Combustion Characteristics of a Single Cylinder Spark Ignition Engine Fueled with Coal Mine Methane

An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane （CMM）.The CMM was simulated by the compressed nature gas （CNG）/nitrogen blend fuels.The cylinder pressure was measured.The maximum heat release ratio,the flame development duration and the main combustion duration were analyzed with the nitrogen volume fraction in the blends changing from 0% to 35%.The results indicate that the maximum cylinder pressure,the maximum rate of pressure,the flame development duration and the main combustion duration increase and the maximum rate of heat release decreases with increasing nitrogen fraction.When the level of nitrogen volume fraction in coalmine methane is lower than 20%,the combustion process of engine is stable.But with the level of nitrogen volume fraction over 30%,the cycle to cycle combustion variation is large,especially under low load condition.

Study on Combustion Performance of the Radial Staged Combustion Chamber with Lobed Nozzles

In order to investigate the effect of the radial gradation of the lobed nozzles on the flow field organization,a cold water model experimental platform for a combustion chamber with radial⁃staged 13-point lobed nozzles is built.Compared with a series of combustion OH*luminescence experiments tested by the University of Cincinnati,the four corresponding working conditions of no load,partial load,cruise and take off are selected.The vortex structure,vorticity value,multi-combustion materiel field and combustion characteristics of the flow field in the radial staged combustion chamber of the lobed nozzles under the equivalence ratio,the fuel injection method,the fuel injection ratio and other factors are numerically studied.The results show that under different influencing factors,the varation trend of the hydroxyl flame field of the lobe combustion chamber is basically the same as that of the hydroxyl light emission experiment of the swirl combustion chamber,but the flame field shape is quite different.The local equivalent ratio has a greater influence on the relevant combustion performance of the combustion chamber.Under the conditions of lower equivalence ratio,three-stage air and fuel injection mode,and gradually transferring the fuel flow of the pilot circuit to the external circuit,the temperature field and flame field of the combustion chamber are more evenly distributed,the outlet temperature field quality is better,the combustion efficiency is higher,and the NO_(X) emission is relatively low.These are basically consistent with the cold test results.The cold experimental results illustrate the importance of the influence of the flow field organization on the combustion organization and verify the reliability of the calculation results.

The experimental study on combustion characteristics and emissions of a CMM fueled engine

In this paper, an experimental study on combustion characteristics and emissions of a single cylinder spark ignition engine fueled with coal-mine methane （CMM） is investigated under various loads. CMM is simulated by the compressed nature gas（ CNG）/nitrogen blend fuels. Based on experiment results, it is shown that under 0% - 35% nitrogen volume fraction in CNG/nitrogen blends, the maximum cylinder pressure, the maximum rate of pressure rise and the rate of heat release decrease, the flame propagation period increases, the center of heat release curve is closed to the top dead centre （TDC）markedly with the increase of nitrogen volume fraction. Meanwhile, the hydrocarbon （HC）, CO emissions increase, the NOx emission decreases apparently with the increase of nitrogen volume fraction.

Effects of Interaction between Axial and Radial Secondary Air and Reductive Intensity in Reduction Region on Combustion Characteristics and NO_(x) Emission of Coal Preheated by a Self-Preheating Burner

The study focused on the effects of the interaction between axial and radial secondary air and the reductive intensity in reduction region on combustion characteristics and NO_(x) emission in a 30 kW preheating combustion system.The results revealed that the interaction and reductive intensity influenced the combustion in the down-fired combustor(DFC) and NO_(x) emission greatly.For the temperature distribution,the interaction caused the position of the main combustion region to shift down as R_(2-12)(ratio of axial secondary air flow to radial secondary air flow) decreased or λ_(2)(total secondary air ratio) increased,and there was the interplay between both of their effects.As R_(3-12)(ratio of first-staged tertiary air flow to second-staged tertiary air flow)increased,the decrease in the reductive intensity also caused the above phenomenon,and the peak temperature increased in this region.For the NO_(x) emission,the interaction affected the NO_(x) reduction adversely when λ_(2) or R_(2-12) was higher,and the range of this effect was larger,so that the NO_x emission increased obviously as they increased.The decrease in the reductive intensity caused the NO_(x) emission increased under the homogeneous reduction mechanism,while was unchanged at a high level under the heterogeneous reduction mechanism.For the combustion efficiency,the interaction improved the combustion efficiency as λ_(2) increased when R_(2-12) was lower,while reduced it as λ_(2) increased excessively when R_(2-12) was higher.The proper decrease in the reductive intensity caused the combustion efficiency increased obviously,while was hardly improved further when the intensity decreased excessively.In this study,the lowest NO_(x) emission was only 41.75 mg/m^(3) without sacrificing the combustion efficiency by optimizing the interaction and reductive intensity.

