Showing papers on "Tip clearance published in 1982"

Scroll type fluid displacement apparatus

Abstract: A scroll type fluid displacement apparatus, for example a refrigerant compressor, includes reinforcing ribs on the rear side of the base plate of the orbiting scroll element to provide rigidity to the base plate. Central and peripheral thrust bearings behind the base plate provide axial restraint for the orbiting scroll element, and one of the thrust bearings is arranged to maintain the fixed and orbital wrap in predetermined angular relationship. A swirling system for the fluid inlet into the scroll apparatus separates liquid from gas in the incoming fluid before it reaches the involute scroll wraps, and the tip edges of the scroll wraps are preformed so that the tip of each scroll wrap tends to expand under exposure to a differential thermal gradient between its inner and outer region to maintain a uniform tip clearance across its entire diameter under operating conditions.

Combined turbine power plant blade tip clearance and nacelle ventilation system

Abstract: A single valve serves the multiple purpose of controlling cool airflow for either blade tip clearance control (active clearance control) or ventilation control of a jet engine installed in a nacelle of an aircraft Means for blocking flow to either or both are contemplated as a fire retarding feature

Adjusting device of tip clearance in turbo fluidic machine

Abstract: PURPOSE:To automatically control tip clearance in the point end of a moving blade, by placing the point end of the moving blade at a face-to-face position to a casing surface, providing a tapered internal peripheral surface to a casing liner, axially movably mounting the casing liner to said casing surface and using a coil spring made of shape memory alloy as a driving source of the casing liner. CONSTITUTION:The point end of a moving blade 1 is placed at a face-to-face position to the part of casings 2, and this part is removably machined, then a casing liner 5, formed with its internal peripheral surface to tapered shape, is axially movably mounted to said removal part. This liner 5 is axially movably built in a sealing cap 10, fixed to the casings 2 by screws 11, and coil springs 6, 7, contained in a housing 9, and a movable element 8, moved by balance of the both springs 6, 7, are built in the sealing cap 10. At this time, only the coil spring 6 is used with a shape memory alloy, and arranged with a different amount of extension between at starting and steady state operations. In this way, for instance, at starting, the liner 5 is moved forward to increase tip clearance between the liner and the moving blade 1.

Closed loop control for tip clearance of a gas turbine engine

Abstract: The control functions by inputting sensed operating variables indicative of engine conditions and closing the loop of said control as a function of the actual tip clearance sensed at 50 and fed back to be compared at 38 with the input signals. The error signal controls actuator 36 operating valve 34 to vary cooling air flowing to casing spray bars 18.

Gas turbine rotor tip clearance control apparatus

Abstract: A stationary shroud structure 26 surrounding a turbine rotor 22 comprises a ring 30 having a frusto conical inner surface 32 defining a small running clearance 29 with blades 24. The ring 30 is supported from a structure 42, 46 by flexible springs 38, 40 which permit axial movement of the ring from an initial position. In operation a pressure difference is formed axially across the ring 30 and a gas bearing is formed between the ring and the radial extremities of the blades 24. The pressure difference produces a first force on the ring 30 acting in a downstream direction; and the air bearing produces a second force on the ring acting in an upstream direction. Axial movement of the shroud ring from the initial position produces a third spring force on the ring acting towards the equilibrium position. The axial position of the ring 30 is determined by the resultant of the first, second and third forces and controls the running clearance. The gas bearing may be improved by the supply of air from each blade interior 58 to a cavity 52 at the blade tip. Winglets may also be provided at the tip. The ring 30 may include a heat pipe or thermosyphon to reduce thermal gradients.

Rotor tip clearance effects on overall and blade-element performance of axial-flow transonic fan stage

Abstract: The effects of tip clearance on the overall and blade-element performance of an axial-flow transonic fan stage are presented. The 50-centimeter-diameter fan was tested at four tip clearances (nonrotating) from 0.061 to 0.178 centimeter. The calculated radial growth of the blades was 0.040 centimeter at design conditions. The decrease in overall stage performance with increasing clearance is attributed to the loss in rotor performance. For the rotor the effects of clearance on performance parameters extended to about 70 percent of blade span from the tip. The stage still margin based on an assumed operating line decreased from 15.3 to 0 percent as the clearance increased from 0.061 to 0.178 centimeter.

