Turbulent Mixing and Reacting Flow Characterization

Morgenthaler, J. H.

doi:10.1115/1.3448143

Cited by 1 publication

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“…A number of other studies which deal with the analysis and modeling of jet mixing include Morgenthaler (1975), A1 Taweel and Landau (1977), and Danon et al (1977). Yuu et al (1978) have developed a model for particle-gas dispersion.…”

Section: Introductionmentioning

confidence: 98%

Cold flow mixing rates in confined, recirculating coaxial jets with angular secondary injection

Hedman¹,

Leavitt²,

Sharp³

1985

AIChE Journal

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The mixing of gases and particles in confined, coaxial jets with angular secondary steam injection into suddenly expanded mixing chambers was studied. The effects of secondary stream injection angle, mixing chamber diameter and length, primary jet solids loading, particle size, and secondary stream velocity on particle and gas mixing rates were determined. Gas mixing was much faster than particle mixing. Angular secondary injection significantly increased the initial gas and particle mixing rates but had little effect on the overall length of duct needed for complete mixing. The effects on initial gas mixing rate of combined angular secondary injection and increased secondary velocity were additive. SCOPEAn understanding of the mixing characteristics of gases and particles is important if the complex processes involved in pulverized coal combustion or entrained coal gasification processes are to be fully understood. The mixing of gases and finely divided powder in confined, nonreactive, coaxial jets has been studied at this laboratory as part of an overall program to develop an understanding of the complex fluid dynamic processes involved in the combustion or gasification of pulverized coal, but without the complications of the chemical reactions. The cold flow work has been an integral part of several studies that have involved pulverized coal combustion (Smoot et al., 1982), entrained coal gasification (Hedman et al., 1981), and the development of sophisticated computer codes to describe these complex processes Fletcher, 1983).The objective of this study was to collect jet mixing data in a particular geometry that has important application in entained flow reactors but that has been ignored in previous studies. The data are useful in determining the effect of various operating variables on gas and particle mixing rates and in providing a set of specific local data that can be compared directly to computer code predictions, thus providing a way of validating the computer codes being developed in companion research programs.This study reports gas and particle mixing data obtained in confined, coaxial jets with angular secondary injection into a suddenly expanded mixing chamber. Flow conditions simulated operating conditions of pulverized coal combustors and entained coal gasifiers. The effects of secondary stream injection angle, mixing chamber diameter and length, solids loading in the primary jet, particle size and type, and secondary stream velocity on particle and gas mixing rates were determined from particle mass flux and gas tracer measurements. Reciprocal core length was used to characterize the initial mixing rate. The normalized length required to achieve complete mixing was used to provide a measure of the required size of a reaction vessel. CONCLUSIONS AND SIGNIFICANCEThe test results have indicated that considerable control over initial gas and particle mixing rates can be gained by variations in inlet geometry and operating conditions. The results also show that a certain amount of independent cont...

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Section: Introductionmentioning

confidence: 98%