Substantial tidal variations and limited quayside water depths for fabrication yards along the Yellow Sea impose considerable constraints on the loadout workability of heavy offshore structures constructed in the Far-East. Loadout describes the process of moving a completed structure from its construction location in-land to its final position on the deck of a Heavy Transport Vessel (HTV) ready for sailaway. This paper presents a case study for the skidded loadout of two 20,000-ton mega offshore topsides in China. The mega topsides are two out of six facilities making-up Marjan Gas-Oil Separation Plant No. 4 (MRJN GOSP-4) in the Arabian Gulf. To overcome low-tide restrictions and potential vessel grounding during loadout, an innovative solution was implemented whereby the HTV stern was retrofitted with removable external buoyancy tanks during this safety critical operation. The paper shows that this unique solution improved loadout workability from a few days to a few weeks per month over the course of the year. Clients and operators building similar assets in the Far-East can utilize this solution to enhance flexibility in their scheduled sailaway dates. For Marjan project, this innovative approach helped achieve timely sailaway and mechanical completion of the whole offshore GOSP complex.
Ammonia-diesel dual-fuel engines can effectively reduce greenhouse gas (GHG) emissions. Aiming at the real-time control requirements of ammonia/diesel dual-fuel engines, this study proposes a segmented real-time modeling method and a heat release rate model simplification strategy by linearized heat release rate curves. First, the engine working cycle is divided into three parts: intake and exhaust stage, compression and expansion stage, and combustion process. Different simulation steps and modeling strategies are designed to optimize computational efficiency while maintaining the necessary level of accuracy at each stage. Secondly, based on the calibrated heat release rate (HRR) curves, feature points are extracted to construct a simplified linear heat release model. In the absence of calibration data, the characteristic points of the HRR curves are obtained through interpolation. Compared with the commonly used combustion model, the Wiebe model, the proposed simplified model can more easily obtain the parameters required for calibration while maintaining accuracy. Finally, the effectiveness of the model was verified experimentally under various cases. The results showed that the real-time modeling method can keep single-cycle simulation time in 2ms, the prediction deviations of the indicated mean effective pressure (IMEP) under 4% and the peak pressure in the cylinder (pmax) deviations are less than 2%, and the deviations of specific combustion angle (CA10, CA50, CA90) are controlled within 1°crankshaft angle (CA). It provides a model basis for the real-time control of ammonia diesel engines and is of great value in promoting the engineering application of ammonia fuel in transportation fields such as ship power systems.
As global warming caused by greenhouse gases grows (GHGs) into a global environmental threat, carbon dioxide emissions are drawing increasing attention in these years.Among all emission sources, transportation is a major contributor to climate change because of its high dependence on fossil fuels.The International Maritime Organization (IMO) has therefore been promoting the reduction of fuel usage and carbon emissions for container ships by such measures as improving shipping route selection, shipping speed optimization, and constructing clean energy propulsion systems.In this paper, a review of the impact of carbon dioxide emissions on climate change is presented; the current situations of carbon dioxide emissions, decarbonizing methods, IMO regulations, and possible future directions of decarbonizing in the maritime transportation industry are also discussed.Based on the result, it is found that in the case that non intelligent ships still occupy the vast majority of operating ships, the use of new energy as the main propulsion fuel has the defects of high renewal cost and long effective period.It is more likely to achieve energy conservation and emission reduction in the shipping industry in a short period of time by using intelligent means and artificial intelligence to assist ship operation.
Some of the bridges across the Yangtze River in the Three Gorges Reservoir area are in the curved section, and the collision prevention of bridges is a hot issue in the current industry. The system of ships sailing across bridges is a complex system in the discipline of transportation engineering. It is affected by ship conditions, channel conditions, meteorology and hydrology, navigation management and human factors. In order to grasp the influence of turbulent flow near the piers of bridges in curved river sections and oblique flow during variable water level periods on ships crossing bridges, it is necessary to carry out numerical simulation analysis. Methods: By establishing a simple physical model of the water area of the bridge pier, the turbulent flow field of the bridge pier was simulated in two dimensions by Fluent software. Then the turbulent flow characteristics of the single pier and the tandem double pier were compared, and the flow velocity on the upstream side of the bridge pier was used as a parameter to carry out numerical simulation. Finally, the flow-induced drift of the ship is quantitatively calculated in combination with the flow velocity. Conclusion: The two-dimensional simulation confirms that the turbulent width of the bridge pier increases with the increase of the flow velocity. The turbulent width of the tandem double pier is larger than that of the single pier, but the vorticity extending downstream is smaller than that of the single pier. The deflection moment and flow-induced drift of the ship crossing the bridge confirm the risk of ship collision. It is necessary to add a multi-function navigation mark to collect water flow parameters in time, and introduce LED visual navigation in the bridge area to improve the reliability of ship navigation in the bridge area of the curved river section.
