Sistemi Di Iniezione Diesel_1-1

1

Sistemi di iniezione per Motori Diesel I.D.

1

IL SISTEMA DI

ALIMENTAZIONE DEL COMBUSTIBILE

NEI MOTORI DIESEL

POLITECNICO DI TORINO

PROPULSORI TERMICI I

Prof. Marco Badami


2

L’evoluzione dei sistemi iniezione per motori Diesel ad Iniezione Diretta

•Pompa in linea

•Pompa rotativa BoschVE

•Pompa a stantuffi radiali

•Iniettore Pompa

•Il sistema Common Rail

• Prestazioni

• La tecnologia Multijet


3

Un sistema iniezione Diesel deve assolvere tre principali esigenze:

� Fasatura: l’iniezione deve effettuarsi in un ben determinato istante

del ciclo.

� Quantità: il sistema deve permettere l’introduzione di un

quantitativo stabile di combustibile.

� Qualità: il getto deve avere delle ben determinate caratteristiche di

Polverizzazione, Penetrazione e Diffusione


4

Un sistema iniezione Diesel I.D. moderno deve:

� Iniettare ad alta pressione (> 1400 bar) per ridurre il tempo di iniezione e migliorare l’atomizzazione e quindi aumentare la densitàdi potenza

� Gestire un treno di iniezioni successive per ciclo motore per poter

modulare il processo di combustione e quindi ridurre il rumore e le emissioni

� Distribuire il combustibile in camera di combustione nella maniera

ottimale e quindi ridurre la fumosità


5

Come è possibile gestire la combustione con un sistema iniezione Diesel moderno?

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-30 -20 -10 0 10 20 30 40 50 60

Crank angle [deg]

Pre

ssu

re [

bar]

-100

100

300

500

700

900

1100

1300

1500

1700

1900

HR

R [

kJ/m

3d

eg

]

Sistemi meccanici

(ante 1996)

Sistemi a controllo elettronico

(post 2000)


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Bosch Diesel Fuel Injection Systems

2


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Pompa in Linea


8

Pompa in Linea


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Pompa in Linea


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Pompa in Linea


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Pompa in Linea


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Pompa in Linea

3


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Pompa in Linea


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Pompa in Linea


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Pompa in Linea


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE

4


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE

5


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa Rotativa VE


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Pompa a stantuffi radiali

6


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Radial distributor pump with on board electronics

Bosch VP 44

Features

� High peak injection pressure (> 1600 bar)

� Wide range of timing (> 30°CA)

� 1 Pre injection per cycle

� On board engine ECU

Constraints

� Injection pressure depends on speed/load

in open loop

� Only 1 Pre injection per cycle with timing

limitation

� Difficult metering of the Pre injection


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Iniettore Pompa


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Unit Injector – Bosch UIS

Features

� Cam shaft driven

� High peak Injection pressure (> 2000 bar)

� Wide range of timing (> 30°CA)

� 2 Pre inj.+ 1 Post inj. per cycle

Constraints

� Injection pressure depends on speed/load

in open loop

� Heavy impact on the engine layout

� Impossible retrofit of existing hardware


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Il sistema iniezione Common Rail

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Common Rail – Bosch CRS

Features

� High Injection pressure (> 1600 bar)

� Closed loop injection pressure control

(independent from speed/load)

� Fully flexible range of timing

� Up to 5 injection events per cycle

� Easy retrofit of existing hardware

equipped with conventional systems

Constraints

� System complexity, including the vehicle

interface (hydraulic/electrical/electronic)

� Higher nozzle stress, compared with

conventional system


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Il sistema Common Rail permette:

� Completa flessibilità di gestione della pressione di iniezione (> 1400

bar); migliorare l’atomizzazione e quindi ridurre la fumosità ai bassi

regimi e aumentare la densità di potenza

� Possibilità di effettuare iniezioni multiple anche molto ravvicinate, per

modulare il processo di combustione e quindi ridurre il rumore e le emissioni

� Completa flessibilità nella gestione dell’anticipo di iniezione

� Elevata precisione e ripetibilità nella regolazione della quantitàiniettata (anche differente da cilindro a cilindro)

