Pressure-driven flow in a microchannel induces a streaming current due to the presence of an electrical double layer in the interface between the electrolyte solution and channel wall. As the streaming current is of the order of a nano-amphere and is additive, we propose here a method to develop an electrokinetic battery consisting of an array of microchannels that converts the hydrostatic pressure of a liquid into electrical work. We have given oscillating analytical solutions by means of an electrical circuit analysis to model the multi-microchannel battery. Using superposition of the appropriate Fourier series, the derived analytical solutions are useful to predict the current when there is more general time-dependent flow through a microchannel array. To illustrate the idea, we have studied steady-state pressure-driven flow in micropore porous glass filter and compared the results with those predicted from our model. From a 30 cm hydrostatic pressure drop, an external current of 1–2 µA was obtained by means of water passing through the micropore porous glass filter. A larger current can be obtained by simply using a solution with higher salt concentration. This results in a new and potentially useful method of energy conversion by means of an array of microchannels.

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Experiments were conducted to reveal the origins of measured inefficiencies in low-momentum jet diffusion flames in crossflow. Natural gas flames were established at the exit of a burner tube rnounted vertically in a crossflow of air in a wind tunnel, a configuration that is relevant to gas flaring in the atmosphere. At low momentum flux ratios, the flame exists in a wake-stabilized mode and exhibits combustion inefficiencies primarily in the form of emitted unburned fuel. Measurements with a fast flame ionization detector were used to determine the path of the unburned fuel being emitted from the flame. Analysis of the hydrocarbon concentration time series data show that hydrocarbons are ejected from the underside of the flame in a highly intermittent process. A mechanism is proposed in which the mean flow induced by the standing vortex that exists on the leeward side of the stack transports and stretches the ring vortices from the upper shear layer and ejects them on the underside of the flame.

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