Semester

Summer

Date of Graduation

2022

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Songgang Qiu

Committee Co-Chair

Vyacheslav Akkerman

Committee Member

Vyacheslav Akkerman

Committee Member

Hailin Li

Committee Member

Kenneth Means

Abstract

Nonrenewable resources persist as a necessity for perpetuating the current technology and standards of living maintained throughout the world. Biochar is an alternative and renewable fuel source that constitutes the potential to provide energy comparable to coal. Designing and fabricating components that can efficiently harness biochar’s energy to power machinery would demonstrate a successful renewable energy source. The scope of this research is to explain the feasible design, fabrication, and results of technology involving the burning of biochar and transference of hot combustion products for the purpose of powering a Stirling Engine. This design consists of a solid fuel burner, a heat exchanger that provides hot air directly to heat up the Stirling engine, and a heat exchanger necessary for preheating the fresh air that flows into the solid fuel burner. The promotion of complete combustion was accomplished by inputting the appropriate amount of air flow for a reasonable air-to-fuel ratio, feeding a consistent input of solid fuel, preheating the fresh air that flows into the solid fuel burner, and generating secondary combustion by introducing cyclonic secondary air into the upper portion of the combustor. In the design, secondary air inputs are placed in such a fashion that air forces the hot flue gases to travel against the walls in cyclonic motion. The burner’s overall radius decreases as the air moves upwards to complement this cyclonic motion. All fresh air that flows into the solid fuel burner can be preheated by exhaust hot gas through the custom designed recuperator. The implementation of a recuperator increases the temperature of the inlet air moving through the solid fuel burner to improve thermal efficiency. The performance requirement in this application was to provide a minimum of 3000 watts of thermal energy from the solid fuel burner to the Stirling engine’s heat exchanger. During the testing process, the 3000-watt threshold was repeatably met with thermal energy values reaching as high as 7794 watts. The overall maximum temperatures can be summarized as 1250℃ in the secondary combustion zones, 950℃ at the grate, and 600℃ at the fins of the Stirling engine’s heat exchanger according to thermocouple measurements. The reported maximum values were not sustained for durations of time past 2000 seconds due to inconsistent feeding rates instigated by the feeding design and fuel supply. The design proved technology surrounding the burning of biochar can provide meaningful results and with further modifications could demonstrate those results for higher time intervals.

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