Propulsion Losses Research Articles

Assessing the influence of sudden propulsion loss on a ship's manoeuvrability in various wave heights utilizing CFD

The prevalence of ship propulsion failure remains a significant concern at sea, posing a recurring risk to maritime safety. As a ship's ability to manoeuvre heavily relies on its propulsive power generated by a rotating propeller, any loss in propulsion can lead to potential hazards such as collisions, contacts, or groundings, particularly in a real seaway. Therefore, accurately assessing the manoeuvring capabilities of ships experiencing propulsion failure is crucial for ensuring navigation safety. This paper aims to examine the impacts of sudden propulsion loss on the manoeuvring capability of the KCS (KRISO Container Ship) model under different wave heights, utilizing URANS (Unsteady Reynolds-Averaged Navier-Stokes) simulations. Through a series of case studies comparing ship performances under normal conditions versus propulsion loss scenarios, particularly during turning circle manoeuvres in different wave height conditions, the study sheds light on the significant impact of propulsion failure on ship manoeuvrability. When examining the ship's turning performance under identical wave heights, it became evident that the ship's advance increased in instances of propulsion loss compared to normal operational conditions. Specifically, at a wave height of 2.4 m, the ship's advance increased by 23% during propulsion failure. Similarly, at wave heights of 3.6 m, 4.8 m, and 6.0 m, the increases were 19%, 17%, and 12%, respectively. In calm water, there was a 24% increase in advance. Notably, at a wave height of 7.2 m, the ship failed to complete a 90° turn, making it impossible to determine the ship's advance under these conditions. The findings underscore the critical importance of sufficient propulsion power for safe vessel operation. This research not only provides valuable insights for navigators into ship manoeuvring under propulsion failure but also contributes to the development of contingency measures, especially pertinent for autonomous vehicles encountering similar propulsion challenges.

Inhibited swimming capacity of fish entrained in wake vortices behind a semi-cylinder

The loss of fish swimming capacity induced by those energetic vortical structures is detrimental, and limited research on the mechanism of fish entrainment in the vortex has been reported. The present study investigated the entrainment of a fish in vortices generated in wake of a semi-cylinder. The swimming fish was modeled using an undulatory NACA0012 airfoil behind semi-cylinders with a diameter D from 0.1 to 2.4 times the fish body length (L). It was found that the fish couldn't get higher propulsion from the low momentum flow for D > 0.8L. The wake of the fish was distorted by the shedding vortices and trailing-edge vortices (TEVs) arose at fishtail. The length- and time-scale of TEVs were positive correlated with these of oncoming co-directional vortices. The uncontrollable hydrodynamics induced by TEVs could elucidate the disruption of fish stability by surrounding vortices, manifested as a loss of propulsion, the generation of a unidirectional torque, and increased power consumption. The fish head gradually got energy from the turbulent flow of oncoming vortices, but fails to compensate adverse effects of the TEVs. The recovery of swimming capacity occurred only in the less disturbed flow between the wake vortices.

Signal pre-processing techniques for fault signature enhancement in a bearing health monitoring system used in the automotive industry