Method and apparatus for fan blade tip clearance

Abstract: A method and apparatus for adjusting the amount of clearance between the tips of the blades of a large axial flow fan and the inner surfaces of the fan cylinder wall. A plurality of foam spacer panels are secured to the inner surfaces of the fan cylinder walls. A cutting means is attached to the outer end of the longest fan blade and extends a short distance outwardly therefrom. Rotation of the fan causes the cutting means to trim the spacer panels to achieve the required clearance. A plurality of plastic sheets are secured to the spacer panels in covering relationship thereto.

Optical tip clearance sensor for aircraft engine controls

Abstract: Aircraft gas turbine performance and efficiency are related to airfoil tip clearance. The possibility has been considered to obtain optimum performance and efficiency by reducing clearance to a safe minimum with the aid of a closed-loop tip clearance control system, which utilizes a tip clearance sensor. The use of optical sensing methods appears to represent a potential solution to the tip clearance measurement problem. Principles of sensor operation are discussed along with dimensional considerations and diffraction limitations. A description is presented of the study of the feasibility of a certain sensor, taking into account the test rig system, the optical components, and the mounting tube. Attention is also given to the operation of the feasibility-study sensor, performance estimations, the optical fiber bundle, light beam refraction, and aspects of aircraft engine implementation.

The Influence of Tip Clearance, Stage Loading, and Wall Roughness on Compressor Casing Boundary Layer Development

Abstract: An experimental program was conducted in a highly loaded, single-stage, low-speed research compressor that featured variations in blade tip clearances, shroud wall roughness, and stage loading levels. The results showed that tip clearances and stage loading levels exerted a very strong influence on casing boundary layer growth. Shroud wall roughness not only showed some effect on casing boundary layer development, but also influenced stage stall margin. The results point out the need to understand the basic flow processes that occur if realistic mathematical models are to be developed so that casing boundary layer development and its influence on compressor stage performance can be accurately predicted.Copyright © 1982 by ASME

CF6 jet engine diagnostics program. High pressure turbine roundness/clearance investigation

Abstract: The effects of high pressure turbine clearance changes on engine and module performance was evaluated in addition to the measurement of CF6-50C high pressure turbine Stage 1 tip clearance and stator out-of-roundness during steady-state and transient operation. The results indicated a good correlation of the analytical model of round engine clearance response with measured data. The stator out-of-roundness measurements verified that the analytical technique for predicting the distortion effects of mechanical loads is accurate, whereas the technique for calculating the effects of certain circumferential thermal gradients requires some modifications. A potential for improvement in roundness was established in the order of 0.38 mm (0.015 in.), equivalent to 0.86 percent turbine efficiency which translates to a cruise SFC improvement of 0.36 percent. The HP turbine Stage 1 tip clearance performance derivative was established as 0.44 mm (17 mils) per percent of turbine efficiency at take-off power, somewhat smaller, therefore, more sensitive than predicted from previous investigations.

Investigation of the tip clearance flow inside and at the exit of a compressor rotor passage

Abstract: The nature of the tip clearance flow in a moderately loaded compressor rotor is studied. The measurements were taken inside the clearance between the annulus-wall casing and the rotor blade tip. These measurements were obtained using a stationary two-sensor hot-wire probe in combination with an ensemble averaging technique. The flowfield was surveyed at various radial locations and at ten axial locations, four of which were inside the blade passage in the clearance region and the remaining six outside the passage. Variations of the mean flow properties in the tangential and the radial directions at various axial locations were derived from the data. Variation of the leakage velocity at different axial stations and the annulus-wall boundary layer profiles from passage-averaged mean velocities were also estimated.

