Computation and Experiment of Propeller Thrust Fluctuation in Waves for Propeller Open Water Condition

Tokgoz, Emel; Wu, Ping-Chen; Takasu, Sumire; Toda, Yasuyuki

doi:10.2534/jjasnaoe.25.55

Cited by 3 publications

(2 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Under high wave conditions, the propeller may experience a diminution of thrust and torque due to exposure of the propeller disc above the free surface [28]. This large and abrupt drop in torque may lead to engine over-speed, which is known as propeller racing [25]. The resulting change in the propeller torque is proportional to the loss of the effective disc area of the propeller.…”

Section: Diesel Enginementioning

confidence: 99%

“…The most important outcome of this study was the conclusion that the response of the system, including the engine power, propeller rotation speed and torque, can be determined only through the use of a coupled simulation model when realistic engine and propeller models are employed. Following this, Tokgoz et al [25] carried out experimental and numerical analyses of twin propellers operating behind a hull in regular head wave conditions. They concluded that in regular waves, and at an encounter frequency close to its mean value in calm water, the propeller thrust undergoes harmonic oscillation, with a relatively small amplitude; however, when the propeller blade approaches the water surface and ventilation occurs, the propeller thrust radically changes and decreases.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of Propeller Emergence on Hull, Propeller, Engine, and Fuel Consumption Performance in Regular Head Waves

Ghaemi

Zeraatgar

2022

Polish Maritime Research

View full text Add to dashboard Cite

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.

show abstract

Section: Diesel Enginementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Propeller Emergence on Hull, Propeller, Engine, and Fuel Consumption Performance in Regular Head Waves

Ghaemi

Zeraatgar

2022

Polish Maritime Research

View full text Add to dashboard Cite

show abstract

Analysis of hull, propeller and engine interactions in regular waves by a combination of experiment and simulation

Ghaemi

Zeraatgar

2020

J Mar Sci Technol

View full text Add to dashboard Cite

The goal of this study is to investigate ship propulsion system dynamics under sea wave conditions by including the interaction of hull, propeller, and engine. A mathematical ship propulsion system model was made and the related computer code was developed. To get the results as close as possible to real conditions, measured data for physical models, including the ship’s resistance in calm and sea waves and propeller performance, were implemented in the model. For a diesel engine, performances provided by the manufacturer were used. The wave force time series, as exciting force, changed the propulsion system state from steady to transient. It activated system variables including ship’s speed, advance number, propeller and engine torque, propeller and engine rotational speeds, effective and generated powers, and net thrust. The analysis was performed for a container ship for two regular waves. Using the developed computer code, the ship’s speed and system variables, as well as the consumed fuel and the voyage distance, were calculated and compared with the calm water condition. The voyage mode was set on constant rotational engine speed implementing a P-action governor with fuel rate and engine torque limiters. The outcomes of the research explain the influence of the governor and its limiters on fuel consumption, identify the nonlinear impact of sea waves on propeller characteristics, and underline the effect of voyage mode on system response and the consumed fuel. The results also show that the conventional method for calculating speed reduction based on the added resistance is not capable of justifying the system’s dynamic behaviour.

show abstract

Sensitivity Optimisation of a Main Marine Diesel Engine Electronic Speed Governor

Gorb

Levinskyi

Budurov

2022

Scientific Horizons

View full text Add to dashboard Cite

Electronic speed governors have become widespread on marine diesel engines. In comparison with hydromechanical ones, they have an additional setting parameter – input signal sensitivity. This parameter allows changing the response of governors to high-frequency disturbances. In camshaft diesel engines, such disturbances are generated when the cams run over fuels pump push rods, while in ME (MAN Energy Solutions) or RT-flex (Wärtsilä) engines they result from the use of inductive sensors with a serrated tape on the diesel shaft for speed measurement. If the engine is used as a main engine on vessels, the governor’s sensitivity additionally allows governors to vary the response to propeller shaft resistance moment fluctuations in sea waves conditions. In practice the value of sensitivity of electronic speed governors of main marine engines is selected intuitively. As a result, the adjustment of governors doesn’t provide satisfactory stability of speed modes at the change of sea conditions. The study aims to develop a methodology for adjusting the sensitivity of main engines electronic speed governors with considering the stochasticity of the load on the diesel engine in sea waves state. The study was carried out using the systems of automatic speed control model, which is based on the assumption of relatively small deviations of diesel engine shaft rotation speed and load parameters at sea waves conditions. Considering the character and magnitude of change of load on diesel engine at sea waves conditions depend on many variables of external conditions (waves levels, course of a vessel in relation to wind-wave conditions, wind gusts, vessel’s loading condition, given speed of a vessel), any set value of sensitivity of electronic speed governors appears to be optimum only for a particular case of vessel movement in sea waves state. The scientific novelty is defined by the fact that recommendations on the choice of governor sensitivity are determined with considering stochasticity of propeller shaft resistance moment fluctuations at sea waves conditions, that increased accuracy, and validity of recommendations. The practical significance of the research consist in the increase of stability of speed modes of the main engine with electronic speed governor at various sea waves conditions

show abstract

Computation and Experiment of Propeller Thrust Fluctuation in Waves for Propeller Open Water Condition

Cited by 3 publications

References 8 publications

Impact of Propeller Emergence on Hull, Propeller, Engine, and Fuel Consumption Performance in Regular Head Waves

Impact of Propeller Emergence on Hull, Propeller, Engine, and Fuel Consumption Performance in Regular Head Waves

Analysis of hull, propeller and engine interactions in regular waves by a combination of experiment and simulation

Sensitivity Optimisation of a Main Marine Diesel Engine Electronic Speed Governor

Contact Info

Product

Resources

About