Staff publications (AA)

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Open Access
A review of hydrogen micromix combustion technologies for gas turbine applications
(Elsevier, 2025-05-13) Singh, Gaurav; Schreiner, B. Deneys J.; Sun, Xiaoxiao; Sethi, Vishal
Hydrogen micromix combustion is a promising technology for gas turbines, introducing rapid, miniaturized air-fuel mixing, significantly reducing combustion zone length and nitrogen oxides (NOx) emissions. This review evaluates the state-of-the-art hydrogen micromix combustion technologies, focusing on injector performance, flashback characteristics, and NOx reduction strategies. Injector designs are categorized based on premixing and flame stabilization techniques. While stationary gas turbines approach Technology Readiness Level (TRL) 9, aviation applications remain below TRL 4. This review identifies key design principles and predictive modelling challenges and presents a development roadmap for advancing hydrogen micromix combustion technology for aviation from TRL 4 to TRL 9 by 2040.
Open Access
An experimental investigation into fracture resistance of carbon fibre sheet moulding compound
(Elsevier, 2025-06-26) Xu, Xiaodong; Kiat Lo, Darren Kong; Adi Satriya, Ilham Akbar; Zheng, Liyi
Carbon Fibre Sheet Moulding Compound (CF-SMC) is an attractive material due to its good formability and green credentials. However, there is a lack of reliable fracture data, posing challenges when analysing CF-SMC materials which already have built-in randomness. Fracture Resistance curves (R-curves) and their variability have not been reported before for CF-SMC materials. This knowledge gap in the literature is addressed through Double Cantilever Beam (DCB) and first End Loaded Split (ELS) tests on CF-SMC. This work also explains the toughening mechanisms in CF-SMC materials during interlaminar fracture. Under Mode I, the toughening mechanism is fibre bridging while it is crack migration for Mode II. The new R-curve data provides new insights into the interlaminar fracture behaviour of CF-SMC materials and can be used as invaluable inputs for their failure analyses.
Open Access
Complex network analysis of China's integrated air-high-speed rail network: topological characteristics, centrality measures, and cluster analysis
(Elsevier, 2025-07-01) Lu, Mengyuan; Perez, Edgar Jimenez; Mason, Keith
This paper presents a comprehensive complex network analysis of China's integrated air-High-Speed Rail (HSR) network by constructing a directed weighted network and comparing its complex characteristics with its sub-networks. The findings reveal that, beyond small-world properties, the networks exhibit broad-scale characteristics with a rapid decline in degree distribution, deviating from the traditional scale-free model due to operational constraints and market saturation. Centrality analysis highlights the rising importance of secondary hubs, such as Xi'an, Kunming, and Zhengzhou, as strategic transit points linking urban centres and peripheral regions. The integrated network achieves enhanced efficiency through hybrid modularity, combining the aviation network's centralised structure with the HSR network's corridor-focused design. While this integration fosters economic connectivity and regional development, resilience challenges emerge due to reliance on high-centrality nodes. These findings offer implications for intermodal transport planning and regional development.
Open Access
Control allocation problem transformation approaches for over-actuated vectored thrust VTOLs
(Elsevier, 2025-06-01) Enenakpogbe, Emmanuel; Whidborne, James F.; Lu, Linghai
One main challenge of vectored thrust VTOLs is actuator thrust control saturation because it may lead to undesired behaviour and loss of control if the control channels are not prioritised. Another challenge of vectored thrust VTOLs is that the vectored thrust results in non-linear effector mapping preventing the direct use of standard linear control allocation approaches. Linear control allocation approaches have lower online computational and complexity burden, and have simplier requirements for fault tolerance and reconfigurability than nonlinear control allocation approaches. This paper proposes three real-time control allocation approaches for transforming a nonlinear control allocation problem to a linear problem so that classical linear control allocation approaches can then be used. The approaches which addresses the two main challenges of the particular VTOL configuration are then tested using three selected flight test manoeuvres on a generic over-actuated vectored thrust three degrees of freedom planar VTOL with no aerodynamics. The first approach transfers the non-linearity from the effector mapping to the computation of the actuator limits by formulating the real controls in cartesian form and then converts the physical actuator limits from polar to cartesian form. The second approach transforms the non-linear effector mapping to a linear mapping via numerical linearisation of the non-linear effector mapping in real-time. The third approach is similar to second approach except an extra step which transforms the virtual controls from cartesian to polar before performing an analytical linearisation resulting in a different and more complicated linear Effector mapping. The results demonstrate the effectiveness of the proposed control allocation schemes to allocate remaining control authority to higher priority and critical control channels in order to maintain operational safety and stability during certain flight conditions while there is limited control authority.
Open Access
Creating more viable safety recommendations in accident investigation by revising the human factors intervention matrix (HFIX)
(Elsevier, 2025-05-01) Chan, Wesley Tsz-Kin; Li, Wen-Chin; Yeun, Richard; Wang, Thomas
Open Access
Does cutting airport slots reduce climate impact? the case of Amsterdam airport
(Elsevier, 2025-06) Suau-Sanchez, Pere; Dobruszkes, Frédéric; Mattioli, Giulio
This study evaluates the effectiveness of airport slot reductions as a strategy for mitigating greenhouse gas (GHG) emissions, focusing on Amsterdam Schiphol Airport. Following the Dutch Government's decision to reduce slots from 500,000 to 440,000, we analyse various risk scenarios using the D'Hondt method for proportional slot allocation and the Fuel Estimation in Air Transportation (FEAT) model to estimate fuel consumption. Strategies include proportional slot cuts, prioritising short-haul flights, and shifting to rail alternatives. Results show that short-term emissions reductions are modest and do not scale with slot reductions unless long-haul flights are significantly curtailed. Moreover, aircraft up-gauging could lead to increased emissions if airline behaviour is not addressed. Our findings challenge the effectiveness of slot reductions as a climate strategy, highlighting the importance of targeting long-haul flights and adopting comprehensive policies to achieve substantial emissions reductions. The study offers critical insights for sustainable aviation policy development.
