Tip clearance

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

An experimental study on the reduction of motor-fan noise by modification of the blade and shroud configuration:

Abstract: The noise reduction (NR) of fans used for cooling electric motors is one of the key parameters in the design of a motor fan. In the authors’ previous paper, aeroacoustic analysis (which is based on unsteady computational fluid dynamics results) was performed for the baseline fan to know its sound level. To further find a better blade shape from an NR point of view, aeroacoustic analysis on various blade profiles from the NACA-63 and NACA-65 series was conducted. In this work, an experimental study on the baseline fan and three redesigned composite material fans for the low-noise fan is performed. The experimental parameters under investigation are better aerofoil-shape blade cross-section, using inlet bell-mouth entry, using composite materials, reducing the number of blades, using uneven blade spacing, making it a mixed flow fan, using backward-skewed blade design and reducing tip clearance. From the noise measurements in a semi-anechoic chamber for Fan-2, it is observed that the overall NR was 1...

Effects of thermal boundary condition, fin size, spacing, tip clearance, and material on pressure drop, heat transfer, and entropy generation optimization for forced convection from a variable-height shrouded fin array

Abstract: Fully developed forced convection through a variable-height shrouded fin array is studied numerically. Two different base thermal boundary conditions are considered being isothermal and isoflux heating. In either case, the shroud is assumed to be adiabatic. Following the application of two separate thermal energy equations, the conjugate heat transfer problem is solved. Different fin material, spacing, height, tip clearance, and size are examined. Considering these effects, pressure drop, heat transfer, and entropy generation aspect of the problem are studied in detail.

Investigation of the tip clearance flow inside and at the exit of a compressor rotor passage-part II: turbulence properties

Abstract: The flow in the tip clearance region of a compressor rotor is highly turbulent due to the strong interaction of the leakage flow with the annulus wall boundary layer. This paper deals with the turbulence properties of the flow in the tip clearance region of a moderately loaded compressor rotor. The experimental results reported in this paper were obtained using a two-sensor hot-wire probe in combination with an ensemble averaging technique. Blade-to-blade distribution of the axial and tangential turbulence intensities at various radial locations and ten axial locations (four inside the blade passage and the remaining six outside the passage) were derived from this data. Isointensity contours in the clearance region at various radial locations were also obtained from the experimental data. A region of very high turbulence intensities was indicated at the half-chord location from these results. The turbulence intensity profiles also indicated that the leakage flow travels toward the midpassage before rolling up. The turbulence is almost isotropic beyond three-quarter chord downstream of the trailing edge.

Heat Transfer on a Film-Cooled Rotating Blade Using a Two-Equation Turbulence Model

Abstract: A three-dimensional Navier-Stokes code has been used to compare the heat transfer coefficient on a film-cooled, rotating turbine blade. The blade chosen is the ACE rotor with five rows containing 93 film cooling holes covering the entire span. This is the only film-cooled rotating blade over which experimental data is available for comparison. Over 2.278 million grid points are used to compute the flow over the blade including the tip clearance region, using Coakley's q-omega turbulence model. Results are also compared with those obtained by Garg and Abhari (1997) using the zero-equation Baldwin-Lomax (B-L) model. A reasonably good comparison with the experimental data is obtained on the suction surface for both the turbulence models. At the leading edge, the B-L model yields a better comparison than the q-omega model. On the pressure surface, however, the comparison between the experimental data and the prediction from either turbulence model is poor. A potential reason for the discrepancy on the pressure surface could be the presence of unsteady effects due to stator-rotor interaction in the experiments which are not modeled in the present computations. Prediction using the two-equation model is in general poorer than that using the zero-equation model, while the former requires at least 40% more computational resources.

Non-Uniform Flows in Axial Compressors Due to Tip Clearance Variation

Abstract: An approximate analysis is presented for the asymmetric velocity non-uniformities that can exist in an axial compressor due to variations in tip clearance around the circumference. Calculations have been carried out for several different compressor configurations, as well as for both rotating (fixed to rotor) and stationary clearance variations. The numerical results show that, for a given compressor, the ratio of (per cent) variation in axial velocity to (per cent) variation in pressure rise coefficient due to asymmetric clearance increases as flow decreases, although this trend in not necessarily true for the magnitude of actual velocity non-uniformity. In addition, the velocity non-uniformity due to a rotating clearance can be substantially larger than that due to a stationary clearance.