![Turbocharger](https://upload.wikimedia.org/wikipedia/commons/7/76/Turbocharger.jpg)
In an
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal c ...
, a turbocharger (often called a turbo) is a
forced induction
In an internal combustion engine, forced induction is where turbocharging or supercharging is used to increase the density of the intake air. Engines without forced induction are classified as naturally aspirated.
Operating principle Overvi ...
device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to produce more power for a given
displacement
Displacement may refer to:
Physical sciences
Mathematics and Physics
* Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
.
The current categorisation is that a turbocharger is powered by the kinetic energy of the exhaust gasses, whereas a
supercharger is mechanically powered (usually by a belt from the engine's crankshaft). However, up until the mid-20th century, a turbocharger was called a "turbosupercharger" and was considered a type of supercharger.
History
Prior to the invention of the turbocharger,
forced induction
In an internal combustion engine, forced induction is where turbocharging or supercharging is used to increase the density of the intake air. Engines without forced induction are classified as naturally aspirated.
Operating principle Overvi ...
was only possible using mechanically-powered
superchargers. Use of superchargers began in 1878, when several supercharged two-stroke gas engines were built using a design by Scottish engineer
Dugald Clerk
Sir Dugald Clerk (sometimes written as Dugald Clark) KBE, LLD FRS (1854, Glasgow – 1932, Ewhurst, Surrey) was a Scottish engineer who designed the world's first successful two-stroke engine
in 1878 and patented it in England in 1881. He wa ...
. Then in 1885,
Gottlieb Daimler
Gottlieb Wilhelm Daimler (; 17 March 1834 – 6 March 1900) was a German engineer, industrial designer and industrialist born in Schorndorf ( Kingdom of Württemberg, a federal state of the German Confederation), in what is now Germany. He w ...
patented the technique of using a gear-driven pump to force air into an internal combustion engine.
The 1905 patent by
Alfred Büchi
Alfred Büchi (July 11, 1879 – October 27, 1959) was a Swiss engineer and inventor. He was best known as the inventor of turbocharging. Büchi was born July 11, 1879, in Winterthur, Switzerland, growing up there and in Ludwigshafen. He wa ...
, a Swiss engineer working at
Sulzer is often considered the birth of the turbocharger.
This patent was for a compound
radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...
with an exhaust-driven axial flow
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
and compressor mounted on a common shaft.
The first prototype was finished in 1915 with the aim of overcoming the power loss experienced by aircraft engines due to the decreased density of air at high altitudes.
However, the prototype was not reliable and did not reach production.
Another early patent for turbochargers was applied for in 1916 by French steam turbine inventor
Auguste Rateau
Auguste Rateau (13 October 1863 – 13 January 1930) was an engineer and industrialist born in Royan, France, specializing in turbines.
Biography
After studies, first at the École Polytechnique and then at the École des Mines de Paris, he beg ...
, for their intended use on the Renault engines used by French fighter planes.
Separately, testing in 1917 by the
National Advisory Committee for Aeronautics
The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...
(NACA) and
Sanford Alexander Moss
Sanford Alexander Moss (August 23, 1872 – November 10, 1946) was an American aviation engineer, who was the first to use a turbocharger on an aircraft engine.
Life and career
Sanford Moss was born 1872 in San Francisco, California to Ernest ...
showed that a turbocharger could enable an engine to avoid any power loss (compared with the power produced at sea level) at an altitude of up to above sea level.
The testing was conducted at
Pikes Peak
Pikes Peak is the highest summit of the southern Front Range of the Rocky Mountains, in North America. The ultra-prominent fourteener is located in Pike National Forest, west of downtown Colorado Springs, Colorado. The town of Manitou S ...
in the United States using the
Liberty L-12 aircraft engine.
The first commercial application of a turbocharger was in 1925, when Alfred Büchi successfully installed turbochargers on ten-cylinder diesel engines, increasing the power output from .
This engine was used by the German Ministry of Transport for two large passenger ships called the ''Preussen'' and . The design was licensed to several manufacturers and turbochargers began to be used in marine, railcar and large stationary applications.
Turbochargers were used on several aircraft engines during World War II, beginning with the
Boeing B-17 Flying Fortress in 1938, which used turbochargers produced by General Electric.
Other early turbocharged airplanes included the
Consolidated B-24 Liberator,
Lockheed P-38 Lightning,
Republic P-47 Thunderbolt and experimental variants of the
Focke-Wulf Fw 190.
The first practical application for trucks was realized by Swiss truck manufacturing company
Saurer in the 1930s. BXD and BZD engines were manufactured with optional turbocharging from 1931 onwards. The Swiss industry played a pioneering role with turbocharging engines as witnessed by Sulzer, Saurer and
Brown, Boveri & Cie
Brown, Boveri & Cie. (Brown, Boveri & Company; BBC) was a Swiss group of electrical engineering companies.
