Tip clearance

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

Numerical Study on Tip Clearance Effect on Performance of a Centrifugal Compressor

Abstract: Effects of tip clearance on through flows and performance of a centrifugal compressor impeller with six different tip clearances were numerically studied using CFX-TASCflow. The flow structures inside the impeller of a centrifugal compressor were visualized observing streamlines starting the leading edge of blade tips. The calculated results at the impeller exit were circumferential averaged for quantitative discussion. Flow, pressure and entropy contours at the impeller exit were largely influenced by the tip leakage flow. Tip clearance effect on the performance was decomposed into inviscid and viscous components using one-dimensional relations expressed in terms of the specific work reduction and the additional entropy generation. Both inviscid and viscous effects affected performance to similar extent, while efficiency drop was mainly influenced by viscous loss of the tip leakage flow. Performance reduction and efficiency drop due to tip clearance was proportional to the ratio of tip clearance to blade height. A simple model suggested in the present study predicts performance and efficiency drop quite successfully.Copyright © 2002 by ASME

The Effect of Compressor Rotor Tip Crops on Turboshaft Engine Performance

Abstract: The results from an experimental study into the effect of compressor rotor tip clearance changes on the steady-state performance and stability margins of a free-power turbine turboshaft engine are presented and discussed. This work was directed at the development of methods to diagnose engine condition from gas path measurements. It was found that the normal production suite of engine instrumentation was able to measure the deterioration in engine performance due to the implanted compressor degradation and the resultant deviations in the measured parameters from their respective nominal baselines do provide useful indicators of engine condition.Copyright © 1992 by ASME

Microwave Turbine Tip Clearance Measuring System for Gas Turbine Engines

Abstract: For the last fifteen years various research groups have been trying to develop microwave systems that could be used for gas turbine engine condition monitoring and diagnostics. Such systems possess substantial advantages in comparison to other known systems and make possible to define rotor blades vibration parameters, discover blades rupture or their deformation, passing of foreign objects through air-gas channel, combustion chamber burnout as well as to define rotor rotation frequency and angular position. The article gives several examples of microwave systems use (detection of foreign objects in air-gas channel, dents in rotor blades) and results of experiments carried out by us. At present time we work on industrial microwave systems that will be used for measuring of tip clearance on ground and aircraft turbines. The article offers an analysis of microwave systems operation when performing measurements on shrouded and shroudless blades. It describes design concept of microwave system allowing measuring of tip clearance within the accuracy of 0.05 mm for each turbine blade for the whole rotation frequency range and under impact of high temperature and vibration. The results of measuring tip clearance on laboratory bench and gas generator of civil gas turbine engine are offered for consideration. The results of such tests make possible to consider the possibility of implementing proposed design of microwave turbine tip clearance measuring system in commercial equipment for test rigs that are used for gas turbine engine tests and fine tuning. The implementation of proposed design in aircraft version of the equipment is also considered.Copyright © 2008 by ASME

Centrifugal compressor tip clearance and impeller flow

Abstract: Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease.