TURBO CHARGER.docx

SEMINAR REPORT : TURBO CHARGER

Seminar Report 2011-2012

Turbocharger

KALAMASSERY Dept. of mechanical engineering Certificate This is to certify that the seminar report entitled TURBOCHARGER was presented by ARUNLAL S with Reg.No:  of final year Mechanical Engineering of Technical Education Department during the Academic year 2011-2012.

Seminar guide section

Head

of

2 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

Internal Examiner Examiner

External

ACKNOWLEDGEMENT Primarily I devote my gratitude towards the Almighty God for his grace and blessing. I wish to express my sincere gratitude to Head of Section of Mechanical Branch Mr. N RADAKRISHNAN PILLAI, for his expert guidance and valuable suggestions. It is my duty to convey my heartfelt thanks to my respected sir Mr. D PRAKASHAN for his sustained support and guidance on the right lines towards the successful completion and presentation of seminar. Finally, I thank all my colleagues for the cooperation and tremendous support they have given during my seminar.

ARUNLAL S 3 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

CONTENTS  ABSTRACT…………………………………………………… ………………....5  INTRODUCTION……………………………………………… …….………..6  HISTORY………………………………………………………… …….………..7  TURBO V/S SUPERCHARGING………………………………. ………...8  OPERATING PRINCIPLE……………………………………….. …….……9  WORKING……………………………………………………… ……………..11  COMPONENTS………………………………………………… …............13  COMPRESSOR………………………………………………… …………….14  TURBINE………………………………………………………… …………….15  CENTRE HOUSING ROTATINGASSEMBLY (CHRA) ………….…16  CLASSIFICATION SMALL V/S LARGE TURBOCHARGER........17  VARIABLE GEOMETRY……………………………………………………. 17 4 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

 ADVANTAGES………………………………………………… ………………18  BOOST………………………………………………………… …………………19  POWER AT HIGH ALTITUDES…………………………………………..21  HIGHER CARNOTT EFFICIENCY………………………………………...22  DISADVANTAGES……………………………………………… …………….22  TURBOLAG…………………………………………………… …………………22  BOOST THRESHOLD…………………………………………………… ……23  APPLICATIONS………………………………………………… ………………24  AIRCRAFT TURBOCHARGERS…………………………………………… 26  CONCLUSION………………………………………………… ……………….27  REFERENCES………………………………………………… …………………28

ABSTRACT 5 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

TURBOCHARGER A turbocharger or turbo is a centrifugal compressor powered by a turbine which is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the pressure of air entered with internal combustion engines such as four stroke g the engine. This results in greater performance in its power &efficiency. They are popularly use engines working on Otto & diesel cycles. The turbocharger was invented by Swiss engineer alfredbuchi in 1905. The engine is said to have 100% volumetric efficiency if the density of the intake air above the piston is equal to atmospheric. The main objective of a turbocharger is to improve an engine's volumetric efficiency by increasing the intake density. The compressor draws in ambient air and compresses it before it enters into the intake of manifold at increasing pressure. This results in greater mass of air entering the cylinder thus increasing power and efficiency. The impeller and turbine are the two main components of a turbo charger


DEPT OF


Turbocharger

INTRODUCTION A turbocharger or turbo is a centrifugal compressor powered by a turbine which is driven by an engines exhaust gases. Its benefit lies with the compressor increasing the pressure of air entering the engine thus resulting in greater performance. They are popularly used with internal combustion engines. Turbochargers have also been found useful compounding external combustion engines such as automotive fuel cells. It mainly consists of a turbine, compressor, centre housing rotating assembly and other optional features for its better control and efficient working. They provide greater boost and power at high altitudes. It is one of the greater advantages which make the turbocharger more popular. But boost threshold and turbolag must be controlled efficiently for its effective working.


DEPT OF


Turbocharger

HISTORY In 1896 Rudolph Diesel tried to increase power of the engine by pre-compressing intake air. But turbocharger was firstly invented by Swiss engineer Alfred Buchi. His patent for a turbocharger was applied for use in 1905.Diesel ships and locomotives with turbochargers began appearing in the 1920’s. During the First World War French engineer AugusteRateau fitted turbochargers to Renault engines powering various French fighters with some success. Turbochargers were first used in production aircraft engines in 1920’s.Aircrafts such as B-17, P-47 all used turbochargers to increase high altitude engine power. Turbocharger’s first commercial diesel truck application came in 1938 by “Swiss Machine Works Sauer”. First production application of turbocharger wasin passenger cars. It was in 1962.


