Reaction Of Hydrogen Research Articles

Surface Treatment of Aluminum Oxide Using Atomic Hydrogen Generated by Catalytic Reaction on Heated Tungsten

A surface treatment using atomic hydrogen annealing (AHA) of aluminum oxide (alumina, Al2O3) has been investigated. In AHA, high-density atomic hydrogen is generated on a heated tungsten surface by catalytic cracking reaction. Sintered alumina and thermal sprayed alumina coating surfaces were subjected to AHA. The different behavior in the decrement of carbon and OH groups observed by X-ray photoelectron spectroscopy on the surface of AHA-treated sintered alumina and sprayed alumina was assumed to affect the observed different behavior in the changes of water contact angle by AHA. The difference is thought to be attributed to the different crystal structure of alumina. The chemical reactions of atomic hydrogen with carbon contamination, hydroxyl groups, and adsorbed H2O molecules were also discussed.

Improved hydroxyl radical production by electric-field-induced catalysis in O3/H2O2 process: A reactive molecular dynamics perspective

O3/H2O2 process, as a well-used ozone advanced oxidation technology, has been considered to be suitable for treating a variety of organic wastewater. However, the low solubility of ozone in hydrogen peroxide aqueous solution makes the catalytic effect to ozone reaction unsatisfactory. In this study, a novel method of external electric field (EEF) catalyzing O3/H2O2 process was proposed. The chemical reaction in O3/H2O2 process under EEF were investigated by reaction molecular dynamics simulation. The mechanism of the catalytic effect of EEF on chemical reactions in the O3/H2O2 system was revealed by analyzing the system energy, hydrogen bond energy, reaction rate and degree of reaction of the reactants, and the amount of reaction products under EEF with different strength. The results show that EEF can significantly promote the ionization reaction of H2O2 to produce more HO– 2, which further promote the reaction of O3, thus ultimately leads to the increase of •OH production and generation rate. In addition, the catalytic effect of EEF is proportional to the field strength. When the amount of ozone is constant, the concentration of hydrogen peroxide will affect the catalytic effect of EEF.

Two-dimensional alloying MNS4 (M, N = Mn, Fe, Co, Ni, Pd) materials with pentagonal pucker for highly efficient electrocatalytic hydrogen reaction

The rational design of the excellent catalytic activity electrocatalyst to replace noble metal is the core of hydrogen production from water electrolysis. Herein, we designed and demonstrated two-dimensional(2D) alloying monolayer MNS4 (M, N = Mn, Fe, Co, Ni, Pd) materials with three types of pentagonal puckers. Our results showed that the Fe- sites are better than the Co-, Ni- and Pd- sites, so the earth-abundant penta-FeS2 material is expected to be well applied in the HER catalyst. The method of alloying can improve not only the catalytic activity at the metal sites, but also the sulfur sites with abundant adsorption sites for α-type penta-MNS4 materials. Especially for the sulfur sites for α-FeCoS4 materials, there are the most excellent △GH* (0.02 eV) and outstanding exchange current density (−1.62 A/cm2) among all of the materials. We further showed that the α-type penta-MNS4 has a wide range of excellent d-band center (εd), which corresponds to the better △GH*. Ulteriorly, we demonstrated that the reaction barrier of α-FeCoS4 is reduced by the method of alloying. Our results provide theoretical guidance for designing a novel and efficient HER electrocatalyst of pentagonal transition metal dichalcogenide.

Alloying effects on inhibiting hydrogen evolution of Zn metal anode in rechargeable aqueous batteries

Alloying strategy is a feasible avenue to inhabiting the hydrogen reaction evolution (HER) of Zn anode. However, the general rule to select doping element is still unclear. In this study, the effects of Sn, Bi, Ag, and Co alloying on HER of Zn anode were investigated by experiments and DFT calculations. It is found that the doping of Sn or Bi is beneficial for inhabiting the HER compared with that of Ag or Co doping. The Gibbs free energy change (ΔG H *) and Zn atom binding energy calculations confirm that both Sn and Bi doping can inhabit the HER and dendrite formation. The Bader charge analyses indicate that Sn and Bi gain trivial electrons from neighbor Zn atoms. Bond length calculations show that the Sn and Bi will introduce local distortion into surrounding Zn atoms. The effects of alloying doping on the work functions of Zn anodes indicate that the Sn doping and Bi doping both have lower work functions than those of doping Ag and Co doping. Thus, it is proposed that the elemental doping with less charge transfer, inducing large local distortion and reducing the work function might be beneficial to inhabiting HER of Zn anode. • Doping of Sn or Bi is beneficial for inhabiting the HER of Zn anode. • Sn and Bi gain trivial electrons from neighbor Zn atoms compared with Ag and Co. • Sn and Bi doping introduce local distortion into surrounding Zn atoms. • Sn and Bi doping have lower work functions than those of Ag and Co doping.

Large eddy simulation of flame and thermal-acoustic characteristics in a strut-based scramjet with dynamic thickened flame model

Supersonic combustion is a complex phenomenon with multi-physical coupling, and the thermal-acoustic coupling under supersonic inflow is also a matter of concern. In this work, Large Eddy Simulation of a strut-stabilized model scramjet is performed with dynamic thickened flame combustion model, and an efficiency function accounting for both, wrinkling loss due to flame thickening and turbulence/flame interaction. The finite-rate chemistry model and a skeletal hydrogen reaction mechanism with 9 species and 27 reactions are adopted. The method allows to predict the complex physical in supersonic reactive flow efficiently and the results are in good agreement with experimental. A comprehensive analysis of the Damköhler number, modified flame index and heat release rate is conducted to investigate the flame structure under shock-waves condition, and the difference between heat release rate and reaction rate distributions in Mach number space is also observed. The oscillation characteristics in the strut-based scramjet is discussed mode by mode using the Proper Orthogonal Decomposition approach, and the results identify a mode at 4.997 kHz, in which the thermal-acoustic coupling found, while the stronger modes are the results of multiple factors, including auto-ignition, vortexes shedding and the resulting shock-waves oscillation.

Synthesis and characterization of molybdenum trioxide with an orthorhombic crystal structure for supercritical water gasification application

Supercritical water (SCW) catalytic gasification is promising for the production of synthetic gas from biomass. However, maintaining the activity of heterogeneous catalysts under high pressure and hydrothermal conditions is the most important. Therefore, this study investigates the activity and stability of molybdenum trioxide (MoO3) for the gasification of formaldehyde in SCW. MoO3 with an orthorhombic crystal structure was synthesized by the sol-gel method and tested in the gasification of formaldehyde in SCW. Structural and morphological changes of MoO3 with supercritical water gasification were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), N2 adsorption-desorption, thermogravimetric analysis (TGA), temperature-programmed desorption of oxygen (O2-TPD), temperature-programmed desorption with ammonia (TPD-NH3), and temperature-programmed reaction of hydrogen (H2-TPR). The XRD results show that MoO3 has an orthorhombic crystal structure. Its structure changed to a monoclinic structure upon gasification with supercritical water. SEM images showed that the rod-shaped catalyst particles transformed into thin planar plates at high pressure and temperature conditions in the presence of carbonaceous compounds. H2-TPR and XRD results showed that MoO3 was reduced to MoO2 during SCW gasification with hydrogen and carbonaceous compounds. Moreover, the oxygen stability of the catalyst changed during SCW gasification, and active oxygen species formed on the surface of the catalyst. Compared with homogeneous gasification, in the presence of the MoO3 catalyst, the fractions of CO2 and CH4 increased to 50% and 8.4%, respectively, and the fractions of H2 and CO decreased from 37.8% and 11.8% to 32.2% and 3.9%, respectively, due to the changed decomposition mechanism. Orthorhombic molybdenum oxide can be proposed as a promising catalyst for methane production.

