Xin Q. Diesel Engine System Design

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458 Diesel engine system design

In general, turbocharged diesel engines produce lower exhaust noise than

non-turbocharged diesel engines. Compression brake noise is essentially a

part of the exhaust noise and it can be controlled by a functioning mufer.

Using proper mufers with regular maintenance and inspections is important

for controlling the compression brake noise. Advanced high-performance

mufers can be used with the compression brakes to reduce the noise without

increasing the back pressure or losing fuel economy. Such a mufer can also

reduce the acceleration noise. Donaldson’s mufer, developed in cooperation

with Jacobs Vehicle Systems, was reported to be able to reduce the sound

pressure level of the exhaust noise by half during braking compared to a

conventional mufer. More detailed studies on diesel engine brake noise

are addressed by Reinhart (1991), Reinhart and Wahl (1997), and Wahl and

Reinhart (1997).

6.4.9 Powertrain controls of compression brakes

Vehicle braking efciency and stability control are very important for driving

safety. The controls of a central braking management system were described

by Göhring et al. (1992). Engine brake control with an automatic transmission

and advanced estimates of vehicle weight and desirable deceleration were

studied by Murahashi et al. (2006). Powertrain control of the compression

brakes and controller design were extensively studied by a group of

researchers at the University of Michigan. An adaptive controller design for a

continuously variable compression brake to control the braking valve opening

timing was proposed by Druzhinina et al. (2000). Their study was to ensure

good vehicle speed tracking performance under large variations of vehicle

weight and road grade. Engine brake control models and a PI controller for

a variable compression brake actuator and the service brakes were developed

by Moklegaard et al. (2001). A vehicle speed control study was conducted

by Druzhinina and Stefanopoulou (2002) to address the coordinated controls

on the demands between the service brakes and the compression brake by a

PID closed-loop braking controller. Nonlinear controllers for vehicle speed

control with a variable compression brake were developed by Druzhinina et

al. (2002a) to coordinate the compression braking with gear selection and

service brakes. Finally, Druzhinina et al. (2002b) summarized their study of

adaptive controls for the variable compression brake to ensure good vehicle

speed tracking performance under large variations of vehicle weight and

road grade.

6.5 References and bibliography

Akiba K, Ohtani M and Yoshiki H (1981), ‘The optimized design of the exhaust brake

of the automotive diesel engine’, SAE paper 810344.

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459Engine brake performance in diesel engine system design

Barbieri F A A, Andreatta E C, Argachoy C and Brandao H (2010), ‘Decompression

engine brake modeling and design for diesel engine application’, SAE paper 2010-

01-1531.

Cummins C L (1959), ‘Diesel engine brake control’, US Patent No. 2,876,876, March

10.

Cummins D D (1966), ‘The Jacobs engine brake application and performance’, SAE

paper 660740.

Darragh C T (1974), ‘BrakeSaver – Caterpillar’s highway truck retarder’, SAE paper

741129.

Druzhinina M and Stefanopoulou A G (2002), ‘Speed control experiments for commercial

heavy vehicles with coordinated friction and engine compression brakes’, proceedings

of the American Control Conference, Anchorage, AK, May 8–10, pp. 2546–2551.

Druzhinina M, Moklegaard L and Stefanopoulou A G (2000), ‘Compression braking

control for heavy-duty vehicles’, proceedings of the American Control Conference,

Chicago, IL, June, pp. 2543–2547.

Druzhinina M, Stefanopoulou A G and Moklegaard L (2002a), ‘Speed gradient approach

to longitudinal control of heavy-duty vehicles equipped with variable compression

brake’, IEEE Transactions on Control Systems Technology, 10(2), 209–220.

Druzhinina M, Stefanopoulou A and Moklegaard L (2002b), ‘Adaptive continuously

variable compression braking control for heavy-duty vehicles’, Transactions of the

ASME, Journal of Dynamic Systems, Measurement, and Control, 124, 406–414.

‘Engine braking’, Truck Engineering, November 1992, pp. 11–15.

Fancher P S and Radlinski R W (1983), ‘Directional control of retarder-equipped heavy

trucks operating on slippery surfaces’, SAE paper 831788.

