Hydrogen, with its unique flammability characteristics, demands additional consideration due to its broader flammable range compared to fossil fuels. Its low density at atmospheric conditions results in significant buoyancy, mitigating risks in outdoor applications. In confined spaces, hydrogen releases can lead to flammable cloud formation. To study this problem, independent of its dimensions, a dimensional analysis is introduced based on Buckingham’s Π-theorem. This work focuses on thirteen functional parameters, including mole fraction, time, release velocity, orifice diameter, reduced gravity, molecular mass diffusion, viscosity and geometric dimensions. Four dimensional scenarios are simulated and compared in this study, to assess the adequacy of the proposed non-dimensional approach. The setup involves a parallelepiped enclosure with a single release point. RANS simulations are conducted. The proposed non-dimensional formulation proves valuable for interpreting data and discussing practical applications. The study contributes to a deeper understanding of hydrogen filling regimes in confined spaces, offering insights for safety assessments and risk mitigation strategies.

Cavitation is a physical phenomenon that often occurs in hydraulic machines such as pumps, valves, and turbines. Although the Banki-Michell turbine has been used for a long time in small hydropower, no study related to this phenomenon of cavitation in the injector of this turbine has been done. In this study, we will present the results of a numerical study carried out in the nozzle of a Banki-Michell turbine. The numerical solution of the Navier Stokes cavitation equations of the Banki-Michell turbine injector was carried out considering a 2D geometry of the injector-rotor assembly. The simulation results showed that the cavitation phenomenon appears when the water flow area in the nozzle becomes less than 50%. Furthermore, the results also showed that the occurrence of this cavitation phenomenon in the injector is more likely at higher operating heads. The results of an experimental study of the geometry of the injector showed that the height of the water passage section varies linearly with the degree of opening of the stator valve.

For decades, hydropower has been the most important renewable energy source in the world. The use of Banki-Michell turbine (B-M) in small hydropower constitutes an attractive solution for rural electrification in developing countries and off-grid applications. This robust turbine is easy to design and to construct and not expensive. A test bench (JLA 29) for remote applications was installed at the Aero-Thermo-Mechanics Department of the Brussels Polytechnic School of ULB to test this type of turbine. This paper aimed to present the efficiency results of the installed Banki-Michell turbine test bench for remote applications and these results helped to design a typical turbine adapted for remote sites such as the Ryamukona site located in Burundi. Two series of B-M turbine tests were carried out, by varying the flow rate using the turbine control valve opening placed inside the distributor and also by controlling the turbine speed using a Sinamics S 120 drive. The efficiency of the turbine varies between 40 and 60% for a flow range varying between 15 and 20% of the nominal flow. According to the tests made with a discharge above 20%, the efficiency of the turbine can reach easily 75 %. Based on this turbine efficiency, a typical B-M turbine of an electric power of 79.5 kWe turbine was designed for Ryamukona site which is a remote site located in Burundi.

The objective of this work is to analyze two different solutions to the energy demand of the Tucuruí Locks.A photovoltaic power station is compared to a hybrid power generation system composed by photovoltaic and small hydraulic turbine, with pumped storage.The alternatives are discussed technically and economically: the annual energy costs of the scenarios are calculated based on the evolution of the expenses and the related energy payback time are found.The water resource is exploited responsibly, keeping balanced the volume of water in pumping and generating mode.The grid works as an intermediate storage and allows the operations with a single Pump As Turbine (PAT).The installation site is adjacent to the boat-lift structure of the Tucuruí dam.Its specific location lowers down the initial investment in favor of the hybrid system as the more viable alternative to the considered conditions.

The behavior of the fluid inside the internal circulation system of a shell and tube heat exchanger is complex due to the influence of many factors. The flow distribution has a significant influence on the performance of fluidic apparatus such as shell and tube heat exchangers. The non-uniformity of the flow distribution reduces the efficiency of the process. The influence of tubes arrangements on the flow distribution is presented using CFD simulations. In this study, four arrangement types are considered. The present results are in good agreement with those of the literature. The obtained results show that the arrangement of the tubes has a significant influence on the flow distribution. It was concluded that the flow distribution of 60 degrees arrangement exhibits better uniformity compared to the conventional arrangement (90 degrees) by 21%. The 45 degrees arrangement gives good uniformity of pressure distribution compared to the other arrangements. (C) 2017 Elsevier Ltd. All rights reserved.

