Due to the harsh weather conditions, severe spatial limitations and extremely high safety requirements, the indoor climate control for offshore oil & gas production platforms is much more challenging than any on-shore situations. For instance, the indoor pressure of man-board quarters should be kept all the way above the ambient pressure according to safety regulations. Meanwhile, the indoor air needs to be regularly changed in order to guarantee the indoor air quality. Both requirements could be possibly achieved by automatically manipulating either the throttle valve located at the terminal of the inlet channel in the considered Heating Ventilation and Air-Condition (HVAC) system, or the pressurization system located inside the inlet channel, or both of them in a coordinated way. A Model-Predictive Control (MPC) solution to control the inlet throttle has been proposed in our previous work. This paper proposes a set of control solutions to regulate the variable speed pressurization fan system such that the energy efficiency of the considered HVAC system can be explicitly considered. A combined feed-forward with a PI-based feedback control solution, and an MPC solution are proposed based on derived simple system models. Some preliminary simulation results show that both control solutions can keep the indoor pressure and the air circulation in a very satisfactory and robust manner, even subject to the presence of severe disturbances.
Our recent experimental investigations of flexible side-by-side blades under both steady and unsteady flows have observed flutter in both scenarios. Flutter significantly impacts blade kinematics and the hydrodynamic drag experienced by the blades. Our numerical approach [1], utilizing the reactive force model, successfully reproduces flutter phenomena. In contrast, the traditional Morison’s equation fails to trigger flutter. In the static regime where flutter does not occur, the bulk drag coefficients calibrated from experiments in steady and unsteady flows can be unified through an effective Cauchy number, allowing for the use of analytical models developed for steady flows in unsteady flows. In the flutter regime, using the bulk drag coefficient from steady flows underestimates the drag load in oscillatory flow.
As of January 2015, the new maximum limit of fuel sulfur content for ships sailing within emission control areas has been reduced to 0.1%. A critical decision for ship owners in advance of the new limits was the selection of an abatement method that complies with the regulations. Two main options exist: investing in scrubber systems that remove sulfur dioxide emissions from the exhaust and switching to low-sulfur fuel when sailing in regulated waters. The first option would involve significant capital costs, while the latter would lead to operating cost increases because of the higher price of the fuel used. This paper presents a literature review of emissions abatement options and relevant research in the field. A cost–benefit methodology to assess emission reduction investments from ship owners is also presented. A study examined the effects of recent drops in bunker fuel price to the payback period of a potential scrubber investment. The results show that lower prices would significantly delay the payback period of such investments, up to two times in some cases. The case studies present the emissions generation through each option for representative short sea shipping routes. The repercussions of low-sulfur policies on large emission reduction investments including cold ironing are examined, along with implications of slow steaming for their respective payback periods. Recommendations are made for research in anticipation of future regulations and technological improvements.