Showing papers by "Rolls-Royce Limited published in 1986"

Method for eliminating, or minimizing the effects of, defects in materials

Abstract: A method is described for the manufacture of articles in defect immunized materials in which the defects are eliminated, or broken up and oriented in such manner as to minimize their harmful effects on the article. Referring to FIG. 1e, a rotor disc for a gas turbine engine is formed to an approximate shape by stacking together "sticks" 5 of material in an evacuated container and bonding them together by a hot isostatic pressing process. The "sticks" 5 are produced by extruding a starting body, for example, of powder material, to produce an elongation of up to twenty times and then cutting them to the appropriate length. By this means any non-metallic inclusions in the powder are broken up, inspection of the sticks and rejection of defective ones becomes easier, and the sticks can be oriented so that the effects of any remaining defects can be minimized.

Gas turbine engine gaseous fuel injector

Abstract: A gaseous fuel injector for an industrial gas turbine plant is arranged to operate on fuel produced from a coal gasifier for normal running or natural gas for starting purposes. The injector is self purging to prevent the ingestion of natural gas or combustion products into the passage of the fuel injector for the lower calorific value fuel. The fuel injector has fuel ducts and gas flow passages in a duct assembly attached to the head of each flame tube of a gas generator. For starting, natural gas flows through the duct and the central passage, while air flows through the outer passage preventing ingestion of natural gas and combustion products into the outer fuel duct. When running on fuel from a coal gasifier both ducts run full of fuel, as do the passages. The air for the coal gasifier may be provided by the gas generator.

Brush seal manufacture

Abstract: An apparatus for use in the manufacture of brush seals which comprise a plurality of filaments of brush material sandwiched between two sideplates. The apparatus comprises a workplate onto which is mounted one of the sideplates of the seal. A plurality of first clamping members clamp against the sideplate. Each member can be lifted to enable a tuft of brush material to be inserted and clamped against the sideplate. To enable more than one layer of tufts to be built up on the sideplate a second clamping means is provided to enable the first clamping members to be released. An indexing mechanism allows the first clamping members to be moved relative to the clamped tufts and when the assembly of tufts is complete a second sideplate is clamped onto the tufts and first sideplate. The apparatus also includes means for cutting a prewound ribbon of adhesively bonded wires into short lengths to form the tufts.

The Importance of Circumferential Non-uniformities in a Passage-Averaged Quasi-Three-Dimensional Turbomachinery Design System

Abstract: The purpose of this paper is to show, for both rotating and non-rotating blade rows, the importance of including circumferential non-uniform flow effects in a quasi-three-dimensional blade design system. The paper follows on from previous publications on the system in which the mathematical analysis and computerised system are detailed. Results are presented for a different stack of the nozzle guide vane presented previously and for a turbine rotor. In the former case it is again found that the blade force represents a major contribution to the radial pressure gradient, while for the rotor the radial pressure gradient it is dominated by centrifugal effects. In both examples the effects of circumferential non-uniformities are detailed and discussed.Copyright © 1985 by ASME

A different view of the assumed stress hybrid method

Abstract: A somewhat unconventional, yet simple, derivation of the assumed stress hybrid formulation is presented in which its relationship with displacement and stress-based finite element models is demonstrated. This gives insight into the hybrid method and shows that it represents a least energy fit of an equilibrium stress field to a displacement model strain field. By this means the attributes of both fields may be exploited in extending the analysis scope of hybrid models.

The Effect of Reynolds Number and Velocity Distribution on LP Turbine Cascade Performance

Abstract: Because of the laminar boundary-layer’s inability to withstand moderate adverse pressure gradients without separating, profile losses in LP turbines operating at low Reynolds numbers can be high. The choice of design pressure distribution for the blading is thus of great importance.Three sub-sonic LP turbine nozzle-guide-vane cascade profiles have been tested over a wide range of incidence, Mach number and Reynolds number. The three profiles are of low, medium and high deflection and, as such, display significantly different pressure distributions. The tests include detailed boundary-layer traverses, trailing-edge base-pressure monitoring and oil-flow visualisation.It is shown that the loss variation with Reynolds number is a function of pressure distribution and that the trailing-edge loss component is dominant at low Reynolds number. The importance of achieving late flow transition — rather than separation — in the suction-surface trailing-edge region is stressed.The paper concludes by remarking on the advantages and practical implications of each loading design.Copyright © 1986 by ASME

The role of a mixed design and analysis method in a turbomachinery blade design system

Abstract: In this paper the requirements of a design method are considered, with particular emphasis given to the needs of designers of multi-stage compressors. It is concluded that what is required is a quasi three-dimensional compatible design and analysis method. The extension of the finite element blade-to-blade method FINSUP to include a design calculation compatible with the analysis calculation is presented. In this method, changes to the blade shape are modelled using a surface transpiration model. By displacing every point on the blade surface individually, the relationship between the blade shape and the surface velocity is determined. It is shown that with a Newton–Raphson procedure adopted in the method, a very efficient manner of introducing the design option is possible. As a consequence the resulting program is fast and completely interactive. An example of the method is shown in which a transonic compressor blade with a suction surface shock is redesigned to give a blade with controlled suction surface diffusion.

Comparison of techniques for residual stress determination in a bead on plate titanium sample

Abstract: Residual stress determination has been carried out on production welds to provide engineering data. A parting out technique has been used in which a strain gauged through thickness slug of material is removed from the weld area. The centre hole technique has been used with the blind hole in the weld material. There were differences between the results from the two techniques and a fully penetrant bead on plate fatigue sample with the bead running axially was used in order to compare the two techniques in more detail. After parting out, the layer removal technique was carried out in order to provide a relatively detailed through thickness residual stress distribution in order to explain the differences between the results from the centre hole and parting out techniques.