Shaft Line Research Articles

Machine learning performance comparison for main propulsive shafting systems alignment

The ship shaft alignment is crucial to achieve a high-performance propulsion system. This alignment is carried out, still in drydock, by adjusting the bearings' offsets. However, there are numerous available combinations sets of vertical offsets which results in good alignment final condition. Defining an optimum set of vertical displacements is costing shipyards a valuable time. Therefore, this work proposes the use of machine learning algorithms to predict if a given set of offsets, following the mandatory rules in force, should be implemented or not. In this manner, this paper presents a case study where a finite element model of an Anchor Handling Tug Supply (AHTS) vessel’ shaft line was assembled in order to obtain the bearings reactions, shaft line deflections, shear forces, bending moments and, finally, the influence coefficients matrix (ICM). Those data were used to feed machine learning (ML) models based on four different algorithms, namely, K-Nearest-Neighbors, Extremely Randomized Trees, Random Forest and Gradient Boosting in order to solve multiclass classification problems concerning the offset's set to be applied in the alignment of the shaft line. Results showed that the Gradient Boosting and Random Forest algorithms presented the best results, achieving up to 98.1% of precision in one of the 36 scenarios tested, and an average precision above 96.0%. Such results corroborated with the authors' proposal to implement ML techniques as a way to speed up the currently very time-consuming shaft alignment process.

METHODS, MEANS AND TECHNOLOGY FOR IMPROVING THE EFFICIENCY OF VIBRATION DIAGNOSTICS OF GAS PUMPING UNITS

Computational and experimental methods, tools and technology for monitoring the technical condition of gas pumping units according to the parameters of torsional vibrations are proposed. To identify risk-sensitive parts of gas pumping units, energy forms of the machine's own torsional vibrations of the shaft line are used. The results obtained made it possible to reduce operating costs.

Gauging and Diagnostics of Turbine-Unit Shaft Lines by Torsional Oscillations

Gauging and Diagnostics of Turbine-Unit Shaft Lines by Torsional Oscillations

A prototype recuperated supercritical co2 cycle: Part-load and dynamic assessment

High efficiency, flexibility and competitive capital costs make supercritical CO2 (sCO2) systems a promising technology for renewable power generation in a low carbon energy scenario. Recently, innovative supercritical systems have been studied in the literature and proposed by DOE-NETL (STEP project) and by a few projects in the EU Horizon 2020 (H2020) program aiming to demonstrate supercritical CO2 Brayton power plants, promising superior techno-economic features than steam cycles particularly at high temperatures.The H2020 SOLARSCO2OL project, which started in 2020, is building the first European MW-scale sCO2 demonstration plant and has been specifically tailored for Concentrating Solar Power (CSP) applications. After a detailed explanation of the modelling approach for steady and unsteady cycle simulations, this paper presents the off-design and dynamic analysis of such plant layout, which is based on a simply recuperated sCO2 cycle. The entire system model has been developed in TRANSEO environment. The part-load analysis ranged from 50% of nominal up to a 105% peak load, discussing the impact on compressor and turbine operating conditions. Full operational envelop has been determined considering cycle main constraints, such as maximum turbine inlet temperature and minimum pressure at compressor inlet.The off-design performance analysis highlights the most relevant relationships among the main part-load regulating parameters, namely molten salt mass flow rate, CO2 mass flow rate, total CO2 mass in the loop, and shaft line speed. The results show specific features of different control approaches, discussing the pros and cons of each solution, considering also its upscale towards commercial applications. In particular, the analysis shows that at 51% of load an efficiency decrease of 20% is expected. Finally, the dynamic characterization of the closed loop shows the relatively fast responsiveness of the plant to compressor speed variations, causing quick changes in CO2 mass flow rate, together with longer time scale phenomena related to the plant heat exchangers. In this respect, sCO2 plants demonstrate to have the potential to provide primary reserve for the electrical grid, as far as thermal stresses on main plant components are kept under acceptable limits.

Tunneling construction technology of shafts and cross-passages under strictly controlling deformation of the existing railway

Underground construction will have more or less adverse effects on adjacent existing buildings with more and more existing buildings above ground. However, this situation has only been reported by a small number of researchers. In view of this, this article takes the existing airport line shaft and horizontal passage project in the western suburb of Beijing Metro Line 12 as the background to study the impact of the construction of subway station and shaft passage on the adjacent existing railway. Based on the above project reality, under the action of pavement load, the effects of different parameters (the distance between the surface measuring point and the middle line of the transverse passage and the substep of construction loading sup step) on the surface settlement and track deformation of the shaft and cross-passage through the existing railway are studied by numerical analysis method. The calculation results show that the construction method of shaft and cross passage is reasonable. The comprehensive reinforcement measures of subgrade, rail and hole are effective, effectively controlling the deformation of subgrade and rail within the standard value (surface settlement ≤60 mm, rail deformation ≤6 mm). In addition, the numerical simulation data can better represent the actual situation as a whole.

COMPARATIVE STUDY ON THE DISPLACEMENTS, EQUIVALENT ELASTIC STRAIN AND EQUIVALENT STRESS OF THE PROPELLER SHAFT AT DIFFERENT OPERATING MODES

This study presents the sizing calculation and the FEM analysis of the propeller shaft for three different operating modes. The propeller shaft has the role of supporting the engine and transmitting its rotating motion and is the most requested element in the structure of the shaft line. In scenario 1, a "fixed support" type constraint is applied at one end and the maximum torque given by the motor at the other end is applied to lock the propeller. Than to simulate scenario 2, apply the maximum thrust force to the propeller at one end, and the "fixed support" constraint will be inserted at the end of the engine. And the 3 th scenario was the operating of propulsion system in normal mode. Comparing the results from the simulation of the three scenarios, it is observed that the maximum values recorded for displacement, equivalent elastic strain and equivalent stresses were recorded at the engine operation under normal conditions. In conclusion, although the scenarios were a bit exaggerated, the propeller shaft withstood the efforts, falling within the limit of elasticity. This demonstrates that the calculation method of propeller shafts is correct, and safe, as long as their size is not oversized.

Localized Damage Identification in the Last Stage Low-Pressure Steam Turbine Blade Using Dynamic Parameter Measurements

Abstract Steam turbine blades are the important components in power system shaft lines subjected to severe temperatures, leading to low/high cycle fatigue failures. The transient conditions occurring during startup and shutdown events generate alternative stresses causing the fracture at the blade roots. The present work deals with the effect of localized damage on the vibration characteristics and damage identification study in the last stage low-pressure (LP) steam turbine blade. Initially, free vibration studies and transient analysis of the last row LP blade section are conducted using the finite element model. A crack near the root region is modeled by a torsional spring, whose stiffness is expressed in terms of crack depth ratio. Effects of crack depth ratio and location near the roots on the natural frequencies and transient response amplitudes are studied in detail. The relationship between the damage parameters and blade frequencies is established through the backpropagation neural network model.

Parametric method for the assessment of fatigue damage for marine shaft lines

An original parametric method is introduced for the assessment of the fatigue life of marine shaft lines. The particularity of the method lies in the fact it introduces a relevant load modelling around a limited number of parameters specific to marine shaft lines while depicting the loading complexity (multiaxiality, mean stress effect, non-proportionality of the loading path). The method is designed to allow for assessments, in both in-use and pre-design phase shafts, towards a particular fatigue damage mode. The observations made in this study show two damage modes. On one hand, a damage mode issued from multiaxial cycles and associated with ship maneuvers, corresponding to HCF regime. On the other hand, there is a damage mode in the VHCF regime resulting from bending stress cycles due to the structure rotary bending.

Preliminary Design of a Mini Gas Turbine via 1D Methodology

To address the increasing interest towards more environmentally friendly naval transportation and the introduction of IMO2020 restrictions on pollutant emissions onboard ships, the present work details the preliminary design of a mini gas turbine engine, i.e., a gas turbine engine with an output power up to 5 MW, for onboard energy generation. In comparison to conventional propulsion systems, gas turbine units benefit from known compactness, which can be further enhanced by employing single-stage uncooled radial machines, according to similar works in the field. As such, the present paper aims to set up a complete procedure that allows a reliable and fast (i.e., requiring a limited computational effort) preliminary design of one-stage centrifugal compressors and radial turbines operating at a high pressure ratio via the use of classical one-dimensional theory. The aerodynamic design outputs in terms of forces and torques are then used to perform a preliminary mechanical design of the shaft by means of a one-dimensional finite element model with commercial software to estimate the corresponding shaft line stress. Despite some necessary geometrical and modeling simplification of the design problem, which results in the unavailability of detailed information on individual components, the employed procedure nevertheless allows a comprehensive overview of the possibilities in terms of maximum machine performance achievable at an early design stage with the associated limited computational requirements. The design procedure and the geometry achieved for the application are presented along with aerodynamic and structural results.

