Performance Simulation of a Commercial Vehicle Engine ...

Knorr-Bremse Group

Performance Simulation of a Commercial Vehicle Engine using a Pneumatic Booster System

Dr. Huba NÉMETHKnorr-Bremse R&D Center Budapest

Frankfurt, 25th Oct 2010

2010 European GT-Suite Conference

Knorr-Bremse Group 2

Motivation for the Pneumatic Booster System developmentIncreased demands from customers and legislatives

Improvement of fuel economy (was always the strongest driver for the commercial vehicles)Fulfilling of future emission targets

Effective measures to fulfill the strongest demandsDownsizing PrincipleExhaust gas recirculation

Both requires increased charger pressure levels and often more than one charging stages

ResultWorse transient responseReduced drivability

In order to have good response and emission the same time, one needsAir demand control for the engine (proactive instead of reactive)New tool in transients – Air injection rate

Solution approach: Compressed air injection


The Pneumatic Booster System – PBS

Function of the SystemCompressed air injection from additional reservoir increases the intake manifold pressure enabling an increased fuel rateFast response electrically controlled flap used as back flow blockingBMEP increases immediatelyTurbo charger is heavily speeded up meanwhileThe process takes till the turbo charger reaches the target operation point

Compressed air injection into the intake manifold with backflow blocking

PBS

Turbocharger

Intake Manifold

Compressor

Additional Reservoir

Exhaust

EGR (optional)

Intercooler

Air SupplyControl Unit

Exhaust Gas Treatment


PBS with Double Compressed Air Injector

Different injector orifices

Different injector flow sections for better flow rate shaping


Simulation approachGoal of the investigation

Evaluation of engine performance improvement by PBSVehicle acceleration test with gearshifts

MethodologyGT-Suite model

Transient engine model with EDC– Employing DIWiebe combustion model– Mean value surge range extension of TC mapDriveline and longitudinal vehicle dynamicsCompressed air system

MATLAB/Simulink partPBS controller

The investigation is carried out as a multidisciplinary GT-Suite-MATLAB/Simulink co-simulation.

Main model parameters:

Manual, 6 gearsGearbox

Compressed air system

300 ccm, single cylinderCompressor

2 x 40 lBrake system tank

40 lPBS tank

Engine data

12.5 bar (relative)Cut off pressure

Dry friction clutchClutch

12 tonTotal mass

Vehicle and driveline data

620 Nm – 1400 rpmRated torque

150 kW (203 HP) - 2200 rpmRated power

TC, intercooledAspiration

16.9Compression ratio

1-3-4-2Injection sequence

4748 ccmDisplacement

105 x 137 mmBore x stroke

4Number cylinders


GT-Suite model - Overview PBS

PBS controller from Simulink


GT-Suite model – Pneumatic Booster Module

Booster Module includesPressure Sensors– Intercooler outlet– Intake manifoldActuators– Flap actuator– Air injector actuators (2x)– Sampled outputs (instead

of CA based RLTs)Connections to– Compressed air system– PBS controller

PBS


GT-Suite model – Compressed air systemBrake circuit tank1 – Front axle

Brake circuit tank2 – Rear axle

Multi-circuit protection valve

PBS tank

Compressor unloader control PBS injector

ports


Vehicle acceleration and engine torque response

Significant response improvement especially at lower gears

Reduced vehicle acceleration time

by 6 seconds


TC speed and pressure response

Turbo lag reduction by ~4.5 s, naturally aspirated like engine response achieved

Response time:

5 s => 0.3 s


PBS injection periodTarget boost pressure at first PBS activity: 2.5 bar, – boost duration 0.6 s

Typical boosting duration: 0.3-0.6s depending on target pressure level

Boost period

Injector modulation to maintain target

pressure


TC compressor trajectories and air temperature

Short stall line crossing during boost, manifold air temperature decrease during the boost by ~10 K


Air-fuel ratio and BSFC response

Air-fuel ratio increase by boosting results in BSFC and soot emission improvement


Fuel flow rate and vehicle fuel consumption

2.1% fuel consumption reduction achieved in this test case due to better BSFC and acceleration levels

2 - 4% fuel consumption improvement confirmed by extensive vehicle tests in representative cycles!

35.16 => 34.43

0.73 l/100km reduction


Compressed air tank and injector upstream pressures

After primary pressure drop in PBS tank a refill procedure occurred from the brake circuit tanks;

Reflections at injector closing causes pressure waves with >1 bar amplitudes

First boost periodPBS tank pressure drops

by boosting interventions


ConclusionsThe strategies for decreasing the fuel consumption and emission lead without additional measures to reduction of engine responses and drivability

Advantages of the newly developed Pneumatic Booster SystemImproved dynamic response of the engineSupport of engine downsizingSignificantly improved run up especially at high vehicle loadsReduction of fuel consumptionImproved emissions in transientsNew degree of freedom in the driveline design by– TC can be matched better for fuel economy than for dynamics– Transient soot emission reduction enables different DPF strategies


Thank you for your attention!

Dynamics under control – Knorr-Bremse Group

Performance Simulation of a Commercial Vehicle Engine ...

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