ref question from Joliste
why were the Olympus 593 s so smoky to start with, did they use excess fuel to help with cooling as some petrol engines do or was there some design feature which caused the smoke. It seeems to have been cured in later engines
rod
As I was working my way from 1 to 85 I read the above which reminded of a paper I filed 35 years ago:
"Development of Pollution Controls for Rolls-Royce RB211 and Olympus 593 Engines" by A B Wassall. I have picked out stuff relevant to the question:
The engines of the day generated smoke in the primary zone and partially consumed it in the rest of the combustor.
It was easier to reduce the production than increase the consumption but leaning the primary zone had an adverse effect on relight capability which then needed its own corrective action as was done on the 211. Metal temperatures went up with the leaning (as intimated by Joliste)
The 593 did not have the leaning option as it had to maintain an over-rich primary zone at TO to ensure an adequate weak extinction margin when throttled back at completion of supersonic cruise when the combustor had to operate at A/F ratios over 180.
In addition to the smoke problem the combustor weight and pressure loss had to be reduced.
These other two requirements led to the annular combustor and vaporizers which also reduced the smoke substantially. These three benefits were expected based on Pegasus experience.