Monday, June 12, 2006
Increasing the fuel efficiency of hybrids
While most engineers are struggling to increase the fuel efficiency of cars by fractions of a percent, there is an obvious place where big gains can be made while improving handing: turning. Turning wastes about 6% of total energy used by a car, since two of the wheels have to slow down, while two speed up. (The wheels on the outside have to travel further (that is spin faster) then the wheels on the inside.) Now then some hybrids have independent drive motors for each wheel or at least the back two, if you use the regenerative braking to slow the wheels that have to go slower, you recapture some of the lost energy and the car turns better (it won’t turn like a tank (tanks can turn inside there own radius) but it should be noticeable better.) You can’t get all the wasted energy back but it should be enough to make it worth implementing (the steering improvements alone should justify the implementation.)
Sunday, June 11, 2006
SBIR solutions
Army A06-008 Advanced Inlet Protection System in Severe Sand Environments
This SBIR wants a solution for how to filter small sand and dust particles out of the air that is ingested by gas turbines.
There are a number of options but the simplest in my mind is to use the centrifugal force generated in the compressor stage to remove the fine particulates. This would entail designing the first fan to separate the fines (angular momentum of even fine particles is significantly greater then air), throw them against the housing of the turbine into a bypass. This air and the captured fines is vented into the exhaust gases after they are past all the moving parts (this cools the exhaust gases and reduces unburned material). In order to achieve this, the first fan and the bypass channel would have to be hardened since the wear caused by abrasion would be significant, but since the bypass isn’t that hot it can be lined with Silicon Carbide instead of zirconium. If properly executed the first stage filter would function like a turbofan which would increase fuel efficiency and reduce engine noise. In icing environments the bypass would be warmed by the compressed air, so it would not freeze closed, and it would reduce the amount of water and ice that is ingested into the actual compressor stage. While this engine would be limited to subsonic use the SBIR specifics the application to helicopters, sea/land-based gas turbine drive equipment.
DARPA SB062-003 High Temperature Corrosion Resistant Nanocomposite Materials for Turbine Engine Applications
This SBIR wants a way to increase the life of the thermal barrier coating (TBC) in the hot stages of the turbine engines.
This solution to this problem was inspired by the problem in the other challenge. Fine sand particles ingested by the engine melt and coat the hottest parts. Here is the key to the solution the exhaust gasses can actually be hotter then the melting point of the zirconia-based TBC, but since zirconia is such a poor conductor of heat, and the surface area so small it doesn’t melt. However, if a TBC material was extremely finely divided then ingested into the engine it would melt, and coat (or in this case recoat) the parts of the engine where particulate matter would cause the greatest wear. The nano-TBC would only be liquid till it hit a surface then would instantly freeze, and because the surface area is greatly reduced it would not remelt. While it is in theory possible to recoat the entire hot stage of the engine by controlling the amount of bypassed air to keep the nano-TBC particles liquid longer, and monitoring the deposition of new material as a function of shaft power, it is not practical. The best use of the method is to apply the thinnest possible coat of new material (just enough to fill micropits and other small defects in the TBC) since this increases the life of the plasma deposited coating with minimal risk of damage.
Even if in line recoating of the TBC proves impossible it is still possible to clean the engine at a molecular level using ingested compounds. This is of significant benefit since the failure of the TBC is most often caused by mixing of the TBC and the underlying metal caused by migration, or permeation of sulfur or other contaminates. Anti-migration agents or antioxidant coatings could be applied to reduce the corrosion processes and increase the life of hot stage.
This SBIR wants a solution for how to filter small sand and dust particles out of the air that is ingested by gas turbines.
There are a number of options but the simplest in my mind is to use the centrifugal force generated in the compressor stage to remove the fine particulates. This would entail designing the first fan to separate the fines (angular momentum of even fine particles is significantly greater then air), throw them against the housing of the turbine into a bypass. This air and the captured fines is vented into the exhaust gases after they are past all the moving parts (this cools the exhaust gases and reduces unburned material). In order to achieve this, the first fan and the bypass channel would have to be hardened since the wear caused by abrasion would be significant, but since the bypass isn’t that hot it can be lined with Silicon Carbide instead of zirconium. If properly executed the first stage filter would function like a turbofan which would increase fuel efficiency and reduce engine noise. In icing environments the bypass would be warmed by the compressed air, so it would not freeze closed, and it would reduce the amount of water and ice that is ingested into the actual compressor stage. While this engine would be limited to subsonic use the SBIR specifics the application to helicopters, sea/land-based gas turbine drive equipment.
DARPA SB062-003 High Temperature Corrosion Resistant Nanocomposite Materials for Turbine Engine Applications
This SBIR wants a way to increase the life of the thermal barrier coating (TBC) in the hot stages of the turbine engines.
This solution to this problem was inspired by the problem in the other challenge. Fine sand particles ingested by the engine melt and coat the hottest parts. Here is the key to the solution the exhaust gasses can actually be hotter then the melting point of the zirconia-based TBC, but since zirconia is such a poor conductor of heat, and the surface area so small it doesn’t melt. However, if a TBC material was extremely finely divided then ingested into the engine it would melt, and coat (or in this case recoat) the parts of the engine where particulate matter would cause the greatest wear. The nano-TBC would only be liquid till it hit a surface then would instantly freeze, and because the surface area is greatly reduced it would not remelt. While it is in theory possible to recoat the entire hot stage of the engine by controlling the amount of bypassed air to keep the nano-TBC particles liquid longer, and monitoring the deposition of new material as a function of shaft power, it is not practical. The best use of the method is to apply the thinnest possible coat of new material (just enough to fill micropits and other small defects in the TBC) since this increases the life of the plasma deposited coating with minimal risk of damage.
Even if in line recoating of the TBC proves impossible it is still possible to clean the engine at a molecular level using ingested compounds. This is of significant benefit since the failure of the TBC is most often caused by mixing of the TBC and the underlying metal caused by migration, or permeation of sulfur or other contaminates. Anti-migration agents or antioxidant coatings could be applied to reduce the corrosion processes and increase the life of hot stage.
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