DEPT OF


Turbocharger

TURBO V/S SUPERCHARGING In contrast to turbochargers, superchargers are not powered by a turbine but are connected directly to an engine .Belts ,chains, direct shaft, coupled shaft, gears and electric motors are probably only a few of the many ways this is performed. Successful superchargers were developed and used during the late 1800’s. A supercharger inevitably requires some energy to be bled from the engine to drive the supercharger. For instance, the supercharger uses up about 150 hp.For that 110 hp engine generates an additional 400 hp and delivers 1,000 hp when it would deliver 750hpa net gain of 250 hp.This is where the principal disadvantage of a supercharger becomes apparent; the internal hardware of the engine must withstand generating 1150hp. In comparison, a turbocharger will also use 150hp to drive the compressor. It has the ability to be more efficient by utilizing the wasted energy extracted from exhaust gas and converting it into useful power to compress the intake air. It actually converts the heat of the exhaust into 150hp used to drive the compressor. In contrast to supercharging principal disadvantages of turbo 9 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

charging are the back pressuring of the engine and the inefficiencies of the turbine versus direct drive.

OPERATING PRINCIPLE The power generated by the I.C engine is directly related to the compression force exerted on the air fuel mixture. By pressurizing the intake mixture before entering the cylinder, more fuel and air molecules can be packed into combustion chamber. Keep in mind that any time the amount of air/fuel mix that enters the cylinder is increased there is a substantial increase in power. The process of artificially increasing the amount of airflow into the engine is known as turbo charging. The mechanics of a turbocharger are closely related to the mechanics of a jet engine. A turbocharger harnesses the wasted energy of exhaust gases exiting the engine to spin a turbine that compresses the intake air charge.


DEPT OF

Operating Principle


Turbocharger

All naturally aspirated Otto and Diesel cycle engine rely on the downward stroke of a piston to create a low pressure area above the piston in order to draw air through the intake system. With the rare exception of tuned induction systems, most engines cannot inhale their full displacement of atmospheric density air. The measure of this loss or inefficiency in four stroke engines is called volumetric efficiency. If the density of the intake air above piston is equal to atmospheric, then the engine would 100% volumetric efficiency. Unfortunately, most engines fail to achieve this level of performance. The objective of a turbocharger, just as that of a supercharger, is to improve an engine’s volumetric efficiency by increasing the intake density. The compressor draws in ambient air and compresses it before it enters into the intake manifold at increased pressure. This results in a greater mass of air entering the cylinders on each intake stroke. The power needed to spin the 11 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

centrifugal compressor is derived from the high pressure and temperature of the engine’s exhaust gases. The turbine converts the engine exhaust’s potential pressure energy and kinetic velocity energy into rotational power, which is in turn used to drive the compressor.

WORKING The turbocharger is located to one side of the engine, usually to the exhaust manifold. An exhaust pipe runs between the engine exhaust manifold and the turbine housing to carry the exhaust flow to the turbine wheel. Another pipe connects the compressor housing intake to 12 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

an injector throttle body or a carburetor. The typical boost provided by a turbocharger is 4.2 to 5.6N/cm2.


DEPT OF


Turbocharger

Exhaust gases are directed into the turbocharger through the square inlet in the exhaust housing of the turbo .The exhaust flows through the exhaust housing spinning the exhaust turbine. After going through the exhaust housing, the gases flow out through the exhaust housing outlet. The turbine is connected to the compressor wheel on the intake side of the turbo through the center bearing housing. The center housing will have ports for oil to flow in to and out of to lubricate and cool the shaft, and it may or may not have ports for water to go in to and out of. Fresh air is brought into the turbocharger through the air inlet. The air is compressed by the compressor and the now pressurized air flows out through the compressor housing. Exhaust gases leave the engine via a turbo manifold; this replaces the stock exhaust manifold or header. The waste gate is used to control boost levels by allowing exhaust gasses to bypass the turbo, thereby decreasing the volume of exhaust available to spin the turbo’s turbine. After moving through the turbo, exhaust gasses exit the turbo through a down pipe which connects to the rest of the exhaust system. Fresh air, after being compressed by the turbo, passes through some intake piping and into an intercooler. An intercooler works exactly like a radiator except pressurized air passes through it instead of water. The intercooler is mounted on the front of the car so air flows through it as the car moves down the road. This cools the pressurized intake air charge. This is necessary because when air is pressurized it heats up. 14 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

The blow off valve vents pressurized air when the throttle plate is closed. This prevents a pressure surge from building up in the system and possibly damaging the compressor wheel and the turbo's bearings. The typical boost provided by a turbocharger is 4.2 to 5.6N/cm2.Since normal atmospheric pressure 10N/cm2 at sea level; you can see that you are getting 50% more air into the engine. Therefore, you would

expect to get 50% more power. It’s not so perfect, so you might get a 30-40% improvement instead.

