turbocharger - wikipedia, the free encyclopedia

7/13/12 Turbocharger - Wikipedia, the free encyclopedia

1/14en.wikipedia.org/wiki/Turbocharger

Cut-away view of an air foil bearing-supported

turbocharger made by Mohawk Innovative

Technology

TurbochargerFrom Wikipedia, the free encyclopedia

A turbocharger, or turbo (colloquialism), from the Greek"τύρβη" (mixing/spinning) is a forced induction device usedto allow more power to be produced for an engine of a

given size.[1][2] The key difference between a turbochargerand a conventional supercharger is that the latter ismechanically driven from the engine often from a beltconnected to the crankshaft, whereas a turbocharger isdriven by the engine's exhaust gases.

A turbocharged engine can be more powerful and efficientthan a naturally aspirated engine because the turbine forcesmore intake air, proportionately more fuel, into thecombustion chamber than if atmospheric pressure alone isused.

Turbos are commonly used on truck, car, train andconstruction equipment engines. Turbos are popularly usedwith Otto cycle and Diesel cycle internal combustion

engines. They have also been found useful in automotive fuel cells.[3]

Twincharger refers to an engine which has both a supercharger and a turbocharger.

Contents

1 History2 Turbocharging versus supercharging3 Operating principle

3.1 Pressure increase / boost3.2 Turbo lag

3.3 Boost threshold

4 Key components and installation

4.1 Turbine

4.2 Compressor

4.3 Intercooling

4.4 Water injection

4.5 Fuel-air mixture ratio

4.6 Center housing/hub rotating assembly

4.7 Wastegate

4.8 Anti-surge/dump/blow off valves4.9 Factors affecting lifespan

5 Applications

5.1 Petrol powered cars



5.2 Diesel powered cars

5.3 Motorcycles

5.4 Trucks

5.5 Aircraft

5.6 Marine and land-based diesel turbochargers

6 Business7 See also

8 References

9 External links

History

Forced induction dates from the late 19th century, when Gottlieb Daimler patented the technique of using a gear-

driven pump to force air into an internal combustion engine in 1885.[4] The turbocharger was invented by Swissengineer Alfred Büchi (1879-1959), the head of diesel engine research at Gebruder Sulzer engine manufacturing

company in Winterhur,[5] who received a patent in 1905 for using a compressor driven by exhaust gasses to force

air into a diesel engine to increase power output but it took another 20 years for the idea to come to fruition.[6][7]

During World War I French engineer Auguste Rateau fitted turbochargers to Renault engines powering various

French fighters with some success.[8] In 1918, General Electric engineer Sanford Alexander Moss attached a turboto a V12 Liberty aircraft engine. The engine was tested at Pikes Peak in Colorado at 14,000 ft (4,300 m) todemonstrate that it could eliminate the power loss usually experienced in internal combustion engines as a result of

reduced air pressure and density at high altitude.[8] General Electric called the system turbosupercharging.[9] At thetime, all forced induction devices were known as superchargers, however more recently the term "supercharger" is

usually applied to only mechanically-driven forced induction devices.[10]

Turbochargers were first used in production aircraft engines such as the Napier Lioness[11] in the 1920s, althoughthey were less common than engine-driven centrifugal superchargers. Ships and locomotives equipped withturbocharged Diesel engines began appearing in the 1920s. Turbochargers were also used in aviation, most widelyused by the United States, which led the world in the technology due to General Electric's early

start.[citation needed] During World War II, notable examples of US aircraft with turbochargers include the B-17Flying Fortress, B-24 Liberator, P-38 Lightning and P-47 Thunderbolt. The technology was also used inexperimental fittings by a number of other manufacturers, notably a variety of Focke-Wulf Fw 190 models, but the

need for advanced high-temperature metals in the turbine kept them out of widespread use.[citation needed]

Turbocharging versus supercharging

Main article: Supercharger

In contrast to turbochargers, superchargers are not powered by exhaust gases but driven by the engine

mechanically.[12] Belts, chains, shafts, and gears are common methods of powering a supercharger. A supercharger

places a mechanical load on the engine to drive.[13][14] For example, on the single-stage single-speed superchargedRolls-Royce Merlin engine, the supercharger uses up about 150 horsepower (110 kW). Yet the benefits outweighthe costs: For that 150 hp (110 kW), the engine generates an additional 400 horsepower, a net gain of 250 hp



(190 kW). This is where the principal disadvantage of a supercharger becomes apparent: the internal hardware ofthe engine must withstand the net power output of the engine plus the 150 horsepower to drive the supercharger.

In comparison, a turbocharger does not place a direct mechanical load on the engine.[12] It is more efficientbecause it uses kinetic energy of the exhaust gas to drive the compressor. In contrast to supercharging, the principal

disadvantages of turbocharging are back-pressure,[12] heat soak of the intake air and the inefficiencies of the turbineversus direct-drive.

