Department of Mechanical Engineering
K Pavan Kumar,11781A0347,IV year, mechanical Dept,SVCET, Chittoor.
Presented by
Twin Turbo Technology
Introduction :
The power out put of an engine depends upon the amount of air inducted per unit time
and the degree of utilization of this air , and the thermal efficiency of the engine.
Indicated engine Power
IP=P*L*A*n*K/60000
Where,
IP= indicated power (kW)
P=indicated mean effective pressure(N/m2)
L=length of stroke
A= area of piston
n= no of power stroke, for 2-s engine-N and for 4-s engine N/2, N= rpm
K= No of cylinders
Three possible methods utilized to increase the air
consumption of an engine are as follows:
Increasing the piston displacement: This increases the size and weight of the engine, and introduces additional cooling problems.
Running the engine at higher speeds: This results in increased mechanical friction losses and imposes greater inertia stresses on engine parts.
Increasing the density of the charge: This allows a greater mass of the charge to be inducted into the same volume.
Definition
The most efficient method of increasing the power of an engine is by
supercharging, i.e. increasing the flow of air into the engine to enable
more fuel to be burnt.
A Supercharger is run by the mechanical drive, powered by engine power .
A turbocharger uses the otherwise unused energy in the exhaust gases todrive a turbine directly connected by a co-axial shaft to a rotarycompressor in the air intake system.
Introduction :
The parameters which take the centre stage of the competition in car
today are efficiency, power, and environmental safety.
One technology that is going to be the heart of the future diesel cars is
TWIN TURBO technology.
Unlike the Bi-Turbo mechanism, this Twin Turbo is a combination of
two turbo chargers mounted serially rather than in parallel.
The only car in India, which has this facility, is Hyundai i20.
Super Charger
Turbo Charger( schematic diagram)
Need of turbocharger and super
charger
For ground installations, it is used to produce a gain in the power out put of the engine.
For aircraft installations, in addition to produce a gain in the power out put at sea-level, it also enables the engine to maintain a higher power out put as altitude is increased.
Turbo Charger
A turbocharger is practically a turbine that is fuel-driven.
A turbocharger, often called a turbo, is a small radial fan pump driven
by the energy of the exhaust flow of an engine.
A turbocharger consists of a turbine and a compressor on a shared axle.
The turbocharger increases the pressure at the point where air is
entering the cylinder, a greater mass of air (oxygen) will be forced in as
the inlet manifold pressure increases.
Working principle of a turbocharger:
A turbocharger is a small radial fan pump driven by the energy of theexhaust gases of an engine.
A turbocharger consists of a turbine and a compressor on a sharedshaft.
The turbine converts exhaust to rotational force, which is in turn usedto drive the compressor.
The compressor draws in ambient air and pumps it in to the intakemanifold at increased pressure, resulting in a greater mass of airentering the cylinders on each intake stroke.
Where the turbocharger is located in the car
0
2
3
41
Four-stroke cycle of an SI engine equipped with a
supercharger turbocharger, plotted on p-v coordinates.
Thermodynamic analysis of turbocharged engine
cycle
Net work output Wnet= work done by piston + Gas exchange work= area A + area
Area A=
Area B= work done by turbocharger=
Wnet = Work done per unit of air mass.Where, p0 = atmospheric pressure,p1= pressure after compression,T0= atmospheric air temperature,V1= volume of boosted air,rp =pressure ratio,r = compression ratio, cp=Specific heat of air
and η = turbocharger efficiency,
Selection process of turbocharger
Illustration of the concept of a turbocharger.
•Compressor air inlet,Point1- p1, T1•Compressor air out let, point2-p2, T2•Turbine exhaust gas inlet, point 3-p3,T3•Turbine exhaust gas outlet-P4, T4
The compressor efficiency = ( theoretical temperature rise across the compressor)/(the actual temperature rise). ec is always less than 1.0.
The turbine efficiency = ( the actual temperature drop across the turbine )/(the theoretical temperature drop). The turbine efficiency is also always less than 1.0.
The mechanical efficiency of the turbocharger
Types of Turbo Chargers
Single Turbo Charger
Twin – Turbo Charger
Single Turbo Charger
Single Turbo, a single turbo
requires all 8 cylinders in
order to build some boost.
Produces good results for drag
racing, which needs extremely
high power.
Single Turbo Charger
Single turbo engines are easier
to set up.
There are super large single
setups that can support up to
1500BHP, can create real
power but there is that
unwanted lag.
Doesn't take up much space in
the car.