COMPONENTS The turbocharger has three main components. First a turbine, which is almost always a radial inflow turbine. Second a compressor, which is almost a centrifugal compressor. These first two components are 15 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

the primary flow path components. Third, the center housing/hub rotating assembly (CHRA). Then, depending upon the exact installation and application, numerous other parts, features and controls may be required, such as  Engine  Turbo manifold  Westgate  Turbocharger  Anti-Surge valve  Boost controller

Components of a turbo charger

COMPRESSOR The compressor mainly consists of an impeller and spiral casing. It is usually located between air filter and intake manifold. The rotation of the impeller creates suction. This draws in air in at the center. The 16 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

impeller flings radially outwards and compresses the air. The outlet pressure is greater than inlet. The flow range of a turbocharger compressor can also be increased by allowing air to bleed from a ring of holes or a circular groove around the compressor at a point slightly downstream of the compressor inlet (but far nearer to the inlet than to the outlet). For all practical situations, the act of compressing air increases the air's temperature along with pressure. This temperature increase can cause a number of problems when not expected or when installing a turbocharger on an engine not designed for forced induction. Excessive charge air temperature can lead to detonation, which is extremely destructive to engines. The size of the compressor and impeller housings determines what A/R ratios are available and what trim compressor and turbine wheels will fit. The housings are expressed by codes that are proprietary to each turbocharger manufacturer and to each product line.

The housings fitted around the compressor impeller direct the gas flow through the wheels as they spin. The size and shape can dictate Compressor Wheel some performance characteristics of the overall turbocharger. The impeller wheel sizes also dictate 17 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

Compressor assembly

the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. Generally, the larger the compressor wheel, the larger the flow capacity

TURBINE


DEPT OF


Turbocharger

The turbine is enclosed inside a spiral casing. It is connected to exhaust manifold. The exhaust manifold directs the exhaust to turbine. The turbine and compressor are mounted on the same shaft. It converts the heat energy into kinetic energy. Thus it rotates and gives drive to the shaft from there to the compressor. The

Turbine assembly

housings fitted around the turbine collect and direct the gas flow through the wheels as they spin. The size and shape can dictate some performance characteristics of the overall turbocharger. The turbine wheel sizes also dictate the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. Generally, the larger the turbine wheel the larger the flow capacity.

CENTREHOUSINGROTATINGASSEMBLY (CHRA) It is the centre hub which houses the shaft connecting both the impeller and compressor. Usually a common shaft is used. It is lubricated by high pressurized engine oil which allows the turbine and impeller to rotate 19 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

at high speed at minimal friction. There are also housings which are water cooled. It also must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction and capable of withstanding high temperatures. For instance, in automotive applications the CHRA typically uses a thrust bearing or ball bearing lubricated by a constant supply of pressurized engine oil. Fluid bearings are preferred for high temperature purpose. The CHRA may also be considered "water cooled" by having an entry and exit point for engine coolant to be cycled. Water cooled models allow engine coolant to be used to keep the lubricating oil cooler, avoiding possible oil coking (the destructive distillation of the engine oil) from the extreme heat found in the turbine. The development of air-foil bearings has removed this risk. Adaptation of turbochargers on naturally aspirated internal combustion engines, either on petrol or diesel, can yield power increases of 30% to 40%.

CHRA assembly

CLASSIFICATION SMALL V/S LARGE TURBOCHARGER 20 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

To reduce the inertia of the turbine and the compressor is to make the turbocharger smaller. A small turbocharger will provide the boost more quickly and at lower engine speeds, but may not be able to provide much boost at higher engine speeds when a large volume of air is going into the engine. It is also in danger in spinning too quickly at higher engine speeds, when lots of exhaust is passing through the turbine. A large turbocharger can provide lost of boost at engine speeds, but may have but may have bad turbo lag because of how long it takes to accelerate its heavier turbine and compressor.