Near-zero-waste hydrogenolysis of poly(lactic acid) to biofuel

Green recycling of poly(lactic acid) (PLA) has become the future trend for its large-scale application to cope with the “white pollution” associated. In the present study, solvent-free catalytic hydrogenolysis of PLA powder was developed with a carbon utilization of 99 % and 100 % conversion. The primary products were oxygenated liquid fuels with HHV = 29.9 MJ/kg and CO gas (∼99 %, disregard of hydrogen reactant) without the formation of any solid residues. Such hydrogenolysis process was further verified by discarded PLA straws, which possessed 95 % carbon recovery, and the derived oil held an HHV = 30.3 MJ/kg. Benefiting from the solvent-free process and near-zero-waste products, this technique provides an extraordinarily sustainable pathway for recycling PLA and its spent plastics.

Experimental investigation of hydrogen-carbonate reactions via computerized tomography: Implications for underground hydrogen storage

The underground hydrogen storage (UHS) in depleted hydrocarbon reservoirs, aquifers, and saline caverns is regarded as a vital component of hydrogen economy value-chains, meant to tackle carbon emissions and global warming. The caprock integrity and storage capacity of the carbonate formations can be altered by the reaction between the injected hydrogen and the calcite/dolomite minerals during UHS. However, experimental investigations of hydrogen-calcite/dolomite reactions at underground storage temperature are rarely reported in literature. Thus, we conducted X-ray computed micro-tomography (μCT) scans of limestone and dolomite cores before and after pressurization with hydrogen for 75 days at 700 psi and 75 °C. For the first time, a significant calcite expansion was observed and led to reduction in storage capacity (i.e., effective porosity) by 47%. However, the storage capacity of the dolomite rock slightly increased (∼6%) because the grain expansion effects canceled out the dissolution effects. The study suggests that reduction in storage capacity of carbonate formation due to hydrogen reactivity with calcite is possible during UHS in carbonate formations. Thus, hydrogen reactivity with carbonate minerals should be evaluated to de-risk hydrogen storage projects in carbonate formations.

Deflagration-to-Detonation Transition in Stochiometric Propane–Hydrogen–Air Mixtures

Hydrocarbon–hydrogen blends are often considered as perspective environmentally friendly fuels for power plants, piston engines, heating appliances, home stoves, etc. However, the addition of hydrogen to a hydrocarbon fuel poses a potential risk of accidental explosion due to the high reactivity of hydrogen. In this manuscript, the detonability of stoichiometric C3H8–H2–air mixtures is studied experimentally in terms of the run-up time and distance of deflagration to detonation transition (DDT). The hydrogen volume fraction in the mixtures varied from 0 to 1. Three different configurations of detonation tubes were used to ensure the DDT in the mixtures of the various compositions. The measured dependences of the DDT run-up time and distance on the hydrogen volume fraction were found to be nonlinear and, in some cases, nonmonotonic with local maxima. Blended fuel detonability is shown to increase sharply only at a relatively large hydrogen volume fraction (above 70%), i.e., the addition of hydrogen to propane in amounts less than 70% vol. does not affect the detonability of the blended fuel significantly. The observed nonlinear/nonmonotonic dependences are shown to be the manifestation of the physicochemical properties of hydrogen-containing mixtures. An increase in the hydrogen volume fraction is accompanied by effects leading to both an increase and a decrease in mixture sensitivity to the DDT. Thus, on the one hand, the increase in the hydrogen volume fraction increases the mixture sensitivity to DDT due to an increase in the laminar flame velocity and a decrease in the self-ignition delay at isotherms above 1000 K and pressures relevant to DDT. On the other hand, the mixture sensitivity to DDT decreases due to the increase in the speed of sound in the hydrogen-containing mixture, thus leading to a decrease in the Mach number of the lead shock wave propagating ahead of the flame, and to a corresponding increase in the self-ignition delay. Moreover, for C3H8–H2–air mixtures at isotherms below 1000 K and pressures relevant to DDT, the self-ignition delay increases with hydrogen volume fraction.

