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Impact of late and early fuel injection on main engine efficiency and exhaust gas emissions

Pavin Z., Knezević V., Orović J., Valčić M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2023

Vol. 17 No. 1

177--181

Exhaust gas emissions from ships are an aspect of the global maritime industry which has been given great importance in recent years. Increasing the efficiency of maritime transport regarding fuel consumption and exhaust gas emissions is an ongoing effort which requires a detailed analysis of all ship systems that have an effect on the aforementioned issue. One aspect that can be analyzed in this regard are the various machinery faults which influence the ships exploitation efficiency. This paper will focus on the analysis of the two stroke slow speed diesel main engine with early and late fuel injection faults. This analysis is based on a set of data acquired from a simulation model of a LCC tanker vessel including fuel consumption and emission pollutants such as carbon monoxide (CO), sulphur oxides (SOX) and carbon dioxide (CO2) as a greenhouse gas with early and late fuel injection fault introduced to different number of main engine cylinders. This methodology of research has the advantage of analyzing various scenarios which are not as easily reproduced on actual vessels.

Derivative free optimal thrust allocation in ship dynamic positioning based on direct search algorithms

Valčić M., Prpić-Oršić J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2020

Vol. 14, no. 2

309--314

In dynamic positioning systems, nonlinear cost functions, as well as nonlinear equality and inequality constraints within optimal thrust allocation procedures cannot be handled directly by means of the solvers like industry-standardized quadratic programing (QP), at least not without appropriate linearization technique applied, which can be computationally very expensive. Thus, if optimization requirements are strict, and problem should be solved for nonlinear objective function with nonlinear equality and inequality constraints, than one should use some appropriate nonlinear optimization technique. The current state-of-the-art in nonlinear optimization for gradient-based algorithms is surely the sequential quadratic programing (SQP), both for general applications and specific thrust allocation problems. On the other hand, in recent time, one can also notice the increased applications of gradient-free optimization methods in various engineering problems. In this context, the implementation of selected derivative free direct search algorithms in optimal thrust allocation is proposed and discussed in this paper, and avenues for future research are provided.