Traditional internal combustion engine vehicles have low transmission bearing failure rates in their lifespans. However, the prolonged lifespan of electric and autonomous vehicles can surpass the reliable life of bearing designs, which poses a risk of bearing failure and loss of propulsion. Compared to replacing bearings on a fixed schedule to ensure reliability, a bearing health monitoring system is a more cost-effective solution. Despite extensive research on bearing condition monitoring, implementing well-known methods such as vibration spectrum analysis in vehicles can be challenging due to vibrations from vehicle components and the road. This paper explores and compares the effect of various pre-processing techniques on the spectrum of a faulty bearing with various fault levels. To achieve this objective, faults with the width size of 0.1 mm (mild), 0.5 mm (moderate) and 2 mm (severe) were injected into the inner race of a ball bearing. A bench setup was then used to capture the vibrations of multiple vehicle components including the faulty ball bearing under various speed/ load conditions. Phase domain transform, envelope and Fourier transform were used as the core signal processing steps, and advanced signal processing methods for removing discrete frequencies from other components and enhancing the fault signature were explored. 4 health indicators were then developed from the vibration spectrum of the vibration signals and calculated for the captured data. Next, for each fault level, the area under Receiver operating characteristic (ROC) curve was calculated and used as a metric to compare the performance of our health monitoring system for classification of faulty and healthy bearings. For our best health indicator, the results show that applying minimum entropy deconvolution, and spectral kurtosis-based band pass filtering increases the ROC area from 0.40, 0.99, 1.0 to 0.86, 1.0 and 1.0 for the mild, moderate, and severe inner race faults, respectively. This implies that although applying only phase domain transform, envelope and Fourier transform might be enough for moderate and severe faults, advanced signal processing is needed to enhance the fault signature for early detection of mild faults.

Faults prevention for the gear coupling of the azimuth thruster L-drive through a study of shaft alignment measurements

The propulsion system is one of the most important systems in a vessel. It is considered critical, since if it fails, directly compromises the operation and safety. A common fault on the azimuth propulsion L-drive system is the gear coupling failure, where on the last stage of damage the shaft can broke causing propulsion loss. The two main reasons of this problem are the shaft misalignment and lack of gear coupling teeth lubrication. Through a specific alignment measurement procedure, performed on three different vessels and 17 azimuth thruster L-drive, this study will prove that the shaft alignment between motor and thruster is affected by the steering rotation of the azimuth system. The alignment changes due to steering position sometimes can be greater than alignment tolerance values, generating gear coupling damages. Then a specific procedure is proposed to measure, evaluate, and correct the alignment to prevent gear coupling failures and improve the system reliability.

Dynamic and quantitative risk assessment of Cruise ship pod propulsion system failure: An integrated Type-2 Fuzzy-Bayesian approach

Azipod propulsion has revolutionized the future of ship propulsion and maneuvering operations with over 20 years of experience, eventually improving ship safety, reliability, energy efficiency, and overall vessel performance. However, it consists of technically complex machinery systems; its breakdown can result in many potential failures with severe repercussions. In this work, an accident-based dynamic risk assessment study of the Cruise ship pod propulsion system has been carried out. It is based on the real-ship accident of the Norwegian Star, which resulted in the loss of ship propulsion. When historical accident statistics are limited, traditional methods fail to address the uncertainty, dynamic environment, and quantitative risk assessment problems. The goals include avoiding worst-case scenarios by illustrating the progression of dynamic change in risk and establishing the Bayesian network framework for dealing with uncertainty more effectively. Interval type-2 Fuzzy expert system is integrated with the dynamic Bayesian network and bow-tie model for quantitative risk assessment, which laid the groundwork for the subsequent hazard identification and quantitative risk assessment. This accident network summarizes how pod machinery operational failures can cause accidents. The estimated sensitive machinery nodes such as Main motor failure, propulsion system, and power system failure are the leading causes of pod propulsion system failures on board cruise vessels. Risk analysts and decision-makers in the marine and offshore engineering industry can use the suggested model as a decision support tool to considerably reduce and eliminate potential failures, improving the ship's safety and system reliability.

URANS prediction of ship performance: An analysis of propulsion system failure on turning behaviour of a ship in waves

The loss of ship propulsive power has been recognised as the most frequently occurring incident at sea. Given the fact that the manoeuvrability of a ship is highly reliant on the propulsive power produced by a rotating propeller, propulsion loss may pose potential threats to navigational safety in a real seaway by resulting in further serious incidents, such as collision, contact, and grounding. The key objective of this paper is to analyse the propulsion loss impacts on the turning capability of the KRISO Container Ship (KCS) model in different wave height conditions, using unsteady Reynolds-Averaged Navier-Stokes (URANS) computations. It is expected that this work will be of great interest to Master Mariners and navigating officers who are in charge of ship handling and help enhance navigational safety in real sea states.

