A turbo-compound engine is a

reciprocating engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...

that employs a

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 e ...

to recover energy from the exhaust gases. Instead of using that energy to drive a

turbocharger In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction 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 pro ...

as found in many high-power

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...

s, the energy is instead sent to the output shaft to increase the total power delivered by the engine. The turbine is usually mechanically connected to the

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...

, as on the

Wright R-3350 Duplex-Cyclone The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly . Power ranged from 2,200 to over 3,700 hp (1,640 to 2,760 kW), depending on the model. ...

, but electric and hydraulic power recovery systems have been investigated as well. As this recovery process does not increase

fuel consumption A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

, it has the effect of reducing the specific fuel consumption, the ratio of fuel use to power. Turbo-compounding was used for commercial airliners and similar long-range, long-endurance roles before the introduction of

turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...

engines. Examples using the Duplex-Cyclone include the

Douglas DC-7B The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. A derivative of the DC-6, it was the last major piston engine-powered transport made by Douglas, being developed shortly after the ea ...

and

Lockheed L-1049 Super Constellation The Lockheed L-1049 Super Constellation is an American aircraft, a member of the Lockheed Constellation aircraft line. The L-1049 was Lockheed's response to the successful Douglas DC-6 airliner, first flying in 1950. The aircraft was also produc ...

, while other designs did not see production use.

Concept

Most piston engines have a hot exhaust that still contains considerable undeveloped

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...

that could be used for propulsion if extracted. A turbine is often used to extract energy from such a stream of gases. A conventional gas turbine is fed high-pressure, high-velocity air, extracts energy from it, and leaves as a lower-pressure, slower-moving stream. This action has the side-effect of increasing the upstream pressure, which makes it undesirable for use with a piston engine as it increases the back-pressure in the engine, which decreases scavenging of the

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 ...

from the cylinders and thereby lowers the efficiency of the piston portion of a compound engine. Through the late 1930s and early 1940s one solution to this problem was the introduction of "jet stack" exhaust manifolds. These were simply short sections of metal pipe attached to the exhaust ports, shaped so that they would interact with the airstream to produce a jet of air that produced forward thrust. Another

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

introduction was the use of the Meredith effect to recover heat from the radiator system to provide additional thrust. By the late-war era, turbine development had improved dramatically and led to a new turbine design known as the "blowdown turbine" or "power-recovery turbine". This design extracts energy from the momentum of the moving exhaust, but does not appreciably increase back-pressure. This means it does not have the undesirable effects of conventional designs when connected to the exhaust of a piston engine, and a number of manufacturers began studying the design.

History

The first aircraft engine to be tested with a power-recovery turbine was the

Rolls-Royce Crecy The Rolls-Royce Crecy was a British experimental two-stroke, 90-degree, V12, liquid-cooled aero-engine of 1,593.4 cu.in (26.11 L) capacity, featuring sleeve valves and direct petrol injection. Initially intended for a high-speed "sprint" i ...

. This was used primarily to drive a geared centrifugal supercharger, although it was also coupled to the crankshaft and gave an extra 15 to 35 percent fuel economy. Blowdown turbines became relatively common features in the late- and post-war era, especially for engines designed for long overwater flights. Turbo-compounding was used on several

airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spe ...

engines after

, including the

Napier Nomad The Napier Nomad is a British diesel aircraft engine designed and built by Napier & Son in 1949. They combined a piston engine with a turbine to recover energy from the exhaust and thereby improve fuel economy. Two versions were tested, the c ...

and the

Wright R-3350 The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly . Power ranged from 2,200 to over 3,700 hp (1,640 to 2,760 kW), depending on the model. ...

. The exhaust restriction imparted by the three blowdown turbines used on the Wright R-3350 is equal to a well-designed jet stack system used on a conventional

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 ca ...

, while recovering about at METO (maximum continuous except for take-off) power. In the case of the R-3350, maintenance crews sometimes nicknamed the turbine the ''parts recovery turbine'' due to its negative effect on engine reliability. Turbo-compound versions of the

Napier Deltic The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disp ...

Rolls-Royce Griffon The Rolls-Royce Griffon is a British 37-litre (2,240 cu in) capacity, 60-degree V-12, liquid-cooled aero engine designed and built by Rolls-Royce Limited. In keeping with company convention, the Griffon was named after a bird of prey, ...

