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Things you need to know about Turbocharged Engines

Have you been Hearing about the high-power input device in an internal combustion engine, well, the secret is the turbocharger. It is also known as a turbo which was invented in the early twentieth century by an engineer in Swiss land, Alfred Buchi. He introduced a prototype to increase the power of diesel engines.

Today, turbocharging has become a standard device for most gasoline and diesel engines. Research is still ongoing on ways to improve the designs of turbochargers for better performance at lower manufacturing cost. Even though vibration-induced stresses and bearing performance are major failure factors. For this reason, a rotodynamic analysis should be an important part of the turbocharger design process, well, maybe!

turbocharged engine

In an automobile engine, power is produced in the combustion chamber with intake fuel/air mixture, right! After the compression, it releases the mixture as exhaust gas which becomes waste products and even cause pollution to the atmosphere. But instead of having the exhaust gas useless, turbocharger makes use of it to make the engine run faster. Let me explain.

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Today we’ll be looking at the definition, functions, applications, parts, history, diagram, types, working principle as well as the advantages and disadvantages of a turbocharger. This article is broad so I urge you to read through to attain the knowledge.

Turbocharger Definition

A turbocharger is a turbine-driven, force induction device that increases the efficiency and power output of internal combustion engines by forcing extra compressed air into the combustion chamber. This hot air induction seems to work because the compressor can force more air and proportionately more fuel into the combustion chamber than normal atmospheric pressure.

A turbocharger is a device fitted to a vehicle’s engine in order to improve the overall efficiency and increase the performance of the engine. turbochargers are originally known as turbosuperchargers because all forced induction devices are classified as superchargers. A supercharger is a term given to a mechanically driven forced induction device.

The difference between a turbocharger and a conventional supercharger is that a turbocharger is powered by a turbine driven by an engine’s exhaust gas. Whereas, a supercharger is mechanically driven by the engine crankshaft, often connected with a belt. However, turbochargers are more efficient but less responsive. The term Twin-charger is referred to an engine with a turbocharger and a supercharger.

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History

A brief history on turbochargers, credit goes to the founder Alfred J Buchi (1879 – 1932) who was employed in an automotive engineer workshop by the Gebruder Sulzer Engine Company of Winterthur, Switzerland. The project was developed a year before the first World War I which was patented in Germany in 1905. He continued the enhancement of the project until his death after four decades.

Some other engineers also deserve to be credited on the turbocharger project. Some years earlier, Sir Dugald Clark (1854 – 1932) was a Scottish inventor of a two-stroke engine. he experimented with separating the compression and expansion stages of internal combustion using two separate cylinders.

His experiment worked like supercharging, increasing both airflows into cylinders and the amount of fuel that could be burned. Other engineers like Louis Renault, Gottlieb Daimler, and Lee Chadwick, also take part in the supercharging systems.

Functions of Turbocharger

The primary function of a turbocharger is to increase the working efficiency of an automobile engine. below are purposes why turbo will always exist despite a few of its limitations.

  • Extra oomph is provided, without increasing the engine capacity.
  • Make the engine run faster without an increase of fuel burning rate.
  • Make use of carbon II oxide (exhaust gas) instead of causing pollution.

turbochargers engine layout

Applications of Turbocharger

A turbocharger is commonly used in automotive engines like truck, car, train, aircraft, and construction equipment. modern release of Otto cycle and diesel cycle internal combustion engines feature turbochargers.

Let dive in to explain some applications of turbochargers:

Gasoline and Diesel-power cars: As earlier mentioned turbocharged cars is common of petrol and diesel-powered cars to increase their power output for a given capacity. It also increases fuel efficiency, allowing a smaller displacement engine. These engines lost weight of about 10% and save up to 30% in fuel consumption and still deliver the same peak horsepower.

The first turbocharged passenger car was the Oldsmobile Jetfire option. It uses the component to a 215 cu in all aluminium V8 and on Chevrolet product called corvairs. It is initially called Monza Spyder cooled flat six-cylinder engine.

Diesel cars vastly rely on turbocharger since the use of improved efficiency, drivability, and performance of diesel engines. It is produced on passenger car was Garrett-turbocharged Mercedes introduced in 1978.

Trucks: For the same benefit, diesel truck engines have featured turbocharging since 1938.

Aircraft: Over the year the effect of turbocharger also increases the efficiency of aeroplanes.

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Motorcycles: Most Japanese companies produced high-performance motorcycles that feature turbocharged since the early 1980s. Although there are few turbocharged motorcycles out there, this is because of an abundance of larger displacement. The naturally aspirated engine being available that offer the torque and power benefits of smaller displacement engine with turbocharger but returns more linear power characteristics.