Exposure to diesel exhaust was recently identified as an important cardiovascular risk factor, but whether it impairs nitric oxide (NO)–mediated endothelial function and increases production of reactive oxygen species (ROS) in endothelial cells is not known. We tested these hypotheses in a randomized, controlled, crossover study in healthy male volunteers exposed to ambient and polluted air (n=12). The effects of skin microvascular hyperemic provocative tests, including local heating and iontophoresis of acetylcholine and sodium nitroprusside, were assessed using a laser Doppler imager. Before local heating, skin was pretreated by iontophoresis of either a specific NO–synthase inhibitor (L- N -arginine-methyl-ester) or a saline solution (Control). ROS production was measured by chemiluminescence using the lucigenin technique in human umbilical vein endothelial cells preincubated with serum from 5 of the subjects. Exposure to diesel exhaust reduced acetylcholine-induced vasodilation ( P <0.01) but did not affect vasodilation with sodium nitroprusside. Moreover, the acetylcholine/sodium nitroprusside vasodilation ratio decreased from 1.51±0.1 to 1.06±0.07 ( P <0.01) and was correlated to inhaled particulate matter 2.5 ( r =−0.55; P <0.01). NO–mediated skin thermal vasodilatation decreased from 466±264% to 29±123% ( P <0.05). ROS production was increased after polluted air exposure ( P <0.01) and was correlated with the total amount of inhaled particulate matter <2.5 μm (PM2.5). In healthy subjects, acute experimental exposure to diesel exhaust impaired NO–mediated endothelial vasomotor function and promoted ROS generation in endothelial cells. Increased PM2.5 inhalation enhances microvascular dysfunction and ROS production.

A lot of research effort is spent worldwide in order to reduce the environmental impact of the transportation and power generation sector. To minimize the environmental pollution the role of hydrogen fuelled gas turbines is intensively discussed in several research scenarios, like the IGCC-technology or the application of hydrogen as large scale storage for renewable energy sources. The adaptation of the applied gas turbine combustion chamber technology and control technology is mandatory for a stable and secure low NOx operation of a hydrogen fuelled gas turbine.The micromix combustion principle was invented at Aachen University of Applied Sciences and achieves a significant reduction of the NOx-emissions by the application of multi miniaturized diffusion-type flamelets. Based on the research experiences, gained during the two European hydrogen research programs EQHHPP and Cryoplane at Aachen University of Applied Sciences, the intention of this thesis was to continue the scientific research work on low NOx hydrogen fuelled gas turbines. This included the experimental characterization of the micromix combustion principle, the design of an improved combustion chamber, based on the micromix combustion principle, for industrial gas turbine applications and the improvement of the gas turbine’s control and metering technology.The experimental characterization of the micromix combustion principle investigated the impact of several key parameters, which influence the formation of the NOx-emissions, and allows therefore the definition of boundary conditions and design laws, in which a low NOx operation of the micromix combustion principle is practicable. In addition the ability of the micromix combustion principle to operate at elevated energy densities up to 15 MW/(m2bar) was successfully demonstrated. The improved combustion chamber design concept includes the experiences gained during the experimental characterization and covers the industrial needs regarding scalability and manufacturability.The optimization and testing is done with an Auxiliary Power Unit GTCP 36-300. The original kerosene fuelled gas turbine was modified for the hydrogen application. Therefore several hardware and software modifications were realized. The improved gas turbine’s control and metering technology enables stable and comparable operational characteristics as in kerosene reference. An improved hydrogen metering unit, which is controlled by the industrial Versatile Engine Control Box, was successfully implemented. The combination of the micromix combustion technology and of the optimized control and metering technology allows a stable, secure and low NOx hydrogen fuelled gas turbine operation.