Nonlinear URANS model for evaluating course keeping and turning capabilities of a vessel with propulsion system failure in waves

The loss of ship propulsion has been reported to be the most frequent cause of accidents at sea over the last few years. The loss of propulsive power has a notable effect on the behaviour of a ship during ship manoeuvring, and hence the manoeuvrability of ships suffering from propulsion loss should be accurately estimated for navigation safety. The aim of this study is to evaluate the effects of a propulsion failure on the manoeuvrability of the KRISO Container Ship (KCS) using a fully nonlinear URANS model, which is capable of resolving complex fluid-structure interactions with high accuracy. A series of case studies were carried out to compare the ship performances of both the normal and propulsion loss condition, especially for the course keeping and turning circle manoeuvres. The results explicitly revealed that the propulsion failure has a strong influence on the ship manoeuvrability, implying the importance of sufficient propulsion power when vessels are underway. The key findings obtained from this study are believed to provide navigators with a practical insight into ship manoeuvrability under the propulsion failure condition as well as contribute to developing standards for navigational safety in waves.

Learning from failures in cruise ship industry: The blackout of Viking Sky in Hustadvika, Norway

This article brings to attention learning from the failure - blackout, loss of propulsion and near grounding - of Viking Sky cruise ship which occurred in Hustadvika, Norway, in March 2019. Failures and accidents in the cruise ship industry attract the global media and can severely impact reputation and business performance of companies and authorities involved. A system approach investigation and analysis - CAST - was employed with the aim to maximize learning from the Viking Sky’s failure through a systematic approach and to contribute to failure reduction in the cruise ship industry. Three main recommendations emerged from this study: an overview of the accident or failure precursors and resilience indicators; safety recommendations for other cruise ships; lessons and strategies of actions for the increased cruise operations in the Arctic and Antarctic areas. It was found that several accident or failure precursors, for example, a low level of lubricating oil, the failure of a turbocharger, an inoperative large diesel generator, lack of functionality for safety equipment due to bad weather, and others precursors contributed to failure and highly critical situation encountered by Viking Sky in Hustadvika. Resilience indicators such as the master’s immediate decision to launch mayday, the crew preparedness, and the way how the emergency situation was handled were found to have positive impacts on critical situation of Viking Sky. This article highlights also that adaptations and improvement of standards and regulations for harsh environmental conditions can play an important role in prevention of marine accidents. Furthermore, for a better understanding of correlation between environmental loads and their effects on machinery systems, digital solutions such as digital twin for condition monitoring of cruise ships in the Polar areas are seen as possible innovative solutions yet to be fully implemented in the marine industry.

An Integrated Fault Isolation and Prognosis Method for Electric Drive Systems of Battery Electric Vehicles

The electric drive system is a key subsystem of battery electric vehicles (BEVs). Abnormalities in the electric drive system components may lead to performance degradation in the drive system and, more severely, loss of power in the vehicle. This article presents an integrated prognosis system for early detection and isolation of the electric drive system and component faults. The system first calculates multiple health features, known as health indicators derived from the available onboard sensor signals. Then, an integrated prognostic and fault isolation strategy is used to isolate the root cause of electric drive faults by monitoring the performance of the multiple health indicators. The prognostic system uses a hierarchical approach: it first determines if there is a degradation in the electric drive system by comparing the system achieved torque with the estimated torque and, then, goes further to check multiple component-level health indicators for the various components comprising an electric drive system, including motor stator winding, three-phase current sensors, and resolver. After a component has been detected to degrade to a certain level, the prognosis system sends out an alert before the severe performance reduction of the drive system occurs, thus protecting the customers from loss of propulsion and walk home situations.

