. Linkage mechanisms :
1.1 Four bar linkages
Linkage are composed of links and lower pairs. The simplest closed-loop linkage is the four-bar linkage, which has three moving links, one fixed link and four pin joints. A linkage with one link fixed is a mechanism. You can load the following four-bar linkage into SimDesign from the file mechanisms/fourbar.sim.
This mechanism has three moving links. Two of them are pinned to the frame, which is not shown in this picture. In SimDesign, you can nail these two links to the background.
How many degrees of freedom (DOF) does this mechanism have? If it has one, you can impose one constraint on the mechanism for it to have definite motion. For example, you can pull the nailed link on the left (making it the input link) and it will turn around the nail. The right link (now the output link) will make an oscillating motion. Suppose you put a pen on the top of the triangle-shaped link. (The triangle is also called a link. A link is not necessarily a simple line-shaped body). The pen will trace its path. The triangle-shaped link connects the two moving pivots and couples the input and the output motion; hence, it is called coupler.
Linkages have different functions. The functions are classified depending on the primary goal of the mechanism:
Function generation: the relative motion between the links connected to the frame,
Path generation: the path of a tracer point, or
Motion generation: the motion of the coupler link.
1.1.1 Crane
An application of path generation is a crane in which an approximate horizontal trace is needed.
1.1.2 Hood
An example of motion generation is a hood which opens and closes.
1.1.3 Parallelogram mechanism
In a parallelogram four-bar linkage, the orientation of the coupler does not change during the motion. The figure illustrates a loader.
1.2 Slider-crank mechanisms
The four-bar mechanism has some special configurations created by making one or more links infinite in length. The slider-crank (or crank and slider) mechanism shown below is a four-bar linkage with a slider replacing an infinitely long output link.
Pull the crank of this mechanism and you will see that it transfers rotary motion into translation. Most mechanisms are driven by motors, and slider-cranks are often used to transform rotary motion into linear motion.
1.2.1 Crank and piston
You can also use the slider as the input link and the crank as the output link. In this case, the mechanism transfers translational motion into rotary motion. The pistons and crank in an internal combustion engine are an example of this type of mechanism. The corresponding SimDesign file is mechanisms/combustion.sim.
You might wonder why there is another slider and a link on the left. This mechanism has two dead points. The slider and link on the left help the mechanism to overcome these dead points.
1.2.2 Block feeder
One interesting application of slider-crank is the block feeder. The SimDesign file can be found in mechanisms/block.feeder.sim
2. Cam mechanisms
Linkages, while useful, cannot achieve all possible motions. For example, if the output link must remain stationary for a certain period of time while the input link keeps turning, linkages cannot be used. Cam mechanisms can realize any required output motion. The composition of a cam mechanisms is simple: a cam, a follower and a frame. (You may find springs used in a cam mechanism to keep the follower and the cam in contact, but it is not part of the cam mechanism.)
2.1 Rotating cam/Translating follower
If you turn the cam, the follower will move. The weight of the follower keeps them in contact. This is called a gravity constraintcam.
2.2 Rotating cam/Rotating follower
The SimDesign file is mechanisms/cam.oscillating.sim. Notice that a roller is used at the end of the follower. In addition, a spring is used to maintain the contact of the cam and the roller.
If you try to calculate the degrees of freedom (DOF) of the mechanism, you must imagine that the roller is welded onto the follower because turning the roller does not influence the motion of the follower.
3. Gears
There are many kinds of gears. The following examples are involute spur gears. We use the word involute because the contour of gear teeth curves inward. There are many terminologies, parameters and principles for gears. One of the important concept is the velocity ratio, which is the ratio of the rotary velocity of the driver gear to that of the driven gears.
The number of teeth in these gears are 15 and 30, respectively. If the 15-tooth gear is the driving gear and the 30-teeth gear is the driven gear, their velocity ratio is 2.
An example of a set of gears is in mechanisms/gear10.30.sim.
3.1 Rack and pinion
When the number of teeth of a gear becomes infinite, the center of the gear goes to infinity. The gear becomes a rack. The following picture shows a rack and pinion. The corresponding SimDesign file is mechanisms/gear.rack.sim.
