Gear Loss Research Articles

A Novel Prediction Model for Churning Power Loss of Spur Gear

ABSTRACTThe prediction of churning power loss has been a difficult problem in the analysis of spur gears. Thus, an analytical prediction model based on the redefinition of churning power loss and energy transformation is proposed to estimate the churning power of spur gears. Churning power loss is defined as the combination of the power loss due to the drag on the end face, the power loss due to the tangential flow, the power loss due to the acceleration of lubricants in the tooth space, and the power loss due to the centrifugal force. Several comparisons of prediction and experimental results are made and good agreement of those is obtained. Finally, the components of churning power loss under different gears and work conditions are analyzed, and the influences of each part on churning power loss are obtained.

Detailed Investigation of the Eddy Current and Core Losses in Coaxial Magnetic Gears through a Two-Dimensional Analytical Model

This work introduces a 2D model that calculates power losses in coaxial magnetic gears (CMGs). The eddy current losses of the magnets are computed analytically, whereas the core losses of the ferromagnetic segments are computed using an analytical–finite element hybrid model. The results were within 1.51% and 3.18% of those obtained from an FEA for the eddy current and core losses in the CMG for an indicative inner rotor speed of 2500 rpm. In addition, the significance of the circumferential magnet segmentation is demonstrated in the CMGs. Furthermore, a parametric investigation of the efficiency of the system for different applied external loads is carried out. Finally, a mesh sensitivity analysis is performed, along with the computation of the average power losses throughout one full period, resulting in an at least 80% reduction in computational costs with a negligible effect on accuracy. The developed model could be a valuable tool for the minimization of power losses in CMGs since it combines high accuracy with a low computational cost.

Classification of numerical, experimental, and analytical approaches for gearbox oil flow and no-load gear power loss

The interaction of rotating machine elements with fluid in gearboxes results in fluid flow and no-load power loss. A targeted design of the gearbox lubrication system enables a reliable operation under economical and sustainable use of lubricant. This study focuses on the influence of various parameters on the oil flow and no-load gear power loss of a dip-lubricated single-stage gearbox. Numerical, experimental, and analytical results are presented and compared. A single numerical simulation setup without parameter-specific tuning is applied for a wide range of parameters. The evaluated wetted gear surface strongly depends on the circumferential speed and shows a strong correlation with the resulting no-load gear loss torque. At lower circumferential speed, the wetted gear surface decreases before increasing at higher circumferential speed. Numerical and experimental results show good agreement in terms of magnitude and trend. The analytical approaches underestimate the numerical and experimental results. Nevertheless, they do provide a good representation of the trends in terms of the influence of immersion depth and rotation direction.

Power Loss and Damage Behavior of Gears Operating Under Loss of Lubrication

Abstract Geared turbofans need to withstand loss of lubrication due to inevitable off-design conditions. Additionally, the loss of lubrication specifications that have to be fulfilled are getting stricter. For a loss of lubrication event, today's geared turbofans are equipped with secondary oil supply systems. Their omission would reduce space and weight and, consequently, carbon emissions. However, this requires geared transmissions to withstand loss of lubrication events. In order to enable this, knowledge of the power loss and damage behavior of gears under loss of lubrication is required first. In this study, power loss and bulk temperature measurements of test gears under loss of lubrication on an FZG gear efficiency test rig are presented. Hertzian pressures in the pitch point up to 1723 N/mm2 and circumferential speeds up to 20 m/s were considered. The experimental results show the characteristics of increasing power loss and bulk temperatures under loss of lubrication depending on load and speed. At moderate operating conditions, no damage occurs within 20 s under loss of lubrication, whereas a load increase results in slight scuffing, and a speed increase results in severe scuffing. Oil centrifugation has a strong effect on the loss of lubrication performance. Additional experiments under reduced quantity lubrication demonstrate the impact of the remaining oil on the survivability of gears facing the loss of lubrication.

Ghost Gears in the Gulf of Gabès: Alarming Situation and Sustainable Solution Perspectives

This study represents a first step in investigating the prevalence, causes, and spatial distribution of Abandoned, Lost, or Discarded Fishing Gears (ALDFGs) in the Gulf of Gabès, a critical fishing area in Tunisia. Five main fishing gear types—benthic trawls, encircling nets, longlines, gillnets, and trammel nets were analysed for their loss rates and contributing factors. The study involved extensive surveys among local fishermen and the use of geographic information system (GIS) tools for spatial mapping. The findings reveal varying loss rates among different gear types, with longlines experiencing the highest losses (59%), followed by trammel nets (45%), gillnets (40%), trawls (38%), and encircling nets (36%). Causes of gear loss include entanglement on obstructions, conflicts with other fishing gears, entanglement with marine animals, adverse weather conditions, and intentional dumping at sea. The study highlights the challenges posed by the consistent increase in fishing effort in the region. Spatial distribution mapping indicates two significant concentrations of ALDFGs, correlating with specific fishing activities and depths. The study emphasizes the importance of addressing gear losses as a threat to marine biodiversity and ecosystem health. Recommendations for mitigation include improving boat equipment, raising awareness among fishermen, implementing effective waste management, and exploring economic incentives for ALDFG recovery. This research contributes essential insights for fisheries management, environmental conservation, and sustainable practices in the Gulf of Gabès. Collaborative efforts are crucial for developing and implementing strategies that minimize the impact of ALDFGs on the marine environment while supporting the socio-economic interests of fishermen.

