Dakota Air Parts Intl., Inc. Is an aerospace and defense logistics corporation headquartered in Fargo, North Dakota. Dakota Air Parts specializes in the buying, selling and support of a variety of rotor-wing and fixed wing aircraft, turbine engines, and parts - OEM & aftermarket. Tool Aid S&G (90020) Reciprocating Air Saw Blades, Pack of 5. Only 7 left in stock (more on the way). Ingersoll Rand P4FS-20 Air Reciprocating Saw Blades for all standard shank air reciprocating saws. Only 3 left in stock (more on the way).
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Dyson Airblade is an electric hand dryer made by the Wiltshire, UK based company Dyson, found in public bathrooms across the United Kingdom.[1] It was introduced in the United Kingdom in 2006 and in the United States in late 2007. In 2013 the Airblade Tap was launched, which incorporates Airblade technology into a bathroom faucet enabling washing and drying in a single unit.
Description[edit]
Instead of using a wide jet of heated air, Dyson Airblade uses a thin layer of unheated air travelling at around 400 mph (180 m/s; 640 km/h) as a squeegee to remove water, rather than using heat to evaporate the water.[2] The Dyson Airblade is claimed by its manufacturer to dry hands in 10 seconds and to use less electricity than conventional hand dryers.[1]
The first commercially available high-speed, horizontal-wiping air dryer was the Mitsubishi Jet Towel, invented in 1993 and available in the United States since 2005.[3] There are several technical differences among electric hand dryers, such as airspeed, water containment, energy efficiency, use of heat, type of filter, motor lifespan and power usage.[4]
The same technology is used by Dyson in the Air Multiplierfan to create a cooling air stream for personal comfort.
Energy efficiency[edit]
The Dyson Airblade is 69% more energy-efficient than conventional hand-dryers and 97% more cost effective than paper towels.[5] The Airblade is cheaper to operate because it does not require hot air which greatly increases electricity consumption. The Airblade is also cheaper to operate due to decreased drying times. The Airblade V can dry off hands in 12 seconds, versus 25 for a traditional hand dryer.[6]
Drying time[edit]
A comparative test found that both paper towels and the Airblade dried hands quickly, achieving around 90% dryness in about ten seconds, supporting Dyson's claim of approximately ten seconds of drying time.[7] A conventional warm air dryer took about forty-seven seconds.
Hygiene[edit]
Dyson Airblade (view from top)
In the United States, Dyson worked with the NSF to become the only certified hand dryer under Protocol P335 for Hygienic Commercial Hand Dryers.[8][9] The Royal Society of Public Health has given the Dyson Airblade hand dryer its first hygiene accreditation.[10]
A paper was presented at the 17th European Congress of Clinical Microbiology and Infectious Diseases, Munich, Germany in 2007 by the University of Bradford and Dyson showing that for a set drying time of 10 seconds, the Airblade led to significantly less bacterial transfer than with the other driers (p < 0.05). When the latter were used for longer (30–35 s) the trend was for the Airblade to still perform better; however, these results did not reach statistical significance (p > 0.05). In addition the study showed that rubbing hands whilst using the driers counteracted the reduction in overall bacterial numbers at all anatomical sites.[11]
Hygiene associated with the product has been questioned in research by the University of Westminster Trade Group, London and sponsored by the paper towel industry the European Tissue Symposium, which suggests that use increases the amount of bacteria on the fingertips by about 42%; paper towels reduced the number of bacteria by 50 to 75%, while warm air dryers increased bacteria by 194%. The report found that 'the manufacturer’s claim that the tested JAD [Airblade] is 'the most hygienic hand dryer' is confirmed ... assuming that the term 'hand dryer' refers to electric devices only because its performance in terms of the numbers of all types of bacteria remaining on the hands of users compared to paper towels was significantly worse.'[7]
Model history[edit]
Airblade (AB14) Mk. 2
In early 2013, three new models of the Dyson Airblade were introduced: the Airblade Mk. 2, the Airblade V, and the Airblade Tap. The Mk. 2 uses a similar design as the original model, but has increased jet air speed from 400–430 mph (180–190 m/s; 640–690 km/h), and new soundproofing makes the new model quieter than the old one. The Airblade V is a hands-under hand dryer that complies with the Americans With Disabilities Act.
