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Hydraulic Machinery:

Hydraulic machines are machinery and tools that use liquid fluid power to do simple

work. Heavy equipment is a common example.

In this type of machine, hydraulic fluid  is transmitted throughout the machine to varioushydraulic motors and hydraulic cylinders and which becomes pressurised according to 

the resistance present. The fluid is controlled directly or automatically by control valves 

and distributed through hoses  and tubes .

The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and

wide array of actuators  that can make use of this power. 

Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering

medium.

Hydraulic circuits

For the hydraulic fluid to do work, it must flow to the actuator and or motors, then return

to a reservoir. The fluid is then filtered and re-pumped. The path taken by hydraulic

fluid is called a hydraulic circuit of which there are several types. Open center circuits

use pumps which supply a continuous flow. The flow is returned to tank through the

control valve's open center ; that is, when the control valve is centered, it provides an

open return path to tank and the fluid is not pumped to a high pressure. Otherwise, if thecontrol valve is actuated it routes fluid to and from an actuator and tank. The fluid's

 pressure will rise to meet any resistance, since the pump has a constant output. If the

 pressure rises too high, fluid returns to tank through a pressure relief valve. Multiplecontrol valves may be stacked in series [1]. This type of circuit can use inexpensive,

constant displacement pumps.

Closed center circuits supply full pressure to the control valves, whether any valves are

actuated or not. The pumps vary their flow rate, pumping very little hydraulic fluid untilthe operator actuates a valve. The valve's spool therefore doesn't need an open center 

return path to tank. Multiple valves can be connected in a parallel arrangement and

system pressure is equal for all valves.

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LAMINAR FLOW

Laminar flow, sometimes known as streamline  flow, occurs when a fluid flows in

parallel layers, with no disruption between the layers.[1] At low velocities the fluidtends to flow without lateral mixing, and adjacent layers slide past one another like

 playing cards. There are no cross currents perpendicular to the direction of flow, nor eddies or swirls of fluids.[2] In laminar flow the motion of the particles of fluid is very

orderly with all particles moving in straight lines parallel to the pipe walls .[3] In fluiddynamics, laminar flow is a flow regime characterized by high momentum diffusion and

low momentum convection.

When a fluid is flowing through a closed channel such as a pipe or between two flat

 plates, either of two types of flow may occur depending on the velocity of the fluid:laminar flow or turbulent flow . Laminar flow is the opposite of turbulent flow  which

occurs at higher velocities where eddies or small packets of fluid particles form leading to

lateral mixing.[2] In nonscientific terms laminar flow is "smooth", while turbulent flow is

"rough."

The type of flow occurring in a fluid in a channel is important in fluid dynamics

 problems. The dimensionless  Reynolds number   is an important parameter in the

equations that describe whether flow conditions lead to laminar or turbulent flow. In thecase of flow through a straight pipe with a circular cross-section, at a Reynolds number 

 below the critical value of approximately 2040 [4]  fluid motion will ultimately be laminar, 

whereas at larger Reynolds number the flow can be turbulent. The Reynolds number delimiting laminar and turbulent flow depends on the particular flow geometry, and

moreover, the transition from laminar flow to turbulence can be sensitive to disturbance

levels and imperfections present in a given configuration.

When the Reynolds number  is much less than 1, Creeping motion or  Stokes flow occurs.This is an extreme case of laminar flow where viscous (friction) effects are much greater 

than inertial forces. The common application of laminar flow would be in the smooth

flow of a viscous liquid through a tube or pipe. In that case, the velocity of flow variesfrom zero at the walls to a maximum along the centerline of the vessel. The flow profile

of laminar flow in a tube can be calculated by dividing the flow into thin cylindrical

elements and applying the viscous force to them.[5]

For example, consider the flow of air over an aircraft wing. The boundary layer is a verythin sheet of air lying over the surface of the wing (and all other surfaces of the aircraft).

