Abstract
To analyze the dynamic characteristics of hammer shocks caused by engine surge, a serpentine inlet with a front fuselage is simulated under conditions of subsonic inflow and three flight angles based on the improved delayed detached eddy simulation method. An unsteady back pressure boundary condition in an aerodynamic interface plane is used to simulate the overpressure during engine surge. There is a certain angle between the normal line of the hammer shock and the centerline, which is approximately equal to the corresponding flight angle. The inlet wall pressures are above 2.3 times of the free-stream static pressure, and even local transient pressures reach more than 3 times. Complex flow field structures are generated behind the shock, which are affected by the centrifugal force and lateral pressure gradient. The velocities and intensities of the hammer shocks and the pressure distributions on the wall and the shapes of the flow field structures are greatly affected by the flight angle. In a large yaw angle, the hammer shock velocity is the fastest, and the internal airflow and load are the most severe. In particular, it is necessary to consider the influence of the ultra-high dynamic loads in the opposite direction at the two bends in a short period of time.
Highlights
Future aircraft configurations are expected to require more closely coupled propulsion and airframe architectures, which often feature convoluted inlets to deliver the airflow to the engine.1,2 Such aircrafts generally adopt an S-shaped or serpentine inlet and achieve complete shielding to the engine by changing the cross section.3,4 such aircraft configurations have weight and drag advantages, the coupling between the inlet and compressor system becomes more critical
The changes of total pressure Pt at a part of the measurement points in the serpentine inlet with time are illustrated in Fig. 7, the corresponding positions of each point have been marked in Fig. 4, and the time is intercepted to 0.13 s because most of the flow field in the inlet has been recovered at this time
The obvious threedimensional complex flow field structures are influenced by the centrifugal force and lateral pressure gradient of the two large bends
Summary
Future aircraft configurations are expected to require more closely coupled propulsion and airframe architectures, which often feature convoluted inlets to deliver the airflow to the engine. Such aircrafts generally adopt an S-shaped or serpentine inlet and achieve complete shielding to the engine by changing the cross section. such aircraft configurations have weight and drag advantages, the coupling between the inlet and compressor system becomes more critical. Future aircraft configurations are expected to require more closely coupled propulsion and airframe architectures, which often feature convoluted inlets to deliver the airflow to the engine.. Future aircraft configurations are expected to require more closely coupled propulsion and airframe architectures, which often feature convoluted inlets to deliver the airflow to the engine.1,2 Such aircrafts generally adopt an S-shaped or serpentine inlet and achieve complete shielding to the engine by changing the cross section.. Such aircrafts generally adopt an S-shaped or serpentine inlet and achieve complete shielding to the engine by changing the cross section.3,4 Such aircraft configurations have weight and drag advantages, the coupling between the inlet and compressor system becomes more critical. The overpressure in the Aerodynamic Interface Plane (AIP) is caused by engine surge, which instantly generates a shock wave that travels upstream, and it is commonly referred to as the hammer shock. The peak pressure of hammer shock in the inlet is much higher than the normal pressure, which can get up to twice the total pressure.
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