Integer weighing matrices (IW-matrices for short) are integer valued orthogonal square matrices. One usecase of these is to create classical weighing matrices with various block structures. In this paper we study and classify the space IW(n,k) of the integer weighing matrices of small size n×n and weight k. Our classification includes a full list of all inequivalent matrices up to Hadamard equivalence and automorphism groups [14]. We then continue to a secondary classification of the symmetric and anti-symmetric IW up to symmetric Hadamard equivalence. We apply this to the case of projective space weighing matrices. Next we use the classification to count the cardinality of the spaces of all IW(n,k) as well as the symmetric and anti-symmetric subspace. We supply practical algorithms and implement them in Sagemath [11]. Finding an (anti-)symmetric IW-matrix in a given Hadamard class can be done for significantly higher orders. In particular we solve some open cases: Symmetric W(23,16), W(28,25) and W(30,17), and an anti-symmetric W(28,25). We conclude by showing a detailed classification of IW(7,25). We have also improved the NSOKS [30] algorithm to find all possible representations of an integer k as a sum of n integer squares.
A novel autoignition-assisted, high-temperature High-Pressure Well-Stirred Turbulent Combustor (HP-WSTC) has been developed for detailed kinetic studies of fuels under gas-turbine conditions that were difficult to obtain with conventional reactors and flame chemistry facilities. It is designed for operations at 1–20 atm, 1200–2200 K, and residence times of 1–100 ms, enabling treatment as a zero-dimensional premixed-combustion system. Methane combustion experiments at 1–10 atm were compared with 0D simulations, showing good agreement for major species across a wide equivalence-ratio range, demonstrating the reliability of the HP-WSTC. Although methane combustion kinetics are well established, NO predictions still show large discrepancies, even at atmospheric pressure. Sensitivity analyses identify CH-pool reactions, including CH2 + O2 = CH2O + O and CH + CO2 = HCO + CO, as key uncertain reactions. The developed HP-WSTC provides a new platform for fuel kinetic investigations and bridges the gap between reactor and flame facilities for high-temperature kinetic studies under gas-turbine conditions.
For steady flow past a circular cylinder, analytical solutions can be obtained describing uniform flow and a stable pair of symmetric vortices. The latter approximates the viscous vortex flow at low Reynolds number, prior to the onset of vortex shedding. Herein, we employ the analytical Föppl vortex solution to model idealised steady and unsteady heat transfer from a cylinder, and explore connections with viscous theory for this problem. We use numerical methods based on the combination of a streamline-tracing technique with operator splitting to obtain fast, accurate solutions of the convection–diffusion equation. Comparison between results from our model with those for viscous flows, based on geometric similarity criteria, show significant similarity at low Reynolds numbers, but exhibit systematic discrepancies at higher Reynolds numbers. This paper showcases important differences between viscous and inviscid heat transfer, and suggests the use of the simple Föppl vortex case as a benchmark for numerical studies.