Read: Components of an internal combustion engine

Parts of Turbochargers

Below are the major parts of a turbocharger and their functions:

  • Cartridges (fully assembled and balanced turbocharger cores)
  • Vacuum actuators and pneumatic actuators
  • Electronic actuators (electric servo drives)
  • Compressor housings (the housings of the turbocharger cold section/part)
  • Turbocharger repair kits (spare part kits/sets for a quick minor repair)
  • Compressor wheels (turbocharger compressor wheels)
  • Shaft and wheels (turbocharger shafts with turbine wheel, turbine rotors)
  • Nozzle Ring Housings (Housings for VNT geometry control elements)
  • Bearing Housings (Cartridge housings, Turbo core housings)
  • Backplates (turbocharger cores plate from compressor side)
  • VNT Nozzle Rings (Rings with nozzles for VNT turbochargers, VNT geometry control nodes)
  • Heat shields (turbocharger core heat shields)
  • Gasket kits(turbocharger gasket kits/sets)
  • Actuator sensors (pressure sensors, position sensors
  • VNT Gaskets (internal gaskets for VNT turbochargers)
  • Turbine housings (the housings of the turbocharger hot section/part)
  • Electronic actuator parts (electric motors, shafts, gears of turbocharger servo drives).

parts of turbocharger

Types of Turbochargers

Below are the various types of turbochargers that exist:

Single turbo:

The single turbo is the simplest, most common and cheapest type of turbocharger that exist. It has limitless variability and being a smaller turbo, it provides better low-end grunt as they spool faster. The single turbo has a ball bearing and journal bearing which provide less friction for the compressor and turbine to spin on.

The benefits of the single turbochargers are that smaller engines are also allowed to feature a turbo, cost-effectiveness is also considered, simplicity and easier to install. It also increases engine efficiency.

Some limitations still occur despite its advantages which includes; having a fair narrow effective rpm range. Single turbos make sizing an issue since one has to choose between better high-end power or good low-end torque. Finally, the response may be slow compare to other turbo types.

Twin Turbos:

The twin-turbo is another option that allows single turbocharger for each cylinder bank (v8, v12 etc.). Alternatively, a single turbocharger could be used for low rpm and bypass to a larger turbocharger for high rpm. Two similar-sized turbos where one is used at low rpm and both are used at higher rpm (14, 16). BMW x5 M and x6 M uses twin-scroll turbos, one on each side of the v8.

The benefit of twin-turbo when it’s sequential or on the turbo at low rpm and both at high rpm. It allows wider, flatter torque curve, better low-end torque, but the power won’t taper at high rpm like a single turbo. Limitations with these turbochargers include cost and complexity, as the component is almost doubled. And, there are other alternatives for achieving a similar result that is lighter.

Read: Difference between gasoline and diesel engine

Twin-Scroll Turbo:

In almost every way, twin-scroll turbochargers are better than single-scroll turbos because while using two scrolls, the exhaust pulses are divided. For instance, in four-cylinder engines having firing order of 1 3 4 2, cylinders 1 and 4 may be feed to one scroll of a turbo. Whereas cylinders 2 and 3 are feed to separate scroll. The purpose of these types of a turbocharger is that there is overlap in the cylinder. Let say cylinder is ending its power stroke as the piston reaches the bottom dead centre, and exhaust valve will open. During this time, cylinder two ends its exhaust stroke by closing the valve and opening the intake valve.

A traditional single-scroll turbo manifold is quite different, the exhaust pressure from cylinder one will interfere with cylinder two pulling in the fresh air because of both exhaust valves ae temporary open. This reduces how much pressure reaches the turbo and interfering with how much air the second cylinder pulls in.

The advantages of the turbocharger are that more energy is sent to the exhaust turbine and wider rpm range of effective boost is attained. This is because of the different scroll designs. Basically, there is more valve overlap without hampering exhaust scavenging, leading to more tuning flexibility.

Limitations is that cost and complexity is high compare to the single turbos and it requires a specific engine layout and exhaust design.

Variable Geometry Turbocharger (VGT):

The variable geometry types of a turbocharger are common on diesel engines and they are limited in production. This is because of its cost and exotic material requirements. Internal vanes within the turbocharger alter the area-to-radius A/R ratio to correspond with the rpm. That is, at a low rpm, a low A/R ratio is used to increase exhaust gas velocity and quickly spool up the turbocharger. If the revs climb, the A/R ratio increases in order to increase the airflow which result in low turbo lag. It also leads to low boost threshold and a wide and smooth torque band.

The benefits of this type of turbo is that wide, flat torque curve is produced. Which is effective at a very wide rpm range. It requires a single turbo, simplifying a sequential turbo setup into something more compact. Its limitations are that it is only used in diesel applications where exhaust gases are lower so the vanes will not be destroyed by the head. Using the turbo on a gasoline engine, high-cost exotic metals will be used in order to maintain reliability.

