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.
79-427: 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 Roots blower design does not incorporate any reduction in volume/increase in pressure as air or other fluid passes through, hence it can best be described as
158-430: A centrifugal pump . The fluid enters along the axis or center, is accelerated by the impeller and exits at right angles to the shaft (radially); an example is the centrifugal fan , which is commonly used to implement a vacuum cleaner . Another type of radial-flow pump is a vortex pump. The liquid in them moves in tangential direction around the working wheel. The conversion from the mechanical energy of motor into
237-408: A Roots blower has cycloidal rotors, constructed of alternating tangential sections of hypocycloidal and epicycloidal curves. For a two-lobed rotor, the smaller generating circles are one-quarter the diameter of the larger. Real Roots blowers may have more complex profiles for increased efficiency. The lobes on one rotor will not drive the other rotor with minimal free play in all positions, so that
316-495: A Roots-style blower in a patented engine design, making the Roots-type blower the oldest of the various designs now available. Roots blowers are commonly referred to as air blowers or PD (positive displacement) blowers. The Roots-type blower is simple and widely used. It can be more effective than alternative superchargers at developing positive intake manifold pressure (i.e., above atmospheric pressure) at low engine speeds, making it
395-547: A Roots-type blower; the two companies are not related. The superchargers used on top fuel engines , funny cars , and other dragsters , as well as hot rods , are in fact derivatives of General Motors Coach Division blowers for their industrial diesel engines , which were adapted for automotive use in drag racing . The model name of these units delineates their size - the once-commonly used 4–71 and 6–71 blowers were designed for 71 series diesels. Current competition dragsters use aftermarket GMC variants similar in design to
474-523: A blower rather than a supercharger unlike some other designs of "supercharger" such as cozette, centric, Shorrock supercharger , Powerplus supercharger and also the axial flow Eaton type supercharger which have internal "compression". 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
553-453: A crankshaft-driven roots type supercharger, a turbo supercharger, the engine pistons' undersides, and a supercharger powered by an electric motor. The slide valve for the ram induction effect eventually proved to be prone to failure and was rendered obsolete by increasing supercharging rates in the early 1960s. In the early 1980s, all major two-stroke diesel engine manufacturers switched from reverse flow scavenging to uniflow scavenging, because
632-460: A curved spiral wound around of thickness half x , though in reality it is manufactured in a single casting. This shaft fits inside a heavy-duty rubber sleeve, of wall thickness also typically x . As the shaft rotates, the rotor gradually forces fluid up the rubber sleeve. Such pumps can develop very high pressure at low volumes. Named after the Roots brothers who invented it, this lobe pump displaces
711-417: A free path through the supercharger at certain angles). Accumulated heat is an important consideration in the operation of a compressor in an internal combustion engine . Of the three basic supercharger types, the Roots design historically possessed the worst thermal efficiency , especially at high pressure ratios. In accordance with the ideal gas law , a compression operation will raise the temperature of
790-526: A gentle pumping process ideal for transporting shear-sensitive media. Devised in China as chain pumps over 1000 years ago, these pumps can be made from very simple materials: A rope, a wheel and a pipe are sufficient to make a simple rope pump. Rope pump efficiency has been studied by grassroots organizations and the techniques for making and running them have been continuously improved. Impulse pumps use pressure created by gas (usually air). In some impulse pumps
869-431: A higher flash point and giving them higher energy density . They are therefore easier and safer to handle and occupy less volume for a given amount of energy. Two stroke diesels usually burn even heavier grades of fuel oil than standard diesel fuels . In two-stroke marine diesel engines for sea-going craft, the most common fuels are residue oils . Günter Mau argues that no uniform standards for such fuels exist, which
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#1732855413153948-425: A higher hydraulic-head and lower flow-rate. The device uses the water hammer effect to develop pressure that lifts a portion of the input water that powers the pump to a point higher than where the water started. The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation,
1027-464: A long way to negating the inefficiency of the Roots design in that application. Rotary lobe blowers, commonly called boosters in high vacuum application, are not used as a stand-alone pump. In high vacuum applications, the boosters' pumping speed can be used towards reducing the end pressure and increasing the pumping speed. Fans With a low increase in pressure, fans are commonly used to move substantial quantities of gas. They're typically employed for
1106-442: A low flow rate, the total head rise and high torque associated with this pipe would mean that the starting torque would have to become a function of acceleration for the whole mass of liquid in the pipe system. Two-stroke diesel engine 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. In compression ignition, air