� Completa possibilità di rimappare la centralina se necessario, variando

quindi i parametri


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Filtro

RAIL

Elettroiniettore

Sensore di

Pressione

Pompa Alta

Pressione

Serbatoio

Regolatore di

Pressione

Pompa di Innesco

Common Rail – Layout Idraulico


40Iniettori Elettroidraulici

ELECTRONIC

CONTROL UNITPompa Alta

Pressione

Regolatore di

Pressione

Pompa di

Alimentazione

Sensore di

Pressione

Common Rail – Controllo


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Common Rail Injector

Polverizzatore

Asta di comando

Corpo Iniettore

Servovalvola

Gruppo Armatura

Solenoide

High pressure fitting


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Common Rail InjectorMain parts

Anchor

Load spring spacer

Magnet spring

Anchor bolt

Anchor spring

Residual Air Gap spacer

Bolt guidance

Nut

Anchor lift spacer

Valve sphere + sphere seat

Valve body

Valve pushroad

8


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Common Rail injector - 2 way control valve

“A” pre hole

“A” hole

Control volume

“Z” pre hole

“Z” hole


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ELECTROMAGNET

TWO WAYVALVE

NOZZLE

INLET FUEL ATHIGH PRESSURE

• Electromagnete not activated

• Same pressure in the valveand in the nozzle

• Forces balance: F1 > F2

• Nozzle closed

F1

F2

ELECTROMAGNET

TWO WAY

VALVE

NOZZLE

ELECTRIC ACTUATION

INLET FUEL AT

HIGH PRESSURE

FUEL RECIRCULATEDAT LOW PRESSURE

• Electromagnet activated

• Pressure in the valvereduced by opening theoutflow hole


• Nozzle open

F1

F2

Outflow hole open

Common Rail injector – Funzionamento


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ELECTROMAGNET

TWO WAY

VALVE

NOZZLE

ELECTRIC ACTUATION

INLET FUEL AT

HIGH PRESSURE

FUEL RECIRCULATED

AT LOW PRESSURE

• Electromagnet activated

• Pressure in the valvereduced by opening theoutflow hole


• Nozzle open

F1

F2

Outflow hole open

Injector functioning

Control Volume press.

[A]

Current

Anchor lift

Neddle lift

Injection rate

Time [µµµµs]

[mm

3/ µµ µµ

s]

[ µµ µµm

][b

ar]

[ µµ µµm

]

~ 300 µµµµs

~ 40 µµµµs

~ 450 µµµµs (depending on the neddle lift)


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Common Rail Injector - the nozzle

Needle

Nozzle

body

Sealing

diameter

Stabilization

grooveHole


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VCO Microsac Minisac

(Valve Covered Orifice)

Trapped fuel beloved the needle hydraulic sealing (5 holes x φ 0.15 mm x l 1mm)

0,145mm3 0,23mm3 0,32mm3

Common Rail Injector - the nozzleTip geometries


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Common Rail Injector - the nozzleInfluence of the hole inlet geometry on the flow field and discharge coefficient (µ)

9


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Common Rail Injector - the nozzleFunctional issue


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Common Rail high pressure pump


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Common Rail high pressure pump


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Common Rail Injector performanceInfluence of pressure on the injection rate

Injection rate [mm3/µs] = f ( Inj. Press.)

ET 670 µµµµs


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Common Rail Injector performanceInfluence of ET on the injection rate

Injection rate [mm3/µs] = f ( ET)

Inj. pressure 800 bar


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Common Rail Injector performance

Injector Characteristic map ⇒ Fuel Delivery = f (E.T., Inj. Press.)

Pilot Injection Area

(zoom)

10


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Common Rail Injector performanceInfluence of the injections separation (Dwell Time) on the total (Pilot+Main) delivery

Delivery (Pilot + Main) = f (ETPilot, ETMain, Inj. Press., Dwell Time)

Injection stability threshold

StabilityInstability

DT

P M


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Common Rail Injector performance

Waterfall analysis of the Dwell Time effect on injection rate

Injector current Injection rate

DT

P M


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La tecnologia Multijet


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CRS with

Multiple Injections

Noise control

in cold operation

and low rpm

� Injection Duration Control

� Combustion Rate Shaping

� Soot oxidation

DENOx or DPF

Regeneration

PILOT POSTMAIN

PRE MAIN AFTER

CRS1st generation

From Pilot Injection...

