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The paper aims to undertake coal–water suspension combustion, in air and in fluidised bed conditions. Fluidised bed conditions are the best to efficiently and ecologically use fuel. Combustion technologies using coal–water fuels create a number of new possibilities for organising combustion processes so that they fulfil contemporary requirements. The aim of the process was to show how the specificity of combustion of coal–water suspensions in the fluidised bed changes the kinetics of the process, compared to combustion in the air stream. Changes of the surface and the centre temperature and mass of the coal suspension during combustion, and evolution of fuels during process are presented in the paper.

Experimental character of the research required the research stand preparation, as well as working out of the measurements methodology (Kijo-Kleczkowska, 2010). The research stand (Figure 1a) was made of ceramic blocks in which the quartz pipes were put. The heating element of the stand comprised three heating coils of 2.0 kW. Each heater was placed in small quartz tubes. These tubes were built into the quartz tube which was thermally insulated by fibre material Al₂O₃ and which was covered with steel sheet. Combustion chamber constituted the quartz pipe, which was additionally insulated thermally, to keep the necessary temperature of the entering gas and to reduce the heat loss. The compressed air was transported to the quartz tube through the electro-valve, the control valve and the rotameter. This study stand allowed for the comparison of the combustion process of coal–water suspensions, in air and in fluidised bed conditions. To study in the fluidised bed, quartz sand was used. Depending on the velocity of air inflowing from the bottom of the bed, different bed characteristics were obtained – from bubble – to circulating-beds. The fumes were removed outside by means of a fan fume cupboard. To regulate the temperature inside the combustion chamber, the Lumel microprocessor thermoregulator was applied. The regulator controlled the work of tri-phase Lumel power controller supplying the main heating elements (gas heater) allowing to measure the actual temperature with accuracy of measurements to 20°C. The temperature measurements in the combustion chamber were carried out by means of the thermocouple NiCr-NiAl. To establish the centre and surface temperature and mass of the fuel, a special instrument stalk was constructed (Figure 1b). It had two thermocouples PtRh10-Pt, placed in two thin quartz tubes connected to the scale. One of the thermocouples was located inside the fuel, while the other served as a basket which was to support the fuel. It also touched the surface of the fuel. The thermocouples were connected to the computer to record the experimental results. The essential stage of the preliminary work was to make out a suspension, which was a mixture of fuel dust (hard coal dust or dried coal-sludge dust) and water. To produce the suspension it was necessary to prepare fuel dust after grinding and sifting it, and then adding water, to obtain a suspension moisture of 20, 35 or 50 per cent. The hard coal was applied in the research. The analysis of fuel dust (in air-dry state) is shown in Table I. The testing of the porosity of fuel was made with mercury porosimetry, carried out in the Pascal 440 apparatus, applying pressure from 0.1 to 200 MPa. This method involves the injection of mercury into the pores of the fuel, using high pressures (Kijo-Kleczkowska, 2010).

1. Under experimental conditions, during combustion in the fluidised bed, intensive heating of the suspension is observed in the initial stage of the process, followed by the removal of heat from the suspension by the contacting quartz material, leading to lowering of the average fuel temperature and extension of the combustion time, compared to the process carried out in air. 2. Measurements using mercury porosimetry enable the identification of the change of suspension porosity. 3. Devolatilisation and combustion of volatiles lead to an increase in the pores’ size in the fuel and their coalescence. 4. Combustion of fuel leads to the development of cracks in the suspension, and its structure changes under the influence of temperature. Cracks are caused by the formation of thermal stresses inside the fuel. 5. Under experimental conditions, suspension combustion in the fluidised bed causes an increase in volume participation of pores, with larger sizes of pores (3,500-5,000 nm), compared to combustion in the air.

The paper undertakes the evolution of suspension fuel, made of a hard coal and a coal-sludge, during combustion in air and in the fluidised bed.

The development of a theoretical model for predicting the combustion, performance and emission characteristics of a cylinder head porous medium engine becomes necessary due to imposed requirements from the viewpoint of power, efficiency and toxic gases in the exhaust. The cylinder head porous medium engine was found to have superior combustion, performance and emission characteristics when compared to a conventional diesel engine. The paper aims to discuss these issues.

