Fully hermetic Stirling engine concept
An idea for this engine appears when I tried to eliminate friction in power cylinder of an engine. Any builder knows that friction is a big problem with low power density engines. Common solution for this is a pressurized crankcase, preferably with included alternator. But this solution led to high volume of pressurized gaz. This results as big weight and danger. For gamma engine a diaphragm is a known solution. We all watched rubber diaphragm on thin-can models. But there are another reciprocating motion: the displacer rod. If we use some clearance we can not pressurize the engine, if we use a sealing we have friction and wearing and (probably) heating of the sealing by friction loses. It is not merry situation for a cheap engine. My next thought was to transfer reciprocating motion through another diaphragm, but this led to pressure disturbance. The solution is in the ONE diaphragm. A diaphragm can not only roll up, but it can tilt! Then classic roll motion can be used for volume change (as a working piston) and light tilt can simultaneously transfer a motion to the displacer. This solution eliminates most of the friction loses. Some loses remain in displacer, but it can be made vertical and with clearance on guidance ring. On the market there are a good offer for diaphragms: trucks brakes. They have a roll deformation about 40-50mm and effective area from 12 to 24 square inch (example: Type 16). Type 16 diaphragm can displace up to 450cc of gas. Classic brake diaphragm withstand up to 8.5 bar of air pressure. I think in real engine not more 4-6 bar, but this is common for conventional air compressors. Advantages of this concept: 1. fully hermetic 2. low friction 3. simplicity 4. inexpensive 5. Helium can be used freely Disadvantages 1. Can not be achieved high pressure (more than 6 bar) 2. Probably heating of the diaphragm by pressure effects 3. Probably fast wearing on high RPM 4. High static load on a crank -- starting problem 5. Only gamma configuration (alpha and beta are impossible) 6. Additional dead volume of inside driving parts and cavities. The first three problems can be solved by creating a special diaphragm from silicone and reinforced with Kevlar or carbon fibers. High static load can be eliminated by using twin design or by static spring or another diaphragm. 5 and 6 disadvantages are essential and can't be solved. I see a destination of the engine and the driving mechanism as a cheap and not hi-power engines for DIY environment, models, some solar application with mirrors from 1 to 2 meters, domestic uses with ovens for supply electronics. I estimate the power of 1 unit from 100 to 300 wt depending on pressure, rpm and diaphragm diameter (hot temperature 600C). Twin design will be about 0.5 kw. If someone want to try it please contact me. I will help.
An idea for this engine appears when I tried to eliminate friction in power cylinder of an engine. Any builder knows that friction is a big problem with low power density engines. Common solution for this is a pressurized crankcase, preferably with included alternator. But this solution led to high volume of pressurized gaz. This results as big weight and danger. For gamma engine a diaphragm is a known solution. We all watched rubber diaphragm on thin-can models. But there are another reciprocating motion: the displacer rod. If we use some clearance we can not pressurize the engine, if we use a sealing we have friction and wearing and (probably) heating of the sealing by friction loses. It is not merry situation for a cheap engine. My next thought was to transfer reciprocating motion through another diaphragm, but this led to pressure disturbance. The solution is in the ONE diaphragm. A diaphragm can not only roll up, but it can tilt! Then classic roll motion can be used for volume change (as a working piston) and light tilt can simultaneously transfer a motion to the displacer. This solution eliminates most of the friction loses. Some loses remain in displacer, but it can be made vertical and with clearance on guidance ring. On the market there are a good offer for diaphragms: trucks brakes. They have a roll deformation about 40-50mm and effective area from 12 to 24 square inch (example: Type 16). Type 16 diaphragm can displace up to 450cc of gas. Classic brake diaphragm withstand up to 8.5 bar of air pressure. I think in real engine not more 4-6 bar, but this is common for conventional air compressors. Advantages of this concept: 1. fully hermetic 2. low friction 3. simplicity 4. inexpensive 5. Helium can be used freely Disadvantages 1. Can not be achieved high pressure (more than 6 bar) 2. Probably heating of the diaphragm by pressure effects 3. Probably fast wearing on high RPM 4. High static load on a crank -- starting problem 5. Only gamma configuration (alpha and beta are impossible) 6. Additional dead volume of inside driving parts and cavities. The first three problems can be solved by creating a special diaphragm from silicone and reinforced with Kevlar or carbon fibers. High static load can be eliminated by using twin design or by static spring or another diaphragm. 5 and 6 disadvantages are essential and can't be solved. I see a destination of the engine and the driving mechanism as a cheap and not hi-power engines for DIY environment, models, some solar application with mirrors from 1 to 2 meters, domestic uses with ovens for supply electronics. I estimate the power of 1 unit from 100 to 300 wt depending on pressure, rpm and diaphragm diameter (hot temperature 600C). Twin design will be about 0.5 kw. If someone want to try it please contact me. I will help.