Utilizing design of experiments techniques to determine the optimal coefficient of friction in spur gears

The friction occurring between the teeth of gears is a significant contributor to energy loss in gear drives. Factors like the load, speed, and coefficient of friction (µ) play a crucial role in determining the extent of frictional losses in gears. The coefficient of friction (µ) is a complex function influenced by various tribological parameters, including rolling, and sliding velocities, normal load at the tooth contact zone, oil temperature, and contact surface roughness. To analyze the impact of design and operating parameters on the coefficient of friction, a comprehensive statistical parametric approach was employed, combining numerical and statistical methods. The study employed a design of experiments methodology to numerically examine the impact of various tribological factors on the coefficient of friction. This methodology facilitated the identification of primary effects and crucial factors that have a significant impact on the variable µ. The findings derived from the computational models were subsequently compared with the discoveries of pre-existing investigations that includes both experimental and theoretical approaches. The proposed method represents a powerful tool for understanding the relationship and correlation between major tribological factors and the coefficient of friction. By employing this approach, it becomes possible to identify optimized tribological parameters. This information is valuable in improving the design and operation of gear systems, with the aim of reducing energy loss due to friction and enhancing overall efficiency.

Numerical study on the churning power loss of spiral bevel gears at splash lubrication system

AbstractIn order to predict the spiral bevel gear churning power loss, based on the Computational Fluid Dynamics (CFD) method, the computational model for the splash lubrication of the spiral bevel gear pair is established and validated by experiments. The churning power loss of spiral bevel gears is obtained and the corresponding flow field distribution in the gearbox with a pair of spiral bevel gears is analysed under a standard operating condition. For the churning power loss of spiral bevel gears, the loss of teeth surface is mainly caused by pressure while the loss of gear side is mainly generated by the viscous force. The effects of the gear rotational speed, oil level, oil temperature and oil shroud on the churning loss are also investigated and analysed. Ultimately, an optimisation method is proposed for the original spiral bevel geared transmission.

Ageing abandoned, lost, and discarded lobster fishing gear based on fouling assemblages

Abstract Abandoned, lost, or otherwise discarded fishing gear (ALDFG) is a by‐product of many fisheries. ALDFG impacts extend beyond the targeted species and include by‐catch, habitat degradation, and increased plastic in the environment. In particular ALDFG such as lobster gear attracts a succession of fouling organisms, increasing species diversity and productivity. In Cape Cod Bay, Massachusetts, USA, a seasonal lobster gear closure occurs for the protection of North Atlantic right whales (Eubalaena glacialis), allowing for the removal of ALDFG. In this study, the percentage cover of fouling organisms on recovered gear was used to model the age of the recovered gear (of indeterminate age because of missing tags). Between 2017 and 2021, a total of 379 traps were photo documented, of which 223 were of known age (1–22 years) and 156 were of unknown age. The age of the unknown traps was modelled utilizing a random forest algorithm using traps with a known age as a training library. High correlations between modelled ages and known ages (R2 = 0.634, P < 0.001*) slightly underestimated the age of the traps by 1.2–1.8 years, but are sufficient for developing an age distribution. The majority (79%) of traps were recovered off Provincetown and averaged 10–11 years old. Approximately 50% of the traps recovered in Cape Cod Bay were deposited or lost between 2005 and 2010. Calculating the age of ALDFG aids in determining the loss rate of gear and in identifying high concentrations of untended gear that can be recycled or reused. This analysis allows practitioners to understand the scale of the problem, helps quantify the quantity of gear in the ocean, and helps identify the areas most affected. This information improves the effectiveness of removal efforts by focusing on discrete areas of recurring and recent gear loss.

Regional oceanography affects humpback whale entanglements in set fishing gear

AbstractHumpback whales Megaptera novaengliae undertake annual migrations along eastern Australia, where they can be susceptible to entanglement in set fishing gear. This can potentially result in both sublethal and fatal outcomes for the whales, and financial losses for the fishing industry, including loss of gear and catch. Interannual fluctuations in entanglement records suggest that dynamic oceanographic features may be associated with the whales' migration path, and therefore, risk of entanglement. Using records of demersal fish traps off the coast of New South Wales (NSW), we identify two areas of high fishing pressure and entanglement risk overlap. Within each area, we combine entanglement observations with metrics associated with the East Australian Current (EAC) and climate (i.e., southern oscillation index). We show that the strength and position of the EAC was associated with the likelihood of entanglement in set fishing gear. In northern NSW (30.3° S), entanglement risk was highest between July and October when the EAC is relatively close to the coast. In contrast, there was no evidence suggesting that oceanography further south in the separation zone of the EAC (33.8° S) was associated with risk of entanglement. In the years following a strongly negative SOI (i.e., El Niño events), entanglement risk was also reduced. While we provide clear linkages with regional oceanographic dynamics and entanglement risk off NSW, if a dynamic ocean management approach to reducing entanglements is to be realized, further research into the fine‐scale movements of humpback whales is needed.

