Graduate Studies


First Advisor

George Gogos

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the degree of Master of Science, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor George Gogos. Lincoln, Nebraska: May 2023

Copyright © 2023 Josh L. Gerdes


Building on flaming using hoods, three new hood designs were created to study the effects of varying propane mass flow rate and secondary air entrainment. Flaming is a method used to control insects and weeds using thermal energy from combustion gases. Flaming is a non-chemical process that can be applied to agricultural crop production to control weeds, and as a result to increase yields.

To build a better understanding of the torch and hood system, a combustion test bench that was used in prior studies was substantially modified. This bench had previously been used to record temperatures using thermocouples at various positions inside and outside of the hood. To increase the rate of data collection, the Y - axis thermocouple control was automated, adding aluminum guides to ensure smooth operation. To improve accuracy, the previously filled soil bins were replaced by fire bricks creating a better surface. An updated data collection system was developed using National Instruments hardware and LabVIEW software. This enabled steady state numerical verification before recording data.

When comparing the various hood/torch setups, an open torch setup is used as a baseline. The following three methods of analysis are used, which provide different strengths of data comparison: a) thermal images, b) area fractions above a threshold temperature, and c) temperature weighted average and weighted standard deviation. When investigating the effects of varying fuel mass flow rates, it was found that with an increase in fuel flow rate the combustion gas temperatures always increased. However, a hood setup with 6” inlet and 2” outlet showed that temperatures inside the hood can drop when excess fuel is used. The torch position played a key role in determining the location of temperature increases. When attempting to control secondary air entrainment, it was found that the inlet height did not provide adequate control. Adjusting the exit height showed to be the most effective method to increase combustion gas temperature for a fixed mass flow rate.

Advisor: George Gogos