Tip clearance

About: Tip clearance is a research topic. Over the lifetime, 2637 publications have been published within this topic receiving 32671 citations.

Control of compressor surge with Active Magnetic Bearings

Abstract: The design of an active surge controller, which employs Active Magnetic Bearings (AMBs) to stabilize the flow in the compressor, is presented in this paper. The axial tip clearance of an unshrouded centrifugal impeller from a single stage compressor is modulated relative to the static shroud to induce a pressure variation in the compressor output pressure. This fast-response, high-precision control of the output pressure is employed to stabilize the compressor operating in surge condition. The control law for the tip clearance is derived based on a recently introduced mathematical model, and the performance of the controller is tested through simulation.

Compensating for blade tip clearance deterioration in active clearance control

Abstract: A method to compensate for blade tip clearance deterioration between rotating blade tips and a surrounding shroud in an aircraft gas turbine engine includes determining one or more variables based on at least one or more moving averages of one or more engine operating parameters respectively averaged over a fixed number of operational engine flight cycles and adjusting a flow rate of thermal control air to counter the blade tip clearance deterioration based on the one or more variables. The engine operating parameters may include running number of engine cycles, takeoff and cruise exhaust gas temperature margins, a cruise turbine efficiency, takeoff and cruise maximum turbine speeds, a cruise fuel flow. Some or all of the variables may be differences between the moving averages and corresponding baselines of the engine operating parameters respectively or the variables may all be moving averages. The flow rate may be adjusted incrementally.

Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES

Abstract: When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers.