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Showing papers on "Tip clearance published in 1991"


Journal ArticleDOI
TL;DR: In this paper, a linear cascade with tip clearance is complemented by numerical solutions of the three-dimensional Navier-Stokes equations in an investigation of tip leakage flow, and detailed comparisons show that the mechanism of leakage is primarily inviscid.
Abstract: Experimental measurements in a linear cascade with tip clearance are complemented by numerical solutions of the three-dimensional Navier–Stokes equations in an investigation of tip leakage flow. Measurements reveal that the clearance flow, which separates near the entry of the tip gap, remains unattached for the majority of the blade chord when the tip clearance is similar to that typical of a machine. The numerical predictions of leakage flow rate agree very well with measurements, and detailed comparisons show that the mechanism of tip leakage is primarily inviscid. It is demonstrated by simple calculation that it is the static pressure field near the end of the blade that controls chordwise distribution of the flow across the tip. Although the presence of a vortex caused by the roll-up of the leakage flow may affect the local pressure field, the overall magnitude of the tip leakage flow remains strongly related to the aerodynamic loading of the blades.

239 citations


Journal Article
TL;DR: In this article, a new approach is presented for analyzing compressor tip clearance flow, where the clearance velocity field can be decomposed into independent throughflow and crossflow, since chordwise pressure gradients are much smaller than normal pressure gradient in the clearance region.
Abstract: A new approach is presented for analyzing compressor tip clearance flow. The basic idea is that the clearance velocity field can be (approximately) decomposed into independent throughflow and crossflow, since chordwise pressure gradients are much smaller than normal pressure gradients in the clearance region. As in the slender body approximation in external aerodynamics, this description implies that the three-dimensional steady clearance flow can be viewed as a two-dimensional, unsteady flow. Using this approach, a similarity scaling for the crossflow in the clearance region is developed and a generalized description of the clearance vortex is derived. Calculations based on the similarity scaling agree well with a wide range of experimental data in regard to flow features such as crossflow velocity field, static pressure field, and tip clearance vortex trajectory.

115 citations


Journal ArticleDOI
TL;DR: In this paper, a new approach is presented for analyzing compressor tip clearance flow, where the clearance velocity field can be decomposed into independent throughflow and crossflow, since chordwise pressure gradients are much smaller than normal pressure gradient in the clearance region.
Abstract: A new approach is presented for analyzing compressor tip clearance flow. The basic idea is that the clearance velocity field can be (approximately) decomposed into independent throughflow and crossflow, since chordwise pressure gradients are much smaller than normal pressure gradients in the clearance region. As in the slender body approximation in external aerodynamics, this description implies that the three-dimensional steady clearance flow can be viewed as a two-dimensional, unsteady flow. Using this approach, a similarity scaling for the crossflow in the clearance region is developed and a generalized description of the clearance vortex is derived. Calculations based on the similarity scaling agree well with a wide range of experimental data in regard to flow features such as crossflow velocity field, static pressure field, and tip clearance vortex trajectory.

111 citations


Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this paper, a numerical experiment has been carried out to define the nearstall casing endwall flowfield of a high-speed fan rotor using a simple clearance model, whose calibration is presented.
Abstract: A numerical experiment has been carried out to define the near-stall casing endwall flowfield of a high-speed fan rotor. The experiment used a simulation code incorporating a simple clearance model, whose calibration is presented. The results of the simulation show that the interaction of the tip leakage vortex and the in-pasage shock plays a major role in determining the fan flow range. More specifically, the computations imply that it is the area increase of this vortex as it passes through the in-passage shock, which is the source of the blockage associated with stall. In addition, for fans of this type, it is the clearance over the forward portion of the fan blade which controls the flow processes leading to stall.

43 citations


Patent
10 Dec 1991
TL;DR: In this article, a blade clearance control apparatus (46) for a gas turbine engine (10) comprises a series of segments (42) which define a casing in the rotor path of high pressure shroudless turbine blades.
Abstract: A blade clearance control apparatus (46) for a gas turbine engine (10) comprises a series of segments (42) which define a casing in the rotor path of high pressure shroudless turbine blades (30). The segments (42) are attached to plates (78) having surfaces co-operating with chordal lengths (74) of a number of pressure tubes (68) which are located in a frame (46). The application and release of pressure to the pressure tubes (68) causes the segments (42) to move between inner and outer positions in order to control clearance X between the tips of blades (30) and the segments (42).