Dreyfuss, C.; Wauters, A.; Adamopoulos, D.; Moentack, C.; Hendrick, P.; Berkenboom, G.; Van De Borne, P.; Argacha, J. F. Author Information

With the final objective of optimizing the Micromix hydrogen combustion principle, a round jet in a laminar cross-flow prior to its combustion is investigated experimentally using Stereoscopic Particle Image Velocimetry. Measurements are performed at a jet to cross-stream momentum ratio of 1 and a Reynolds number, based on the jet diameter and jet velocity, of 1600. The suitability to combine side, top and end views is analyzed statistically. The statistical theory of testing hypotheses, pertaining to the joint distribution of the averaged velocity along intersecting observation planes, is employed. Overall, the averaged velocity fields of the varying observation planes feature homogeneity at a 0.05 significance level. Minor discrepancies are related to the given experimental conditions. By use of image maps, averaged and instantaneous velocity fields, an attempt is made to elucidate the flow physics and a kinematically consistent vortex model is proposed. In the time-averaged flow field, the principal vortical systems were identified and the associated mixing visualized. The jet trajectory and physical dimensions scale with the momentum ratio times the jet diameter. The jet/cross-flow mixture converging upon the span-wise centre-line, the lifting action of the Counter Rotating Vortex Pair and the reversed flow region contribute to the high entrainment and mixedness. It is shown that the jet width is larger on the downstream side as compared to the upstream side of the centre-streamline. The deepest penetration of the particles on the outer boundary occurs in the centre-plane. Meanwhile, with increasing off-centre position, the boundaries all lay further from the centre- line position than does the boundary in the centre-plane, corresponding to a kidney-like shape of the flow cross-section. The generation of the Counter Rotating Vortex Pair and the instability mechanism is documented by instantaneous image maps and vector fields. The necessary circulation for the Counter Rotating Vortex Pair originates from a combined effect of steady in-hole, hanging and wake vortices. The strong cross-flow and jet interaction induces a three-dimensional waving, the stream-wise Counter Rotating Vortex Pair pair, leading to the formation of Ring Like Vortices. A secondary Counter Rotating Vortex Pair forms on top of the primary Counter Rotating Vortex Pair, resulting in mixing by puffs. Overall, Stereoscopic Particle Image Velocimetry proofed capable of elucidating the Jet in Cross-Flow complex flow field. The gained insight in the mixing process will definitely contribute to the Micromix hydrogen combustion optimization.

With the final objective of optimizing the “Micromixing” combustion principle with means of the commercial CFD code STAR-CD, Large Eddy Simulation (LES) is used to study passive scalar transport and mixing in a round jet in a laminar cross-flow. Simulations were performed at a jet to cross-flow momentum ratio of 5.7, and a Reynolds number of 5000 based on the jet velocity and jet exit diameter. An attempt is made to provide a criterion for optimal structured meshing for Jets in Cross-flow (JICF). The performance of a structured grid based on the Taylor microscales is investigated and has been found successful. Mean and turbulent statistics are compared to data from the experiments by Su & Mungal (2004) and to Direct Numerical Simulation (DNS) performed by Muppidi & Mahesh (2006-2007). The mean scalar field from the simulation shows a very good agreement with the experimental and the DNS results. The fluctuating field terms show some differences. Given the uncertainties in the experimental configuration, overall, the agreement is quite reasonable. This study confirms the ability of the commercial CFD code STAR-CD to reproduce complex flow phenomenon. More generally, the simulation rational will form the baseline for future “Micromixing” combustion simulations.

In the scope of an industry-funded study, a test bench intended to duplicate all possible working conditions inside aircraft gas turbine engines oil lubrication systems has been designed, built, validated and even, for some functions, certified. This test bench is designed to test the externals of the gas turbine engine oil systems but mainly the lubrication pumps, mainly of the volumetric type. The development rationale of the test bench as well as the possible types of test are explained. The different aspects of the test bench are then presented, including the DAQ system and the control system. A high modularity of this test bench has been an objective from the beginning of the development. This aspect allowed in the past and will continue to allow in the future to implement new functions on the test installation. For example, recently, an extension for tests with controlled polluted oil (with sand or metallic particles) has been made possible. Some extremely successful tests have already been done in this new environment. Nomenclature

This paper reviews the status of the Belgian PowerMEMS project [1]. Focus is on the technology developments for realizing a 20 mm diameter hydrogen-based gas turbine. The total device consists of a compressor, turbine, combustion chamber, generator and recuperator. It has a total diameter of 100 mm and is 112 mm long, and has an expected electrical power output in the order of 1 kW.