scholarly journals Aerodynamic Design of Separate-Jet Exhausts for Future Civil Aero-engines—Part I: Parametric Geometry Definition and Computational Fluid Dynamics Approach

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Ioannis Goulos ◽  
Tomasz Stankowski ◽  
John Otter ◽  
David MacManus ◽  
Nicholas Grech ◽  
...  
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Design Parameters ◽  
Small Scale ◽  
Aerodynamic Design ◽  
Shape Transformation ◽  
Design Variables ◽  
Aero Engines ◽  
Engine Cycle ◽  
Exhaust Systems

This paper presents the development of an integrated approach which targets the aerodynamic design of separate-jet exhaust systems for future gas-turbine aero-engines. The proposed framework comprises a series of fundamental modeling theories which are applicable to engine performance simulation, parametric geometry definition, viscous/compressible flow solution, and design space exploration (DSE). A mathematical method has been developed based on class-shape transformation (CST) functions for the geometric design of axisymmetric engines with separate-jet exhausts. Design is carried out based on a set of standard nozzle design parameters along with the flow capacities established from zero-dimensional (0D) cycle analysis. The developed approach has been coupled with an automatic mesh generation and a Reynolds averaged Navier–Stokes (RANS) flow-field solution method, thus forming a complete aerodynamic design tool for separate-jet exhaust systems. The employed aerodynamic method has initially been validated against experimental measurements conducted on a small-scale turbine powered simulator (TPS) nacelle. The developed tool has been subsequently coupled with a comprehensive DSE method based on Latin-hypercube sampling. The overall framework has been deployed to investigate the design space of two civil aero-engines with separate-jet exhausts, representative of current and future architectures, respectively. The inter-relationship between the exhaust systems' thrust and discharge coefficients has been thoroughly quantified. The dominant design variables that affect the aerodynamic performance of both investigated exhaust systems have been determined. A comparative evaluation has been carried out between the optimum exhaust design subdomains established for each engine. The proposed method enables the aerodynamic design of separate-jet exhaust systems for a designated engine cycle, using only a limited set of intuitive design variables. Furthermore, it enables the quantification and correlation of the aerodynamic behavior of separate-jet exhaust systems for designated civil aero-engine architectures. Therefore, it constitutes an enabling technology toward the identification of the fundamental aerodynamic mechanisms that govern the exhaust system performance for a user-specified engine cycle.

Aerodynamic Design of Separate-Jet Exhausts for Future Civil Aero-engines—Part II: Design Space Exploration, Surrogate Modeling, and Optimization

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Ioannis Goulos ◽  
John Otter ◽  
Tomasz Stankowski ◽  
David MacManus ◽  
Nicholas Grech ◽  
...  
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Design Tool ◽  
Civil Aviation ◽  
Aerodynamic Design ◽  
Aero Engines ◽  
Exhaust Systems

The aerodynamic performance of the bypass exhaust system is key to the success of future civil turbofan engines. This is due to current design trends in civil aviation dictating continuous improvement in propulsive efficiency by reducing specific thrust and increasing bypass ratio (BPR). This paper aims to develop an integrated framework targeting the automatic design optimization of separate-jet exhaust systems for future aero-engine architectures. The core method of the proposed approach is based on a standalone exhaust design tool comprising modules for cycle analysis, geometry parameterization, mesh generation, and Reynolds-averaged Navier–Stokes (RANS) flow solution. A comprehensive optimization strategy has been structured comprising design space exploration (DSE), response surface modeling (RSM) algorithms, as well as state-of-the-art global/genetic optimization methods. The overall framework has been deployed to optimize the aerodynamic design of two civil aero-engines with separate-jet exhausts, representative of current and future engine architectures, respectively. A set of optimum exhaust designs have been obtained for each investigated engine and subsequently compared against their reciprocal baselines established using the current industry practice in terms of exhaust design. The obtained results indicate that the optimization could lead to designs with significant increase in net propulsive force, compared to their respective notional baselines. It is shown that the developed approach is implicitly able to identify and mitigate undesirable flow-features that may compromise the aerodynamic performance of the exhaust system. The proposed method enables the aerodynamic design of optimum separate-jet exhaust systems for a user-specified engine cycle, using only a limited set of standard nozzle design variables. Furthermore, it enables to quantify, correlate, and understand the aerodynamic behavior of any separate-jet exhaust system for any specified engine architecture. Hence, the overall framework constitutes an enabling technology toward the design of optimally configured exhaust systems, consequently leading to increased overall engine thrust and reduced specific fuel consumption (SFC).