Fessler H and Genova M (2004), ‘An electro-hydraulic “lost motion” VVA system for

a 3.0 liter diesel engine’, SAE paper 2004-01-3018.

Freiburg K E (1994), ‘Design and development of the Jacobs model 340A engine retarder

using concurrent development’, SAE paper 940585.

Freund D M (2007), Foundations of Commercial Vehicle Safety: Laws, Regulations and

Standards, the 52nd L. Ray Buckendale Lecture, SAE paper 2007-01-4298, SAE

International, Warrendale, PA.

Göhring E, Glasner E C and Povel R (1992), ‘Engine braking systems and retarders – an

overview from a European standpoint’, SAE paper 922451.

Greathouse J F, Pekar F J and Gibson R B (1971), ‘The Mack Maxidyne, ENDT865

diesel with Dynatard engine brake’, SAE paper 710557.

Habib G (1992), ‘The present status of electro-magnetic retarders in commercial vehicles’,

SAE paper 922450.

Haiss J (1992), ‘Demand criteria on retarders’, SAE paper 922453.

Hu H, Israel M A and Vorih J M (1997a), ‘Variable valve actuation and diesel engine

retarding performance’, SAE paper 970342.

Hu H, Vorih J M and Israel M A (1997b), ‘The integrated lost motion VVT diesel engine

retarder’, SAE paper 973180.

Imai Y, Torii A, Kobayashi N, Miura Y and Maeda S (1996), ‘Development of a new

decompression brake for heavy duty diesel engine’, JSAE Review, 17, 213–217, JSAE

paper 9630381.

Israel M A (1998), ‘Jacobs variable valve actuation system for diesel powering and

retarding’, GT-Suite Users’ Conference proceedings, November.

Israel M A and Hu H (1993), ‘Impact of ambient parameters on operating efciency

of compression release engine retarder systems on heavy duty diesel engines’, SAE

paper 932972.

Diesel-Xin-06.indd 459 5/5/11 11:50:37 AM

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460 Diesel engine system design

Jahn M (1989), ‘A contribution on the application of downhill driving brakes’, SAE

paper 892501.

Kirchensteiner J (1927), ‘Motor brake’, US Patent No. 1,637,117, July 26.

Klemen D, Martin R K and Trotter J L (1989), ‘A new Allison transmission output

retarder’, SAE paper 892530.

Kubomiya T, Kuwahara T and Araki K (1992), ‘Permanent-magnet-type-retarder in

commercial vehicles’, SAE paper 922455.

Kuwano M, Endoh K and Suzuki I (1983), ‘Exhaust brakes for Japanese trucks’, SAE

paper 831789.

Limpert R (1975), ‘An investigation of integrated retarder/foundation brake systems for

commercial vehicles’, SAE paper 750126.

Limpert R (1992), Brake Design and Safety, SAE International, Warrendale, PA.

Meistrick Z (1992), ‘Jacobs new engine brake technology’, SAE paper 922448.

Meistrick Z, Usko J, Shoyama K, Kijima K, Okazaki T and Maeda Y (2004), ‘Integrated

internal EGR and compression braking system for Hino’s E13C engine’, SAE paper

2004-01-1313.

Moklegaard L, Druzhinina M and Stefanopoulou A G (2001), ‘Brake valve timing and

fuel injection: a unied engine torque actuator for heavy-duty vehicles’, Vehicle

System Dynamics, 36(2–3), 179–201.

Morse W H and Rife J M (1979), ‘Compression engine brake performance with turbocharged

diesel engines’, SAE paper 790769.

Murahashi T, Sonoda S, Yamada N, Katoh H and Hayakawa K (2006), ‘Development

of engine brake control system for commercial vehicle with 6-speed automatic

transmission’, SAE paper 2006-01-1674.

O’Day J and Bunch H M (1981), ‘Safety and economic benets of heavy truck retarder

use’, SAE paper 811260.

Price R B and Meistrick Z S (1983), ‘A new breed of engine brake for the Cummins

L10 engine’, SAE paper 831780.

Radlinski R (1987), ‘Braking performance of highway US vehicles’, SAE paper

870492.