Hydrogen Fuel-cell Technology in Electric Vehicles: Current Usage, Materials and Future Applications

A conventional combustion engine results in high greenhouse gas emissions, so the world is transforming to clean energy and electric vehicles. Developments and applications of hydrogen fuel cells in electric vehicles (EVs) lead the world toward a sustainable future. Hydrogen fuel applies to fuel cells and generates electricity through electrochemical reactions. It is exceptionally clean because the by-products are water and heat, so there has no visual pollution from vehicles. HFC technology is not commonly used for now but will take place in many EVs. Some countries planned to apply it to electric power systems, railways and spacecraft fields. Currently, HFC uses platinum as the main catalyst material because of its stability, high efficiency, and good performance that boosts the hydrogen and oxygen reactions. It is the most reliable source and a perfect catalyst that is widely applied. Other catalysts such as carbon-coated nickel, nitrogen-carbon mixtures (MNCs) and transition metal nitrides (TMNs) all show good performance and have similar efficiency with Pt. These materials could replace platinum in the future because Pt has limited sources and higher costs. Also, the study has found that scientists use ruthenium graphene as a catalyst in hydrogen fuel cells. However, its effectiveness needs long-term monitoring. Although HFC is a clean technology, it has disadvantages, for example, hard for hydrogen extraction and storage, lacking refueling systems etc. Current technology limits development, and barriers exist, such as overwhelming H2 storage and delivery and some safety issues. Even so, hydrogen energy and HFC application are the future for EVs and others.

A crystal glass-nanostructured Al-based electrocatalyst for hydrogen evolution reaction.

Platinum-based catalysts are widely used in hydrogen evolution reactions; however, their applications are restricted because of the cost-efficiency trade-off. Here, we present a thermodynamics-based design strategy for synthesizing an Al73Mn7Ru20 (atomic %) metal catalyst via combinatorial magnetron co-sputtering. The new electrocatalyst is composed of ~2 nanometers of medium-entropy nanocrystals surrounded by ~2 nanometers of amorphous regions. The catalyst exhibits exceptional performance, similar to that of single-atom catalysts and better than that of nanocluster-based catalysts. We use aluminum rather than a noble metal as the principal element of the catalyst and ruthenium, which is cheaper than platinum, as the noble metal component. The design strategy provides an efficient route for the development of electrocatalysts for use in large-scale hydrogen production. Moreover, the superior hydrogen reaction evolution created by the synergistic effect of the nano-dual-phase structure is expected to guide the development of high-performance catalysts in other alloy systems.

Sensitive and Facile HCOOH Fluorescence Sensor Based on Highly Active Ir Complexes' Catalytic Transfer Hydrogen Reaction.

With several major polarity and weak optical properties, the sensitive detection of HCOOH remains a major challenge. Given the special role of HCOOH in assisting in the catalytic hydrogenation process of Ir complexes, HCOOH (as a hydrogen source) could rapidly activate Ir complexes as catalysts and further reduce the substrates. This work developed a facile and sensitive HCOOH fluorescence sensor utilizing an optimal catalytic fluorescence generation system, which consists of the phenyl-pyrazole-type Ir-complex PP-Ir-Cl and the coumarin-type fluorescence probe P-coumarin. The sensor demonstrates excellent sensitivity and specificity for HCOOH and formates; the limits of detection for HCOOH, HCOONa, and HCOOEt3N were tested to be 50.6 ppb, 68.0 ppb, and 146.0 ppb, respectively. Compared to previous methods, the proposed sensor exhibits good detection accuracy and excellent sensitivity. Therefore, the proposed HCOOH sensor could be used as a new detection method for HCOOH and could provide a new design path for other sensors.

Modeling of the Electrostatic Interaction and Catalytic Activity of [NiFe] Hydrogenases on a Planar Electrode.