35 citations


Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this paper, the effect of difference in rotor tip clearance on the mean flow fields and unsteadiness and mixing across a stator blade row were investigated using hot-wire anemometry, pressure probes, flow visualization and the ethylene tracer-gas technique on a single stage axial flow compressor.
Abstract: The effect of difference in rotor tip clearance on the mean flow fields and unsteadiness and mixing across a stator blade row were investigated using hot-wire anemometry, pressure probes, flow visualization and the ethylene tracer-gas technique on a single stage axial flow compressor. The structure of the three-dimensional flow fields was discussed based on results of experiments using the 12-orientation single slanted hot-wire technique and spectrum analysis of velocity fluctuation. High-pass filtered measurements of turbulence were also carried out in order to confirm small-scale velocity fluctuation which is more realistically referred to as turbulence. The spanwise distribution of ethylene gas spreading, estimated by the measured small-scale velocity fluctuation at the rotor exit, agreed quite well with that which was experimentally measured. This fact suggests the significant role of turbulence, generated within the rotor, in the mixing process across the downstream stator. The value of the maximum mixing coefficient in the tip region was found to increase linearly as the tip clearance became enlarged, starting from the value at midspan.Copyright © 1991 by ASME

26 citations


Patent
Jeffrey Glover1
16 Apr 1991
TL;DR: In a gas turbine engine, a conduit delivers pressurized cooling air to a selected group of hollow struts at a temperature sufficient to induce thermal contraction of the struts, thereby opposing a downward shift in the rotor axis during high power engine operation, and maintaining a circumferentially uniform tip clearance as mentioned in this paper.
Abstract: In a gas turbine engine, conduit delivers pressurized cooling air to a selected group of hollow struts at a temperature sufficient to induce thermal contraction of the selected group of hollow struts, thereby opposing a downward shift in the rotor axis during high power engine operation, and maintaining a circumferentially uniform tip clearance. Air baffles disposed in the cooled struts ensure radially uniform thermal contraction and efficient heat transfer.

25 citations


Dissertation
04 Jun 1991

21 citations


Patent
01 Jul 1991
TL;DR: An axial flow compressor in which rotor blade clearance is controlled by the cross-sectional area of a ring surrounding the stator case and by a gap between the inner surface of the ring and the outer surface established at the time of compressor build is described in this paper.
Abstract: An axial-flow compressor in which rotor blade clearance, in an area where the stator case surrounding a rotor blade stage is unsupported, is controlled by the cross-sectional area of a ring surrounding the stator case and by a gap between the inner surface of the ring and the outer surface of the stator case established at the time of compressor build.

20 citations


Dissertation
01 Jan 1991
TL;DR: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991 as mentioned in this paper, Massachusetts State University, Boston.
Abstract: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991.

20 citations


Patent
28 Nov 1991
TL;DR: In this paper, a tip clearance control system having a plurality of impingement manifolds to unevenly heat or cool a turbine shroud is described, such creating a non-uniform circumferential temperature distribution to produce ovalization of said turbine shroud.
Abstract: Tip clearance control system having a plurality of impingement manifolds (40) to unevenly heat or cool a turbine shroud (28) such creating a non-uniform circumferential temperature distribution to produce ovalization of said turbine shroud (28) to conform to high load induced non-concentricities of the turbine rotor (52).

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this article, the formation of the tip clearance vortex and the passage vortices is presented, which are strongly influenced by the spanwise non-uniform stator outlet flow.
Abstract: Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data in- cludes the static pressure distribution on the rotor blade passage surfaces and radial-cir- cumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The formation of the tip clearance vortex and the passage vortices is presented, which are strongly influenced by the spanwise non- uniform stator outlet flow. Taking the experi- mental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed. Nomenclature b, � axial chord Cvelocity, absolute frame hspan nshaft speed pstatic pressure p, total pressure schord tpitch ucircumferential speed u' random axial velocity fluctuation v' random radial velocity fluctuation wvelocity, relative frame w' random circumferential velocity fluctuation Zblade number aflow angle in circumferential direction, absolute frame 6� flow angle in circumferential direction, relative frame d, tip clearance tv, reduced frequency Subscripts