Radlinski R (1989), ‘Heavy vehicle braking – US versus Europe’, SAE paper 892504.

Rao N N N (1968), ‘The basic theory of hydraulic dynamometers and retarders’, SAE

paper 680178.

Reinhart T E (1991), ‘US vehicle noise regulations and the effects of vehicle condition’,

SAE paper 912709.

Reinhart T E and Wahl T J (1997), ‘Reducing compression brake noise’, SAE paper

971870.

SAE Surface Vehicle Recommended Practice J257 (1997), ‘(R) Brake rating horsepower

requirement – commercial vehicles’.

SAE Surface Vehicle Recommended Practice J2458 (1998), ‘Exhaust brake dynamometer

test and capability rating procedure’.

SAE Surface Vehicle Recommended Practice J1489 (2000), ‘Heavy truck and bus retarder

downhill performance mapping procedure’.

SAE Surface Vehicle Recommended Practice J1621 (2005), ‘Engine retarder dynamometer

test and capability rating procedure’.

SAE Surface Vehicle Recommended Practice J2627 (2009), ‘Braking system denitions

– truck and bus’.

Schmitz T N, Bergmann H and Daeuble H (1992), ‘The new Mercedes-Benz engine

brake with decompression valve’, SAE paper 920086.

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461Engine brake performance in diesel engine system design

Schmitz T N, Holloh K D, Fleckenstein G and Juergens R (1994), ‘The new Mercedes-

Benz engine brake with pulsed decompression valve – decompression valve engine

brake (DVB)’, SAE paper 942266.

Schreck H, Kucher H and Reisch B (1992), ‘ZF retarder in commercial vehicles’, SAE

paper 922452.

Schwoerer J, Huang S and Trzaska G (2002), ‘Simulation tools for development of advanced

engine braking and variable valve actuation systems’, SAE paper 2002-01-0375.

Sequeira M M and Faria P P (1984), ‘Adverse consequences for engines resulting from

the frequent use of exhaust brakes’, Tribology International, 17(6), 335–340.

Spurlin S F and Trotter J L (1982), ‘The Allison transmission output retarder’, SAE

paper 821277.

Wahl T J and Reinhart T E (1997), ‘Developing a test procedure for compression brake

noise’, SAE paper 972038.

Wong J Y (1993), Theory of Ground Vehicles, 2nd edn, John Wiley & Sons, New

York.

Xin Q (2008), ‘Engine brake concept analysis for improved engine brake performance’,

Navistar technical report 580.08.2515.

Yang Z (2002), ‘A study of two-stroke engine braking for HD diesel engines’, SAE

paper 2002-01-0487.

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462

Combustion, emissions, and calibration for

diesel engine system design

Abstract: This chapter establishes the system design logic from emissions

to the overall engine system, especially the air system. It links three

sequential functions in an engine development cycle: combustion/emissions

development, engine system design, and engine calibration. It rst introduces

combustion and emissions development and the corresponding requirement

for air system design, followed by discussions on engine calibration

optimization at both steady-state and transients. The emissions behavior is

illustrated by using the minimum BSFC (brake specic fuel consumption)

optimization contour map. The advanced emissions modeling approach

suitable for engine system design is summarized. The concept of virtual

calibration is emphasized at the system design stage.

Key words: combustion, emissions, engine system design, calibration,

minimum BSFC (brake specic fuel consumption) optimization contour map,

heuristic macro-parameter-dependent approach.

7.1 The process from power and emissions

requirements to system design

At the beginning of an engine program, performance simulation can be

used extensively during the stage of choosing key technologies, for example

hybrid powertrain, waste heat recovery, variable valve actuation (VVA), and

cylinder deactivation. Once the technology path is dened, engine air system

design can start with several possible conguration options, for example high-

pressure-loop or low-pressure-loop exhaust gas recirculation (EGR), parallel

or series EGR coolers, single-stage or two-stage turbocharger, air-cooled or

coolant-cooled charge air cooler. The required input for system performance

design is the established target of air ow requirements to meet the emission

regulations. The air ow requirements generally include the gravimetric

air–fuel ratio, the EGR rate and the intake manifold gas temperature at each

critical engine speed and load mode. Those requirements are produced by

conducting combustion hardware searching and tuning. The ‘searching’