Hydrogenases are a group of enzymes that have caught the interest of researchers in renewable energies, due to their ability to catalyze the redox reaction of hydrogen. The exploitation of hydrogenases in electrochemical devices requires their immobilization on the surface of suitable electrodes, such as graphite. The orientation of the enzyme on the electrode is important to ensure a good flux of electrons to the catalytic center, through an array of iron-sulfur clusters. Here we present a computational approach to determine the possible orientations of a [NiFe] hydrogenase (PDB 1e3d) on a planar electrode, as a function of pH, salinity, and electrode potential. The calculations are based on the solution of the linearized Poisson-Boltzmann equation, using the PyGBe software. The results reveal that electrostatic interactions do not truly immobilize the enzyme on the surface of the electrode, but there is instead a dynamic equilibrium between different orientations. Nonetheless, after averaging over all thermally accessible orientations, we find significant differences related to the solution's salinity and pH, while the effect of the electrode potential is relatively weak. We also combine models for the protein adsoption-desorption equilibria and for the electron transfer between the proteins and the electrode to arrive at a prediction of the electrode's activity as a function of the enzyme concentration.

Experimental investigation of hydrogen enriched natural gas diffusion reactions using preheated air in a hot coflow burner

The present paper analyzes experimentally the morphology of a set of non-premixed diffusion reactions of hydrogen enriched natural gas (NG). For the analysis the H2 content was varied from 0 to 100 vol.-% and the mixture issues in a co-flow at variable preheating temperatures, from ambient conditions of 25 °C and up to 400 °C. For the various NG-H2 blends the thermal power input was held constant at 0.8 kW. For processing the images, a bitmap filter was used to isolate visible flame height, visible width variations, and soot free length fraction (SFLF). The results show that visible flame height always decreases when increasing H2 content in NG at any preheating temperature. The effects of air preheating summarize as follows: for NG enriched up to 75 vol.-% H2, the visible flame height reduces when increasing the air preheating temperature from 25 °C to 200 °C, then at 300 °C the visible flame height increases when rising the air temperature up to 400 °C. For the 100% H2 non-premixed flame the visible height presents a linear trend to increase as air temperature rises. Roper's theory for non-premixed flames in circular ports correlates reaction length to air preheating temperature and fuel composition variations, however those trends neglect buoyancy and diffusion phenomena, which results in significant error on predicting the effects of hydrogen addition to NG on the reaction length. A modified correlation is proposed to predict accurately the effects of air preheating and H2 fraction on visible flame height. Finally, a multidimensional scaling analysis shows that hydrogen addition up to 50 vol.-% does not modifies the visible flame morphology significantly when compared to pure NG.

Role of Surface Reactions in Hydrogen–Oxygen Explosion Limits

Role of Surface Reactions in Hydrogen–Oxygen Explosion Limits

Wet Gas Water Feed of Polymer Electrolyte Membrane Electrolyzer for Simultaneous Hydrogenation of Organic Chemical Hydride Energy Carrier and Water Decomposition