Journal ArticleDOI
TL;DR: In this article, the C106 four-stage compressor was investigated in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor.
Abstract: This paper follows directly from Part I which contains not only the description of the facilities and the results for the C106 four-stage compressor but also the background, list of nomenclature, acknowledgement and references. The discussion and conclusions for Part I and Part II are given here. The single stage compressor results show the significant effects of inlet guide vane (IGV) wakes on mixing across the stage in the so called ‘free stream’ region; in the casing region tip clearance flow is shown to play an important role in mixing. Explanations for these results are given. Investigations were also carried out in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor. Turbulent diffusion has been found to be the dominant mechanism in spanwise mixing; anisotropic inhomogeneous turbulent diffusion is mainly responsible for the non-uniform mixing in the corner region. The larger spread of tracer gas in the tangential direction than in the radial direction is mainly caused by the wake dispersion and relative flow motions within the blade wakes as well as secondary flow contributions in the end-wall regions.Copyright © 1990 by ASME

Journal Article
TL;DR: In this article, a linear cascade with tip clearance is complemented by numerical solutions of the three-dimensional Navier-Stokes equations in an investigation of tip leakage flow, and it is demonstrated by simple calculation that it is the static pressure field near the end of the blade which controls chordwise distribution of the flow across the tip.
Abstract: Experimental measurements in a linear cascade with tip clearance are complemented by numerical solutions of the three-dimensional Navier-Stokes equations in an investigation of tip leakage flow. Measurements reveal that the clearance flow, which separates near the entry of the tip gap, remains unattached for the majority of the blade chord when the tip clearance is similar to that typical of a machine. The numerical predictions of leakage flow rate agree very well with measurements and detailed comparisons show that the mechanism of tip leakage is primarily inviscid. It is demonstrated by simple calculation that it is the static pressure field near the end of the blade which controls chordwise distribution of the flow across the tip. Although the presence of a vortex caused by the roll-up of the leakage flow may affect the local pressure field, the overall magnitude of the tip leakage flow remains strongly related to the aerodynamic loading of the blades.Copyright © 1990 by ASME

Journal ArticleDOI
TL;DR: In this article, the authors examined the pressure loss due to the tip clearance based on a macroscopic balance of forces and derived the two kinds of loss are derived, the former coming from the induced drag which is parallel to the blade while the latter comes from the missing blade force normal to a blade in the clearance zone.
Abstract: For predicting the tip clearance loss of turbomachines, different equations are published in the literatures based on differnt principles. In 1986 the present author posturated a new theory where the pressure loss consisted of two parts, one was the pressure loss induced by the drag force of the leaked flow and the other was the pressure loss to support the axial pressure difference without blades in the tip clearance zone. There were comments such as the two losses were the same loss looked from two different view points, or at least a part of the former was included in the latter or vice versa.In this paper the pressure loss due to the tip clearance is examined based on a macroscopic balance of forces and the two kinds of loss are derived. Furthermore, it is made clear that the former comes from the induced drag which is parallel to the blade while the latter comes from the missing blade force normal to the blade in the clearance zone. Because these two forces are mutually perpendicular, the two losses are entirely different in nature and they do not even partially overlap to each other. It is also made clear quantitatively, how the loss of the kinetic energy of leaked flow is related to the induced drag of the clearance flow.Copyright © 1990 by ASME

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this paper, three-dimensional solutions of the ensemble-averaged Navier-Stokes equations have been computed for a high-turning turbine rotor passage, both with and without tip clearance effects.
Abstract: Three-dimensional solutions of the ensemble-averaged Navier-Stokes equations have been computed for a high-turning turbine rotor passage, both with and without tip clearance effects. The geometry is Pratt & Whitney’s preliminary design for the Generic Gas Generator Turbine (GGGT), having an axial chord of 0.5 inch and turning angle of about 160 degrees. The solutions match the design Reynolds number of 3x 106/inch and design inflow/outflow distributions of flow quantities. The grid contains 627,000 points, including 20 radial points in the clearance gap of 0.015 inch, and has a minimum spacing of 10−4 inch adjacent to all surfaces. The solutions account for relative motion of the blade and shroud surfaces and include a backstep on the shroud. Computed results are presented which show the general flow behavior, especially near the tip clearance and backstep regions. The results are generally consistent with experimental observations for other geometries having thinner blades and smaller turning angles. The leakage flow includes some fluid originally in the freestream at 91 percent span. Downstream, the leakage flow behaves as a wall jet directed at 100 degrees to the main stream, with total pressure and temperature higher than the freestream. Radial distributions of circumferentially-averaged flow quantities are compared for solutions with and without tip leakage flow. Two-dimensional solutions are also presented for the mid-span blade geometry for design and off-design inflow angles.Copyright © 1991 by ASME

