An investigation of swirling flow mixing for application in an MHD pulverized coal combustor using isothermal modeling

The purpose of this study was to investigate combustor reactant mixing with swirling oxidizer flow. The combustor configuration that was considered was designed to simulate a 4 lbm/sec mass flow pulverized coal combustor being tested in The University of Tennessee Space Institute MHD Facility. A one-fourth dimensionally scaled combustor model was developed for isothermal flow testing. A comparison was made of cold flow tests using 3 swirler designs with a base case oxidizer injector design which demonstrated acceptable performance in the 4 lbm/sec MHD combustor.

The three swirlers that were evaluated were designed to allow a wide range of swirl intensity to be investigated. The design criterion of the swirler was the swirl number which has been related to swirler geometry.

The results of the study showed that the swirlers that were tested fell short of the mixing characteristics displayed with the base case oxidizer injector. Test data obtained with the cold flow model established that the actual swirl numbers of two of the swirlers were much lower than the design swirl numbers. Recirculation zones were defined for all configurations that were tested, and a comparison of velocity profiles was made for the configurations.

The test program proved to be a very useful phase of a large scale combustor development program. In general the test results were consistent with similar studies that were investigated by means of available literature. Although the oxidizer swirler configurations that were tested proved to be inadequate for the MHD combustor, the tests provided valuable information that can contribute to future swirler designs as well as other oxidizer and fuel injector concepts for direct application in an MHD pulverized coal combustor.