Dwight W. Senser

CO and NOx emissions from a controlled-air burner : experimental measurements and exhaust correlations

ABSTRACT We present an experimental study of CO and NOx emissions from a controlled-air burner. Burners of this type are used throughout industry for direct heating of gas streams. A small scale research burner is used which emulates the key geometric features of a typical production burner. Exhaust measurements based on parametric variations of burner operating conditions are combined with insights gained from in situ measurements and from visual observations of flame structure to develop a description of the key mechanisms controlling pollutant production. Combustion within these burners occurs via an ensemble of inverse diffusion flames that stabilize on an array of air holes located on the side plates of the burner. Measurements indicate that the highest flames in the burner control CO emissions. In contrast, NOx emissions are controlled by the lowest rows of lit flames. Owing to this separation, CO emissions can be reduced without significantly affecting NOx emissions. Numerical correlations are deve...

Drop size measurements in electrostatic paint sprays

Drop-sizing experiments were performed on an electrostatic fan-spray atomizer operated in the airless mode. Tests were conducted with and without application of a high-voltage charge to the electrode tip placed downstream of the nozzle exit. A nonintrusive Malvern 2600 particle sizer, based on the forward scattering of a 5 mW He-Ne laser beam, was used to yield line-of-sight and cross-sectional drop size distributions. The atomizer was traversed across the laser beam, and drop size profiles as a function of distance from the centerline were developed. Enamel paint with a viscosity of 17 cp was sprayed over a differential pressure range of 1.38 to 6.20 MPa. Results indicate that at low injection pressures the charge application has a significant effect on the average drop size and the spatial drop distribution. However, as injection pressure is increased, the electrostatic influence on drop size and distribution decreases. >

Constant-tension thermocouple rake suitable for use in flame mode combustion studies

An improved design for a thermocouple rake configuration to be used in fundamental combustion studies is presented. Experience with the constant‐tension thermocouple rake has nearly eliminated thermocouple sensing wire sag which is common using conventional rake configurations.

Practical incinerator implications from a fundamental flat flame study of dichloromethane combustion

This paper discusses a number of results obtained from a hazardous waste flat flame combustion study with implications to full scale incinerators. The results demonstrate that it is possible to obtain DREs of up to 99.95 percent firing mixtures of CH2Cl2/CH4 and air in such a facility. These results are significant since residence times are at the millisecond level. The paper presents DRE results obtained with this CH2Cl2 flat flame system when systematically varying the chlorine loading and equivalence ratio within the flames. Additionally, a PIC DRE is defined as an alternative approach to measure total stack emissions. PIC DRE results are presented for systematic variation of chlorine loading and equivalence ratio. Based upon the data of the paper, a suggested two-stage incineration process is presented which may be both economically advantageous and result in less total PIC emissions as compared with conventional incinerators for certain wastes. The data of this work further indicate that it is kineti...

Peclet correlation for stability of inverse diffusion flames in methane-air cross flows

The effects of jet oxygen concentration, preheat temperature, and a jet diameter on the visual lift-off velocity are reported and correlated using a modified Peclet number. The correlation provides a practical tool for understanding and predicting the extinction characteristics of inverse diffusion flames

Incipient soot formation in dichloromethanemethaneair premixed flames

Abstract Measurements are presented of critical sooting equivalence ratio and peak flame temperature for mixtures of dichloromethane and methane in air. Flame temperature variation was achieved by controlling total mass flux through an atmospheric-pressure, uncooled flat flame burner. A comparison of coated and uncoated thermocouple measurements is given, showing the effect of catalytic surface reactions to be negligible compared to errors in the calculation of radiation loss. The data are correlated using a global model developed for soot inception studies in premixed hydrocarbon flames. The importance of evaluating the correlation in primitive as opposed to parametric variables is shown. The model features two parameters, an activation energy difference and a variable β that has previously been correlated with fuel type in hydrocarbon studies. In chlorinated mixtures, the activation energy difference for incipient soot temperature dependence agrees well with that reported for aliphatic hydrocarbons. The fuel-dependent correlation parameters used for hydrocarbons, C H ratio and number of CC bonds, are not sufficient to explain the behavior of chlorinated mixtures. The parameter β is shown to depend on the Cl H ratio in addition to possible dependence on C H ratio and/or number of CC bonds. Analysis showns this is consistent with the known chemical effects of chlorine on hydroxyl radicals and fuel molecules. At constant temperature, the effects of chlorine on hydroxyl concentration and fuel pyrolysis are shown to be of comparable magnitude.

Specific Charge Measurements in Electrostatic Air Sprays

ABSTRACT An experimental study of the effects of both nozzle parameters and fluid properties on specific charge and ratio of ion to drop current for electrostatic air sprays is reported. The specific gun used and the parameter ranges investigated are indicative of many industrial painting processes. A simple collector system that discriminates between drop and ion currents was used to measure ensemble averaged specific charge for the drops and the ratio of ion to drop current. The data exhibit a coupled dependence on applied potential, liquid flow rate, atomizing airflow rate, and fluid properties. The trends are consistent with contact charging of the liquid and ion generation during breakup of the bulk liquid into drops. Specific charges range from zero to nine μC/g and the ratios of ion to drop currents from zero to six. Analysis of the current ratios indicates that under many conditions the ion charge density near the substrate is small in comparison to the drop charge density. Consequently, the ion charge density may be neglected and only the drop charge density must be considered in simulating the electrostatic fields.