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Competition in a Modified Gradostat
Published in Ovide Arino, David E. Axelrod, Marek Kimmel, Mathematical population dynamics, 2020
This brings us finally to the point of the present paper. We conjecture that coexistence can occur in the gradostat when the competitors’ growth curves intersect and when the operating parameters are such that environments are created in the two vessels which allow each species to be the superior competitor in one of the two vessels. The superior competitor in each vessel is unable to eliminate its rival in that vessel, due to the steady influx of the rival species (immigration) from the vessel in which it is the superior competitor and by the fact that the superior competitor is obliged to dilute its strength by the constant outflow to the other vessel (emmigration), in which it is the inferior competitor. More precisely, we conjecture that it is the mobility of the competitors that facilitates coexistence. This is a well-known phenomena in population ecology and has been referred to as the “rescue effect” (see Brown and Kedric-Brown, 1977). Quoting from Stevens (1989), “The sites where a species is successful become source areas for colonists that sometimes arrive in habitats to which they are poorly suited. Populations of these poorly suited arrivals cannot be excluded through competition with better-adapted locals because their population dynamics depend on the proximity of areas where they do well, not on local conditions.”
An Experimental Investigation on Flame Stability and Lean Extinction Limit in Tubular Flame Burners Operating on Jet Fuel
Published in Combustion Science and Technology, 2022
Yiran Feng, Wenyuan Qi, Yifan Zhou, Yuyin Zhang, Liqiao Jiang, Haolin Yang
In this work, the combustion stability and extinction limits of multi-staged tubular flame burner (MSTF) were investigated in comparison with the conventional rapidly mixed (RMTF) tubular flame burner when operating on RP-3 jet fuel. A planar laser induced fluorescence (PLIF) system and a 3D CFD numerical modeling were applied to observe the fuel-air mixing processes of MSTF and RMTF burners at cold conditions. PPI and IOU methods were adopted to analyze combustion characteristics of MSTF and RMTF. The mechanism for expansion of extinction limit of MSTF burner has been identified based on the experimental and numerical results. The conclusions are summarized below: A stable tubular flames can be established without flash-back for both multi-staged tubular flame (MSTF) burner and rapidly mixed tubular flame (RMTF) burners in a wide range of equivalent ratios for RP-3 jet fuel. The lean extinction limits were found to be Фg= 0.26 for multi-staged tubular flame (MSTF) burner and Фg= 0.40 for rapidly-mixed tubular flame (RMTF) burner under experiment conditions of Table 2.Multi-staged tubular flame (MSTF) burner has much more stable flame than rapidly mixed tubular flame (RMTF) burner which has been evidenced by both the irradiance analysis and the morphology analysis of flame.PLIF measurement results indicate that the fuel-air mixture distributes itself more uniformly for multi-staged tubular flame (MSTF) burner than that for RMTF burner in the downstream of the burnersMulti-staged tubular flame (MSTF) burner has a broad range of lean extinction limit because there is a fuel rich region in the upstream of the burner slits which increases the fuel resident time thus stabilizing the flame through mutual kinetic rescue effect, while rapidly mixed tubular flame (RMTF) burner is completely different in this point.