Актуальные вопросы изучения реверса движителей

Object and purpose of research. This paper discusses crash-stop of ship propellers. The puspose of the study was to investigate a number of relevant challenges in this process, i.e. to refine the methods of crash-stop distance calculation, to update the scenarios for which crash-stop strength of propeller blades has to be verified, as well as to determine operational parameters and algorithms for automatic control systems of electric power plants in crash-stop conditions. Subject matter and methods. The study was based on the results of quasi-crash-stop model tests, as well as on previous publications about crash-stop maneuvers of ships and operations of their propulsion systems in these conditions. Main results. To obtain more accurate crash-stop distance estimates, it was suggested to use an alternative, bollard-pull system of propeller-hull interaction coefficients for crash-stop conditions. It was also suggested to perform crash-stop strength check of propellers not only for the scenarios with maximum hydrodynamic load, but also for the moment of propeller rotation direction reversal because it might be accompanied by considerable inertial loads. It is shown that model testing is not helpful in determination of operational parameters and automatic control system algorithms for electric power plants because shaft lines cannot be simulated correctly. These parameters can be obtained through calculations, but this will require more refined expressions for shaft line friction moments. Conclusion. The actual problems of ship reverse propulsion theory is presented in the paper. The possible approaches to their solution are proposed.

Rare cause of intraoperative endotracheal cuff deflation.

Dear Editor, Manufacturing defects in endotracheal tubes (ETTs) can lead to cuff leaks, inadequate ventilation, hypoxemia, and risk of aspiration.[1] These defects may go unnoticed during preuse check of tube before intubating[2] and may lead to difficulty in tube exchange during head and neck surgeries or prone positioning. We report a case of trivial leak that went unnoticed until the intraoperative phase with a source of leak being only established after tube exchange. A 39-year-old female (43 kg), undergoing gastric pull-up surgery, was intubated with a 7.5-mm ID cuffed ETT (Portex®, Smiths Medical, Minneapolis, MN, USA) and a pilot balloon was filled with 4 ml of air at which there was no cuff leak. After around 30 min, a leak was visible on the ventilator with 150 ml of difference between the inspired and expired air. On inspection of the pilot balloon, it was found to be deflated. It was again filled with air resulting in correction of leak. As neck incision had been made with the face covered under the drapes with no leak, we decided to continue with the surgery. Thereafter, every 45–60 min, the tube developed a leak that was managed by filling air repeatedly. A syringe was attached at the valve to rule out valve incompetency, but it did not prevent leak and tube was exchanged. The surgery lasted for 5 h and the patient was extubated uneventfully. The tube was dipped in water and cuff did not show any bubbling. Then, the pilot balloon and valve were immersed in water, which showed slight bubbling at the junction of pilot balloon and valve assembly [Figure 1]. The leak was mild and clearly appreciable only when the tube cuff was pressurized by hand. These types of leaks were found in other cases in the same operating room complex as well implying a faulty manufacturing defect in the batch of ETT s.Figure 1: Site of leak in endotracheal tube. (a) Immersion in water showed bubbling. (b) Application of water showed bubble at junction of pilot balloon and one-way valveManufacturing defects in tube can lead to leaks present in the valve, pilot balloon, junction of cuff inflation line and ETT shaft, lumen of tube and the cuff.[3,4] Minute leaks may not be visible and missed during inspection of tube before intubating. These leaks can be hazardous in cases of head and neck surgery and difficult airway. Various methods of minimizing the leak have been described and include throat packing, injecting the cuff inflation line with lignocaine, continuous inflation, and blocking the one-way valve (in case of valve incompetency).[5] These methods are not foolproof and act as temporary measures. If a leak is detected, a plan must be formulated depending upon the surgery, airway, and amount of leak. Manufacturing defects must be reported to the manufacturer and stores department. The tubes of same batch must be inspected thoroughly as they may have the same defect and leak. If a trivial leak is present, it should always be looked for after extubating and immersing the tube in water. Intense vigilance toward monitoring difference in inspired and expired tidal volume can aid in detection of such minuscule defects. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

