Mark Savill

Use of Parallel Coordinates for Post-Analyses of Multi-Objective Aerodynamic Design Optimisation in Turbomachinery

A novel approach for the post-analysis of design optimisation processes is suggested. The technique is based on parallel coordinates representation of multi-dimensional design spaces. By applying this methodology, the geometrical characteristics of optimum blade shapes of axial compressors responsible for improved behaviour of crucial o w characteristics possibly can be identied and classied according to their impact to the overall eciency of the turbomachine. Hence, geometrical features are directly associated with physical o w characteristics in highly complex aerodynamic domains. The main objective of this approach is to identify and reveal the physical mechanisms, which are responsible for highly ecien t turbomachines and which are obtainable by no other means, to the researchers and designers. Furthermore, the technique can be directly applied to any type of computational engineering design problem.

Multi-objective optimisation of turbomachinery blades using tabu search

This paper describes the application of a new multi-objective integrated turbomachinery blade design optimisation system. The system combines an existing geometry parameterisation scheme, a well-established CFD package and a novel multi-objective variant of the Tabu Search optimisation algorithm. Two case studies, in which the flow characteristics most important to the overall performance of turbomachinery blades are optimised, are investigated. Results are presented and compared with a previous (single-objective) investigation of the problem.

Biobjective optimisation of preliminary aircraft trajectories

The protection of the environment against pollutants produced by aviation is of great concern in the 21st century. Among the multiplicity of proposed solutions, modifying flight profiles for existing aircraft is a promising approach. The aim is to deliver and understand the trade-off between environmental impact and operating costs. This work will illustrate the optimisation process of aircraft trajectories by minimising fuel consumption and flight time for the climb phase of an aircraft that belongs to A320 category. To achieve this purpose a new variant of a multi-objective Tabu Search optimiser was evolved and integrated within a computational framework, called GATAC, that simulates flight profiles based on altitude and speed.

Multi-Criteria Optimisation of Turbomachinery Blades: Investigating the Trade-Off Surface

This paper describes the application of a new multi-objective integrated turbomachinery blade design optimisation system. The system combines an existing geometry parameterisation scheme, a well-established CFD package and a novel multi-objective variant of the Tabu Search optimisation algorithm. Case studies, in which the o w characteristics most important to the overall performance of turbomachinery blades are optimised, are investigated.

COMPUTATIONAL ENGINEERING DESIGN FOR MICRO-SCALE COMBUSTORS

At present, optimisation is an enabling technology in innovation. Multi-objective and multi-disciplinary design tools are essential in the engineering design process, and have been applied successfully in aerospace and turbomachinery applications extensively. These approaches give insight into the design space and identify the trade-offs between the competing performance measures satisfying a number of constraints at the same time. It is anticipated here that the same benefits can be obtained for the design of micro-scale combustors. In this paper, a multi-disciplinary automated design optimisation system was developed for this purpose, which comprises a commercial computational fluid dynamics package and a multi-objective variant of the Tabu Search optimisation algorithm. The main objectives that are considered in this study are to optimise the main micro-scale combustor design characteristics and to satisfy manufacturability considerations from the very beginning of the whole design operation. Hydrogen-air combustion as well as 14 geometrical and 2 operational parameters are used to describe and model the design problem. Two illustrative test cases will be presented, in which the most important device operational requirements are optimised, and the efficiency of the developed optimisation system is demonstrated. The identification, assessment and suitability of the optimum design configurations are discussed in detail.Copyright

Evaluating NOx and CO emissions of bio-SPK fuel using a simplified engine combustion model: A preliminary study towards sustainable environment

Awareness of environmental and economic issues associated with fossil fuel has led to the exploration of alternative fuels for aviation. Analysis and measurements of alternative fuel using real aircraft engines are complex and costly. Thus, evaluation only through computation is an option at present. This paper presents an analysis of aircraft engine emissions, particularly NOx and CO, from the blend of bio-synthetic paraffinic kerosene (bio-SPK) fuel with kerosene using a simplified gas emission model. Three different fuels, namely, a conventional aviation fuel Jet-A, Jatropha bio-SPK and Camelina bio-SPK were tested as pure and as blends with Jet-A. Chemical properties of the tested fuels were introduced into HEPHAESTUS, an in-house gas emission software developed in Cranfield University. HEPHAESTUS was developed based on the physics-based approach by incorporating a number of stirred reactors to predict NOx, CO, UHC and soot. Gaseous emissions generated from kerosene were observed to follow the trends provided by the ICAO databank. The capability of HEPHAESTUS in predicting the NOx and CO level from biofuel is yet to be explored. The level of NOx and CO predicted in this study followed the trends shown in the literature, although they quantitatively differed. Compared to Jet-A, NOx decreased and CO increased as the percentage of Jatropha bio-SPK and Camelina bio-SPK in the mixture increased. NOx reduction was consistent with the reduction in flame temperature because NOx generation considered in the model was dominantly based on thermal NOx. In contrast, increases in CO were due to low flame temperature that led to incomplete combustion. The consistency of the results obtained showed that the computational work performed in this study as an initial step toward the prediction of emission level of biofuels was successful. However, further studies on the experimental work or computational fluid dynamic simulation is essential.