1185-434: A lower temperature of the intake charge results in a greater thermodynamic expansion and vice versa. A hot intake charge provokes detonation in a petrol engine, and can melt the pistons in a diesel, while an intercooling stage adds complexity but can improve the power output by increasing the amount of the input charge, exactly as if the engine were of higher capacity. An intercooler reduces the thermodynamic efficiency by losing
1264-518: A myriad of markets across the world. Triplex pumps with shorter lifetimes are commonplace to the home user. A person who uses a home pressure washer for 10 hours a year may be satisfied with a pump that lasts 100 hours between rebuilds. Industrial-grade or continuous duty triplex pumps on the other end of the quality spectrum may run for as much as 2,080 hours a year. The oil and gas drilling industry uses massive semi-trailer-transported triplex pumps called mud pumps to pump drilling mud , which cools
1343-405: A popular choice for passenger automobile applications. Peak torque can be achieved by about 2000 rpm. Unlike the basic illustration, most modern Roots-type superchargers incorporate three-lobe or four-lobe rotors; this allows the lobes to have a slight twist along the rotor axes, which reduces pulsing in the input and output (this is impractical with two lobes, as even a slight twist could open up
1422-574: A pulsation damper. The increase in moving parts and crankshaft load is one drawback. Car washes often use these triplex-style plunger pumps (perhaps without pulsation dampers). In 1968, William Bruggeman reduced the size of the triplex pump and increased the lifespan so that car washes could use equipment with smaller footprints. Durable high-pressure seals, low-pressure seals and oil seals, hardened crankshafts, hardened connecting rods, thick ceramic plungers and heavier duty ball and roller bearings improve reliability in triplex pumps. Triplex pumps now are in
1501-531: A rated power of 12,400 PS (9,120 kW; 12,230 hp). MAN moved their two-stroke diesel engine department from Nürnberg to Augsburg in 1919. By 1939, several two-stroke diesel types were in widespread use, and others were being developed for high-power applications,. Of several two-stroke aircraft diesel engine concepts, the Junkers Jumo 205 was the only type to be made in significant quantities, with approximately 900 units in all. Introduced in 1939,
1580-477: A return line back to the suction line or supply tank, provides increased safety . A positive-displacement pump can be further classified according to the mechanism used to move the fluid: These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid. Advantages: Rotary pumps are very efficient because they can handle highly viscous fluids with higher flow rates as viscosity increases. Drawbacks: The nature of
1659-467: A roots type supercharger which is a positive displacement pump "blower" with no internal volume reduction/pressure increase, and other types of supercharger such as the eccentric vane powerplus and the Eaton axial flow which have internal compression and are more correctly described as superchargers. Conversely, a turbocharger , using exhaust compression to spin its turbine, and not a direct mechanical link,
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#17328554131531738-589: A second unit placed near the front of the vehicle where a fan and the ambient air-stream can dissipate the collected heat. The Roots design was commonly used on two-stroke diesel engines (popularized by the Detroit Diesel [truck and bus] and Electro-Motive [railroad] divisions of General Motors), which require some form of forced induction , because there is no separate intake stroke. The Rootes Co . two-stroke diesel engine, used in Commer and Karrier vehicles, had
1817-491: A separate pair of gears provide the phasing of the lobes. Because rotary lobe pumps need to maintain a clearance between the lobes, a single stage Roots blower can pump gas across only a limited pressure differential. If the pump is used beyond its specification, the compression of the gas generates enough heat so that the lobes expand to the point that they jam, damaging the pump. Roots pumps are capable of pumping large volumes but, as they only achieve moderate compression, it
1896-414: A slight increase in internal leakage as the pressure increases prevents a truly constant flow rate. A positive-displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive-displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until
1975-400: A smaller blower with a larger blower moves the point to the left. In most cases, as the map shows, this will move it into higher efficiency areas on the left as the smaller blower likely will have been running fast on the right of the chart. Usually, using a larger blower and running it slower to achieve the same boost will give an increase in compressor efficiency. The volumetric efficiency of
2054-425: Is a more complicated type of rotary pump that uses two or three screws with opposing thread — e.g., one screw turns clockwise and the other counterclockwise. The screws are mounted on parallel shafts that often have gears that mesh so the shafts turn together and everything stays in place. In some cases the driven screw drives the secondary screw, without gears, often using the fluid to limit abrasion. The screws turn on
