Centrifugal-type supercharger

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A centrifugal supercharger is a specialized type of supercharger that makes use of centrifugal force in order to increase the manifold air pressure, MAP. An increased MAP allows the engine to burn more fuel, which results in an increased power output. Centrifugal superchargers are generally attached to the front of the engine via a belt-drive or gear-drive from the engine's crankshaft.

Contents

Types of centrifugal superchargers

The centrifugal supercharger is used in many applications including, but not limited to, automotive, truck, marine, aircraft, motorcycles and UTV's. Of these applications, they are most commonly utilized for increasing horsepower in street vehicles and race applications. While the first practical centrifugal compressor was designed in 1899, [1] centrifugal superchargers evolved during World War II with their use in aircraft, where they were frequently paired with their exhaust driven counterpart, the turbocharger. [2] This term refers to the fact that turbochargers are a specific type of centrifugal supercharger, one that is driven by a turbine.

Lately[ when? ], centrifugal superchargers have become very common in today's performance automotive world. [3] Superchargers are sometimes installed as original equipment on some vehicles manufactured today. Centrifugal supercharging creates an efficient, compact and intercooler friendly means to boost horsepower in both gasoline and diesel engines for a wide variety of watercraft, land craft and aircraft.

Automotive superchargers

Centrifugal superchargers have become popular in the aftermarket as a bolt-on addition to improve performance. [4] By design, centrifugal superchargers allow for easy integration of air-to-air or air-to-water intercooling. [5] Several companies build centrifugal superchargers and also offer them as complete systems which can be easily installed by a mechanic or the auto enthusiast at home.

Aircraft superchargers

Because air pressure decreases with altitude, air compression helps maintain engine power as the aircraft climbs.

Standard functionality

Components

Centrifugal supercharger components ATI ProCharger Supercharger Cutaway.jpg
Centrifugal supercharger components

The four main components of a centrifugal supercharger are the volute (compressor housing), diffuser, impeller and transmission. Volutes are typically cast into a form from aluminum rather than other metals due to the combination of strength, weight, and resistance to corrosion. Volutes are then precision machined to match the impeller design. [6] Impellers are designed in many configurations, and Euler's pump and turbine equation plays an important role in understanding impeller performance. [7] Impellers are often formed by casting metals into a form and then machined, with the highest quality impellers machined from solid billet.

The transmission provides a step-up ratio from the input shaft (driven from the engine crankshaft) to the output shaft, to which the impeller attaches (it is not uncommon for centrifugal supercharger impeller speeds to exceed 100,000 rotations per minute). The basic components of the gear drive centrifugal transmission are shafts, gears, bearings, and seals. Because of the high speeds and loads the transmission must endure, components are machined, ground and assembled to extremely close tolerances.

Process

The centrifugal supercharger draws its power from the movement of the drive where it is attached. At this point, the supercharger powers an impeller – or small rotating wheel. The impeller draws air into a small compressor housing (volute) and centrifugal force sends the air into the diffuser. The result is air that is highly pressurized, but that travels at low speed. [8] The high-pressure, low-speed air is then fed into the engine, where the additional pressure gives the engine the ability to burn more fuel and have a higher level of combustion. This results in a faster, more responsive vehicle due to greater engine volumetric efficiency.

Uses for centrifugal-type superchargers

Personal/recreational

Beyond the use in aircraft which drove many improvements in centrifugal design, more widespread use of the centrifugal supercharger has been heavily focused on the automotive performance aftermarket. [9]

Improvements in design and machining technology have allowed for major advancements in compressor efficiency, as well as bearing and seal design. As a reliable, safe and affordable (dollar per horsepower) option to increase the performance of cars, truck, boats, motorcycles and UTV's, centrifugal supercharging has become a viable option for performance enthusiasts in a variety of applications. Due to the ease of installation, and the fact that many systems utilize integrated intercooling, centrifugal supercharging continues to gain popularity within the performance industry.

Commercial

Centrifugal supercharger technology has also found its way into industrial applications. From wastewater treatment to aircraft deicing, air compression from a centrifugal supercharger has significantly improved the efficiency and reliability of the overall system. In many industries, pneumatic conveying is now the preferred method for moving product or media within a facility. Traditionally the only source for air flow of this volume was considered to be a Roots style compressor. Due to its efficient design, centrifugal technology is now being embraced because it offers substantial energy savings, lower discharge air temperatures and quieter operation. [10]

Benefits of centrifugal-type superchargers

Performance

Engine driven Centrifugal superchargers are inferior to Roots-type superchargers in building torque low in the RPM range but superior to Roots-type superchargers in thermodynamic efficiency (less heat is generated when compressing the air).

Adiabatic efficiency

Because centrifugal superchargers utilize centrifugal forces to compress the air, they offer higher efficiency than positive displacement designs, both in terms of power consumption and heat production. "Perhaps the simplest of all superchargers, the centrifugal can also be the most thermally efficient". [11] The compressor-side of turbochargers are centrifugal designs as well, and also feature high efficiency.

Minimal heat transfer

Centrifugal superchargers are typically mounted off to the side on the front of the engine. Distancing the supercharger from the engine via a mounting bracket greatly reduces heat transfer from the engine to the supercharger during operation. By comparison, a twin screw or roots blower which is nested in the center (valley) of the engine, will absorb heat (heat soak) during operation due to thermal transfer from the engine block and heads. Elevated temperature levels in the supercharger directly influence discharge air temperatures that next enter the engine. Higher engine inlet air temperatures result in reduced power increases and an increased likelihood of engine damage resulting from detonation within the cylinders. See also intercooling (charge-air density increase).