It was founded in Zürich, in 1891 by Charles Eugene Lancelot Brown and Walter Boveri who worked at the Maschinenfabrik Oerlikon. In 1 ...
.
Automobile manufacturers began research into turbocharged engines during the 1950s, however the problems of "turbo lag" and the bulky size of the turbocharger were not able to be solved at the time.
The first turbocharged cars were the short-lived
Chevrolet Corvair Monza and the
Oldsmobile Jetfire, both introduced in 1962.
Greater adoption of turbocharging in passenger cars began in the 1980s, as a way to increase the performance of smaller
displacement
Displacement may refer to:
Physical sciences
Mathematics and Physics
* Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
engines.
Design
Like other forced induction devices, a
compressor in the turbocharger pressurises the intake air before it enters the
inlet manifold. In the case of a turbocharger, the compressor is powered by the kinetic energy of the engine's exhaust gases, which is extracted by the turbocharger's
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
.
The main components of the turbocharger are:
* Turbine – usually a
radial turbine design
* Compressor – usually a
centrifugal compressor
Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
They achieve pressure rise by adding energy to the continuous flow of fluid through t ...
* Center housing hub rotating assembly
Turbine
![Turbo-turbine](https://upload.wikimedia.org/wikipedia/commons/f/fd/Turbo-turbine.jpg)
The
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
section (also called the "hot side" or "exhaust side" of the turbo) is where the rotational force is produced, in order to power the compressor (via a rotating
shaft through the center of a turbo. After the exhaust has spun the turbine it continues into the exhaust and out of the vehicle.
The turbine uses a series of blades to convert kinetic energy from the flow of exhaust gases to mechanical energy of a rotating shaft (which is used to power the compressor section). The turbine housings direct the gas flow through the turbine section, and the turbine itself can spin at speeds of up to 250,000 rpm. Some turbocharger designs are available with multiple turbine housing options, allowing a housing to be selected to best suit the engine's characteristics and the performance requirements.
A turbocharger's performance is closely tied to its size,
and the relative sizes of the turbine wheel and the compressor wheel. Large turbines typically require higher exhaust gas flow rates, therefore increasing turbo lag and increasing the boost threshold. Small turbines can produce boost quickly and at lower flow rates, but can be a limiting factor in the peak power produced by the engine.
[A National Maritime Academy Presentation]
Variable Turbine Geometry
Various technologies, as described in the following sections, are often aimed at combining the benefits of both small turbines and large turbines.
Large diesel engines often use a single-stage
axial inflow turbine instead of a radial turbine.
Twin-scroll
A twin-scroll turbocharger uses two separate exhaust gas inlets, to make use of the pulses in the flow of the exhaust gasses from each cylinder. In a standard (single-scroll) turbocharger, the exhaust gas from all cylinders are combined and enter the turbocharger via a single intake, which causes the gas pulses from each cylinder to interfere with each other. For a twin-scroll turbocharger, the cylinders are split into two groups in order to maximise the pulses. The exhaust manifold keeps these two groups of cylinders separated, then they travel through two separate spiral chambers ("scrolls") before entering the turbine housing via two separate nozzles. The
scavenging
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding ...
effect of these gas pulses recovers more energy from the exhaust gases, minimizes parasitic back losses and improves responsiveness at low engine speeds.
Another common feature of twin-scroll turbochargers is that the two nozzles are different sizes: the smaller nozzle is installed at a steeper angle and is used for low-rpm response, while the larger nozzle is less angled and optimised for times when high outputs are required.
File:Mitsubishi twin-scroll turbo.JPG , Cutaway view showing the two scrolls of a Mitsubishi twin-scroll (the larger scroll is illuminated in red)
File:Twin-scroll turbo T-GDI.jpg , Transparent exhaust manifold and turbo scrolls on a Hyundai Gamma engine
The Hyundai Gamma engine was introduced in 2006 to replace the existing Hyundai Alpha engine. There are 1.4 L and 1.6 L versions of this engine.
The Gamma II can apparently run in Atkinson cycle (leaving intake open longer for more complete burn ...
