Tucker, Paul K.

NASA Technical Reports Server

+ Several Types of Altitude-Compensating Nozzle (ACN) concepts have been studied 
over the years. 
+ The DB nozzle is one type of ACN, and is predicted to have a higher nozzle efficiency 
than a CB nozzle 
+ The DB has a distinct "Dual-Bell" shape 
How it wo rks: 
DB Mode 1 operation (low altitude) 
-Nozzle flow expands out to the end of the first bell, optimized for lower altitudes ;;,;;;;;;;; 
DB Mode 2 operation (high altitude) 
--Nozzle flow expands out to the exit plane, at the end of the second bell 
Flight Testing the Dual-Bell Nozzle 
+ Although predicted to be higher performing, the DB 
nozzle must be proven in a relevant fl ight environment 
+ Captive-carry fl ight testing will enable a more detailed investigation 
into the nozzle plume behavior and performance at several conditions 
--Captive-carry fl ight-testing will also enable the propulsion assets to 
be protected for future testing 
+ The NASA F-15B Propulsion Flight Test Fixture (PFTF) was 
developed for captive-carried fl ight tests with advanced propulsion 
systems 
--DB nozzle testing can leverage this flight-proven 
capability 
https://ntrs.nasa.gov/search.jsp?R=20140016896 2019-08-31T16:37:11+00:00Z


The Dual-Bell (DB) Nozzle

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