Alignment optimization of 3D model of propulsion shaft system

Three dimensions models of propulsion shafts are presented in this work. A shaft alignment optimization is computed for a crankshaft, intermediate shaft and propeller shaft. “Design Study” sensors are used to report the best solutions of bearing reactions according to the vertical displacement. Shear forces and bending moments are listed for the flanges. The finite element analysis investigated a slope and deflection of the propulsion shaft system. Pictures of stress and displacement of the shafts, bolts and flanges are pointed in the paper. Stress concentrations and a factor of safety is calculated in the 3D dimension.


Introduction
Nowadays, the shipbuilding tendency is followed by increasing the vessel cargo capacity, which is associated to the rise of main drive power. The drive shafts then become increasingly sensitive to the disturbances affecting to the bearing's vertical displacement. However, the shaft alignment procedures remain an important problem requiring accurate analyzes [1,2]. The positive values of supporting reactions in the sliding bearings is the main criteria of shaft alignment. A software method is used to optimize the elastic shafts line [3] by monitoring and compliance of the shaft alignment criteria. This paper examines the loading of propulsion shaft system of a bulk carrier 21100 DWT. An assemble model is created of the shafts and a methodology of alignment optimization is developed. In figure 1 is presented: The correct static alignment of shafts is developed from practice to get the smooth dynamic operations of system [4,5]. This leads to the reduction of excessive vibration of line, as well as the transmission of gearbox noise. • radial, axial and angular shaft flanges positions; • engine base deflection and its bending; • vessel hull deformation.
The shaft alignment is satisfactory if the above mentioned parameters can be controlled within certain limits for all operating conditions of the vessel (fully loaded or unloaded vessel, lowered or into open water, temperature changes affecting shafts, propulsion on maximum power). The shaft alignment procedure begins once the conditions are met: • vessel's construction temperature is stabled (usually the alignment is done in the early morning); • massive parts such as superstructure, main engine, etc. are installed; • all elements of the hull construction and equipment are presented; • stern blocks are fully welded; • leak tests are completed.
It is preferable for the shaft alignment procedures to start in a dry dock (bearing positioning, slope, etc.) and to provide a sufficient information for the production personnel. The alignment procedures are extended and require many software operations, mathematical calculations and theoretical analyzes. In this regard, the present paper is focused on the study and optimization of some parameters described above. The extreme cases that can lead to damage and failure of the propulsion system of vessel are analyzed.     The 3D models of shafts are assembled into one model and links between them are created to meet the real conditions for joining the shafts figure 5.

Configure simulation mode
In the static simulation of shafts, the following settings must be made:

Software shaft alignment of bulk carrier propulsion system
For most vessels, a vertical displacement of shaft's bearings by 10% of a millimeter can lead to significant changes in the support reactions. Therefore, the process of shaft alignment takes a long time in order to determine satisfactory set of parameters that meet all criteria for the shaft alignment. The main parameter to be defined is the vertical location of FWD stern tube bearing and intermediate bearing. In addition, it must be verified that the alignment is feasible for the specific shaft geometry, material properties, installation restrictions and other requirements related to the drive shaft and the impact of surrounding systems [10].
The shaft alignment problem is different and has an infinite number of bearing vertical displacements satisfying the alignment requirements. For a optimization purpose is provided a set of acceptable solutions meeting the constraints imposed, the alignment parameters and the relevant criteria [6]. Numerous solutions are needed to engineers choose of desired alignment.
Three parameters sets are introduced for the shaft alignment optimization application: variables, constraints, and goals. Report date sensors are created for limitations and purposes of the optimization.

Shaft alignment optimization results
The simulation is made of 38 displacement scenarios. The vertical displacement is set to the bearing №2 (2.1 mm ÷ 2.6 mm) and the bearing №4 (1.3 mm ÷ 1.8) for duration 37 minutes and data 10.27 GB. Data is extracted of the scenario №25 with vertical displacement 2.1 mm of bearing №2 and vertical displacement 1.7 mm of bearing №4. The slope of bearing №1 -0.9516*10 -3 rad.
The following figures are presented to show deformation and stress in the individual shaft sections as follows:

Conclusion
А methodology has been developed for a software alignment optimization of a propulsion shaft system. The method advantage is the deformations and stress calculation of loaded 3D shaft models, associated to bearing supports displacement. Load data is presented of the additional elements, such as bolt connections. Stress concentrators are pictured of the crankshaft. The method can be used to simulate the loading of additional elements, such as stern tube elements, seals, caps, technological holes, thread etc., in parallel with the shaft alignment optimization. It is possible to optimize the model geometry, to monitor the working capacity criterion, to set temperature differences and many others.
Some of the scenario №25 values are written in table 1.