TURBOCHARGER

The main objectives of turbocharger is

To increase the volumetric efficiency of an

engine for that power output will increase by

pressure charging.

To reduce Hydrocarbon and carbon monoxide

exhaust emissions.

To achieve better fuel economy

Increased air mass allows more fuel to be burnt, for that bmep will increase and finally increases power output

Air charging is achieved by pre-compression of intake charge by some type of compressor.

Turbocharging can be done only in CI engines

Supercharger(race cars)

Power determined by Rate of mass flow of air

A turbocharger is increases the pressure or density of

air supplied to an IC Engine. This gives each cycle of

the engine more oxygen, letting it burn more fuel and do

more work, thus increasing power output.

Turbocharger - Runs at high speed(75,000rpm – 100000rpm)

Inc. density, suitable for CI-now reasearch is going in SI (bcz of

knocking-we expect implement in 2020-the.efficiency SI-35%-

remaining 65%-1/3rdheat loss, 1/3rd exhaust loss-

rem.Unaccounted loss-

TC application:1st-battle tank

2nd-attitude

3rd-Aircraft

• A supercharger is an engine-driven air pump that supplies more than the normal amount of air into the intake manifold and boosts engine torque and power.

• A supercharger provides an instantaneous increase in power without the delay or lag often associated with turbochargers. – However, a

supercharger, because it is driven by the engine, does require horsepower to operate and is not as efficient as a turbocharger.

A turbocharger is a small radial fan pump driven by the energy of

the exhaust gases of an engine.

A turbocharger consists of a turbine and a compressor on a shared

shaft.

Important Parts of Turbocharger: Turbine, compressor, Ball

bearings & Fluid Bearings - Intercooler

The turbine converts exhaust to rotational force, which is in turn

used to drive the compressor.

The compressor draws in ambient air and pumps it into the intake

manifold at increased pressure, resulting in a greater mass of air

entering the cylinders on each intake stroke.

An intercooler is any mechanical device used to cool the air

between stages of a multi-stage turbocharger, typically a heat

exchanger

Turbocharger

FIG.3

Battle tank

Aircraft

Figure 1

A Turbocharger consists of a compressor and a turbine connected by

a common shaft. Centrifugal compressors and centripetal turbines

are most popular types used in automotive applications and form the

basis for most turbochargers today.

Constant Pressure Turbocharging

Pulse Turbocharging

The kinetic energy of the exhaust gas exiting from the cylinders is

mostly recovered.

The exhaust manifold will be bifurcated to join the cylinders, which

do not interfere during gas exchange process.

Turbine housing is divided to accept the exhaust pulse from each

branch of the exhaust manifold.

Better low speed engine performance

The pressure pulsation is smoothened out by relatively large exhaust manifold.

Large marine engines, Gensets and Industrial engines use this type.

Types of supercharger Positive displacement blowers - fixed volume of

air per revolution at all speeds

Non-Positive displacement blowers - volume of air per revolution at all speeds is not constant

ENGINE MATCHING OF EXHAUST GAS TURBOCHARGER

Although the installation of a turbocharger on the engine is quite simple, the

engine must fulfill certain pre-requisites. These are:

Thermodynamic compatibility of the engine and the turbocharger over the

complete operational range of the engine. Based on the application of the engine

the majority of the operating points (load – speed characteristics) should lie in the

efficient operating range of compressor and turbine characteristics.

Mechanical integrity of the engine:

The engine components must be able to withstand the thermal and mechanical

stresses which are likely to be higher than the naturally aspirated engine.

The objective in matching the turbocharger to an engine is to find the right

combination of turbocharger compressor and turbine to suit the engine and its

application. The pre-requisite for a successful matching needs development of a

number of compressor & turbine modules to cover all intended applications.

This matching requires very close co-operation between the engine and

turbocharger manufacturers.

Thermodynamic analysis of naturally aspirated engine

cycle

po

0

2

3

4

1

PV Diagram of turbocharged Four-stroke engine

Thermodynamic analysis of turbocharged engine cycle

VTG allows the turbine flow cross section to be varied in accordance with the engine

operating point. VTG has variable guide vanes. As a result of continuous turbine

cross section adjustment to the engine airflow requirements, SFC and emissions are

reduced. High engine torque at low speeds and with adequate control strategy

ensures a significant improvement of dynamic performance.

Guide vane control is mostly electronic through a vacuum regulated actuator and a

proportional valve. Electric actuators with position feed back are also used for vane

control.

Torque-motor DC motor

ADVANTAGES OF THE EXHAUST GAS TURBOCHARGER :

• The turbocharged engine has a number of advantages over naturally aspirated

engine.

• No gearing is required between the gas turbine and compressor

• Power – to - weight ratio of the turbocharged engine is higher than with a

naturally aspirated engine.

• Its suitable for high speed engine and it require limited space

• Its increase the pressure of the intake air above the local atmospheric pressure

for that maximum power is produced

• The size of the turbocharged engine is smaller than that of naturally aspirated

engine of equal output.

• The high altitude power loss of turbocharged engine is significantly less than

that of naturally aspirated engine.

• The turbocharged engine has a reduced specific fuel consumption since part of

the exhaust gas energy is utilized in the turbocharger.

• The turbocharged engine is quieter than a naturally aspirated engine for the

same power.

Cost and complexity

Run at high speeds – difficult to stop suddenly

Detonation - Extreme temperatures - summer

Turbo lag which is a serious problem in Turbocharger

Turbo lag - is the time required to change power output in

response to a throttle change

Exhaust back pressure on engines

Installing a turbocharger requires extensive modification of the

exhaust system

Air flow rate is proportional to engine load and speed

, noticed as a hesitation or slowed throttle response when

accelerating from idle as compared to a naturally aspirated

engine. This is due to the time needed for the exhaust system

and turbocharger to generate the required boost. Inertia,

friction, and compressor load are the primary contributors to

turbo lag. Superchargers do not suffer this problem, because

the turbine is eliminated due to the compressor being directly

powered by the engine.

Turbo-charging is an acceptable method of increasing its performance of an engine if carried out within manufacturers’ specifications.

Utilizing the waste exhaust energy

More power output

Lower engine operating temperatures result which can be beneficial.

Since the engine lubricating oil is subjected to high temperatures as it passes through the turbocharger the correct oil must be used as specified for turbocharged engines.

Advantages of Superchargers Over a Turbocharger: Supercharger do not suffer lag which is a serious problem in Turbocharger . Modification of the exhaust system:-, but superchargers can be bolted to the top or side of the engine , that makes them cheaper to install and easier to service and maintain. Shutdown procedure:-No special shutdown procedure is required with superchargers as they are not lubricated by engine oil . They can be shut down normally. Turbochargers must idle for about 30 seconds or so prior to shutdown so the lubricating oil has a chance to cool down.

Disadvantages of Superchargers: It derives power from the engine itself: Crankshaft drives superchargers so they steal some of the engine's horsepower. A supercharger can consume as much as 20 percent of an engine's total power output An added strain on the engine: Supercharging puts an added strain on the engine, which needs to be strong to handle the extra boost and bigger explosions Since some of the superchargers are larger in size the efficiency of the engine decreases as it is the additional component bolted on to it. Detonation is serious problem