Because air has viscosity, this layer of air tends to adhere to the wing. As the wing moves

forward through the air, the boundary layer at first flows smoothly over the streamlinedshape of the airfoil. Here the flow is called laminar and the boundary layer is a laminar 

layer . Prandtl applied the concept of the laminar boundary layer to airfoils in 1904.[6][7]

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Incompressible Flow:

In fluid mechanics or more generally continuum mechanics, incompressible (isochoric)flow refers to flow in which the material density is constant within an infinitesimal

volume that moves with the velocity of the fluid. An equivalent statement that impliesincompressible flow is that the divergence of the fluid velocity is zero (see the derivation

 below, which illustrates why these conditions are equivalent).

Incompressible flow does not imply that the fluid itself is incompressible. It is shown in

the derivation below that even compressible fluids can undergo incompressible flow.

Incompressible fluids must have a constant density everywhere, while incompressible

flow only requires that the density remain constant within a parcel of fluid which moveswith the fluid velocity.

MAJOR AND MINOR ENERGY LOSSES

Minor Energy Loss Attributions

Major losses result from friction within the pipe. Minor losses include those

attributed to junctions, exits, bends in pipes, manholes, expansion and contraction,

and appurtenances such as valves and meters.

Minor losses in a storm drain system are usually insignificant. In a large system,

however, their combined effect may be significant. Methods are available to estimate

these minor losses if they appear to be cumulatively important. You may minimize thehydraulic loss potential of storm drain system features such as junctions, bends,

manholes, and confluences to some extent by careful design. For example, you can

replace severe bends by gradual curves in the pipe run where right-of-way is sufficientand increased costs are manageable. Well designed manholes and inlets, where there are

no sharp or sudden transitions or impediments to the flow, cause virtually no significant

losses.

Tubes, pipes and hoses

 Hydraulic tubes are seamless steel precision pipes, specially manufactured for hydraulics.

The tubes have standard sizes for different pressure ranges, with standard diameters up to100 mm . The tubes are supplied by manufacturers in lengths of 6 m, cleaned, oiled and

 plugged. The tubes are interconnected by different types of flanges (especially for the

larger sizes and pressures), welding cones/nipples (with o-ring seal), several types of flare

connection and by cut-rings. In larger sizes, hydraulic pipes are used. Direct joining of tubes by welding is not acceptable since the interior cannot be inspected.

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 Hydraulic pipe  is used in case standard hydraulic tubes are not available . Generally

these are used for low pressure. They can be connected by threaded connections, but

usually by welds. Because of the larger diameters the pipe can usually be inspected

internally after welding. Black pipe  is non-galvanized  and suitable for welding .

 Hydraulic hose  is graded by pressure, temperature, and fluid compatibility. Hoses are used when pipes or tubes can not be used, usually to provide flexibility for machine

operation or maintenance. The hose is built up with rubber and steel layers. A rubber interior is surrounded by multiple layers of woven wire and rubber. The exterior is

designed for abrasion resistance. The bend radius of hydraulic hose is carefully designed

into the machine, since hose failures can be deadly, and violating the hose's minimum bend radius will cause failure. Hydraulic hoses generally have steel fittings swaged on the

ends. The weakest part of the high pressure hose is the connection of the hose to the

fitting. Another disadvantage of hoses is the shorter life of rubber which requires periodicreplacement, usually at five to seven year intervals.

Tubes and pipes for hydraulic applications are internally oiled before the system iscommissioned. Usually steel piping is painted outside. Where flare and other couplings

are used, the paint is removed under the nut, and is a location where corrosion can begin.For this reason, in marine applications most piping is stainless steel.

Pipe Network Analysis:

In fluid dynamics, pipe network analysis is the analysis of the fluid flow through a

hydraulics network, containing several or many interconnected branches. The aim is to

determine the flow rates and pressure drops in the individual sections of the network.This is a common problem in hydraulic design.

Description

In order to direct water to many individuals in a municipal water supply, many times thewater is routed through a water supply network . A major part of this network may consist

of interconnected pipes. This network creates a special class of problems in hydraulic

design typically referred to as pipe network analysis. The modern solution for this is touse specialized software in order to automatically solve the problems. However, the

 problems can also be addressed with simpler methods like a spreadsheet equipped with a

solver, or a modern graphing calculator.

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Network analysis

Once the friction factors are solved for, then we can start considering the network 

 problem. We can solve the network by satisfying two conditions.

1. At any junction, the flow into a junction equals the flow out of the junction.2. Between any two junctions, the head loss is independent of the path taken.