A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses

of the other.[15] This technique is called twincharging.

Operating principle

In most piston engines, intake gases are "pulled" into the

engine by the downward stroke of the piston[16][17] (whichcreates a low-pressure area), similar to drawing liquid usinga syringe. The amount of air which is actually inhaled,compared with the theoretical amount if the engine couldmaintain atmospheric pressure, is called volumetric

efficiency.[18] The object of a turbocharger is to improve anengine's volumetric efficiency by increasing density of theintake gas (usually air).

The turbocharger's compressor draws in ambient air andcompresses it before it enters into the intake manifold at

increased pressure.[19] This results in a greater mass of airentering the cylinders on each intake stroke. The powerneeded to spin the centrifugal compressor is derived from

the kinetic energy of the engine's exhaust gases.[20]

A turbocharger may also be used to increase fuel efficiency without increasing power.[21] This is achieved byrecovering waste energy in the exhaust and feeding it back into the engine intake. By using this otherwise wastedenergy to increase the mass of air, it becomes easier to ensure that all fuel is burned before being vented at the startof the exhaust stage. The increased temperature from the higher pressure gives a higher Carnot efficiency.

The control of turbochargers is very complex and has changed dramatically over the 100-plus years of its use.Modern turbochargers can use wastegates, blow-off valves and variable geometry, as discussed in later sections.

The reduced density of intake air is often compounded by the loss of atmospheric density seen with elevatedaltitudes. Thus, a natural use of the turbocharger is with aircraft engines. As an aircraft climbs to higher altitudes, thepressure of the surrounding air quickly falls off. At 5,486 metres (17,999 ft), the air is at half the pressure of sea

level, which means that the engine will produce less than half-power at this altitude.[22]

Pressure increase / boost

In automotive applications, "boost" refers to the amount by which intake manifold pressure exceeds atmosphericpressure. 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.[22]

In aircraft engines, turbocharging is commonly used to maintain manifold pressure as altitude increases (i.e. tocompensate for lower-density air at higher altitudes). Since atmospheric pressure reduces as the aircraft climbs,power drops as a function of altitude in normally aspirated engines. Systems that use a turbocharger to maintain anengine's sea-level power output are called turbo-normalized systems. Generally, a turbo-normalized system will

attempt to maintain a manifold pressure of 29.5 inches of mercury (100 kPa).[22]

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 theengine in a variety of ways including pre-ignition, overheating, and over-stressing the engine's internal hardware.

For example, to avoid engine knocking (aka pre-ignition or detonation) and the related physical damage to theengine, the intake manifold pressure must not get too high, thus the pressure at the intake manifold of the enginemust be controlled by some means. Opening the wastegate allows the excess energy destined for the turbine tobypass it and pass directly to the exhaust pipe, thus reducing boost pressure. The wastegate can be eithercontrolled manually (frequently seen in aircraft) or by an actuator (in automotive applications, it is often controlledby the Engine Control Unit).

Turbo lag

Turbocharger applications can be categorised according to those which require changes in output power (such asautomotive) and those which do not (such as marine, aircraft, commercial automotive, industrial, locomotives).While important to varying degrees, turbo lag is most problematic when rapid changes in power output arerequired.

Turbo lag is the time required to change power output in response to a throttle change, noticed as a hesitation orslowed throttle response when accelerating from idle as compared to a naturally aspirated engine. This is due to thetime needed for the exhaust system and turbocharger to generate the required boost. Inertia, friction, andcompressor load are the primary contributors to turbo lag. Superchargers do not suffer this problem, because theturbine is eliminated due to the compressor being directly powered by the engine.

Lag can be reduced in a number of ways:

lowering the rotational inertia of the turbocharger; for example by using lighter, lower radius parts to allow

the spool-up to happen more quickly. Ceramic turbines are of benefit in this regard and or billet compressorwheel.

changing the aspect ratio of the turbine.

increasing the upper-deck air pressure (compressor discharge) and improving the wastegate response

reducing bearing frictional losses (such as by using a foil bearing rather than a conventional oil bearing)using variable-nozzle turbochargers (discussed below).

decreasing the volume of the upper-deck piping.

using multiple turbos sequentially or in parallel.

using an Antilag system.

Boost threshold

Lag is not to be confused with the boost threshold. The boost threshold of a turbo system describes the lower



On the left, the brass oil drain

connection. On the right are the

braided oil supply line and water

coolant line connections.

Compressor impeller side with the

cover removed.

Turbine side housing removed.

bound of the region within which the compressor will operate. Below a certain rate of flow, a compressor will notproduce significant boost. This has the effect of limiting boost at particular rpm regardless of exhaust gas pressure.Newer turbocharger and engine developments have caused boost thresholds to steadily decline.

