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Stephen McClelland looks at an intriguing — but contentious development in the normally sedate world of hydrogen sensors.

U.S.S.R. Effect of pH value on iron corrosion. The solubility of iron in media of sufficiently high acidity proceeds mainly through hydrogen depolarisation and without formation of compounds soluble only with difficulty; and the role of pH should be determined chiefly through its effect on hydrogen separation. In work on the nature of the pH effect on corrosion of iron in the presence of inhibitors, tests were made with both pure hydrochloric acid (HCl) and also in the presence of additives: anthranilic acid and tetrabutyl‐ammonium sulphate (TAS). The corrosion rate was determined as usual by loss in weight and expressed in units of current density (amp./sq. cm.). Preliminary tests showed that only in weak solutions (pH 0.61 and 1.06) containing TAS was any divergence noticeable—in connection with the increased role of oxygen depolarisation — between results of quantitative and volumetric methods. Therefore in the present case the corrosion rate is calculated from the volume of separated hydrogen. The pH value was measured with a glass electrode and amplifier, and controlled both before and after test. The tests were made in an aero‐thermostat at 20° ±0.5° and each lasted 24 hr.

The purpose of this paper is the definition and the implementation of a simplified mathematical model to estimate the hazard and the risk related to the use of high‐pressurized hydrogen pipeline.

This study aims to investigate the effects of different hydrogen operations conditions and to tackle with different release or failure scenarios. Based on the combination of empirical relations and analytical models, this paper sets the basis for suitable models for consequence analysis in terms of estimating fire length and of predicting its thermal radiation. The results are compared either with experimental data available in the literature, thus by setting the same operations and failure conditions, or with other conventional gaseous fuel currently used.

The findings show that the release rate increasingly varies according to the supply pressure. Regarding the effect of the hole diameter, it hugely affects the amount of hydrogen escaping from the leak, up to a value of approximately 0.3 m, after which the release rate remains fixed at a maximum of 43 Kg/s. For failure consequences related to jet flame, the leak dimension has a strength impact on the flame length.

This paper represents a helpful engineering tool, to establish the safety requirements that are related to define adequate safety buffer zones for the hydrogen pipeline in order to ensure safety to people, as well the environment.

This paper aims to evaluate nine types of electrical energy generation options with regard to seven criteria. The analytic hierarchy process (AHP) was used to perform the evaluation. The TOPSIS method was used to evaluate the best generation technology.

The options that were evaluated are the hydrogen combustion turbine, the hydrogen internal combustion engine, the hydrogen fuelled phosphoric acid fuel cell, the hydrogen fuelled solid oxide fuel cell, the natural gas fuelled phosphoric acid fuel cell, the natural gas fuelled solid oxide fuel cell, the natural gas turbine, the natural gas combined cycle and the natural gas internal combustion engine. The criteria used for the evaluation are CO₂ emissions, NOX emissions, efficiency, capital cost, operation and maintenance costs, service life and produced electricity cost.

The results drawn from the analysis in technology wise are as follows: natural gas fuelled solid oxide fuel cells>natural gas combined cycle>natural gas fuelled phosphoric acid fuel cells>natural gas internal combustion engine>hydrogen fuelled solid oxide fuel cells>hydrogen internal combustion engines>hydrogen combustion turbines>hydrogen fuelled phosphoric acid fuel cells> and natural gas turbine. It shows that the natural gas fuelled solid oxide fuel cells are the best technology available among all the available technology considering the seven criteria such as service life, electricity cost, O&M costs, capital cost, NOX emissions, CO₂ emissions and efficiency of the plant.

The most dominant electricity generation technology proved to be the natural gas fuelled solid oxide fuel cells which ranked in the first place among nine alternatives. The research is helpful to evaluate the different alternatives.

The research is helpful to evaluate the different alternatives and can be extended in all the spares of technologies.

The research was the original one. Nine energy generation options were evaluated with regard to seven criteria. The energy generation options were the hydrogen combustion turbine, the hydrogen internal combustion engine, the hydrogen fuelled phosphoric acid fuel cell, the hydrogen fuelled solid oxide fuel cell, the natural gas fuelled phosphoric acid fuel cell, the natural gas fuelled solid oxide fuel cell, the natural gas turbine, the natural gas combined cycle and the natural gas internal combustion engine. The criteria used for the evaluation were efficiency, CO₂ emissions, NOX emissions, capital cost, O&M costs, electricity cost and service life.

This study aims to shed light on the corrosion behavior of X80 steel when sulfate-reducing bacteria (SRB) and permeating hydrogen interact.