Modifications of class-shape transformation driven by aerodynamic concerns over leading-edge region

2021 ◽  
pp. 095441002098457
Author(s):  
Shuyue Wang ◽  
Cong Wang ◽  
Gang Sun
Keyword(s):  
Design Space ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Shape Error ◽  
Edge Region ◽  
Aerodynamic Design ◽  
Shape Transformation ◽  
Geometrical Representation ◽  
Design Variables ◽  
Representation Method

Geometrical representation method plays a fundamental role in aerodynamic design in that it makes preparation for design space. A good design space should be composed of design variables that are more likely to attain the solution to the problem than others. This study finds that due to the characteristics of Bernstein polynomials, a conventional class-shape transformation (CST) geometrical representation method is insufficiently focused on the leading-edge region of airfoils/wings. However, more aerodynamic attention is required there because it has strong relationship with the aerodynamic performance of whole geometry. The lack of design variables assigned to the leading-edge region is likely to compromise the effort in finding better optimization results in design space. While maintaining the convenience and accuracy of conventional CST, this study proposes two types of modifications to add more aerodynamic insights into the leading-edge region: (1) an approach of supplementary vertical CST aiming to describe the leading-edge region upon the fitting result of conventional CST; (2) an approach of globally transforming airfoil surfaces into a single-value function with respect to x-direction so that the leading-edge region avoids being split up into two separate parts. With those two modifications, the leading edge can be put to the center of geometric description by rotating the local coordinate system after tackling some other issues that come with the operation. Modification 1 is intuitive, although it requires additional attention to some parameters for the continuity between the leading-edge region and other regions of the airfoil. Modification 2 is convenient to implement, but has limitations on accuracy control because the result of shape error has to account for the introduction global transforming function. Two modifications are illustrated, and their applications are discussed in the study, showing the perspective of being utilized in aerodynamic design that involves delicate difference of aerodynamic performance brought by variations of leading-edge shape.

scholarly journals Design optimisation of separate-jet exhausts for the next generation of civil aero-engines

2018 ◽  
Vol 122 (1256) ◽  
pp. 1586-1605 ◽  
Author(s):  
I. Goulos ◽  
J. Otter ◽  
T. Stankowski ◽  
D. Macmanus ◽  
N. Grech ◽  
...  
Keyword(s):  
Design Space Exploration ◽  
Exhaust System ◽  
Cost Effective ◽  
Aerodynamic Design ◽  
Next Generation ◽  
Shape Transformation ◽  
Flow Features ◽  
Gas Turbine Exhaust ◽  
Aero Engines ◽  
Definition Of

ABSTRACTThe next generation of civil large aero-engines will employ greater bypass ratios compared with contemporary architectures. This results in higher exchange rates between exhaust performance and specific fuel consumption (SFC). Concurrently, the aerodynamic design of the exhaust is expected to play a key role in the success of future turbofans. This paper presents the development of a computational framework for the aerodynamic design of separate-jet exhaust systems for civil aero-engines. A mathematical approach is synthesised based on class-shape transformation (CST) functions for the parametric geometry definition of gas-turbine exhaust components such as annular ducts and nozzles. This geometry formulation is coupled with an automated viscous and compressible flow solution method and a cost-effective design space exploration (DSE) approach. The framework is deployed to optimise the performance of a separate-jet exhaust for very-high-bypass ratio (VHBR) turbofan engine. The optimisations carried out suggest the potential to increase the engine’s net propulsive force compared with a baseline architecture, through optimum exhaust re-design. The proposed method is able to identify and alleviate adverse flow-features that may deteriorate the aerodynamic behaviour of the exhaust system.

scholarly journals Evaluation of Static Mapping for Dynamic Space-Shared Multi-task Processing on FPGAs

2021 ◽  
Author(s):  
Umar Ibrahim Minhas ◽  
Roger Woods ◽  
Georgios Karakonstantis
Keyword(s):  
High Performance ◽  
Design Space Exploration ◽  
Design Space ◽  
System Throughput ◽  
Design Parameters ◽  
Temporal Constraints ◽  
Shared Resources ◽  
Task Processing ◽  
High Level ◽  
Performance Computing

AbstractWhilst FPGAs have been used in cloud ecosystems, it is still extremely challenging to achieve high compute density when mapping heterogeneous multi-tasks on shared resources at runtime. This work addresses this by treating the FPGA resource as a service and employing multi-task processing at the high level, design space exploration and static off-line partitioning in order to allow more efficient mapping of heterogeneous tasks onto the FPGA. In addition, a new, comprehensive runtime functional simulator is used to evaluate the effect of various spatial and temporal constraints on both the existing and new approaches when varying system design parameters. A comprehensive suite of real high performance computing tasks was implemented on a Nallatech 385 FPGA card and show that our approach can provide on average 2.9 × and 2.3 × higher system throughput for compute and mixed intensity tasks, while 0.2 × lower for memory intensive tasks due to external memory access latency and bandwidth limitations. The work has been extended by introducing a novel scheduling scheme to enhance temporal utilization of resources when using the proposed approach. Additional results for large queues of mixed intensity tasks (compute and memory) show that the proposed partitioning and scheduling approach can provide higher than 3 × system speedup over previous schemes.

