Accession Number : ADA336154

Title :   Mathematical Problems in Combustion

Descriptive Note : Final rept. 1 Dec 92-31 May 96

Corporate Author : ILLINOIS UNIV AT URBANA

Personal Author(s) : Buckmaster, John

PDF Url : ADA336154

Report Date : 24 OCT 1996

Pagination or Media Count : 7

Abstract : Acoustic instabilities in gas turbines. There are many ways, in reactive systems, in which a phase change can arise between pressure fluctuations and the induced fluctuations in heat release, to trigger acoustic instabilities via the well known Raleigh criterion. We have described a mechanism that was not previously recognized and reported this in the engineering literature, with the suggestion that it is responsible for the instability known as groaning observed in gas turbines at low speeds. The abstract of this paper is: Slip affects the response time of fuel sprays to acoustic fluctuations in a gaseous flowfield. This article describes how gaseous fuel is released by evaporation as an oscillating response to the acoustic velocity fluctuations, and so contributes to acoustic instability. This article discusses the differences due to the evaporation characteristics of various fuels (JP-4, JP-5, and D-2) as well as the effect of droplet size, inlet air temperature, air speed, and Reynolds number on mass response. For example, it is shown that instability will be driven harder at lower frequencies, higher gas velocities, and increased liquid volatility.

Descriptors :   *GAS TURBINES, *FLAMES, *JET ENGINE FUELS, PHASE TRANSFORMATIONS, FLOW FIELDS, ACOUSTIC SIGNALS, FUEL SPRAYS, EVAPORATION, ACOUSTIC VELOCITY, REYNOLDS NUMBER, RAYLEIGH TAYLOR INSTABILITY.

Subject Categories : Combustion and Ignition
      Jet and Gas Turbine Engines
      Fuels

Distribution Statement : APPROVED FOR PUBLIC RELEASE