Chapter 19 - Common Rail
-
Upload
tommy-tribbiani -
Category
Documents
-
view
221 -
download
0
Transcript of Chapter 19 - Common Rail
-
8/20/2019 Chapter 19 - Common Rail
1/60
Chapter 19 - Common Rail
High Pressure FuelInjection Systems
Diesel Engine Technology For Automotive Technicians
Understanding & Servicing Contemporary Clean DieselTechnology
-
8/20/2019 Chapter 19 - Common Rail
2/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.2
What is Common Rail?
Common rail fuel systems represent the most recenttechnological achievements in clean diesel engine fuelinjection technology.
-
8/20/2019 Chapter 19 - Common Rail
3/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.3
Conventional Fuel System
Disadvantage
Camshaft actuated fuel systems plunger velocities are low at slowengine speeds. Poor pressurization and atomization results.
Timing and rate control are fixed in camshaft geometry
-
8/20/2019 Chapter 19 - Common Rail
4/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.4
What is Common Rail?
Common rail fuel systems pressurize fuel independently ofengine speed.
CR pressurizes fuel
independently of enginespeed. Availability of high fuelpressure over all engine
speeds = Loweremissions, improved power and fuel economy !
-
8/20/2019 Chapter 19 - Common Rail
5/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.5
What is Common Rail?
A variety of subcategories of common rail fuel systems exist. Generally, common rail refers to a fuel rail system which
supplies fuel at injection pressure to all injectors
This chapter!
-
8/20/2019 Chapter 19 - Common Rail
6/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.6
Common Rail – Features
High-pressure common rail supplies fuel at injection pressure toinjectors
ECM
Rail Pressure Sensor
Injectors
High-Pressure Fuel Pump
Fuel PressureRegulator
SolenoidsHigh-Pressure Fuel Rail
-
8/20/2019 Chapter 19 - Common Rail
7/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.7
Common Rail Advantages – Rate Shaping
The latest high pressure common rail systems are capable of differentinjection events in one combustion cycle.
-
8/20/2019 Chapter 19 - Common Rail
8/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.8
Common Rail Advantages - Injection Rate Shaping
The quantity of fuel injected per degree of crank angle rotation is referred to as the fuelrate.
Injection rate affects emissions, performance, fuel economy and even engine noise levels. A specific injection rate will correspond to any given engine speed and load condition as
well as operating condition (i.e. oil, fuel and air temperature, boost pressure etc..)
-
8/20/2019 Chapter 19 - Common Rail
9/60
-
8/20/2019 Chapter 19 - Common Rail
10/60
-
8/20/2019 Chapter 19 - Common Rail
11/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.11
Common Rail - Components
All common rail systems have the following parts in
common: Injectors High pressure pump Fuel rail Relief valve Rail pressure sensor Fuel pressure regulator
-
8/20/2019 Chapter 19 - Common Rail
12/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.12
Common Rail - Components
This 3-cylinder CR diesel used in the MB Smart car achieves4.2L/110km combined fuel mileage. (56-mpg US)
High-Pressure Fuel
Rail
InjectorsFuel Supply from
High Pressure Pump
Fuel Rail PressureSensor
ReturnFuel
Relief Valve
-
8/20/2019 Chapter 19 - Common Rail
13/60
-
8/20/2019 Chapter 19 - Common Rail
14/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.14
CR Injectors
High pressure common rail is a recent innovation. The technology did not exist to switch fuel injection on and off at
pressures exceeding 20K-psi at the speeds required for combustion
-
8/20/2019 Chapter 19 - Common Rail
15/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.15
CR Injectors - Types
ElectromagneticSolenoid
Piezo-Electric
Actuator
These DMAX injectors
represent the two typesof CR injectors.
1. Electromagneticsolenoids
2. Piezoelectric inlineactuators
-
8/20/2019 Chapter 19 - Common Rail
16/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.16
CR Injector Comparisons
-
8/20/2019 Chapter 19 - Common Rail
17/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.17
CR Injectors – Solenoid Type
Solenoid injectors use anelectromagnet to control
injection events.
