Axial compressor response to inlet flow distortions by a CFD analysis

The usual approach to compressor design considers uniform inlet flow characteristics. Especially in aircraft applications, the inlet flow is quite often non uniform, and this can result in severe performance degradation. The magnitude of this phenomenon is amplified in military engines due to the complexity of inlet duct configurations and the extreme flight conditions. CFD simulation is an innovative and powerful tool for studying inlet distortions and can bring this inside the very early phases of the design process. This project attempts to study the effects of inlet flow distortions in an axial flow compressor trying to minimize the use computer resources and computational time. The first stage of a low bypass ratio compressor has been analyzed and its clean and distorted performance compared outlining the principal changes due to uneven flow distribution: drop in mass flow, increase in pressure and temperature ratios, decrease in surge margin. Three different studies have then been conducted to better understand the effects of the level, the type and the frequency of the distortion.

A comparison of methods for assessing the lifetime reliability of a moored FPSO

Current design codes for floating offshore structures are based on measures of short-term reliability. That is, a design storm is selected via an extreme value analysis of the environmental conditions and the reliability of the vessel in that design storm is computed. Although this approach yields valuable information on the vessel motions, it does not produce a statistically rigorous assessment of the lifetime probability of failure. An alternative approach is to perform a long-term reliability analysis in which consideration is taken of all sea states potentially encountered by the vessel during the design life. Although permitted as a design approach in current design codes, the associated computational expense generally prevents its use in practice. A new efficient approach to long-term reliability analysis is presented here, the results of which are compared with a traditional short-term analysis for the surge motion of a representative moored FPSO in head seas. This serves to illustrate the failure probabilities actually embedded within current design code methods, and the way in which design methods might be adapted to achieve a specified target safety level.

An evaluation of volumetric interest points

This paper presents the first performance evaluation of interest points on scalar volumetric data. Such data encodes 3D shape, a fundamental property of objects. The use of another such property, texture (i.e. 2D surface colouration), or appearance, for object detection, recognition and registration has been well studied; 3D shape less so. However, the increasing prevalence of depth sensors and the diminishing returns to be had from appearance alone have seen a surge in shape-based methods. In this work we investigate the performance of several detectors of interest points in volumetric data, in terms of repeatability, number and nature of interest points. Such methods form the first step in many shape-based applications. Our detailed comparison, with both quantitative and qualitative measures on synthetic and real 3D data, both point-based and volumetric, aids readers in selecting a method suitable for their application. © 2011 IEEE.

Improving co-development through process alignment

There has been a recent surge of enthusiasm icithin tlie automotive industry to build closer supplier relationships idthin the area of product development. One concept deemed central to these relationships is the alignment of development processes between the collaborating organizations, an area that is expanded upon idthin this paper. We suggest that synchronization can be achieved through the four key steps of process standardization, knowledge sliaring, alignment of existing practices, and continuous elimination oftcaste idthin the joint development cycles. A methodology for implementing these stages is presented along idth the underlying prindples on which it is based - the importance of joint teamworking and multi-company involvement idthin the alignment process is higlilighted. © MCB University Press.

Unstable behavior of low and high speed compressors

By far the greater part of our understanding about stall and surge in axial compressors comes from work on low-speed laboratory machines. As a general rule, these machines do not model the compressibility effects present in high-speed compressors and therefore doubt has always existed about the application of low-speed results to high-speed machines. In recent years interest in active control has led to a number of studies of compressor stability in engine type compressors. This paper presents new data from an eight-stage fixed geometry engine compressor and compares this with low-speed laboratory data.