VARIABLE GEOMETRY


DEPT OF


Turbocharger

Instead of using two turbochargers in different sizes, some engines use a single turbocharger, called variable geometry or variable-nozzle turbos, these turbo’s use a

Variable geometry Turbocharger

set of vanes in the exhaust housing to maintain a constant gas velocity across the turbine, the same kind of control as used on power plant turbines. Such turbochargers have minimal lag like a small conventional turbocharger and can achieve full boost as low as 1,500 engine rpm, yet remain efficient as a large conventional turbocharger at higher engine speeds. In many setups these turbo’s do not use a waste gate. The vanes are controlled by a membrane identical to the one on a waste gate, but the mechanism operates the variable vane system instead. These variable turbochargers are commonly used in diesel engines.

ADVANTAGES A turbocharger harnesses the wasted energy of exhaust gases exiting the engine. Thus the velocity and 22 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

heat energy carried by the exhaust gas is partially utilized by turbocharger. Large amount of heat energy is lost in the form of exhaust gases. Thus it is greater benefit for the engine. The exhaust gas is used to spin the turbine which is connected to the compressor wheel. The compressor wheel also rotates and intakes air and compress it and feeds back it into the engine. This results in greater mass of air entering the cylinders on each stroke. Any time the amount of air/fuel mix that enters the cylinder is increased; there is a substantial increase in power. The typical boost provided by a turbocharger is from 4.2 to 5.6 N/cm2. Since normal atmospheric 10N/cm2 at sea level, we can see that we are getting 50% more air into the engine. Therefore we should except to get 50% power, but might get a 30-40% improvement instead. A turbocharger may also be used to increase fuel efficiency with-out attempt to increase power. It does this by increasing waste energy in the exhaust and feeding it back into the engine intake. By using this to increase the mass of air it becomes easier to ensure that all fuel is burnt before vented at the start of the exhaust stage. This increased temperature from the higher temperature gives higher Carnot efficiency. One of the most important advantages is that they give power to the engine at high altitudes. In such cases the duty of turbocharger is to maintain manifold pressure as altitude increases. Since atmospheric pressure reduces as the aircraft climbs, power drop will occur. The 23 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

turbochargers operate and maintain manifold pressure. With such systems, modern high performance piston engine aircraft can cruise at altitudes above 20,000 ft where low air density results in lower drag and higher true airspeeds.

BOOST In the automotive engines, boost refers to the intake manifold pressure that exceeds normal atmospheric pressure. This is representative of the extra air pressure that is achieved over what would be achieved without the forced induction. The level of boost may be shown on a pressure gauge, usually in bar, psi or possibly kPa. Anything above normal atmospheric level is considered to be boost. In all turbocharger applications, boost pressure is limited to keep the entire engine system, including the turbo, inside its thermal and mechanical design operating range. Over boosting an engine frequently causes damage to the engine in a variety of ways including pre-ignition, overheating and over-stressing the engines internal hardware. For example, to avoid Engine knocking (aka preignition or detonation) and the related physical damage to the host engine, the intake manifold pressure must not get too high, thus the pressure at the intake manifold of the engine must be controlled by some means. Opening the waste-gate allows the energy for the turbine to bypass it 24 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

and pass directly to the exhaust pipe. The turbocharger is forced to slow as the turbine is starved of its source of power, the exhaust gas. Slowing the turbine/compressor rotor begets less compressor pressure. In modern installations, an actuator controlled manually (frequently seen in aircraft) or an actuator controlled by the car's Engine Control Unit, forces the waste gate to open or close as necessary. Again, the reduction in turbine speed results in the compressor slowing, and in less air pressure at the intake manifold. The typical boost provided by a turbocharger is 4.2 to 5.6N/cm2.Since normal atmospheric pressure 10N/cm2 at sea level; you can see that you are getting 50% more air into the engine. Therefore, you would expect to get 50% more power. It’s not so perfect, so you might get a 30-40% improvement instead. Older cars with carburetors automatically increase the fuel rate to match the increased air flow going into the cylinders. Modern cars with the fuel injection will also do this to a point. The fuel-injection system release on oxygen sensors in the exhaust to determine if the air-to-fuel ratio is correct, so this system will automatically increase the fuel flow if a turbo is added. If a turbocharger with too much boost is added to a fuel-injector car, the system may not provide enough fueleither the software programmed into the controller couldn’t allow it, or the pump and the injectors are not capable of supplying it. In this case, other modifications 25 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

will have to be made to get the maximum benefit from the turbocharger.

