Optimal Combination of Mixing Units Using the Design of Experiments Method

A passive micromixer was designed by combining two mixing units: the cross-channel split and recombined (CC-SAR) and a mixing cell with baffles (MC-B). The passive micromixer was comprised of eight mixing slots that corresponded to four combination units; two mixing slots were grouped as one combination unit. The combination of the two mixing units was based on four combination schemes: (A) first mixing unit, (B) first combination unit, (C) first combination module, and (D) second combination module. The statistical significance of the four combination schemes was analyzed using analysis of variance (ANOVA) in terms of the degree of mixing (DOM) and mixing energy cost (MEC). The DOM and MEC were simulated numerically for three Reynolds numbers (Re = 0.5, 2, and 50), representing three mixing regimes. The combination scheme (B), using different mixing units in the first two mixing slots, was significant for Re = 2 and 50. The four combination schemes had little effect on the mixing performance of a passive micromixer operating in the mixing regime of molecular dominance. The combination scheme (B) was generalized to arbitrary mixing slots, and its significance was analyzed for Re = 2 and 50. The general combination scheme meant two different mixing units in two consecutive mixing slots. The numerical simulation results showed that the general combination scheme was statistically significant in the first three combination units for Re = 2, and significant in the first two combination units for Re = 50. The combined micromixer based on the general combination scheme throughout the entire micromixer showed the best mixing performance over a wide range of Reynolds numbers, compared to other micromixers that did not adopt completely the general combination scheme. The most significant enhancement due to the general combination scheme was observed in the transition mixing scheme and was negligible in the molecular dominance scheme. The combination order was less significant after three combination units.

Type Synthesis of the Deployable Mechanisms for the Truss Antenna Using the Method of Adding Constraint Chains

In the deployable mechanism for a conventional truss antenna, the nodes cannot be adjusted to be uniform in attitude. To solve this problem, a method of adding constraint chains is proposed based on the reciprocal screw theory. By performing type synthesis of the deployable mechanisms for the truss antenna, a novel deployable mechanism is developed that not only enables complete folding and unfolding but also allows the attitude of the nodes to be made uniform. First, according to the unit division of the antenna reflection surface and the characteristic motions of the nodes, constraint chains that can be added between two adjacent nodes are synthesized based on the reciprocal screw theory. Second, to improve the overall rigidity of the mechanism, a series of basic developable unit mechanisms is obtained by adding virtual constraint chains, again based on the reciprocal screw theory. Next, a method of dividing the minimum combination unit of the curved-surface antenna mechanism is proposed. The design of the minimum combination unit mechanism is optimized, such that the attitude of all nodes in the final folded state can be made consistent. Finally, the feasibility of the optimized minimum combination unit mechanism is verified by simulation analysis. The proposed method for type synthesis provides a new approach to the design of deployable mechanisms for truss antennas, and novel deployable mechanisms for the curved-surface truss antenna with better performance are obtained.