The classical approach for solving these networks is to use the Hardy Cross method. In

this formulation, first you go through and create guess values for the flows in thenetwork. That is, if Q7 enters a junction and Q6 and Q4 leave the same junction, then the

initial guess must satisfy Q7 = Q6 + Q4. After the initial guess is made, then, a loop is

considered so that we can evaluate our second condition. Given a starting node, we work 

our way around the loop in a clockwise fashion, as illustrated by Loop 1. We add up thehead losses according to the Darcy–Weisbach equation f each pipe if Q is in the same

direction as our loop like Q1, and subtract the head loss if the flow is in the reverse

direction, like Q4. In order to satisfy the second condition, we should end up with 0 aboutthe loop if the network is completely solved. If the actual sum of our head loss is not

equal to 0, then we will adjust all the flows in the loop by an amount given by the

following formula, where a positive adjustment is in the clockwise direction.

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Uses Of Hydraulic Machinery

For the majority of operations requiring very great force applied through a comparatively

short stroke, as in riveting, punching, shearing, lifting, forging, flanging, and many other similar operations, there is no other machinery so efficient as hydraulic; first, because

there is absolutely no motion or power consumed except in the act, and at the moment of 

 performing the desired operation - at all other times everything is at rest; secondly, because the water  is carried or transmitted in a small pipe from its reservoir or tank to the

machine. Under proper conditions, this transmission can be accomplished with an

efficiency far surpassing that of the line-shaft, electric wire, or air tube. All the energywhich a steam pump can deliver in the course of 10 to 15 minutes is utilized in the

hydraulic machine within a few seconds. This is not possible in the use of any other form

of machine tool.

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USES:

Hydraulic systems require high-pressure liquid power to operate. The liquid must be

in a pure state; therefore, hydraulic liquid has to pass through an oil purificationsystem to remove any contaminants. Many cylinders and motors move the liquid

through the tubes, hoses and valves. You can find a variety of machinery andequipment that use hydraulic systems to work.

Fork Lift

• Fork lifts run via hydraulic systems. The heavy machines are industrial trucks for 

transporting and lifting materials. Typically, fork lifts move pallets in distribution

centers and warehouses. The forklift mast assists in moving the machine up and

down. Hydraulic cylinders operate the mast of the forklift.

Backhoe• Hydraulics make up some of the components of a backhoe. A tractor backhoe,

also referred to as a digger, is excavating machinery. The equipment features a

two-part articulating arm with a thumb attachment at the end that picks upmaterials, such as dirt. The movable arm-and-thumb attachment utilizes a

hydraulic system that helps move the unit accurately.

Sport Utility Vehicles

• The Environmental Protection Agency introduced the first sport utility vehicle

with a full-size hydraulic powertrain, which the EPA patented. The agency boaststhe system will increase the fuel economy and will reduce wear and tear on the

 brakes. The chief benefit of a hydraulic hybrid vehicle is the ability to capture anduse a large percentage of the energy normally lost in vehicle braking, the EPA

claims

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Similitude is a concept applicable to the testing of engineering models. A model is said

to have similitude with the real application if the two share geometric similarity,

kinematic similarity and dynamic similarity. Similarity and similitude are interchangeablein this context.

The term dynamic similitude is often used as a catch-all because it implies that

geometric and kinematic similitude have already been met.

Similitude's main application is in hydraulic and aerospace engineering to test fluid flowconditions with scaled models. It is also the primary theory behind many textbook 

formulas in fluid mechanics.

Engineering models are used to study complex fluid dynamics problems where

calculations and computer simulations aren't reliable. Models are usually smaller than thefinal design, but not always. Scale models allow testing of a design prior to building, and

in many cases are a critical step in the development process.

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Construction of a scale model, however, must be accompanied by an analysis to

determine what conditions it is tested under. While the geometry may be simply scaled,

other parameters, such as pressure, temperature or the velocity and type of fluid may needto be altered. Similitude is achieved when testing conditions are created such that the test

results are applicable to the real design.

The following criteria are required to achieve similitude;

• Geometric similarity – The model is the same shape as the application, usuallyscaled.

