Marine propeller

Marine parts Marine piping systems Marine propeller Marine steroids Marine use Marinol Marjoram... 

Horizontally Mixing Aspirator Aerators. An aerator using a horizontally mixing aspirator has a marine propeller, submerged under water, attached to a soHd or a hoUow shaft. The other end of the shaft is out of the water and attached to an electric motor. When the propeller is rotated at high velocity, at either 1800 or 3600 rpm, a pressure drop develops around the propeller. Air is then aspirated under the water and mixed with the water, and moved out. This type of aerator, shown ia Figure 3g, is very efficient ia mixing wastewater. 

The stabihty of the emulsions further permits them to be compounded in simple Hquid-blending vessels by means of agitators, eg, marine-type propellers, paddles, or turbines. The adhesives can be adapted to any type of machine appHcation, ie, from spray guns to rollers to extmder-type devices. Different appHcators are fairly specific in their viscosity requirements, as are the various substrates receiving the adhesive. 

Uses. Uses for copper—siUcon alloys are siUcon bronze, UNS C 87200, as bearings, pumps, valve parts, marine fittings, and corrosion-resistant castings siUcon brass UNS C 87400 as bearings, gears, impellers, valve stems, and clamps and siUcon brass UNS C 87500 as small propellers, valve stems, gears, and bearings. 

Curve a is for marine propellers, d-jd = i/i, set a distance C = d or greater from tbe bottom of tbe vessel. The effect of changing d /dj is apparently felt only at very high Reynolds numbers and is not well estab-hsbed. 

Cyclically transmitted torque. Pulsating or cyclic torque in reciprocating prime movers and load machines such as reciprocating compressors, pumps, and marine propellers. 

Amongst the products made by polymerisation casting are propellers for small marine craft, conveyor buckets used in the mining industry, liners for coal washing equipment and main drive gears for use in the textile and papermaking industries. 

Figure 7-5. Marine propeller. (Source Holland, F. A. and Bragg, R. Fluid Flow for Chemioal Engineers, 2nd ed., Edward Arnold, 1995.)...

Zauner and Jones (2000a) describe an experimental set-up for determination of precipitation kinetics, as shown in Figure 6.19. Briefly, the jacket glass reactor (1) (300 ml, d = 65 mm) is equipped with a polyethylene draft tube and four baffles. The contents are stirred using a three-blade marine-type propeller (5) with motor (Haake), which pumps the suspension upwards in the annulus and downwards inside the draft tube. Measured power inputs ranged from 3.3 X 10- to 1.686 W/kg. 

The draft tubes of the reaetor are hollow in order to allow eooling or heating fluid to eireulate. The 300-ml laboratory-seale reaetor (1) is geometrieally similar to the larger reaetors. A marine-type impeller (propeller) provides a smooth and even flow field throughout the reaetor. 

A propeller converts through helical motion the energy supplied by a power source into thrust, a force that moves a vehicle foiward in a fluid medium. They are used primarily for marine and aerial propulsion, but they are found on other technologies such as hovercraft and wind turbines as well. Propellers,... 

Propellers for the marine environment appeared first in the eighteenth centui y. The French mathematician and founder of hydrodynamics, Daniel Bernoulli, proposed steam propulsion with screw propellers as early as 1752. However, the first application of the marine propeller was the hand-cranked screw on American inventor David Bushnell s submarine, Turtle in 1776. Also, many experimenters, such as steamboat inventor Robert Fulton, incorporated marine propellers into their designs. 

Typical marine propellers are fixed pitch and small in diameter with veiy thin, but broad, blade sections. They are made from either cast metal, corrosion-resistant metal alloys such as copper, or composite materials. Marine propellers normally operate at 60 percent efficiency due to the proximity of the ship s hull, which limits the overall diameter of the propeller and disturbs the efficient flow of water through the blades. As a result, the blades have to be veiy wide to produce adequate thrust. Marine propeller designers use innovations such as overlapping blades and wheel vanes to offset those problems and improve efficiency. 

Another important consideration for marine propeller design is cavitation, the rapid formation and then collapse of vacuum pockets on the blade surface at high speed, and its contributions to losses in propulsive efficiency. The phenomenon can cause serious damage to the propeller by eroding the blade surface and creating high frequency underwater noise. Cavitation first became a serious problem in the late nineteenth and early twentieth centuries... 

Cost moderate, less than marine propeller. 

Copper alloys in wrought or cast form are used for other purposes in ships and other marine installations, such as for propellers bearings, valves and pumps. One widespread application of aluminium-brass is its use for heating coils in tankers carrying crude oil or petroleum products. Some corrosion problems encountered in this and other applications on board ship have been described by Gilbert and Jenner . 

This type of damage is dealt with comprehensively in Section 8.8. It can be particularly severe in seawater giving rise to cavitation corrosion or cavitation erosion mechanisms, and hence can be a considerable problem in marine and offshore engineering. Components that may suffer in this way include the suction faces of propellers, the suction areas of pump impellers and casings, diffusers, shaft brackets, rudders and diesel-engine cylinder liners. There is also evidence that cavitation conditions can develop in seawater, drilling mud and produced oil/gas waterlines with turbulent high rates of flow. 

Fig. 6.6. Power number versus Reynolds number for various impellers (flat blades, turbine, vaned disk and marine propeller).

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