On the auto-oscillation effect of Kaplan rotors during load rejection

High vibrations due to auto-oscillation effects can occur at power units with Kaplan type runner during load rejection. These vibrations may be present in the turbine braking mode when the wicket gates are almost closed, and the rotating runner pushes the water towards the draft tube resulting in higher pressure below the runner blades. The upward leakage flow between runner blades and discharge ring is suspected to cause the vibration phenomenon.Within this contribution, a fluid-structure-interaction (FSI) technique is applied to identify the mechanism of self-excitation. The investigation is carried out on a disk that represents the simplified geometry of a Kaplan runner. Computational fluid dynamics (CFD) simulations are used in order to obtain parameters in terms of stiffness, damping and inertia of the fluid to be applied in the following shaft line analysis. Damped modal analyses of the shaft line allow for evaluation of the stability of natural frequencies and corresponding mode shapes of the shaft line. A resulting negative damping indicates the occurrence of auto-oscillation behavior of the shaft line. For the operating condition under investigation, mode shapes with negative damping are obtained with this approach and a dynamic bending moment on the runner due to lateral movement in combination with a tilting at the runner in these mode shapes is identified as source of instability.Based on these findings, an analytical approach for modeling the relevant effect is derived and compared to CFD result as well as results from acoustic finite element modelling. Finally, conclusions for avoidance of self-excited vibrations at Kaplan runners are proposed.

Development and experimental implementation of a biaxial transducer to measure radial loads on a rotor shaft

During realistic functioning conditions, rotating machinery can develop radial loads that are transmitted to the supports of the shaft (bearings) reducing their fatigue life and structural integrity. In the particular case of turbines and propellers, in-plane loads are generated due to non-uniformity of the inflow field and, beside contributing to the onset of structural issues, affect the dynamic response of airplanes and ships as well. The measure of the radial force components provide a considerable information to understand, evaluate and mitigate those effects during the life-cycle of the shaft line and for the improvement of performances. In this work, the development of a new bi-axial force transducer is described. The final design is based on a theoretical approach considering a simplified portal frame model, supported by FE analysis. This device fulfills the need to quantify radial forces acting on a rotating shaft, with low invasive design and very simple setup. The reliability of the device is demonstrated in the context of ship propulsion. It has been mounted on a scaled model of a ship, during self propelled free running maneuvering tests, providing remarkable hydrodynamic results useful to the quantification of poorly documented loads and the comprehension of the interaction between the propeller and the ship wake.

Анализ работоспособности силиконовых демпферов крутильных колебаний судовых двигателей внутреннего сгорания на основе результатов испытательного центра Marine Technology Service

The article presents the analysis results of changes in the operability of silicone dampers of torsional vibrations of marine diesel engines on the basis of practical measurements carried out by the Testing Center Marine Technology Service under the Astrakhan State Technical University (TC MTS). TC MTS is accredited by the Russian classification society - the Russian Maritime Register of Shipping (RMRS) in the field of calculation and measurement of torsional vibrations. During its functioning (2001 – to date) the TC MTS has conducted torsiographing procedures of the machine-propulsion systems (MPS) of more than 200 vessels. The large amount of data obtained makes it possible to assess the dynamics of changes in the parameters of torsional vibrations, including amplitude and frequency, according to the results of periodic torsiographing the ship MPS. A change in the technical condition of the torsional vibration damper (a decrease in the efficiency of its operation) and the lack of its constant monitoring lead to the increasing stresses in the ship shaft line and, as a result, to a growing risk of its breakdown, which confirms the urgency of the study. There are given the images as real examples of ship operation failure: Aratere ship shaft fracture, damper mass wedging due to silicone fluid leakage, silicone fluid viscosity increasing to suspension state due to wear products, wear of silicone damper flyweight surfaces, silicone damper body wear. The Hasse & Wrede damper cap fastening with bolts is illustrated.

