Showing papers on "Tip clearance published in 1985"

Blade tip clearance control

Abstract: The invention is particularly concerned with the control of blade tip clearance in high pressure compressors of gas turbine engines. The compressor comprises a rotor assembly having radially extending rotor blades and a stator assembly. The stator assembly comprises an inner casing and a cylindrical wall member spaced radially from the inner casing to form a chamber. The axial ends of the cylindrical wall member seal with and are moveable radially with respect to the inner casing. The casing has radially inner and radially outer stops to limit radial movement of the cylindrical wall member. The cylindrical wall member carries a ring of shroud segments which are spaced radially from the rotor blades by a clearance. A valve supplies relatively high pressure air from the downstream end of the compressor into the chamber to contract the cylindrical wall member onto the inner stops to give optimum clearance during cruise, or connects the chamber to relatively low pressure air in the fan duct by aperture in outer casing by pipes to allow the cylindrical wall member to expand to the outer stops to prevent rubbing during transients.

End-wall and profile losses in a low-speed axial flow compressor rotor.

Abstract: The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor, is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

The design, performance and analysis of a high work capacity transonic turbine

Abstract: This paper describes the design and testing of a high work capacity single-stage transonic turbine of aerodynamic duty tailored to the requirements of driving the high-pressure core of a low cost turbofan engine. Aerodynamic loading was high for this duty (..delta..H/U/sup 2/ = 2.1) and a major objective in the design was the control of the resulting transonic flow to achieve good turbine performance. Practical and coolable blading was a design requirement. At the design point (pressure ratio = 4.48), a turbine total to total efficiency of 87.0 percent was measured - this being based on measured shaft power and a tip clearance of 1.4 percent of blade height. In addition, the turbine was comprehensively instrumented to allow measurement of aerofoil surface static pressures on both stator and rotor - the latter being expedited via a rotating scanivalve system. Downstream area traverses were also conducted. Analysis of these measurements indicates that the turbine operates at overall reaction levels lower than design but the rotor blade performs efficiently.

Three-dimensional viscous flow analysis for centrifugal impellers

Abstract: A SPACE-MARCHING Navier-Stokes solver is used to -TjLsimulate three-dimensional viscous flows in centrifugal impellers. This solver employs a finite volume integration procedure for the partially parabolic equations written in arbitrary curvilinear coordinates. The solution is achieved using a multiple-pass forward-marching iteration scheme. The accuracy of the analysis method is verified using impeller intrapassage laser-velocimeter data. The method is demonstrated to predict the jet/wake flows characteristic of centrifugal impellers. The result clearly shows the importance of modeling the blade tip clearance flow accurately.

Experimental investigation of losses and secondary flow in an axial compressor stage

Abstract: A detailed investigation of a three-dimensional flow using both stationary and rotating pressure probes has been carried out in a low speed axial compressor stage. At the casing of a rotor row there is secondary flow produced by the relative motion of the annular wall to rotor blade tip and the tip clearance flow. At the hub a channel vortex can be observed. The value of the loss coefficient of both rotor and stator rows determined from conventional pressure probe data is affected by flow unsteadiness. This effect has been considered in detail. As a result, the probes should be dynamically calibrated. The rotor and stator blade elements loss at mid-span approximately equals two-dimensional cascade loss, when the data of probes exposed to strong flow unsteadiness have been corrected.

Numerical solution of two- and three-dimensional rotor tip leakage models

Abstract: Blade tip losses represent a major efficiency penalty in a turbine or compressor rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This paper initially focuses on the control of tip leakage flow through minimization of the discharge coefficient to control the normal leakage flow component. A detailed numerical study of rotor-tip winglets, using a two-dimensional (2-D) turbulent flow formulation in primitive variables, is reported. Long and short winglets on the pressure, suction, and both sides (partial shroud) of the blade tip are analyzed. The results of the viscous analysis indicate superior performance with a partial shroud. The numerical technique is extended further to incorporate the axial flow effects by solving the full three-dimensional (3-D) Navier-Stokes equations with tip clearance effects included in the analysis. The 3-D model is validated by comparing it with the experimental results of the double-sided discharge rig of an earlier investigation. In addition, the variations in the specification of the boundary conditions at the inlet and exit of the pressure and suction side channels are investigated in detail. Comparison of the numerical and experimental results suggests an improvement in the predictive capability of the 3-D model over the 2-D analysis. Nomenclature b = height of the channel CD = discharge coefficient Ckn = discharge coefficient for 2-D model (Ref. 9) D — dilation term du dv dw dx dy Lc = axial length of tip clearance slot (3-D model) Ld = axial length of blade downstream of tip clearance (3-D model) Lg =tip clearance, gap height (3-D model) Lp = width of pressure side channel (3-D model) Ls - width of suction side channel (3-D model)