Electrical boosting ("E-boosting") is a new technology under development; it uses an electric motor to bring the

turbo up to operating speed quicker than is possible using available exhaust gases.[23] An alternative to e-boostingis to completely separate the turbine and compressor into a turbine-generator and electric-compressor as in thehybrid turbocharger. This allows the compressor speed to become independent to that of the turbine. A similarsystem utilising a hydraulic drive system and overspeed clutch arrangement was fitted in 1981 to accelerate the

turbocharger of the MV Canadian Pioneer (Doxford 76J4CR engine).[citation needed]

Turbochargers start producing boost only when a certain amount of kinetic energy (i.e. momentum) is present in theexhaust gasses. Without adequate exhaust gas flow to spin the turbine blades, the turbo cannot produce thenecessary force needed to compress the air going into the engine. The boost threshold is determined by the enginedisplacement, engine rpm, throttle opening, and the size of the turbo. The operating speed (rpm) at which there isenough exhaust gas momentum to compress the air going into the engine is called the "boost threshold rpm".Reducing the "boost threshold rpm" can improve throttle response.

Key components and installation

The turbocharger has three main components:

1. the turbine, which is almost always a radial inflow turbine

2. the compressor, which is almost always a centrifugal compressor3. the center housing/hub rotating assembly

Many modern turbochargers include extra components (such aswastegates and variable vane systems).

Turbine

Kinetic energy of the exhaust gas is captured using the turbine. Theturbine housings direct the gas flow through the turbine as it spins at up to

250,000 rpm.[24][25] The size and shape can dictate some performancecharacteristics of the overall turbocharger. Often the same basicturbocharger assembly will be available from the manufacturer withmultiple housing choices for the turbine and sometimes the compressorcover as well. This allows the balance between performance, response,and efficiency to be tailored to the application.

Twin-scroll designs have two valve-operated exhaust gas inlets, a smallersharper angled one for quick response and a larger less angled one forpeak performance.

The turbine and impeller wheel sizes also dictate the amount of air orexhaust that can be flowed through the system, and the relative efficiencyat which they operate. In general, the larger the turbine wheel andcompressor wheel the larger the flow capacity. Measurements and shapes can vary, as well as curvature and



A wastegate installed next to the

turbocharger.

Garrett variable-geometry

turbocharger on DV6TED4 engine

number of blades on the wheels. Variable geometry turbochargers are further developments of these ideas.

Variable geometry turbine

Variable-geometry or variable-nozzle turbos use a set of vanes in theexhaust housing to maintain a constant gas velocity across the turbine (asused on power plant turbines) and are often used instead of using twoturbochargers in different sizes.

Variable geometry allows lag to be reduced while maintaining theefficiency of a larger turbo at higher engine speeds. In many setups, theseturbos do not use a wastegate. The vanes are controlled by a membraneidentical to the one on a wastegate, but the mechanism operates thevariable vane system instead. These variable turbochargers are commonly

used in diesel engines.[23]

Compressor

The compressor increases the mass of intake air entering the combustionchamber. The compressor is made up of an impeller, a diffuser and avolute housing.

Main article: Centrifugal compressor

The operating range of a compressor is described by the "compressormap".

Main article: Compressor map

Ported shroud The flow range of a turbocharger compressor can be increased by allowing air to bleed from a ringof holes or a circular groove around the compressor at a point slightly downstream of the compressor inlet (but farnearer to the inlet than to the outlet).

The ported shroud is a performance enhancement that allows the compressor to operate at significantly lowerflows. It achieves this by forcing a simulation of impeller stall to occur continuously. Allowing some air to escape atthis location inhibits the onset of surge and widens the operating range. While peak efficiencies may decrease, highefficiency may be achieved over a greater range of engine speeds. Increases in compressor efficiency result inslightly cooler (more dense) intake air, which improves power. This is a passive structure that is constantly open (incontrast to compressor exhaust blow off valves, which are electronically controlled). The ability of the compressorto provide high boost at low rpm may also be increased marginally (because near choke conditions the compressordraws air inward through the bleed path). Ported shrouds are used by turbocharger manufacturers such asHoneywell Turbo Technologies, Cummins Turbo Technologies, and GReddy.

Intercooling

When the pressure of the engine's intake air is increased, its temperature will also increase. In addition, heat soakfrom the hot exhaust gases spinning the turbine may also heat the intake air. The warmer the intake air the lessdense, and the less oxygen available for the combustion event, which reduces fuel efficiency. Not only doesexcessive intake-air temperature reduce efficiency, it also leads to engine knock, or detonation, which is destructive



Illustration of inter-cooler location.

to engines.