2133-400: Is a type of positive-displacement pump. It contains fluid within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A number of rollers , shoes , or wipers attached to a rotor compress the flexible tube. As the rotor turns, the part of the tube under compression closes (or occludes ), forcing the fluid through the tube. Additionally, when
2212-405: Is commonly used to define a device placed on engines with a functional need for additional airflow using a direct mechanical link as its energy source. The term blower is used to describe different types of superchargers. A screw type supercharger , Roots-type supercharger, and a centrifugal supercharger are all types of what are commonly described as blowers, however there is a distinction between
2291-448: Is first compressed and heated; fuel is then injected into the cylinder, causing it to self-ignite . This delivers a power stroke each time the piston rises and falls, without any need for the additional exhaust and induction strokes of the four-stroke cycle. According to the engineer who drew up Rudolf Diesel ‘s design for of the first operational diesel engine , Motor 250/400 , Imanuel Lauster , Diesel did not originally intend using
2370-479: Is given in terms of pressure ratio, which is the ratio of absolute air pressure before the blower to the absolute air pressure after compression by the blower. If no boost is present, the pressure ratio will be 1.0 (meaning 1:1), as the outlet pressure equals the inlet pressure. 15psi boost is marked for reference (slightly above a pressure ratio of 2.0 compared to atmospheric pressure). At 15 psi (100 kPa) boost, Roots blowers hover between 50% and 58%. Replacing
2449-414: Is how they operate under closed valve conditions. Positive-displacement pumps physically displace fluid, so closing a valve downstream of a positive-displacement pump produces a continual pressure build up that can cause mechanical failure of pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time). Such a pump is also referred to as
Roots blower - Misplaced Pages Continue
2528-575: Is in pneumatic conveying systems, the blower delivering a high volume of air for the movement of bulk solids through pipes. Some civil defense sirens used Roots blowers to pump air to the rotor (chopper) so as to drastically increase its sound output through all pitch ranges. The most well known are the Federal Signal Thunderbolt Series , and ACA (now American Signal Corporation) Hurricane. These sirens are known as "supercharged sirens". Roots blowers are also used in reverse to measure
2607-493: Is not generally regarded as a "blower" but simply a "turbo". Pump#Positive-displacement pumps Mechanical pumps serve in a wide range of applications such as pumping water from wells , aquarium filtering , pond filtering and aeration , in the car industry for water-cooling and fuel injection , in the energy industry for pumping oil and natural gas or for operating cooling towers and other components of heating, ventilation and air conditioning systems. In
2686-412: Is not uncommon to see multiple Roots blower stages, frequently with heat exchangers ( intercoolers ) in between to cool the gas. The lack of oil on the pumping surfaces allows the pumps to work in environments where contamination control is important. The high pumping rate for hydrocarbons allows the Roots pump to provide an effective isolation between oiled pumps , such as rotary compression pumps , and
2765-435: Is passed through it. This causes an electromagnetic force that moves the liquid. Applications include pumping molten solder in many wave soldering machines, pumping liquid-metal coolant, and magnetohydrodynamic drive . A positive-displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive-displacement pumps use an expanding cavity on
2844-402: Is the simplest form of rotary positive-displacement pumps. It consists of two meshed gears that rotate in a closely fitted casing. The tooth spaces trap fluid and force it around the outer periphery. The fluid does not travel back on the meshed part, because the teeth mesh closely in the center. Gear pumps see wide use in car engine oil pumps and in various hydraulic power packs . A screw pump
2923-500: The Superior Air Parts Gemini Diesel 100 under development as of 2015. The defining characteristic of the diesel engine is that it relies on compression ignition . As air is compressed it heats up. Fuel is then injected into the hot, compressed air and ignites spontaneously. This allows it to operate with a lean mixture comprising mainly air. Together with the high compression ratio, this makes it more economical than
3002-440: The medical industry , pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heart and penile prosthesis . When a pump contains two or more pump mechanisms with fluid being directed to flow through them in series, it is called a multi-stage pump . Terms such as two-stage or double-stage may be used to specifically describe
3081-539: The potential energy of flow comes by means of multiple whirls, which are excited by the impeller in the working channel of the pump. Generally, a radial-flow pump operates at higher pressures and lower flow rates than an axial- or a mixed-flow pump. These are also referred to as all-fluid pumps . The fluid is pushed outward or inward to move fluid axially. They operate at much lower pressures and higher flow rates than radial-flow (centrifugal) pumps. Axial-flow pumps cannot be run up to speed without special precaution. If at