Experimental study on the failure of tangential anti-loose dowel of ship hydraulic fluid tubing in alternating torque and vibration environment

The internal hydraulic fluid tubing in central shaft is a critical part of pitch adjusting paddle in the ship propulsion system. The failure of screw pairs of internal hydraulic fluid tubing will result in a loss of propulsion. This real accident has happened on a ship. In order to determine the reason for the tangential anti-loose dowel falling out from the screw pairs, 380.5h and 147h alternating torque and vibration environment tests are completed on two samples with difference of manufacturing processing. The result shows that alternating torque and vibration combined stress is the synthesis stress for the dowel falling out from dowel hole. The basic reason is the larger fit clearance between dowel and dowel hole. This clearance is suggested to be manufactured below 0.2∽0.3mm, and the value of diameter for piercing outside the dowel hole should be greater than 1.95mm.

Predicting commercial fishing vessel disasters through a novel application of the theory of man-made disasters

Introduction: Vessel disasters (e.g., sinkings, capsizings) are a leading contributor to fatalities in the U.S. commercial fishing industry. Primary prevention strategies are needed to reduce the occurrence of vessel disasters, which can only be done by developing an understanding of their causes and risk factors. If less serious vessel casualties (e.g., loss of propulsion, fire, flooding) are predictors of future disasters, then reducing vessel casualties should in turn reduce vessel disasters and the accompanying loss of life. Method: This case-control study examined the association between vessel casualties and disasters using fishing vessels in Alaska during 2010–2015. Results: The findings show that vessels that experienced casualties within a preceding 10-year period were at increased odds of disaster. Other significant predictors included safety decal status and hull material. Practical Applications: The results of this analysis emphasize the importance of implementing vessel-specific preventive maintenance plans. At an industry level, specific prevention policies should be developed focusing on high-risk fleets to identify and correct a wide range of safety deficits before they have catastrophic and fatal consequences.

Preliminary Concept of an Unmanned Aerial Vehicle for Patrolling of Water Basins

The paper presents a preliminary concept of an unmanned aerial vehicle (UAV) designed with a form of the Kasper wing (known in Polish as the ‘Kasprzyk wing’) and intended for aerial patrolling and monitoring of large water basins, mass gatherings, ground traffic, state borders, and other applications. Considering the potential uses resulting from the applications, the UAV defined in this preliminary concept would have to operate with high-value onboard data acquisition equipment. This is why this paper focus specifically on the problems of security and protection of the onboard data acquisition equipment the purchase costs of which can be several times higher than the costs of building the UAV airframe. This problem brought the authors to the main assumption of the work presented herein: to develop an UAV design which would provide maximum security and protection of the onboard mission loadout even in conditions of complete loss of propulsion and guidance control. The capability of safe emergency unpowered landing of the UAV enabled the application of an reflex airfoil based on the Kasper wing design. In the event of a propulsion power loss, the UAV could automatically begin a low advance velocity flight to reduce the risk of UAV failure upon touchdown. This was how the objective of this work was identified: to study the design criteria and select the materials for the fabrication of the UAV. The fabrication materials were selected to minimise the risk of failure or sinking of the UAV and its high-value onboard loadout in the event of emergency alighting on water. The behaviour of an UAV model at various loads which simulate real-life flight conditions required a multi-faceted analysis; the second part of the work discusses a selection of experimental methods (including an optically active layer method and a digital image correlation method) which will enable testing the strength properties of the fabricated structural elements of the UAV.

A Fault Management-Oriented Early-Design Framework for Electrical Propulsion Aircraft

Electrical propulsion has been identified as a key enabler of greener, quieter, and more efficient aircraft. However, electrical propulsion aircraft (EPA) will need to demonstrate a level of safety and reliability at least equal to current aircraft to be a viable alternative. Therefore, a robust and reliable fault management (FM) system is needed to prevent electrical faults causing loss of propulsion and critical flight functions. To date, FM of the electrical propulsion system has not been considered in detail for future EPA, nor has it been effectively integrated into the electrical architecture design. This poses a risk that the proposed electrical architectures will be infeasible from an FM perspective, and key FM technologies may not be sufficiently developed. Therefore, a methodology to incorporate FM into the early stages of the design of electrical architectures is required to determine viable FM solutions for a given EPA concept. This paper describes a novel, system-level electrical architecture design framework for EPA, which incorporates FM from the outset. This methodology captures the significant assumptions in the design and acknowledges the novel interfaces that exist between the electrical, conceptual, and FM design of EPA.

