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HYBRID ELECTRIC VEHICLE

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					                    ADVANCES IN AUTOMOBILE ENGINEERING

                             HYBRID ELECTRIC VEHICLE




INTRODUCTION


            Each and every generation of human being tries to invent something as well as to improve the
performance of existing one. If we turn to see the developments from the birth IC engine we can see so
many techniques used in each and every century. Today the development of IC engine is no great. But we
cannot use it as itself. Because of the ambient air quality if the pollutant carbon monoxide (CO) reaches 3%
volumetrically in the air then within 30 minutes no human being will exist to live. So in order to safe guard
our forth-coming generation, it is essential to reduce the pollutants from today vehicle. Decrease in fossil
fuels also tuned to develop a better fuel economy vehicle. Hybrid vehicle technology (HVT) gives solution
for ours.


VEHICULAR EMISSIONS


            Deteriorating air quality is a major environmental problem. Most air pollution, which occurs in
highly urbanized areas with unfavorable topographical and metrological condition, is caused by motor
vehicles. During 1970-1990 the growth of vehicle that grew by about 250% (development countries). With
new economic and trade liberalization polices and the formation of various trade blocks the vehicle that is
expected to grow more quickly over the next decay. If appropriate measures are not taken soon urban air
pollution is likely to worsen posing a great threat to human health and welfare.




MOLECULES EMITTED FROM IC ENGINE: POLLUTANTS
CARBON MONOOXIDE (CO)
         It is a high toxic, colorless, odorless gas having high affinity (200 times that of oxygen) towards
the hemoglobin in the blood. This definitely posses a health hazard. Worldwide anthropogenic CO
emission for 1995 are estimated at 350 million tons. 59% of which are contributed by the transport section.


OXIDES OF NITROGEN (NOX)
         In the atmosphere it may be involved in a series of reaction that produce photochemical smog
reducing visibility. It may react with the chloride monoxide to form chlorides which releases ozone
destroying chlorine atoms upon reaction with hydrogen chloride. Worldwide anthropogenic NO X emission
for 1995 are estimated at 93 million tons. 43% of which are contributed by the transport sector.
HYDROCARBORNS (HC)
         Though it is not toxic, but when reacts with other compounds of atmosphere aldehydes are
formed, which irritates the eyes. It also plays an important role in forming NO 2 & O3, which are health and
environmental hazard.


SULPHUR DIOXIDE (SO2)
         It is extremely soluble in water. In the atmosphere SO2 may be converted to sulphur trioxide (SO3)
by reacting with oxygen. SO2 and SO3 react with moisture in air to form sulfurous and sulphuric acids
(H2SO3 & H2SO4), which may be transported by winds many hundreds of kilometers before falling to each
as acid rain. Annual Global emissions are estimated as 294 million tons with 6% share for transport sector.
PARTICULATE MATTER
         Particulate matter consists of fine solids and liquid droplets other than pure water. TSP is particles
with an aerodynamic diameter of less than 70micro meter. PM larger than 10micro meter diameter result
from physical action such as erosion or grinding action. PM with aerodynamic diameter 10 micrometer can
penetrate deeply into the respiratoty tract and cause illness in humans. I settles and spoils the exposed
surface of fabrics, building, trees, etc.
Pb COMPOUNDS
         It is used as an additive to increase the octane rating of SI engine fuel. The compounds of lead
affect the gastro-interestinal system.
US emission standard for new passenger cars


          1996-2003                  CO                 HC                  NOX                  PM


             G/Km                    2.6                0.19                0.37                 0.06



ANALYSIS OF THE ENGINE PERFORMANCE
         Before going to analysis it is necessary to understand the “driving cycle” or “duty cycle” in case of
the vehicles, which governs the pattern & sequence of power & energy demands by automotive vehicles in
urban conditions. The nature of this cycle is determined partly by the physical characteristics of the vehicle
& partly by its relationship with the road & with other traffic & partly by the behavior of the driver. Fig
shows two driving cycles defined cycles defined by the US EPA for regularity purpose.