The Airblade Tap is a non-contact bathroom faucet that both washes and dries hands. It eliminates the need to move to a separate area to dry hands, and therefore eliminates any water dripped on the floor.[12][13] All three hand dryers use a new Digital Slim Motor, the Dyson V4.
Controversies[edit]
On 5 December 2012, a lawsuit by competitor Excel Dryer was filed against Dyson, claiming that Dyson's advertising comparing the Airblade to the Excel Dryer Xlerator were deceptive.[15] Dyson's advertisements stated the Xlerator produces twice as much carbon dioxide, is worse for the environment, and costs more to operate than the Airblade. Excel Dryer charged that Dyson was falsifying its comparisons by submitting a 20-second dry time for the Xlerator to the Materials Systems Laboratory at the Massachusetts Institute of Technology, rather than Excel Dryer's tested 12-second dry time, thus inflating energy consumption figures in the Airblade's favor.
In 2014, a paper was published in the Journal of Hospital Infection (2014;88:199-206), showing that high-speed hand dryers such as the Dyson Airblade can spread large numbers of a harmless test bacteria through the air in the vicinity. The Dyson company challenged the study with its own criticism of the methods and conclusions.[16]
References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Dyson_Airblade&oldid=935104347'
An animated simulation of an axial compressor. The static blades are the.An axial compressor is a that can continuously.
It is a rotating, -based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from other rotating compressors such as, axi-centrifugal compressors and mixed-flow compressors where the fluid flow will include a 'radial component' through the compressor.
The energy level of the fluid increases as it flows through the compressor due to the action of the rotor blades which exert a torque on the fluid. The stationary blades slow the fluid, converting the circumferential component of flow into pressure. Compressors are typically driven by an or a or a gas turbine.Axial flow compressors produce a continuous flow of compressed gas, and have the benefits of high and large, particularly in relation to their size and cross-section. They do, however, require several rows of airfoils to achieve a large pressure rise, making them complex and expensive relative to other designs (e.g. Centrifugal compressors).Axial compressors are integral to the design of large such as, high speed ship engines, and small scale power stations. They are also used in industrial applications such as large volume air separation plants, air, fluid cracking air, and propane.
Due to high performance, high reliability and flexible operation during the flight envelope, they are also used in engines. Typical applicationType of flowPressure ratio per stageEfficiency per stageIndustrialSubsonic1.05–1.288–92%Aerospace1.15–1.680–85%Research1.8–2.275–85%. The compressor in a.Axial compressors consist of rotating and stationary components. A shaft drives a central drum which is retained by bearings inside of a stationary tubular casing. Between the drum and the casing are rows of airfoils, each row connected to either the drum or the casing in an alternating manner.
A pair of one row of rotating airfoils and the next row of stationary airfoils is called a stage. The rotating airfoils, also known as blades or rotors, accelerate the fluid in both the axial and circumferential directions. The stationary airfoils, also known as vanes, nozzle guide vanes or stators, convert the increased kinetic energy into static pressure through and redirect the flow direction of the fluid to prepare it for the rotor blades of the next stage. The cross-sectional area between rotor drum and casing is reduced in the flow direction to maintain an optimum axial velocity as the fluid is compressed.Working As the fluid enters and leaves in the axial direction, the centrifugal component in the energy equation does not come into play. Here the compression is fully based on diffusing action of the passages. The diffusing action in the stator converts the absolute kinetic head of the fluid into a rise in pressure.
The relative kinetic head in the energy equation is a term that exists only because of the rotation of the rotor. The rotor reduces the relative kinetic head of the fluid and adds it to the absolute kinetic head of the fluid i.e., the impact of the rotor on the fluid particles increases their velocity (absolute) and thereby reduces the relative velocity between the fluid and the rotor.