3160-446: The 71 series, but with the rotor and case length increased for added capacity; hot rodders also use reproduction 6-71s. Roots blowers are typically used in applications where a large volume of air must be moved across a relatively small pressure differential. This includes low vacuum applications, with the Roots blower acting alone, or in combination with other pumps as part of a high vacuum system. One very common industrial application
3239-443: The Roots-type blower is very good, usually staying above 90% at all but the lowest blower speeds. Because of that, a blower running at low efficiency will still mechanically deliver the intended volume of air to the engine, but that air will be hotter. In drag racing applications, where large volumes of fuel are injected with that hot air, vaporizing the fuel absorbs the heat. That functions as a kind of liquid aftercooler system and goes
Roots blower - Misplaced Pages Continue
3318-515: The blower being driven from the engine's crankshaft via a toothed or V-belt , a roller chain or a gear train . The Roots-type blower is named after American inventors and brothers Philander and Francis Marion Roots , founders of the Roots Blower Company of Connersville, Indiana , who patented the basic design in 1860 as an air pump for use in blast furnaces and other industrial applications. In 1900, Gottlieb Daimler included
3397-453: The circulation of air in buildings, machine ventilation, cooling equipment and other industrial applications. Blowers Blowers are capable of creating medium air pressure with moderate pressure levels. They are used in applications where the pressure need is higher than fans. Compressors Compressors generate higher air pressures in industrial applications generally between 8 and 12 bars with less amount of air flow rates. The term "blower"
3476-416: The compressed output. Additionally, the operation of the compressor itself requires energy input, which is converted to heat and can be transferred to the gas through the compressor housing, heating it more. Although intercoolers are more commonly known for their use on turbochargers , superchargers may also benefit from the use of an intercooler. Internal combustion is based upon a thermodynamic cycle , and
3555-404: The crank shaft, whereas in a four-stroke engine they take two complete revolutions. Consequently, in the two-stroke cycle the stages overlap through most of the engine's operation. This makes its thermodynamic and aerodynamic processes more complex. Because the four-stroke cylinder fires only every other revolution, the power output of the two-stroke cycle is theoretically twice as much. However,
3634-485: The crankshaft. The remaining, adjustable, parameters have to do with exhaust valve and injection timing (these two parameters are not necessarily symmetrical about TDC or, for that matter, BDC), they are established to maximize combustion gas exhaust and to maximize charge air intake. A single camshaft operates the poppet-type exhaust valves and the Unit injector , using three lobes: two lobes for exhaust valves (either two valves on
3713-491: The design concept had first been proposed in 1914. The design was license-manufactured in several countries. Subsequent advances in petrol fuel injection technology rendered the two-stroke aircraft engine obsolete. Although the Napier Culverin , a licensed version of the larger Jumo 204 , was not put into production, the later Napier Deltic incorporated a redesigned triangular arrangement with three cylinders per bank, and
3792-686: The desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the chamber pressure and the inward pressure of the plunger will then open the discharge valve and release the fluid into the delivery pipe at constant flow rate and increased pressure. Pumps in this category range from simplex , with one cylinder, to in some cases quad (four) cylinders, or more. Many reciprocating-type pumps are duplex (two) or triplex (three) cylinder. They can be either single-acting with suction during one direction of piston motion and discharge on
3871-407: The direction of flow of the fluid changes by ninety degrees as it flows over an impeller, while in axial flow pumps the direction of flow is unchanged. An electromagnetic pump is a pump that moves liquid metal , molten salt , brine , or other electrically conductive liquid using electromagnetism . A magnetic field is set at right angles to the direction the liquid moves in, and a current
3950-478: The drill bit and carries the cuttings back to the surface. Drillers use triplex or even quintuplex pumps to inject water and solvents deep into shale in the extraction process called fracking . Typically run on electricity compressed air, these pumps are relatively inexpensive and can perform a wide variety of duties, from pumping air into an aquarium , to liquids through a filter press . Double-diaphragm pumps can handle viscous fluids and abrasive materials with
4029-425: The first time. However, with its actual power output of only 6.95 PS (5 kW; 7 hp) and high fuel consumption of 380 g·PS ·h (517 g·kW ·h ), it did not prove to be successful; Güldner's two-stroke diesel engine project was abandoned in 1901. In 1908, MAN Nürnberg offered single-acting piston two-stroke diesel engines for marine use, the first double-acting piston engine from MAN Nürnberg
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#17328554131534108-482: The flow of gases or liquids, for example, in gas meters . Roots blowers were used for cabin pressurisation in aircraft, initially being investigated immediately before WW2 (using the Marshall supercharger ) and made by companies such as Sir George Godfrey and Partners who were still shipping increasing numbers into the 1960s, they were later superseded by air bleeds from jet engine compression stages. The simplest form of
4187-446: The fluid trapped between two long helical rotors, each fitted into the other when perpendicular at 90°, rotating inside a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous flow with equal volume and no vortex. It can work at low pulsation rates, and offers gentle performance that some applications require. Applications include: A peristaltic pump
4266-423: The gas trapped in the liquid (usually water), is released and accumulated somewhere in the pump, creating a pressure that can push part of the liquid upwards. Conventional impulse pumps include: Instead of a gas accumulation and releasing cycle, the pressure can be created by burning of hydrocarbons. Such combustion driven pumps directly transmit the impulse from a combustion event through the actuation membrane to
4345-410: The head of the cylinder. In the suction stroke, the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke, the plunger pushes the liquid out of the discharge valve. Efficiency and common problems: With only one cylinder in plunger pumps, the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when
4424-402: The heat (power) introduced by compression, but increases the power available because of the increased working mass for each cycle. Above about 5 psi (35 kPa) the intercooling improvement can become dramatic. With a Roots-type supercharger, one method successfully employed is the addition of a thin heat exchanger placed between the blower and the engine. Water is circulated through it to
4503-531: The latter, despite being more complicated, allows a higher engine efficiency and thus lower fuel consumption. Charles F. Kettering and colleagues, working at the General Motors Research Corporation and GM's subsidiary Winton Engine Corporation during the 1930s, designed two-stroke diesel engines for on-road use with much higher power-to-weight ratios and output range than contemporary four-stroke diesels. The first mobile application of
4582-418: The line bursts, the pump is severely damaged, or both. A relief or safety valve on the discharge side of the positive-displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually used only as a safety precaution. An external relief valve in the discharge line, with
4661-706: The number of stages. A pump that does not fit this description is simply a single-stage pump in contrast. In biology, many different types of chemical and biomechanical pumps have evolved ; biomimicry is sometimes used in developing new types of mechanical pumps. Mechanical pumps may be submerged in the fluid they are pumping or be placed external to the fluid. Pumps can be classified by their method of displacement into electromagnetic pumps , positive-displacement pumps , impulse pumps , velocity pumps , gravity pumps , steam pumps and valveless pumps . There are three basic types of pumps: positive-displacement, centrifugal and axial-flow pumps. In centrifugal pumps
4740-678: The other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th century—in the early days of steam propulsion—as boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating hand pumps were widely used to pump water from wells. Common bicycle pumps and foot pumps for inflation use reciprocating action. These positive-displacement pumps have an expanding cavity on
4819-480: The petrol or gasoline Otto engine . It also does not require either a carburettor to mix the air and fuel before delivery, or a spark plug or other ignition system. Another consequence is that to control speed and power output, the airflow is not throttled but only the amount of fuel injected at each cycle is varied. In the two-stroke cycle, the four stages of internal combustion engine operation (intake, compression, ignition, exhaust) occur in one 360° revolution of
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#17328554131534898-480: The plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration and water hammer may be a serious problem. In general, the problems are compensated for by using two or more cylinders not working in phase with each other. Centrifugal pumps are also susceptible to water hammer. Surge analysis , a specialized study, helps evaluate this risk in such systems. Triplex plunger pumps use three plungers, which reduces
4977-404: The pulsation relative to single reciprocating plunger pumps. Adding a pulsation dampener on the pump outlet can further smooth the pump ripple , or ripple graph of a pump transducer. The dynamic relationship of the high-pressure fluid and plunger generally requires high-quality plunger seals. Plunger pumps with a larger number of plungers have the benefit of increased flow, or smoother flow without
5056-475: The pump fluid. In order to allow this direct transmission, the pump needs to be almost entirely made of an elastomer (e.g. silicone rubber ). Hence, the combustion causes the membrane to expand and thereby pumps the fluid out of the adjacent pumping chamber. The first combustion-driven soft pump was developed by ETH Zurich. A hydraulic ram is a water pump powered by hydropower. It takes in water at relatively low pressure and high flow-rate and outputs water at
5135-465: The pump into the discharge pipe. This conversion of kinetic energy to pressure is explained by the First law of thermodynamics , or more specifically by Bernoulli's principle . Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved. These types of pumps have a number of characteristics: A practical difference between dynamic and positive-displacement pumps