Comparative study of alternative biofuels on aircraft engine performance

Aviation industries are vulnerable to the energy crisis and simultaneously posed environmental concerns. Proposed engine technology advancements could reduce the environmental impact and energy consumption. Substituting the source of jet fuel from fossil-based fuel to biomass-based fuel will help reduce emissions and minimize the energy crisis. The present paper addresses the analysis of aircraft engine performance in terms of thrust, fuel flow and specific fuel consumption at different mixing ratio percentages (20%, 40%, 50%, 60% and 80%) of alternative biofuel blends already used in flight test (Algae biofuel, Camelina biofuel and Jatropha biofuel) at different flight conditions. In-house computer software codes, PYTHIA and TURBOMATCH, were used for the analysis and modeling of a three-shaft high-bypass-ratio engine which is similar to RB211-524. The engine model was verified and validated with open literature found in the test program of bio-synthetic paraffinic kerosene in commercial aircraft. The results indicated that lower heating value had a significant influence on thrust, fuel flow and specific fuel consumption at every flight condition and at all mixing ratio percentages. Wide lower heating value differences between two fuels give a large variation on the engine performances. Blended Kerosene–Jatropha biofuel and Kerosene–Camelina biofuel showed an improvement on gross thrust, net thrust, reduction of fuel flow and specific fuel consumption at every mixing ratio percentage and at different flight conditions. Moreover, the pure alternative of Jatropha biofuel and Camelina biofuel gave much better engine performances. This was not the case for the Kerosene–Algae blended biofuel. This study is a crucial step in understanding the influence of different blended alternative biofuels on the performance of aircraft engines.

Effects of biofuels properties on aircraft engine performance

Purpose – The purpose of this paper is to examine the effects of heat capacity and density of biofuels on aircraft engine performance indicated by thrust and fuel consumption. Design/methodology/approach – The influence of heat capacity and density was examined by simulating biofuels in a two-spool high-bypass turbofan engine running at cruise condition using a Cranfield in-house engine performance computer tool (PYTHIA). The effect of heat capacity and density on engine performance was evaluated through a comparison between kerosene and biofuels. Two types of biofuels were considered: Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK). Findings – Results show an increase in engine thrust and a reduction in fuel consumption as the percentage of biofuel in the kerosene/biofuel mixture increases. Besides a low heating value, an effect of heat capacity on increasing engine thrust and an effect of density on reducing engine fuel consumption are observed. Pr...

Computational design of S-Duct intakes for distributed propulsion

Purpose – The purpose of this paper is to identify efficient methods and tools for the design of distributed propulsion architectures. Design/methodology/approach – Multi-objective computational aerodynamic design optimisation of an S-Duct shape. Findings – Both duct pressure loss and flow distortion through such a duct can be reduced by wall-curvature changes. Research limitations/implications – Initial simplified study requires higher fidelity computational fluid dynamics & design sensitivity follow-up. Practical implications – Shape optimisation of an S-Duct intake can improve intake efficiency and reduce the risk of engine-intake compatibility problems. Social implications – Potential to advance lower emissions impact from distributed propulsion aircraft. Originality/value – Both the duct loss and flow distortion can be simultaneously reduced by significant amounts.

Large eddy simulation of airfoil self-noise using OpenFOAM

Purpose The purpose of this paper is to investigate airfoil self-noise generation and propagation by employing a hybrid method based on the Large-eddy simulation (LES) approach and Curle’s acoustic analogy as implemented in OpenFOAM. Design/methodology/approach Large-eddy simulation of near-field flow over a NACA6512-63 airfoil at zero angle of attack with a boundary layer trip at Re = 1.9 × 105 has been carried out using the OpenFOAM® CFD code. Calculated flow results are compared with published experimental data. The LES includes the wind-tunnel installation effects by using appropriate inflow boundary conditions obtained from a RANS k-ω SST model computation of the whole wind tunnel domain. Far-field noise prediction was achieved by an integral method based on Curle’s acoustic analogy. The predicted sound pressure levels are validated against the experimental data at various frequency ranges. Findings The numerical results presented in this paper show that the flow features around a NACA6512-63 airfoil...