Risk Assessment of Flight Paths for Automatic Emergency Parachute Deployment in UAVs

This paper presents models for the risk assessment and generation of flight paths, which support the automatic deployment of emergency parachutes for unmanned aerial vehicles in emergencies due to loss of propulsion. Based on a risk analysis of the area underneath the flight path, suitable deployment positions are identified, which minimize the chance of endangering humans on the ground, property damage and loss of the air vehicle. Additionally, the flight path selection is guided by constraints, such as control data link availability or aircraft performance.

A Feasible and Applicable Motion Control Method for AUV

Both the high speed and the changing excess buoyancy can make it difficult in motion control of AUV, in order to solve the problems, an improved control method based on S-surface control is proposed. Taking static forces and coupling effects between longitude velocity and other dimensions into account, the compensation related to the speed is brought into the method to handle the effects caused by high speed. In accordance with the thoughts of S-surface control, an anti-windup intelligent integral method is presented to handle the changing excess buoyancy and propulsion loss via an adaptive weight determined by estimating the motion states of AUV. Finally, experiments of velocity control, yaw control and depth control are conducted, and the results prove the feasibility and advantages in application to AUV motion control.

Toe modifications in hind feet shoes optimise hoof‐unrollment in soundWarmblood horses at trot

It was shown that rolled-toe shoes smooth hoof-unrollment and thereby reduce peak loading of forelimbs in trotting Warmblood horses. Shoe design and shoeing technique for hind feet have been modified over recent decades from fully fitted, toe-clipped shoes to set-back, side-clipped shoes. To study the effects of different shoe modifications on loading and movement of the hind hoof. Ten clinically sound Warmblood horses were shod with 3 types of hind shoe: first, fully fitted, toe-clipped shoes, followed randomly by side-clipped shoes without a rolled toe that were set back by half the thickness of the hoof wall in the plantar direction and identical side-clipped shoes with a rolled toe, with 2 days between shoeing sessions to adapt to the shoes. Then horses were trotted in a straight line over a pressure-force plate combination. Hoof dynamics were compared statistically with the fully fitted shoe condition using a general linear model repeated measures test (P<0.05). There were no significant differences in the characteristics of limb timing, such as stance time and breakover duration nor the peak vertical and horizontal ground reaction force. By setting back the hind shoes, the centre of pressure at toe-off was positioned less dorsally. The rolled toe resulted in a smoother shift of the centre of pressure and thus more fluent hoof-unrollment. Both alternative types of shoe allowed a more lateral orientation of the centre of pressure at toe-off. Toe modifications of hind shoes can influence hindlimb kinematics positively. Setting the hind shoe back and rolling the toe leads to smoother hoof-unrollment, which enables the horse to coordinate movement correctly without loss of propulsion. Thus, shoe modifications might facilitate movement and thereby help prevent overload injuries.

Estimation of the probability of propulsion loss by a seagoing ship based on expert opinions

serious categories of hazardous events 1 in shipping. In specific external conditions it may lead to a loss of ship together with people aboard. The loss of propulsive power may be an effect of the propulsion system (PS) failures or of errors committed by the crew in the system operation process. In the safety engineering language we say that the propulsion loss probability depends on the reliability of the PS and of its operators. Determination of that probability is in practice confronted with difficulties connected with shortage of data on that reliability. This pertains particularly to the cases of estimation in connection with decisions taken in the ship operation. In such cases we have to rely on subjective estimations made by persons with practical knowledge in the field of interest, i.e. experts. The experts, on the other hand, prefer to formulate their opinions in the linguistic categories, in other words in the language of fuzzy sets. The author’s experience tells also that in the expert investigations it is difficult to maintain proper correlation between the system data and the system component data. The paper presents a method of the subjective estimation of propulsion loss probability by a ship, based on the numericalfuzzy expert judgements. The method is supposed to ensure that proper correlation. It is adjusted to the knowledge of experts from ships’ machinery crews and to their capability of expressing that knowledge. The method presented has been developed with an intention of using it in the decision taking procedures in risk prediction during the seagoing ship operation, in the shortage of objective reliability data situations.

