Shahrokh Shahpar

Rolls-Royce · Innovation Hub - Future Methods

The tip clearance size has historically been considered to be the main factor affecting stability range in axial fan and compressors. This paper reveals that the stall characteristics are defined by the axial momentum flux of the tip leakage flow and that tip clearance is primarily a strong driver for this metric. A bespoke methodology for carefull...

In_service deterioration can lead to undesired shape variations on high-pressure turbine rotor blades. This can have a significant impact on efficiency, power generation and component life. Loss of power production from the high_pressure turbine rotor causes engine over_throttling to compensate for the lower performance. This will in turn worsen th...

The urgent need for greener aviation has greatly increased the viability of electric/hybrid-electric aircraft propulsion systems. As a result, there is a need to increase the capability to rapidly design and analyse a range of new systems, about which there is limited established knowledge. An optimisation framework linking Modelica models to a Pyt...

In-service deterioration can lead to undesired shape variations on high-pressure turbine rotor blades. This can have a significant impact on efficiency, power generation and component life. Loss of power production from the high-pressure turbine rotor causes engine over-throttling to compensate for the lower performance. This will in turn worsen th...

The term uncertainty quantification (UQ) refers to a set of techniques which are used to measure the statistical variability of several input parameters. In recent years, UQ has become increasingly relevant due to its applications in robust design and optimization (RDO). The present work focuses on the RDO of aero engine components. 200 in-serviced...

This work shows the application of fluid Topology Optimization for the thermal management of electric parts in aircraft engines. There is a growing trend in electrification of current engines, but this requires higher power to be dissipated. Standard coolant systems based on serpentines are not effective enough to remove the heat produced by these...

The tip clearance size has historically been considered to be the main factor affecting stability range in axial fan and compressor. This paper reveals that the stall characteristics are defined by the axial momentum flux of the tip leakage flow and that tip clearance is primarily a strong driver for this metric. A bespoke methodology for carefully...

This work presents a novel methodology for performing design analysis and optimisation on scenarios involving computationally expensive numerical simulations and high-dimensional design spaces, often encountered in industry. The capabilities and applicability of the method are demonstrated through two application test cases in the field of gas turb...

This work presents the aerodynamic topology optimisation of high pressure turbine rotor blade tips. Before carrying out the topology optimisation on the blade tip, some initial tip design studies were carried out. A winglet tip was optimised first and it was found that the optimum winglet design features a combination of small and largest overhangs...

Multidisciplinary design optimisation of transonic rotors, especially focusing on improving the aeroacoustic performance, has received little attention. This paper employs an automatic design optimisation approach to reduce the shock-associated tone noise and to increase the adiabatic efficiency of NASA rotor 37. An evolutionary algorithm for multi...

Hexahedral meshing of complex domains is a long-standing problem in engineering simulation. One strategy to achieve it is through multi-block decomposition. Recent efforts have focussed on deriving the block topology using frame-fields which aim to capture the desired mesh orientation throughout the domain. This reduces to determining the approxima...

The open source computational fluid dynamics (CFD) software OpenFOAM is used to investigate the flow through the Wellborn s-duct. Numerical simulations with two different modelling techniques are performed. Transient simulations with Unsteady Reynolds Averaged Navier Stokes (URANS) and Detached Delayed Eddy Simulation (DDES) formulations are compar...

Gear pumps are largely employed in aero-engine fuel systems to provide the combustor with fuel at adequate pressure and flow rate. The radial load applied on the gears, as a consequence of the pump pressure rise, is entirely supported by the hybrid journal bearings. Lubrication of these is accomplished using low viscosity aviation fuel, which makes...

The increased need to design higher performing aerodynamic shapes has led to design optimisation cycles requiring high-fidelity CFD models and high-dimensional parametrisation schemes. The computational cost of employing global search algorithms on such scenarios has typically been prohibitive for most academic and industrial environments. In this...

View Video Presentation: https://doi.org/10.2514/6.2021-3073.vid Regression-based Polynomial Chaos expansions offer several advantages over projection-based approaches, including their lower computation cost and greater flexibility. In the presence of expensive function evaluations, such as with computational fluid dynamics and finite element analy...

