1,721,023 research outputs found
The dynamic of ship propulsion unit-large hull-water interactions
No full textThis paper developed a generalised theory to model the dynamics of an integrated ship propulsion unit-large hull–water interaction system. The engine shaft unit, the hull structure are considered as two substructures and the water as a subdomain, of which the motions of each subsystem are governed by the fundamental laws in continuum mechanics, and on their interfaces, kinematical and dynamical conditions are satisfied. The integrated variational formulation is given, based on which the numerical equation is derived by using the mode summation approach. The shaft frequency and deformation factors are defined to study on its interactions with large hull and water in order to provide a mean for safety propulsion unit design in large ships. An example is given to illustrate the applications of the general theory presented in the paper. Some guidelines which are useful in preliminary design stage for dynamical designs of large ship hull – propulsion system are suggested
Turbocharged two-stroke diesel engine of large vessels modeling and simulation
No full textIn this article, according to the work principle of turbocharged two-stroke diesel engine, the characteristic of volume method model is referenced to package the diesel engine and the packaged model is calculated. According to the Matlab/Simulink software platform, the model will be combined to form a full mean value engine model and join speed controller to control diesel engine speed. The variation of diesel engine’s various performance parameter and the dynamic characteristics based on the speed control law will be observed, which means reaching better purpose of using diesel engine. In the process of mean value engine model design, joining a scavenging coefficient and improving the excess air ratio will increase simulation precision. By means of the correlation analysis, the diesel engine models complying with the control requirements can be determined
Automation system vibration analysis taking environmental factors into consideration
No full textThis paper aims to investigate the vibration behavior of a propulsion system subjected to hull deformations in a two dimension circumstance. As known that large scale ships have great developments in recent years which could cause much severer conditions among the interaction between the propulsion system and ship hull. Excited forces from these a waves could make the ship hull deformed which further cause drastic vibrations of the shaft system. As a result, the malfunctions of shaft propulsion system are potential existed as the vibrations of the shaft always exceed its maximum allowable values.This paper establishes a simplified model of the large ship propulsion-hull system to analyze the vibration behavior of the ship propulsion system subjected to the ship hull deformations. The hull deformations were obtained as the excited forces under different sea conditions. Then base on the simplified 2D model, the effects of propeller, supports stiffness, the location of hull excitations, the amplitude of excitations are discusse
Numerical and experimental analysis of coupled transverse and longitudinal vibration of a marine propulsion shaft
Full text linkVibration characteristics analysis on ship propulsion system taking hull deformations into account
Full text linkBudući da je u brodogradnji očita tendencija izgradnje sve većih brodova, dinamičke interakcije između porivnog sustava i trupa mnogo su oštrije kod velikih nego kod malih brodova. Deformacije brodskog trupa izazvane jakim silama valova mogle bi utjecati na značajke vibracija porivnog sustava preko ležajeva postavljenih na brodu. Pouzdanost i sigurnost porivnog sustava bila bi u opasnosti. U ovom se radu predstavlja matematički model novog pojednostavljenog porivnog sustava u svrhu istraživanja dinamičkih interakcija između brodskog porivnog sustava i deformacija trupa. Deformacije brodskog trupa dobivene su numeričkom analizom kao uzbudne sile pri različitim morskim uvjetima. Zatim su se, na temelju dobivenih deformacija trupa, razmotrili različiti parametri koji su uključivali krutost nosača ležaja u odnosu na karakteristike vibracija porivnog sustava. Rezultati ovoga rada mogu doprinijeti ekonomičnosti i sigurnosti u izgradnji i pogonu brodova.Since an evident tendency of the shipbuilding is that the sizes of ships are larger and larger, the dynamic interactions between the propulsion system and ship hull in large scale ships are much severer than those of the small sized ships. Ship hull deformations caused by the action of heavy excited wave forces could affect the vibration characteristics of the propulsion system through bearings mounted on the ships. The reliability and safety of the propulsion system would be in a dangerous condition. In this paper, a novel simplified hull-propulsion system mathematical model is presented to investigate the dynamic interactions between the ship propulsion and hull deformations. Ship hull deformations were obtained as the excited forces under different sea conditions by numerical analysis. Then, based on the gained hull deformations, variable parameters involving stiffness of support bearings are considered on the vibration characteristics of propulsion. The findings of this work may provide a new insight to keep economy and security in both shipbuilding and ship operation fields
