Untersuchung der Zündung von Biogas in einem optisch zugänglichen Motor mit aktiver Vorkammer

Investigation of the ignition of biogas in an optically accessible engine with active pre-chamber

authored by: Jan Wichmar
supervised by: Friedrich Dinkelacker
Abstract: The use of renewable energies such as electricity and heat from biogas plays a crucial role in transitioning to a sustainable energy system. Improving efficiency and reduc-ing emissions are additional measures on the path to achieving set climate goals. When utilizing biogas in cogeneration plants, a lean combustion process is recom-mended to reduce nitrogen oxides while maintaining high efficiency. The use of active pre-chamber ignition shows great potential in this regard, but there is currently a lack of sufficient data specifically related to biogas. Due to numerous influencing factors, active pre-chamber ignition is a complex and challenging process. This study focuses on investigating the combustion process in terms of fundamental design parameters and their impact on the potential and opera-tional limits of pre-chamber ignition with biogas. To examine this, extensive experiments were conducted on an optically accessible engine using biogas with 60 percent methane content as the fuel and various pre-chamber configurations. Simultaneous recording of schlieren and OH* chemilumines-cence during combustion provides valuable insights into the ignition of the main com-bustion chamber by the pre-chamber jets. The experiments were divided into investi-gations of pre-chamber ignition with and without ignition of the main combustion chamber. Additionally, the influence of biogas quality was compared using pure me-thane as a baseline case. The results show very good combustion stability over wide ranges and a positive in-fluence of pressure difference on combustion duration. Two parameter-dependent operational limits for pre-chamber ignition were identified. Upon reaching the lean limit of the main combustion chamber, combustion efficiency gradually decreases due to slowed flame propagation. The extinction limit is defined by the extinguishing of the jet flames upon exceeding a critical pressure difference. By selectively choosing pre-chamber and operating parameters, an optimum between both limits can be achieved. A key parameter for this is the pre-chamber air ratio, which shifts the ex-tinction limit to higher critical pressures in the rich region and, in combination with the nozzle cross-section, determines the resulting pressure differences.
Organisation(s): Institute of Technical Combustion
Type: Doctoral thesis
No. of pages: 152
Publication date: 2024
Publication status: Published
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy, SDG 13 - Climate Action
Electronic version(s): https://doi.org/10.15488/18038 (Access: Open)
https://doi.org/10.51202/9783959009935 (Access: Closed)