Experimental Study and Theoretical Prediction of Secondary Flows in a Transonic Axial Flow Compressor

Abstract: Detailed time-mean measurements have been realized on a transonic axial flow compressor. Flow quantities in the secondary flow regions have been obtained. The purpose of this paper is to present some essential features which drive the secondary following development in axial compressor among others, the strong influence of secondary vortex motion on the energy transfer between the flow and the blading is displayed. Also, we study the effect of tip clearance and axial distance between blade row. A secondary flow model is used for comparisons with theoretical computations. Very good comparisons have been obtained which show the validity of the theoretical model, in particular, the decomposition of the secondary flow into a viscous part and a vortical part, using an inviscid flow as a basis.© 1982 ASME

On the Performance Prediction of a Centrifugal Compressor Scaled Up

Abstract: A centrifugal compressor performance prediction method, in which each loss generated within the compressor stage was estimated by recognizing the individual relationship with Mach number, was investigated over a wide range of sizes and types. Calculation formulae for the losses were established by analyzing test results. It was confirmed that the formulae could be applied to predict the performance levels of compressors with impeller diameters from 78 mm to 640 mm by refering to unpublished test data obtained experimentally by other researchers. From the results, it could be deduced that: (1) The wall friction losses and the secondary flow losses within the compressor decreased with increase of impeller size. (2) The leakage flow losses were found to increase when scaling up the compressor, even when tip clearance/blade height were held constant. The present paper presents a progress report of work still underway.Copyright © 1982 by ASME

Performance of a tandem-rotor/tandem-stator conical-flow compressor designed for a pressure ratio of 3

Abstract: A conical-flow compressor stage with a large radius change through the rotor was tested at three values of rotor tip clearance. The stage had a tandem rotor and a tandem stator. Peak efficiency at design speed was 0.774 at a pressure ratio of 2.613. The rotor was tested without the stator, and detailed survey data were obtained for each rotor blade row. Overall peak rotor efficiency was 0.871 at a pressure ratio of 2.952.

Recherche expérimentale et numérique sur le comportement d'une roue réversible au point de tracé

Abstract: Object of this paper is the comparison of actual flow configurations in a turbomachine with flow configurations estimated by numerical procedures Blade-to-blade solutions of the differential equation of motion are generally referred to an isolated runner, and in fixing the boundary conditions at the impeller periphery the influence of the casing or of the stationary system is completely disregarded While this may be acceptable for centripetal turbine runners, it gives unsatisfactory results in pumps and compressors, where flow pattern at the runner outlet changes considerably with the discharge rate because of the influence of the volute and/or the diffuser The present investigation has been conducted on a model reversible pump-turbine stage fitted with a fully bladed diffuser-conveyor The runner tip clearance has been traversed in pump operation in order to examine the distorsion of the flow induced by the stationary system The averaged values of flow angle, velocity and total pressure better agreed with theoretical estimates only at the matching point of runner and diffuser, which occurred at a discharge different from the bep rate At lower or higher rates the averaged value of the meridional component of the absolute velocity differed considerably from actual through-flow And also, the runner input head obtained from the averaged values of the tangential component of the velocity , which on account of the impeller losses was expected to be always greater than the total head rise through the runner, appeared to be smaller than the latter at flows below the design rate and greater at higher flows The discrepancies have been ascribed to the interaction of runner and stationary vanes, which distorted the flowlines in the clearance annulus It is also shown that fewer interference problems are present in turbine operation The stationary vanes were then removed from the diffuser channel so as to obtain an unobstructed annulus where free flow conditions would set up comparable to those existing outside an isolated runner Flow measurements showed now better consistency with theoretical estimates It could also be appreciated that the ratio of slip velocity to runner tangential velocity did not change appreciably with the rate of flow Axial distribution of velocity and pressure in the clearance annulus was also considerably affected by the presence of the diffuser vanes Known numerical solutions of the equation of motion may yield satisfactory results provided no external action is exerted on the runner flow other than the pressure forces exchanged by the runner itself For pump runner with volute or vaned diffuser casing, the boundary conditions at the impeller exit should be defined by an equation expressing the distorting effects of the stationary system on the flow