View Video Presentation: https://doi.org/10.2514/6.2021-3055.vid The target of reducing the environmental footprint of the aviation industry has continually driven the need to design more efficient and quieter aircraft engines. In this paper, the aeroacoustic adjoint formulization for low-shock tone noise fan blade design is first proposed and comb...

View Video Presentation: https://doi.org/10.2514/6.2021-3071.vid This work deals with aerodynamic and aerothermal optimisations of high pressure turbine blade tips where a winglet turbine tip is optimised in terms of aerodynamic efficiency and integrated heat transfer coefficient. Two constraints were introduced in the optimisation process. In part...

The target of reducing the environmental footprint of the aviation industry has continually driven the need to design more efficient and quieter aircraft engines. In this paper, the aeroacoustic adjoint formulization for low-shock tone noise fan blade design is first proposed and combined with the aerodynamic adjoint analysis to develop an adjoint-...

One of the major noise sources of high bypass ratios modern turbofan engines arises from the interaction between the turbulent rotor wake, the tip-leakage and the leading edge of the downstream outlet guide vanes. Recent research has confirmed that leading edge serrations are an effective passive control for reducing noise. However, for transferrin...

Adjoint aerodynamic optimisation has recently gained increased popularity for turbomachinery applications due to the large number of parameters that can be used without incurring additional major computational costs. This work presents an adjoint based aero-structural optimisation method having efficiency as the objective function and maximum von M...

Machine learning models are becoming an increasingly popular way to exploit data from fluid dynamics simulations. This project investigates how autoencoders and output consolidation can be used to increase the accuracy of machine learning models, by injecting knowledge of the full flow field in the predictions of Quantities of Interest (QoI) used i...

The increased need to design higher performing aerodynamic shapes has led to design optimisation cycles requiring high-fidelity CFD models and high-dimensional parametrisation schemes. The computational cost of employing global search algorithms on such scenarios has typically been prohibitive for most academic and industrial environments. In this...

Leading edge instrumentation used in compressor and turbine blades for jet-engine test rigs can cause significant obstruction and lead to a marked increase in downstream pressure loss. Typical instrumentation used in such a scenario could be a Kiel shrouded probe with either a thermocouple or pitot-static tube for temperature/pressure measurement....

Computational Fluid Dynamics (CFD) discretisation errors are generally present in any simulation result, with the main issues lying in the mesh generation stage. Despite this, CFDsoftware has widespread use in the industrial design procedure. To improve modelling reliability, mesh adaptation proposes to automatically modify grids to better their ac...

With the advancement in electric propulsion systems, aircraft designers and manufacturers are no longer constrained to established configurations. Developments in Vertical Take-off and Landing (VTOL) aircraft have been seen in recent times through the design of modern tiltrotor aircraft, tiltwing concepts and multi-rotor designs. The combination of...

Shock control bumps can be used to control and weaken the shock waves that form on engine intakes at high angles of attack. In this paper, it is demonstrated how shock control bumps applied to an engine intake can reduce or eliminate shock-induced separation at high incidence , and also increase the incidence at which critical separation occurs. Th...

The power of adjoint optimisation is that the computational cost of the optimisation is almost independent of the number of design parameters. Thus, hundreds or even thousands of parameters can be used with relatively little increase in cost. But how much benefit does this provide, and is it always beneficial to increase the number of parameters? T...

The benefit of mesh adaptation to improve the optimisation process of turbomachinery components is here demonstrated. Mesh movement is used to automatically cluster and align the cells with significant flow features such as shocks, shock-induced separation and wakes for every geometry tested during a transonic compressor blade optimisation. Using m...

The measurement of stagnation temperature is important for turbomachinery applications as it is used in the calculation of component efficiency and engine specific fuel consumption. This paper examines the use of polynomial variable projection to identify dimension reducing subspaces for stagnation temperature probes. As an example application we f...

To improve the quality of a manufactured part in industry, a variety of techniques are used to scan a built geometry to bring it back to the physics based simulation world to assess its true performance. There are various laser and structured light measurement techniques (GOM), Computed Tomography (CT) scan as well as touch-point probes in the form...

