Fault Mechanism and Control Method of Flow Fluctuation in Fuel Metering Unit

Fluctuation in metering fuel flow caused by instability of the pressure difference control component (PDCC) of the fuel metering unit severely threatens the speed stability of aeroengines, yet the underlying mechanism remains unclear, and effective prevention or handling methods are lacking. Based on nonlinear dynamic bifurcation theory, a new paradigm for improving PDCC stability is proposed to address these problems. The high-confidence dimensionless nonlinear model of PDCC is established, and the analytical framework of its bifurcation characteristics is designed. The third-order normal form of PDCC at the critical spool mass of the pressure difference valve is derived from the center manifold theorem and normal form theory, thereby revealing the instability mechanism of PDCC, which is validated by numerical simulation. Furthermore, the influence of a single parameter of the pressurized locking valve (PLV) on the bifurcation characteristics, along with the stability region under the coupling of two parameters, is analyzed. On this basis, the low-frequency constant-amplitude oscillation (32.8 Hz) of PDCC at an unstable operating condition is eliminated by optimizing the parameters of PLV, which proves the effectiveness of the method. The findings demonstrate that the metering flow fluctuation malfunction originates from a supercritical Hopf bifurcation, induced by improperly designed parameters, which triggers self-excited oscillation in PDCC. Analyzing the bifurcation characteristics of PDCC is essential for developing effective strategies to prevent the occurrence of supercritical Hopf bifurcation, thereby enhancing system stability.