The design of a lightweight solar powered marine craft is considered in this report. Various design concepts were considered with respect to the hull type, resistance, aesthetics and the operating environment of the vessel. The planning hull-form catamaran was considered for the boat design. The resistance and other hydrodynamic characterization of boat were analyzed using the CAHI and Savitsky method. Detailed algorithm is developed for the sizing of the various components of the solar PV system for the boat. The hull resistance was found to be 740 N corresponding to the boat speed of 5 knot using the above stated methods. The motor power was obtained to be 2.239 kW (3 HP). Torqeedo outboard electric motor of 3 HP was selected for the boat propulsion. The battery bank was seized accordingly and four batteries of 235 AH and 12 V were selected for the storage of electric power for the boat propulsion. Hence, the solar PV module was sized. It was concluded that, due to the limited space for the installation of the PV module, additional source of power (land base) should be made available to completely charge the battery.
A proper characterization of catamarans performance in relation to demi-hull separation ratio (Sc/L) is imperative for optimal design and applications. Resistance, propulsion and good sea-keeping characteristics for various demi-hull separation ratios at different operating conditions are prime considerations. This work evaluates the Resistance and Propulsion (RAP) characteristics of a 72 m long catamaran for various values of Sc/L (0.3, 0.4 and 0.5).Both physical models and numerical methods are implemented for the analysis. The analysis shows that the frictional resistance (R F ) of catamaran is parabolic and slightly higher than those of monohulls. However, catamarans have superior sea-keeping performance. The R F of catamaran dominates the total resistance (R T ) at low speeds; however, at high Froude number (Fn > 0.25), wave-making resistance (Rw) becomes dominant, especially during humps. Consequently, the R T -curve and the effective power P E -curve oscillate in rhythm with the Rw-curve as the velocity increases. Again, the effect of residuary resistance interference due to demi-hulls separation ratio is marginal, except during humps. Also, four speed-regimes are identified such as: 1) Low-speed (Fn < 0.23); 2) 1 st hump (0.23 < Fn < 0.45); 3) Hollow-wave (0.45 < Fn < 0.60) and 4) 2 nd hump, high-speed (Fn > 0.60). The catamaran P E for Fn > 0.6 is very high and uneconomical. Therefore, for optimal performance, catamarans should have service speed limits not exceeding Fn = 0.6.
Hydrodynamic instability is a prime causative of performance irregularities and violent vibrations in floating-ring bearing (FRB) supported turbosystems. The quest for energy-efficient solutions to this has stimulated the development of diverse FRB design-geometries, dimensional relationships, and surface-contours. Unfortunately, these modifications are characterized mainly by model-predictors, which results lack sufficient test-data to benchmark their authenticities. This work presents the concept and the test-data of flow redirection in FRBs by using an oil-injection swirl-control mechanism (OISCM) to attenuate rotordynamic instabilities. FRBs with radius ratio = 1.75 and clearance ratio = 1.5 are tested for various OISCM angles (0 deg, 30 deg, and 60 deg) and under a specific load = 50 kN/m2. The test results indicate that FRBs with OISCM demonstrate substantial improvements in damping and stability characteristics. Their whirl-frequency-ratio (WFR) and cross-coupled forces are lower because of improved symmetry of films' pressure-forces (Kxx ≈ Kyy). Although the magnitudes of direct damping are higher (|Cxx| = 16.92 kN s/m for 60 deg and 6.03 kN s/m for 0 deg), the load capacity (Kxx) is slightly lower than the normal (0 deg), injection. Nonetheless, this discrepancy in load capacities becomes insignificant for speeds above 22 krpm. The WFR and subsynchronous amplitudes, which are graphic reflections of the bearing-based instability, become progressively smaller with increasing OISCM angle. However, this advantage at elevated speeds can only be sustained by a corresponding increase in oil-supply pressure to circumvent the advent of a starved inner-film and its attendant imbalance response and thermal growth. In closure, the OISCM bearing is more effective for mitigating rotordynamic instabilities in turborotors than conventional FRBs.
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