To utilize renewable electricity with fluctuation and localization, large-scale energy storage and transportation technologies using hydrogen energy carrier have been expected. In order to improve hydrogen energy carrier synthesis, we have studied one-step electrolysis for toluene electrohydrogenation and water decomposition using proton exchange membrane (PEM) electrolysis. This process has 1.09 V of theoretical decomposition voltage for simultaneous water electrolysis and toluene hydrogenation.As shown in Figure 1, anode reaction produces oxygen and proton, and proton transports cathode electrocatalyst layer through the PEM with water molecular. Water inhibits toluene transportation to reaction side and hydrogen evolution occurs as side reaction. We have reported electrolyzers that has cathode side of PEFC’s MEA like structure using PtRu/C and anode side of industrial electrolyzer like structure using mesh shape of DSE® electrode for oxygen evolution reaction, and sulfuric acid solution feeds as anolyte that is not only reactant but also for water management. Water back diffusion from cathode to anode enhances with sulfuric acid concentration. In addition, current efficiency with mesh type anode was higher than that with sintered fiber sheet type anode. The mesh shape of electrode makes current distribution that affects mass transfer pass distribution to improve current efficiency, although sheet type anode is lower overpotential because of large surface area [1 – 3]. As practical system, water transportation from anode to cathode should be supressed without sulfuric acid utilization, and electrochemical surface- area of anode should extend to reduce overpotential.In this study, we have investigated wet gas water feed for PEM electrolysis to reduce water transfer to cathode, because water transfer would control by relative humidity of wet gas that feed to anode for oxygen evolution reaction. Here, PEM water electrolysis type anode catalyst layer with ionomer was employed to reduce anode overpotential and to maintain ionic conduction in catalyst layer.Figure 1 shows the schematic drawing of toluene direct hydrogenation electrolyzers with water splitting. Figure 1 (a) is our conventional electrolyzer of H2SO4 solution feed, and Figure 1 (b) is wet air feed in this study. The anode side for wet air feed had polymer electrolyte fuel cell type serpentine gas flow channel. Anode catalyst layer was 1.0 mg cm-2 of IrOx (TKK) with Nafion ionomer. The porous transport layer was platinum plated sintered titanium sheet. PEM was Nafion 117 (Du Point), cathode catalyst layer was 0.5 mg cm-2 of PtRu/C with Nafion ionomer supported on a porous flow field of a carbon paper that was loaded 0.02 mg cm-2 platinum for chemical reaction of toluene and hydrogen.5 mL min-1 of toluene or 10% toluene – methylcyclohexane and 1.0 L min-1 of wet air fed to cathode and anode, respectively. Operation temperature was 80oC. After the 100 % RH feed electrolysis, there is no product except methylcyclohexane in the liquid phase and water transportation from anode to cathode reduced one twentieth from the conventional electrolyzer fed 1 M H2SO4 operation at 60oC. In this condition, IR free cell voltage of the wet gas fed electrolyzer was significantly smaller than that of the conventional one because of high surface area anode. Internal resistance of the wet gas feed determined by AC impedance method was about two times higher than that of the conventional, and current efficiency maintained in the low current density region. The internal resistance increased in the high current density region where the membrane and ionomer dry up with electro osmosis water. In this region, current efficiency also decreases.In summary, wet gas feed water electrolysis for electrohydrogenation of toluene using a PEM electrolyzer is an interesting technology that combines water electrolyzer with water purification system and manages water feed to reduce water transportation to cathode to maintain current efficiency of with accurate control of relative humidity and gas feed amount.AcknowledgementThis study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (P14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).References Nagasawa, K. Tanimoto, J. Koike, K. Ikegami, S. Mitsushima, J Power Sources, 439, 227070 (2019).Oi, K. Nagasawa, T. Takamura, Y. Misu, K. Matsuoka, S. Mitsushima, ECS Meeting s, MA2021-02, 1737 (2021).Mitsushima, Y. Sugita, J. Koike, Y. Kuroda, K. Matsuoka, Y. Sato, K. Nagasawa, ECS Meeting s, MA2020-02, 2494 (2020). Figure 1

Quantitative real-time in situ measurement of gaseous K, KOH and KCl in a 140 kW entrained-flow biomass gasifier

Photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) was used to simultaneously measure the concentrations of gas phase atomic potassium (K), potassium hydroxide (KOH) and potassium chloride (KCl) in the reactor core of a 140 kWth atmospheric entrained-flow gasifier (EFG). In two gasification experiments at air-to-fuel equivalence ratio of 0.5, the EFG was first run on forest residues (FR) and then on an 80/20 mixture of FR and wheat straw (FR/WS). Combustion at air-to-fuel equivalence ratio of 1.3 was investigated for comparison. A high K(g) absorbance was observed in gasification, requiring the photofragmentation signals from KOH(g) and KCl(g) to be recorded at a fixed detuning of 7.3 cm−1 from the center of the K(g) absorption profile. In combustion, the fragments recombined instantly after the UV pulse within around 10 µs, whereas in gasification, the K(g) fragment concentration first increased further for 30 µs after the UV pulse, before slowly decaying for up to hundreds of µs. According to 0D reaction kinetics simulations, this could be explained by a difference in recombination kinetics, which is dominated by oxygen reactions in combustion and by hydrogen reactions in gasification. The K species concentrations in the EFG were stable on average, but periodic short-term variations due to fuel feeding were observed, as well as a gradual increase in KOH(g) over the day as the reactor approached global equilibrium. A comparison of the average K species concentrations towards the end of each experiment showed a higher total K in the gas phase for FR/WS, with higher K(g) and KCl(g), but lower KOH(g), compared to the FR fuel. The measured values were in reasonable agreement with predictions by thermodynamic equilibrium calculations.

