Underground coal gasification, UCG, has been applied on a large scale in the Soviet Union as alternative energy recovery technique since 1960s. A method suitable for US conditions, i.e., shallow depth and large seam thickness, was developed in 10 years and is both basically appropriate for large scale application and economically promising. The application of UCG at great depth is, however, considerably more difficult. Research and development projects on underground gasification at great depth have been carried out in Belgium, France, Great Britain, the Netherlands, and the F. R. Germany for about 10 years. Three field trials have been initiated in France and in Belgium by a joint Belgo-German field project. A number of technical uncertainties and problems resulted in the creation and maintenance of high permeability pathways in the seams and by corrosion of well equipment. Field trials were accompanied by research and development work in universities and other research institutes. Research works at the Technical University Aachen are discussed in this paper.
An analytical procedure of supersonic nozzle flows of gas–particle mixtures is described for the case where a nozzle configuration has previously been prescribed. Thereby, some numerical examples concerning the flow properties of gas-phase and particle-phase are illustrated. There are two equations for determining the gas velocity. One includes a term of the variational cross-sectional area along the whole nozzle length. The other includes a term of the pressure profile, instead of the term of the foregoing area. At the present situation where the supersonic nozzle flows are treated for a given nozzle geometry, the former equation is employed upstream and downstream of the transonic region and the latter is utilized in the transonic region. The numerical perturbation between the above two equations is examined and discussed from a practical point of view.
The present paper is concerned with a predictable model for the temperature change of a horizontally moving hot steel plate cooled by a laminar water curtain. The numerical results calculated by the model presented here give a fairly close agreement with the results of cooling test. The effect of the traveling velocity of the hot plate on the cooling intensity has been examined from a numerical as well as experimental point of view. It has been found that the film boiling occurs even on the water impinging surface beyond a certain traveling velocity, and therefore the cooling intensity is decreased to an appreciable degree. It has been suggested from such facts that there is a critical velocity determining whether the film boiling occurs or not.
Effects of alloying additions on improving the wettability of liquid copper (Cu) to carbon fiber (C) has been quantitatively evaluated by using a newly defined quantity, F, which has the meaning that the larger the F in its magnitiude the better the wettability of a copper alloy to carbon fider. Based on a simple thermodynamical model, F as to the C/Cu system can be easily calculated. The values of F for alloying elements Mo, Cr, Fe, V and Co are comparatively large. These theoretical predictions correspond well to the results in a previous experiment by the present authors on alloying effects to improve the wettability of copper to carbon fiber.
Surface cracking and the effect of predeformation on the cracks of low alloy steel slabs in the continuous casting and the direct rolling processes have been studied by means of hot bending tests simulating the processes using as-cast thin slabs. Two kinds of cracks, i.e., fine transverse cracks in microalloyed steels and severe cracks in low Mn steels, are easily simulated by the deformation in low temperature γ region, if the deformation conditions are suitably controlled. They are markedly suppressed by the slight predeformation at certain conditions on the slab surface during cooling to the bending temperature. These results can consistently be explained in terms of precipitation behavior of carbonitride or sulfide. Suppression of the cracks due to the predeformation is caused by nucleation and coarsening of the precipitates by the deformation, and does not result from γ grain refinement by recrystallization due to the predeformation.
A laboratory study has been made on the mechanical properties of hot-direct-rolled steels containing a small amount of titanium. In the steels processed by hot-direct-rolling, even a small amount of titanium content (0.005-0.02 wt%) which has little effect on the strengthening of the steels processed by conventional reheat-rolling was found to be very effective both in the strengthening and in the low temperature toughening. Chemical analyses and electron microscopy confirmed that in the hot-direct-rolling process, most of titanium is in super-saturated solid-solution during cooling after solidification down to the temperature at the start of hot rolling. The titanium in solution precipitates as very fine particles of titanium nitride during the hot rolling. From a further detailed study of the change in mechanical properties with nitrogen content for the direct-rolled low-titanium steels, it was concluded that the higher nitrogen content steels (more than 40 ppm) are strengthened mainly by TiN particles of non-embrittling type with precipitate during hot rolling. For the lower nitrogen content steels (less than 20 ppm), the main strengthening is caused by TiC particles of embrittling type which precipitate after hot rolling.
