure in the fuel-injection chamber can be as high as 2,050 bar. This is equivalent to the pressure produced by the weight of a large executive car acting on an area of a fingernail.

The injection duration is 1…2 milliseconds (ms). In one millisecond, the sound wave from a loudspeaker only travels about 33 cm.

Dimensions of diesel fuel-injection technology - 3 The injection durations on a car engine vary between 1 mm injected) and 50 mm 3 3 (pre (full-load delivery); on a commercial vehicle between 3 mm delivery). 1 mm mm 3 3 3 (pre-injection) and 350 mm 3 is equivalent to half the size of a pinhead. 350 is about the same as 12 large raindrops (30 mm km/h through an opening of less then 0.24 mm 2 3 (full-load per raindrop). That amount of fuel is forced at a velocity of 2,000 in the time of only 2ms.

The valve-needle clearance is 0.002 mm (2 μ m). A human hair is 30 times as thick (0.06 mm) Such hi-precision technology demands an enormous amount of expertise in development, materials, production and measurement techniques. 51 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Injector Tip Geometry

• Tip geometry varies from blind hole, conical blind hole, micro blind hole and sac-less nozzles; seat geometry; and injection-orifice geometry • Sac-less nozzles have minimum dead volume and lower HC emissions • Micro blind hole is suited for common rail FI • Spray shapes are important to avoid overlap and lack of combustion air • Commercial-vehicle engines have up to 10 spray orifices • Figures 33, 34, 35 53 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Fig 33 a Cylindrical blind hole and conical tip b Conical blind hole and conical tip c Micro-blind-hole d Sac-less (vco) nozzle

1 Cylinder blind hole 2 Conical nozzle tip 3 Neck radius 4 Nozzle-body seat face 5 Conical blind hole 54

Decisive areas of nozzle geometry

Fig 34

1 Injector-orifice geometry 2 Seat geometry 3 Blind-hole geometry 1 2 3 Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 55

High-speed photographs of rate-of discharge curve of a car hole-type nozzle

Fig 35

Systems Diagram for Commercial Vehicles • Engine, engine control unit and high-pressure injection components • Sensors and desired-value generators • Interfaces • Fuel supply system low pressure system) • Air intake system • Exhaust-gas treatment systems • Other interfaces, i.e. transmission control system, traction control system – not included • Figure 37, 38 57 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Common-rail diesel fuel-injector system for commercial vehicles (See Fig 36 Legend on following pages) Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 58

Fig 36 Legend Engine, engine control unit and high pressure injection components 22 High-pressure pump 29 electronic engine control unit 30 Fuel rail 31 Fuel-rail pressure sensor 32 Fuel injector 33 Relay 34 Auxiliary equipment (e.g. retarder, exhaust flap for engine brakes, starter motor, fan) 35 Diesel engine (DI) 36 Flame glow plug (alternatively grid heater) M Torque © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) A Sensors and desired-value generators 1 Accelerator-pedal sensor 2 Clutch switch 3 Brake switches (2) 4 Engine brake switch 5 Parking brake switch 6 Control switch (e.g. cruise control, intermediate speed control, engine speed and torque reduction) 7 Starter switch 8 Charge-air speed sensor 9 Crankshaft speed sensor (inductive) 10 Camshaft speed sensor 11 Fuel temperature sensor 12 Engine-temperature sensor (in coolant system) 13 Charge-air temperature sensor 14 Charge--air pressure sensor 15 Fan speed sensor 16 Air-filter differential pressure sensor 59

Fig 36 Legend - 2 B Interfaces 17 Air-conditioning compressor with control 18 Alternator 19 Diagnosis interface 20 SCR control unit 21 Air compressor CAN Controller Area Network (vehicle’s serial data bus) (up to three data busses) C Fuel supply system (low pressure system) 23 Fuel Pump 24 Fuel filter with water-level and pressure sensors 25 Control unit cooler 26 Fuel tank with filter 27 Pressure limiting valve 28 Fuel level sensor D Air Intake System 37 Exhaust-gas recirculation cooler 38 Control flap 39 Exhaust-gas recirculation actuator with exhaust recirculation valve and position sensor 40 Intercooler with by-pass for cold starting 41 Turbocharger (in this case with variable turbine geometry) with position sensor 42 Charge-air pressure actuator 60 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Fig 36 Legend - 3 E Exhaust gas emission control systems 43 Exhaust-gas temperature sensor 44 Oxidation-type catalytic converter 45 Differential-pressure sensor 46 Particulate filter 47 Soot sensor 48 Fluid level sensor 49 Reducing agent tank 50 Reducing agent pump 51 Reducing agent injector 52 NOx sensor 53 SCR catalytic converter 54 NH3 sensor 55 Blocking catalytic converter 56 Catalyzed soot filter Type CSF 57 Hydrolyzing catalytic converter © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 61