scholarly journals Effects of Robust Convex Optimization on Early-Stage Design Space Exploratory Behavior

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Priya P. Pillai ◽  
Edward Burnell ◽  
Xiqing Wang ◽  
Maria C. Yang
Keyword(s):  
Robust Optimization ◽  
Design Space Exploration ◽  
Design Space ◽  
Early Stage ◽  
Pareto Frontier ◽  
Design Parameters ◽  
Safety Factors ◽  
Worst Case ◽  
Robust Convex Optimization ◽  
Early Stage Design

Abstract Engineers design for an inherently uncertain world. In the early stages of design processes, they commonly account for such uncertainty either by manually choosing a specific worst-case and multiplying uncertain parameters with safety factors or by using Monte Carlo simulations to estimate the probabilistic boundaries in which their design is feasible. The safety factors of this first practice are determined by industry and organizational standards, providing a limited account of uncertainty; the second practice is time intensive, requiring the development of separate testing infrastructure. In theory, robust optimization provides an alternative, allowing set-based conceptualizations of uncertainty to be represented during model development as optimizable design parameters. How these theoretical benefits translate to design practice has not previously been studied. In this work, we analyzed the present use of geometric programs as design models in the aerospace industry to determine the current state-of-the-art, then conducted a human-subjects experiment to investigate how various mathematical representations of uncertainty affect design space exploration. We found that robust optimization led to far more efficient explorations of possible designs with only small differences in an experimental participant’s understanding of their model. Specifically, the Pareto frontier of a typical participant using robust optimization left less performance “on the table” across various levels of risk than the very best frontiers of participants using industry-standard practices.

Multi-objective Optimization of a Regenerative Rotorcraft Powerplant: Trade-off Between Overall Engine Weight and Fuel Economy

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Fakhre Ali ◽  
Konstantinos Tzanidakis ◽  
Ioannis Goulos ◽  
Vassilios Pachidis ◽  
Roberto d'Ippolito
Keyword(s):  
Fuel Economy ◽  
Pareto Front ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Design Parameters ◽  
Optimization Strategy ◽  
Multi Objective Optimization ◽  
Trade Off ◽  
Multi Objective

A computationally efficient and cost effective simulation framework has been implemented to perform design space exploration and multi-objective optimization for a conceptual regenerative rotorcraft powerplant configuration at mission level. The proposed framework is developed by coupling a comprehensive rotorcraft mission analysis code with a design space exploration and optimization package. The overall approach is deployed to design and optimize the powerplant of a reference twin-engine light rotorcraft, modeled after the Bo105 helicopter, manufactured by Airbus Helicopters. Initially, a sensitivity analysis of the regenerative engine is carried out to quantify the relationship between the engine thermodynamic cycle design parameters, engine weight, and overall mission fuel economy. Second, through the execution of a multi-objective optimization strategy, a Pareto front surface is constructed, quantifying the optimum trade-off between the fuel economy offered by a regenerative engine and its associated weight penalty. The optimum sets of cycle design parameters obtained from the structured Pareto front suggest that the employed heat effectiveness is the key design parameter affecting the engine weight and fuel efficiency. Furthermore, through quantification of the benefits suggested by the acquired Pareto front, it is shown that the fuel economy offered by the simple cycle rotorcraft engine can be substantially improved with the implementation of regeneration technology, without degrading the payload-range capability and airworthiness (one-engine-inoperative) of the rotorcraft.

Design Space Exploration in Sparse, Mixed Continuous/Discrete Spaces via Synthetically Enhanced Classification

2018 ◽  
Author(s):  
Tyler Wiest ◽  
Carolyn Conner Seepersad ◽  
Michael Haberman
Keyword(s):  
High Performance ◽  
Design Space Exploration ◽  
Design Space ◽  
Regions Of Interest ◽  
High Performing ◽  
Bayesian Network Classifiers ◽  
Design Variables ◽  
Complex Engineering ◽  
Low Performance ◽  
Discrete Spaces

Exploration of a design space is the first step in identifying sets of high-performing solutions to complex engineering problems. For this purpose, Bayesian network classifiers (BNCs) have been shown to be effective for mapping regions of interest in the design space, even when those regions of interest exhibit complex topologies. However, identifying sets of desirable solutions can be difficult with a BNC when attempting to map a space where high-performance designs are spread sparsely among a disproportionately large number of low-performance designs, resulting in an imbalanced classifier. In this paper, a method is presented that utilizes probabilities of class membership for known training points, combined with interpolation between those points, to generate synthetic high-performance points in a design space. By adding synthetic design points into the BNC training set, a designer can rebalance an imbalanced classifier and improve classification accuracy throughout the space. For demonstration, this approach is applied to an acoustics metamaterial design problem with a sparse design space characterized by a combination of discrete and continuous design variables.

