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Investigation Concerning the Effect of Post Fuel Injection on The Performance and Pollutants of Heavy Duty Diesel Engines Using a Multi-Zone Combustion Model

  • D. T. Hountalas
  • D. A. Kouremenos
  • E. G. Pariotis
  • V. Schwarz
  • K. B. Binder
Conference paper

Abstract

As widely recognized the direct injection heavy-duty diesel engine is the most efficient powertrain system for trucks, lorries and other heavy-duty vehicles. This results from its relatively low specific fuel consumption compared to other existing thermal engines. Taking this under consideration it remains a serious problem, its relatively high, compared to future legislation, NOx and particulate emissions. Manufacturers have proposed various solutions towards this problem. Two are the main categories proposed, improvement of the combustion process to control directly the formation of pollutants inside the combustion chamber and the use of aftertreatment technologies to reduce pollutants at the engine exhaust. In the present work we will concentrate our efforts on the first category by examining the technique of post fuel injection. For this reason a multi-zone phenomenological model is used to examine the effect of post fuel injection on pollutants emissions and bsfc. The study is conducted using a single cylinder heavy-duty test diesel engine capable of withstanding relatively high peak combustion pressures. The simulation model has been used to examine the effect of post fuel injection at various operating conditions corresponding to key operation points of the engine under question. During the investigation, various injection timings are considered setting the peak combustion pressure limit to 200–220 bar. In all cases, the effect of the interval between the main and the post fuel injection is examined. From the analysis of results, important information is derived concerning the effect of post fuel injection parameters on engine performance and emissions. The results are given in the form of NO-bsfc and Soot-NO curves to obtain a clear picture of the effect of post injection. Furthermore results are provided concerning the pollutant formation mechanism i.e. Soot and NO formation history inside the combustion chamber. As revealed post injection seems to have no serious effect on NO emissions since it occurs at the late stages of combustion, but on the other hand it seems to have a serious effect on Soot emission. The effect on Soot emission depends on the interval between the main and the post fuel injection. Post injection has a small penalty on bsfc but this is compensated by the serious reduction of Soot. Comparing the results with published data concerning the effect of post injection on engine performance and emissions, they appear to be at least qualitevely correct. However it remains to verify them using experimental data. Another important outcome of the present investigation is that phenomenological modeling is a promising tool to study such cases since it is very fast and can contribute to the reduction of development cost. These models cannot be directly compared to multi-dimensional sophisticated ones since the last concentrate on the detailed modeling of the various processes occurring inside the cylinder, but in the time being it is an efficient way to conduct overall engine performance and pollutant emission studies where a great number of parameters are involved. From the experience up to now, it seems that phenomenological models can produce results that can reveal trends despite the possible differences when comparing predicted absolute values with the corresponding measured ones. For this reason we believe that the use of such models is a promising tool for engineers who want qualitative results before conducting a more detailed investigation using CFD models.

Keywords

Diesel Engine Engine Speed Fuel Injection Post Injection Soot Formation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notation

A

Area, m2

C

Mass concentration

c

Constant in heat transfer relation

cr

Radiation constant, W/m2K4

cv

Specific heat capacity under constant volume, [J/kg K]

dinj

Injector hole diameter, m

D

Cylinder bore, m

Db

Piston bowl diameter, m

Dd

Droplet diameter, m

DSM

Sauter mean diameter, m

E

Activation energy, J/kmol

fcor

Constant for air-entraintment adjustment

h

Heat transfer coefficient W/m2K

k

Turbulent kinetic energy, J

kif

Forward reaction rate constant for the “ith” reaction

l

Length, m

lcar

Characteristic length, m

L

Breakup length, m

m

Mass, kg

Mass flow rate, kg/s

n

Total number of zones or axial velocity distribution function exponent

N

Engine rotational speed (rpm)

P

Pressure, Pa

\(\dot Q\)

Heat rate, W

r

Droplet radius, m, or radial space coordinate, m

rc

Jet cross section radius, m

rinj

Injector hole radius, m

R

Radius, m

Ri

One way reaction rate for the “ith” reaction

Rin

Cylinder-valve axis distance

Rmol

Universal gas constant, J/kmol K

t

Time, s

tbreak

Break up time, sec

thit

Time needed for the fuel spray to hit on cylinder walls, sec

T

Temperature, K

u

Velocity, m/s

up

Penetration velocity, m/s

V

Volume, m3

W

Air angular velocity, rad/s

x

Space coordinate, m

z

Axial space coordinate, m

Greek

α

Initial jet angle, rad

ΔP

Pressure difference in fuel injector, Pa

εt

Viscous dissipation rate per unit mass, W/kg

Θ

Angle of injector axis projection with axis “x ” on plane “x,r”

λ

Thermal conductivity, W/m K

μ

Dynamic viscosity, kg/m s

ν

Kinematic viscosity, m2/s

ρ

Density, kg/m3

σ

Surface tension, N/m

Φ

Angle of injector axis with the “x,r” plane

Φeq

Equivalence ratio (fuel-to-air)

φ

Angular position of a zone

Subscripts

a

Air

b

Burned, bowl

c

Solid body core, combustion, cylinder

ev

Evaporated, fuel

f

Fuel

g

Gas

i

Zone identification number (r direction)

j

Zone identification number (z direction)

inj

Injection

l

Liquid fuel

o

Initial coordinate system, oxygen

p

Potential flow core, piston

r

Direction normal to the ‘x’ axis

s

Soot

sb

Soot burning

sf

Soot formation

w

Wall

x

Jet axis (initial) direction on the cylinder cross plane

z

Cylinder axis direction

Abbreviations

ATDC

After top dead centre

BTDC

Before top dead centre

CA

Crank angle

PLN

Pump Line Nozzle Injection System

Dimensionless Groups

Nu

Nusselt number

Pr

Prandtl number

Re

Reynolds number

We

Weber number

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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • D. T. Hountalas
    • 1
  • D. A. Kouremenos
    • 1
  • E. G. Pariotis
    • 1
  • V. Schwarz
    • 2
  • K. B. Binder
    • 3
  1. 1.Mechanical Engng Department, IROON POLYTECHNIOU 9National Technical University of AthensAthensGreece
  2. 2.Engines Injection Systems DevelopmentDaimler-Chrysler AG Powersystems Business UnitStuttgartGermany
  3. 3.Daimler-Chrysler AG Truck Engine Developing Dep.StuttgartGermany

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