Tip clearance

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

Influence of tip clearance and inlet flow distortion on ducted fan performance in VTOL UAVs

Abstract: Ducted fan vertical take-off and landing (VTOL) uni nhabited aerial vehicles (UAV) are popular because they offer higher disk loading compared to open rotors and improve propulsive performance. Although ducted fans provide high performance in many VTOL applications, there are still unresolv ed problems associated with them especially in the forward flight mode. The main problems in these applications are distort ion of inlet flow due to forward flight and tip lea kage related problems in hover and forward flight modes. The present experi mental study mainly uses total pressure measurement s downstream of a ducted fan rotor to investigate the performance dro p in hover and forward flight condition related wit h these problems. Tip leakage flow related total pressure losses are domi nant in hover condition. Losses are dramatically in creased in forward flight due to inlet lip separation and inlet flow distorti on. For a better comparison of the tip clearance ef fects in forward flight, a new parameter named as “Forward flight penalty” is defined. In addition to comprehensive aerodynamic l oss measurements downstream of the rotor, the paper also discusses t he results from the early stage of a computational study aiming to calculate the 3D turbulent viscous flow in and around the duc ted fan.

Capacitive blade tip clearance measurements for a micro gas turbine

Abstract: The efficiency of a gas turbine has an inverse relationship with the clearance between the rotor blades and the casing. Recent efforts in miniaturization of micro gas turbine engines have created new challenge in tip clearance measurement. This paper describes the development of a tip clearance measurement system, based on capacitive measurement for a palm-top micro gas turbine engine. The sensor uses a ratio-metric measurement principle with synchronous detector to measure the average tip clearance between the rotor blades and the casing. A surface modification of the nonconductive compressor is used to create an electrode opposing the casing. A measurement range of 100 /spl mu/m was achieved with a resolution of 0.8 /spl mu/m.

Analysing Non-Synchronous Blade Vibrations in a Transonic Compressor Rotor

Abstract: This paper aims to add to the understanding of non-synchronous blade vibration caused by unsteady flow close to the stability limit of transonic compressor rotors. Blade vibrations are measured in the rotating frame of reference by strain gauges applied to the blades and additionally in the stationary frame of reference by capacitive tip clearance/tip timing sensors. Furthermore unsteady pressure transducers in the casing wall are used to analyse the flow phenomena during high blade vibration amplitudes. During the transient experiments, the compressor is back-pressured into its stability limit. Two transient measurements of a compressor setup with an enlarged tip clearance of 2.5% blade chord are analysed at part speed and design speed. This means that subsonic and transonic operation conditions are analysed. In both cases, nonsynchronous vibration occurred and limited the compressor operation. The mechanism leading to these vibrations is based on an unsteady flow pattern that rotates relative to the rotor, reported as rotating instability.

Tip clearance harmonic estimation

Abstract: A method of tip clearance estimation for a rotor blade is provided. The method includes measuring blade deflection of the rotor blade, generating a harmonic function for the rotor blade from the measured blade deflection, predicting tip displacement of the rotor blade using the generated harmonic function and adjusting a position of the rotor blade according to the predicted tip displacement.

Axial fan tip clearance noise: Experiments, Lattice–Boltzmann simulation, and mitigation measures:

Abstract: The effect of tip clearance in an axial fan on its aerodynamic and aeroacoustic performance is investigated experimentally as well as via a Lattice–Boltzmann flow simulation method. An increase in ...