5214-513: The pump requires very close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which eventually causes enlarged clearances that liquid can pass through, which reduces efficiency. Rotary positive-displacement pumps fall into five main types: Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to
5293-404: The ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water. Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits
5372-504: The resulting pulsations can cause fluid cavitation and/or damage to components downstream of the blower. For any given Roots blower running under given conditions, a single point will fall on the map. This point will rise with increasing boost and will move to the right with increasing blower speed. It can be seen that, at moderate speed and low boost, the efficiency can be over 90%. This is the area in which Roots blowers were originally intended to operate, and they are very good at it. Boost
5451-425: The scavenging losses make this advantage difficult to achieve in practice. In most EMD and GM (i.e. Detroit Diesel ) two-stroke engines, very few parameters are adjustable and all the remaining ones are fixed by the mechanical design of the engines. The scavenging ports are open from 45 degrees before BDC, to 45 degrees after BDC. However, some manufacturers make the scavenging port timing asymmetric by offsetting
5530-421: The shafts and drive fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal. Widely used for pumping difficult materials, such as sewage sludge contaminated with large particles, a progressing cavity pump consists of a helical rotor, about ten times as long as its width. This can be visualized as a central core of diameter x with, typically,
5609-417: The smallest engines or four valves on the largest, and a third lobe for the unit injector). Specific to EMD two-stroke engines ( 567 , 645 , and 710 ): Specific to GM two-stroke ( 6-71 ) and related on-road/off-road/marine two-stroke engines: Fuels used in diesel engines can be composed of heavier hydrocarbon oils than the petrol or gasoline used in spark-ignition engines, making them less volatile with
5688-488: The suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation. Positive-displacement pumps, unlike centrifugal , can theoretically produce the same flow at a given rotational speed no matter what the discharge pressure. Thus, positive-displacement pumps are constant flow machines . However,
5767-469: The suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation and the pump's volumetric efficiency can be achieved through routine maintenance and inspection of its valves. Typical reciprocating pumps are: The positive-displacement principle applies in these pumps: This
5846-399: The tube opens to its natural state after the passing of the cam it draws ( restitution ) fluid into the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract . Plunger pumps are reciprocating positive-displacement pumps. These consist of a cylinder with a reciprocating plunger. The suction and discharge valves are mounted in
5925-500: The two-stroke diesel engine was with the diesel streamliners of the mid-1930s. Continued development work resulted in improved two-stroke diesels for locomotive and marine applications in the late 1930s. This work laid the foundation for the dieselisation of railroads in the 1940s and 1950s in the United States. Towards the end of the twentieth century, interest in aircraft diesel engines revived, with two-stroke examples such as
6004-496: The two-stroke principle for the diesel engine. Hugo Güldner designed what is believed to be the first operational two-stroke diesel engine in 1899, and he convinced MAN , Krupp and Diesel to fund building this engine with ℳ 10,000 each. Güldner's engine had a 175 mm work cylinder, and a 185 mm scavenging cylinder; both had a stroke of 210 mm. The indicated power output was 12 PS (9 kW; 12 hp). In February 1900, this engine ran under its own power for
6083-547: The vacuum chamber. A variant uses claw-shaped rotors for higher compression. The Roots-type blower may achieve an efficiency of approximately 70% while achieving a maximum pressure ratio of two. Higher pressure ratios are achievable but at decreasing efficiency. Because a Roots-type blower pumps air in discrete pulses (unlike a screw compressor ), pulsation noise and turbulence may be transmitted downstream. If not properly managed (through outlet piping geometry) or accounted for (by structural reinforcement of downstream components),
6162-473: Was made in 1912 for an electric power plant. In collaboration with Blohm + Voss in Hamburg , MAN Nürnberg built the first double-acting piston two-stroke engine for marine use in 1913/1914. Paul Henry Schweitzer argues that the opposed piston two-stroke diesel engine was originally invented by Hugo Junkers . During World War I, MAN Nürnberg built a six-cylinder, double-acting piston, two-stroke diesel engine with
6241-423: Was successfully adopted in locomotive and marine applications, well into the postwar era. From 1923 until 1982, MAN had been using reverse flow scavenging for their marine two-stroke engines. From 1945, a slide valve for the ram induction effect was installed, and from 1954, constant gas flow supercharging with intercooling was used. The supercharging was achieved with the combination of four supercharging methods:
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