TDC +60°-60°

PIL

OT

MA

IN

COMBUSTI

ON

RATE

FUELL

ING

… to Sequential Multiple Injections

TDC +60°-60°

PIL

OT

PR

E

MA

IN

AFT

ER

COMBUS

TION

RATE

FUELL

ING

PO

ST

The Multijet tech – the application


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Crank angle [deg]

Pre

ssu

re [b

ar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [k

J/m

3d

eg

]

MAIN

ADVANCED MAIN

PRE + MAIN

PRE + PRE + MAIN

PRE + PRE + MAIN + AFTER

MULTIJET – The Diesel combustion controlThe indicated cycle shaping by the means of the injection strategy

1500 rpm x 5 bar of BMEP


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0

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80

-15 -10 -5 0 5 10 15 20 25 30

Crank angle [deg]

Pre

ssu

re [

bar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [k

J/m

3d

eg

]

CYL. PRESS. [bar]

INJ. RATE [mm3/deg]

HRR [kJ/m3deg]

NOx = 1.59 g/kWh

SOOT = 0.010 g/kWh

CN = 95 DBA

Single injection - S.o.I. 0º C.A.


1500 rpm, 5 bar of BMEP

11


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80

-15 -10 -5 0 5 10 15 20 25 30

Crank angle [deg]

Pre

ss

ure

[b

ar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [

kJ

/m3

de

g]

CYL. PRESS. [bar]

INJ. RATE [mm3/deg]

HRR [kJ/m3deg]

NOx = 2.10 g/kWh

SOOT = 0.022 g/kWh

CN = 96 DBA

Single Advanced Injection - S.o.I. 3º C.A.




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0

10

20

30

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50

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-15 -10 -5 0 5 10 15 20 25 30

Crank angle [deg]

Pre

ss

ure

[b

ar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [

kJ

/m3

de

g]

CYL. PRESS. [bar]

INJ. RATE [mm3/deg]

HRR [kJ/m3deg]

NOx = 1.54 g/kWh

SOOT = 0.038 g/kWh

CN = 87 DBA

Pre + Main - S.o.I. 0º ETPre 300 µµµµs DTPre 200 µµµµs




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-15 -10 -5 0 5 10 15 20 25 30

Crank angle [deg]

Pre

ss

ure

[b

ar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [

kJ/m

3d

eg

]

CYL. PRESS. [bar]

INJ. RATE [mm3/deg]

HRR [kJ/m3deg]

NOx = 1.55 g/kWh

SOOT = 0.101 g/kWh

CN = 84 DBA

Double Pre + Main - S.o.I. 0º ETPre 1&2 300 µµµµs DTPre 1&2 200 µµµµs




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Crank angle [deg]

Pre

ss

ure

[b

ar]

-100

0

100

200

300

400

500

600

700

800

900

HR

R [

kJ

/m3

deg

]

CYL. PRESS. [bar]

INJ. RATE [mm3/deg]

HRR [kJ/m3deg]

NOx = 1.54 g/kWh

SOOT = 0.095 g/kWh

CN = 84 DBA

Double Pre + Main + After - S.o.I. 0º ETPre 1 & 2 300 µµµµs DTPre 1 & 2 200 µµµµs ETAfter 300 µµµµs DTAfter 700 µµµµs




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The Piezo Technology in the Diesel Injector


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The Piezo Tech in the Diesel Injector - The functioning

Outlet

A hole

Inlet

Z hole

Bypass

Addittive

Z hole

V3

control

volume

control

valve

needle

1) Starting position

outlet

inlet

bypass

blocked

V3

2) Needle opening

• Bypass blocked

• normal CR-function

with inlet/outlet throttle

inlet

inlet

bypass

open

V3

3) Needle closing

• Bypass open

• two inlet throttlesrail pressure

leakage pressure

control volume pressure

12


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The Piezo vs Advanced Solenoid injector

E.T.

Piezo Voltage inj.pattern

Solenoid Current inj.pattern


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Tdiff

CRIP 1 MI inj. currentpattern

Tdiff

Piezo inj. Voltage pattern

800 bar / ~20 mm3 tot.

(Main = 18,5 mm3, Pilot =1.5 mm3 , Inj. Pipe = 200 mm)



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Injection rate @ 1600 bar 70mm3 (different ET)


Sistemi Di Iniezione Diesel_1-1

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