-
8/20/2019 Chapter 19 - Common Rail
18/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.18
Solenoid CR Injection
Injection events are
triggered electricallybut the main actuationforces are hydraulic
The solenoid armatureis a pilot needle valvewhich controls the flowof fuel out of apressure chamber
above the needlevalve.
-
8/20/2019 Chapter 19 - Common Rail
19/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.19
Solenoid CR InjectionSequence
Important note – highpressure fuel (yellow) holdsthe nozzle valve against its
seat.
Pressure above the needle valve isslightly greater than below so
injection cannot take place
-
8/20/2019 Chapter 19 - Common Rail
20/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.20
Solenoid CR Injection
1. The injector at rest
High pressure fuel is atthe bottom and top of the
needle valve but noinjection takes place sincethe larger surface area ontop of the needle valvehold the nozzle against its
seat.
-
8/20/2019 Chapter 19 - Common Rail
21/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.21
Solenoid CR Injection
2. Injection
The solenoid is energized and liftsthe pilot needle or check ball from its
seat above the needle valve.
Fuel pressure above the needle valvedrops and fuel pressure below thevalve forcing the nozzle from its seat.
Fuel cannot fill the chamber abovethe needle valve quickly since thereis a restriction in the passagewaybetween the rail pressure fuel and
pressure chamber
Restriction
Fuel Return
-
8/20/2019 Chapter 19 - Common Rail
22/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.22
Solenoid CR Injection
3. End of Injection
The solenoid is de-energized and the
check ball return to its seat.
Fuel at rail pressure builds-up quicklyabove the needle valve forcing it
against it’s seat thus ending injection
-
8/20/2019 Chapter 19 - Common Rail
23/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.23
Adaptive Cylinder Balance
This 2004 6.6L DMAX engine is adjusting fuel rate at idle toeach injector to enable smoother engine operation
-
8/20/2019 Chapter 19 - Common Rail
24/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.24
Pilot Injection
Note pilot injection factors are variable for CR engines. UnlikeHEUI and other fuel systems where pilot injection ismechanical, CR engines it is achieved electronically –microseconds in duration! (2004 6.6L DMAX)
-
8/20/2019 Chapter 19 - Common Rail
25/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.25
Piezo-electric Actuated Injectors Piezo technology enables
the fastest switchingtime for injectorscurrently allowing up to
seven injection events inone injection sequence.
The mass of the inline
actuators is less thansolenoid actuatedinjectors
Solenoid
Inline Piezo
Actuator
-
8/20/2019 Chapter 19 - Common Rail
26/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.26
Piezo-electric Actuated Injectors
Comparisons of injector response time (top solenoid,bottom piezo-electric actuation.
-
8/20/2019 Chapter 19 - Common Rail
27/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.27
Piezo-electric Actuated Injectors
Piezo-electric injectors can achieve lower emission reduction withimproved rate shaping and multiple injection events.
-
8/20/2019 Chapter 19 - Common Rail
28/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.28
Piezo-electric Principles
Piezo crystals expand when current is applied to a stack of crystalsand contract when the currents polarity is reversed.
Note the change in current direction and the shape of the crystals
Piezo Mineral Crystal
-
8/20/2019 Chapter 19 - Common Rail
29/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.29
Piezo-electric Principles
Stacks of piezo crystals deform when energized with electrical current.
Piezo crystals respond much faster than electromagnetic solenoids
-
8/20/2019 Chapter 19 - Common Rail
30/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.30
Piezo-electric CR Injection Sequence
Piezoelectric actuators operate a servo valve to changehydraulic pressure acting on the needle valve holding thenozzle closed
-
8/20/2019 Chapter 19 - Common Rail
31/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.31
Piezo-electric CR Injection Sequence
2008MY Ford 6.4L Powerstroke Diesel uses piezo electricactuated CR injectors manufactured by Siemens
-
8/20/2019 Chapter 19 - Common Rail
32/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.32
Piezo-electric CR Injection Sequence
The Ford nozzle has aconventional type ofnozzle.