POWER AT HIGH ALTITUDES In most aircraft engines the main benefit of turbochargers is to maintain manifold pressure as altitude increases. Since atmospheric pressure reduces as the aircraft climbs, power drops as a function of altitude in normally aspirated engines. Aircraft manifold pressure in western built aircraft is expressed in inches of mercury (Hg) where 29.92 inches is the standard sea level pressure. In high performance aircraft, turbo chargers will provide takeoff manifold pressures in the 30 - 42 inches Hg range (1 to 1.4 bar). This varies according to aircraft and engine types. In contrast, the takeoff manifold pressure of a normally aspirated engine is about 27 inches of Hg, even at sea level, due to losses in the induction system (air filter, ducting, throttle body, etc.). As the turbocharged aircraft climbs, however, the pilot (or automated system) can close the waste gate forcing more exhaust gas through the turbocharger turbine thereby maintaining manifold pressure during the climb, at least until the critical pressure altitude is reached (when the 26 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

waste gate is fully closed) after which manifold pressure will fall. With such systems, modern high performance piston engine aircraft can cruise at altitudes above 20,000 feet where low air density results in lower drag and higher true airspeeds. Most importantly, this allows flying "above the weather". In manually controlled waste gate systems the pilot must take care not to over boost the engine which will cause pre-ignition leading to engine damage. Further, since most aircraft turbocharger systems do not include an intercooler, the engine is typically operated on the rich side of peak exhaust temperature in order to avoid overheating the turbocharger. In non high performance turbo charged aircraft, the turbocharger is solely used to maintain sea-level manifold pressure during the climb (this is called turbo-normalizing).

HIGHER CARNOTT EFFICIENCY Turbochargers are not only used for increasing the power but also for increasing the Carnot efficiency. It recovers the waste energy in exhaust and feeds back it to the engine cylinder. Thus the mass of air entering the cylinder increases which ensures complete combustion of fuel. This increased temperature from high pressure gives higher Carnot efficiency.

DISADVANTAGES 27 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

In contrast to supercharging, the principal disadvantages of turbo charging are the back pressuring of the engine and the inefficiencies of the turbine versus direct drive. The disadvantages of turbine are defined below.

TURBOLAG Turbo lag is most problematic when rapid changes in engine performance are required. Turbo lag is the time required to change speed and function effectively in response to a throttle change. For example, this is noticed as a hesitation in throttle response when accelerating from idle as compared to a naturally aspirated engine. Turbocharger doesn’t provide an immediate power boost when you step over the gas. It takes a second for the turbine to get up to speed before the boost is produced. This results in a feeling of a lag when you step on the gas and then the car lungs ahead when the turbo gets moving. Throttle lag may be noticeable under any driving condition, yet becomes a significant issue under acceleration. This is symptomatic of the time needed for the exhaust system working in concert with the turbine to generate enough extra power to accelerate rapidly. A combination of inertia, friction and compressor load is the primary contributors to turbo lag. By eliminating the


DEPT OF


Turbocharger

turbine, the directly-driven compressor in a supercharger does not suffer from this problem. Lag can be reduced in a number of ways: 1. By lowering the rotational inertia of the turbocharger; for example by using lighter, lower radius parts. Ceramic turbines and billet compressor wheel can be used. 2. By changing the aspect ratio of the turbine. 3. By increasing the upper-deck air pressure (compressor discharge) and improving the waste gate response. 4. By reducing bearing frictional losses; by using a foil bearing rather than a conventional oil bearing. 5. Variable-nozzle turbochargers greatly reduce lag. 6. By decreasing the volume of the upper-deck piping. 7. By using multiple turbos sequentially or in parallel.

BOOST THRESHOLD Lag is not to be confused with the boost threshold. The boost threshold of a turbo system describes the lower bound of the region within which the compressor will operate. Below a certain rate of flow at any given pressure multiplier, a given compressor will not produce significant boost. This has the effect of limiting boost at 29 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

particular rpm regardless of exhaust gas pressure. Turbochargers start producing boost only above a certain exhaust mass flow rate. The boost threshold is determined by the engine displacement, engine rpm, throttle opening, and the size of the turbo. Without adequate exhaust gas flow to spin the turbine blades, the turbo cannot produce the necessary force needed to compress the air going into the engine. The point at full throttle in which the mass flow in the exhaust is strong enough to force air into the engine is known as the boost threshold rpm. Engineers have, in some cases, been able to reduce the boost threshold rpm to idle speed to allow for instant response. Newer turbocharger and engine developments have caused boost thresholds to steadily decline. Electrical boosting ("E-boosting") is a new technology under development; it uses a high speed electrical motor to drive the turbocharger to speed before exhaust gases are available. An alternative to e-boosting is to completely separate the turbine and compressor into a turbinegenerator and electric-compressor as in the hybrid turbocharger. This allows the compressor speed to become independent to that of the turbine. A similar system utilizing a hydraulic drive system and over speed clutch arrangement was fitted in 1981 to accelerate the turbocharger of the MV Canadian.