You can pull the pinion so that it turns and drives the rack. You can also pull the rack along the guide and drive the pinion.
3.2 Ordinary gear trains
Gear trains consist of two or more gears that transmit motion from one axis to another. Ordinary gear trains have axes, relative to the frame, for all gears comprising the train.
3.3 Planetary gear train
The SimDesign file is mechanisms/gear.planet.sim. Since the sun gear (the largest gear) is fixed, the DOF of the above mechanism is one. When you pull the arm or the planet, the mechanism has a definite motion. If the sun gear isn't frozen, the relative motion is difficult to control.
4. Miscellaneous mechanisms
4.1 Ratchet mechanism
A wheel with suitably shaped teeth, receiving an intermittent circular motion from an oscillating member, is a ratchet wheel. The figure below shows a simple ratchet mechanism.
A is the ratchet wheel, and B is an oscillating link. Attached to B is a pawl which is a link designed to engage with the ratchet teeth to prevent the wheel from moving in one direction. This mechanism has a supplementary pawl at D. When the link B moves in a counterclockwise direction, the pawl C pushes the wheel through a partial rotation. When the link B moves clockwise, the pawl C slides over the points of the teeth while the wheel remains at rest because of the fixed pawl D. The amount of backward motion possible varies with the pitch of the teeth. The smaller the teeth, the smaller the backward motion. The contact surfaces of wheel and pawl should be inclined so they don't disengage under pressure.
The corresponding SimDesign file is mechanisms/ratchet.sim. The four-bar linkage on the right generates an oscillating rotation for link B. Pull the crank to watch the ratchet work.
4.2 Geneva Wheel
An interesting example of intermittent gearing is the Geneva Wheel.
In this mechanism, for every turn of the driver wheel A, the driven wheel B makes a quarter turn. The pin, attached to driver wheel A, moves in the slots causing the motion of wheel B. The contact between the lower part of driver A with the corresponding hollow part of wheel B, retains it in position when the pin is out of the slot. Wheel A is cut away near the pin as shown, in order to provide clearance for wheel B as it moves. If one of the slots is closed, A can make less than one revolution in either direction before the pin strikes the closed slot, stopping the motion. Early watches, music boxes, etc., used Geneva wheels to prevent over winding. From this application, they also are called Geneva Stops. As a stop, wheel A is fastened to the spring shaft, and B turns on the axis of the spring barrel. The number of slots in B depends upon the number of times the spring shaft should be turned.
The SimDesign file for Geneva wheel is "geneva.sim".
You may try this mechanism by pulling on the Geneva wheel.
Complete Table of Contents
1. Linkage mechanisms
1.1 Four bar linkages
1.1.1 Crane
1.1.2 Hood
1.1.3 Parallelogram mechanism
1.2 Slider-crank mechanisms
1.2.1 Crank and piston
1.2.2 Block feeder
2. Cam mechanisms
2.1 Rotating cam/Translating follower
2.2 Rotating cam-rotating follower
3. Gears
3.1 Rack and pinion
3.2 Ordinary gear trains
3.3 Planetary gear train
4. Miscellaneous mechanisms
4.1 Rachet mechanism
4.2 Geneva Wheel
http://www.cs.cmu.edu/~sfinger/home.html
SLIDER CRANK MECHANISM:.
Crank:.:
A side link which revolves relative to the frame is called a cran
Slider-Crank Mechanism:.
A four-bar linkage with output crank and ground member of infinite length
working:.
A slider crank is most widely used to convert reciprocating or linear motion to rotary motion or to convert rotary to reciprocating motion.
Dead centers:.
Positions at which slider motion reverses are called dead centers.
Crankshaft:.
When crank and connecting rod are extended in a straight line and the slider is at its maximum distance from the axis of the crankshaft,the position is top dead center (TDC); when the slider is at its minimum distance from the axis of the crankshaft, the position is bottom dead center.
Appliction.:.
The slider crank mechanism is used in internal combustion engines.
Block feeder
Crank and piston
You can also use the slider as the input link and the crank as the output link. In this case, the mechanism transfers translational motion into rotary motion. The pistons and crank in an internal combustion engine are an example of this type of mechanism.
HOW WIND TURBINES WORK:.
Wind:.
Wind is a form of solar energy.
