Study on the atomization and vaporization characteristics of kerosene with dual-stage counter-rotating nozzle

Abstract

To achieve low NOx emissions in the combustor, a dual-stage counter-rotating nozzle based on lean direct injection was designed. The investigation of kerosene atomization and vaporization using this nozzle contributes to optimizing its structure and enhancing its practical applications. In this study, experiments were conducted to measure droplet size and velocity profiles. Large eddy simulations were performed to analyze velocity, droplet size, and kerosene distribution in a high-temperature environment (770 K, 205.2 kPa). The results demonstrate that droplet size increases with both radial and axial distances. The dual-stage counter-rotating swirler reduces droplet size, enhances heat transfer, accelerates vaporization, and improves kerosene uniformity. Increasing the inner blade angle results in a wider atomization cone and smaller droplet sizes. At outer blade angles of 35° or 40°, the spray cone fails to form. Vaporization occurs most rapidly at an inner blade angle of 45°, taking 33.1 ms. Increasing the inner-to-outer air flow rate ratio expands droplet distribution, enhances heat transfer, and accelerates vaporization. As the ratio increases from 1:3 to 3:1, the vaporization time decreases from 47.5 to 32.8 ms. Additionally, increasing the air flow rate strengthens droplet breakup, further reducing droplet size and accelerating vaporization. As the total air flow rate increases from 4.2 to 8.4 g·s⁻¹, the vaporization time decreases from 37.9 to 32.1 ms. The study identifies the optimal parameters as a 40° inner blade angle, a 45° outer blade angle, and a 3:1 inner-to-outer air flow rate ratio, which reduce droplet diameter, enhance vaporization rate, and improve kerosene dispersion.