Reed valves are a type of

check valve A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have t ...

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 A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...

(

fiberglass Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...

carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...

Applications

Traditional

Reed valves, normally a

leather Leather is a strong, flexible and durable material obtained from the tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffalo, pigs and hogs, ...

flap covering a hole, are amongst the earliest form of automatic flow control for

liquids A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

and

gases Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

. They have been used for thousands of years in

water pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they u ...

s and for hundreds of years in

bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtigh ...

for high-temperature

forge A forge is a type of hearth used for heating metals, or the workplace (smithy) where such a hearth is located. The forge is used by the smith to heat a piece of metal to a temperature at which it becomes easier to shape by forging, or to th ...

s and

musical instruments A musical instrument is a device created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument. A person who pl ...

such as

church organ Carol Williams performing at the United States Military Academy West Point Cadet Chapel.">West_Point_Cadet_Chapel.html" ;"title="United States Military Academy West Point Cadet Chapel">United States Military Academy West Point Cadet Chapel. ...

s and

accordion Accordions (from 19th-century German ''Akkordeon'', from ''Akkord''—"musical chord, concord of sounds") are a family of box-shaped musical instruments of the bellows-driven free-reed aerophone type (producing sound as air flows past a reed ...

s. In nature,

heart valve A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart v ...

s operate in a somewhat similar fashion.

Pumps

Reed valves are used in some reciprocating compressor designs, and in the pumping element of some musical instruments, large and small.

Two-stroke engines

Reed valves are commonly used in high-performance versions of the

two-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...

engine, where they control the fuel-air mixture admitted to the cylinder. As the piston rises in the cylinder a vacuum is created in the crankcase beneath the piston. The resulting pressure differential opens the valve and the fuel-air mixture flows into the crankcase. As the piston descends, it raises the crankcase pressure causing the valve to close to retain the mixture and pressurize it for its eventual transfer through to the

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...

. The Swedish motorcycle company Husqvarna produced a two-stroke, 500 cc displacement single cylinder engine with a reed-valve controlled intake, one of the biggest in using this arrangement. Reed valves in two-stroke engines have been placed in the intake ports and also in controlling the intake to the crankshaft space. Composite materials are preferred in racing engines, especially in

kart racing Kart racing or karting is a road racing variant of motorsport with open-wheel, four-wheeled vehicles known as go-karts or shifter karts. They are usually raced on kart circuit, scaled-down circuits, although some professional kart races are als ...

, because the stiffness of the petals can be easily tuned and they are relatively safe in failure. High-speed impact takes its toll on all reed valves, with metal valves suffering in

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

. The physical inertia of reed valves means that they are not as entirely precise in action as

rotary valve A rotary valve (also called rotary-motion valve) is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rot ...

s, a rotary valve engine may run better than a reed valve engine at a small rpm range but the reed valve engine often runs better over a wider rpm range. More sophisticated designs partly address this by creating multi-stage reeds with smaller, more responsive reeds within larger ones that provide more volume later in the cycle. Nevertheless, current technology favors reed valves almost to the exclusion of rotary valves due to their simplicity and low implementation costs and less rotational mass.

Wankel rotary combustion engines

Yanmar Diesel is a Japanese diesel engine, heavy machinery and agricultural machinery manufacturer founded in Osaka, Japan in 1912. Yanmar manufactures and sells engines used in a wide range of applications, including seagoing vessels, pleasure boats, constr ...

, a Japanese engine maker, was pioneer in introducing reed valves for flow control at intake ports of its small

Wankel engines Wankel may refer to: * Wankel engine, a type of internal combustion engine using an eccentric rotary design instead of reciprocating pistons * Wankel AG, a German company that produces Wankel engines for ultralight aircraft and racing cars People ...

, showing an improvement in torque and performances at low rpm and under partial load of the engine. Toyota discovered the benefits of injecting fresh air into the Wankel RCE exhaust port, and also used a reed valve in prototypes where they tested the SCRE concept (

Stratified Charge A stratified charge engine describes a certain type of internal combustion engine, usually spark ignition (SI) engine that can be used in trucks, automobiles, portable and stationary equipment. The term "stratified charge" refers to the working fl ...

Rotary Engine). However, this kind of intake port arrangement never reached the production line for automobile size RCEs. According to David W. Garside, who developed the Norton line of Wankel-powered motorcycles, data from other RCE producers pointed that reed valves do improve performances at low rpm and under partial load, but reduce the high speed power output of the engine, a feature considered inconvenient for motorcycle engines.

Pulse jets

Reed valves are used in the cheap but inefficient

pulse jet engine 300px, Diagram of a pulsejet A pulsejet engine (or pulse jet) is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically (i.e. it does not need ...

, such as the one used by the

Argus As 014 The Argus As 014 (designated 109-014 by the RLM) was a pulsejet engine used on the German V-1 flying bomb of World War II, and the first model of pulsejet engine placed in mass production. License manufacture of the As 014 was carried out in J ...

engine in the German

V-1 (flying bomb) The V-1 flying bomb (german: Vergeltungswaffe 1 "Vengeance Weapon 1") was an early cruise missile. Its official Reich Aviation Ministry () designation was Fi 103. It was also known to the Allies as the buzz bomb or doodlebug and in Germany as ...

. The valves at the front of the cylindrical engine are opened by the low pressure in the combustion chamber caused by the resonance of the air column in the engine,

fuel 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 ...

is squirted into the combustion chamber and ignited by the hot combustion gases of the previous cycle. Once the charge has expanded and mostly left the engine, pressure inside drops again to below-atmospheric values and the reed valve allows fresh air to enter and the cycle be repeated. Some

ram-air 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 massf ...

pressure due to forward motion helps scavenging and filling the combustion chamber with the new, fresh air charge, thus improving the power of the engine at higher speeds.

Design and modelling

Reed valves are designed considering the

pressure gradient In atmospheric science, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location. The p ...

and

mass flow Mass flow, also known as mass transfer and bulk flow, is the movement of fluids down a pressure or temperature gradient,Moyes & Schulte (2008). Principles of Animal Physiology. Pearson Benjamin Cummings. San Francisco, California particularly in ...

. The pressure gradient is used to evaluate the valve lift during open condition; the lift and overall component geometry (considering also a pressure loss coefficient) are then used to calculate the mass flow. For high speed applications (compressors and engines) the dynamic response has to be considered. A simple approach consists in the evaluation of first

eigenvalue In linear algebra, an eigenvector () or characteristic vector of a linear transformation is a nonzero vector that changes at most by a scalar factor when that linear transformation is applied to it. The corresponding eigenvalue, often denoted b ...

that is compared with exciting frequency. Design of reed valves can be refined using simulations. The dynamic of petals can be studied neglecting the coupling between fluid and structure: in this case the evolution of the structural part are simulated using lumped parameters models or FEM models, discharge coefficients at various valve lift are evaluated with experiments or CFD simulations. The study of the complete system needs an integrated Fluid-structure interaction model.