In order to demonstrate clearly the damaging mechanism on rail surfaces at the joint subjected to impact blows by train wheels, cyclic impact blow tests and low cycle fatigue tests have been performed using 0.75% C rail steel with different hardness valuse and microstructures. The results are summarized as follows: (1) Under cyclic impact blows, a cyclic softening occurs at an early deformation stage in tempered martensite, but only a hardening occurs following surface cracking afterward in pearlite. (2) Under low cycle fatigue conditions, a cyclic softening at a small strain amplitude gives place to a hardening as the strain amplitude increases in pearlite, although only a cyclic softening occurs more extensively in tempered martensite. (3) The fact that dislocation structures formed under cyclic impact blows correspond to the structural changes observed under cyclic plastic straining suggests that the fatigue behavior under impact blows can be roughly estimated using low cycle fatigue tests.
Using the mechanics of inclusions, the effect of strong fibers on the arrest of a mode 1 crack in a brittle material has been studied. Two effects of fibers on the crack arrest are considered; bridging action and sliding. The fibers bridge the crack and the bridging action reduces the energy release rate during the crack extension. The sliding of the fibers results in an effective increase in the fracture toughness, since the sliding under non-vanishing friction on matrix-fiber interfaces dissipates energy. The reduction in the energy release rate and the increase in the fracture toughness are given in analytical forms which involve the size of a crack, the geometry and distribution of fibers and external and frictional stresses. Diagrams to indicate the stability and growth of a crack reinforced by fibers are presented.
The influence of Mn on the solubility of C in ferrte in equilibrium with cementite was investigated in low-carbon steels containing Mn rangeing from 0 to 1 mass% over the temperature range from 573 to 973 K. The internal friction method was employed together with chemical analysis of C by means of infrared absorption after combustion. It has been clarified that Mn hardly changes the solubility of C in ferrite in equilibrium with cementite (about 0.018 mass% at 973 K), whereas Mn reduces the Snoek peak height despite the fact that the amount of C in solid solution is constant. The proportionality constant K in the equation, Sol. C (mass ppm)=K×Q-1max·(10-4), was experimentally determined as a function of the Mn content. K increases with increase in Mn content; this is speculated to be caused by the lattice strain introduced by Mn atom and/or the chemical interaction between Mn and C atoms.
Our previous research suggests that the interfacial segregation of S during high temperature oxidation is detrimental to the adherence of oxide scale to metal substrate. But the effect of S is often perturbed by other complex factors affecting the scale adherence. In this work the surface segregation of S and the spalling of Al2O3 coating layer were examined on 18 sorts of alloys with and without REM doping or Y2O3 dispersion. It was found that the segregated S promotes the spalling of Al2O3 coating lager, and that REM and Y2O3 suppress concurrently the segregation of S and spalling of Al2O3 coating layer. These detrimental effect of S and suppression effect of REM were confirmed much more clearly on Al2O3 coating layer than oxide scale. On the other hand P had no detrimental effect on the adherence. For practical coating technique it is recommended to suppress the segregation of S. The difference in the effect between REM and Y2O3 will be discussed.
In the determination of the total iron (T. Fe) content in iron ores by X-ray fluorescence spectrometry, the determined value is influenced by the coexistent elements in iron ores, the loss of combined water and the gain of oxygen during the glass bead preparation. In the present work, the phenomena of the loss of combined water and the gain of oxygen have been discussed, and the influence of these phenomena on the determination of total iron content has been studied. The results obtained were as follows: (1) It was experimentally confirmed that the combined water was expelled from the glass bead and iron was converted from the lower to the higher oxidation state, Fe(II)→Fe(III), by the glass bead preparation. (2) The phenomena of (1) had an influence on the FeKα line intensity. The intensity increased when the combined water was expelled from the glass bead. On the other hand, the FeKα line intensity decreased when the gain of oxygen took place. (3) The correction factors for the loss of combined water and for the gain of oxygen were theoretically derived. (4) In the experiments, a good analytical accuracy was obtained after correction of changes in weights of samples (glass beads) induced by fusion.