This doctoral thesis represents a set of new ideas, methods and research re-sults related to improving the efficiency of functioning of ship power plants (SPP) of combined propulsion complexes (CPC). The main motivation for these studies...
moreThis doctoral thesis represents a set of new ideas, methods and research re-sults related to improving the efficiency of functioning of ship power plants (SPP) of combined propulsion complexes (CPC). The main motivation for these studies is the existing current practice requests for the operation of the SPP CPC, such as: ensuring minimization of irreversible losses in the transmission of capac-ities from the SPP to the engines of the CPC; the need to improve the monitoring of the transfer of capacities in the SPP CPC with dynamic principles of retaining the vessel; increasing the operational reliability and strength of the SPP CPC; creation of new and improvement of existing decision support systems (DSS) during operation, research and design of the SPP CPC.
Based on the analysis of the existing state of the development of the SPP CPC, the following unresolved problems were found on the lines of propellers, in power systems of motors for thrusters and power distribution systems, which can be characterized as follows: reduction of propeller thrust and torque due to water flow perpendicular to the axis of the propeller caused by the flow from the vessel speed or flows from other engines with force in the direction of inflow due to the deflection of the propeller flow. This is often called a cross-combination of resistances; the presence of cavitation for heavy loads on the propellers leads to a reduction in pressure on the blade of the propeller and can occur during a small immersion of the propeller due to the movement of the ship across the waves; sudden drops of thrust and torque with the effect of hysteresis due to the large amplitude of the ship's motion perpendicular to the surface of the water; simulta-neous reduction of thrust and change of thrust direction due to interaction of the flow from the thruster to the hull (Coanda effect); loss of the thrust and reduction of thrust caused by the action of the propellant flow from one motor to adjacent motors; limitation of the increase in torque by the inductance of the motor with the prevention of damage to the mechanical part of the electric drive; limitation of the maximum power of the thruster, is taken into account when determining the overload capacity of the electric motor and frequency converter (FC); the absence of a control strategy for the thruster FC based on variable speed governors which provide the transition of consumers, working on a constant power hyper-bola, to the torque or speed of rotation control mode; the need for Dynamic Posi-tioning (DP) systems to meet the quality management requirements encountered during the operational phase; unification of Power Management System (PMS) in a combination of functions in relation to others similar; the independence of PMS systems components from each other to the level of sensors; not only the reduc-tion in capacity based on the total design load, but also the load of an individual medium speed diesel generator (MSDG); compliance of the system with condi-tions increasing the load in terms of sufficiency to ensure normal operation in re-lation to any abnormal mode and non-overloading the ship electric power system (SEPS) in general.
The above problems directly led to the formulation of the main complex re-search task: the development of a DSS for the design, research and improvement of SPP CPC, consisting of three main tasks: the development of a monitoring system for degradation effects on the lines of propulsion flows of motors with the identification of relevant markers, the development of the strategy for all-mode power controllers, torque controllers and variable speed governors by the electric motors of the CPC thrusters and the development of the methodology for con-structing multi-criteria control strategies over power distribution of the SPP CPC.
As a result of solving the main and auxiliary tasks, the following scientific positions were obtained: improvement of the method of computational hydrody-namics is provided by using the distribution of the sought-for intensities of the degradation effects from the interaction of the propeller flows among themselves and the CPC body due to the use of piezoelectric sensors on the shaft lines of az-imuth thruster. Compensation of degradation effects is achieved by calculation of power flows from azimuth thrusters in the form of a power drive disc, which al-lows identifying turbulent regions with relative vortex viscosity coefficients μt/μw. Calculation of the components of the x-velocities at the intersection of the propel-ler flow along the axis of rotation with dimensions in units of the diameter of the DP propeller makes it possible to realize the method of surface-oriented averag-ing of the Reynolds-Navier-Stokes equation for mass transfer at the interface; limitations on power and torque on the shaft lines of the SPP CPC thruster of dynamically positioning vessels are provided by redistribution of the thrusts be-tween the thrusters or the reduction of the maximum load as part of the algo-rithm for distributing the thrust of the DP system due to the application of the strategy of full range speed governors in relation to operating conditions; for the first time, a three-level multi-criteria strategy for managing the distribution of en-ergy in the hybrid SPP CPC was developed by integrating the classical strategy of power distribution management with a strategy of control over the state of the MSDG and the degree of charge of the energy storage system alternative generat-ing element. The developed strategy differs from existing by higher speed detec-tion of risk of de-energization of ship electric power system, greater reliability and accuracy in determining the need for load reduction and the thruster speed of rotation fully integrated with variable speed governors and power supply system; for the first time, the DSS was created to study the ways of automating and com-puterizing the design and operation processes of the SPP CPC, which being based on theoretical, design and experimental methods, has enabled the introduction of a comprehensive substantiation, verification and self-testing of the developed components of the methodological and mathematical apparatus; for the first time, a physical model of a multifunctional CPC with a variable structure was created, which, in synergy with the solution of the problem of DSS development, allows iterative analysis of the structures of the SPP CPC with minimal initial data; the law of pulsations of thrusts on the lines of propeller shafts is established, which occur under conditions of interaction of several thrusters with each other and with the CPC body. In the process of studying the version of the configuration of a CPC with contra-rotating propellers (CRP) it was established that: 1) the rota-tion of the thruster body leads to the appearance of characteristic recirculation zones and changes in the velocity fields in its disk and differs by an increased de-gree of flow heterogeneity; 2) the characteristics of the thrust and the torque of the thruster differ significantly depending on the direction of rotation; 3) the pul-sation of the propeller thrust of the azimuth thruster sharply increases with its rotation, and the most significant growth in pulsations occurs at the resonant fre-quencies of the interaction of the propeller flow of the azimuth thruster and the stationary one; the theory of non-stationary interaction of several propellers with each other has been developed, which made it possible to establish for the first time the following facts: 1) rotation of the thruster leads to an increase in the ax-ial and tangential components of the thrusts and torques; 2) the operation of the azimuth thruster at large angles with respect to the stationary propeller results in the appearance of significant loads on the thruster stock, which can be determi-native in terms of the strength of the structural components of the thruster, the presence of deformations of which has been experimentally established and con-firmed by calculation. Also, for the first time, the dependencies of the thrusts and torques of the azimuth thruster were determined as a result of the interaction of the propeller flow with the hull and the stock due to the occurrence of degrada-tion effects; for the first time, a simplified semi-empirical method for iterative progressively regressive parameterization of the SPP CPC was developed in off-design operation modes, which generalizes the previously relationship, which have been derived for thrusts and torques of co-axial CPP s in a homogeneous flow with ratios known from the theory of turbomachines for the case of interac-tion between the stationary propeller and the azimuth thruster. On the basis of this technique, a calculation method has been developed that makes it possible to accurately estimate the value of thrusts and torques of motors for azimuth thrust-ers in a wide range of operating conditions and the angles of flow deflection due to the influence of degradation effects that are substantially different from the de-sign ones. The necessity to take into account the influence of degradation effects on the lines of propeller shafts in the CRP Azipod® concept has been proved