Turbocharger units often make use of an intercooler (also known as a charge air cooler), to cool down the intakeair. Intercoolers are often tested for leaks during routine servicing, particularly in trucks where a leaking intercoolercan result in a 20% reduction in fuel economy.

Water injection

An alternative to intercooling is injecting water into the intake air toreduce the temperature. This method has been used in automotive and

aircraft applications.[citation needed]

Fuel-air mixture ratio

Main article: Air-fuel ratio

In addition to the use of intercoolers, it is common practice to add extra fuel to the intake air (known as "running anengine rich") for the sole purpose of cooling. The amount of extra fuel varies, but typically reduces the air-fuel ratioto between 11 and 13, instead of the stoichiometric 14.7 (in petrol engines). The extra fuel is not burned (as there isinsufficient oxygen to complete the chemical reaction), instead it undergoes a phase change from vapor (liquid) togas. This phase change absorbs heat, and the added mass of the extra fuel reduces the average kinetic energy of thecharge and exhaust gas. Even when a catalytic converter is used, the practice of running an engine rich increasesexhaust emissions.

Center housing/hub rotating assembly

The center hub rotating assembly (CHRA) houses the shaft that connects the compressor impeller and turbine. Italso must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction.For instance, in automotive applications the CHRA typically uses a thrust bearing or ball bearing lubricated by aconstant supply of pressurized engine oil. The CHRA may also be considered "water-cooled" by having an entryand exit point for engine coolant to be cycled. Water-cooled models allow engine coolant to be used to keep thelubricating oil cooler, avoiding possible oil coking (the destructive distillation of the engine oil) from the extreme heatfound in the turbine. The development of air-foil bearings has removed this risk. Adaptation of turbochargers onnaturally aspirated internal combustion engines, on either petrol or diesel, can yield power increases of 30% to40%.

Wastegate

Main article: Wastegate

To control the pressure (therefore mass) of the air coming from the compressor (known as the "upper-deck airpressure"), the engine's exhaust gas flow is regulated before it enters the turbine with a wastegate that bypasses theturbine. A wastegate is the most common mechanical speed control system, and is often further augmented by anelectronic or manual boost controller.

The main function of a wastegate is to allow some of the exhaust to bypass the turbine when the set intake pressureis achieved. This regulates the rotational speed of the turbine and thus the turbocharger's boost. The wastegate isopened and closed by the compressed air from the turbo and can be raised by using a solenoid to regulate the



View of a turbocharger from the

turbine exhaust side, showing the

integral wastegate to the right

A recirculating type anti-surge valve

pressure fed to the wastegate membrane.[26] This solenoid is usually controlled by the engine's electronic controlunit or a boost controller.

Most modern automotive engines have wastegates that are internal to the turbocharger, although some earlierengines (such as the Audi Inline-5 in the UrS4 and S6) have external wastegates. External wastegates are more

accurate and efficient[citation needed] than internal wastegates, but are far more expensive, and thus are in generalfound only in racing cars. Amongst the modified car community, external wastegates may be configured to ventbypass gasses directly to atmosphere through a Screamer Pipe instead of routing them back into the exhaust.Although illegal in many areas, this method is often used due to the loudjet sound that is produced and potential performance gains from reducedexhaust back pressure.

Aircraft waste-gates and their operation are similar to automotiveinstallations, however there are differences, usually depending on whetherthe application is "military/performance" or "non-performance".

Anti-surge/dump/blow off valves

Main article: Blowoff valve

Turbocharged engines operating at wide open throttle and high rpmrequire a large volume of air to flow between the turbo and the inlet of theengine. When the throttle is closed, compressed air will flow to thethrottle valve without an exit (i.e., the air has nowhere to go).

In this situation, the surge can raise the pressure of the air to a level thatcan cause damage. This is because if the pressure rises high enough, acompressor stall will occur, where the stored pressurized airdecompresses backward across the impeller and out the inlet. Thereverse flow back across the turbocharger causes the turbine shaft toreduce in speed more quickly than it would naturally, possibly damagingthe turbocharger.

In order to prevent this from happening, a valve is fitted between theturbo and inlet, which vents off the excess air pressure. These are knownas an anti-surge, diverter, bypass, blow-off valve (BOV), or dump valve. It is a pressure relief valve, and isnormally operated by the vacuum in the intake manifold.

The primary use of this valve is to maintain the spinning of the turbocharger at a high speed. The air is usuallyrecycled back into the turbo inlet (diverter or bypass valves) but can also be vented to the atmosphere (blow offvalve). Recycling back into the turbocharger inlet is required on an engine that uses a mass-airflow fuel injectionsystem, because dumping the excessive air overboard downstream of the mass airflow sensor will cause anexcessively rich fuel mixture (this is because the mass-airflow sensor has already accounted for the extra air that isno longer being used). Valves that recycle the air will also shorten the time needed to re-spool the turbo aftersudden engine deceleration, since the load on the turbo when the valve is active is much lower than it is if the aircharge is vented to atmosphere.

