Plenum chamber

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A plenum chamber is a pressurised housing containing a fluid (typically air) at positive pressure. One of its functions is to equalise pressure for more even distribution, compensating for irregular supply or demand. It is typically relatively large in volume and thus has relatively low velocity compared to the system's other components. In wind tunnels, rockets, and many flow applications, it is a chamber upstream on the fluid flow where the fluid initially resides (approximately at rest). It can also work as an acoustic silencer.

Contents

Examples

Examples of plenum chambers include those used with:

Etymology

Schoolroom ventilation on the plenum system N&AMOV - School - clean.png
Schoolroom ventilation on the plenum system

The term "plenum" was coined in the 1670s, derived from Latin adjective plenus ("filled, full"). The usage originates from classical theories of physics and the notion that "nature abhors a vacuum". These gave rise to the notion of 17th century 'plenum' as the opposite of vacuum, and all things "being either Plenum or Vacuum". [2]

By the 19th century, the development of mechanical fans and industrial machinery had provided another, more technical use. This referred to "a system of artificial ventilation", [2] which used a pressure raised slightly above atmospheric pressure, in contrast to the "vacuum system" which used a pressure below atmospheric. At a time when high pressure steam or hydraulic systems were well established, these were a distinct set of systems based on low pressure and high volume flows.

Supercharging

V12 engine (non-supercharged), showing plenum chamber 2001 Ferrari 550 engine.jpg
V12 engine (non-supercharged), showing plenum chamber

Supercharged piston engines typically use many cylinders arranged in-line and one or two superchargers. Superchargers deliver air at a relatively constant rate, while cylinders demand it in a varying manner, as the valves open and as piston speed varies through the stroke. Simple direct ducting would give problems where the nearest cylinders received more airflow. The pulsating demand from the cylinders would also show problems of either pressure waves in the duct, or a shortage of inlet air towards the end of the inlet phase.

The solution is to provide a large-volume plenum chamber between the inlet and the cylinders. This has two benefits: it evens out the difference in path restriction between cylinders (distribution across space), secondly it provides a large-volume buffer against pressure changes (distribution over time).

For non-supercharged / normally aspirated engines see Airbox.

Norton Classic

Norton Classic with twin-rotor Wankel engine MyPicClassic.jpg
Norton Classic with twin-rotor Wankel engine

The Norton Classic was a motorcycle whose air-cooled twin-rotor Wankel engine was developed by David Garside at BSA. [3] [4] Wankel engines run very hot, so Garside gave this air-cooled motor additional interior air-cooling. Air was drawn through a forward-facing filter situated to provide a ram air effect. This air passed through the interior of the rotors and then into a large pressed-steel plenum before entering the combustion chambers via twin carburettors. [5] The plenum (which doubled as the bike's semi-monocoque frame) enabled the transfer of much of the heat to the surrounding atmosphere. The carburation process further reduced temperatures via the heat of evaporation. Even so, at 50 °C the fuel-air mixture was still hotter than ideal, and the engine's volumetric efficiency remained somewhat impaired. The eccentric shaft's main bearings and the inlet manifolds were fed by oil-injection lubrication, and the fuel-air mix also carried residual mist of oil from the interior of the rotors, which helped to lubricate the rotor tips. [6]

Hovercraft

Hovercraft schematic Hovercraft - scheme.svg
Hovercraft schematic

Practical hovercraft use a peripheral skirt system, where the air from the lift fans is routed to a narrow slot around the edge of the hull, and bound by a flexible skirt. Distribution of this air from the fans to the periphery is through a large-volume plenum chamber, so as to provide even distribution of airflow without sensitivity to the length of the direct path.[ citation needed ]

Nuclear Waste burning reactor rods

Molten salts consisting of chlorinated nuclear waste are contained in atomic fission reactor rods. This Alvin M. Weinberg et al design has a liquid fuel instead of a solid fuel. The gas plenum is above the fuel and below a diving bell style vent for the reaction products. This allows for convection currents and fluid flow eliminating the possibility for gas products to build up and rupture as in a light water reactor.

Related Research Articles

<span class="mw-page-title-main">Wankel engine</span> Combustion engine using an eccentric rotary design

The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle, with the sides having less curvature. The rotor spins inside a figure-eight-like epitrochoidal housing, around a fixed-toothed gearing. The midpoint of the rotor moves in a circle around the output shaft, spinning the shaft via a cam.