Cause of Wind:.
Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth.
WIND TURBINE:.
Principle of Wind Energy:.
The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy of the wind into mechanical power.
Use:.
This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.
How Do Wind Turbines Make Electricity?
Principle:.
Wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity.
Working:.
The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.
View Of Wind Power Plant:.
Inside View Of Wind Turbine:.
Measures the wind speed and transmits wind speed data to the controller.
2: Blades:
Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate.
3: Brake:
A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies.
4: High-speed shaft:.
Drives the generator.
5: Low-speed shaft:.
The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.
6: Rotor:
The blades and the hub together are called the rotor.
END:.
How Gasoline and Diesel can work together;
When we use the combination of diesel and gasoline
the results are impressive.
1: An average 20% greater fuel efficiency.
2: Combustion temperatures reduced by up to 40%.
1:Working:.
Because it’s less reactive and won’t burn so easily, gasoline could normally never fuel a diesel engine.
the fuel-injected diesel becomes a kind of liquid spark plug, providing a kick-start for ignition.
a heavily-laden truck might require a mix as high as 85% gasoline to 15% diesel, while a light load would require a roughly 50-50 blend.
First:.> the combustion temperatures were reduced by as much as 40%, meaning far less energy was lost from the engine through heat transfer.
Second:.>the customized fuel mix optimized combustion, with less unburned fuel lost in the exhaust and fewer emissions.
Third:.> In combination, these helped the test engine achieve a best result of 53% thermal efficiency.
3:Thermal efficincy:.
Thermal efficiency, basically, measures the percentage of fuel converted into power,and not lost in heat transfer or exhaust.
4:Best diesel engine:.
The most fuel-efficient diesel engine in the world can only achieve a best figure of 50%.
5:Working:.
It will work just as well with the low-pressure fuel injection of gasoline engines as with diesel’s high-pressure valves. And, because gasoline engines average only 25% thermal efficiency, the potential for fuel economy is even greater.
6:Applications:.
If every gasoline and diesel engine in the U.S. converted to this blended fuel process – and achieved an overall thermal efficiency of 53% - oil consumption would reduce by about 4 million barrels a day, a little under a third of today's current consumption.
REACTION TURBINE AND ELECTRIC GENERATOR ;
The runner of the small water turbineA water turbine is a rotary engine that takes energy from moving water.
Water turbines were developed in the nineteenth 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.
Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow.
Newton's third law describes the transfer of energy for reaction turbines.
Most water turbines in use are reaction turbines and are used in low (<30m/98ft) and medium (30-300m/98-984ft)head applications. In reaction turbine pressure drop occurs in both fixed and moving blades.
Impulse turbines
Impulse turbines change the velocity of a water jet. The jet impinges on the turbine's curved blades which change the direction of the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.
Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a housing for operation.
Newton's second law describes the transfer of energy for impulse turbines.
Impulse turbines are most often used in very high (>300m/984ft) head applications .
- HYDOGEN ENGINES:
Hydrogen engines will be replacing gasoline powered engines in automobiles. The question is when. Hydrogen engines come in two varieties, electric engines powered directly by hydrogen fuel cells and those engines that are converted from traditional gasoline powered combustion engines and powered by compressed hydrogen. The natural transitional vehicle, on a consumer level, most likely will be to have a car that has a hydrogen engine that has been converted from a gasoline powered engine and is fueled by pressurized hydrogen Hydrogen-fueled internal combustion engines (H2ICEs) as they are called will most likely hit the consumer market first. For the long-term, though, fuel cell driven engines will become the standard within the next 10 years.
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This "transitional" hydrogen H2ICE engine is already taking hold as both Mazda and BMW have introduced into limited production "dual-fuel" engines. With the flip of a switch, each car can switch back and forth between gasoline and hydrogen fuel. The Mazda RX-8 uses a RENESIS Hydrogen Rotary Engine, which is ideally suited to burn hydrogen without inviting the backfiring that can occur when hydrogen is burned in a traditional piston engine. Twin hydrogen injectors and a separate induction chamber help maintain safer temperatures with the hot running hydrogen fuel
This can be achieved by using piezoelectric materials under busy roads. The property is aptly known as piezoelectricity and it's the ability to produce electric power in response to applied mechanical stress, and in this case this stress is the movement of vehicles on the roads. The concept was originally developed by Innowattech and now the company is laying down a sort of test road in Israel. Is it a solution to the global energy and environment crisis? It could very well be.