Leading edge instrumentation used in compressor and turbine blades for jet-engine test rigs can cause significant obstruction and lead to a marked increase in downstream pressure loss. Typical instrumentation used in such a scenario could be a Kiel-shrouded probe with either a thermocouple or pitot-static tube for temperature/pressure measurement....

This work presents the aerodynamic topology optimisation of high pressure turbine rotor blade tips. Before carrying out the topology optimisation on the blade tip, some initial tip design studies were carried out. The winglet shape was optimised using two different design space setups and parameter limits. The optimum winglet design features the la...

Achieving an optimal level of flow swirl is required for efficient mixing of air and fuel in order to realise lean combustion. A novel method is devised to achieve a necessary level of swirl, using NACA airfoil profiles as the baseline for swirl stator blades. Formulas for achieving a required level of swirl have been derived and implemented in a c...

Reducing emissions and improving fuel economy has become a key target for advanced aircraft engine platforms. The competitive aviation market requires a drastic reduction in current aircraft emission levels, which leads to the requirement of optimising the entire combustion process. Lean burn pre-mixed systems are an efficient way of reducing NOx e...

A Multi-point Approximation Method (MAM) coupled with adjoint is presented to increase the efficiency of a modern jet-engine fan blade. The study performed makes use of Rolls-Royce in-house suite of codes and its discrete adjoint capability. The adjoint gradient is used along with MAM to create a Design Of Experiment to enhance the optimization pro...

Motivated by the idea of turbomachinery active subspace performance maps, this paper studies dimension reduction in turbomachinery 3D CFD simulations. First, we show that these subspaces exist across different blades—under the same parametrisation—largely independent of their Mach number or Reynolds number. This is demonstrated via a numerical stud...

Summar Nowadays, aerodynamic computational modelling is carried out on a daily basis in an industrial setting. This is done with the aim of predicting the performance and flow characteristics of new components. However, limited resources in terms of time and hardware force the engineer to employ relatively coarse computational grids, thus achieving...

With the advancement in electric battery design, aircraft designers and manufacturers are no longer constrained to established configurations. Developments in Vertical Take-off and Landing (VTOL) aircraft have also been seen in recent times through the design of modern tiltrotor aircraft such as the AW609 and the V-280 Valor. The combination of the...

A nacelle defining an intake is provided for channelling and conditioning freestream airflow to a fan of a ducted fan gas turbine engine. The nacelle intake comprises in flow series an intake lip, and a diffuser. The intake lip has at its forwardmost end a highlight which is a closed loop defining a boundary between inner and outer surfaces of the...

In this work, a novel method for creating decompositions of general 3D domains, suitable for hexahedral mesh generation is presented. To accomplish this, frames and cross-fields are generated on top of the medial object of the domain. The geometrical and topological information carried by the medial object, together with the directional information...

Inevitable uncertainties and their potential negative impact on performance are a widely known problem in the field of turbomachinery. Based on a representative sample of optically scanned film cooled turbine blades, the impact of real manufacturing variations is investigated. Geometric models with realistic blade shape and film cooling hole variat...

This work focuses on the use of evolutionary algorithm to perform automatic blocking of a 2D manifold. The goal of such a blocking process is to completely partition a 2D region into a set of conforming and non-intersecting quadrilaterals to facilitate the generation of an all-quadrilateral, or more preferably an ideal quadrilateral mesh configurat...

Moving towards a zero emission world, hybrid electric aircraft are becoming an increasingly popular research topic to improve urban mobility. Most of the concepts being developed, however, require technological leaps that can delay the introduction of such ideas to the commuters market. In this context, optimisation applied in early design stages i...

The present patent relates to shroudless turbine blades having squealer tips. More particularly the invention relates to the arrangement of internal cooling channels in this region of the blade and the geometry of squealer tips which accommodate the cooling channels. • In some embodiments, the gutter in the region of the trailing edge is inclined f...

