| OCR Text |
Show The electrostatic measurements were made with a Langmuir probe, a device for determining the electric charge concentration. The main body of the grounded probe was water-cooled and transitioned to a smaller diameter air-cooled tube. The tip of this section was capped with an electric insulator through which an electrically isolated wire passed. The current collected when there was a voltage difference between the wire and the probe body is related to the electron and ion charge concentrations. In this program we were interested only in relative concentrations and so we only report the currents. Most of the data were taken with the probe wire at + 15 V so that it was really the electrons that were being collected. Air cooling was used near the tip so that it would be hot enough to prevent water condensation and shorting to the main body. IGT provided a specially designed water-cooled stainless steel probe that combines a suction pyrometer and a gas sampling probe to trace the local gas temperature and composition. In addition, separate suction pyrometer and sampling probes were also used for monitoring flow properties in the flue gases. B. RESULTS OF MAPPING STUDY The measurements were focused on searching for regions where the electric current is high and axial flow velocity is low, similar to the conditions that existed in the flame stabilization zone in AeroChem's successful cylindrical burner experiments. 1. OQerating Conditions Since the observed features of the ignition and flame stabilization zones depend on various parameters, data were collected at different operating conditions, such as firing rate, excess air, and nozzle velocity. The basic operating mode, producing low NOx levels without the flame stabilizer, was selected as follows : parameters: Flame Stabilizer: Firing Rate: Excess Air: Number of Nozzles: Nozzle Pressure: Off 1 x 106 Btulh (293 kW) 62% 2 15 in. H20 (3.74 kPa) Other measurements were carried out at selected combinations of the following 5 |
