Engineering topics

Schefer, R. W.

Publications and source records attributed to Schefer, R. W..

5 records

NASA NTRS1977

Interferences in chemiluminescent measurement of NO and NO2 emissions from combustion systems

Two factors that may affect the quantification of NO and NO2 concentrations when using chemiluminescent analysis are investigated. The first is the dependence of the chemiluminescent intensity on competing third body quenching reactions. Relative quenching efficiencies are determined as a function of third body concentration for six different species that are common products of combustion. A mathematical expression is derived that allows calculation of the actual concentration of NO, given the indicated concentration of NO and the concentrations of the important third bodies. An example calculation is presented. The second factor investigated involves the conversion to NO of low molecular weight nitrogen-containing species, other than NO2, in commercial NOx converters. Conversion efficiencies for six species are determined using a commercial stainless steel catalyst at 920 K.

Matthews, R. D.↗

NASA NTRS1977

Laboratory studies of lean combustion

The fundamental processes controlling lean combustion were observed for better understanding, with particular emphasis on the formation and measurement of gas-phase pollutants, the stability of the combustion process (blowout limits), methods of improving stability, and the application of probe and optical diagnostics for flow field characterization, temperature mapping, and composition measurements. The following areas of investigation are described in detail: (1) axisymmetric, opposed-reacting-jet-stabilized combustor studies; (2) stabilization through heat recirculation; (3) two dimensional combustor studies; and (4) spectroscopic methods. A departure from conventional combustor design to a premixed/prevaporized, lean combustion configuration is attractive for the control of oxides of nitrogen and smoke emissions, the promotion of uniform turbine inlet temperatures, and, possibly, the reduction of carbon monoxide and hydrocarbons at idle.

Sawyer, R. F.↗

NASA NTRS1977

Lean premixed recirculating flow combustion for control of oxides of nitrogen

The objectives of the reported investigation included the demonstration of a system in which combustion can be maintained under very lean conditions. Aspects of pollutant formation and the stability characteristics of the system were studied. An opposed reacting jet model laboratory combustor was employed in the experiments. Results obtained with the aid of an analytical modeling technique based on the computational scheme reported by Gosman et al. (1969) are also presented. The investigation indicates that fuel lean combustion might provide an effective means of achieving low pollutant emission levels.

Schefer, R. W.↗

NASA NTRS1976

Pollutant formation in fuel lean recirculating flows

An opposed reacting jet combustor (ORJ) was tested at a pressure of 1 atmosphere. A premixed propane/air stream was stabilized by a counterflowing jet of the same reactants. The resulting intensely mixed zone of partially reacted combustion products produced stable combustion at equivalence ratios as low as 0.45. Measurements are presented for main stream velocities of 7.74 and 13.6 m/sec with an opposed jet velocity of 96 m/sec, inlet air temperatures from 300 to 600 K, and equivalence ratios from 0.45 to 0.625. Fuel lean premixed combustion was an effective method of achieving low NOx emissions and high combustion efficiencies simultaneously. Under conditions promoting lower flame temperature, NO2 constituted up to 100 percent of the total NOx. At higher temperatures this percentage decreased to a minimum of 50 percent.

Schefer, R. W.↗

NASA NTRS1976

Interferences in the chemiluminescent measurement of NO and NO2 emissions from combustion systems

Two factors which may affect the quantification of NO and NO2 concentrations when using chemiluminescent analysis are investigated. The first is the dependence of the chemiluminescent intensity on competing third body quenching reactions. Relative quenching efficiencies are determined as a function of third body concentration for six different species which are common products of combustion. A mathematical expression is derived which allows calculation of the actual concentration of NO given the indicated concentration of NO and the concentrations of the important third bodies. An example calculation is presented. The second factor which is investigated involves the conversion of low molecular weight nitrogen containing species, other than NO2, in commercial NOx converters. Conversion efficiencies for six species were determined using a commercial stainless steel catalyst at 923 K.

Matthews, R. D.↗