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this article, a mixed-flow pump impeller at various tip clearances for both shrouded and unshrouded cases was investigated and the interaction between the tip leakage flows and secondary flows and the formation of the wake regions was explained based on experimental observation and computations by the Dawes 3D Navier-Stokes code.
Abstract: The flow phenomena around the positive slope region of the head-flow characteristic were investigated experimentally on a mixed-flow pump impeller at various tip clearances for both shrouded and unshrouded cases. A positively-sloped head-flow characteristic (abrupt decrease in pressure head) was caused by the onset of extensive flow separation in the impeller at the casing-suction surface corner. The corner separation in unshrouded cases appeared at much lower flow rate than the shrouded case due to the favorable effect of the tip leakage flow which displaced the wake region away from the corner. The interaction between the tip leakage flows and secondary flows and the formation of the wake regions in shrouded and unshrouded cases were explained based on experimental observation and computations by the Dawes’ 3-D Navier-Stokes code. In the shrouded case, the flow rate, at which an abrupt decrease in pressure head appeared, was lowered substantially by introducing a leakage flow through a slit made between the shroud and the blade tip. Inlet recirculation was triggered by the corner separation and developed more gradually for larger tip clearances. Both the increased loss, due to the extensive flow separation, and the decreased Euler’s head, due to the abrupt change in flow pattern caused by the inlet recirculation, were responsible for the generation of positively-sloped head-flow characteristic in the unshrouded case when the tip clearance was small, while the increased loss was the primary factor in the shrouded case.Copyright © 1991 by ASME

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this paper, an extension of the secondary flow calculation method is presented in order to estimate the influence of the tip clearance on the SFA, and the estimated tip clearance losses, based on the flow field structure, are compared to results obtained from various semi-empirical loss correlations found in the literature.
Abstract: In this paper an extension of our secondary flow calculation method is presented in order to estimate the influence of the tip clearance on the secondary flow field.The impact of the tip clearance vortex is embodied in the method so that the secondary vorticity field, based on the complete form of the meridional vorticity transport equation is properly modified. In this way the changes of the secondary flow field quantities are predicted along with the resulting additional losses imposed by the existence of the tip clearance.The estimated tip clearance losses, based on the flow field structure, are compared to results obtained from various semi-empirical loss correlations found in the literature.Several cases encountered in axial flow compressor configurations are investigated and the calculated results are favourably compared to experimental data and results of previous calculations.Additionally, in order to clarify the influence of the tip clearance structure upon the secondary flow field, cases with and without tip clearance are also examined.Copyright © 1991 by ASME


Journal ArticleDOI
TL;DR: In this paper, the effects of the impeller blade tip clearance and the blade number on the inlet reverse flow starting point were clarified. And the effect of blade number was also studied.
Abstract: In the previous report, it was pointed out that leakage flow through the comparatively large blade tip clearance of an open impeller considerably affects the flow just before the capacity at which an inlet reverse flow occurs. Then, in this paper, unsteady flows at the impeller entrance were measured for a small blade tip clearance impeller and a closed impeller. For the former, especially, static pressure distribution measurements on the casing surface outside of impeller blades and the flow visualization in the impeller were performed. The effect of blade number was also studied. As a result, the effects of the impeller blade tip clearance and the blade number on the inlet reverse flow starting point were clarified.