Variable Twin-Scroll Turbocharger:

The variable twin-scroll turbo is significantly cheaper than VGTs, making it a preferable choice for gasoline turbocharging. It combines a VGT with a twin-scroll setup, thus, at a low revolution, one of the scrolls is completely closed forcing all the air into the other. As the engine speed up, a valve opens to allow air into the other scroll and good high-end performance is obtained.

Advantages of the turbocharger are that it allows a wide, flat torque curve and it’s more robust in design than the VGT. Cost and complexity are also its limitations and technology have been unwanted before.

Electric Turbochargers:

With the application of electric motor in a turbocharger, it enhances its features and provides an instant boost to the engine. Low-end torque is easily produced, lag is eliminated. This turbocharger is just the best of all, perhaps a new version might bring it down.

its benefits are that wider effective rpm range with even torque throughout is produced. Wasted energy is recovered as an electric motor is connected directly to the exhaust turbine. And as mentioned earlier turbo lag and insufficient exhaust gases can be virtually eliminated by rotating the compressor with electric power when needed.

Complexity and cost are one of the disadvantages of the turbocharger as account for the electric motor is now included. Packaging and weight is also an issue, especially with the addition off a battery onboard, which supply sufficient power to the turbo when needed. Similar benefits can be obtained from other types like the VGTs or twin-scrolls.

Working principle

Having a basic knowledge of how a jet engine works, understanding cars with a turbocharger will be much easier. Let me explain, a jet engine sucks fresh air at the front, and use it in the chamber to mix and burn with fuel. It then blasts hot air through its back. The hot roars past a turbine made of a compact metal windmill, which drives the compressor (air pump) at the front of the engine. the engine uses it to pushes air into the engine to make the fuel burn properly.

A similar process is applied to the turbocharger on a car piston engine. exhaust gases are used to drive the turbine, which spins an air compressor that pushes extra air into the cylinders. It causes more fuel to be burned in second which why a turbocharged car can produce more power. That is more energy per second.

Turbochargers are made of two halves joined together by a shaft. One of it contains a turbine that is spin by hot exhaust gases, the other helve also contains a turbine that sucks air in and compresses it into the engine. This compression offers extra power and efficiency to the engine. As more air enters the combustion chamber, more fuel is added which produce extra power.

Note that the compressed air is hot which is less dense and it rises over radiators. This hot air is less effective in helping fuel to burn. Because of this, the air coming from the compressor needs to be cooled before entering the cylinders. This is why the hot air from the compressor passes over a heat exchanger that removes extra heat before it enters into the combustion chamber.

turbocharger operation diagram

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Where the extra power comes from and how much you can get

Most people think turbine engine offers extra power from the received exhaust gas, but that’s not true. The exhaust gas is used to drive the compressor that transfers air to the combustion chamber allowing the engine to burn more fuel each second. The extra power is obtained from the extra fuel that is burned at a faster rate.

The amount of extra power turbocharger gives is determined by how big the components are. Turbochargers can be improving to make the engine more powerful, depending on the much power one desired. But there is a limit of improvement. Cylinders are so large that they can receive much air and fuel to mix.

Advantages and Disadvantages of Turbochargers

Advantages:

Below are the benefits of turbochargers:

  • Extra power is offered to the engine.
  • Free power is given to the engine using waste exhaust gases. it does not require any engine’s power to drive it.
  • It’s used in both diesel and gasoline engines.
  • Improve fuel efficiency of engines.

Disadvantages:

Despite the advantages of turbochargers, two main limitations still occur. Below are the disadvantages of the turbocharger:

One of the big issue with a turbocharger is known as turbo lag. This happened when the throttle is press down, it takes time for the engine to speed up. That’s, turbochargers take time to reflect the engine speed.

When the engine’s speed is low, there are not enough exhaust gasses to spin the compressor to offer the power needed. The required exhaust will be created after the throttle is pressed. This effect is reduced by downshifting to a lower gear but expert drivers sometimes notice the split delay in response.

The second limitation of turbochargers does not occur in everyday driving conditions. It happens only when the engine is pushed to its limits. The heat produced from the exhaust gasses, it gets very hot and causes the turbocharger to start glowing red.

This is why most turbocharged sports cars are designed with vents in at the downside of the engine. This vent keeps air circulation constant and cools the parts.

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In conclusion, we’ve exposed to you the various functions of turbochargers. One of them is to increase the working and fuel efficiency of engines. We also see the various types of turbos and their working principle. Advantages and disadvantages are also revealed.

I hope the knowledge is attained, if so, kindly comment, share and recommend this site to other technical students. Thanks!

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