Study on the Tooth Profile Parameters Design Method of Crown Gear Coupling for Helicopter Tail Folding Device

Shipboard helicopter folding technology can increase the number of helicopters parked on board aircraft carriers. Crown gear coupling is the trend in helicopter tail rotor folding technology due to its ability to automatically and quickly engage and disengage helicopter tail rotors. This paper presents a method for the design of tooth parameters for crown gear coupling for folding devices. The model of the relationship between tooth shape parameters and angular displacement of the crown gear coupling and the model of the relationship between angular displacement and shaft line angle of the crown gear coupling were established, respectively, and the basic parameters of tooth shape and modified parameters of the crown gear coupling were designed. The correctness of the design method of the tooth parameters of the crown gear coupling for the folding device was also verified through motion simulation. The results of the study provide a theoretical basis for the design and optimization of crown gear couplings for folding devices.

Динамическая прочность компактных резонирующих вибропоглотителей, применяемых в судовых валопроводных системах

Object and purpose of research. The object of the study is compact lamellar resonating vibration absorbers (RVA). The purpose of the study is to develop a method for calculation of the dynamic strength of RVA, designed to assess the possibility of their use in ship shafting systems. Materials and methods. The initial data and material for the study were the design of a plate-shaped resonating vibration absorber and the amplitude value of the variable components of the forces accompanying the bending vibration of the shaft line. Simplified methods for calculating the dynamics and strength of plates during their deformation in the elastic region are applied. Main results. Developed method for calculation of dynamic strength of RVA. Relations are obtained that make it possible to choose the geometric dimensions of the RVA that ensure its dynamic strength and vibration damping efficiency. Conclusion. The possibility of ensuring the vibration resistance of the RVA designed to dampen the vibration of the shaft span is confirmed with the initial data accepted in the problem.

REMOVED: Hysteresis and torsional-lateral vibration coupling in a complex shaft line supported by hydrodyanamic journal bearings

This article has been removed: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been removed at the request of the authors because of incomplete authorization for the inclusion of proprietary information in the article. The authors apologize for any inconvenience this may cause.

Voltage balancing control of a series-resonant DAB converter with a virtual line shaft

Voltage balancing control of a series-resonant DAB converter with a virtual line shaft

Опыт виброналадки турбогенераторов К-1200-6.8/50 + Т3В-1200-2АУЗ первого и второго энергоблоков Нововоронежской АЭС

The paper briefly describes the K-1200-6.8/50 turbine, a component of the innovative VVER-1200 pressurised water reactor unit. The main advantage of this turbine is that instead of implementing cooling by filling the generator interior with hydrogen it uses full water cooling, which prevents explosion or combustion. Direct cooling of the stator winding works as follows: distillate circulating in a closed circuit flows through hollow stainless steel water-cooling components laid within the stator grooves. The number of hollow water-cooling elements in the stator grooves is dictated by a desire to ensure sufficient cooling efficiency while minimising electromagnetic losses. The paper considers the features of vibration manifested and vibration control of the turbo generator in terms of the generator-exciter assembly, as, when seeking to minimise time spent on mounting and adjusting loads while performing vibration correction via balancing, the most readily available planes are those located on the rotors of the generator and exciter. We investigated the possibility to reduce axial components of oscillations occurring in supports No. 10 and 11 by balancing the shaft line rotors in their own bearings at the operating frequency.

A Measurement System to Monitor Propulsion Performance and Ice-Induced Shaftline Dynamic Response of Icebreakers

Polar navigation entails challenges that affect the continuation of ship operations in severe ice conditions. Due to ice-propeller interaction, propulsion shafting segments are often at a high risk of failure. Efficient methods for shaft line design are hence needed to ensure the safety of ice-going vessels and propulsion reliability. To this end, full-scale measurements have proven essential to support the development of ship-design tools and updated safety regulations for ice-going vessels. This paper presents a unique integrated measurement system that employs measuring equipment to monitor Polar-Class vessel performance and shaft line dynamics during ice navigation. The system was installed on board the Canadian Coast Guard (CCG) icebreaker Henry Larsen. This experimental concept aims to monitor the shaft’s torque and thrust fluctuations during ice navigation to obtain information about the ship’s propulsion efficiency. In the paper, we describe the arrangement of the measurement system and the components it features. Finally, we present preliminary datasets acquired during two icebreaking expeditions. This work is framed into a broader research project, which includes the long-term objective to determine a correlation between sea ice conditions and the dynamic response of shaft lines.