Accession Number : AD0475934
Title : AN ENGINEERING APPROACH TO COMBUSTION INSTABILITY
Descriptive Note : Technical documentary rept.
Corporate Author : AEROSPACE CORP EL SEGUNDO CA EL SEGUNDO TECHNICAL OPERATIONS
Personal Author(s) : Dykema, Owen W
Report Date : 05 Nov 1965
Pagination or Media Count : 24
Abstract : A simplified engineering approach to the analysis of high frequency combustion instability in large liquid rocket engines is outlined. The approach stems from theoretical consideration of pressure and time dependent droplet combustion. There results a dimensionless correlating parameter, called a stability number (Ns), which essentially represents the dimensionless ratio of a characteristic molecular diffusion time to a characteristic acoustic time. Stable and unstable ranges of Ns are defined, and Ns is reduced and simplified to common, readily measurable engineering terms involving the injector orifice pattern (size and umber of orifices), the frequency of the acoustic modes, chamber pressure, and propellant flow rate. The main purpose of the report is to demonstrate the application of this approach to real engine instability problems. An example application is shown, using data from the Aerojet Gemini Stability Improvement Program. Other applications conducted over a period of five years, to a wide variety of large liquid rocket engines involving seven injector element types, four propellant combinations, and ten combustors ranging in thrust from 8,000 to 1,500,000 pounds, and in chamber pressure from 100 to 1, 100 psia, are briefly reviewed. The approach can be used with good accuracy to interpolate or extrapolate Ns to stable regions if some instability data is available and can be used (with some limitations) to generate design data for stability of a new engine.
Descriptors : *COMBUSTION , COMBUSTION CHAMBERS , DIFFUSIVITY , DROPS , FLUID FLOW , FUEL INJECTORS , FUEL SPRAYS , LIQUID PROPELLANT ROCKET ENGINES , MASS TRANSFER , MATHEMATICAL ANALYSIS , MATHEMATICAL MODELS , ORIFICES , PRESSURE , STABILITY , THRUST , VELOCITY
Subject Categories : Combustion and Ignition
Distribution Statement : APPROVED FOR PUBLIC RELEASE