-
8/20/2019 Chapter 19 - Common Rail
33/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.33
Piezo-electric CR Injection Sequence
Like solenoid type CRinjectors, in a piezo injector
the nozzle needle valve isheld in place by hydraulicforce of pressurized fuel.
A mushroom shaped valvecontrols the exit of fuelpressure above a controlpiston holding the needlevalve on its seat.
-
8/20/2019 Chapter 19 - Common Rail
34/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.34
Piezo-electric CR Injection Sequence
High pressure fuel forces the
control piston against theneedle valve
-
8/20/2019 Chapter 19 - Common Rail
35/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.35
Piezo-electric CR Injection Sequence
Applying current to the piezo
crystals forces the mushroomvalve downward releasingpressure above the controlpiston to the lower pressure fuelinlet.
Fuel pressure below the needlevalve force the valve upwardsand injection begins
ExitingFuel
-
8/20/2019 Chapter 19 - Common Rail
36/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.36
Injection Ending - Current Reversal
The injection event can end quickly by changing the direction of current
flow through the stack of piezo crystals. Without pressure from the piezo crystals, hydraulic force closes the
mushroom valve and pressure returns to the top of the control piston
-
8/20/2019 Chapter 19 - Common Rail
37/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.37
Hydraulically Amplified CR Injectors
Current heavy-duty diesel are using hydraulically amplified CR injectors.
These injectors use an internal amplifier/intensifier piston similar in principle toHEUI injectors
-
8/20/2019 Chapter 19 - Common Rail
38/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.38
Co-Axial Nozzle CR Injectors
Two rows of spray orifices are used in a co-axial nozzle toachieve more sophisticated rate shaping of injection
-
8/20/2019 Chapter 19 - Common Rail
39/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.39
CR Injector Failure
CR injectors are very sensitive to dirt.
The smallest particle of dirt causing a solenoid or mushroom valve to stay opencould allow the injector to continuously inject fuel.
This overheated cylinder which damaged valves was caused by an injector “stuck open”.
-
8/20/2019 Chapter 19 - Common Rail
40/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.40
CR Injectors – Lines
Injectors
Fuel ReturnLines
High PressureLines
The injector and lines on the 2006 6.6L DMAX engine are all locatedoutside the scalloped valve covers to prevent fuel leaks into the engine
-
8/20/2019 Chapter 19 - Common Rail
41/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.41
CR Injectors – Lines
These Cummins B series injectors use a quill tube to connect an external injector linewith the injector.
These tubes must be carefully tightened and the high-pressure connection cleanedduring assembly to prevent leakage!
Quill Tube
HighPressure
Connection
-
8/20/2019 Chapter 19 - Common Rail
42/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.42
CR Injectors – Lines
This early 6.6l DMAX has line fitting clamps to prevent looseningand leakage of lines.
-
8/20/2019 Chapter 19 - Common Rail
43/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.43
CR Injector Lines
Never crack-open a high pressure line when running an engine.Cylinder misfires cannot be detected and high pressure fuel canpenetrate the skin
RailPressureSensor
Fuel Rail
HighPressure
Lines
-
8/20/2019 Chapter 19 - Common Rail
44/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.44
Ford Duratorq I-4 CR Engine
The hugely popular European Ford TDCi 2.0L Duratorqengine (Ford Galaxy van shown)
-
8/20/2019 Chapter 19 - Common Rail
45/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.45
CR Injector Trim Codes
Characteristics of CR injectorscause fuel delivery variations over
a wide range of operation(pressure & actuation time)
-
8/20/2019 Chapter 19 - Common Rail
46/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.46
CR Injector Trim Codes
Trim codes
Trim codes or injection quality adjustment (IQA) codes for each injectorare entered in the ECM module and used to compensate for deliveryquantity variations
High Pressure Pumps
-
8/20/2019 Chapter 19 - Common Rail
47/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.47
High Pressure Pumps
High pressure pumps take low transfer fuel pressure and pressurize the fuel tothe for injection.