In this study, electrochemical tests were conducted between 25 and 55 °C, and the surface morphology of the specimen was observed using scanning electron microscopy and three-dimensional photos. The composition of the oxide film was characterized by X-ray photoelectron spectroscopy (XPS).

Under the condition of 6 MPa simulated natural gas (15% H₂), the content of S-containing compounds (FeS and FeSO₄) in the corrosion products on the surface of the specimen decreases from 60.8% to 54.4%. This finding indicates that hydrogen permeation inhibits the metabolic processes of SRB in this environment. By comparing the hydrogen-uncharged specimen, it was found that under the condition of 6 MPa simulated natural gas (15% H₂) hydrogen charging, the uniform corrosion on the X80 surface was weakened, and the protection of the oxide film on the specimen surface in this environment was better than that without hydrogen charging.

To the best of the authors’ knowledge, most of these existing studies have focused on the effect of hydrogen on the mechanical properties of materials and very little is known about corrosion behavior in the hydrogen environment. In this study, a self-designed small gas phase hydrogen charging device was used to study the X80 surface corrosion behavior in the environment of the H₂-doped natural gas pipeline.

The future of the current family of wide‐bodied transports is examined in the environment of the changing world‐wide fuel supply situation. Synthetic hydrocarbon and cryogenic fuels are considered in the context of impact on airline fleets and their maintenance. The probability of the emergence of new technology aircraft, still utilising hydrocarbon fuel is considered in view of the possible shortening of their useful life by the introduction of cryogenic fuels. Possible effects on maintenance of the new technologies which would be included in such aircraft are discussed. Finally, the characteristics of the two most promising cryogenic fuels are compared and the effects of one of these fuels on fuel system design, maintenance, and service as well as facilities and equipment are reviewed.

Galvanic corrosion It is commonly held that it is the electrochemical potential between two surfaces that is the controlling factor for the rate of corrosion. Table 1.2 in chapter one of this series lists the standard oxidation potentials. However, the difference between the potentials of the two metals plus the difference in the e.m.f. due to the concentration of ions is the reversible electrochemical potential, which only applies when there is no current flowing. The degree of corrosion that occurs is based on the potential difference existing when there is a known current flowing. Thus the baser of two connected metals can be extremely corrosion‐resistant, even if the potential difference is quite large, provided at least one of them has good polarisation characteristics. Metals that are particularly damaging to ferrous metals not only have a very low potential, but are also to all practical purposes insoluble in the corrosive environment around the steel. Thus it is that one of the worst is copper.

Although under many conditions a carefully made weld should introduce no special corrosion risk, the fact remains that welding raises special corrosion problems. The reasons are discussed by Dr. Evans in the first part of his article. He then considers in particular the corrosion of welded stainless steel and aluminium alloys, corrosion fatigue, and hydrogen blistering and cracking.

In tomorrow's world there will be more attention paid to the conservation of materials and energy. Energy is often a significant input in the production of materials. A greater realisation of the degradation mechanisms (and particularly corrosion) must be achieved in that corrosion is ‘an insidious consumer of our stocks of raw materials, a squanderer of our productive capacity and a dissipator of the fruits of our labours’. In real terms it costs about 4 per cent of the GNP of the UK, USA, or Japan and this is wasted ‘labour’. Another way of looking at these figures is to remember that a third of all the steel produced in the UK in one year goes to back to rust within the year.

The different performance tests were conducted on diesel engine compression ignition (CI) mode and CRDi engine.

The CI engine was suitably modified to CRDi engine with Toroidal re-entrant combustion chamber (TRCC) and was run in dual-fuel (DF) mode. Hydrogen (H₂) was supplied at different flow rates during the suction stroke, and 0.22 Kg/h of hydrogen fuel flow rate (HFFR) was found to be optimum. Diesel and biodiesel were used as pilot fuels. The CRDi engine with DF mode was run at various injection pressures, and 900 bar was found to be optimum injection pressure (IP) with 10o before top dead center (bTDC) as fuel injection timing (IT).

These operating engine conditions increased formation of oxides of nitrogen (NOx), which were reduced by exhaust gas recycle (EGR). With EGR of 15%, CRDi engine resulted in 12.6% lower brake thermal efficiency (BTE), 5.5% lower hydrocarbon (HC), 7.7% lower carbon monoxide (CO), 26% lower NOx at 80% load as compared to the unmodified diesel engine (CI mode).

The current research is an effort to study and evaluate the performance of CRDi engine in DF mode with diesel-H₂ and BCPO-H₂ fuel combinations with TRCC.