A Practical Approach for Design of Marine Propellers with Systematic Propeller Series
Original scientific paper Although there have been important developments in marine propellers since their first use in 1850, the main concept has been conserved. Parallel to the developments in the computer technologies in the past 50 years, methods based on the circulation theory are often used for the design and analysis of propellers. Due to the ability to predict the propulsion performance with just a few design parameters, the use of systematic propeller series based on open water model experiments is still widespread. The design with standard propeller series is usually made with diagrams developed from model experiments. Reading errors during the use of these diagrams are inevitable. In the presented study a practical approach is developed for preventing reading errors and time loss during the design with standard propeller series. A practical approach based on empirical formulas for the design and performance prediction for four-bladed Wageningen B propeller series is presented, and design applications for three propellers with different loading conditions are realized. The results obtained from the presented method are compared with those of open water diagram data and a good agreement between the results is observed.
Multiobjective Design Optimization of B-Screw Series Propellers Using Evolutionary Algorithms
Methodical series are still widely used in the preliminary design of light- and moderate-duty marine propellers. If the above series enables standard screws to be designed by simple chart methods, they do not help the designer to deal with a complex design involving multiple and conflicting objectives. In this paper, a multiobjective optimization method of B-screw series propeller is introduced that makes use of an evolutionary algorithm maximizing both efficiency and thrust coefficient with a constraint determined by cavitation. The capabilities of the method are illustrated and discussed in detail. The results following the application of the method are given in the form of diagrams, which can be implemented on a common personal computer and used to derive optimal screw configurations in real time.
Fully Integrated Bidirectional CMOS-MEMS Flow Sensor With Low Power Pulse Operation
Leveraging More-than-Moore technology, we demonstrate an integrated CMOS MEMS flow sensor via a very compact system on chip (SoC) that can sense the bidirectional N2 gas flow. Our SoC features a very low-noise instrumentation amplifier that is implemented on a CMOS wafer and serves as a readout integrated circuit for a thermoresistive micro-calorimetric flow sensor which is fabricated on a MEMS wafer. A compact heterogeneous integration is achieved by combining the two wafers via the proprietary InvenSense AlN process. The measured sensitivity of our CMOS MEMS flow sensor is 98 mV/sccm which is three times better than the state-of-the-art counterpart. The flow range measured by our SoC is from −26 to 26 m/s (from −50 to 50 sccm). Moreover, the pulsed heater operation makes this proposed SoC flow sensor a very low power (<9 mW) and, thus, a promising candidate for the Internet-of-Things applications in smart home/green buildings.