Due to heterogeneous and transient operation of diesel engine under conventional and porous medium mode, the combustion process becomes complex, and achieving a pure analytical solution to the problem was difficult. Although, closer accuracy of correlation between the computer models and the experimental results is improbable, the computer model will give an opportunity to quantify the combustion and heat transfer processes and thus the performance and emission characteristics of an engine.

In this research work, a theoretical model was developed to predict the combustion, performance and emission characteristics of a cylinder head porous medium engine through two-zone combustion modeling technique, and the results were validated through experimentation.

The two-zone model developed by using programming language C for the purpose of predicting combustion, performance and emission characteristics of a porous medium engine is the first of its kind.

The complete system of equations for a theory of laminar flame equations is presented, taking into account both heat conduction and diffusion, and for the case of an arbitrary number of simultaneous reactions. The eigen value problem determining the flame velocity is formulated. Two examples are given in order to show that explicit analytical expressions for the flame velocity can be obtained, which are in good agreement with the results obtained by numerical integration of the equations. In the first example (hydrazine decomposition) one reaction is considered as global reaction. In the second example (ozone decomposition) a hypothesis is introduced for the concentration of the free radical O, which corresponds to the steady‐state approximation generally used in classical chemical kinetics. In both cases the measured flame velocities are between the flame velocities computed with no diffusion, and with a coefficient estimated by Professor Hirschfelder from the kinetic theory of gases. The approximate explicit formulae are obtained without drastic assumptions and using legitimate approximation methods. The assumption used for the ozone decomposition flame has a bearing on a better understanding of the mechanism of chain reactions in general. The method indicated in the paper gives hope that the more complicated chain reactions such as the combustion of hydrocarbons will also be made accessible to theoretical computation.

This study explores a reactor model designed to describe the decomposition, ignition and combustion of energetic materials in combination with real experimental data for these energetic materials. Spatial uniformity is initially assumed which reduces the system of partial‐differential‐equations to a system of ordinary‐differential‐equations that can be easily solved numerically. The phase‐plane is explicitly presented and examined to illustrate how chemistry and temperature evolve in time. The computations provide an understanding of the vast different timescales that exist and illustrate the singularity structure. Following this the effect of including this chemical regime in an environment typically induced by the combustion of these materials, that is within a compressible fluid flow, is pursued.

The purpose of this paper is to report a novel formulation of convective heat transfer source term for the case of flow through porous medium.

The novel formulation is obtained by analytical solution of an idealized dual problem. Computations are performed by dedicated tool for fixed bed combustion named GRATECAL and developed by the authors. However, the proposed method can also be applied to other porous media flow problems.

The new source term formulation is unconditionally stable and it respects exponential decay of temperature difference between the fluid and porous solid medium.

The results of this work are applicable in the simulation of convective heat transfer between the fluid and porous medium. Applications include e.g. fixed bed combustion, catalytic reactors and lime kilns.

The reported solution is believed to be original. It will be useful to all involved in numerical simulations of fluid flow in porous media with convective heat transfer.

The purpose of this paper is to introduce new and modified “staged combustion” cycles in the form of engineering algorithm as a possible propulsion contender for future aerospace vehicle to achieve the highest possible “total impulse” to “mass” of propulsion system.

In this regard, the mathematical cycle model is formed to calculate the engine’s parameters. In addition, flow conditions (pressure, temperature, flow rate, etc). in the chamber, nozzle and turbopump are assessed based on the results of turbo machinery power balance and initial data such as thrust, propellant mixture ratio and specifications. The developed code has been written in the modern, object-oriented C++ programming language.

The results of the developed code are compared with the Russian RD180 engine which demonstrates the superiority and capability of new “thermodynamic diagrams”.

This algorithm is under constraint to control the critical variation of combustion pressure, turbine rpm, pump cavitation and turbine temperature. It is imperative to emphasize that this paper is limited to “oxidizer-rich staged combustion” engines with “single pre-burner”.

