The characteristic time model (CTM) represents the dominant physical subprocesses related to combustor performance in terms of characteristic times. Properly formulated, these characteristic times account for variations in combustor geometry, fuel characteristics, and operating conditions. Here, a CTM for piloted–lean premixed combustor NOx emissions is used to investigate the sensitivity of NO formation in such combustors to fuel/air unmixedness and suggests an experimental method of evaluating premixed performance under fired conditions that is discussed in the companion paper.

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