Back pressure
Encyclopedia
Back pressure refers to the resistance to a moving fluid
by obstructions or tight bends in the confinement vessel along which it is moving, such as piping or air vents, against its direction of flow.
Because it is really resistance, the term back pressure is misleading as the pressure remains and causes flow in the same direction, but the flow is reduced due to resistance. For example, an automotive exhaust muffler
with a particularly high number of twists, bends, turns and right angles could be described as having particularly high back pressure .
Back pressure, in the exhaust sense of the term, of a four-stroke engine is usually termed as being a "bad thing" for performance; however, in the interest of reducing exhaust sound to levels allowable by public noise ordinances, back pressure can be regulated using systems from simple butterfly valve
s to fully computer controlled units sensing pressure in the exhaust pipe itself.
In a two-stroke engine however, a certain amount of exhaust backpressure is needed to prevent unburned fuel/air mixture from passing right through the cylinders into the exhaust.
to describe the build-up of data
behind an I/O switch if the buffer
s are full and incapable of receiving any more data; the transmitting device halts the sending of data packets until the buffers have been emptied and are once more capable of storing information . It also refers to an algorithm for routing data according to congestion
gradients, see Backpressure Routing
.
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
by obstructions or tight bends in the confinement vessel along which it is moving, such as piping or air vents, against its direction of flow.
Because it is really resistance, the term back pressure is misleading as the pressure remains and causes flow in the same direction, but the flow is reduced due to resistance. For example, an automotive exhaust muffler
Muffler
A muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. A US Patent for an Exhaust muffler for engines was granted to Milton and Marshall Reeves in 1897....
with a particularly high number of twists, bends, turns and right angles could be described as having particularly high back pressure .
Back pressure, in the exhaust sense of the term, of a four-stroke engine is usually termed as being a "bad thing" for performance; however, in the interest of reducing exhaust sound to levels allowable by public noise ordinances, back pressure can be regulated using systems from simple butterfly valve
Butterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve...
s to fully computer controlled units sensing pressure in the exhaust pipe itself.
In a two-stroke engine however, a certain amount of exhaust backpressure is needed to prevent unburned fuel/air mixture from passing right through the cylinders into the exhaust.
See also
- Engine tuningEngine tuningEngine tuning is the adjustment, modification or design of internal combustion engines to yield optimal performance, to increase an engine's power output, economy, or durability....
- Exhaust pulse pressure chargingExhaust pulse pressure chargingExhaust pulse pressure charging is a system for supercharging two-stroke diesel engines of the loop-scavenge type. Loop-scavenge engines cannot be pressure-charged in the same way as uniflow engines or four-stroke engines because the inlet and exhaust ports are open at the same time.-Overview:The...
- Tuned pipeTuned pipeA tuned pipe is a part of a two-stroke engine's exhaust system.It should be distinguished from a muffler as a tuned exhaust pipe does more than muffling the sound...
- Backpressure RoutingBackpressure RoutingThis article describes backpressure routing forqueueing networks. It shows how the algorithm is derived and how its optimality is establishedusing concepts of Lyapunov drift....
Back pressure in information technology
The term is also used analogously in the field of information technologyInformation technology
Information technology is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications...
to describe the build-up of data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
behind an I/O switch if the buffer
Buffer (computer science)
In computer science, a buffer is a region of a physical memory storage used to temporarily hold data while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device or just before it is sent to an output device...
s are full and incapable of receiving any more data; the transmitting device halts the sending of data packets until the buffers have been emptied and are once more capable of storing information . It also refers to an algorithm for routing data according to congestion
gradients, see Backpressure Routing
Backpressure Routing
This article describes backpressure routing forqueueing networks. It shows how the algorithm is derived and how its optimality is establishedusing concepts of Lyapunov drift....
.