Diesel Engine Benefits

Three major factors for improved fuel economy compared to SI engines • Higher compression ratio (giving a larger area on the p.V indicator diagram) • Greater excess air (made possible by heterogeneous internal air/fuel mixing) • Absence of throttle flap – and consequently no throttle-related losses in the part-load range • In principle the fuel consumption of diesel engines is lower than that of gasoline engines – Figure 38 63 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM)

Increased compression ratio improves thermal efficiency and lowers specific fuel consumption, but increases pumping, friction and compression / expansion losses CR from 10 to 20 improves thermal efficiency from 26 to 40% and lowers specific fuel consumption from about 230 to 208 g/kWh.

However, compression and expansion losses, friction losses and pumping losses combine to reduce mechanical efficiency from about 83 to 75%.

Comparison of cumulative fuel consumption after cold start (10 o C)

Fig 38

1 Gasoline engine, 1.1 l, 37 kW (50 bhp) 2 Diesel engine, 1.5 l, 37 kW (50 bhp) Source: “Diesel-Engine Management 3rd Edition” ISBN 0-7680-1343-7 © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 65

Diesel Engine Challenges

• 10% larger engine displacement for equal power • Cold start • Limited engine RPM • Chemical reaction delay time to establish conditions for the oxidation combustion process • Fuel / air mixing within cylinder • Below 20% lean, poor mixing results in high production of soot • Need 20% excess air to assure completeness of combustion before the exhaust valve opens • High emissions of NOx and particle matter (soot) © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 66

Engine Design Options That Affect Emissions • Injection timing, pressure, pre- and post-injection Figures 12, 13, 14, 15, 16, 17, 18 • Exhaust Gas Recirculation. Slide 21 • Variable Valve Timing. Under development • Turbocharger/ Figures 21, 22. Slide 21 • 4-valve – primarily for passenger car diesel engine

Engine design, emissions control and fuel must be developed together using the systems approach in order to achieve optimal emission control, fuel efficiency and engine performance from this marvelous and complicated internal combustion engine

Diesel Engine Emissions

• Hydrocarbons – Figure 16 • NOx - Figure 15 • Soot – Figure 17 • Particle mass – total PM and elemental carbon • Solid particle number, size and surface © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 68

Hydrocarbon emissions

• Hydrocarbon exhaust emissions are relatively low in terms of g/bhp-hr • At large range of hydrocarbon species are present including toxics generated during combustion: Aldehydes Acrolein (responsible for diesel odor) Polynuclear Aromatic Hydrocarbons © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) 69

Nanometer particles constitute most of the number of particles and all of the surface area Particle filers remove over 99.9% of ultra-particles © 2005 Northeast States for Coordinated Air Use Management (NESCAUM) Lung alveoli penetrating particles can be eliminated almost completely by particle filter as BACT 71

The Exhaust Gas after the Filter is Cleaner than Ambient Air!

The authors wish to thank Robert Bosch GmbH for permission to use pictures and illustrations from – “Diesel-Engine Management” 3 rd Edition ISBN 07680-1343-7

Northeast States CLEAN AIR ACADEMY

Transcript Northeast States CLEAN AIR ACADEMY

Advanced Mobile Source Training Course MS 201 - Diesel

Heavy-duty Engine Features

4-Stroke Diesel Engine Cycle

4-Stroke Diesel Engine Valve Timing

Excess-Air Factor

(Lambda)

Lambda Levels in Diesel Engine

Injection Pattern Affects Emissions

Fuel Pre-Supply Components

Injector Tip Geometry

Diesel Engine Benefits

Diesel Engine Challenges

Diesel Engine Emissions

Hydrocarbon emissions

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