Experimental and Theoretical Study on Spray Angles of Bi-Swirl Coaxial Injectors


School of Mechanical Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea


An experimental and theoretical study was undertaken to investigate the effects of the recess length, swirl direction, and mixture ratio on the spray angles of the bi-swirl coaxial injectors with the inner, closed-type and outer, open-type swirl injectors. Eight bi-swirl coaxial injectors with a range of recess lengths and different swirl directions between the inner and outer swirl injectors were used. As the recess length was increased, each bi-swirl coaxial injector exhibited external-mixing, tip-mixing, or internal-mixing spray characteristics. To measure the spray angles, cold-flow tests for which the mass flow rates of the two injectors were varied were performed to capture the spray images. The single-injection results indicated that the spray cone angles of both the inner and outer swirl injectors were relatively unaffected by the mass flow rate and the swirl direction, with the recess length influencing the spray cone angles of the inner swirl injectors. The bi-injection tests show that the spray angles are significantly dependent on the recess length and the mixture ratio, while also being affected by the swirl direction, especially regarding the internal-mixing bi-swirl coaxial injectors. Theoretical models that can predict the spray angles were developed and compared using the experimental data. The theoretical models could approximate the combined spray angles of the internal-mixing bi-swirl coaxial injectors.