Factors affecting lifespan



Turbochargers can be damaged by dirty or ineffective oiling systems, and most manufacturers recommend morefrequent oil changes for turbocharged engines. Many owners and some companies recommend using synthetic oils,which tend to flow more readily when cold and do not break down as quickly as conventional oils.

Because turbochargers have high operating temperatures, it is often recommended to let the engine idle for up tothree minutes before shutting off the engine if the turbocharger was used shortly before stopping. This gives time tocool the turbo rotating assembly. It also ensures that oil is supplied to the turbocharger while the turbine housing andexhaust manifold are still very hot, otherwise coking of the lubricating oil trapped in the unit may occur when theheat soaks into the bearings, causing rapid bearing wear. Small particles of burnt oil can accumulate and lead tochoking the oil supply and failure. This problem is less pronounced in diesel engines, due to specifications of higher-quality oil.

A turbo timer can keep an engine running for a pre-specified period of time, to automatically provide this cool-down period, however turbo-timers are illegal on public roads in many areas. Oil coking is also eliminated by foil

bearings[citation needed]. A more complex and problematic protective barrier against oil coking is the use of water-cooled bearing cartridges. The water boils in the cartridge when the engine is shut off and forms a naturalrecirculation to drain away the heat. Nevertheless, it is bad practice to shut the engine off while the turbo andmanifold are still glowing with heat. In custom applications using tubular headers rather than cast iron manifolds, theneed for a cooldown period is reduced because the lighter headers store much less heat than heavy cast ironmanifolds.

Race cars often use an Anti-Lag System to reduce lag at the cost of reduced turbocharger life.

Applications

Petrol powered cars

Main article: Turbocharged petrol engines

The first turbocharged passenger car was the Oldsmobile Turbo Jetfire in 1962. Today, turbocharging is commonlyused by many manufacturers of petrol powered cars. Turbocharging can be used to increase power output for a

given capacity[27] or increase fuel efficiency by allowing a smaller displacement engine to be used.

Diesel powered cars

Main article: Turbodiesel

The first production turbo diesel passenger car was the Garrett-turbocharged[28] Mercedes 300SD introduced in

1978.[29][30] Today, many automotive diesels are turbocharged, since the use of turbocharging improved efficiency,

driveability and performance of diesel engines,[29][30] greatly increasing their popularity.

Motorcycles

Main article: Turbocharged petrol engines#Motorcycles

The first example of a turbocharged bike is the 1978 Kawasaki Z1R TC. Several Japanese companies producedturbocharged high performance motorcycles in the early 1980s. Since then, few turbocharged motorcycles have



been produced.

The Dutch manufacturer EVA motorcycles builds a small series of turbocharged diesel motorcycle with an 800ccsmart CDI engine.

Trucks

The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer (Swiss Machine Works

Saurer) in 1938.[31]

Aircraft

A natural use of the turbocharger is with aircraft engines. As an aircraft climbs to higher altitudes the pressure of thesurrounding air quickly falls off. At 5,486 m (18,000 ft), the air is at half the pressure of sea level and the airframeexperiences only half the aerodynamic drag. However, since the charge in the cylinders is being pushed in by this airpressure, it means that the engine will normally produce only half-power at full throttle at this altitude. Pilots wouldlike to take advantage of the low drag at high altitudes in order to go faster, but a naturally aspirated engine will notproduce enough power at the same altitude to do so.

The table below is used to demonstrate the wide range of conditions experienced. As seen in the table below, thereis significant scope for forced induction to compensate for lower density environments.

Daytona

BeachDenver

Death

Valley

Colorado State

Highway 5

La Rinconada,

Peru,

elevation 0 m / 0 ft1,609 m /

5,280 ft

-86 m /

-282 ft

4,347 m /

14,264 ft

5,100 m /

16,732 ft

atm 1.000 0.823 1.010 0.581 0.526

bar 1.013 0.834 1.024 0.589 0.533

psia 14.696 12.100 14.846 8.543 7.731

kPa 101.3 83.40 102.4 58.90 53.30

A turbocharger remedies this problem by compressing the air back to sea-level pressures, or even much higher, inorder to produce rated power at high altitude. Since the size of the turbocharger is chosen to produce a givenamount of pressure at high altitude, the turbocharger is over-sized for low altitude. The speed of the turbocharger iscontrolled by a wastegate. Early systems used a fixed wastegate, resulting in a turbocharger that functioned muchlike a supercharger. Later systems utilized an adjustable wastegate, controlled either manually by the pilot or by anautomatic hydraulic or electric system. When the aircraft is at low altitude the wastegate is usually fully open, ventingall the exhaust gases overboard. As the aircraft climbs and the air density drops, the wastegate must continuouslyclose in small increments to maintain full power. The altitude at which the wastegate is fully closed and the engine isstill 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.