Combustion effects and emission characteristics of SO2, CO, NOx and heavy metals during co-combustion of coal and dewatered sludge

The influences of dewatered sludge blending ratio in coal on flammability index （C） and combustion characteristic index （S） and release of sulfur dioxide （SO2）, nitrogen oxide （NOx）, carbon monoxide （CO） and heavy metals （Hg, As, Cd, Pb and Cr） were studied. The impact on combustion characteristics could be ignored if less than 20% of dewatered sludge was added in coal. Besides, emission pattern experiments of NOx, SO2, CO and heavy metals were carried out in a high-temperature tubular furnace. Results showed that the conversion rate of NOx and total emission of SO2 reduced with the increase of sludge adding ratio, and a better effect of fixing sulfur could be obtained when the blending ratio reached 30%. Concentrations and distributions of five types of heavy metals in different residues （bottom ash and fly ash） as well as in flue gas were analyzed. It was shown that the characteristics of coal and sludge, as well as the volatilization of heavy metals had a great influence on the distribution of heavy metals.

Combustion Characteristics of Polyethylene and Coal Powder at High Temperature

To study the combustion characteristics of the polyethylene（PE）particle and coal powder at blast temperature of the blast furnace,the contents of CO and CO2 of off-gas during the combustion of PE particle and coal powder at the 1 200 ℃ and 1 250 ℃ were measured using carbon monoxide and carbon dioxide infrared analyzer,and then the corresponding combustion ratio was calculated.The results showed that when the temperature is high,the combustion speed of PE and coal powder is high and the corresponding combustion ratio is high.Whereas,the combustion speed and ratio of PE are much higher than those of coal powder.

Effect of the Mixing Structure Parameters of a Self-reflux Burner on Combustion Characteristics and NO_(x)Emission

To solve the problem of low efficiency of NO_(x)emission reduction in self-reflux burners,this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters.After completing the structural design and optimization of thermal parameters,we continue to adjust the two key structural parameters:the nozzle axis distance and the length of the cylindrical section,to minimize NO_(x)emissions.These are the two parameters that chiefly affect the mixing of flue gas and fuel gas.The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process.The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NO_(x)in the flue gas is reduced from 188.08×10^(–6)to 143.47×10^(–6).However,compared with the nozzle axis distance,the length of the cylindrical section of the burner has little effect on the mixing of the flow field.Under different cylindrical section lengths,the maximum combustion temperature does not change more than 3 K,and the volume fraction of NO_(x)in the flue gas changes within 5×10~(–6).

Effect of methane-hydrogen mixtures on flow and combustion of coherent jets

Coherent jets are widely used in electric are furnace （EAF） steelmaking to increase the oxygen utilization and chemical reaction rates. However, the influence of fuel gas combustion on jet behavior is not fully understood yet. The flow and combustion characteristics of a coherent jet were thus investigated at steelmaking temperature using Fluent software, and a detailed chemical kinetic reaction mecha- nism was used in the combustion reaction model. The axial velocity and total temperature of the supersonic jet were measured via hot state experiments. The simulation results were compared with the experimental data and the empirical jet model proposed by Ito and Muchi and good consistency was obtained. The research results indicated that the potential core length of the coherent jet can be prolonged by optimizing the combustion effect of the fuel gas. Besides, the behavior of the supersonic jet in the subsonic section was also investigated, as it is an important factor for controlling the position of the oxygen lance. The investigation indicated that the attenuation of the coherent jet is more notable than that of the conventional jet in the subsonic section.