SUPERCHARGING & TURBOCHARGING

SHREY SHIROMANI (140050119110)

A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine. This gives each intake cycle of the engine more oxygen, letting it burn more fuel and do more work, thus increasing power.

Power for the supercharger can be provided mechanically by means of a belt, gear, shaft, or chain connected to the engine's crankshaft.

SUPERCHARGERS

Air inlet

OBJECTIVES OF SUPERCHARGING1. To overcome the effect of high altitude, as in the case of aircrafts and stationary engine ties in mountains.

2. To reduce the weight of an engine per kW or power developed, as in the case of racing cars.

3. To reduce the size of the engine to fit into a limited space, as in the case of locomotives or marine engines.

4. To increase the power output of an existing engine to meet greater power demands.

1. Power output: Supercharging produces more power because the supercharger supplies air at a pressure and density higher than atmospheric with has the effect of increasing volumetric efficiency.

2. Mechanical efficiency : The mechanical efficiency of a supercharged engine is higher than that of one not supercharged.

3. Fuel consumption : It provides better mixing of fuel and air which results in a specific reduction of fuel consumption and the thermal efficiency increases.

4. Scavenging : In supercharged engine , the pressure of charge is higher than the exhaust pressure & hence scavenging is possible

EFFECTS OF SUPERCHARGING

Based on the use of compressor Centrifugal type Roots type Vane type

TYPES OF SUPERCHARGER

The roots type supercharger is by far the oldest, dating back to before the 20th century. However, it has been continuously updated since it was first invented and used, and has managed to hold its own in modern times in several areas.

Originally, roots type superchargers push extra oxygen into engines by using meshed-lobe rotors with two lobes. These rotors rotate in opposite directions, trapping air in pockets and forcing it from the inlet to the compressor chamber, where it is compressed and moved into the engine. Modern designs use the same basic principal, but usually use rotors with three or even four lobes, as well as other upgrades that can improve efficiency in dramatic ways.

ROOTS BLOWER SUPERCHARGER

ROOTS BLOWER SUPERCHARGER

Centrifugal superchargers are similar to many pumps or fans. They pull air through an intake using an impeller, which collects air and forces it out into a progressively smaller area, compressing it and leading to an engine, where it is put to work.

Centrifugal superchargers use their special features to their advantage, but not without drawbacks. In general, they are excellent at moving a large volume of air. As a result of this, they are among the most efficient and effective superchargers. Centrifugal superchargers have comparatively few moving parts. As a result of this, they are quite reliable, requiring little maintenance. They also generate much less heat than their more complicated equivalents. Unfortunately, they put a limited amount of pressure on this air, unlike the other kinds of superchargers. They also perform less effectively at lower RPM.

CENTRIFUGAL COMPRESSOR SUPERCHARGER

The screw type supercharger works in a similar way to the roots type supercharger. Screw type superchargers work by using two counter rotating screws, rather than rotors. While this seems similar enough to a roots type supercharger, it actually offers very different advantages and disadvantages.

Screw type superchargers are very good at moving air — they lose very little of it due to their design. Additionally, they can compress air as they move it using their screws. However, these advantages are not without cost. Screw type superchargers are significantly less powerful before reaching high RPM — and if used on an engine that never reaches high RPM, they will not ever achieve their potential.

SCREW COMPRESSOR SUPERCHARGER

1. Compressor driven by engine

2. Compressor driven by turbine

3. Compressor driven by external source of power

4. Compressor driven by engine shaft & free turbine

5. Direct coupling between engine, compressor & turbine

METHODS OR ARRANGMENTS OF SUPERCHARGING

Increased horsepower: adding a supercharger to any engine is a quick solution to boosting power.

No lag: the supercharger’s biggest advantage over a turbocharger is that it does not have any lag. Power delivery is immediate because the supercharger is driven by the engine’s crankshaft.

Low RPM boost: good power at low RPM in comparison with turbochargers.

Price: cost effective way of increasing horsepower.

ADVANTAGES OF SUPERCHARGING

Less efficient: the biggest disadvantage of superchargers is that they suck engine power simply to produce engine power. They’re run off an engine belt connected to the crankshaft, so you’re essentially powering an air pump with another air pump. Because of this, superchargers are significantly less efficient than turbochargers.

Increases knocking tendency of engine. Increases the strain on engine & running gear. Mechanical & gas loading increases with an increase in

supercharging. Reliability: with all forced induction systems (including

turbochargers), the engine internals will be exposed to higher pressures and temperatures, which will of course affect the longevity of the engine. It’s best to build the engine from the bottom up to handle these pressures, rather than relying on stock internals.

DISADVANTAGES OF SUPERCHARGING

A turbocharger, is a turbine-driven forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra air into the combustion chamber. This improvement over a naturally aspirated engine's power output is due to the fact that the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure (and for that matter, ram air intakes) alone.

The key difference between a turbocharger and a conventional supercharger is that a supercharger is mechanically driven by the engine, often through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive. Twin charger refers to an engine with both a supercharger and a turbocharger.

TURBOCHARGING

1. Constant pressure turbocharging

The various cylinders discharge their exhaust into a common manifold at pressures higher than atmospheric pressure.

These exhaust gases undergo expansion in exhaust valves, to an approximately constant pressure in the common manifold and then enter the turbine.

This allows the conversion of blow-down energy (internal energy) to work in the turbine. Higher the pressure ratio of turbine, higher is the recovery of blow-down energy.

METHODS OF TURBOCHARGING

2. Pulse Turbocharging: In this significant part of blow down energy is converted into

exhaust pulses as soon as exhaust valve opens. These pulses enter the turbine through narrow exhaust pipes

where this energy is utilized and so a large part of energy is recovered.

Separate exhaust pipes are used so that the exhaust process of various cylinders do not interfere with each other.

3. Pulse Convertor Turbocharging: This method provides advantages of both constant pressure

and pulse turbocharging simultaneously. The arrangement involves connecting the different branches

of exhaust manifolds together in a specially designed venturi junction called pulse converter before the turbine.

Significant increase in horsepower.

Power vs. size: allows for smaller engine displacements to produce much more power relative to their size.

Better fuel economy: smaller engines use less fuel to idle, and have less rotational and reciprocating mass, which improves fuel economy.

Higher efficiency: turbochargers run off energy that is typically lost in naturally-aspirated and supercharged engines (exhaust gases), thus the recovery of this energy improves the overall efficiency of the engine.

ADVANTAGES OF TURBOCHARGING

Turbo lag: turbochargers, especially large turbochargers, take time to spool up and provide useful boost.

Boost threshold: for traditional turbochargers, they are often sized for a certain RPM range where the exhaust gas flow is adequate to provide additional boost for the engine. They typically do not operate across as wide an RPM range as superchargers.

Power surge: in some turbocharger applications, especially with larger turbos, reaching the boost threshold can provide an almost instantaneous surge in power, which could compromise tire traction or cause some instability of the car.

Oil requirement: turbochargers get very hot and often tap into the engine’s oil supply. This calls for additional plumbing, and is more demanding on the engine oil. Superchargers typically do not require engine oil lubrication.

DISADVANTAGES OF TURBOCHARGING