Thermo-Elasto-Hydrodynamic analysis and optimization of rubber-supported water-lubricated thrust bearings with polymer coated pads
No full textIn order to study the lubrication performance of rubber-supported water-lubricated thrust bearings (RWTBs) with polymer coated pads and optimize the offset ratio of rubber cushions, a Thermo-Elasto-Hydrodynamic lubrication performance computational model is proposed. Case studies show that there are concave and convex deformations on the polymer surface under certain load and speed conditions. Deformations decrease the minimum film thickness by 10.9% compared with that calculated without considering deformation. Optimization indicates that the optimum offset ratios of the rubber cushion are 0.585–0.59 in circumferential and 0.49–0.5 in radial direction, and both of them are independent of speed and load. The research verifies that the proposed model is an effective tool for studying lubrication performance and optimizing of RWTBs.</p
Robust global sliding model control for water-hull-propulsion unit interaction systems - part 2: model validation
Full text linkUnexpected severe hull deformation caused by wave loads poses alignment problem to the propulsion shaft line in large scale ships, which would significantly influence the dynamical performance of the marine propulsion system. How to suppress negative disturbance imposed by the interaction between water-hull-propulsion and ensure the normal operation of the marine propulsion system is a challenging task. To address this issue, a new global sliding model control (GSMC) for marine water-hull-propulsion unit systems is proposed and investigated to obtain more accurate control performance in a series of researches. In Part 1 the GSMC controller has been developed and the bounded nonlinear model uncertainties have been derived based on the experiments and sea trial. In this work the upper boundary of 1,85 % was introduced into the GSMC controller to derive the total control law realising the robust control of the marine propulsion system. Numerical simulations based on the real bulk carrier parameters show a high effectiveness of the GSMC for speed tracking, compared with the traditional sliding model controller and Proportional Integral Derivative (PID) controller. By the proposed and investigated control system in this paper may be developed a simple practical-effective robust control strategy for marine propulsion systems subject to some complex unknown uncertainties through further investigations, validations and modification
Robust global sliding model control for water-hull-propulsion unit interaction systems - part 1: system boundary identification
Full text linkUnexpected severe hull deformation caused by the wave loads would significantly influence the dynamical behaviours of the propulsion system in large scale ships, resulting in degradation of the ship control performance. A new global sliding model control (GSMC) for marine water-hull-propulsion unit systems is proposed to obtain more accurate control performance in this paper. The GSMC was firstly employed to establish the marine propulsion control model with nonlinear uncertainties. In the GSMC model, the saturation function method is applied to eliminate chattering on the sliding surface. Then the Lyapunov stability criterion is adopted to confirm the stability of the control system. Following, for the first time, the boundary problem of the nonlinear model uncertainties were investigated quantitatively. The bounded nonlinear model uncertainties required in the proposed GSMC model, involving engine torque loss / variations, power transfer for various load conditions and shaft rotational speeds, were derived based on the experiments carried out on a marine shaft-line test-bed of the integrated propulsion system as well as a sea trial implemented for a running bulk carrier. An upper boundary of 1,85 % for the model uncertainty has been obtained, which would be introduced into the GSMC for the integrated marine propulsion system to derive the total control law realising the robust control of the syste
Comparison of measured and calculated water film thickness of a water-lubricated elastically supported tilting pad thrust bearing
No full textA xenon induced fluorescence technique is used to measure the water film thickness of a rubber-supported water-lubricated tilting pad thrust bearing (RWTB). Film thickness maps are obtained over a range of speeds and loads. Based on a Thermo-Elasto-Hydrodynamic lubrication model, the calculated film thickness is compared with the measured one. The measurement shows that the lubrication regime of the RWTB can be observed and it can form a convergent wedge of lubricant. The calculated results are on par with the experimental results at low speed condition (200 r·min-1). Generally, the calculated film thickness is larger and the discrepancy between them increases respecting to the speed. The RWTB is in the hydrodynamic lubrication regime when the speed is over 200 r·min-1 and the load is less than 0.25 MPa. The comparison between the measurements and calculations verifies that the fluorescence technique can be used to measure the film thickness of water-lubricated thrust bearings
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