Preprocessing remains one the main bottlenecks in the computational fluid Dynamics simulations of flows involving complex geometries as advances in the algorithm development, turbulence modelling and parallel computing are made. To this end, two approaches are presented here to efficiently deal with complex geometries in order to reduce the preproc...

Shock control bumps can help to delay and weaken shocks, reducing loss generation and shock-induced separation and delaying stall inception for transonic turbomachinery components. The use of shock control bumps on turbomachinery blades is investigated here for the first time using 3D analysis. The aerodynamic optimisation of a modern research fan...

In this work, a novel method for calculating mesh singularity lines (chains of irregular edges in an otherwise structured hex mesh) in a 3D computational domain is presented. It explores how combining the medial object of a domain with frames can provide insights to the placement of singularity lines. The medial object's vertices, edges and surface...

This article introduces an implementation of mesh morphing using radial basis functions (RBF) in a proprietary meshing framework ABIHex. RBF Morphing is a meshless method for mesh morphing that derives its origin from optimisation and machine learning. The method is used to perturb an arbitrarily complex mesh given a sample of displacements at know...

This work focuses on the use of evolutionary algorithm to perform automatic blocking of a 2D manifold. The goal of such a blocking process is to completely partition a 2D region into a set of conforming and non intersecting quadrilaterals to facilitate the generation of an all-quadrilateral, or more preferably an ideal quadrilateral mesh configurat...

The measurement accuracy of the temperature/pressure probe mounted at the leading edge of a turbine/compressor blade is crucial for estimating the fuel consumption of a turbo-fan engine. Apart from the measurement error itself, the probe also introduces extra losses. This again would compromise the measurement accuracy of the overall engine efficie...

The turbine tip geometry can significantly alter the performance of the turbine stage; its design represents a challenge for a variety of reasons. Multiple disciplines are involved in its design and their requirements limit the creativity of the designer. Multi-Disciplinary Design Optimisation (MDO) offers the capability to improve the performance...

This paper is a review of significant studies in the complex flow physics in diffusive, s-shaped ducts, focusing on flow control methods employed to counteract the onset of separation, swirl formation, and non-uniformity of pressure at the duct exit plane. Passive, active, and hybrid flow control, along with optimisation techniques used to control...

Motivated by the idea of turbomachinery active subspace performance maps, this paper studies dimension reduction in turbomachinery 3D CFD simulations. First, we show that these subspaces exist across different blades-under the same parametrization-largely independent of their Mach number or Reynolds number. This is demonstrated via a numerical stud...

Within an industrial setting, mesh adaptation has so far found very limited use. This is, in part, due to the complexity of the geometries and flow features that are to be dealt with. However, the successful utilisation of grid modification techniques, could help engineers achieve more accurate estimates of quantities of interest quickly and effici...

Shock control bumps can help to delay and weaken shocks, reducing loss generation and shock-induced separation and delaying stall inception for transonic turbomachinery components. The use of shock control bumps on turbomachinery blades is investigated here for the first time using 3D analysis. The aerodynamic optimisation of a modem research fan b...

The measurement accuracy of the temperature/pressure probe mounted at the leading edge of a turbine/compressor blade is crucial for estimating the fuel consumption of a turbo-fan engine. Apart from the measurement error itself, the probe also introduces extra losses. This again would compromise the measurement accuracy of the overall engine efficie...

Shock control bumps can help to delay and weaken shocks, reducing loss generation and shock-induced separation and delaying stall inception for transonic turbomachinery components. The use of shock control bumps on turbomachinery blades is investigated here for the first time using 3D analysis. The aerodynamic optimisation of a modern research fan...

A computer-implemented method of optimizing an automatically meshable shape is provided. The method includes the steps of: providing a continuous boundary of the automatically meshable shape, the continuous boundary being defined by a spline formed by two or more spline segments, wherein each segment has a terminal point at each end of the segment;...

Uncertainty Quantification is an increasingly important area of research. As components and systems become more efficient and optimized, the impact of uncertain parameters. It is fundamental to consider the impact of these uncertainties as early as possible during the design process, with the aim of producing more robust designs (less sensitive to...