         Comparing fig1, fig2 shows driving the vehicle in urban conditions frequent accelerations &
deceleration are happened. Now we can see the engine performance during acceleration, deceleration/idling
or cruising range.


STARTING AND IDLING / DECELERATION PERIOD
         During the period, the BSFC is infinite. Because consumption of fuel with no load. Rich mixture
is used in this period because of minimum throttle opening. The rich mixture, leads to more amount of
emission of HC & CO as shown in fig.


CRUISING PERIOD
         During this period stochiometric A/F mixture is used. So that minimum BSFC occurs. But the
emission of NOx will be more in this period. HC &CO emission will be considerably minimum.


ACCELERATION &HEAVY LOAD OPERATION
         In this period the speed of the engine is raised up to its maximum level. A rich mixture is also
supplied in this period. These causes
                     1.   Increase in FMEP.
                     2.   Decrease in volumetric efficiency.
                     3.   Retardation of spark timing from MBT.
                     4.   Increase in pumping loss.
                    5.   Incomplete combustion.
                    6.   Maximum emission of HC &CO.
         All the above factors increase the increase in fuel consumption per hour.


DISCUSSION FROM ANALYSIS
         If the number of stops per kilometer increases then there will be more wastage of fuel due to more
number of acceleration, deceleration & idling & it increases the amount of emission of pollutants HC &
CO.
         If a passenger car gives 14kmpl in highway driving it will give 7kmpl in city driving because of
the above problem. So that 50% of fuel loss is occurred. If poor traffic occurs then it leads to more than
60% loss of fuel.
         The amount of HC & CO emissions in the city driving is 3-4 times greater than highway driving
which leads to a very worsen ambient air quality in urban areas.
         The economy and exhaust emission of an engine are known to be influenced by quite a number of
design and operation parameters. A passenger car engine is operated through a wide load and speed range,
and any change of engine load, speed pressure and temperature requires an individual adjustment of these
parameters in order to make optimum use of fuel energy involved. And it is practically impossible to ensure
a continuous change of design parameters such as C.R, displacement, number of cylinders etc, The engine
layout will always constitute a compromise between such criteria. Hence today‟s engine can be called as a
“compromise engine”.
         An alternative drive is required to give a good solution for poor fuel economy and high rate of
emission in urban driving conditions of a vehicle. HEV becomes the best solution.


HYBRID ELECTRIC VEHICLE
         With a concept hybrid vehicle design, we explain how hybrid vehicle technology.
                    The Z-HEV we go to design is a
                                       Medium passenger car
                                       Maximum speed 130 Kmph
                                       Gross vehicle weight 1350 Kg
         Power required for the vehicle can be calculated by the formula
                    Pveh = 1.1*(V/217) {[w/g. ac/ka] + [kaAV.kaAV] + [(a+bv).w]}…hp
                             W = 1350 kg                Gross vehicle weight
                             Ac = 0.3                   Acceleration at max power
                             KA = 0.9                   Acceleration constant
                             A = 0.0032                 Aerodynamic constant
                             V = 117 kmep               Vehicle speed at max power
                             a = 7.6                    constant
                          b = 0.05625                 constant
                          v = 130 kmph                maximum vehicle speed


        Substituting these values
                          Pvehicle = 70 hp
        These main power components are used instead of a single ICE. They are
                 (1) Integral starter generator flywheel
                 (2) Rear motor
                 (3) IC engine
        The total 70hp required is redistributed to the three main power components according to the Z-
        HEV driving mode as given below,




                                    Z-HEV DRIVING MODE
Drive                Series hybrid drive     Conventional drive     Parallel             Hybrid drive
Vehicle speed        Speed          upto     40-70kmph              70-100kmph           Above 100 kmph
                     40kmph
Driving power        Rear motor only         IC engine only         IC engine    +rear   IC    engine+rear
                                                                    motor                motor+ISGF