Hi h P P
-
8/20/2019 Chapter 19 - Common Rail
48/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.48
High Pressure Pumps
A Bosch CP-3 Pump is commonly used in automotive applications
Radial Plungers
Fuel PressureRegulator
Low PressureGear Type
Transfer Pump
Fuel Return
High PressureOutlet
Inlet/Outlet
Check Valve
-
8/20/2019 Chapter 19 - Common Rail
49/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.49
High Pressure Pumps
Bosch CP-3 High Pressure Pump
FuelReturn
FuelInlet
Fuel Pressure
Regulator
-
8/20/2019 Chapter 19 - Common Rail
50/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.50
High Pressure Pumps
Bosch CP-3High
Pressure
Pump
Location of the high-pressure pump on a 2007 6.6L DMAX
i h
-
8/20/2019 Chapter 19 - Common Rail
51/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.51
High Pressure Pumps
Rear geartrain mounted pump of the 6.7L Cummins diesel
High PressurePump
Hi h P P
-
8/20/2019 Chapter 19 - Common Rail
52/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.52
High Pressure Pumps
Location of the high pressure pump on the 2008MYPowerstroke
High Pressure Pumps
-
8/20/2019 Chapter 19 - Common Rail
53/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.53
High Pressure Pumps
Radial plunger pumps use three lobed cams to driven by the engine to pressurize fuel. Check valves in the end of the plunger pistons operate to control flow of fuel in and
out of the pumping chambers
High Pressure Pumps Pressure Regulation
-
8/20/2019 Chapter 19 - Common Rail
54/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.54
High Pressure Pumps – Pressure Regulation
A fuel pressure regulating valve controls fuel pressure using a PWM signal sent from theECM.
With no signal, all pressurized fuel is sent to the fuel rail. Increasing the PWM signal lowers fuel pressure to the rail
High Pressure Pumps Pressure Regulation
-
8/20/2019 Chapter 19 - Common Rail
55/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.55
High Pressure Pumps – Pressure Regulation
Note the duty-cycle reportedfor the fuel pressure regulator
(35%)
Fuel temperature is calculatedthrough ECM measurement of
the resistance of the pressureregulator coil.
High Pressure Pumps – Inlet Volume Regulation
-
8/20/2019 Chapter 19 - Common Rail
56/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.56
High Pressure Pumps – Inlet Volume Regulation
To reduce parasitic power loss some pumps such as used on thePowerstroke regulate the amount of fuel admitted into the pump usinga volume control regulator.
Fuel Rail
-
8/20/2019 Chapter 19 - Common Rail
57/60
Title, Edition Author(s)
© 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.57
Fuel RailFuel Rail
Fuel RailPressure Sensor
Fuel RailInlet
The fuel rail is common to several cylinders.
Internal orifices dampen pressure pulses
Fuel Rail
-
8/20/2019 Chapter 19 - Common Rail
58/60
Title, Edition Author(s)
©2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.58
Fuel Rail
This Ford Dura-torque diesel
uses a circular shaped fuelrail (Delphi) for packagingreasons
Fuel Rail
P P t ti P Li iti V l
-
8/20/2019 Chapter 19 - Common Rail
59/60
Title, Edition Author(s)
©2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.59
Pressure Protection – Pressure Limiting Valve
To protect the high pressure system from over pressurization apressure limiting valve is used in the high pressure section.
Pressure Protection
-
8/20/2019 Chapter 19 - Common Rail
60/60
Title, Edition Author(s)
©2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.60
Pressure Protection
The function block on this DMAX contains the pressureliing valve.