Bacteria are one of the most abundant organisms on the planet and also one of the most studied. Today, scientists use bacteria for genetics research, antibiotics, and yes! Even biofuels. Recent technological advances have made a battery running on bacteria a reality. Known as microbial fuels cells or MFCs, batteries running on bacteria and other microbes have been keenly researched by scientist for decades.
Turbine & Tailrace
The Inclined Plane was powered by using water from the upper level of the canal to run a huge Reaction Turbine located in a chamber beneath the powerhouse. This powerful machine could move the wheeled cradle car and Canal Boat loaded with 70 tons of coal, from a dead stop, up the plane, over the summit and down into the upper level of the canal. Once used, water was carried away from the turbine chamber in a Tailrace Tunnel that led back into the canal at the bottom of the plane. From the powerhouse, the Plane Tender controlled the operation by adjusting the speed of the turbine and tightening a brake on the cable winding drum shaft. At Plane 9 West, boats were raised or lowered 100 vertical feet in about 15 minutes.
Water was brought to the powerhouse from the upper level of the canal in a headrace flume that ended just behind the building at the level of the second floor. A valve allowed the water to be dropped about 50 feet through a penstock pipe to the turbine chamber and up into the turbine from below. Jets of water from the turbine rotor’s four curved nozzles force it to turn at approximately 67 RPM. A drive shaft attached to the rotor was geared to the cable winding drum in the powerhouse overhead.
Turbine & Tailrace
The Inclined Plane was powered by using water from the upper level of the canal to run a huge Reaction Turbine located in a chamber beneath the powerhouse. This powerful machine could move the wheeled cradle car and Canal Boat loaded with 70 tons of coal, from a dead stop, up the plane, over the summit and down into the upper level of the canal. Once used, water was carried away from the turbine chamber in a Tailrace Tunnel that led back into the canal at the bottom of the plane. From the powerhouse, the Plane Tender controlled the operation by adjusting the speed of the turbine and tightening a brake on the cable winding drum shaft. At Plane 9 West, boats were raised or lowered 100 vertical feet in about 15 minutes.
Water was brought to the powerhouse from the upper level of the canal in a headrace flume that ended just behind the building at the level of the second floor. A valve allowed the water to be dropped about 50 feet through a penstock pipe to the turbine chamber and up into the turbine from below. Jets of water from the turbine rotor’s four curved nozzles force it to turn at approximately 67 RPM. A drive shaft attached to the rotor was geared to the cable winding drum in the powerhouse overhead.
TURBINE:
A turbine with blades arranged to develop torque from gradual decrease of steam pressure from inlet to exhaust.
The Encyclopedia Americana: A Library of Universal Knowledge (1920)
"In the reaction turbine all parts are filled with moving water, while in the impulse ... A reaction turbine is driven by the dynamic pressure of the water, ..."
Steam Power Plant Engineering by George Frederick Gebhardt (1917)
"In the Westinghouse compound turbine the high-pressure element is practically a typical single-cylinder reaction turbine and the low- pressure element is a ..."
3. Hydraulics by Robert Long Daugherty (1919)
"CHAPTER XIV THEORY OF THE reaction turbine 141. Introductory Illustration.—The reaction turbine is so called because an important factor in its operation is ..."
4. Water Power Engineering: The Theory, Investigation and Development of Water by Daniel Webster Mead (1908)
"Graphical Relation of Energy and Velocity in reaction turbine. — The relations of the changes in velocity and in energy in the passage of water through a ..."
5. Treatise on Hydraulics by Mansfield Merriman, Thaddeus Merriman (1916)
"In a reaction turbine, however, the velocity of the entering water may be ... This is due to thc fact that in a reaction turbine the static pressure of the ..."
6. A Text-book on Hydraulics: Including an Outline of the Theory of Turbines by Leander Miller Hoskins (1906)
"The fundamental characteristic of a reaction turbine is the fact that the ... The general arrangement of a reaction turbine with radial outward flow (the ..."
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