This study sheds light on using fuel booster turbopump and the second-stage fuel pump to moderate the effect of cavitation on pumps which reduces tank pressure and, as a consequence, decreases the propulsion system weight.

This paper aims to get an in-depth understanding of the fuel spray characteristics to further improve the emission performance of a lean premixed prevaporized (LPP) combustor with staged lean combustion.

In this paper, the fuel spray characteristics in the LPP combustor are experimentally studied by using particle image velocimetry (PIV), and raw data are processed by image-processing technologies for different inlet conditions. The effects of the fuel allocation and pilot atomizer position on fuel spray characteristics are investigated.

Experiment results show that when only the pilot atomizer is operated, the fuel spray characteristics is worsened by increasing fuel flow rate. The fuel spray fields generated by the pilot atomizer are better at the throat than that at the pilot swirler outlet; when the pilot atomizer and primary injector are operated at the same time with the same inlet fuel air ratio, the spray characteristics are improved by increasing the primary fuel flow rate and decreasing the pilot fuel flow rate. Meanwhile, fuel spray fields generated by the pilot atomizer are better at the throat than that at the pilot swirler outlet.

The present results are useful for further development of the LPP combustor.

An LPP combustor with staged lean combustion technology was proposed; to obtain fuel spray characteristics, image-processing program was compiled; the fuel spray characteristics in the LPP combustor were investigated, especially the effects of the fuel allocation and pilot atomizer position.

Decreasing energy demand due to improved building standards requires the development of new biomass combustion technologies to be able to provide individual biomass heating solutions. The purpose of this paper is, therefore, the development of a pellet water heating stove with minimal emission at high thermal efficiency.

The single components of a 10 kW water heating pellet stove are analysed and partly redesigned considering the latest scientific findings and experimental know‐how in combustion engineering. The outcome of this development is a 12 kW prototype which is subsequently down‐scaled to a 6 kW prototype. Finally, the results of the development are evaluated by testing of an accredited institute.

Based on an existing pellet water heating stove, the total excess air ratio was reduced, a strict air staging was implemented and the fuel supply was homogenized. All three measures improved the operating performance regarding emissions and thermal efficiency. The evaluation of the development process showed that the CO emissions are reduced by over 90 per cent during full load and by 30‐60 per cent during minimum load conditions. Emissions of particulate matter are reduced by 70 per cent and the thermal efficiency increased to 95 per cent.

The result represents a new state of technology in this sector for minimal emissions and maximal thermal efficiency, which surpasses the directives of the Eco label “UZ37” in Austria and “Blauer Engel” in Germany, which are amongst the most stringent performance requirements in the European Union. Hence this design possesses a high potential as heating solution for low and passive energy houses.

This paper aims to study the influences of hydrogen jet pressure on flow features of a strut-based injector in a scramjet combustor under-reacting cases are numerically investigated in this study.

The numerical analysis is carried out using Reynolds Averaged Navier Stokes (RANS) equations with the Shear Stress Transport k-ω turbulence model in contention to comprehend the flow physics during scramjet combustion. The three major parameters such as the shock wave pattern, wall pressures and static temperature across the combustor are validated with the reported experiments. The results comply with the range, indicating the adopted simulation method can be extended for other investigations as well. The supersonic flow characteristics are determined based on the flow properties, combustion efficiency and total pressure loss.

The results revealed that the augmentation of hydrogen jet pressure via variation in flame features increases the static pressure in the vicinity of the strut and destabilize the normal shock wave position. Indeed, the pressure of the mainstream flow drives the shock wave toward the upstream direction. The study perceived that once the hydrogen jet pressure is reached 4 bar, the incoming flow attains a subsonic state due to the movement of normal shock wave ahead of the strut. It is noticed that the increase in hydrogen jet pressure in the supersonic flow field improves the jet penetration rate in the lateral direction of the flow and also increases the total pressure loss as compared with the baseline injection pressure condition.

The outcome of this research provides the influence of fuel injection pressure variations in the supersonic combustion phenomenon of hypersonic vehicles.

This paper substantiates the effect of increasing hydrogen jet pressure in the reacting supersonic airstream on the performance of a scramjet combustor.

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