Abstract
Aerodynamic measurement of combustion temperature relies upon measurement of the total-to-static pressure ratio across the combustor exhaust nozzle, and simul taneous measurement of the weight flow. Combustion efficiency computed from this temperature expresses jet propulsion performance characteristics of the combustor, subject to both systematic and random errors. The sources and magnitudes of these errors are examined, as a key to estimation of reliability of combustion efficiency values. Care must be taken to avoid certain potential systematic errors, but in most instances corrections can be made which themselves do not introduce appreciable ran dom errors. With such care and with reasonably refined instrumentation, the major source of random error is the evaluation of nozzle exit Mach number. The resulting probable error in combustion efficiency, expressed as either a temperature rise ratio or a ratio of fuel/air ratios to com pare theoretical and actual performance, is in the neigh borhood of ±5 per cent. When development of thrust for jet propulsion is the point of interest, this is reasonable reliability, considerably less doubtful than offhand esti mates which are often made to provide conservative views.
Published Version
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