With older supercharged aircraft, the pilot must continually adjust the throttle to maintain the required manifoldpressure during ascent or descent. The pilot must also take great care to avoid overboosting the engine and causingdamage, especially during emergencies such as go-arounds. In contrast, modern turbocharger systems use anautomatic wastegate, which controls the manifold pressure within parameters preset by the manufacturer. For these



systems, as long as the control system is working properly and the pilot's control commands are smooth anddeliberate, a turbocharger will not overboost the engine and damage it.

Yet the majority of World War II engines used superchargers, because they maintained three significantmanufacturing advantages over turbochargers, which were larger, involved extra piping, and required exotic high-temperature materials in the turbine and pre-turbine section of the exhaust system. The size of the piping alone is aserious issue; American fighters Vought F4U and Republic P-47 used the same engine but the huge barrel-likefuselage of the latter was, in part, needed to hold the piping to and from the turbocharger in the rear of the plane.Turbocharged piston engines are also subject to many of the same operating restrictions as gas turbine engines.Pilots must make smooth, slow throttle adjustments to avoid overshooting their target manifold pressure. The fuelmixture must often be adjusted far on the rich side of stoichiometric combustion needs to avoid pre-detonation inthe engine when running at high power settings. In systems using a manually operated wastegate, the pilot must becareful not to exceed the turbocharger's maximum rpm. Turbocharged engines require a cooldown period afterlanding to prevent cracking of the turbo or exhaust system from thermal shock. Turbocharged engines requirefrequent inspections of the turbocharger and exhaust systems for damage due to the increased heat, increasingmaintenance costs.

Today, most general aviation aircraft are naturally aspirated.[citation needed] The small number of modern aviationpiston engines designed to run at high altitudes in general use a turbocharger or turbo-normalizer system rather than

a supercharger.[citation needed] The change in thinking is largely due to economics. Aviation gasoline was onceplentiful and cheap, favoring the simple but fuel-hungry supercharger. As the cost of fuel has increased, thesupercharger has fallen out of favor.

Turbocharged aircraft often occupy a performance range between that of normally aspirated piston-poweredaircraft and turbine-powered aircraft. The increased maintenance costs of a turbocharged engine are consideredworthwhile for this purpose, as a turbocharged piston engine is still far cheaper than any turbine engine.

As the turbocharged aircraft climbs, however, the pilot (or automated system) can close the wastegate, forcingmore exhaust gas through the turbocharger turbine, thereby maintaining manifold pressure during the climb, at leastuntil the critical pressure altitude is reached (when the wastegate is fully closed), after which manifold pressure willfall. 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. This allows flying "above the weather". Inmanually controlled wastegate systems, the pilot must take care not to overboost 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 theturbocharger.

In non-high-performance turbocharged aircraft, the turbocharger is solely used to maintain sea-level manifold

pressure during the climb (this is called turbo-normalizing).[22]

Modern turbocharged aircraft usually forgo any kind of temperature compensation, because the turbochargers arein general small and the manifold pressures created by the turbocharger are not very high. Thus, the added weight,cost, and complexity of a charge cooling system are considered to be unnecessary penalties. In those cases, theturbocharger is limited by the temperature at the compressor outlet, and the turbocharger and its controls aredesigned to prevent a large enough temperature rise to cause detonation. Even so, in many cases the engines aredesigned to run rich in order to use the evaporating fuel for charge cooling.

Marine and land-based diesel turbochargers



A medium-sized six-cylinder marine

Diesel-engine, with turbocharger and

exhaust in the foreground

Turbocharging, which is common on diesel engines in automobiles, trucks, tractors, and boats is also common inheavy machinery such as locomotives, ships, and auxiliary powergeneration.

Turbocharging can dramatically improve an engine's specific power and

power-to-weight ratio, performance characteristics, which are normally

poor in non-turbocharged diesel engines.Diesel engines have no detonation because diesel fuel is injected at the

end of the compression stroke, ignited by compression heat. Because ofthis, diesel engines can use much higher boost pressures than spark

ignition engines, limited only by the engine's ability to withstand theadditional heat and pressure.