<span class="mw-page-title-main">Carburetor</span> Component of internal combustion engines which mixes air and fuel in a controlled ratio

A carburetor is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances.

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

A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.

<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. The most common application of the Roots-type blower has been the induction device on two-stroke diesel engines, such as those produced by Detroit Diesel and Electro-Motive Diesel. Roots-type blowers are also used to supercharge four-stroke Otto cycle engines, with the blower being driven from the engine's crankshaft via a toothed or V-belt, a roller chain or a gear train.

Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the equivalent volume of the fresh air drawn into the cylinder during the intake stroke to the volume of the cylinder itself. The term is also used in other engineering contexts, such as hydraulic pumps and electronic components.

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

The Sarich orbital engine is a type of internal combustion engine, invented in 1972 by Ralph Sarich, an engineer from Perth, Australia, which features orbital rather than reciprocating motion of its central piston. It differs from the conceptually similar Wankel engine by using a generally prismatic shaped piston that orbits the axis of the engine, without rotation, rather than the rotating trilobular rotor of the Wankel.

<span class="mw-page-title-main">Inlet manifold</span> Automotive technology

In automotive engineering, an inlet manifold or intake manifold is the part of an engine that supplies the fuel/air mixture to the cylinders. The word manifold comes from the Old English word manigfeald and refers to the multiplying of one (pipe) into many.

<span class="mw-page-title-main">Reed valve</span> Type of check valve

Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face. Modern versions often consist of flexible metal or composite materials.

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<span class="mw-page-title-main">Ram-air intake</span> An intake design which uses air pressure from vehicle motion to increase static air pressure

A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion, or ram pressure, to increase the static air pressure inside of the intake manifold on an internal combustion engine, thus allowing a greater massflow through the engine and hence increasing engine power.

<span class="mw-page-title-main">Intake</span> Opening or structure through which a fluid is admitted into a space or machine

An intake is an opening, structure or system through which a fluid is admitted to a space or machine as a consequence of a pressure differential between the outside and the inside. The pressure difference may be generated on the inside by a mechanism, or on the outside by ram pressure or hydrostatic pressure. Flow rate through the intake depends on pressure difference, fluid properties, and intake geometry.

<span class="mw-page-title-main">Crankcase ventilation system</span> System to relieve pressure in a combustion engines crankcase

A crankcase ventilation system removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source.

<span class="mw-page-title-main">Norton Classic</span> Type of motorcycle

The Norton Classic is a rotary-engined motorcycle built in 1987 by Norton as a special edition of just 100 machines.

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This article briefly describes the components and systems found in jet engines.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

<span class="mw-page-title-main">Bendix-Stromberg pressure carburetor</span>

Of the three types of carburetors used on large, high-performance aircraft engines manufactured in the United States during World War II, the Bendix-Stromberg pressure carburetor was the one most commonly found. The other two carburetor types were manufactured by Chandler Groves and Chandler Evans Control Systems (CECO). Both of these types of carburetors had a relatively large number of internal parts, and in the case of the Holley Carburetor, there were complications in its "variable venturi" design.

The MidWest AE series are lightweight, liquid-cooled, single- and twin-rotor Wankel engines, with dual ignition, designed for light aircraft. They were produced by Mid-West Engines Ltd. at Staverton Airport, Gloucestershire, UK.

<span class="mw-page-title-main">Total-loss oiling system</span> Engine lubrication system

A total-loss oiling system is an engine lubrication system whereby oil is introduced into the engine, and then either burned or ejected overboard. Now rare in four-stroke engines, total loss oiling is still used in many two-stroke engines.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

David W. Garside is an inventor and former project engineer at BSA's Umberslade Hall research facility. He is notable for having developed an air-cooled twin-rotor Wankel motorcycle engine which powered the Norton Classic road bike. Although the Classic was not the first production rotary-engined bike, it was significantly lighter, smoother, more powerful and better-handling than the contemporary Suzuki RE5.

References

  1. Robert O. Woods (April 2005). "Organic Developments". Mechanical Engineering Magazine. Archived from the original on January 15, 2009. Retrieved 2008-07-14.
  2. 1 2 "plenum". Oxford English Dictionary. Vol. VII. 1928. plenum
  3. The Wankel Rotary Engine: A History By John B. Hege page 137, ISBN   978-0-7864-2905-9
  4. Denniss, Tony (1990). "The Norton Rotary" . Retrieved 14 August 2011.
  5. "Cycle World" magazine February 1971
  6. Bill Murray monograph 1985: "The decline of the British motorcycle industry"