Two-stroke outboard boat engines using total loss lubrication deposit a significant proportion of their lubricant and fuel directly into the water environment. Extensive atmospheric emission testing of outboard motors has taken place, however, emissions to the water are largely unaddressed in the literature and could be critical because the exhaust of most outboard engines is released below the water and mixed by the action of the propeller. The purpose of this work is to document the velocity and scalar field characteristics of a submerged swirling jet emanating from a propeller. The aim is to provide guidance on fundamental characteristics of such a jet, far enough downstream that it is relevant to the eventual modelling of this mixing problem (i.e. the mixing of engine emissions with water). Measurements of the velocity field (axial, tangential, and radial) and scalar field (concentration) were performed in a turbulent jet generated by a model boat propeller (0.02 m diameter) operating in a weak co-flow of 0.04 ms-1. The measurements were carried out up to 50 propeller diameters downstream of the source which was placed in a glass-walled flume, 0.4 m wide with a free surface depth of 0.15 m. The jet and scalar plume development were compared to that of a classical free round jet. Further, results with respect to velocity distribution, turbulence decay and integral flow properties plus scalar distribution, dilution and integral plume properties were all calculated and compared to existing literature. The velocity field results are the first published results to show the development of the flow fifty propeller diameters downstream. Up to ten propeller diameters downstream the results corroborate the earlier work of Petersson [1, 2]. Beyond ten propeller diameters downstream, the walls of the flume affected the flow. The concentration field results show that under these experimental conditions the propeller induced mixing exhibited a complete mixing length some 300 times shorter than for the wall-shear induced diffusion alone. Furthermore, a first principles relation was derived that illustrates the link between engine emission rate and propeller kinematics in generating the propeller-jet source concentration of pollutants. Using experimental results an estimate for benzene concentration fifty propeller diameters downstream of a 74 kW vessel was calculated to be around one third of the regulatory threshold for that chemical.

This paper presents new bonding and surface modification methods for plastic substrates utilizing atmospheric pressure plasma (AP plasma) treatment. Three kinds of AP plasma equipments including after-glow discharge, dielectric barrier discharge and flame type are tested and evaluated for their feasibility of microfluidic device fabrication. The experimental results show that the DBD plasma equipment is the most suitable one for microfluidic applications due to its low temperature and high treating level. Three kinds of polymenr including PMMA, PC and PDMS are used as the sample substrates for evaluating the performance of AP plasma in this study. Experimental results show that the polymer surface turns into hydrophilic after AP plasma treatment. Fourier Transform Infrared Spectroscopy (FTIR) inspection indicates that a new peak corresponding to -C-OH functional group is generated at the wavenumber of 1040 cm-1 after AP plasma treatment. X-ray photoelectron spectrum investigation also shows that the O/C (atom ratio) is 3.5-fold incensement in compare with the bare sample. SEM and AFM observations are utilized to evaluate the surface morphology change after plasma treatment. The measured surface roughness is at the level of several nanometers which is acceptable for most microfluidic applications. We develop two simple and high strength bonding methods for sealing microfluidic deivices in this study. The bonding process can be achieved in 6 minutes and bonding strength of 1.69 MPa and 3.81 MPa can be obtained using direct plasma bonding and ethyl alcohol assisted bonding, respectively. The bonding strength obtained using ethyl alcohol assisted bonding technique reported in this study is the highest one that ever been reported. The feasibility of AP plasma treatment for sealing microfluidic chips are confirmed by three examples including two novel passive microfluidic mixers and one cross-type micro CE chip. Experimental result shows that the mixing performance of the micromixer can reach up to 90% at an operation condition of a low Reynolds number of 4. In addition, micro CE chip sealed with the proposed method can successfully inject and separate dye sample with a long-term stability upto 30 minutes. Separation of 100 bp standard DNA sample of 100 bp to 3000 is also successfully demonstrated with high separation efficiency. It is the author¡¦s firm believes that the proposed bonding method will give substaintial impact on the fabrication of microfluidic device in the future.

The mixing performance of multiple transverse jets has been evaluated experimentally. Measurement techniques included laser Doppler velocimetry and planar laser induced fluorescence. Basic findings are consistent with results presented in literature for single jet mixing behavior. Mixing performance has been compared to literature for the single jet case and the Holdeman parameter has been re-evaluated for effectiveness at low jet numbers. A single jet in a confined crossflow was found to have a local minimum at B(d⁄D) = 0.721. Results for two jets indicate monotonically decreasing unmixedness for the range of conditions tested, with no local optimum apparent. Data for three jets indicate a local optimum at B(d⁄D) = 0.87and relatively flat range of mixing performance in the range of 0.75 < B(d⁄D) < 1.5. Six jets indicate a minimum unmixedness near B(d⁄D) = 0.5, but exhibited poorer mixing performance than all other configurations at the highest values of B(d⁄D)tested. The most optimum configuration tested was six jets at B(d⁄D) = 0.5, resulting in an unmixedness of 0.0192. This value was 76% lower than the next lowest configuration (three jets) at the same B(d⁄D).Total momentum was found to collapse the data well, as configurations more closely matched a historical correlation for second moment of a single confined jet more closely.