Experimental investigation on carbon deposition characteristics of aeroengine swirl nozzle and its effect on spray behaviors

The rapid development of aeroengines has resulted in higher thermal stress on the fuel supply system, which spans from the fuel tank to the combustion chamber. In particular, the thermal environment around the fuel nozzle is severe, which increases the possibility of carbon deposits formation. In this study, a series of fouling experimental tests is conducted on swirl nozzles which were commonly used in small-sized aeroengines to further understand the effect of deposits. Three stages of thermal loading are applied to the nozzle to simulate its actual operating condition. Nozzles with different foul levels are obtained at 1, 3, 5, and 10 h of uninterrupted operations, respectively. The spray characteristics of swirl nozzles with different fouling times and clean nozzles are compared. Furthermore, the components are analyzed via scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) to determine the morphology and composition of the deposits. As the fouling time increases, the maximum flow rate loss of the nozzle reaches 14.98%. Because the fouled nozzle cannot form a stable air core easily, the instability of spray angle and liquid film increase significantly. Amorphous deposits containing carbon and oxygen are discovered on the wetted internal wall of the nozzle. The deposits change the flow channel structure of the swirler, which is the most important factor affecting the spray performance. Based on the experimental results, methods for delaying the carbon deposition of swirl nozzles are presented.