Turbochargers are also employed in certain two-stroke cycle diesel engines, which would normally require a Rootsblower for aspiration. In this specific application, mainly Electro-Motive Diesel (EMD) 567, 645, and 710 Seriesengines, the turbocharger is initially driven by the engine's crankshaft through a gear train and an overriding clutch,thereby providing aspiration for combustion. After the engine achieves combustion, and after the exhaust gasesreach sufficient temperature, the overriding clutch disengages the turbo-compressor from the gear train and theturbo-compressor is thereafter driven exclusively by the turbine, which, in turn, is driven by the exhaust gases. In theEMD application, the turbocharger is used for normal aspiration during starting and low power output settings andis used for true turbocharging during medium and high power output settings. This is particularly beneficial at highaltitudes, as are often encountered on western U.S. railroads. One EMD engine model was fitted with a "locked"turbocharger; it was used in normal aspiration mode during starting and all power output settings.

Business

Sales of turbochargers are expected to increase, due to increasingly strict emissions regulations.[32][33] The largest

manufacturers in Europe are Garrett (By Honeywell) and BorgWarner,[32][33] while in America the largest

manufacturers of turbochargers are Honeywell and BorgWarner.[2]

See also

Boost gaugetwincharger

exhaust pulse pressure chargingHybrid turbocharger

Twin-turboVariable geometry turbocharger

References

1. ^ Nice, Karim (2000-12-04). "HowStuffWorks "How Turbochargers Work""(http://auto.howstuffworks.com/turbo.htm) . Auto.howstuffworks.com.http://auto.howstuffworks.com/turbo.htm. Retrieved 2012-06-01.

2. ̂a b [1] (http://reviews.cnet.com/8301-13746_7-20045466-48.html)



3. ^ Baines, Nicholas C. (2005). Fundamentals of Turbocharging. Concepts ETI. ISBN 0-933283-14-8.

4. ^ History of the Supercharger (http://www.calaisturbo.org/history-of-the-supercharger.php) ,http://www.calaisturbo.org/history-of-the-supercharger.php, retrieved 2011-06-30

5. ^ Porsche Turbo: The Full History. Peter Vann. MotorBooks International, 11 Jul 2004

6. ^ Compressor Performance: Aerodynamics for the User. M. Theodore Gresh. Newnes, 29 Mar 2001

7. ^ Diesel and gas turbine progress, Volume 26. Diesel Engines, inc., 1960

8. ̂a b "Hill Climb" (http://www.airspacemag.com/history-of-flight/climb.html?c=y&page=1) . Air & SpaceMagazine. http://www.airspacemag.com/history-of-flight/climb.html?c=y&page=1. Retrieved 2010-08-02.

9. ^ "The Turbosupercharger and the Airplane Powerplant." (http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm). http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm.

10. ^ "supercharger - Wiktionary" (http://en.wiktionary.org/wiki/supercharger) . En.wiktionary.org.http://en.wiktionary.org/wiki/supercharger. Retrieved 2012-06-01.

11. ^ "Gallery" (http://picturegallery.imeche.org/ViewLarger.aspx?PID=422&RAID=30) . Picturegallery.imeche.org.http://picturegallery.imeche.org/ViewLarger.aspx?PID=422&RAID=30. Retrieved 2011-04-09.

12. ̂a b c "HowStuffWorks "What is the difference between a turbocharger and a supercharger on a car\'s engine?""(http://auto.howstuffworks.com/question122.htm) . Auto.howstuffworks.com. 2000-04-01.http://auto.howstuffworks.com/question122.htm. Retrieved 2012-06-01.

13. ^ "supercharging" (http://www.elsberg-tuning.dk/supercharging.html) . Elsberg-tuning.dk. http://www.elsberg-tuning.dk/supercharging.html. Retrieved 2012-06-01.

14. ^ Chris Longhurst. "The Fuel and Engine Bible: page 5 of 6"(http://www.carbibles.com/fuel_engine_bible_pg5.html) . Car Bibles.http://www.carbibles.com/fuel_engine_bible_pg5.html. Retrieved 2012-06-01.

15. ^ "How to twincharge an engine" (http://www.torquecars.com/tuning/twincharging.php) . Torquecars.com.http://www.torquecars.com/tuning/twincharging.php. Retrieved 2012-06-01.

16. ^ "Four Stroke Engine Basics" (http://www.compgoparts.com/TechnicalResources/FourStrokeEngineBasics.asp) .Compgoparts.com. http://www.compgoparts.com/TechnicalResources/FourStrokeEngineBasics.asp. Retrieved2012-06-01.

17. ^ Brain, Marshall (2000-04-05). "HowStuffWorks "Internal Combustion""(http://www.howstuffworks.com/engine1.htm) . Howstuffworks.com.http://www.howstuffworks.com/engine1.htm. Retrieved 2012-06-01.

18. ^ "Volumetric Efficiency (and the REAL factor: MASS AIRFLOW), by EPI Inc" (http://www.epi-eng.com/piston_engine_technology/volumetric_efficiency.htm) . Epi-eng.com. 2011-11-18. http://www.epi-eng.com/piston_engine_technology/volumetric_efficiency.htm. Retrieved 2012-06-01.