refers to screening different sets of hardware (e.g., intake ports, combustion

chambers, and fuel injection systems) to determine their ability to meet the

emission requirements. ‘Tuning’ (referred to before the system design) or

‘calibration’ (referred to after the system design) means any optimization

of the tunable parameters with a xed set of hardware. Some examples of

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463Combustion, emissions, and calibration for system design

tuning and calibration include calibrating the fuel injection pressure, the

injection timing, the VGT vane opening and the EGR valve opening to nd

the optimum air–fuel ratio and EGR rate for a minimum BSFC while meeting

the emission requirements. The ‘calibration’ links the electronic software

controls with the selected hardware for production engines. Engine system

design resides in the center of this design process and bridges the upstream

combustion development and the downstream production calibration (Fig.

7.1). When a particular set of combustion–fuel–air system hardware is

selected, it is important to predict the outcome of engine calibration during

the system design stage because any modications to inadequately designed

hardware during the calibration stage are extremely expensive. Engine system

design not only produces a specication for each subsystem design, but also

generates the simulated virtual performance and emissions regarding engine

calibration prior to the actual calibration testing.

The same analysis methodology is used as the optimization techniques

in the following three functional areas: combustion hardware screening,

system simulation and design, and calibration testing. The analysis method

is the design-of-experiments (DoE) combined with the response surface

methodology (RSM), as introduced in Chapter 3. A thorough understanding

of the hardware screening and calibration processes in the entire engine

speed–load domain under various situations (e.g., cold and hot ambient,

high altitude, aftertreatment regeneration) is critical for properly translating

the emission requirements to the air ow functional target, which is needed

by the engine system design as analysis input. This chapter introduces the

sensitivity of emissions to the calibration parameters. The method of setting

the engine system design target of airow requirements to meet emission

regulations is discussed. In addition, emissions modeling methodology is

briey reviewed.

7.2 Combustion and emissions development

7.2.1 Introduction to diesel emissions control

Compared with the gasoline engine, the diesel engine emits a similar amount of

(engine-out NO

), much more particulate matter (PM), and much less CO

and HC. Improving the air–fuel mixing and combustion processes can reduce

PM, but usually results in an increase in NO

. There exists a fundamental

trade-off between NO

and PM in the diesel engine. The NO

emissions from

the gasoline engine may be reduced by a three-way catalyst aftertreatment

device. But currently it is still very costly to use any aftertreatment devices

to clean the NO

from the diesel engine because the NO

is formed with

the air–fuel ratios much greater than those in the gasoline engine, and exists

in an oxygen-rich exhaust ow environment. Reducing the engine-out NO

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Emissions

regulation

Averaging,

banking and

trading strategy

Transient

feed gas emissions

target

Steady-state feed

gas (engine out)

emissions target

Combustion and emissions development

(search and tune different hardware) to

generate recipes and air ﬂow requirements

to meet emissions (i.e., air–fuel ratio,

EGR rate, intake manifold temperature

associated with certain heat release rate)

Correlation between

steady-state and transient

emissions

Production

tolerance and

margin

Vehicle driving cycle

simulation analysis and

design points selection

Aftertreatment performance,

efﬁciency and safety margin

(aging); regeneration

Conduct transient simulation to check

Iterate design

with testing and

recipe changes

Subsystems design to

procure engine hardware,

and conduct calibrations

Other functional areas (engine

controls, mechanical

durability testing, etc.)

Engine system design and integration optimization analysis

(exhaust restriction, valvetrain, turbo matching, EGR circuit,

heat rejection, cooling, engine brake, etc.); virtual calibration

Iterate design

with testing

results and

supplier design

changes

7.1 The process from vehicle, aftertreatment, combustion/emissions to system design.

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465Combustion, emissions, and calibration for system design

and PM while still maintaining low fuel consumption poses a signicant

challenge to diesel engine combustion and air system design. Note that NO is

largely formed during the premixed lean burn combustion phase with a local

excess air–fuel ratio at 1.0–1.2, and soot is mainly formed in the diffusion

combustion phase with insufcient air at a local excess air–fuel ratio lower

than 0.5–0.6. The heterogeneous local mixing between the air and the fuel

during the combustion process is the root cause of the soot emission in the

diesel engine. Achieving better mixing and preventing high NO

and soot

is the design goal of the air–fuel–combustion system.

