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Impact of propeller emergence on hull, propeller, engine, and fuel consumption performance in regular head waves

Ghaemi Mohammad Hossein, Zeraatgar Hamid

Polish Maritime Research

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2022

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nr 4

56--76

EN

In this study, the impact of propeller emergence on the performance of a ship (speed), propeller (thrust, torque, and RPM), a diesel engine (torque and RPM) and fuel consumption are analysed under severe sea conditions. The goal is to describe the variation in the system variables and fuel consumption rather than analysing the motion of the ship or the phenomenon of propeller ventilation in itself. A mathematical model of the hull, propeller, and engine interactions is developed in which the propeller emergence is included. The system parameters are set using model experiments, empirical formulae, and available data for the engine. The dynamic response of the system is examined in regular head waves under submerged and emerged conditions of the propeller. The pulsatility and the extent of variation of 20 selected variables for the coupled system of hull, propeller, and engine are elaborated using quantitative and qualitative terms and absolute and relative scales. The simulation begins with a ship moving on a straight path, in calm water, with a constant speed for the ship, propeller and engine under steady conditions. The ship then encounters regular head waves with a known time series of the total resistance of the ship in waves. Large motions of the ship create propeller emergence, which in turn reduces the propeller thrust and torque. This study shows that for a specific ship, the mean ship speed, shaft angular velocity, and engine power were slightly reduced in submerged conditions with respect to calm water. We compared the mean values of the variables to those in the emerged condition, and found that the shaft angular velocity was almost the same, the ship speed was considerably reduced, and the engine power significantly dropped with respect to calm water. The ratios of the amplitude of fluctuation to the mean (Amp/Mean) for the ship speed and angular velocity of the shaft under both conditions were considerable, while the Amp/Mean for the power delivered by the engine was extremely high. The outcomes of the study show the degree of influence of propeller emergence on these variables. We identify the extent of each change and categorise the variables into three main groups based on the results.

2

Metoda uwzględniania dynamiki statku w procesie wyznaczania bezpiecznej trajektorii

Lazarowska A.

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

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2016

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Nr 51

107--110

PL

Dynamika statku w procesie manewru zmiany kursy zależy od aktualnego kąta wychylenia płetwy steru, aktualnej prędkości statku oraz stanu załadowania. W pracy przedstawiono metodę tworzenia rodziny charakterystyk czasu realizacji manewru w funkcji zmiany kursu dla różnych wartości kąta wychylenia steru oraz prędkości liniowych statku, dla wybranych typów statków. Właśności dynamiczne przykładowych statków obliczane są przy wykorzystaniu oprogramowania MATLAB. Na podstawie obliczeń próby cyrkulacji otrzymywania jest wartość średnicy cyrkulacji ustalonej statku. Następnie obliczana jest prędkość kątowa statku oraz wyznaczane są charakterystyki czasu realizacji manerwu w funkcji zmiany kursu. W dalszej części pracy przedstawiono sposób uwzględniania czasu realizacji manewru w obliczeniach realizowanych przez algorytm wyznaczania bezpiecznej trajektorii statku.

EN

Dynamics of a ship in the process of a course change manoeuvre depends on the current rudder angle, the ship’s speed and loading condition. A method of calculating a family of characteristics, presenting the manoeuvre time as a function of the course change for different values of the rudder angle and the ship’s speed, for different types of vessels is presented in this paper. Dynamic properties of a ship are calculated using the MATLAB software. Based upon the turning circle calculation, a value of the steady turning radius in obtained. Then, the angular velocity of the ship is calculated and characteristics of the manoeuvre time as a function of the course change are determined. After that, a method of taking into account the manoeuvre time in the ship’s safe trajectory determination algorithm is presented and its successful application is proved by results of simulation tests. A heuristic Ant Colony Optimization based algorithm and a deterministic Trajectory Base algorithm were used for the dynamic properties application and evaluation tests, but the method can easily be applied in other algorithms utilizing different optimization methods.

3

Modelling the dynamics of ships with different propulsion systems for control purpose

Gierusz W.

Polish Maritime Research

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2016

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nr 1

31--36

EN

Two different propulsion systems are analyzed from point of view of future control applications. The traditional one consists of a pushing single screw propeller and a blade rudder. The other system is based on pod (pods): pulling or pushing ones. The equations describing forces and moments generated in both systems, are presented. Exemplary results of a simulation in comparison to the real-time experiments for two ships are also shown.