Posted tagged ‘velocity’

Introduction | Fluid Mechanics | Fluid properties

September 16, 2011

Fluid Mechanics – Introduction

01-Fluid Mechanics example - Static and Turbulent Flow - Analysis -Dynamic  analysis - CFD

Fluid Mechanics is that section of applied mechanics, concerned with the statics and dynamics of liquids and gases.

A knowledge of fluid mechanics is essential for the Mechanical engineer, because the majority of Mechanical processing operations are conducted either partially or totally in the fluid phase.

The handling of liquids is much simpler, much cheaper, and much less troublesome than handling solids.

Even in many operations a solid is handled in a finely divided state so that it stays in suspension in a fluid.

Fluid Statics: Which treats fluids in the equilibrium state of no shear stress

 02-Fluid Mechanics example - Static and Turbulent Flow - Analysis -Dynamic  analysis - CFD

Fluid Mechanics: Which treats when portions of fluid are in motion relative to other parts.

03-Fluid Mechanics example - Static and Turbulent Flow - Analysis -Dynamic  analysis - CFD

Fluids and their Properties

Fluids

In everyday life, we recognize three states of matter:

  • solid,
  • liquid and
  • gas.

Although different in many respects, liquids and gases have a common characteristic in which they differ from solids: they are fluids, lacking the ability of solids to offer a permanent resistance to a deforming force.

fluid is a substance which deforms continuously under the action of shearing forces, however small they may be.Conversely, it follows that:
If a fluid is at rest, there can be no shearing forces acting and, therefore, all forces in the fluid must be perpendicular to the planes upon which they act.

Shear stress in a moving fluid

Although there can be no shear stress in a fluid at rest, shear stresses are developed when the fluid is in motion, if the particles of the fluid move relative to each other so that they have different velocities, causing the original shape of the fluid to become distorted. If, on the other hand, the velocity of the fluid is same at every point, no shear stresses will be produced, since the fluid particles are at rest relative to each other.

PULLEY

August 23, 2011

Pulley:

01-standard pulley-spun end curve crown pulley-steel pulley-straight faced pulley-pulley mechanism-pulley ratio-pulley size-pulley selection

The diameters of standard pulleys are: 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1400 and 1600 mm. pulley may be straight faced or crowned. The crown serves to keep the belt centered. The height of the crown is usually 0.5% of the pulley width, but not less than 4 mm. The pulley diameter Dp depends on the number of plies of belt and may be also be determined from the formula:

Dp > K.i (mm)

Where

K = a factor depending on the number of plies (125 to 150)

i = no of plies

The compound value should be rounded off to the nearest standard size. While selecting the pulley diameter it should be ascertained that the diameter selected is larger than the minimum diameter of pulley for the particular belt selected.

The drive pulley may be lagged by rubber coating whenever necessary, to increase the coefficient of friction. The lagging thickness shall vary between 6 to 12 mm. The hardness of rubber lagging of the pulley shall be less than that of the cover rubber of the running belt.

Pulley types:


Pulleys are manufactured in a wide range of sizes, consisting of a continuous rim and two end discs fitted with hubs. In most of the conveyor pulleys intermediate stiffening discs are welded inside the rim. Other pulleys are self cleaning wing types which are used as the tail, take-up, or snub pulley where material tends to build up on the pulley face. Magnetic types of pulleys are used to remove tramp iron from the material being conveyed.

Typical welded steel pulley-Drum conveyor pulley

01-typical welded steel pulley-pulley types-pulley design-pulley system-pulley problems-pulley size

Spun end curve crown pulley

01-conveyor pulleys-spun end crown pulley-self cleaning wing pulley-snub pulley-pulley face-magenetic pulley

Spiral drum conveyor pulley

01-spiral drum conveyor pulley-pulley types-pulley with ball bearings-pulley for handling bulk load

Welded steel pulley with diamond grooved lagging

01-types of pulley-welded steel pulley-grooved lagging-belt conveyor drive-belt conveyor resistance-belt wrapping over pulleys

Welded steel pulley with grooved Lagging

01-welded steel pulley with grooved lagging-pulley types-belt conveyor speed reduction mechanism-belt conveyor drive arrangement

Spiral Wing Conveyor pulley

01-spiral wing conveyor pulley-belt conveyor calculation-belt conveyor formula-belt conveyor gallery

 

Power calculation for the drive unit:

The horse power required at the drive of a belt conveyor is derived from the following formula:

H.P = Te . V

Where

Te is the effective tension in the belt in N

V = velocity of the belt in m/s

The required effective tension Te on the driving pulley of a belt conveyor is obtained by adding up all the resistances.