Influence of Design Parameters on the Performance of a Multistage Centrifugal Compressor for Supercritical Carbon Dioxide Applications

2015 ◽  
Author(s):  
B. Monge ◽  
D. Sánchez ◽  
M. Savill ◽  
P. Pilidis ◽  
T. Sánchez
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Centrifugal Compressor ◽  
Design Space ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Small Scale ◽  
Main Design ◽  
Supercritical Carbon

The development of the supercritical Carbon Dioxide power cycle has relied on parallel tracks along which theoretical and experimental works have successfully complemented each other in the last few years. Following this approach, intensive work on the development of critical components has enabled the demonstration of the technology in small-scale test loops. The next step in the roadmap is scaling-up the technology in order to bridge the gap to commercialisation. To this aim, not only is it necessary to demonstrate that the cycle works, but it is also mandatory to rise component (and system) efficiencies to levels comparable with competing technologies. In this process, assessing the impact of the main design parameters on the efficiency of turbomachinery is deemed crucial. The present work is a follow-up to others presented by the authors in previous years where preliminary analysis on centrifugal compressor design combining tools of different levels of fidelity were used. Nevertheless, whilst these presented guidelines to design the main compressor successfully, this new piece of research presents how the design space of the unit is affected by the characteristics of the working fluid. A review of past research is first presented to evidence that the design space is largely influenced by the particular behaviour of the working fluid close to the critical point. Then, design maps are presented for different operating conditions (cycle heat balance), showing that their shapes change substantially depending on compressor inlet pressure and temperature. Also, a comparison of these maps confirms that the design regions enabling high efficiency can be substantially reduced depending on the inlet/outlet thermodynamic states. Finally, conclusions are drawn regarding optimal intervals for the main design parameters involved in the process.

Aerodynamic Design of Transonic Tip Sections

2010 ◽  
Author(s):  
A. Stein ◽  
D. C. Hofer ◽  
V. Filippenko ◽  
J. Slepski
Keyword(s):  
Design Space ◽  
Wedge Angle ◽  
Design Parameters ◽  
Steam Turbines ◽  
Aerodynamic Design ◽  
Performance Impact ◽  
Trailing Edge ◽  
Individual Parameter ◽  
Mach Numbers ◽  
The Individual

This paper systematically explores the aerodynamic design space of transonic tip sections for large steam turbines. The sections studied in this work have subsonic inlet relative Mach numbers, and supersonic exit Mach numbers up to 1.75. Two-dimensional CFD evaluations using numerical solvers MISES and TACOMA are used to assess the performance impact of design parameters. Geometric features including subsonic overlap, supersonic overlap, trailing edge thickness, trailing edge wedge angle and camber distribution are evaluated for their effect on the section performance. An optimal geometry is then generated incorporating the best features from each of the individual parameter studies.

scholarly journals A Parametric Blade Design Method for High-Speed Axial Compressor

Aerospace ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 271
Author(s):  
Hengtao Shi
Keyword(s):  
Design Space ◽  
Flow Characteristic ◽  
Design Method ◽  
Compressor Blade ◽  
Design Parameters ◽  
Blade Design ◽  
Axial Fan ◽  
Geometry Design ◽  
Design Variables ◽  
Blade Geometry

The blade geometry design method is an important tool to design high performance axial compressors, expected to have large design space while limiting the quantity of design variables to a suitable level for usability. However, the large design space tends to increase the quantity of the design variables. To solve this problem, this paper utilizes the normalization and subsection techniques to develop a geometry design method featuring flexibility and local adjustability with limited design variables for usability. Firstly, the blade geometry parameters are defined by using the normalization technique. Then, the normalized camber angle f1(x) and thickness f2(x) functions are proposed with subsection techniques used to improve the design flexibility. The setting of adjustable coefficients acquires the local adjustability of blade geometry. Considering the usability, most of the design parameters have clear, intuitive meanings to make the method easy to use. To test this developed geometry design method, it is applied in the design of a transonic, two flow-path axial fan component for an aero engine. Numerical simulations indicate that the designed transonic axial fan system achieves good efficiency above 0.90 for the entire main-flow characteristic and above 0.865 for the bypass flow characteristic, while possessing a sufficiently stable operation range. This indicates that the developed design method has a large design space for containing the good performance compressor blade of different inflow Mach numbers, which is a useful platform for axial-flow compressor blade design.

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