Twin-Turbo Charger
The secret behind "twin-turbo" is
the clever two-stage forced
aspiration principle.
The revolutionary twin-turbo
technology, the next big step
forward in the development of
modern diesel engines for
passenger cars.
Twin-Turbo Charger
The car with the Twin-Turbo mechanism gives more power, more torque,better mileage, and a comprehensive pollution free engine than its rivals.
ENGINE SPEED BELOW 1800 RPM:
By using a small high-pressure turbocharger for the first
stage, the engine responds readily to the gas pedal at lower
speeds without suffering from "turbo lag".
Up to 1800 rpm this high-pressure turbocharger works
alone and compresses the intake air at up to 3.2 bar boost
pressure.
ENGINE SPEED BETWEEN 1800 -
3000 RPM:
Between 1800 and 3000 rpm, a larger low pressure turbocharger joins
in - both turbines run together in this engine speed range.
The exhaust from the cylinder will drive the first turbo charger and
come to the second. This will leads to the working of the second stage
turbo charger it affects in the intake air. This intake air which is needed
for the combustion is sucked in and goes to the first stage turbo charger
which will pressurized the air and goes to the cylinders.
ENGINE SPEED ABOVE 3000 RPM:
Above 3000 rpm, only the larger turbocharger continues to deliver
charge air to the cylinders.
The complex control of both chargers is via a valve in the engine's
exhaust system, controlled by engine speed and load.
POTENTIAL OF THE TWIN TURBO-
CHARGER
The enormous potential of a twin-turbo engine can be seen
from the mean effective pressure values it achieves.
Whereas traditional turbo-diesels have a mean effective
pressure of 17 to 19 bars, the 1.9-litre twin-turbo reaches
26 bars.
EFFICIENCY: 212 hp from 1.9-liter engine with fuel consumption of only 6.0
l/100 km
Compared with a naturally aspirated diesel engine, power outputs can
be raised by up to 50 percentages without increasing fuel consumption.
Alternatively, consumption can be reduced by as much as a quarter
without loss of power.
This high-tech engine delivers a peak power output of 156 kW (212 hp)
from just 1.9 litters displacement.
With this engine the Vectra OPC accelerates from 0 to 100 in 6.5 seconds;
the top speed is an electronically regulated 250 km/h.
At 6.0 litters per 100 km in the European test cycle
Vectra OPC
Type of Twin-Turbo
After the revolution of the two-stage turbo-charger, there are two ways in
which the turbo-charger can be mounted. They are parallel and
sequential.
Parallel:
Sequential:
APPLICATIONS:
Everybody knows mechanical superchargers are good for low-end output but
short of efficiency at high rev, while exhaust turbochargers works strongly at
high rev but reluctantly at low rev. For decades engineers dreamed of
combining supercharger and turbocharger together. This was tried once in
history – the 1985 Lancia Delta S4 rally car.
1985 Lancia Delta S4 rally car
APPLICATIONS:
In 2005, Volkswagen finally introduced a production unit toits Golf 1.4 TSI. Called "Twin charger" system.
APPLICATIONS:
The only car in India, which has this facility, is Hyundai i20.
Advantages
The environmental safety standard is the major consideration today, this
technology is EURO V ready.
Even though the car delivers a much higher power than its counterparts, it still
maintains the conventional 16.5 KMpL as mileage.
At 1500 rpm, both chargers contribute about the same boost pressure, with a
total of 2.5 bars. (If the turbocharger works alone, it can only provide 1.3 bars
at the same rev.)
In the 1.4-litre Golf, the Twin charger system produces 170 horsepower and
177 lbft of torque. That's equivalent to a 2.3-litre normally aspirated engine
but it consumes 20% less fuel.
Advantages
The more increase the pressure of the intake air above the local atmosphericpressure (boost), the more power the engine produces. Automotivesuperchargers for street use typically produce a maximum boost pressurebetween 0.33 to 1.0 bar, providing a proportionate increase in power.
Engines burn air and fuel at an ideal (stoichiometric) ratio of about 14.7:1,which means that if you burn more air, you must also burn more fuel.
This is particularly useful at high altitudes: thinner air has less oxygen, reducingpower by around 3% per 1,000 feet above sea level, but a supercharger cancompensate for that loss, pressurizing the intake charge to something close tosea level pressure.
Disadvantages
Cost and complexity
Detonation
Parasitic losses
Space
Turbo lag
CONCLUSION:
From this, it is clear that the vehicle, which use thisadvanced technology, has proved to be more efficient andmore powerful. So let’s hope that the recent automobile willuse this technology and gets modernized.
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