الفهرس 
PREVIOUS WORK AND OUTLINE OF THE PRESENT WORKOnly 14 pages are availabe for public view
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Abstract
The max11num rating of diesel engmes , as governed by the mass of air available for
efficient combustion has increased steadily since the introd uction of turbochargers . As
the turbocharger is powered by exhaust gas energy , its steady state speed varies with the rack
position of the fuel pu mp and engine speed . However quick changes m rack position do
not resu lt in instantaneous response of the turbocharger , due to its inertia and
compressi bi lity of the exhaust gases link from the engine . The lag between the rate of
change of air flow and fuell ing leads to rapid changes in the overall air-fuel ratio
insi de the combustion chambers .
In transien t cond it ion at wh ich large changes of fuell ing occures
excessi vely rich supply becomes
mi xtures are developed and consequentl y the air the controll ing factor . In
the presen t work ,
matchi ng turbochargers componen ts as a system as well as to the engine i s the major issue ,
and studying the matchi ng process during transient operating cond itions is very importan t to
meet the requ irements of the engine during these period . To veri fy this purpose a non-l inear
digital simulation of turbocharged diesel engine has been developed to pred ict
transient performance . The quasi steady ” filling and emptyi ng ” approach has
been employed in the analysis of the thermo and fluid dynam i cs under transi ent
engine cond i tion s . The t u rbocharger i s also treated on a quasi steady basi s , with the
aid of steady state performa nce characteri sti c. I n order to faci l i tate the computat
ions , the proposed model employs a correlat ions to sim u l ate compressor and tu rbi ne
characteri stics . By applyi ng conservat ion law ( energy , mass and angu l ar momentum
) and the ideal gas equati ons ,
a set of coupled ordinary differential equations 1s obtained m the form of an initial
value problem .
Governing equations are numerically integrated in a simultaneous manner along equal steps of
crank angle increments.
The combustion model is based on the fuel burning rate approach . Emprical burning rate curves for
the other workers are correlated for ignition delay , engine speed and equivalence fuel-air ratio .
Injection delay 1s taken as the duration of propagation of a pressure wave along the fuel
pipe . Heat transfer to the cylinder walls is evaluated from wall surface and instantaneous
gas temperature and the wall temperature has been determined using VOSHNI’s correlation .
The instantaneous valve area as well as the pressure difference has been taken into
account for calculating the gas flow through the valves . Friction torque 1s also
computed as a function of engine speed and maximum cylinder pressure according to Willan ’s
approach .
Comparison of experimental work for different authers data and predicted results for the
present work shows fair agreement in most cases within the accuracy of the measurements
. Effect of varymg compressor characteristic, engine cylinders number on the transient response
of the engme are predicted and discussed. Evaluation of matching process are considered
,especially during the transient operating condition . A modified model is proposed to meet the
requirements of the engine during such period .
Finally it is concluded that the model can be used as a research and development tool
, particularly in studying the feasibility of design options aimed to improving transient
performance of turbocharged diesel engines , and to study how to chose the suitable
turbocharger which give a good matching between the turbocharger and the engine
under all engine operating conditions .