Browsing by Author "Ramesh, U.S."

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Antifouling paint schemes for green SHIPS
(Elsevier, 2019-01-09) Joshi, M.; Misra, S.C.; Ramesh, U.S.
Recent advances in antifouling (AF) paints in general prevent fouling in about 95% of the vessel's immersed surface. However the remaining area which amounts to 5% or less of the total area does get fouled. Although this level of fouling has marginal impact on the routine performance of the vessel it is a predominant vector for the transmigration of invasive species which is now a serious environmental concern. Virtually all ocean going vessels are coated with antifouling paints predominant among them are “Self polishing coatings”. CFD analysis conducted on various types of vessels have indicated that there are certain “hotspots” where the polishing rates are exceedingly high and would polish the AF paints at a much faster rate and ultimately result in the failure of the AF coating. A possible solution to this issue is to first identify these hotspots and suitable paint schemes/formulations are to be applied in such areas. An experimental procedure utilizing a “drum-test” apparatus can be used to compute the coating thicknesses based on wall shear stresses. Such painting schemes would prevent the premature failure of the AF coating in general and significantly reduce the risk of transmigration of invasive species in particular.
Coordinated control of electric tugboats considering inductive power transfer for better fuel efficiency /
(IEEE, 2018-12-01) Ramesh, U.S.
Developments in the shipping industry have necessitated the use of numerous tugboats at harbors for high revenue growth. Over the time, electrification has gained significant potential in transport sector in view of meeting the strict emission norms. Lately, the tugboats are powered with diesel electric generators and energy storage systems to meet its propulsion and auxiliary loads. Optimal use of power sources leads to have better fuel use efficiency with reduced footprint of greenhouse gases. This paper presents an optimization technique for scheduling available power sources to meet onboard load demand. Furthermore, to transfer surplus electric power available in an electric marine vessel to the tugboats in operation nearby, the concept of wireless inductive power transfer (WIPT) is proposed for contactless charging and discharging of tugboat batteries. In addition, doubly fed induction machine (DFIM) as variable speed generator is considered in this paper for tugboat power generation in the interest of better operational efficiency at part load operation. From the test results, it is observed that the tugboat with 50 kWh battery storage system offers 21.4% of fuel saving and 25.5% of fuel saving with proposed WIPT, when compared with conventional tugboat. Further, an additional 2.6% of fuel saving is achieved by adopting DFIM for tugboat power generation.
Energy saving strategy on electric propulsion system integrated with doubly fed asynchronous motors
(IEEE, 2016-11-01) Ramesh, U.S.
Electric propulsion system integrated with doubly-fed asynchronous motor contributes efficient characteristics and flexibility in operation. However, in perception of energy saving and full-scale speed variation, the conventional doubly fed asynchronous motor is limited by the ratings of power converters. Generally, the electrical machines are designed to attain maximum efficiency around the full load. To increase energy saving and operating speed range under lightly loaded condition, the proposed strategy injects a low voltage DC supply to the stator winding instead of full rated AC supply. Wherein the DC supply is obtained from the converter's DC-link instead of external source. The proposed system is mathematically modelled using Matlab/Simulink tool and implemented experimentally with a 2.2 kW doubly fed asynchronous motor. In addition to this, the comparative energy conservation analysis of an electric propulsion system (2 MW) with the proposed strategy is carried out as a case study.
Fuel Minimization in Diesel-Electric Tugboat Considering Flywheel Energy Storage System /
(IEEE, 2018-06-01) Ramesh, U.S.
Energy storage system plays an important role in electric propelled marine vessels for efficient power management. This paper considers flywheel storage system in place of battery storage for reducing fuel consumption in a diesel-electric tugboat. To achieve fuel efficiency, optimal scheduling and controlling of energy sources and energy storage devices take place in consideration with tugboat load demand. A simple fuel optimization problem considering flywheel and battery storage system is formulated. Economic analysis is done in consideration of both the storage systems. Furthermore, DFIM as variable speed generation is considered in this research for tugboat power generation in the interest of better efficiency at part load operation. Fuel usage at fixed speed and variable speed diesel engine with flywheel and battery ESS are correlated. From the test results, it is observed that the adoption of 50kWh battery and 50kWh flywheel ESS offers 21.4% and 23% of fuel reduction in comparison with diesel-mechanical propelled tugboat. Whereas the adoption of variable speed operation of diesel generator with 50kWh flywheel offers 25.6% of fuel reduction.
Underwater noise radiated by fishing vessels in visakhapatnam fishing harbor /
(Journal of Offshore Structure and Technology, 2019-04-24) Kumar, G.V.V. Pavan; Ramesh, U.S.
The sound has always been a better measure to understand the oceans. Among the various sources of underwater noise, mainly physical, biological and anthropogenic, it is seen that through the increase in anthropogenic noise in the oceans, the ambient noise levels are rising. Fishing vessel radiated noise has been a major concern in the fisheries acoustic scientific community due to the possible effects on altering the natural activities of the target species. The fishing vessel noise signature shall be valuable in building a quiet vessel with effective combination of the machinery in opposing excessive noise levels. In the present paper, the measurements of the underwater noise levels within the Visakhapatnam fishing harbor (VFH) limits are detailed to understand the fishing vessel radiated noise levels. The VFH is a bay spreading over 22 ha next to the Visakhapatnam Port channel entrance. At VHF, there are around 700 fishing boats engaged in fishing activity within the coast of Andhra Pradesh. A vertical omni-directional hydrophone and TASCAM handheld linear PCM recorder was deployed at five different locations with deployment depth of 2 m within the VHF bay. Fast Fourier Transformation spectral analysis program is used to post-process the time domain signal to the frequency domain. The measured data helped to understand the ambient noise levels within the VFH limits being ~120 dB re 1 μPa and with a distant boat idling having peak amplitude 136.97 dB re 1 μPa at peak frequency of 425 Hz. The regular fishing vessel movement recorded peak amplitude 160.39 dB re 1 μPa at peak frequency of 425 Hz. The changes in the ambient noise levels due to the fishing vessel movement recorded a significant increase in sound pressure levels (SPL) by about 20 dB. The increase in SPL is mainly due to propeller and machinery radiated noise which is clearly identified in lower frequency range <500 Hz. The measurements also helped to understand the effect of each vessel type on the ambient levels due to vessel movements, mainly during entrance and exit within the VHF bay. However, the noise pollution due to vessel movement has similar effects on the local environment, i.e., the residential area close to VFH.