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In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that compresses the intake air, forcing more air into the engine in order to produce more power for a given displacement.[1]
Turbochargers are distinguished from in that a turbocharger is powered by the kinetic energy of the exhaust gases, 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.
The 1905 patent by Alfred Büchi, a Swiss engineer working at Sulzer is often considered the birth of the turbocharger. This patent was for a compound radial engine with an exhaust-driven axial flow turbine 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, for their intended use on the Renault engines used by French fighter planes. Separately, testing in 1917 by the National Advisory Committee for Aeronautics (NACA) and Sanford Alexander Moss 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 in the United States using the Liberty L-12 aircraft engine.
The first commercial application of a turbocharger was in June 1924 when the first heavy duty turbocharger, model VT402, was delivered from the Baden works of Brown, Boveri & Cie, under the supervision of Alfred Büchi, to SLM, Swiss Locomotive and Machine Works in Winterthur. This was followed very closely in 1925, when Alfred Büchi successfully installed turbochargers on ten-cylinder diesel engines, increasing the power output from .Compressor Performance: Aerodynamics for the User. M. Theodore Gresh. Newnes, 29 March 2001Diesel and gas turbine progress, Volume 26. Diesel Engines, 1960 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.Ernst Jenny: "Der BBC-Turbolader." Birkhäuser, Basel, 1993, ISBN 978-3-7643-2719-4. "Buchbesprechung." Neue Zürcher Zeitung, May 26, 1993, p. 69., issued 1989-07-13, assigned to BBC Brown Boveri AG, Baden, Switzerland
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.
The turbo succeeded in motorsport, but took its time. The 1968 Indianapolis 500 was the first to be won with a turbocharged engine; turbos have won on the fast oval track ever since. Porsche pioneered turbos in engines derived from the 1963 Porsche 911, which had an air-cooled flat six engine just like the Chevrolet Corvair, but got turbocharged ten years later. Porsche 935 and Porsche 936 won both kinds of Sportcars World Championships in 1976, as well as the Le Mans 24h, proving that they could be reliable and fast. In Formula One, capacity was limited to only 1.5 litre, with the first race victories coming in the late 1970s, and the first F1 World Championship in 1983, with a BMW M10-based 4-cylinder engine that dates back to 1961.
Turbodiesel passenger cars appeared in the 1970s, with the Mercedes 300 D. Greater adoption of turbocharging in passenger cars began in the 1980s, as a way to increase the performance of smaller displacement engines.
The main components of the turbocharger are:
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.Mechanical engineering: Volume 106, Issues 7-12; p.51Popular Science. Detroit's big switch to Turbo Power. Apr 1984. 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, since it has lower rotational inertia, 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 turbine instead of a radial turbine.
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.
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.
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.
Additional components that are commonly used in conjunction with turbochargers are:
Methods to reduce turbo lag include:
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 rpm.
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.
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.
Failure of the seals will cause oil to leak into the exhaust system causing blue-gray smoke or a runaway diesel.
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