Effect of emitter geometry on flow rate sensitivity to voltage in cone jet mode electrospray

Abstract

The effect of voltage on flow rate within cone jet mode electrospraying has been investigated, with particular emphasis on the effect of emitter geometry. A set of experiments investigated the effect of the outer and inner diameters on the flow rate relationship to voltage, in cone jet mode electrospray. This was accomplished by the use of a high fidelity flow meter, capable of measuring changes in flow rate to a fraction of a nanolitre per second.

It has been previously demonstrated that there are two separate parameters that influence the flow rate sensitivity to voltage; the hydraulic resistance of the flow system, and the outer diameter of the emitter. By a simple derivation, the second of these two is explained by the variation of theoretical electric pressure with voltage, as the outer diameter is varied.

Good agreement is found between experimental and theoretical results, suggesting the simple theory reasonably explains the physics of the situation.

As well as elucidating the physics involved in electrospray—suggesting the electric field is an important controlling parameter within cone jet mode electrospray—the theoretical and experimental agreement has important implications for variable throttling of thrust in colloid thrusters, and could bring about better optimization of performance in other electrospray-employing fields.

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