Investigation of a Tip Clearance Cascade in a Water Analogy Rig

Abstract: The tip clearance flow region of high pressure axial turbine blades for small gas turbine engines has been investigated in a water flow cascade. The blade model features variable clearance and variable endwall speeds. The cascade is scaled for Reynolds number and sized to give velocities suitable for visualization. Pressure profiles were measured on one blade, and correlated with the visualization. Unloading is found to be a major feature of the pressure field at both tip and midspan, and is intimately connected with scraping effects and the behavior of the clearance vortex. Some initial hot film velocity measurements are also presented.Copyright © 1985 by ASME

Construction for maintaining turbine tip clearance minimal

Abstract: PURPOSE:To normally maintain a blade tip clearance minimal by providing a tubular adjustment member of ceramics having an inner surface complementary in contour with the distal end of the blade tip of a turbine rotor, and being fitted in a shroud groove and supplying compressed air against the reverse side of the adjustment member. CONSTITUTION:A tubular adjustment member 13 of ceramics, having an inner surface complementary in contour with the distal end of the blade tip 1A of a rotor 1, is slidably received in and along the groove 15 of a turbine shroud 2. The reverseside of the adjustment member 13 defines a space 16. Compressed air is supplied into the space 16 via an air-supply channel 17. Thus the adjustment member 13 is normally biased toward the blade tip 1A even when it undergoes abrasive wear for thereby enabling the adjustment member 13 to maintain a minimal clearance at blade tip 1A.

The effect of tip clearance on the noise generated from low pressure axial flow fans.

Abstract: 3種類の低圧軸流送風機を用いて翼先端すきまS-が騒音に与える影響を実験的に調査した・その結果I動翼紬とダクトとに偏心があると高いピークの音が発生するので注意がいるがが0・6mm程度までは小さい程騒音は低下する.S-を小さくする効果は低流量域ではさらに著しく,最高効率点程度の低騒音領域が低流量域へ大幅に広がる.翼先端近傍の流れの乱れも減少し,低流量特有の離散周波数騒音の発生もなくなる.

Fuel and oxidizer turbine loss analysis

Abstract: The turbine losses for the fuel and oxidizer turbines at the FPL condition were assessed by a quasi-3D loss analysis method. This loss analysis method uses two flow codes - MERIDL and TSONIC - to calculate the flow velocities along the blade surfaces and endwalls. The velocities are then used as input to the boundary layer code - BLAYER - to calculate the friction losses due to incidence, secondary flow, and tip clearance. The loss analysis for the fuel turbine indicated an overall two-stage efficiency of about 90%. The largest loss was due to rotor tip clearance. The loss analysis for the oxidizer turbine is nearly completed. Results for the first stage of the two-stage design indicates an efficiency of about 80%, with high losses due to rotor incidence and blade and endwall friction.

Turbine blade-tip clearance excitation forces

Abstract: The results of an effort to assess the existing knowledge and plan the required experimentation in the area of turbine blade tip excitation forces is summarized The work was carried out in three phases The first was a literature search and evaluation, which served to highlight the state of the art and to expose the need for an articulated theoretical experimental effort to provide not only design data, but also a rational framework for their extrapolation to new configurations and regimes The second phase was a start in this direction, in which several of the explicit or implicit assumptions contained in the usual formulations of the Alford force effect were removed and a rigorous linearized flow analysis of the behavior of a nonsymmetric actuator disc was carried out In the third phase a preliminary design of a turbine test facility that would be used to measure both the excitation forces themselves and the flow patterns responsible for them were conducted and do so over a realistic range of dimensionless parameters