Gasdynamic stimulation of combustion of lean fuel mixtures. 2. Evaluation of thermodynamic parameters and the magnitude of heat losses

Various gasdynamic regimes of combustion of a lean fuel mixture of propane with air, including combustion of the mixture at rest, combustion with annular twisting of the gas, and combustion stimulated by jets of a burning gas injected into the combustion chamber (PJC) were analyzed from the viewpoint of the magnitude of heat losses. The advantage of PJC over other combustion regimes is shown. We suggest a simple method to evaluate the pressure increase by calculating the magnitude of the energy release with allowance for heat losses to the combustion-chamber walls. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 309–312, March–April, 2000.     

A study on flammability limits of fuel mixtures

Flammability limit measurements were made for various binary and ternary mixtures prepared from nine different compounds. The compounds treated are methane, propane, ethylene, propylene, methyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. The observed values of lower flammability limits of mixtures were found to be in good agreement to the calculated values by Le Chatelier's formula. As for the upper limits, however, some are close to the calculated values but some are not. It has been found that the deviations of the observed values of upper flammability limits from the calculated ones are mostly to lower concentrations. Modification of Le Chatelier's formula was made to better fit to the observed values of upper flammability limits. This procedure reduced the average difference between the observed and calculated values of upper flammability limits to one-third of the initial value.     

Solution combustion synthesis of MgAl2O4 using fuel mixtures

The paper reveals a new perspective concerning the rational fuel selection and the logical elaboration of the recipes for the MgAl₂O₄ solution combustion synthesis. It was shown that Mg(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O exhibit different behavior with respect to urea, glycine and β-alanine. Urea proved to be the most adequate fuel for Al(NO₃)₃·9H₂O, while β-alanine proved to be the most appropriate fuel for Mg(NO₃)₂·6H₂O. Considering that there is a predilection of metal nitrates with respect to these fuels, in the case of MgAl₂O₄ combustion synthesis best results were achieved when fuel mixtures (urea and β-alanine, urea and glycine) were used. The use of fuel mixtures allowed the formation of pure, nanocrystalline MgAl₂O₄ directly from the combustion reaction, without any subsequent annealing step. The use of a single fuel (urea, glycine or β-alanine) led to the formation of an amorphous powder, which required further annealing in order to achieve the formation of crystalline MgAl₂O₄.     

预热燃料在无焰燃烧模式下的NO_x排放特性

采用燃料预热燃烧工艺,在30 kW煤粉无焰燃烧实验台上探索高温预热燃料的无焰燃烧可行性,及其燃烧和NO_x排放特性。结果表明:高挥发分的神木烟煤和低挥发分的气化细粉灰均能在该实验系统上实现稳定的无焰燃烧;煤粉经过预热过程,部分挥发份析出,部分焦炭气化,产生高温煤气和煤焦;高温预热燃料(煤焦和煤气)经燃料喷口进入燃烧室,进行分级燃烧,有效降低燃烧温度的峰值,燃烧温度分布更均匀,燃烧温度波动均低于10%;NO_x主要来源于焦炭氮,在燃烧室的下游被焦炭的异相反应所还原;对于神木烟煤和气化细粉灰,NO_x排放分别为90.4、96.7 mg/m~3(O_2体积分数为6%时,@6%O_2)。     

The combustion of a system of liquid fuel drops

We examine the combustion of drops in a system of solitary drops. It is established that the rate of combustion for the system varies with a change in the distance between the drops.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 4, pp. 617–621, April, 1969.     

Some principles of combustion of homogeneous fuel-air mixtures in the cylinder of an internal combustion engine

An algorithm is presented for the problem of flame propagation rate in combustion of a homogeneous fuel-air mixture in the cylinder of an internal combustion engine. It is assumed that the mixture is not overturbulized and that the flame front is spherical. The model used for the phenomenon is based on a turbulent transport mechanism. In the near-wall region the combustion mechanism follows a fine-scale mechanism, but in the core, a large-scale mechanism.Experiments permitted determination of the character and numerical value of coefficients which consider the effect of turbulence on flame front propagation in the combustion chamber of a ZMZ-4021 engine.The principles presented can be used as the basis of an algorithm for heat liberation rate in an internal combustion engine with external mixture formation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 6, pp. 942–947, December, 1990.     

Adsorbed films of 3He-4He mixtures: A systematic experimental study

The results of a systematic study of helium thin-film adsorption are presented. Measurements are reported, obtained with a 24-MHz crystal adsorptometer, on the adsorbed mass per unit area as a function of the three independent variables temperature, concentration, and pressure of the gas of ³He-⁴He atoms generating the adsorbed film. The investigations span concentrations from zero to unity, all pressures up to the dew point for each mixture, and temperatures from 1.3 to 2.1 K. From the experimental results we display the detailed form of the van der Waals attractive potential holding the helium atoms to the surface. The expected dependence on the cube of the distance from the substrate is confirmed over the range of distances explored. The strength of the van der Waals potential is measured and reported. This attractive potential is demonstrated to be of the same form and of the same strength both for the ³He atoms and for the ⁴He atoms in the mixture at all concentrations. We further deduce, directly from our measurements, the detailed relationship between , the mass per unit area of film absorbed, and d, the thickness of the film.German Academic Exchange Service (DAAD) leave from the Free University of Berlin.     