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In short, the rotor increases the absolute velocity of the fluid and the stator converts this into pressure rise. Designing the rotor passage with a diffusing capability can produce a pressure rise in addition to its normal functioning. This produces greater pressure rise per stage which constitutes a stator and a rotor together.
This is the reaction principle in. If 50% of the pressure rise in a stage is obtained at the rotor section, it is said to have a 50% reaction. Design The increase in pressure produced by a single stage is limited by the relative velocity between the rotor and the fluid, and the turning and diffusion capabilities of the airfoils.
A typical stage in a commercial compressor will produce a pressure increase of between 15% and 60% (pressure ratios of 1.15–1.6) at design conditions with a efficiency in the region of 90–95%. To achieve different pressure ratios, axial compressors are designed with different numbers of stages and rotational speeds. As a rule of thumb we can assume that each stage in a given compressor has the same temperature rise (Delta T).
Therefore, at the entry, temperature (Tstage) to each stage must increase progressively through the compressor and the ratio (Delta T)/(Tstage) entry must decrease, thus implying a progressive reduction in stage pressure ratio through the unit. Hence the rear stage develops a significantly lower pressure ratio than the first stage.Higher stage pressure ratios are also possible if the relative velocity between fluid and rotors is supersonic, but this is achieved at the expense of efficiency and operability. Such compressors, with stage pressure ratios of over 2, are only used where minimizing the compressor size, weight or complexity is critical, such as in military jets.The airfoil profiles are optimized and matched for specific velocities and turning. Although compressors can be run at other conditions with different flows, speeds, or pressure ratios, this can result in an efficiency penalty or even a partial or complete breakdown in flow (known as compressor stall and pressure surge respectively). Thus, a practical limit on the number of stages, and the overall pressure ratio, comes from the interaction of the different stages when required to work away from the design conditions. These “off-design” conditions can be mitigated to a certain extent by providing some flexibility in the compressor. This is achieved normally through the use of adjustable stators or with valves that can bleed fluid from the main flow between stages (inter-stage bleed).Modern jet engines use a series of compressors, running at different speeds; to supply air at around 40:1 pressure ratio for combustion with sufficient flexibility for all flight conditions.Kinetics and energy equations.
Low-pressure axial compressor scheme of the turbojet.In the jet engine application, the compressor faces a wide variety of operating conditions. On the ground at takeoff the inlet pressure is high, inlet speed zero, and the compressor spun at a variety of speeds as the power is applied. Once in flight the inlet pressure drops, but the inlet speed increases (due to the forward motion of the aircraft) to recover some of this pressure, and the compressor tends to run at a single speed for long periods of time.There is simply no 'perfect' compressor for this wide range of operating conditions. Fixed geometry compressors, like those used on early jet engines, are limited to a design pressure ratio of about 4 or 5:1. As with any, is strongly related to the, so there is very strong financial need to improve the compressor stages beyond these sorts of ratios.Additionally the compressor may if the inlet conditions change abruptly, a common problem on early engines. In some cases, if the stall occurs near the front of the engine, all of the stages from that point on will stop compressing the air.
In this situation the energy required to run the compressor drops suddenly, and the remaining hot air in the rear of the engine allows the turbine to speed up the whole engine dramatically. This condition, known as surging, was a major problem on early engines and often led to the turbine or compressor breaking and shedding blades.For all of these reasons, axial compressors on modern jet engines are considerably more complex than those on earlier designs.Spools All compressors have an optimum point relating rotational speed and pressure, with higher compressions requiring higher speeds. Early engines were designed for simplicity, and used a single large compressor spinning at a single speed. Later designs added a second turbine and divided the compressor into low-pressure and high-pressure sections, the latter spinning faster. This two-spool design, pioneered on the, resulted in increased efficiency. Further increases in efficiency may be realised by adding a third spool, but in practice the added complexity increases maintenance costs to the point of negating any economic benefit.
