Topic
Tip clearance
About: Tip clearance is a research topic. Over the lifetime, 2637 publications have been published within this topic receiving 32671 citations.
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TL;DR: In this article, an extensive hydro-generator rotordynamic model is presented along with a technique for determining imbalances and shaft misalignments using the model and mechanical run vibration measurements.
Abstract: An extensive hydro-generator rotordynamic model is presented along with a technique for determining imbalances and shaft misalignments using the model and mechanical run vibration measurements. The hydro-generator model combines a finite element rotor model with a finite difference guide bearing model, generator magnetic forces and turbine hydraulic forces to calculate natural frequencies, stability and steadystate response. The complete model allows a great number of inputs including imbalances, rotation speed, guide bearing misalignments, coupling misalignments, bearing clearances, bearing temperatures, generator stator and rotor center misalignments, generator average air gap, generator power output and turbine blade tip clearance, all of which are described in this paper. Finally, the numerical results are compared with vibration data from the mechanical run and load test of an actual hydro generator unit.
14 citations
Patent•
01 Feb 2012TL;DR: In this article, a valve is controlled to act on a flow rate and/or a temperature of air directed against the turbine ring of a casing surrounding the blades of a turbine rotor.
Abstract: A method and system for controlling clearance between the tips of blades of a turbine rotor in a gas turbine airplane engine and a turbine ring of a casing surrounding the blades. A valve is controlled to act on a flow rate and/or a temperature of air directed against the casing. The valve is of the on/off type for switching between an open state and a closed state in a determined reaction time, the valve control module including a corrector for determining a first binary control signal that can take a first value corresponding to an open state and a second value corresponding to a closed state of the valve. The corrector includes a time-delay module for determining a binary control signal, with the duration between two successive changes of state in the control signal being not less than the reaction time of the valve.
13 citations
TL;DR: In this article, the effect of three types of casing contouring, step, trench, and arc casings, on aerodynamic performance of an unshrouded turbine rotor at design and off-design incidences was investigated.
Abstract: Tip leakage flow is responsible for a number of aerodynamic losses in turbines, and the mixing of tip leakage flow with the passage secondaryflowcauses significant losses. This paperpresents a numerical investigation of the effect of three types of casing contouring: 1) step, 2) trench, and 3) arc casings on aerodynamic performance of anunshrouded turbine rotor at design and off-design incidences, in an attempt to seek an optimal casing contour with the objective both of avoiding direct tip leakage in the tip clearance, and of efficiently using the interaction between the tip leakage vortex and passage vortex inside rotor passage, and then to reduce the total losses in turbines. The results show that the reduction in tip leakage losses obtained by the optimized casing contour significantly overrides the losses caused by the step in theflowpath. Introduction of casing step thickens the inlet boundary layer, which increases the strength of the tip passage vortex and hence suppresses the evolution of the tip leakage vortex. Step and trench casings provide the largest efficiency increase when the inlet flow direction is normal to the casing step while arc casing achieves the best performance improvement at the design incidence.
13 citations
01 May 2016
TL;DR: In this article, the authors investigated the relationship between rotating instability and fluctuating tip clearance flow and found that tip clearance vortex structures oscillate periodically at low flow rate conditions, which leads to an intense fluctuation of the casing flow field.
Abstract: To investigate the relationship between rotating instability and fluctuating tip clearance flow, experimental tests as well as numerical studies are conducted on a 1.5 stage low-speed axial compressor rig. The rotating instability is detected through casing mounted dynamic pressure sensors. The phase-locked and root-mean-square pressure contours show that the interaction of tip clearance flow with the neighboring blade is the most likely cause of casing flow field fluctuation. From the calculated results of entire-annulus cascade, it is found that the tip clearance vortex structures oscillate periodically at low flow rate conditions. That leads to intense fluctuation of the casing flow field. Further, phase lag of pressure fluctuations exists between two neighboring passages, which induces a rotating pressure pattern of multiple frequencies. The frequency characteristics of this rotating pressure pattern caused by fluctuating tip clearance flow is coincident with the frequency of rotating instability. Thi...
13 citations
TL;DR: In this article, the authors show that the stall margin and pressure ratio of an axial compressor can both be increased with the use of circumferential groove casing treatments over the rotor, which can be found in many axial compressors.
Abstract: The stall margin and pressure ratio of an axial compressor can both be increased with the use of circumferential groove casing treatments over the rotor. Performance and stall point measurements we...
13 citations