, showing the paired cylinders (1 & 4 and 2 & 3)
Variable-geometry
Variable-geometry turbocharger
Variable-geometry turbochargers (VGTs), occasionally known as variable-nozzle turbines (VNTs), are a type of turbochargers, usually designed to allow the effective aspect ratio of the turbocharger to be altered as conditions change. This is done ...
s (also known as ''variable-nozzle turbochargers'') are used to alter the effective
aspect ratio of the turbocharger as operating conditions change. This is done with the use of adjustable vanes located inside the turbine housing between the inlet and turbine, these vanes affect flow of gases towards the turbine. Some variable-geometry turbochargers use a rotary
electric actuator
A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, ...
to open and close the vanes, while others use a
pneumatic actuator
A pneumatic control valve actuator converts energy (typically in the form of compressed air) into mechanical motion. The motion can be rotary or linear, depending on the type of actuator.
Principle of operation
A Pneumatic actuator mainly co ...
.
If the turbine's aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, variable-geometry turbochargers often have reduced lag, a lower boost threshold, and greater efficiency at higher engine speeds.
The benefit of variable-geometry turbochargers is that the optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
Electrically-assisted turbochargers
An
electrically-assisted turbocharger combines a traditional exhaust-powered turbine with an electric motor, in order to reduce turbo lag. This differs from an
electric supercharger
An electric supercharger is a specific type of supercharger for internal combustion engines that uses an electrically powered forced-air system that contains an electric motor to pressurize the intake air. By pressurizing the air available to th ...
, which solely use an electric motor to power the compressor.
Compressor
![Turbo-compressor](https://upload.wikimedia.org/wikipedia/commons/8/8e/Turbo-compressor.jpg)
The
compressor draws in outside air through the engine's intake system, pressurises it, then feeds it into the
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Intern ...
s (via the
inlet manifold). The compressor section of the turbocharger consists of an impeller, a diffuser and a volute housing. The operating characteristics of a compressor is described by the
compressor map A compressor map is a chart which shows the performance of a turbomachinery compressor. This type of compressor is used in gas turbine engines, for supercharging reciprocating engines and for industrial processes, where it is known as a dynamic co ...
.
Ported shroud
Some turbochargers use a "ported shroud", whereby a ring of holes or circular grooves allows air to bleed around the compressor blades. Ported shroud designs can have greater resistance to compressor surge and can improve the efficiency of the compressor wheel.
Center hub rotating assembly
The center hub rotating assembly (CHRA) houses the shaft that connects the turbine to the compressor. A lighter shaft can help reduce turbo lag. The CHRA also contains a bearing to allow this shaft to rotate at high speeds speed with minimal friction.
Some CHRAs are water-cooled and have pipes for the engine's coolant to flow through. One reason for water cooling is to protect the turbocharger's lubricating oil from overheating.
Supporting components
![TurbochargedGasolineEngineFlowDiagram](https://upload.wikimedia.org/wikipedia/commons/2/2b/TurbochargedGasolineEngineFlowDiagram.png)
The simplest type of turbocharger is the ''free floating'' turbocharger.
This system would be able to achieve maximum boost at maximum engine revs and full throttle, however additional components are needed to produce an engine that is driveable in a range load and rpm conditions.
Additional components that are commonly used in conjunction with turbochargers are:
*
Intercooler - a radiator used to cool the intake air after it has been pressurised by the turbocharger
*
Water injection - spraying water into the combustion chamber, in order to cool the intake air
*
Wastegate
A wastegate is a valve that controls the flow of exhaust gases to the turbine wheel in a turbocharged engine system.Robson, D. (2018). Aircraft General Knowledge. Aviation Theory Centre Pty Ltd. .
Diversion of exhaust gases regulates the turbine ...
- many turbochargers are capable of producing boost pressures in some circumstances that are higher than the engine can safely withstand, therefore a wastegate is often used to limit the amount of exhaust gases that enters the turbine
*
Blowoff valve
A blowoff valve (also called dump valve or compressor bypass valve) is a pressure release system present in most petrol turbocharged engines. Blowoff valves are used to reduce pressure in the intake system as the throttle is closed, thus prevent ...
- to prevent ''compressor stall'' when the throttle is closed
Turbo lag and boost threshold
Turbo lag refers to delaywhen the engine rpm is within the turbocharger's operating rangethat occurs between pressing the throttle and the turbocharger spooling up to provide boost pressure. This delay is due to the increasing exhaust gas flow (after the throttle is suddenly opened) taking time to spin up the turbine to speeds where boost is produced. The effect of turbo lag is reduced
throttle response Throttle response or vehicle responsiveness is a measure of how quickly a vehicle's prime mover, such as an internal combustion engine, can increase its power output in response to a driver's request for acceleration. Throttles are not used in diese ...
, in the form of a delay in the power delivery. Superchargers do not suffer from turbo lag, because the compressor mechanism is driven directly by the engine.
Methods to reduce turbo lag include:
* Lowering the rotational inertia of the turbocharger by using lower radius parts and ceramic and other lighter materials
* Changing the turbine's ''aspect ratio''
* Increasing upper-deck air pressure (compressor discharge) and improving wastegate response
* Reducing bearing frictional losses, e.g., using a
foil bearing
A foil bearing, also known as a foil-air bearing, is a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid (usually air) pushes the foil away from ...
rather than a conventional oil bearing
* Using
variable-nozzle or
twin-scroll turbochargers
* Decreasing the volume of the upper-deck piping
* Using multiple turbochargers sequentially or in parallel
* Using an
antilag system
The anti-lag system (ALS) is a method of reducing turbo lag or effective compression used on turbocharged engines to minimize turbo lag on racing or performance cars. It works by delaying the ignition timing and adding extra fuel (and sometimes air ...
* Using a turbocharger spool valve to increase exhaust gas flow speed to the (twin-scroll) turbine
* Using a
butterfly valve
A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates.
Principle of operation
Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves ...
to force exhaust gas through a smaller passage in the turbo inlet
* Electric turbochargers
and
hybrid turbocharger
An electrically-assisted turbocharger (EAT) is an arrangement where an electric motor assists the gas-driven turbocharger in providing forced induction, particular at times when exhaust gas flow is insufficient to produce the desired boost. So ...
s.
A similar phenomenon that is often mistaken for turbo lag is the boost threshold. This is where the engine speed (rpm) is currently below the operating range of the turbocharger system, therefore the engine is unable to produce significant boost. At low rpm, the exhaust gas flow rate is unable to spin the turbine sufficiently.
The boost threshold causes delays in the power delivery at low rpm (since the unboosted engine must accelerate the vehicle to increase the rpm above the boost threshold), while turbo lag causes delay in the power delivery at higher PRM.
Use of multiple turbochargers
Some engines use multiple turbochargers, usually to reduce turbo lag, increase the range of rpm where boost is produced, or simplify the layout of the intake/exhaust system. The most common arrangement is twin turbochargers, however triple-turbo or quad-turbo arrangements have been occasionally used in production cars.
Turbocharging versus supercharging
The key difference between a turbocharger and a 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 the kinetic energy of the engine's
exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
.
A turbocharger does not place a direct mechanical load on the engine, although turbochargers place exhaust back pressure on engines, increasing pumping losses.
Supercharged engines are common in applications where throttle response is a key concern, and supercharged engines are less likely to
heat soak the intake air.
Twincharging
A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses of both. This technique is called ''twincharging''.
Applications
![Schiffsdiesel](https://upload.wikimedia.org/wikipedia/commons/b/b2/Schiffsdiesel.jpg)
Turbochargers have been used in the following applications:
*
Petrol-powered car engines
*
Diesel-powered car and van engines
*
Motorcycle engines
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle Steering, steered by a Motorcycle handlebar, handlebar. Motorcycle design varies greatly to suit a range of different purposes: Long-distance ...
(quite rarely)
* Diesel-powered
truck engines, beginning with a
Saurer truck in 1938
*
Bus
A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
and
coach diesel engines
*
Aircraft piston engines
*
Marine engines
*
Locomotive and
diesel multiple unit engines for trains
*
Stationary/industrial engines
In 2017, 27% of vehicles sold in the US were turbocharged. In Europe 67% of all vehicles were turbocharged in 2014. Historically, more than 90% of turbochargers were diesel, however, adoption in petrol engines is increasing.
The companies which manufacture the most turbochargers in Europe and the U.S. are
Garrett Motion (formerly Honeywell),
BorgWarner and
Mitsubishi Turbocharger.
Safety
Turbocharger failures and resultant high exhaust temperatures are among the causes of car fires.
Why trucks catch fire
Australian Road Transport Suppliers Association (ARTSA). November 2006. Retrieved 2020-07-22.
Failure of the seals will cause oil to leak into the cylinders causing blue-gray smoke. In diesel engines, this can cause an overspeed, a condition known as diesel engine runaway
Diesel engine runaway is a rare condition affecting diesel engines, in which the engine draws extra fuel from an unintended source and overspeeds at higher and higher RPM, producing up to ten times the engine's rated output until destroyed by mec ...
.
See also
* Boost gauge
* Engine downsizing In the automotive industry, engine downsizing is the practice of utilizing smaller combustion engines over larger ones of the same power capacity when manufacturing vehicles. It is the result of car manufacturers attempting to provide more efficient ...
* Exhaust pulse pressure charging Exhaust pulse pressure charging (EPPC) is a system for supercharging two-stroke diesel engines of the loop-scavenge type. Loop-scavenge engines cannot be pressure-charged in the same way as uniflow engines or four-stroke engines because the inlet ...
References
{{Authority control
Engine components