Related Research Articles

<span class="mw-page-title-main">Turbocharger</span> Exhaust-powered forced-induction device for engines

In an internal combustion engine, a turbocharger is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the engine in order to produce more power for a given displacement.

<span class="mw-page-title-main">Gas turbine</span> Type of internal and continuous combustion engine

A gas turbine, gas turbine engine, or also known by its old name internal combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part and are, in the direction of flow:

<span class="mw-page-title-main">Miller cycle</span> Thermodynamic cycle

In engineering, the Miller cycle is a thermodynamic cycle used in a type of internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, U.S. patent 2,817,322 dated Dec 24, 1957. The engine may be two- or four-stroke and may be run on diesel fuel, gases, or dual fuel. It uses a supercharger or a turbocharger to offset the performance loss of the Atkinson cycle.

<span class="mw-page-title-main">Four-stroke engine</span> Internal combustion engine type

A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:

  1. Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
  2. Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
  3. Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
  4. Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.
<span class="mw-page-title-main">Intercooler</span> Heat exchanger used to cool a gas after compression

An intercooler is a heat exchanger used to cool a gas after compression. Often found in turbocharged engines, intercoolers are also used in air compressors, air conditioners, refrigeration and gas turbines.

<span class="mw-page-title-main">Roots blower</span> A positive displacement lobe pump

The Roots blower is a positive displacement lobe pump which operates by pumping a fluid with a pair of meshing lobes resembling a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust.

<span class="mw-page-title-main">Centrifugal compressor</span> Sub-class of dynamic axisymmetric work-absorbing turbomachinery

Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.

<span class="mw-page-title-main">Compressor</span> Machine to increase pressure of gas by reducing its volume

A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.

<span class="mw-page-title-main">Naturally aspirated engine</span> Type of internal combustion engine

A naturally aspirated engine, also known as a normally aspirated engine, and abbreviated to N/A or NA, is an internal combustion engine in which air intake depends solely on atmospheric pressure and does not have forced induction through a turbocharger or a supercharger.

<span class="mw-page-title-main">Forced induction</span> Concept in engine design

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.

<span class="mw-page-title-main">Impeller</span> Rotor used to increase (or decrease in case of turbines) the pressure and flow of a fluid or gas

An impeller, or impellor, is a driven rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.

<span class="mw-page-title-main">Turbomachinery</span> Machine for exchanging energy with a fluid

Turbomachinery, in mechanical engineering, describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid. It is an important application of fluid mechanics.

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 compressor. A map is created from compressor rig test results or predicted by a special computer program. Alternatively the map of a similar compressor can be suitably scaled. This article is an overview of compressor maps and their different applications and also has detailed explanations of maps for a fan and intermediate and high-pressure compressors from a three-shaft aero-engine as specific examples.

A twincharger refers to a compound forced induction system used on some internal combustion engines. It is a combination of an exhaust-driven turbocharger and a mechanically driven supercharger, each mitigating the weaknesses of the other.

<span class="mw-page-title-main">Rotary-screw compressor</span> Gas compressor using a rotary positive-displacement mechanism

A rotary-screw compressor is a type of gas compressor, such as an air compressor, that uses a rotary-type positive-displacement mechanism. These compressors are common in industrial applications and replace more traditional piston compressors where larger volumes of compressed gas are needed, e.g. for large refrigeration cycles such as chillers, or for compressed air systems to operate air-driven tools such as jackhammers and impact wrenches. For smaller rotor sizes the inherent leakage in the rotors becomes much more significant, leading to this type of mechanism being less suitable for smaller compressors than piston compressors.

<span class="mw-page-title-main">Supercharger</span> Air compressor for an internal combustion engine

In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement.

<span class="mw-page-title-main">Pressure wave supercharger</span>

A pressure wave supercharger is a type of supercharger technology that harnesses the pressure waves produced by an internal combustion engine exhaust gas pulses to compress the intake air. Its automotive use is not widespread; the most widely used example is the Comprex, developed by Brown Boveri.

<span class="mw-page-title-main">Two-stroke diesel engine</span> Engine type

A two-stroke diesel engine is a diesel engine that uses compression ignition in a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899.

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 the engine intake system, the air becomes more dense, and is matched with more fuel, producing the increased horsepower to the wheels.

<span class="mw-page-title-main">ProCharger</span>

ProCharger is the automotive supercharger division of Accessible Technologies, Inc. (ATI), a manufacturer of centrifugal compressor technology in multiple industries, located in the Kansas City metropolitan area. Inovair is the name of the company’s industrial products division.

References

  1. ↑ ["The Turbosupercharger", S.A.E. Journal, October 1931]
  2. ↑ Powell, H. (June 1941). "He Harnessed a Tornado..." Popular Science. Bonnier Corporation. p. 67.
  3. ↑ [Gilles, T. (2012). Automotive Service?: Inspection, Maintenance, Repair. Clifton Park, NY: Delmar, Cengage Learning.]
  4. ↑ [Campisano, Jim (2001) "Mustang Performance Engine Tuning", p. 178]
  5. ↑ [Corky Bell, Supercharged! Page 108]
  6. ↑ Centrifugal Superchargers http://www.procharger.com/centrifugalsupercharger.shtml
  7. ↑ [Japikse, David. Centrifugal Compressor Design and Performance.]
  8. ↑ [Aungier, Ronald H. (2000). Centrifugal Compressors, A Strategy for Aerodynamic Design and Analysis.]
  9. ↑ [Truckin’ Custom Pickup Handbook. (2005). St Paul, MN: Motorbooks International.]
  10. ↑ [Evaluation of Energy Conservation Measures for Wastewater Treatment Facilities, United States Environmental Protection Agency, September 2010, EPA 832?R?10?005]
  11. ↑ [Corky Bell, Supercharged! Page 67]
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