The validity and accuracy of performance measurements for pulse detonation engines depend on the ability toaccurately measure thrust and fuel mass flow rates during system operation. Experimental tests have revealed thatwhen fuel mass flow rates are calculated by conventional mass metering methods, incorrect values of the aggregatefuel mass in the combustor will often be calculated due to inaccurate assumptions regarding the spatial fueldistribution. The difficulty in predicting the actual fuel distribution affects the ability to achieve reliable detonationsfor successful operation and introduces inaccuracies directly into the performance calculations. Tunable diode laserand absorption spectroscopy techniques have been applied to provide time-resolved fuel mass fractionmeasurements and improve the fidelity of the specific impulse calculations. Results show that stratified fueldistributions that begin near stoichiometric at the forward end of the combustor and gradually become fuel lean nearthe combustor exit produce substantially higher specific impulse values than axially uniform fuel distributions withthe same amount of aggregate fuel due to the ability to reliably detonate while operating at an overall lean condition.Axially uniform fuel distributions at the same average equivalence ratio demonstrated lower detonability andaccordingly had lower thrust and specific impulse values.
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