That said, there are several three-spool engines in use, perhaps the most famous being the, used on a wide variety of commercial aircraft.Bleed air, variable stators. See also:As an aircraft changes speed or altitude, the pressure of the air at the inlet to the compressor will vary. In order to 'tune' the compressor for these changing conditions, designs starting in the 1950s would 'bleed' air out of the middle of the compressor in order to avoid trying to compress too much air in the final stages. This was also used to help start the engine, allowing it to be spun up without compressing much air by bleeding off as much as possible.
Bleed systems were already commonly used anyway, to provide airflow into the stage where it was used to cool the turbine blades, as well as provide pressurized air for the systems inside the aircraft.A more advanced design, the variable stator, used blades that can be individually rotated around their axis, as opposed to the power axis of the engine. For startup they are rotated to 'closed', reducing compression, and then are rotated back into the airflow as the external conditions require. The was the first major example of a variable stator design, and today it is a common feature of most military engines.Closing the variable stators progressively, as compressor speed falls, reduces the slope of the surge (or stall) line on the operating characteristic (or map), improving the surge margin of the installed unit. By incorporating variable stators in the first five stages, has developed a ten-stage axial compressor capable of operating at a 23:1 design pressure ratio.Design notes Energy exchange between rotor and fluid The relative motion of the blades to the fluid adds velocity or pressure or both to the fluid as it passes through the rotor.
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The fluid velocity is increased through the rotor, and the stator converts kinetic energy to pressure energy. Some diffusion also occurs in the rotor in most practical designs.The increase in velocity of the fluid is primarily in the tangential direction (swirl) and the stator removes this angular momentum.The pressure rise results in a rise. For a given geometry the temperature rise depends on the square of the tangential of the rotor row. Current engines have fans that operate at Mach 1.7 or more, and require significant containment and noise suppression structures to reduce blade loss damage and noise.Compressor maps A map shows the performance of a compressor and allows determination of optimal operating conditions. It shows the mass flow along the horizontal axis, typically as a percentage of the design mass flow rate, or in actual units. The pressure rise is indicated on the vertical axis as a ratio between inlet and exit stagnation pressures.A surge or stall line identifies the boundary to the left of which the compressor performance rapidly degrades and identifies the maximum pressure ratio that can be achieved for a given mass flow.
Contours of efficiency are drawn as well as performance lines for operation at particular rotational speeds.Compression stability Operating efficiency is highest close to the stall line. If the downstream pressure is increased beyond the maximum possible the compressor will stall and become unstable.Typically the instability will be at the of the system, taking the downstream plenum into account.See also.References. ^ Yahya, S.M.
Turbines, Compressors and Fans. Tata McGraw Hill Education Private Limited. ^ Meherwan, P.Boyce. Academic Dictionaries and Encyclopedias.
Perry, R.H. And Green, D.W.
(Eds.) (2007). Perry's Chemical Engineers' Handbook (8th ed.). McGraw Hill. Greitzer, E. (1 April 1976). 'Surge and Rotating Stall in Axial Flow Compressors—Part I: Theoretical Compression System Model'.
Journal of Engineering for Power. 98 (2): 190–198. Practical considerations in designing the engine cycle, Philpott, pp. 2-8, 2-17. McDougall, NM; Cumpsty, NA; Hynes, TP (2012). 'Stall inception in axial compressors'.
Journal of Turbomachinery. 112 (1): 116–123. p.2. ^ The Engineer magazine May 27, 1938 Supplement The Development Of Blowers And Compressors p.xxxiiiBibliography.
Treager, Irwin E. 'Aircraft Gas Turbine Engine Technology' 3rd edn, McGraw-Hill Book Company, 1995,. Hill, Philip and Carl Peterson.
'Mechanics and Thermodynamics of Propulsion,' 2nd edn, Prentice Hall, 1991. Kerrebrock, Jack L.
'Aircraft Engines and Gas Turbines,' 2nd edn, Cambridge, Massachusetts: The MIT Press, 1992. Rangwalla, Abdulla. 'Turbo-Machinery Dynamics: Design and Operation,' New York: McGraw-Hill: 2005. Wilson, David Gordon and Theodosios Korakianitis. 'The Design of High-Efficiency Turbomachinery and Turbines,' 2nd edn, Prentice Hall, 1998.
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