Open Access
The effects of environmental conditions on the failure of double lap composite joints with different overlap lengths and adherend thicknesses
(Elsevier, 2025-09-01) Paul, Aakash; Xu, Xiaodong; Shimizu, Takayuki; Wisnom, Michael R.
This paper provides a comprehensive study of the effects of environmental conditions on the failure of Double Lap Joints (DLJ) with composite adherends of different overlap lengths and thicknesses. The environmental conditions tested are Room Temperature Dry (RTD), Hot Temperature Dry (HTD) and Hot Temperature Wet (HTW). The mechanical properties of both the adhesive and composite adherends were characterised at these environmental conditions, showing conflicting trends. A new way of presenting the data based on simple calculations of strength or fracture dominated failure allows all the data to be shown on a single plot, and satisfactorily explains the failure modes, failure loads and opposite trends observed for a total of 13 DLJ configurations tested at the three environmental conditions.
Open Access
Experimental investigation of unsteady fan-intake interactions using time-resolved stereoscopic particle image velocimetry
(Elsevier, 2025-07) Migliorini, Matteo; Zachos, Pavlos K.; MacManus, David G.; Giannouloudis, Alexandros
Understanding engine response to unsteady intake flow distortion is a crucial requirement to de-risk the development of novel aircraft configurations. This is more critical for configurations with highly embedded engines. Recent advances in non-intrusive, laser-based flow diagnostics demonstrated the ability to measure unsteady flows in convoluted intakes with high resolution in time and space. This work presents novel non-intrusive, unsteady flow measurements ahead of a fan rotor coupled to a convoluted diffusive intake. The fan rotor caused a local increase of the maximum levels of swirl intensity at the blade tip region, as well as flow re-distribution at the interface plane between the fan and the inlet duct compared to the baseline configuration with no fan in place. This contributed to the reduction of the overall swirl angle unsteadiness across the main flow distortion frequencies. This research presents a notable advance in unsteady fan-intake interaction characterisation. The work shows that high-resolution optical measurements offer notably better understanding of these complex aerodynamic interactions and have the potential to be part of larger scale, industrial testing programmes for future product development and certification.
Open Access
On residual tensile strength after lightning strikes
(Elsevier, 2025-07-01) Xu, Xiaodong; Millen, Scott L. J.; Mitchard, Daniel; Wisnom, Michael R.
The study of post lightning strike residual strength is still relatively underdeveloped in the literature. Different approaches including in-plane compression or flexural testing have been used, but in-plane tensile loading post-strike has not been studied in detail. Although previous attempts have been made to determine the residual strength using Compression-After-Lightning (CAL) tests on composite laminates, these have been limited and not readily applicable under tensile loads. Therefore, this work completes Tension-After-Lightning (TAL) testing at 75 kA on composite laminates, a more realistic peak current than previously reported for TAL tests, to assess the knock-down in strength post-strike. The measured average TAL failure stress was 716 MPa, a reduction of 23 % from the baseline tensile failure stress of 929 MPa in the literature. This confirms a similar knock-down factor reported at lower peak currents (e.g. 50 kA), but the new TAL specimen geometry ensures that the lightning damage is contained within both the lightning and TAL specimen widths. In addition, a new Finite Element (FE) based virtual test was conducted, considering 0° ply splitting, and validated with the TAL tests herein. The TAL simulation predicted the residual tensile failure stress well, within 6 % of the measured value.
Open Access
Pilots’ training backgrounds affecting the attribution of event causal factors and airline safety management
(Elsevier, 2025-05) Chan, Wesley Tsz-Kin; Li, Wen-Chin; Braithwaite, Graham
For safety management in diverse aviation operators, it is necessary to investigate how different cultural factors interact in flight operations. Whilst prior studies have evaluated between-group cultural differences, there remains a research gap on whether within-group subcultural differences challenge the assimilation of people into the safety culture of the wider group. Cultural differences in how causal factors are perceived in the context of systemic safety deficiencies can affect the implementation of safety management strategies. In the present study, pilots from airline-sponsored, self-funded, and ex-military initial training backgrounds were invited to categorise an identical set of aircraft accident causal factors using the Human Factors Analysis and Classification System (HFACS). Results from 121 participants found significant differences amongst the three groups in the attribution of human factors conditions to organisational-level and supervisory-level categories. Significant associations amongst HFACS categories also differed amongst the three professional groups, with a considerable number of same-level associations found between ‘Preconditions for Unsafe Acts’ at the same level. Familiarity with organizational cultures was considered to impact the perception of causal factors. The finding of same-level associations presents a new contribution to the theoretical basis of the HFACS taxonomy, calling for a conceptual change in the directionality of causal sequences. The results suggest that the direction of safety remedies for different parts of the organisation is dependent on perceived relevance, which differs amongst subcultural groups. Findings are relevant to industry, particularly international airlines with diverse employee subcultural groups, for the implementation of safety management systems.

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