Risk Analysis and Management for Marine Systems

ABSTRACTSources of risk to marine systems include equipment failure, external events, human error, and institutional error. Equipment failure, the most readily recognized hazard on ships, may be categorized as either independent failure, such as the loss of steering because of the failure of a power steering pump or common‐cause failure, such as the loss of propulsion and steering resulting from a total loss of electrical power to the ship. Risk from external events arises from hazards such as collision with other ships, sea state; wind, and ice or other weather factors. Humans provide another source of risk to marine systems when they lack skill, are excessively fatigued, or commit sabotage. Institutional failure creates risks from poor management including inadequate training, poor communications, and low morale.Risk studies may be classified according to whether they focus primarily on assessment, management, or communication; these aspects of risk studies are described to prepare users and readers of this paper for performing risk‐based analysis of marine systems. Methods are provided in the paper that can be used to develop risk‐based standards for system safety. The relationship between risk and standards is studied from a historical perspective. Great successes in controlling risk to health and safety are exemplified by the development of design methods for buildings, bridges, or super tankers that render them capable of withstanding extreme storms. Yet, familiar risks persist while less familiar ones escape attention and new ones appear. Ironically, management of some of the most difficult risks has led to improved standards of living. This paper provides background information, introduces fundamental concepts, and offers examples of risk methods applied to marine systems.

Z-Drive Escort Tug Operating Modes

The suitability of various types of tugs to perform indirect towing has been a lively subject of debate, mainly in the international arena, and increasingly in North America. In the United States, this is the result of the enactment of well-meaning laws to improve the safety of seaborne oil transportation in environmentally sensitive areas such as Puget Sound and San Francisco Bay. Escort by means of a tug tethered to the stern of a tanker to permit rapid response to loss of propulsion or steering is often promoted as being the best way to accomplish the goal of such legislation. The development of indirect towing has made it possible to satisfy the desire to combine environmental safety with reasonable transit speeds. Indirect towing uses steerable propulsion to present the profile of the hull to the direction of advance of the tanker. Simultaneous braking and steering forces result. At elevated speeds, extremely high line pulls can be achieved, but with some risk to the towing vessel as it is in a girthing situation at all times. Research conducted by Aquamaster-Rauma Ltd. reveals that vessels equipped with independently controlled steerable propulsion systems (i.e., Z-drives) are capable of other means of producing arresting and steering forces with reduced risk of placing the escorting tug in a potentially dangerous situation. In this paper, these methods are discussed with comments on the situations where each mode applies.

Implementation of an Adaptive Autopilot Unit

This paper presents details in the implementation of an adaptive autopilot unit used for ship course keeping and course changing. The control strategy is based on the scheme of self-tuning regulator (STR) in which the generalized minimum variance (GMV) control law is combined with an extended least square (ELS) parameter identification technique. A time-varying extended state Kaiman filter (EKF) is designed to estimate the state of the system under disturbances induced by the sea environment and loading conditions. ELS and EKF constitute an adaptive estimator by which both state vector and parameter vector can be estimated properly. A dual microcomputer system using warm standby redundant design is implemented to guarantee the reliability in the control and safety in the steering. The construction principles of hardware and software are discussed. A sophisticated simulation facility is extensively used in the design stage of the autopilot unit. Several sea trials have been performed at “DAQING 232”, a 15000 tdw tanker, the results of which show that the unit reduces the propulsion losses of the ship motion in addition to keeping the course satisfactorily.