PASCO Specialty & Mfg. SE-8576A User's Manual
Contents
1. the PASCO catalog Copyright The PASCO scientific 012 06870B Low Delta T Stirling Engine Instruction Sheet is copy righted with all rights reserved Permission is granted to non profit educational institutions for reproduction of any part of this manual providing the reproductions are used only in their laboratories and classrooms and are not sold for profit Reproduction under any other circumstances without the written consent of PASCO scientific is prohibited Trademarks PASCO and PASCO scientific are trade marks or registered trademarks of PASCO scientific in the United States and or in other countries All other brands products or ser vice names are or may be trademarks or service marks of and are used to identify products or services of their respective owners For more information visit www pasco com legal IZEN2. PASCOE Instruction Sheet 012 06870B Low Delta T Stirling Engine SE 8576A Introduction The PASCO SE 8576A Low Delta T Stirling Engine is a jewel like engine Because of its precision components and careful construction it can operate on temperature differ ences as small as four degrees celsius 4 C For example when the room temperature is 22 2 C 72 F or cooler the heat from a warm hand is enough to power the engine Stirling engines can be very efficient with some designs attaining efficiencies up to 50 of the Carnot Cycle effi ciency The Carnot Cycle determines the maximum theoreti cal efficiency of a heat engine according to the formula temp hot temp cold emp hot efficiency where the temperature is measured in absolute degrees kelvin K or rankine Operation The Low Delta T Stirling Engine operates as follows The bottom plate of the engine along with the clear acrylic cylinder the top plate and the graphite power piston make up a sealed system When the air inside this system changes temperature so does the pressure Inside the clear acrylic cylinder is a large white foam dis placer This displacer looks like a piston but it has a 3 125 mm 1 8 inch gap around its outer edge Air never pushes on the displacer it flows around the displacer The engine can begin working when either the bottom plate or the top plate is heated or cooled to a temperature at least 4 C warmer o
3. Stirling Engine to fail to run is inadequate thermal transfer If the engine will not run try the following Put 2 5 cm 1 inch of water in the bottom of a coffee mug Heat the water until the water is boiling vigorously Care fully remove the mug from the heat source and place the engine on top of the mug Wait for 15 seconds and then gen tly spin the flywheel Try spinning the flywheel in both directions if it fails to start in a minute or so If the engine will not run when you try this test it needs to be returned for maintenance A Brief History of the Stirling Engine The Reverend Robert Stirling a minister of the Church of Scotland was troubled by some of the dangerous engines that were used at the beginning of the industrial revolution Steam engines would often explode with tragic effects to anyone unfortunate enough to be standing nearby So in 1816 he invented and patented A New Type of Air Engine with Economizer Robert Stirling realized that the engines he built would be more efficient if some of the heat that was used to warm the air for one cycle was saved and used again in the next cycle He called the device that saved the heat an economizer Today this is usually called a regenerator and is probably Robert Stirling s most important invention Hot air engines as they were initially called couldn t explode and often produced more power than the steam engines of their day The pro
4. is a very high percentage Stirling Engines Today The modern uses of Stirling engines are invisible to almost everyone There have been many research engines built in recent years but there are only three areas where Stirling engines have made a dramatic impact These are Stirling engines in submarines in cryocoolers and in science class rooms Cryogenics is the science of things that are very cold and Stirling engines can be used to produce extremely cold tem peratures It s not obvious but a Stirling engine is reversible If you warm one side and cool the other you get mechanical work out However if you mechanical work in by connect ing an electric motor for example one side will get hot and the other will get cold In a correctly designed Stirling engine the cold side will get extremely cold In fact Stirling engines used as cryocoolers have been made that will cool below 10 kelvin K Micro sized Stirling engines have been produced in large numbers for cooling infrared chips down to 80 K for use in night vision goggles and infrared cameras Since Stirling engines are so efficient an obvious question is Why doesn t my car have one Although a variety of prototype Stirling engine powered cars have been developed they have not gained popularity because that have to warm up for 30 seconds to a minute before they will move Most consumers have not been will ing to wait that long to get started The low gas prices