Gas turbines are a cornerstone of modern power generation, providing reliable and dispatchable electricity across the globe. However, their significant contribution to global CO2 emissions has become increasingly untenable under international climate agreements such as the Paris Agreement. This creates a critical imperative to develop technologies that can improve the efficiency and sustainability of existing and future gas turbine fleets without compromising their operational flexibility. While the long-term vision is a fully renewable energy system, the intermittent nature of sources like wind and solar necessitates the continued use of thermal power for grid stability in the foreseeable future. Within this context, the transition to low-carbon and carbon-neutral fuels – such as hydrogen, ammonia, and methanol – has emerged as a key decarbonization pathway. However, the direct use of these fuels in conventional gas turbines is hampered by challenges related to combustion stability, flame speed, NOx formation, and, in some cases, fuel infrastructure and storage.Pre-combustion fuel reforming offers a transformative solution to these challenges. By harnessing waste heat from the turbine exhaust – or external, low-grade heat sources like solar thermal energy – to drive endothermic reforming reactions, primary fuels are converted into hydrogen-rich gas prior to combustion. This process of the use of exhaust heat to drive pre-combustion fuel reforming, known as thermochemical recuperation (TCR), achieves a dual benefit: it upgrades low-grade thermal energy into high-value chemical energy stored in the reformate, thereby enhancing the overall cycle efficiency, and it produces a fuel with superior combustion properties, including higher flame speed and wider flammability limits. Gas turbines implementing this strategy are termed Chemically Recuperated Gas Turbines (CRGTs).While CRGT upgrades fuel via waste heat recuperation – thereby increasing the share of work output from the more efficient gas turbine cycle – an alternative hybrid pathway integrates a fuel cell with a gas turbine (FC-GT), where the fuel cell converts the majority of the fuel’s chemical energy electrochemically. This fundamental difference enables FC-GT systems to achieve even higher electrical efficiencies (60%–70%). This review provides a comparative analysis between FC-GT systems and CRGT, focusing on their primary constraints.This paper presents a comprehensive and critical review of the potential of pre-combustion reforming to redefine the role of gas turbines in a low-carbon energy future. The analysis is structured around three primary fuel pathways: natural gas, where steam methane reforming offers a route to significant efficiency improvements; ammonia, where pre-combustion cracking is critical for achieving stable and efficient combustion with a carbon-free footprint; and methanol, which acts as a convenient hydrogen carrier and offers a carbon-neutral pathway when produced from renewable sources. For each fuel, the review examines the underlying thermodynamics, catalyst development, reformer design, combustion characteristics of the resulting hydrogen-rich gas, and integration into various gas turbine cycles — from simple and reheat configurations to advanced combined cycles.Furthermore, the work explores the innovative integration of concentrated solar thermal energy to drive the pre-combustion fuel reforming process, creating solar-hybrid gas turbine systems that offer a dispatchable, partially renewable power generation solution. Key technical hurdles are identified and discussed, including catalyst durability under moderate operating conditions, combustion dynamics and NOx control for hydrogen-rich fuels, materials challenges in high-temperature reformers, and the techno-economic viability of scaling such integrated solar-gas turbine systems. By synthesizing decades of research from fundamental kinetics to system-level analysis, this review aims to provide a clear roadmap for future development. It concludes that pre-combustion fuel reforming is not merely an incremental improvement but a pivotal enabling technology that can accelerate the decarbonization of the power sector by making gas turbines compatible with a sustainable, fuel-flexible, and high-efficiency future.
Cattle grazing near and inside watercourses may potentially contribute fecal coliform (FC) to surface water (streams, lakes, etc.), posing risks to both ecosystems and public health. This study presents a novel approach for estimating the impact of grazing cattle on watercourses under diverse conditions and to assess the effects of mitigation measures. The approach is based on a conceptual framework integrating field observations, long-term laboratory analysis, and FC fate and transport prediction modeling. The field survey revealed uniform distribution of dung across the plots, irrespective of distance to water. Microbial fate in the cattle dung over time under varying temperatures describes growth followed by a decline. The developed predictive process-based model showed that indirect FC load reaching the stream after dry grazing days ( 1010 CFU per cow per rain event) was approximately two orders of magnitude higher than FC load by direct in-stream deposition ( 108 CFU per cow per day). These loads were significantly reduced by creating a buffer zone of 50 m between the watercourse and grazing areas or by cattle exclusion from the watercourses for a limited time - at least during sensitive periods, i.e., when heavy rain is expected after several dry weeks and especially during the tourist period. The model results can help policy makers to quantify the effectiveness of management practices and will assist in identifying ways of revising existing measures to improve this effectiveness. The developed model can be adapted to different cases, considering the conditions prevailing on the sites. We assessed the impact of cattle grazing on watercourse microbial loads. Microbial fate and transport model was developed based on field and lab observations. Uniform dung distribution was observed irrespective of distance from watercourse. Rain after dry period is predicted to increase fecal coliform load at watercourses. The model may serve policymakers to derive effective grazing management.
