Procedure for evaluating fuel composition effects on combustor life

A generalized method is presented for estimating the effects of fuel composition on liner life. This method avoids the detailed temperature and stress distribution calculations required when using conventional cyclic material property charts. The simplified approach became possible when it was found that cyclic life ratios due to fuel change were very similar when correlated with a convenient temperature parameter that had already been used in the past to correlate fuel composition with metal temperature change. This life ratio was found to be relatively independent of (1) the peak temperature existing with the base fuel, (2) the coolant temperature, and (3) the actual detailed stress calculation. A trend of increased life ratio effect at longer cyclic lives for crack initiation was found. This trend can be incorporated into life ratio estimates from the prepared curves by using the actual observed service life without the need for a calculated absolute life. (Author)