Flashback Propensity of Synthetic Gas/air Mixtures in a Generic Non-swirling Jet Injector PDF Download

Author: Zhi-Xuan Duan
Publisher:
ISBN: 9781267745798
Category :
Languages : en
Pages : 130

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Book Description
Various renewable gaseous fuels offer the opportunity to meet increasing energy demands and address concerns regarding global climate change. Synthetic gas generated from biomass is one such fuel that is an attractive potential substitute fuel for current combustion systems to reduce greenhouse gas emissions. Current advanced combustion systems use lean premixed strategies for minimizing criteria pollutant emissions. For the successful use of syngas in light of varying composition in lean premixed low emission combustion systems, an understanding of the role of composition on performance is required. For example, the high hydrogen content of syngas has been shown to affect the operability of combustion systems and, in particular, the risk of flashback. Hence, the focus of this thesis is on flashback in lean premixed flames under the atmospheric condition. The non-swirling jet flame configuration is chosen to isolate specific flashback mechanisms While the major focus is on the effect of fuel composition, the influence of injector diameter, diluent addition, higher hydrocarbon addition, and injector wall temperature are evaluated as well. The experimental setup consists of a quartz tube that serves as an axisymmetric injector. A quartz enclosure is used to assist with flame stabilization for the lower flame speed fuel compositions. The test procedure for approaching flashback establishes a target adiabatic flame temperature which is held constant while decreasing the mixture flow rate until flashback occurs. To add insight into the flashback mechanism, high speed schlieren imaging is employed to document the dynamic processes of flashback. Observations include 1. The schlieren images indicate the flashback in the present research typically starts in the boundary layer. 2. Different flame stabilization modes occur which have differing flashback tendencies. 3. Flashback propensity increases generally following the trend of laminar flame speed. More hydrogen and higher wall temperatures yield higher a tendency to flashback. 4. There are other factors determining the scale of flashback propensity. It is found that given a similar laminar flame speed and the same mixing ratio (1:1), the flashback propensity of H2/CO is nearly three times more prone to flashback than the mixture of H2/CH4. 5. The laminar flame speed alone cannot predict the flashback propensity. Interactions among other variables, such as wall temperature and fuel properties etc. also affect the flashback. 6. Addition of diluents over a limited range did not strongly impact flashback 7. Addition of ethane to hydrogen reduces flashback propensity more than does the addition of methane or diluents. 8.A statistical model estimates the present test result very well.