• Kinematic similarity – Fluid flow of both the model and real application must

undergo similar time rates of change motions. (fluid streamlines are similar)

• Dynamic similarity – Ratios of all forces acting on corresponding fluid particlesand boundary surfaces in the two systems are constant.

•

To satisfy the above conditions the application is analyzed;

1. All parameters required to describe the system are identified using principles fromcontinuum mechanics.

2. Dimensional analysis is used to express the system with as few independent

variables and as many dimensionless parameters as possible.

3. The values of the dimensionless parameters are held to be the same for both thescale model and application. This can be done because they are dimensionless and

will ensure dynamic similitude between the model and the application. Theresulting equations are used to derive scaling laws which dictate model testingconditions.

It is often impossible to achieve strict similitude during a model test. The greater the

departure from the application's operating conditions, the more difficult achieving

similitude is. In these cases some aspects of similitude may be neglected, focusing ononly the most important parameters.

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The design of marine vessels remains more of an art than a science in large part because

dynamic similitude is especially difficult to attain for a vessel that is partially submerged:

a ship is affected by wind forces in the air above it, by hydrodynamic forces within thewater under it, and especially by wave motions at the interface between the water and the

air. The scaling requirements for each of these phenomena differ, so models cannot

replicate what happens to a full sized vessel nearly so well as can be done for an aircraftor submarine—each of which operates entirely within one medium.

Similitude is a term used widely in fracture mechanics relating to the strain life approach.

Under given loading conditions the fatigue damage in an un-notched specimen is

comparable to that of a notched specimen. Similitude suggests that the component fatiguelife of the two objects will also be similar.

Dimensional Analysis

In physics and all science, dimensional analysis is a tool to find or check relations

among physical quantities by using their dimensions. The dimension of a physicalquantity is the combination of the basic physical dimensions (usually mass, length, time,

electric charge, and temperature) which describe it; for example, speed has the dimension

length per unit time, and may be measured in meters per second, miles per hour, or other units. Dimensional analysis is based on the fact that a physical law must be independent

of the units used to measure the physical variables. A straightforward practical

consequence is that any meaningful equation (and any inequality and inequation) must

have the same dimensions in the left and right sides. Checking this is the basic way of  performing dimensional analysis.

Dimensional analysis is routinely used to check the plausibility of derived equations and

computations. It is also used to form reasonable hypotheses about complex physicalsituations that can be tested by experiment or by more developed theories of the

 phenomena, and to categorize types of physical quantities and units based on their 

relations to or dependence on other units, or their dimensions if any.

Great Principle of Similitude

The basic principle of dimensional analysis was known to Isaac Newton (1686) whoreferred to it as the "Great Principle of Similitude".[1] James Clerk Maxwell played a

major role in establishing modern use of dimensional analysis by distinguishing mass,length, and time as fundamental units, while referring to other units as derived.[2] The

19th-century French mathematician Joseph Fourier  made important contributions[3]  based

on the idea that physical laws like  F = ma should be independent of the units employed tomeasure the physical variables. This led to the conclusion that meaningful laws must be

homogeneous equations in their various units of measurement, a result which was

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eventually formalized in the Buckingham π theorem. This theorem describes how every

 physically meaningful equation involving n variables can be equivalently rewritten as an

equation of n − m dimensionless parameters, where m is the number of fundamentaldimensions used. Furthermore, and most importantly, it provides a method for computing

these dimensionless parameters from the given variables.

A dimensional equation can have the dimensions reduced or eliminated through

nondimensionalization, which begins with dimensional analysis, and involves scalingquantities by characteristic units of a system or natural units of nature. This gives insight

into the fundamental properties of the system, as illustrated in the examples below.

Definition

The dimensions of a physical quantity are associated with combinations of mass, length,time, electric charge, and temperature, represented by sans-serif symbols M, L, T, Q, and

Θ, respectively, each raised to rational powers.

The term dimension is more abstract than scale unit: mass is a dimension, whilekilograms are a scale unit (choice of standard) in the mass dimension.