Emissions control is also closely related to mechanical design. A typical

example is the lube oil consumption control to reduce the soluble organic

fraction (SOF) in PM emissions by using high-tension piston rings or a better

control on cylinder bore distortion with improved cooling jacket design. The

high-tension piston rings result in increased friction losses and durability

problems. Another example is using retarded fuel injection timing to reduce

. This leads to higher soot emission. Faster soot accumulation in the

lube oil would force more frequent oil changes for the customer. In fuel

system design, the demand of using a higher injection pressure to control PM

exerts a higher load on the injector mechanism. In that case, the lubricant

oil experiences a higher shear rate, and the oil viscosity improver additive

breaks down more quickly. More information on the effect of lubricant oil

on diesel emissions can be found in Manni et al. (1997), Stunnenberg et al.

(2001), Barr et al. (2003), and McGeehan et al. (2006). The effect of EGR

on diesel engine oil is discussed by Sasaki et al. (1997).

The following topics are important for diesel engine system design:

∑ emissions certication and the impact on engine performance strategy

∑ the impact of the conventional and innovative combustion systems on

engine system design

∑ the fuel system, ultra-low-sulfur fuels, and low-ash oils

∑ the intake manifold gas temperature and condensation controls

∑ the engine compression ratio

∑ cold start.

7.2.2 Combustion and emissions research

The following research ndings in diesel combustion and emissions are

important for engine system design. Automotive test drive cycles for emissions

measurement is reviewed by Samuel et al. (2002) and Taylor et al. (2004).

Early design guidelines for low-emission diesel engine design are summarized

by Gill (1988). The technical trends of diesel engine designs to meet emission

regulations are discussed by Mori (1997), Khair (1997), Browning (1997),

Dexter and Kling (1999), Hountalas (2000), Walsh (1999, 2001), Moser et

al. (2001), Wuensche et al. (2003), Pfeifer et al. (2003), Leet et al. (2004),

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466 Diesel engine system design

Charlton (2005), and Dollmeyer et al. (2007). Vehicle integration of low

emissions engines into commercial vehicles is summarized by a group of

experts at Navistar (Baus et al., 2006).

The heavy-duty diesel engine emission regulations are explained by

Charmley (2004). The US EPA Not-to-Exceed (NTE) and in-use emissions

are discussed by Krishnamurthy and Gautam (2005), Shade et al. (2008),

Thompson et al. (2008), Darlington et al. (2008), and Johnson et al. (2008).

The NTE regulation is a concept of heavy-duty emissions control that is

applied to both laboratory and on-road in-use testing. The effect of the NTE

regulation is to level the emission map and avoid or preclude the likelihood

of defeat devices. The NTE regulation covers an ‘NTE control zone’ in

the engine speed–load domain (i.e., speeds greater than the so-called 15%

European Stationary Cycle (ESC) speed, and engine loads greater than or

equal to the higher of 30% of the maximum power or 30% of the maximum

torque). The NTE regulation also covers a range of ambient conditions (i.e.,

the temperatures up to 38°C or 100°F, a humidity range of 0–100%, altitude

levels up to 1,676 meters or 5,500 feet). Engine manufacturers are required

to test customer vehicles for compliance with the NTE regulation. The reader

is referred to the current EPA website at www.epa.gov for more information

on the NTE standards and exclusions (e.g., exclusions due to not capable of

operation, 5% limited test, deciencies and auxiliary emissions control device

(AECD), cold temperature operation, and cold exhaust aftertreatment).

Diesel engine combustion is introduced in Bowman (1991), Borman and

Ragland (1998), and Hsu (2002). The fundamental mechanisms of the emissions

of modern diesel engines with EGR are reviewed by Reitz (1998). Fundamental

diesel emissions research has been carried out by Flynn et al. (2000), Kamimoto

and Bae (1988), Song et al. (2001), Akihama et al. (2001), and Bianchi et al.