5. ON N Y COLD AIR l HEATING HOTAIR h A l 6666666666666 x T a COOLING Graphite power piston 04666666666066 EXPANSION 0664600666666006 Operation of a displacer type Stirling Engine Usage Place the Low Delta T Stirling Engine on the palm of your ward hand with the label toward you After the engine has warmed up for a couple of minutes gently spin the flywheel in a clockwise direction to get it started NOTE Hand temperatures vary widely Not everyone has warm enough hands to make this engine run If your hands are cool find someone with warm hands to try this You can also run the engine in the opposite direction by plac ing the bottom plate on a cold object letting it cool down and then gently spinning the flywheel in the counterclock wise direction Maintenance e Dust is the number one enemy of this engine Cover it when it is not in use e It is a good idea to store it in a plastic case e Never oil the engine e Do not store the engine where it will be exposed to bright sunlight or the colors will fade e Handle with care The Low Delta T Stirling Engine is a delicately balanced precision engine and it is very frag ile Troubleshooting Generally there are three reasons why Stirling engines fail to run too much friction air leaks or inadequate thermal trans fer The most likely reason for the Low Delta T
6. blem was that the only readily available metal in the early 1800s was cast iron which oxi dizes rapidly when left in a very hot flame Despite this difficulty Stirling engines were widely used as water pumping engines at the turn of the century They required little service never exploded were fairly quiet and the water provided a good cooling source for the cool side of the engine Thousands of these engines were sold The Low Delta T Stirling Engine In 1983 Ivo Kolin a professor at the University of Zagreb in what was then Yugoslavia demonstrated the first Stirling engine that would run on small temperature differences After he published his work Dr James Senft a mathematics professor at the University of Wisconsin River Falls United States built the first engines similar to the PASCO Low Delta T Stirling Engine The Carnot Energy Cycle In the mid 1800s a Frenchman named Sadi Carnot figured out the maximum limits of efficiency His formula is an accepted standard for determining the maximum possible IZEIA Low Delta T Stirling Engine SE 8576A efficiency of an engine No engine can exceed the Carnot efficiency The second law of thermodynamics says you can t get out more than you put in you can only break even It takes good engineering and complex machines to achieve a significant fraction of the Carnot efficiency Real Stirling engines can reach 50 percent of the maximum theoretical value which
7. of the 1980s and 1990s did not provide an economic incentive for consumers to switch to Stirling engines and automobile companies have not had the incentive to research and develop more saleable engine designs Stirling Engines in the Future Future uses of Stirling engines could include applications in the maritime and aviation industries Stirling engines would work exceptionally well for auxiliary power generators on pleasure boats where their silence and efficiency would be value and cooling water is plentiful Some research has already been done in this area the French research subma rine Saga is Stirling engine powered Stirling engines would also work very well in airplanes where the air gets cooler as the plane climbs to altitude Stirling engines would not lose as much power as they climb as conventional piston engines or jet engines Stirling engines would operate with very low levels of vibration and noise Technical Support For assistance with any PASCO product contact PASCO at Address PASCO scientific 10101 Foothills Blvd Roseville CA 95747 7100 Phone 1 916 786 3800 worldwide 800 772 8700 U S Web Wwww pasco com Email techsupp pasco com For more information about the Low Delta T Stirling Engine and the latest revision of this Instruction Sheet go to the PASCO web site at www pasco com and enter SE 8576A in the Search window Limited Warranty For a description of the product warranty see
8. r cooler than the other plate A gentle spin on the flywheel is needed to start the engine As the foam displacer moves away from the warm side of the engine air flows around the edge of the displacer toward the warm side and is heated When the air is heated it expands which increases the pressure inside the entire engine This increase in air pressure pushes up on the graphite power pis ton Next the energy stored in the flywheel moves the displacer closer to the warm side of the engine and the air once again flows around the edge of the displacer toward the cool side of the engine When the air is cooled it contracts and the pressure drops throughout the engine The pressure inside the engine becomes less than the pressure outside and the graphite power piston is pushed down The displacer moves back toward the cool side the air is displaced toward the warm side and the cycle starts all over again IMPORTANT Do Not Oil Flywheel Crankshaft Connecting Connecting rod rod Graphite power piston Foam displacer The foam displacer only moves the air back and forth from the warm side to the cool side of the engine It does not do any work on the crankshaft In other words the connecting 800 772 8700 techsupp pasco com www pasco com Low Delta T Stirling Engine SE 8576A rod to the displacer could be a string and the engine would still work REVOLUTION CONTRACTI
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