Experimental and Modelling Study on Emission of Volatile Nitrogen Derived NO during Pressured Oxy-fuel Combustion under Wet Flue Gas Environment

Pressurised oxy-fuel combustion(POFC)is a clean and efficient combustion technology with great potential.Due to the recycling of flue gas,the concentration of steam in the flue gas is higher than that of conventional combustion,which enriches the free radical pool in the flue gas and thus affects the emission of gaseous pollutants.Therefore,further research into the effect of high steam concentrations on NO_(x)emission mechanisms in POFC is necessary.In this work,a fixed-bed reactor was used to conduct combustion experiments of volatiles and combined with chemical kinetic models to study the NO release characteristics for different pressures and steam concentrations in an O_(2)/CO_(2)atmosphere at 800℃/900℃temperature.The results of the study indicated that the volatile nitrogen comes from the pyrolysis of part of pyrrole,pyridine,and all quaternary nitrogen in coal.The increase in temperature promoted the formation of NO during combustion.Higher pressure affects the main reaction pathway for NO formation,promoting NO consumption by HCCO and C_(2)O groups while enhancing the overall NO reduction.Steam promoted NO consumption by NCO.In addition,steam increased the amount of H/OH groups during the reaction,which affected both NO formation and consumption.However,from the overall effect,the steam still inhibits the emission of NO.

Expansion characteristics of twin combustion gas jets with high pressure in cylindrical filling liquid chamber

To deal with the problem of how to control the interior ballistic stability in the bulk-loaded liquid propellant gun, the expansion and mixing process of the twin combustion-gas jets with high temperature and pressure in a liquid medium is studied in the cylindrical filling liquid chamber. A series of the jet expansion shapes is obtained by using a high-speed photographic system. The influences of the jet pressure on the jet expansion shape are discussed. Based on the experiments, the three-dimensional mathematical model is established. The expansion processes of the twin gas jets in the liquid medium are simulated by means of fluent to get the pressure, density, temperature, velocity contours and evolutionary process of vortices. Results show that the jet external out-line and tops are all irregular. The Kelvin-Helmholtz instability is shown in the whole expansion process. The numerical simulation results of the axial displacement of the twin gas jets in liquid agree well with the experiment.

Experimental study on combustion pressure oscillation of soybean bio diesel oil

The principal objectives of this study were to examine in-cylinder combustion pressure oscillation characteristics of soybean biodiesel in time domain and time-frequency domain,and their influences on the control and operational parameters,such as injection timing,exhaust gas recirculation(EGR)ratio,engine load and engine speed.In this study,the combustion pressure oscillation characteristics of biodiesel engine for various injection timing,EGR ratio and engine speed were investigated.The corresponding relation of pressure characteristics in the time domain and frequency domain were obtained.The results showed that the pressure oscillation and peak pressure rise acceleration occurred mainly in the diffusion combustion,and the peak pressure rise rate located in the premixed combustion.The in-cylinder pressure level curve can be divided into three stages.The pressure levels of stage 1,stage 2 and stage 3 represent the peak in-cylinder pressure,the maximum amplitude of pressure rise rate and pressure rise acceleration,respectively.As the injection timing retards,the pressure levels of stage 1 and stage 3 decrease gradually.The pressure level curve of stage 3 with 25°before top dead center(BTDC)is the highest and the oscillation is the most significant.It is worth noting that the location of each stage with various operate conditions is not fixed.At 0.41 MPa indicated mean effective pressure(IMEP),with the increase of EGR rate,the pressure levels of stage 1 and stage 2 decrease gradually.The pressure level curve of stage 3 and the maximum amplitude of pressure rise acceleration with 0%EGR rate are the highest.The oscillation with 0%EGR rate is the most significant at 0.41 MPa IMEP.Compared to 0.41 MPa IMEP,the frequency bands of stage 1 and stage 2 at 1.1 MPa IMEP are relatively low due to the soft combustion in the cylinder.As EGR rate increases,the pressure level of stage 1 decreases,and those of stage 2 and stage 3 increase gradually.The oscillation with 30%EGR rate is the most significant.With the increase of engine speed,the pressure levels of stage 1 and stage 2 decrease,and move to the low frequency.The pressure level in the high frequency domain at 1600 r/min is less than that at 1100 r/min,and the combustion process is smooth.