Az üzemanyag cella laírását a bal oldali felső menűben találod meg.
Itt elfogyott a memória helyem és nem ad az Admin.
Üdv Polgár Sándor
MAI IDŐJÁRÁS ELŐREJELZÉS
Mai Időjárás
Kis Hőtérkép
Napfogyatkozás 2006 03 29
Tartalom
A szerető hivatásos intézménye
Tartalom
Térhajtómű Miguel Alcbeirre 1996
Tartalom
Térhajtómű Miguel Alcbeirre 1996
Tartalom
A Stirling motor elvéé a jövő
Two Cylinder Stirling Engine
The Stirling engine is one of my favorites. It was invented in 1816 by Rev. Robert Stirling of Scotland. The Stirling is a very simple engine, and was often billed as a safe alternative to steam (since there's no boiler to explode). It enjoyed some success in industrial applications, and in small appliances like fans and water pumps, but was eclipsed by the advent of inexpensive electric motors.3 Since it can run on any source of heat, it now holds promise for alternative fuel engines, solar power, geothermal power, etc.
Stirling engines feature a completely closed system in which the working gas (usually air but sometimes helium or hydrogen) is alternately heated and cooled by shifting the gas to different temperature locations within the system.
In the two-cylinder or alpha configured3 Stirling, one cylinder is kept hot while the other is kept cool. In the illustration the lower-left cylinder is heated by burning fuel. The other cylinder is kept cool by an air cooled heat sink (a.k.a. cooling fins).
The Stirling cycle may be thought of as four different phases: expansion, transfer, contraction, and transfer.
Expansion. At this point, most of the gas in the system has just been driven into the hot cylinder. The gas heats and expands driving both pistons inward.
Transfer. At this point, the gas has expanded (about 3 times in this example). Most of the gas (about 2/3rds) is still located in the hot cylinder. Flywheel momentum carries the crankshaft the next 90 degrees, transferring the bulk of the gas to the cool cylinder.
Contraction. Now the majority of the expanded gas has been shifted to the cool cylinder. It cools and contracts, drawing both pistons outward.
Transfer. The now contracted gas is still located in the cool cylinder. Flywheel momentum carries the crank another 90 degrees, transferring the gas to back to the hot cylinder to complete the cycle.
This engine also features a regenerator, illustrated by the chamber containing the green hatch lines. The regenerator is constructed of material that readily conducts heat and has a high surface area (a mesh of closely spaced thin metal plates for example). When hot gas is transferred to the cool cylinder, it is first driven through the regenerator, where a portion of the heat is deposited. When the cool gas is transferred back, this heat is reclaimed; thus the regenerator "pre heats" and "pre cools" the working gas, dramatically improving efficiency.3
Copyright 2000, Matt Keveney. All rights reserved.
Single Cylinder Stirling Engine
This type of Stirling engine, known as the beta configuration3, features just one cylinder with a hot end and a cool end. The working gas is transferred from one end of the cylinder to the other by a device called a displacer (here illustrated in blue). The displacer resembles a large piston, except that it has a smaller diameter than the cylinder, thus its motion does not change the volume of gas in the cylinder - it merely transfers the gas around within the cylinder.
The same four phases of the Stirling cycle are at work here:
Expansion. At this point, most of the gas in the system has just been driven to the hot end of the cylinder. The gas heats and expands driving the piston outward.
Transfer. At this point, the gas has expanded. Most of the gas is still located in the hot end of the cylinder. Flywheel momentum carries the crankshaft the next quarter turn. The bulk of the gas is transferred around the displacer to the cool end of the cylinder.
Contraction. Now the majority of the expanded gas has been shifted to the cool end. It contracts, drawing the piston inward.
Transfer. The contracted gas is still located near the cool end of the cylinder. Flywheel momentum carries the crank another quarter turn, moving the displacer and transferring the bulk of the gas back to the hot end of the cylinder.
Instead of having two pistons, a displacer-type engine has one piston and a displacer. The displacer serves to control when the gas chamber is heated and when it is cooled. This type of Stirling engine is sometimes used in classroom demonstrations. You can even buy a kit to build one yourself!
In order to run, the engine above requires a temperature difference between the top and the bottom of the large cylinder. In this case, the difference between the temperature of your hand and the air around it is enough to run the engine.
In the figure above, you can see two pistons:
The power piston - This is the smaller piston at the top of the engine. It is a tightly-sealed piston that moves up as the gas inside the engine expands.
The displacer - This is the large piston in the drawing. This piston is very loose in its cylinder, so air can move easily between the heated and cooled sections of the engine as the piston moves up and down.
The displacer moves up and down to control whether the gas in the engine is being heated or cooled. There are two positions:
When the displacer is near the top of the large cylinder, most of the gas inside the engine is heated by the heat source and it expands. Pressure builds inside the engine, forcing the power piston up.
When the displacer is near the bottom of the large cylinder, most of the gas inside the engine cools and contracts. This causes the pressure to drop, making it easier for the power piston to move down and compress the gas.
The engine repeatedly heats and cools the gas, extracting energy from the gas's expansion and contraction.
Next, we'll take a look at a two-piston Stirling engine.
Valódi krimibe illő történetet tarthatnak kezükben olvasóink a Magyar Nemzet négyrészes sorozatában, amely teljes terjedelemben olvasható az alábbiakban:
AJÁNLOM AZ OLDALT