Turbomachinery active subspace performance maps are two-dimensional (2D) contour plots that illustrate the variation of key flow performance metrics with different blade designs. While such maps are easy to construct for design parameterizations with two variables, in this paper, maps will be generated for a fan blade with twenty-five design variab...

During engine operation, fan casing abradable liners are worn by the blade tip, resulting in the formation of trenches. This paper describes the influence of these trenches on the fan blade tip aerodynamics. A detailed understanding of the fan tip flow features for cropped and trenched clearances is first developed. A parametric model is then used...

This work proposes a simple and fast approach for re-meshing the surfaces of smooth-featured geometries prior to CFD analysis. The aim is to improve mesh quality and thus the convergence and accuracy of the CFD analysis. The method is based on constructing an interpolant based on the geometry shape and then mapping a regular rectangular grid to the...

Non-intrusive Polynomial Chaos (NIPC) methods have become popular for uncertainty quantification, as they have the potential to achieve a significant reduction in computational cost (number of evaluations) with respect to traditional techniques such as the Monte Carlo approach, while allowing the model to be still treated as a black box. This work...

Uncertainty Quantification (UQ) is an increasingly important area of research. As components and systems become more efficient and optimized, the impact of uncertain parameters (such as boundary and operating conditions, geometrical variations due to manufacturing or in-service deterioration, etc.) is likely to become critical. It is therefore fund...

Turbomachinery active subspace performance maps are 2D contour plots that illustrate the variation of key flow performance metrics with different blade designs. While such maps are easy to construct for design parameterizations with two variables, in this paper maps will be generated for a fan blade with twenty- five design variables. Turbomachiner...

In engineering design, uncertainty is inevitable and can cause a significant deviation in the performance of a system. Uncertainty in input parameters can be categorized into two groups: aleatory and epistemic uncertainty. The work presented here is focused on aleatory uncertainty, which can cause natural, unpredictable and uncontrollable variation...

During engine operation fan casing abradable liners are worn by the blade tip, resulting in the formation of trenches. This paper investigates the influence of these trenches on the fan blade tip aerodynamics. A detailed understanding of the tip flow features for the fan blade under investigation is developed. A parametric model is then used to mod...

An improvement in overall efficiency and power output for gas turbine engines can be obtained by increasing the combustor exit temperature, but the thermal management of metal parts exposed to hot gases is challenging. Discrete film cooling, combined with internal convective cooling is the current state-of-the-art available to aerothermal designers...

An assessment of various automatic block topology generation techniques for creating structured meshes has been performed in the first part of the paper. The objective is to find out optimal blocking methods for generating meshes suitable for flow simulations. The comparison has been carried out using an adjoint-based error analysis of the meshes g...

An assessment of various automatic block topology generation techniques for creating structured meshes has been performed in the first part of the paper. The objective is to find out optimal blocking methods for generating meshes suitable for flow simulations. The comparison has been carried out using an adjoint based error analysis of the meshes g...

Tip leakage flow has a significant impact on fan blade performance. It is therefore critical to understand the effect of both the uniform and non-uniform tip clearance variations that occur in engines. Firstly, a detailed understanding of the flow physics present in the tip region of a modern axial flow fan blade is developed using RANS CFD. Analys...

Compressors of gas turbine engines are multi-disciplinary systems whereas the different disciplines are largely considered separately. In order to produce feasible designs, the components need to be re-designed several times which is time consuming. A multi-disciplinary design process enabling an integrated approach for all discipline is described...

This paper describes the use of the Free-Form-Deformation parameterisation method to create a novel blade shape for a highly loaded, transonic axial compressor. The novel geometry makes use of pre-compression (via an S-shaping of the blade around mid-span) to weaken the shock and improve the aerodynamic performance. It has been known for some time...

Rare event simulation is vital for industrial design because some events, so-called black swans, can have fatal consequences despite their low probability of occurrence. Finding low-probability events far off the mean design is a challenging task for realistic engineering models because they are characterized by high computational demands, many inp...

A computational engineering modelling tool having a point generation module arranged to read geometry data representing a domain to be modelled. The point generation module also generates point data for the domain having multiple boundary points located on a boundary of the domain and multiple further points spaced from the boundary within the doma...