From the driving mode power required for each unit
        Rear motor --19hp
        IC engine -- 42hp
        ISGF       -- 9hp
GEAR BOX
        4 speed gearbox can be used.
From the formula N/V =2.65G ra/Rw the gear ratio for Z-HEV can be selected as follows
                 Axle reduction     =2.58                        speed range
                 I gear ratio       =3.38                        23-38kmph
                 II gear ratio      =2.29                        34-56kmph
                 III gear ratio     =1.56                        50-83kmph
                 IV gear ratio      =1.0                         78-130kmph


CHOICE OF ENGINE
         Various approaches toward reducing the exhaust, NOx emission techniques are related to fuel
economy.
         Approaches are
                  1. Rich mixture with / without EGR
                  2. Lean mixture without EGR
                  3. Stoichiometric mixture with heavy EGR
                  4. Retarded ignition timing.




         It is a very interesting technical subject to study which approach especially stoichiometric mixture
with heavy EGR or very lean mixture without EGR is more advantageous to achieve large reduction of
NOx along with good fuel economy. For the study of this subject, improvement of combustion in the
cylinder should be carefully examined.
         Combustion stability under heavy EGR is greatly improved by the fast burn concept it is to
introduce more EGR and to achieve lower NOx level than conventional engine. Fast burn extends not only
EGR limits but also lean operating limit.
         Hemispherical combustion chamber with petrol injection system and spark plug arrangement will
be a fast burn engine. The reason why EGR is superior to lean mixture for NO x reduction would be lower
oxygen content and higher heat capacity of the charged gas to the cylinder.
         An inlet air conditioner is used to minimize the effect of inlet air temperature and humidity
fluctuation on the engine emission data especially on NOx.
         Combustion duration of fast burn engine with 20% EGR is almost the same as that of conventional
engine without EGR. EGR rate at the engine stability limit in fast burn engine is 33%, which is 15% higher
than the conventional.
         It is recognized that stable operating zone is wider and both lower NO x level and better fuel
economy are achieved. From the graph we can clear about the fast burn engine.


CHOICE OF MOTOR
         Though there are so many types of AC & DC motors, WOUND-ROTOR INDUCTION MOTOR
will be the best choice for HEV. Because of its cheapness, rigid and less maintenance and good operation
characteristics. Selecting wound – rotor motor is induction type motor the starting torque can be increased
by three external resistors. The mechanical characteristics of wound round motor is shown in the figure.




Features of wound rotor induction motor
         1.   Start up of very high inertia loads.
         2.   Easy speed control by pwm
         3.   The external resistors can be varied as the motor picks up speed. As a result, it is possible for
              the motor to develop its max torque during the entire acceleration period.
                            Required motor capacity 7.5 AH.
SPEED CONTROL BY PULSE WIDTH MODULATION (PWM)
         The most efficient methods of speed control available on a practical basis today use a solid state
chopper circuit that limits the current to the motor. It is achieved by SCRS. The accelerator usually controls
a small variable resistor that is not located directly in the high current path. Very little power is lost in this
resistor & efficiency is very high. When the accelerator pedal is initially activated, a few pulses of voltage
and current per second are applied to the motor. As the accelerator pedal is further depressed the pulse
duration and width increases at a fairly linear rate. By carrying the number of power pulses per second and
the duration or width of each individual pulse, the chopper circuit effectively limits the current applied to
the motor from the bank of batteries.




CHOICE OF BATTERY
         All types of battery from lead-acid type, lithium-ion type battery will be the best choice of battery
to HEV. Lithium-ion battery pack is approximately 70% lighter than an equivalent part using conventional
lead-acid technology is its tolerance to high electric current when recharging. Unlike other battery system
lithium-ion packs immune to the so called “memory effect” retaining full charging capacity regardless of
usage.
                  Peak power        : 30kw
                  Nominal voltage : 280v
                  Weight            : 70kg