19. ^ "Variable-Geometry Turbochargers" (http://large.stanford.edu/courses/2010/ph240/veltman1/) .Large.stanford.edu. 2010-10-24. http://large.stanford.edu/courses/2010/ph240/veltman1/. Retrieved 2012-06-01.

20. ^ "How Turbo Chargers Work" (http://conceptengine.tripod.com/conceptengine/id5.html) .Conceptengine.tripod.com. http://conceptengine.tripod.com/conceptengine/id5.html. Retrieved 2012-06-01.

21. ^ "Effects of Variable Geometry Turbochargers in Increasing Efficiency and Reducing Lag - Thermal Systems"(http://me1065.wikidot.com/variable-geometry-turbochargers) . Me1065.wikidot.com. 2007-12-06.DOI:10.1243/0954407991526766 (http://dx.doi.org/10.1243%2F0954407991526766) .http://me1065.wikidot.com/variable-geometry-turbochargers. Retrieved 2012-06-01.

22. ̂a b c d Knuteson, Randy (July 1999). "Boosting Your Knowledge of Turbocharging"(http://www.kellyaerospace.com/articles/Turbocharging.pdf) . Aircraft Maintenance Technology.http://www.kellyaerospace.com/articles/Turbocharging.pdf. Retrieved 18 April 2012.

23. ̂a b Parkhurst, Terry. "Turbochargers: an interview with Garrett’s Martin Verschoor"(http://www.acarplace.com/cars/turbochargers.html) . Allpar, LLC.http://www.acarplace.com/cars/turbochargers.html. Retrieved 12 December 2006.

24. ^ Mechanical engineering: Volume 106, Issues 7-12; p.51

25. ^ Popular Science. Detroit's big switch to Turbo Power. Apr 1984.

26. ^ Nice, Karim. "How Turbochargers Work" (http://auto.howstuffworks.com/turbo3.htm) .Auto.howstuffworks.com. http://auto.howstuffworks.com/turbo3.htm. Retrieved 2010-08-02.

27. ^ Richard Whitehead (2010-05-25). "Road Test: 2011 Mercedes-Benz CL63 AMG - The National"



(http://www.thenational.ae/lifestyle/motoring/road-test-2011-mercedes-benz-cl63-amg) . Thenational.ae.http://www.thenational.ae/lifestyle/motoring/road-test-2011-mercedes-benz-cl63-amg. Retrieved 2012-06-01.

28. ^ http://www.honeywell.com/sites/ts/tt/100Years_Turbo3_C83869114-FF16-C7FE-13F7-7CD478B60F02_H6470A0D1-554D-CF34-4086-9E97AA11107E.htm

29. ̂a b "The history of turbocharging" (http://en.turbolader.net/Technology/History.aspx) . En.turbolader.net. 1959-10-27. http://en.turbolader.net/Technology/History.aspx. Retrieved 2012-06-01.

30. ̂a b http://www.theturboforums.com/turbotech/main.htm

31. ^ "BorgWarner turbo history" (http://www.turbodriven.com/en/turbofacts/default.aspx) . Turbodriven.com.http://www.turbodriven.com/en/turbofacts/default.aspx. Retrieved 2010-08-02.

32. ̂a b Kitamura, Makiko (2008-07-24). "IHI Aims to Double Turbocharger Sales by 2013 on Europe Demand"(http://www.bloomberg.com/apps/news?pid=newsarchive&sid=aYKNPOS_J37k) . Bloomberg.http://www.bloomberg.com/apps/news?pid=newsarchive&sid=aYKNPOS_J37k. Retrieved 2012-06-01.

33. ̂a b CLEPA CEO Lars Holmqvist is retiring (2002-11-18). "Turbochargers - European growth driven by spread tosmall cars" (http://www.just-auto.com/analysis/turbochargers-european-growth-driven-by-spread-to-small-cars_id86995.aspx) . Just-auto.com. http://www.just-auto.com/analysis/turbochargers-european-growth-driven-by-spread-to-small-cars_id86995.aspx. Retrieved 2012-06-01.

External links

Don Sherman (February 2006). "Happy 100th Birthday to the Turbocharger"(http://www.automobilemag.com/features/news/0602_turbocharger_history/index.html) . Automobile

Magazine. http://www.automobilemag.com/features/news/0602_turbocharger_history/index.html.Mohawk Innovative Technology, Inc.'s Oil Free Turbocharger(http://www.miti.cc/new_products.html#OilFreeTurbocharger)

NASA Oil Free Turbocharger(http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990018837_1999018726.pdf)

Video showing how a turbocharger works (http://turbo.honeywell.com/whats-new-in-turbo/video/how-a-turbocharger-works/)

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