, and

Allison V-1710 The Allison V-1710 aircraft engine designed and produced by the Allison Engine Company was the only US-developed V-12 liquid-cooled engine to see service during World War II. Versions with a turbocharger gave excellent performance at high a ...

were constructed but none was developed beyond the prototype stage. It was realized in many cases the power produced by the simple turbine was approaching that of the enormously complex and maintenance-intensive piston engine to which it was attached. As a result, turbo-compound aero engines were soon supplanted by

turboprop A turboprop is a turbine engine that drives an aircraft propeller. A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. Fuel ...

and

engines. Some modern heavy truck diesel manufacturers have incorporated turbo-compounding into their designs. Examples include the

Detroit Diesel Detroit Diesel Corporation (DDC) is an American diesel engine manufacturer headquartered in Detroit, Michigan, United States. It is a subsidiary of Daimler Truck North America, which is itself a wholly owned subsidiary of the mulitinational Da ...

DD15 and

Scania Scania, also known by its native name of Skåne (, ), is the southernmost of the historical provinces of Sweden, provinces (''landskap'') of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conte ...

in production from 1991. Starting with the 2014 season,

Formula 1 Formula One (also known as Formula 1 or F1) is the highest class of international racing for open-wheel single-seater formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Drivers' Championship, ...

switched to a new 1.6 liter turbocharged V6

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

that uses turbo-compounding. The engines use a single turbocharger that is connected to an electric motor/generator called the MGU-H. The MGU-H uses a turbine to drive a generator, converting waste heat from the exhaust into electrical energy that is either stored in a battery or sent directly to an electric motor in the car's powertrain.

List of types

** DD15 * Napier **

Wright Aeronautical Wright Aeronautical (1919–1929) was an American aircraft manufacturer headquartered in Paterson, New Jersey. It was the successor corporation to Wright-Martin. It built aircraft and was a supplier of aircraft engines to other builders in the g ...

: The turbo-compound version was the only turbo-compound

aero-engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...

to see mass production and widespread usage. * Dobrynin **

Dobrynin VD-4K The Dobrynin VD-4K was a Soviet six-bank, 24-cylinder, turbo-compound, inline engine developed after the end of World War II. It was superseded by turboprop engines before it could be widely used. Development The VD-4K, originally designated as t ...

* Zvezda **

Zvezda M503 The Zvezda M503 (built at AO Zvezda at St Petersburg) is a maritime 7 bank, 42 cylinder diesel radial engine built in the 1970s by the Soviet Union. Its primary use was in Soviet missile boats that used three of these engines. This engine ...

: Soviet-built 42 cylinder diesel naval engine used in the

Osa-class missile boat The Project 205 Moskit (''mosquito'') more commonly known by their NATO reporting name Osa, are a class of missile boats developed for the Soviet Navy in the late 1950s. Until 1962 this was classified as a large torpedo boat. The Osa class is ...

Renault Groupe Renault ( , , , also known as the Renault Group in English; legally Renault S.A.) is a French multinational automobile manufacturer established in 1899. The company produces a range of cars and vans, and in the past has manufactured ...

** Renault Energy F1: 1.6 liter turbocharged V6 engine built for Formula 1. Unlike its contemporaries, still uses a wastegate as an emergency measure to control boost pressure in case the turbo-compounding with the MGU-H fails. *

Ferrari Ferrari S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari (1898–1988) in 1939 from the Alfa Romeo racing division as ''Auto Avio Costruzioni'', the company built its first car in ...

** Ferrari 059: 1.6 liter turbocharged V6 engine built for Formula 1 for the Ferrari F14 T as well as the

Sauber C33 The Sauber C33 is a Formula One racing car designed by Sauber to compete in the 2014 Formula One season. It was driven by Esteban Gutiérrez and Adrian Sutil, who joined the team after Nico Hülkenberg returned to Force India. The C33 was design ...

. *

Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...

** Mercedes PU106: 1.6 liter turbocharged V6 engine built for Mercedes-Benz Formula 1 programme. *

Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda has been the world's largest motorcycle manufacturer since 1959, reaching a product ...

** Honda RA615H: 1.6 liter turbocharged V6 engine built for Formula 1 for the

McLaren MP4-30 The McLaren MP4-30 was a Formula One auto racing, racing car designed by Tim Goss and Neil Oatley for McLaren to compete in the 2015 Formula One season. The car was driven by and List of Formula One World Drivers' Champions, World Drivers' C ...

References

{{DEFAULTSORT:Turbo-Compound Engine Turbo-compound engines Turbochargers Engine technology Internal combustion engine Piston engines

Concept

History

List of types

See also

References