Measurements of Non-reacting and Reacting Flow Fields of a Liquid Swirl Flame Burner

The understanding of the liquid fuel spray and flow field characteristics inside a combustor is crucial for designing a fuel efficient and low emission device.Characterisation of the flow field of a model gas turbine liquid swirl burner is performed by using a2-D particle imaging velocimetry（PIV）system.The flow field pattern of an axial flow burner with a fixed swirl intensity is compared under confined and unconfined conditions,i.e.,with and without the combustor wall.The effect of temperature on the main swirling air flow is investigated under open and non-reacting conditions.The result shows that axial and radial velocities increase as a result of decreased flow density and increased flow volume.The flow field of the main swirling flow with liquid fuel spray injection is compared to non-spray swirling flow.Introduction of liquid fuel spray changes the swirl air flow field at the burner outlet,where the radial velocity components increase for both open and confined environment.Under reacting condition,the enclosure generates a corner recirculation zone that intensifies the strength of radial velocity.The reverse flow and corner recirculation zone assists in stabilizing the flame by preheating the reactants.The flow field data can be used as validation target for swirl combustion modelling.

Numerical investigation of gas-particle flow in the primary air pipe of a low NO_x swirl burner-The DEM-CFD method

The gas-particle flow in the primary air pipe （PAP） of a low NOx swirl burner was investigated using the computational fluid dynamics （CFD） coupled with the discrete element method （DEM）. The mathematical models were validated using the measured values obtained at the outlet of the primary pipe through a phase Doppler anemometer （PDA） system. Particles of different Stokes numbers in the primary air pipe （PAP） were investigated, and the effects of the structure of the primary air pipe and the particle-particle interaction on particle dispersion were analyzed. The results indicate that particles under the combined effects of the Venturi pipe and the spindle body are concentrated into a narrow band area and that the PAP structure can more efficiently concentrate particles with large Stokes numbers. The formed fuel rich/lean jet persists for a long distance out of the burner, thereby favoring of air-staged combustion and NOx reduction. The particle collision frequency and its fluctuation range increase as the particle Stokes number increases. The collisions among particles result in an increase of the spanwise dispersion of particles. Experimental results indicate that the models that take particle-particle collision into consideration are more able to predict particle concentration.

Influence of mass air flow ratio on gas-particle flow characteristics of a swirl burner in a 29 MW pulverized coal boiler

In a gas/particle two-phase test facility, a three-component particle-dynamics anemometer was used to measure the characteristics of gas/particle two-phase flows in a 29 megawatt (MW) pulverized coal industrial boiler equipped with a new type of swirling pulverized coal burner. The distributions of three-dimensional gas/particle velocity, particle volume flux, and particle size distribution were measured under different working conditions. The mean axial velocity and the particle volume flux in the central region of the burner outlet were found to be negative. This indicated that a central recirculation zone was formed in the center of the burner. In the central recirculation zone, the absolute value of the mean axial velocity and the particle volume flux increased when the external secondary air volume increased. The size of the central reflux zone remained stable when the air volume ratio changed. Along the direction of the jet, the peak value formed by the tertiary air gradually moved toward the center of the burner. This tertiary air was mixed with the peak value formed by the air in the adiabatic combustion chamber after the cross-section of x/d = 0.7. Large particles were concentrated near the wall area, and the particle size in the recirculation zone was small.

Numerical Simulation of Gas-particle Flows with Different Swirl Numbers in a Swirl Burner

Swirl burner design was optimized by simulating swirl gas\|particle flows with different swirl numbers at the exit of a small\|scale swirl burner for pulverized\|coal furnaces using the k\|ε\|k p model. The predicted two\|phase time\|averaged velocities and particle concentration distributions for several different cases were compared to improve the design. The effect of the swirl number on the two\|phase velocities and particle concentration was investigated. The results give the two\|phase axial and tangential time\|averaged and fluctuation velocities and particle concentrations, showing that large recirculation zones of gas and particles forms in the near\|axis region of the burner exit, but the particle concentration in the recirculating zone is very low.

Simulation of Combustion Flow of Methane Gas in a Premixed Low-Swirl Burner using a Partially Premixed Combustion Model

Because the rotational current stabilizes the flame by creating a recirculation zone,it may increase the risk of reversal.For this reason,low-spin combustion is used to stabilize the flame while preventing flashbacks.Therefore,in this study,the combustion flow of methane gas in a low-swirl burner is simulated using a partially premixed combustion model.Furthermore,the fuel flow rate is considered constant.The research parameters include swirl angle(θ=35°–47°),equivalence ratio(φ=0.6–0.9)and inlet axial flow radius(R=0.6–0.7)and effect of these parameters on temperature distribution,flame length,flame rise length,velocity field,and streamlines of the number of pollutant species are investigated.The contours of streamline,temperature distribution,and velocity distribution are also presented for analysis of flow physics.The results show that with increasing the fuel-air ratio,the strength of the axial flow decreases,and the position of the maximum flame temperature shifts toward the inlet of the reactants.The results also reveal that by increasing the swirl angle of the flow,the position of the minimum velocity value(opposite to the direction of the axis)tends towards the outlet.The results also indicate that the maximum temperature of the combustion chamber increases with increasing the swirl angle,and inθ=35°,the maximum temperature is 1711℃and inθ=41°,this value is 1812℃.Finally,by increasing the swirl angle toθ=47°,the maximum flame temperature position is found at a considerable distance from the inlet and is 1842℃.

Cold Gas-particle Flows in a New Swirl Pulverized-coal Burner by PDPA Measurement

A new type of swirl burner has been developed to stabilize pulverized\|coal combustion by burning different types of coal at different loads and to reduce NO x formation during combustion. The burner uses a device to concentrate the coal powder in the primary\|air tube that divides the primary coal\|air into two streams with different pulverized\|coal concentrations. This paper reports the measurement of gas\|particle flows at the exit of the different swirl burners using a 3\|D Phase Doppler Particle Anemometer (PDPA). The effect of different geometrical configurations on the two\|phase flow field is studied. The results that give the two\|phase flow fields and particle concentrations show the superiority of the new swirl burner.