A Duncan Walker

Loughborough University | Lough · Department of Aeronautical and Automotive Engineering

The compression system in modern turbofan engines is split into stages linked by transition ducts. Downstream of the low-pressure system, a handling bleed is often required and, in conjunction with structural vanes, can introduce component interactions which compromise aerodynamic performance. In this paper a fully annular, low-speed test facility...

The drive towards net-zero carbon emissions is favoring lighter, more compact compressors. For the connecting S-shaped ducts, a larger radial offset must be accommodated within the shortest length ensuring no boundary layer separation and minimum losses. The duct aerodynamic design is however significantly affected by highly complex flow field inte...

This paper examines a lifted turbulent H2/N2 diffusion flame in a vitiated co-flow, using a Flamelet Generated Manifold (FGM) combustion model. FGM is commonly used in combusting simulations in the gas turbine industry as it is cheaper than solving detailed chemistry as part of the simulation. The aim of this paper is to examine the ability of the...

The compression system in modern turbofan engines is split into several stages linked by s-shaped transition ducts. Downstream of the low-pressure system, a handling bleed is often required for off-design performance and/or to extract ice/water and foreign debris prior to the air entering the high-pressure compression stages. The inclusion of this...

Ski jumping is a highly competitive sport, where the distance jumped is greatly dependent on the aerodynamic effects of the athlete’s posture. In the current paper a wind tunnel experiment was conducted to generate a parametric database of the effects of posture on aerodynamics and to compute the aerodynamic force coefficients. The parameters consi...

Fluid off-takes and complex delivery ducts are common in many engineering systems but designing them can be a challenging task. At the conceptual design phase many system parameters are open to consideration and preliminary design studies are necessary to instruct the conceptualisation process in an iterative development of design ideas. This paper...

This paper uses Computational Fluid Dynamics to investigate the effect of an engine handling bleed situated on the outer casing downstream of the last rotor stage of a low-pressure compressor and upstream of the outlet guide vane and S-shaped duct. The model, validated against existing experimental data, utilized an unsteady RANS solver incorporati...

The need to reduce fuel-burn and emissions, is pushing turbofan engines towards geared architectures with higher bypass ratios and small ultra-high-pressure ratio cores. However, this increases the radial offset between compressor spools leading to a more challenging design for compressor transition ducts. For the duct connecting the fan to the eng...

For preliminary design of compressor transition ducts, knowledge-based tools for the rapid assessment of aerodynamic performance of S-shaped ducts are not currently available in the open literature. This is due to the highly complex flow developing under the combined influence of pressure gradients and streamline curvature. This paper presents a ne...

The need to reduce fuel-burn and CO2 emissions, is pushing turbofan engines towards geared architectures with very high bypass-ratios and small ultra-high-pressure ratio core engines. However, this increases the radial offset between compressor spools and leads to a more challenging design for the compressor transition ducts. To minimise weight, th...

The S-shaped duct which transfers flow from the low-pressure fan to the engine core in large civil turbofans presents a challenging problem. Aerodynamically it has a spatially and temporarily varying inlet flow combined with a complex flow field which develops under the combined influence of pressure gradients and streamline curvature. It must also...

To reduce fuel-burn and CO2 emissions from aero gas turbines there is a drive towards very-high bypass ratio and smaller ultra-high-pressure ratio core engine technologies. However, this makes the design of the ducts connecting various compressor spools more challenging as the larger required radius change increases their aerodynamic loading. This...

The S-shaped duct which transfers flow from the low-pressure fan to the engine core of modern large civil turbofans presents a challenging design problem. Aerodynamically it must accommodate a spatially and temporarily non-uniform inlet in conjunction with a complex flow field which will develop under the combined influence of pressure gradients an...

To reduce fuel-burn and emissions there is a drive towards higher bypass ratio and smaller high-pressure ratio core engines. This makes the design of the ducts connecting compressor spools more challenging as the higher radius change increases aerodynamic loading. This is exacerbated at inlet to the engine core by fan root flow which is characteris...

The aim of this research was to improve the understanding of the complex flow featuresfound around a wheel and wheelhouse and to examine how the lateral displacement of the wheelaffects these features and the production of exhibited pressures and forces. A bespoke rotatingwheel rig and accompanying wheelhouse with a fully-pressure-tapped wheel arch...

Lean burn combustion is currently a preferred technology to meet the future low emission requirements faced by aero gas turbines. Previous work has shown that the increased air mass flow and size of lean burn fuel injector alters the necessary redistribution of the airflow leaving the high-pressure compressor. This can lead to flow field non-unifor...

To reduce fuel-burn and CO2 emissions from aero gas turbines there is a drive towards very-high bypass ratio and smaller ultra-high-pressure ratio core engine technologies. However, this makes the design of the ducts connecting various compressor spools more challenging as the higher required radius change increases their aerodynamic loading. This...

As aero gas turbine designs strive for ever greater efficiencies, the trend is for engine overall pressure ratios to rise. Although this provides greater thermal efficiency, it means that cycle temperatures also increase. One potential solution to managing the increasing temperatures is to employ a cooled cooling air system. In such a system, a pur...

Impingement cooling is commonly employed in gas turbines to control the turbine tip clearance. During the design phase, computational fluid dynamics (CFD) is an effective way of evaluating such systems but for most turbine case cooling (TCC) systems resolving the small scale and large number of cooling holes is impractical at the preliminary design...

