Criterion for burner design in thermal weed control

Abstract

A covered infrared burner was designed and constructed so that it could be compared to an open-flame burner. Two covered burners, a high configuration and a low configuration, were constructed. A low configuration covered infrared burner, high configuration covered infrared burner, and an open-flame burner were studied to evaluate the increase in temperature caused by each burner to a target zone. These evaluations were conducted while the burners were traveling at a given speed (2, 3.5, or 5 km/h) and pressure combination (207, 276, or 345 kPa). The temperature increase was referred to as the heat transfer. The target zone levels were monitored individually by thermocouples on the target sensor, a tool developed specifically to aid in data acquisition for the heat transfer experiments. There were four zone levels that were observed: 3.5 and 1 cm above ground, ground level, and 0.5 cm below ground. A set of Temperature versus Time curves was developed for the four zones. The area under the curve, above the threshold boundary, and left of the exposure time boundary was found so that a utilization factor could be calculated. The utilization factor was used as a relative comparison of burner efficiency and performance. Results reveal that there was not a significant rise in temperature in the sub-ground level zone. The observations at the ground level zone varied dramatically due to the intermittent activity of soil particles making contact with the thermocouple. The 1 and 3.5 cm zone levels were a better indication of temperature activity; therefore, conclusions were drawn from observations at these above ground levels. In comparing the utilization factors of the covered infrared burners and the open-flame burner, it was observed that the covered infrared burner performed better than an open-flame burner at any speed and pressure combination even when the covered burner was utilizing all four burners continuously. When comparing the low and high configuration burner, it was observed that the low configuration burner slightly outperforms the high configuration burner when relating to the average utilization factor. This was attributed to the different forms of ventilation used for the low and high configuration burners.