(2002). It should be noted that the combustion similarity research to compare

different sizes of diesel engines was conducted by Chikahisa et al. (1992).

Emissions control and combustion technologies in engine designs have been

reviewed by Suzuki et al. (1997), Kanda et al. (2004), Thompson et al. (2004),

Zhu et al. (2004), and Czerwinski et al. (2007).

The interaction between the fuel spray and the air motion in diesel engines

is reviewed by Singal et al. (1993). The effect of air–fuel ratio on emissions

is discussed by Page (1996). The effect of EGR on diesel combustion and

emissions has been investigated by Shiozaki et al. (1996), Zelenka et al.

(1998), Ladommatos et al. (1999), Desantes et al. (2000), Simescu et al.

(2002), Tomazic and Pfeifer (2002), Langridge and Fessler (2002), and Jacobs

et al. (2003). The effects of fuel injection parameters and other engine design/

calibration parameters (e.g., swirl ratio, intake manifold gas temperature)

on combustion and emissions have been researched by Mather and Reitz

(1998), Wickman et al. (2000), Woods et al. (2000), Montgomery and Reitz

(2001), Henein et al. (2001), Shin et al. (2001), Payri et al. (2003), Zhu et

al. (2003), Dronniou et al. (2005), and Millo et al. (2007).

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467Combustion, emissions, and calibration for system design

Advanced diesel engine combustion (e.g., low-temperature combustion,

Yun and Reitz (2005)) is being actively developed in order to reduce the

engine-out emissions. It will have a direct impact on the emissions recipes

required for the system design. Understanding the advanced combustion

modes is important for a system engineer. Summary information on the

homogeneous charge compression ignition (HCCI) can be found in Zhao et

al. (2003), Najt and Foster (1983), Thring (1989), Christensen et al. (1998),

Stanglmaier and Roberts (1999), Baxter and Hiltner (2001), Epping et al.

(2002), Ryan et al. (2004), Narayanaswamy et al. (2005), Schleyer (2006),

Zhao (2007), and Cracknell et al. (2008). More discussions on HCCI are

provided in Chapter 9 related to VVA.

7.2.3 Diesel fuel injection system

Fuel system design and matching with combustion and air systems is a

highly important and specialized area for low-emission diesel engines. Fuel

system design is very complex and includes a wide range of components

such as low-pressure oil pump, high-pressure oil pump, fuel pump, fuel line,

oil/fuel rail, injector-rail adaptor, and injector. The design issues include

fatigue, distortion, vibration, noise, leakage, cavitation, lubrication, wear,

scufng, coking, ow restriction, ow distribution, and hydraulic pressure

uctuation, under a variety of hydraulic, thermo-mechanical, tribological,

and mechanical impact loads. Actuator performance degradation over

time, nozzle valve seat migration and nozzle ow loss due to lacquering

are common durability problems. Different types of fuel system (e.g.,

the electronically controlled unit injector, the unit pump, or the common

rail system) exhibit different performance, durability, and packaging

characteristics.

Fuel injection dynamics and fuel system performance largely affect

emissions, fuel economy, engine startability, load acceptance (acceleration),

and combustion noise. Fuel injection pressure, nozzle number, nozzle hole

size, injection rate, and many other design and calibration parameters need

to be optimized. The air system (e.g., for air–fuel ratio and swirl ratio) is

designed to match the capability of the fuel system for a given emissions

target. Generally, at a xed engine speed–load mode a simultaneous increase

of fuel injection pressure (or initial injection rate) and EGR rate may reduce

engine-out soot while maintaining a constant NO

. Pilot injection may

reduce combustion noise, especially at the idle mode or low speeds/loads.

However, pilot injection sometimes may adversely affect the NO

–soot

trade-off. Moreover, injection stability becomes more difcult to control

when the pilot quantities become very small. Flexible multiple injections

are desirable to control the emissions, the combustion noise, the transient

operation, and the aftertreatment regeneration. For example, post fuel injection

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