Elan Vital
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Hi everyone,
I have recently been delving in all sorts of propulsion related websites, and recently found a database from the French company Safran, which among other things had documents on the work done by the company Hispano Suiza for tank engines, namely the HS-110 powering the AMX-30 and the HS-115 powering the AMX-10P and early RC (as well as the HS-103 used for all sorts of applications).
The rather unusual feature of these engines is the presence of a turbulence (swirl) combustion chamber patented by Hispano Suiza. This had been developped in the late 50s for the American company Hercules to turn diesel engines into multifuels. The report will explain this better than I can, but the gist of it is that it's an hemispheric combustion chamber which improves fuel mixing and allows better performance than the direct injection of the time. Main advantages being: cleaner exhaust, ability to turn into multifuel system by changing some materials, reduced injector servicing, better high speed performance (flatter torque curve mainly) and higher BMEP.
In the mid 1960s, Hispano Suiza would attempt to improve on the turbulence chamber as the present designs had high compression ratios (19.5 to 21), limiting potential for high turbocharging. The solution was the CAPC, or Variable Volume Combustion Chamber or Constant Pressure Combustion Chamber. This is conceptually related to VCR engines in that the compression ratio can be varied (from 12 to 19), which allows high turbocharging at high loads (where compression ratio will be reduced). However, it is the upper part of the chamber itself which changes, rather than the piston. It is possible, in my opinion, that the CAPC was possibly easier to get right than VCR, although it might not have allowed the same level of improvement.
Core benefits of the CAPC are even cleaner exhaust, significant reduction in fuel consumption, and massive increase in specific power. Indeed the French would test a HS-115 with such a system under the name HS-115-3 or HS-116, getting a whopping 400hp instead of 260, with experiments with improved turbocharging and NATO reliability trials being performed in 1969/70. The HS-110, if it could achieve the same power density could have got 1200hp instead of 680-720. Sadly my knowledge goes no further for a lack of the necessary archives (which are at Châtellerault). However, the presentation from Hispano Suiza indicates that better compact turbochargers would be needed to get the necessary boost to achieve these power densities in AFVs, so it certainly wasn't gonna mature until the 1970's. In any case, a sad and still mysterious death for what could have been the potential French tank engine of the 1980s.
The link to the Safran Database if you ever want to have a look: https://heritage.medialibrary.safran-group.com/Heritage/search.do?q=hs&page=5I have recently been delving in all sorts of propulsion related websites, and recently found a database from the French company Safran, which among other things had documents on the work done by the company Hispano Suiza for tank engines, namely the HS-110 powering the AMX-30 and the HS-115 powering the AMX-10P and early RC (as well as the HS-103 used for all sorts of applications).
The rather unusual feature of these engines is the presence of a turbulence (swirl) combustion chamber patented by Hispano Suiza. This had been developped in the late 50s for the American company Hercules to turn diesel engines into multifuels. The report will explain this better than I can, but the gist of it is that it's an hemispheric combustion chamber which improves fuel mixing and allows better performance than the direct injection of the time. Main advantages being: cleaner exhaust, ability to turn into multifuel system by changing some materials, reduced injector servicing, better high speed performance (flatter torque curve mainly) and higher BMEP.
In the mid 1960s, Hispano Suiza would attempt to improve on the turbulence chamber as the present designs had high compression ratios (19.5 to 21), limiting potential for high turbocharging. The solution was the CAPC, or Variable Volume Combustion Chamber or Constant Pressure Combustion Chamber. This is conceptually related to VCR engines in that the compression ratio can be varied (from 12 to 19), which allows high turbocharging at high loads (where compression ratio will be reduced). However, it is the upper part of the chamber itself which changes, rather than the piston. It is possible, in my opinion, that the CAPC was possibly easier to get right than VCR, although it might not have allowed the same level of improvement.
Core benefits of the CAPC are even cleaner exhaust, significant reduction in fuel consumption, and massive increase in specific power. Indeed the French would test a HS-115 with such a system under the name HS-115-3 or HS-116, getting a whopping 400hp instead of 260, with experiments with improved turbocharging and NATO reliability trials being performed in 1969/70. The HS-110, if it could achieve the same power density could have got 1200hp instead of 680-720. Sadly my knowledge goes no further for a lack of the necessary archives (which are at Châtellerault). However, the presentation from Hispano Suiza indicates that better compact turbochargers would be needed to get the necessary boost to achieve these power densities in AFVs, so it certainly wasn't gonna mature until the 1970's. In any case, a sad and still mysterious death for what could have been the potential French tank engine of the 1980s.
Link to the article (in French) on the CAPC since it is too big for the forum: https://heritage.medialibrary.safra...12930257/Kup7ikoojEKqcxxr/SAF2012_0049033.pdf