Journal ArticleDOI
TL;DR: In this paper, the internal gap flow is dominated by a ''separation bubble'' within which intense static pressure driven shear flows takes place giving rise to 38% of the overall loss.
Abstract: The flows occurring in the tip clearance region of an axial turbine is studied in a linear cascade with flow visualisation, surface pressures and with flow probes. The internal gap flow is dominated by a \"separation\" bubble within which intense static pressure driven shear flows takes place giving rise to 38% of the overall loss. This microflow pattern was shown to be uninfluenced by blade relative motion but could be eliminated by contouring and radiusing the blade tip to also improve rotor performance determined by a method of converting stationary cascade data into a simulated rotor. The development of loss on the endwall is almost unaffected by clearance up to mid chord. Thereafter loss growth is very rapid which could be due to the influence of suction corner diffusion on the high loss tip clearance vortex.

Journal ArticleDOI
TL;DR: In this article, the three-dimensional flow field through a linear cascade with tip clearance was numerically studied by solving Navier-Stokes equations and the detailed flow phenomena around the blade tip, such as the formation of separation bubbles on the tip surface, were clearly described.
Abstract: The three-dimensional flow field through a linear cascade with tip clearance was numerically studied by solving Navier-Stokes equations. A fundamental cascade model composed of flat plates, on which corresponding experimental data were available, was adopted to develop the appropriate solution method for the flow through the tip clearance. The computed normal force distributions on blades and velocity vectors in the downstream flow field showed good qualitative agreement with the experimental data. The detailed flow phenomena around the blade tip, such as the formation of separation bubbles on the tip surface, were clearly described. The spanwise distributions of the normal force on the blade were investigated for various tip clearances, and it was found that the normal force on the extremity of the blade did not diminish in the case of small clearances of less than 0.6% of the blade span because of the blockage of leakage flow due to the effect of viscosity.

Patent
28 Nov 1991
TL;DR: In this paper, the authors propose a movable section capable of relative moving in the direction that the wind blows between a ring-like cylinder section and the fan to vary a tip clearance.
Abstract: PURPOSE:To vary a tip clearance all over the periphery of a fan by changing both diameters of the fan, and also providing a movable section capable of relative moving in the direction that the wind blows thereto between a ring-like cylinder section and the fan. CONSTITUTION:The upper stream side diameter and the down stream side diameter of the cooling fan 14 provided on a radiator shroud 12 are different from each other. A ring-like cylinder section 16 comprises a fixed side ring 16a and movable side ring 16b, and both rings are relatively movable by the actuation of an actuator 24 through a movable section 18 in the direction that the wind blows thereto. Therefore, when the movable side ring 16b is moved, the covering quantity of the ring-like cylinder section 16 and the fan 14 varies, as a result, the tip clearance provided between the outer periphery of the fan 14 and the head of the ring-like cylinder section 16 can be varied all over the periphery.

Proceedings ArticleDOI
B. Glezer1
03 Jun 1991
TL;DR: In this paper, a non-traditional design concept addressing turbine blade tip clearance reduction to provide long-term engine performance improvement and stability is presented, based on the direct attachment of the diaphragm, which supports Stage 1 integral nozzle and tips shroud segments, to the bearing housing, thus providing a close thermal link between the rotor and the stator.
Abstract: A recently developed non-traditional design concept addressing turbine blade tip clearance reduction to provide long-term engine performance improvement and stability is presented. The concept is based on the direct attachment of the diaphragm, which supports Stage 1 integral nozzle and tips shroud segments, to the bearing housing, thus providing a close thermal link between the rotor and the stator. Transient thermal matching between the rotating and stationary structures was based on analytical prediction. Results of the complex turbine hot section study including cooling flow, thermal, stress, and deflection analyses are presented. An advanced tip clearance measurement technique was used in the full scale engine test to verify the analytical predictions. The potential to reduce tip clearance to less than 1% of blade height without blade tip rubs has been demonstrated. Extensive field operating experience with more than 100 Centaur Type ‘H’ engines showed very light or no blade tip rub and corresponding engine performance stability during long-term operation.Copyright © 1991 by ASME

