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 fea ...

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 ...

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 pr ...

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 ma ...

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, as on the Wright R-3350 Duplex-Cyclone, 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, ...

engines. Examples using the Duplex-Cyclone include the Douglas DC-7B 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 produ ...

, 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 hea ...

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 a ...

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 World War II by country, vast majority of the world's countries—including all of the great power ...

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. 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 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 ...

, 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 engine, opposed-piston valveless, supercharged Uniflow scavenging, uniflow scavenged, two-stroke diesel engine used in marine diesel engine, marine and locomotive applications, designed and ...

, Rolls-Royce Crecy,

Rolls-Royce Griffon The Rolls-Royce Griffon is a British 37-litre (2,240 cubic inch, cu in) Engine displacement, capacity, 60-degree V12 engine, V-12, liquid-cooled Aircraft engine, aero engine designed and built by Rolls-Royce Limited. In keeping with compan ...

, 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 hig ...

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. ...

and

engines. Some modern heavy truck diesel manufacturers have incorporated turbo-compounding into their designs. Examples include the Detroit Diesel DD15 and

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

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 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

* Detroit Diesel ** DD15 * Napier ** Napier Nomad *

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 ...

: 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 * 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 ma ...

: 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 i ...

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 manufacture ...

** 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 059: 1.6 liter turbocharged V6 engine built for Formula 1 for the Ferrari F14 T as well as the Sauber C33. *

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 headquarter ...

** 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 producti ...

** Honda RA615H: 1.6 liter turbocharged V6 engine built for Formula 1 for the McLaren MP4-30.

References

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

Concept

History

List of types

See also

References