An electro-chemo-mechanical framework for predicting hydrogen uptake in metals due to aqueous electrolytes

We present a theoretical and numerical scheme that enables quantifying hydrogen ingress in metals for arbitrary environments and defect geometries. This is achieved by explicitly resolving the electrochemical behaviour of the electrolyte, the hydrogen and corrosion reactions, the kinetics of surface adsorption, and hydrogen uptake, diffusion and trapping in mechanically-deforming solids. This new framework is used to produce maps that relate the absorbed hydrogen with the applied potential, specimen geometry and fluid velocity. We also present simplified versions of our generalised model, and benchmark predictions of these and other existing models against the generalised electro-chemo-mechanical results, establishing regimes of validity.

Thermodynamic Assessment of Exhaust Gas Recirculation in High-Volume Hydrogen Gas Turbines in Combined Cycle Mode

Abstract To reach net-zero while ensuring grid reliability and resiliency, gas turbine (GT) technology has a place for years to come. However, shifting to low-carbon fuels, such as hydrogen, is the key to maintain positive returns in combined cycle (CC) power plants. By recirculating a fraction of the exhaust gas exiting the heat recovery steam generator (HRSG) back to the inlet of a natural gas (NG) and hydrogen cofired GT, the gas flow passing through the compressor and entering the combustor has a reduced oxygen concentration thus lowering flame temperature, hence NOx formation. Hydrogen reactivity is then turned into a benefit since the exhaust gas recirculation (EGR) rate can be higher than that with NG, without facing flame stability issues. In light of this, a thermodynamic assessment of EGR effects on a 2 × 1 large-scale CC is presented considering GT with hydrogen capability up to 65%. The impact of partially replacing NG with hydrogen on GT behavior and overall CC performance was first evaluated at both full and part load, with no EGR. Then EGR was simulated for a rate up to 0.5 for different fuel mixtures, under the assumptions of GT inlet flow at low (ISO) and high (up to 47 °C) temperature. The analysis was again carried out at full and part load. In the latter case, EGR was exploited to improve CC efficiency at very low loads. For each scenario, CO2 emission intensity was computed thus highlighting the environmental benefits of hydrogen-NG blends.

Accelerating turbulent reacting flow simulations on many-core/GPUs using matrix-based kinetics

The present work assesses the impact - in terms of time to solution, throughput analysis, and hardware scalability - of transferring computationally intensive tasks, found in compressible reacting flow solvers, to the GPU. Attention is focused on outlining the workflow and data transfer penalties associated with “plugging in” a recently developed GPU-based chemistry library into (a) a purely CPU-based solver and (b) a GPU-based solver, where, except for the chemistry, all other variables are computed on the GPU. This comparison allows quantification of host-to-device (and vice versa) data transfer penalties on the overall solver speedup as a function of mesh and reaction mechanism size. To this end, a recently developed GPU-based chemistry library known as UMChemGPU is employed to treat the kinetics in the flow solver KARFS. UMChemGPU replaces conventional CPU-based Cantera routines using a matrix-based formulation. The impact of i) data transfer times, ii) chemistry acceleration, and iii) the hardware architecture is studied in detail in the context of GPU saturation limits. Hydrogen and dimethyl ether (DME) reaction mechanisms are used to assess the impact of the number of species/reactions on overall/chemistry-only speedup. It was found that offloading the source term computation to UMChemGPU results in up to 7X reduction in overall time to solution and four orders of magnitude faster source term computation compared to conventional CPU-based methods. Furthermore, the metrics for achieving maximum performance gain using GPU chemistry with an MPI + CUDA solver are explained using the Roofline model. Integrating the UMChemGPU with an MPI + OpenMP solver does not improve the overall performance due to the associated data copy time between the device (GPU) and host (CPU) memory spaces. The performance portability was demonstrated using three different GPU architectures, and the findings are expected to translate to a wide variety of high-performance codes in the combustion community.