As examples, the dimension of the physical quantity speed is distance/time (L/T or 

LT−1), and the dimension of the physical quantity force is "mass × acceleration" or 

"mass×(distance/time)/time" (ML/T2 or MLT−2). In principle, other dimensions of  physical quantity could be defined as "fundamental" (such as momentum or energy or 

electric current) in lieu of some of those shown above. Most[citation needed ] physicists do not

recognize temperature, Θ, as a fundamental dimension of physical quantity since it

essentially expresses the energy per particle per degree of freedom, which can be

expressed in terms of energy (or mass, length, and time). Still others do not recognizeelectric charge, Q, as a separate fundamental dimension of physical quantity, since it has

 been expressed in terms of mass, length, and time in unit systems such as the cgs system.There are also physicists that have cast doubt on the very existence of incompatible

fundamental dimensions of physical quantity.[4]

The unit of a physical quantity and its dimension are related, but not identical concepts.

The units of a physical quantity are defined by convention and related to some standard;e.g., length may have units of meters, feet, inches, miles or micrometres; but any length

always has a dimension of L, independent of what units are arbitrarily chosen to measure

it. Two different units of the same physical quantity have conversion factors that relate

them. For example: 1 in = 2.54 cm; then (2.54 cm/in) is the conversion factor, and isitself dimensionless and equal to one. Therefore multiplying by that conversion factor 

does not change a quantity. Dimensional symbols do not have conversion factors.

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Hydraulic Turbine

A water turbine is a rotary engine that takes energy from moving water .

Water turbines were developed in the 19th century and were widely used for industrial

 power prior to electrical grids. Now they are mostly used for electric power  generation.They harness a clean and renewable energy source.

History

Water wheels have been used for thousands of years for industrial power. Their main

shortcoming is size, which limits the flow rate and head that can be harnessed. Themigration from water wheels to modern turbines took about one hundred years.

Development occurred during the Industrial revolution, using scientific principles and

methods. They also made extensive use of new materials and manufacturing methodsdeveloped at the time.

Efficiency

Large modern water turbines operate at mechanical efficiencies greater than 90% (not to

 be confused with thermodynamic efficiency).

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Horsepower (HP) is the name of several units of measurement of  power . The most

common definitions equal between 735.5 and 750 watts.[1] Horsepower was originally

defined to compare the output of steam engines with the power of  draft horses. The unitwas widely adopted to measure the output of piston engines, turbines, electric motors,

and other machinery. The definition of the unit varied between geographical regions.

Most countries now use the SI unit watt for measurement of power. With theimplementation of the EU Directive 80/181/EEC on January 1, 2010, the use of 

horsepower in the EU is only permitted as supplementary unit.

Boiler horsepower (BHP)

One boiler horse power unit or BHP is equal to a boiler thermal output of 33,475 BTU/h

(9.811 kW), which is the energy rate needed to evaporate 34.5 lb (15.65 kg) at 212 °F(100 °C) in one hour. The unit is not current outside of North America.

The term was originally developed at the Philadelphia Centennial Exhibition in 1876,

where the best steam engines of that period were tested. The average steam consumption

of those engines (per output horsepower) was determined to be the evaporation of 30 lb/hof water, based on feedwater at 100 °F (37.8 °C), and saturated steam generated at 70 psi

(480 kPa) gauge pressure. This original definition is equivalent to a boiler heat output of 

33,485 BTU/h (9.813 kW). In 1884, the ASME redefined the boiler horsepower as thethermal output equal to the evaporation of 34.5 lb/h of water "from and at" 212 °F. This

considerably simplified boiler testing, and provided more accurate comparisons of the

 boilers at that time. This revised definition is equivalent to a boiler heat output of 33,469 BTU/h (9.809 kW). Present industrial practice is to define boiler horsepower as a

 boiler thermal output equal to 33,475 BTU/h (9.811 kW), which is very close to the

original and revised definitions.

The amount of power that can be obtained by a steam engine or steam turbine based onboiler horsepower varies so widely that use of the term is entirely obsolete for these

 purposes. The term makes no distinction as to the steam pressure or temperature which is

 produced (both of which significantly influence engine/turbine output); it merely definesa thermal output of a boiler. Smaller steam engines often require several boiler 

horsepower to make one horsepower, and modern steam turbines can make power with as

little as about 0.15 hp (boiler) thermal output per actual horsepower developed.