Dissertation
01 Dec 1991
TL;DR: In this article, an analytical and experimental study of the performance changes and flow effects of rotor tip clearance variation in axial flow compressors is presented, demonstrating that previously unrecognized loss characteristics and flow behavior trends can be identified in a wide range of published tests of clearance effects.
Abstract: An analytical and experimental study of the performance changes and flow effects of rotor tip clearance variation in axial flow compressors is presented. The analyses demonstrate that previously unrecognized loss characteristics and flow behavior trends can be identified in a wide range of published tests of clearance effects. The performance and flow data are correlated at constant power conditions or nondimensionally in terms of the test compressor's geometry and wall flow conditions to observe the trends. Flow field changes caused by increasing the tip seal clearance of a low speed, large scale axial compressor having a symmetric velocity diagram were examined experimentally. The measurements were made at several clearances for one rotational speed. Synchronized blade-to-blade measurements of case wall static pressure and skin friction under the rotor tip of the second stage were collected. The detailed surveys showed the tip local blade-to-blade flow pattern to be dependent on the rotor blade's position relative to the upstream stator. Preliminary case wall skin friction traces showed a similar dependence and indicated a region of stagnant flow several blade thicknesses wide exists on the case wall beside the blade suction side. The stagnant region's position corresponds with a minimum wall static pressure trough standing off the blade suction surface. The blade loading at the tip was found to alter its form depending on the passage throughflow, stator relative position and tip clearance height Detailed measurements and correlative results are presented. The detailed measurements were evaluated in the context of the flow mechanisms causing the efficiency losses, the models typically used to quantify tip clearance effects, computations of the tip local flow field and the possibilities for improved tip local blade and case wall geometry design for axial flow compressors.

Dissertation
01 Jan 1991
TL;DR: Martinez-Sanchez et al. as mentioned in this paper investigated the effects of blade-tip leakage in a turbine by modeling the stage as an incomplete actuator disk, taking advantage of the xz solutions for the spanwise flow redistribution due to constant geometrical gap width, they are generalized to include flow with some azimuthal inlet velocity component which develops in the xy redistribution on the R scale when the turbine is eccentric.
Abstract: The effects of blade-tip leakage in a turbine are investigated by modeling the stage as an incomplete actuator disk. Taking advantage of the xz solutions for the spanwise flow redistribution due to constant geometrical gap width, they are generalized to include flow with some azimuthal inlet velocity component which develops in the xy redistribution on the R scale when the turbine is eccentric. The relevant flow quantities are linearized into their corresponding mean and perturbation parts. 5 downstream and 1 upstream perturbation modes are identified. Combining with the linear sensitivities calculated from the xz model, the coefficients for the perturbation modes superposition are calculated. The resulting perturbed flow quantities represent various responses of the downstream flowfield to a cyclically varying gap at the disk. Finally, the Alford force coefficients are calculated and correlate well with experimental data. Only the Alford force coefficient in the Y direction and the loss coefficient 1 are sensitive to changes in the mean geometrical gap. Thesis Supervisor: Prof. Manuel Martinez-Sanchez Title: Associate Professor, Gas Turbine Laboratory Acknowledgments I wish to express my gratitude to Prof. M. Martinez-Sanchez for his guidance and instruction throughout the project, not to mention especially his patience in going through all the details of this work with me. I am grateful to Dr. T. W. Poon and S. Yoo for their concern over my research work and the progress in writing up this thesis. Much thanks are given to C. Adrian and A. Wong for preparing the figures with me. Finally, I would like to dedicate this thesis to my parents and my younger brother for their love, care and prayerful support of me during this program.

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this article, the effect of tip clearance changes on the pressure at the case wall of a second stage rotor is described, and the results suggest a viscous or shearing layer, due to blade-to-wall relative motion, is generated on the blade side of the tip gap which modifies the inviscid relative flow field and produces an unloading on the rotor tip.
Abstract: This paper describes the effect of tip clearance changes on the pressure at the case wall of a second stage rotor. Wall shear distributions under the rotor tip are also presented. The results show low pressure areas extending along the rotor suction side but lying away from the blade. Pressure contours indicate the tangential loading at the tip is lower than predicted by two dimensional calculations, however, the predicted loading is observed between the lowest pressure’s path in the passage and the blade pressure side. The results suggest a viscous or shearing layer, due to blade-to-wall relative motion, is generated on the blade side of the tip gap which modifies the inviscid relative flow field and produces an unloading on the blade tip.Copyright © 1991 by ASME