Numerical and experimental study on flame propagating mechanism of a fuel droplet array

The major goals of the researches in combustion science are to provide predictive and controlling capabilities to enhance combustion technology and fire safety. In other words, the practical motivations for combustion study and application research are, owed to the widespread dependence on combustion processes in modern societies. Furthermore, environmental concerns recently dominate needs of combustion research for the realization of low-emissive, efficient energy generation and utilization. The utilization of microgravity is an exceedingly useful tool for the scientific research for realization of physics and dynamics of combustion phenomena, such as spray combustion. Many experiments have been conducted in order to investigate combustion phenomena without natural convection. Now in addition, numerical simulation becomes useful method for further understanding of combustion phenomena. From the fundamental viewpoints, the interactions among fluid dynamics, scalar transport, thermodynamics and chemical kinetics that are characteristic of combustion phenomena have been investigated by above experimental and numerical methods. This paper reports about our efforts on microgravity combustion study. In order to describe the characteristic mode of droplet-to-droplet flame propagation, we conducted the numerical simulations and dropshaft experiments comparing with theoretical prediction models of flame propagation.     

An experimental study on conversion of high-density polyethylene and polypropylene to liquid fuel

Clean Technologies and Environmental Policy - Pyrolysis of plastic material is a potential way for the conversion of plastic into hydrocarbon fuel. Thermal and catalytic pyrolysis of high-density...     

Computational method for investigation of solid fuel combustion in combustion chambers of a heat power plant

Solid fuel combustion in an actual combustion chamber using coal with an ash content of more than 40% for minimization of the deleterious effects (environmental pollution) of heat power plants on environment. The FLOREAN application package was used for simulation and determination of various parameters of combustion.     

Environmentally friendly catalytic combustion of gaseous fuel to heat greenhouses

Data on the study of thermally stable manganese oxide catalysts for deep oxidation of lean CH₄ and propane–butane mixtures in air into CO₂ are presented in the paper. New approaches to the synthesis of polyoxide catalysts based on Mn, modified with rare earth elements (La, Ce) and alkaline earth elements (Ba, Sr) when its supporting from nitrate solutions onto the alumina granules stabilized with 2 % Ce were used in the preparation of catalysts. Polyoxide thermally stable (up to 1473 K) high-performance Mn-containing catalyst for deep oxidation of CH₄ and propane–butane in gas-air mixture was developed. Prototype of the catalytic heat generator for environmentally friendly burning of methane and propane–butane mixture was created. Experienced tests of the catalytic heat generator for heating of greenhouses were performed and carbon dioxide fertilizing of plants by combustion products of propane–butane mixture was carried out.     

Combustion stability of a dispersed fuel in a combustion chamber

A combustion instability criterion and an analogy with the burning of a solid propellant element are established as a result of an analysis of the behavior of the gasdynamic disturbances superimposed on the process of turbulent combustion of an atomized fuel in a one dimensional combustion chamber.     

Effect of the PLAZMAZER plasma ignition system on the fuel combustion regimes in combustion chambers of engines

An economically efficient method of combatting toxic products of incomplete fuel combustion in engines and other movable and stationary power installations by means of pulsed automatic control of the ignition and combustion processes carried out by the PLAZMAZER system is proposed. A new concept of the occurrence of motor knock in internal combustion engines with external carburetion, the stiff operating mode of diesel engines, erosion of turbine blades, burn-out of combustion-chamber and exhaust-line elements, and jet engine compression stalling are presented.     

Reasons for drop in shell-and-tube condenser performance when replacing R22 with zeotropic mixtures. Part 1. Analysis of experimental findings

An experimental and theoretical investigation was made to find out the reasons for the drop in shell-and-tube condenser performance when replacing R22 with a zeotropic mixture R407C. Measurements show that at lower condenser loads the reduction in performance can be as large as 70% compared to the full condenser load. Calculation results are compared with experimental results for two different condensers, one with micro-finned tubes and one with 3-D finned tubes. Calculations show that the degree of mixing of the newly formed condensate on a tube and the drained condensate is a factor influential enough to explain the performance drop. 3-D finned tubes seem to have better mixing in the condensate than integral finned tubes.     

Modelling the combustion of high-ash content solid fuel in circulating systems

G. M. Krzhizhanovski Institute of Power Engineering, Moscow. Translated from Inzhenerno-Fizicheski Zhurnal, Vol. 62, No. 3, pp. 427–435, March, 1992.     

Modelling and experimental study on agglomeration of particles from coal combustion in multistage spouted fluidized tower

An experimental platform of spray agglomeration has been designed and built for removing small fly ash particles (PM₁₀) from coal combustion. Agglomerating model of fine particles during the spray process was developed by combining rapid coagulation theory and analysis of the interaction between droplets and particulates. Systematic experiments were conducted in multistage spouted tower using several kinds of agglomerant solutions. The influencing factors such as surfactant, pH value, flow rate of agglomerant solutions and inlet flue gas temperature were analyzed. SEM was used to analyze the microstructure of the aggregation. Based on this model, coagulation rate constant was calculated and the influences of original parameters were observed. The spray agglomeration mechanism of particles can be analyzed from both macroscopical and microcosmic aspects. Preliminary results are presented and discussed in this work. Final results indicate that the special shape of multistage spouted fluidized tower has significant influences on the effect of agglomeration. The findings from this work will be helpful to form the basis and provide guidance for further studies on the control of fine particles such as PM_2.5 or even smaller ones.     

Kinetics of the self-similar conditions of diffusional combustion of polydisperse liquid fuel

On the basis of the kinetic equation for the particle distribution function with respect to the radius, a method is proposed for calculating the processes of heat and mass transfer in the combustion of liquid fuel of a polydisperse melt.