APPLICATIONS 30 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

Today, turbochargers are most commonly used on gasoline engines in high-performance automobiles and diesel engines in transportation and other industrial equipment. Small cars in particular benefit from this technology, as there is often little room to fit a large engine. The turbocharger's small size and low weight have production and marketing advantage to vehicle manufacturers. By providing naturally-aspirated and turbocharged versions of one engine, the manufacturer can offer two different power outputs with only a fraction of the development and production costs of designing and installing a different engine. Usually increased piston cooling is provided by spraying more lubrication oil on the bottom of the piston. The compact nature of a turbocharger means that bodywork and engine compartment layout changes to accommodate the more powerful engine are not needed. The use of parts common to the two versions of the same engine reduces production and servicing costs. Recently, several manufacturers have returned to the turbocharger in an attempt to improve the tradeoff between performance and fuel economy by using a smaller turbocharged engine in place of a larger normally-aspirated engine. The first production turbocharged automobile engines came from General Motors in 1962. The Y-body Oldsmobile Cutlass Jet fire was fitted with a Garrett Air search turbocharger and the Chevrolet Corvair Monza Spyder with a TRW turbocharger. Their applications are 31 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

 Aircraft turbochargers  Land based turbochargers  Marine based turbochargers  Locomotive turbochargers  Motorsport and performance turbochargers  Auxiliary power generation

AIRCRAFT TURBOCHARGERS A natural use of the turbocharger is with aircraft engines. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off. At

5,486 m (18,000 ft) the air is at half the pressure of sea level, and the airframe only experiences half the aerodynamic drag. However, since the charge in the cylinders is being pushed in by this air pressure, it means that the engine will normally produce only half-power at full throttle at this altitude. Pilots would like to take advantage of the low drag at high altitudes in order to go faster, but a naturally aspirated engine will not produce enough power at the same altitude to do so. A turbocharger remedies this problem by compressing the air back to sea-level pressures; or even much higher; in order to produce rated power at high altitude. Since the 32 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

size of the turbocharger is chosen to produce a given amount of pressure at high altitude, the turbocharger is over-sized for low altitude. The speed of the turbocharger is controlled by a wastegate. Early systems used a fixed waste gate, resulting in a turbocharger that functioned much like a supercharger. Later systems utilized an adjustable wastegate, controlled either manually by the pilot or by an automatic hydraulic or electric system. When the aircraft is at low altitude the waste gate is usually fully open, venting all the exhaust gases overboard. As the aircraft climbs and the air density drops, the wastegate must continually close in small increments to maintain full power. The altitude at which the wastegate is fully closed and the engine is still producing full rated power is known as the critical altitude. When the aircraft climbs above the critical altitude, engine power output will decrease as altitude increases just as it would in a naturally-aspirated engine.

CONCLUSION Turbocharger can be used for utilizing the waste energy from the engine. Thus it gives a greater performance for a naturally aspirated engine. It is now being mostly used in all type of cars for harnessing the waste energy. As the Petroleum products are being scarce it is a vice technique to use this turbocharger so that 33 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

maximum amount of energy can be utilized with less wastage. It also has wide applications in various automotive fields. The typical boost provided by a turbocharger is from 4.2 to 5.6 N/cm 2. That is we are getting 50% more air into the engine. Therefore we should except to get 50% power, but might get a 30-40% improvement instead. That’s a great boost for the vehicle.

REFERENCES 1. Automobile engineering-“R.B Gupta” H & C publications (2001) 34 G P T C KALAMASSERY MECHANICAL ENGG.

DEPT OF


Turbocharger

2. Automobile engineering-''R.K Rajput'' Laxmipublications (2007) 3. Web pages 3.1. http://en.wikipedia.org/wiki/turbocharger 3.2. http://en.turboguide.org/turbocharger 3.3. http://www.g2ic.com/turbocharger


DEPT OF

TURBO CHARGER.docx

Recommend Documents