SPECIAL FEATURES OF HYBRID ELECTRIC VEHICLE
         The hybrid system combines benefits parallel & as well as the conventional drive system. The
flywheel is designed as integrated starter generator. So that starter motor and alternators are eliminated.
Low power engine is used so that the weight of the engine is reduced. Hence the total weight of the vehicle
can be maintained as the conventional vehicle. The engine used in HEV can be called as “precisions
engine”. Because the engine is only used for a small range of speed (1500-2500 rpm) & load. So that
maximum efficiency of the engine can be got.
         In the slow of the vehicle, motor is used as the power source. So that the vehicle acts as a zero
emission vehicle. Throughout the complete operation emission from the vehicle is almost constant. Due to
small variations of speed and load of the engine.
         The gearshift sensors are used, so that if the vehicle climbs a hill the first gear is mainly used. So
that all the three power unit come to operation unnoticed by the vehicle occupants. But for shifting from 40
kmph, 70 kmph, 100 kmph to above shift button should be pressed by the driver. While reducing the speed
by breaking the vehicle the shift from high speed to low speed will happen automatically by the „MICRO
COMPUTER‟. While breaking the brake pedal position sensor senses the amount of movement of the
pedal and its velocity of movement and the signal sent to the microcomputer, which gives signal to the rear
motor controller to act the rear motor as a generator. So that the braking energy is absorbed.
         The hybrid vehicle can be converted to a stationary electrical generator to drive up to 10kw of
power for work, recreation, or home use.
         Up to 40kmph speed of the vehicle there is no need to use gears. This facilitates the parking and
starting of the vehicle in simple manner. An electric control mechanical clutch is used so that the flow of
power from the engine to the rear wheels is cut-off while the speed of the vehicle is below 40 kmph and the
power of the engine is used for charging the battery by the use of integrator starter generator to act as
generator.
         A battery management system constantly monitors the modules both during operation and while
they are being recharged. Data concerning cell voltage, battery charge status and the operating temperature
of the battery module are passed through an on board communication network to the central
microcomputer. The flow of electricity from the battery unit is automatically shut off if the system is
farmed to off or if the sensor defect a crash.
         Emission from HEV is reduced 4-5 times than conventional vehicle. Fuel economy is achieved
more than 60% than conventional vehicles.
         To ensure electric safety, the systems high voltage parts are enclosed in the pack. These parts
consist of a system main relay (SMR) with a built in ampere sensor, a service plug with a built in fuse a
battery ECV.
         The total cost of this Z-HEV car will be around 15 lakes. So that hybrid vehicles will be the
cleaner drive, which is an urgent need for today‟s environment.




CONCLUSION
                   Considering the rate of polluting the air by vehicles & the decrement of fossil fuels,
hybrid vehicle technology is the urgent need to solve the problem. The high cost of the electric components
increases the total cost of the hybrid vehicle. But in future vehicle system costs will be made equivalent to
conventional IC power trains.


REFERENCE
“Fuel economy and emission of lean burn engines”-I MECH CONFERENCE PUBLICATIONS
Eleventh national conference on IC engines and combustion-IIT madras
“The passenger car power plant of the future”- I MECH CONFERENCE PUBLICATIONS
EDWARD. F. OBERT,” Internal combustion engines and air pollution”
Dr. S.SUBRAMANIAN,” Advances in Automobile Engineering
RICHARD STONE, “Introduction to internal combustion engines”
JOHN. B. HEYOOD, “Internal combustion engine fundamental”
THEOGARG WILDI, “Electrical machines, drives and power systems.
BETIRO NIRSAL, SURHID. P. GAUTUM, “Vehicular air pollution”
W. SHEPHERD, L. N. HULLY AND TW.LIANG, “Power electronics and motor control”
“AUTOMOTIVE ENGG INTERNATIONAL” Magazine-MAR, DEC, MAY, JUNE-2001, FEB-2002.


DECLARATION

         We hereby declare that this paper and its contents solely belong to us and this

our first venture in this paper.


                                                            Signature of the candidates,




                                    K.SURESH & P.KARTHIKEYAN.

                                    Final year, Department of Automobile Engg.,

                                    Institute of Road and Transport Technology,

                                    Vasavi College (P.o),

                                    Erode-638 316

                                    E_mail: autocreat@yahoo.com