It has been known for a sometime that the compressor exit profile can have a significant effect on the overall performance of the fuel injector. This effect has been increased recently with the advent of larger leaner injection systems. With a modern gas turbine combustion system the fuel injectors are presented with a non-uniform feed generated by...

Particle Image Velocimetry (PIV) has been used to study the complex flowfield created by simulated battle damage to a two-dimensional wing. Computational Fluid Dynamics (CFD) predictions have also been used for validation of internal cavity flow. Two damage cases were selected for the study; both cases were simulated using a single hole with diamet...

As aero gas turbines strive for higher efficiencies and reduced fuel burn, the trend is for engine overall pressure ratio to increase. This means that engine cycle temperatures will increase and that cooling of various engine components, for example the high pressure turbine, is becoming more difficult. One solution is to employ a cooled cooling ai...

As aero gas turbine designs strive for ever greater efficiencies the trend is for engine overall pressure ratios to rise. Although this provides greater thermal efficiency it means that cycle temperatures also increase. Traditionally turbines have been the focus of cooling schemes to enable them to survive high temperatures. However, it is envisage...

To manage the increasing turbine temperatures of future gas turbines a cooled-cooling air system has been proposed. In such a system some of the compressor efflux is diverted for additional cooling in a heat exchanger located in the by-pass duct. The cooled air must then be returned, across the main gas path, to the engine core for use in component...

In a multistage intermediate pressure compressor an efficiency benefit may be gained by reducing reaction in the rear stages, and allowing swirl to persist at the exit. This swirl must now be removed within the transition duct that is situated between the intermediate and high pressure compressor spools, in order to present the downstream compresso...

To meet the technological challenges of lean burn, low emission combustion knowledge based design methodologies must be developed. This paper presents back-to-back, time-averaged and time-resolved aerodynamic measurements made using a unique state-of-the-art fully annular isothermal test facility incorporating a 1/2 stage axial compressor and a typ...

Numerical methods are invaluable in the initial phase of a project for evaluating potential design solutions. The design of aircraft gas turbine combustor external aerodynamics is one example where such methodology is applied. The system is geometrically complex and requires a high fidelity mesh to resolve small geometric features, such as the inje...

The development of radical new aeroengine technologies will be key to delivering the step changes in aircraft environmental performance required to meet future emissions legislation. Intercooling has the potential for higher overall pressure ratios, enabling reduced fuel consumption and/or lower compressor delivery air temperatures, and therefore r...

This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors. Any resulting non-uniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance. The geometry considered is typical of the lean burn systems currently being proposed for fut...

In engineering applications, diffuser performance is significantly affected by its boundary conditions. In a gas turbine combustion system, the space envelope is limited, the inlet conditions are generated by upstream turbomachinery, and the downstream geometry is complex and in close proximity. Published work discusses the impact of compressor-gen...

The ability to design S-shaped ducts with high aerodynamic loading is advantageous from a performance and/or weight saving perspective. However, the radial pressure gradients required to turn the flow produce strong pressure gradients in the axial direction. This promotes the likelihood of flow separation from the inner casing as the loading is inc...

Within gas turbines the ability to design shorter aggressive S-shaped ducts is advantageous from a performance and weight saving perspective. However, current design philosophies tend to treat the S-shaped duct as an isolated component, neglecting the potential advantages of integrating the design with the upstream or downstream components. In this...

Within the compression system of a gas turbine engine a significant amount of air is removed to fulfil various requirements associated with cooling, ventilation and sealing. Flow is usually removed through off-takes located in regions where space is restricted, whilst the flow is highly complex containing blade wakes, secondary flows and other flow...

This item is closed access. It is an article from the serial, Journal of Engineering for Gas Turbines and Power [© ASME ]. For more information on how to obtain this article please visit the ASME Digital Library, http://www.asmedl.org/ . The increasing demand to reduce fuel burn, hence CO2 emissions, from the gas turbine requires efficient diffusio...

Economic and environmental concerns are a major driving force behind the development of aero gas turbine technology, with ever more stringent legislation dictating significant reductions in specific fuel consumption and pollutant emissions. Intercooling has long been of interest as it has the potential for lower compressor delivery and turbine cool...

This item is closed access. It is a conference paper [© ASME ]. For more information on how to obtain this article please visit the ASME Digital Library, http://www.asmedl.org/ . The paper reports an experimental investigation into the possibility of increased interactions between combustor external aerodynamics and upstream components e.g. pre-dif...

This item is closed access. It is a conference paper [© ASME ]. For more information on how to obtain this article please visit the ASME Digital Library, http://www.asmedl.org/ . The paper uses experimental measurements to characterise the extent that improved external aerodynamic performance (reduced total pressure loss, increased flow quality) of...

Modern; low-emission, radially staged combustors present the diffuser with a flametube of increasing radial depth. However, conventional diffuser systems limit the amount of flow diffusion and deflection that can be achieved in a given length, and, therefore,unconventional configurations such as hybrid or bled diffusers must be considered. This pap...

The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the pre-diffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This...

A doctoral thesis submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy. Diffusers are essential in gas turbine combustors, decelerating the compressor efflux prior to the combustion chamber to reduce total pressure losses. Modern, low emission, radially staged combustors require even more diffusion due to the in...