The new Marine Stewardship Council requirements to improve ghost gear management: Insights from the policy development process

Abandoned, lost or discarded fishing gear, otherwise known as ‘ghost gear’, impacts marine ecosystems in a variety of important ways. The growing recognition of these impacts has led to an evolution of fisheries management with a focus on gear loss avoidance and ghost gear mitigation. The Marine Stewardship Council has responded to the global ghost gear challenge through important revisions made to its Fisheries Standard during the recent Fisheries Standard Review (FSR). Fisheries certified against the Fisheries Standard will now be required to explicitly assess and manage their ghost gear impact on target stocks, on bycatch and on marine habitats - this outcome received strong support during public consultation undertaken for the policy development process. These changes are aimed implementation of best practice management strategies which emphasise gear loss preventative measures supplemented by mitigation and remedial action to minimise impact of ghost gear. The paper covers key insights of the policy development process which supported these changes including best practice research, policy design, public consultation, and impact testing. Conclusions of the policy process are discussed, included their likely implications for fisheries currently certified and those planning to seek certification against the MSC Fisheries Standard.

Why, and where, is commercial fishing gear lost? A global review and case study of Pacific Canada

Derelict fishing gear is a global problem, damaging marine ecosystems via habitat degradation and trapping marine life, thereby impacting fisheries. We conducted a global review of reasons for commercial gear loss, and used the findings to design a survey focused on coastal British Columbia (BC), Canada. We conducted dockside and on-line surveys of commercial fishers to record their experiences with lost gear across net, line, and trap gear types. The most common reasons for gear loss from the global review were interactions with other fishing vessels and their gear, marine weather, and snagging on submerged features. Survey results of 29 fishers in BC indicated that snagging gear on rough substrate was the most important reason for loss across all gear categories, followed by seafloor type. Other reasons for gear loss varied by net, line, and trap gear type. Understanding reasons for gear loss is important to reduce losses.

Energy Losses in Harmonic Gears

Energy Losses in Harmonic Gears

An Analysis Model for Predicting Windage Power Loss of Aviation Spiral Bevel Gears Under Optimal Injection Jet Layout

With the increasing rotating speed of aviation spiral bevel gears, the load-independent windage power loss caused by hydrodynamic behavior has a greater impact on transmission efficiency. An analytical model is established to predict the windage power loss of spiral bevel gears with oil injection lubrication. The improved model regards the total windage losses as the sum of oil–gas dragging effects on the tooth flank, toe/heel, circular cone surface, circumference of the teeth, and tooth root. Then the numerical method and analytical method are combined to calculate windage losses. A multi-objective NSGA-II optimization algorithm is used to optimize the jet layout parameters. The rationality and accuracy of this model are verified by comparing the calculation results of an example with data sets of existing experimental findings and computational fluid dynamics (CFD) simulation results. The calculation results show that compared with the tooth profile assumption method in the existing literature, the improved calculation formula of windage dragging effect on tooth flank can better reflect the influence of oil injection lubrication layout parameters on windage loss and make the windage loss calculation more accurate. Finally, the influence of gear body parameters, working conditions parameters, geometric parameters, and injection lubrication layout parameters on the windage loss is examined. This research provides a theoretical basis and methodological guidance for optimization design of reducing windage power loss.

Research on the calculation method of windage power loss of aviation spiral bevel gear and experiment verification

This paper proposes a method for calculating windage power losses of spiral bevel gears by dividing the losses into the sum of windage effects on tooth surface, toe/heel, conical surface, and circumferential surface, according to the gear structure. A calculation model for each component of windage losses is established based on the basic equation of fluid dynamics. Subsequently, a windage loss measurement test bench is developed, and a windage moment measurement method is proposed for experimental spiral bevel gears. The individual contributions of each windage loss component are calculated. The results of the calculations indicate that the gear speed is the primary factor that impacts windage losses, with the windage power loss being proportional to the 2.96th power of gear speed. Gear geometry parameters and the jet flow impacting the tooth surface are also significant factors, followed by the hub and spoke values in the wheel body parameters. The findings also show that an increase in lubricating oil content in oil-gas two-phase flow can significantly increase windage losses. Finally, a comparison between the dimensionless windage calculation values and the experimental measurement values demonstrates good agreement. This paper provides theoretical guidance for future research aimed at reducing windage power loss and improving the efficiency of aviation gear transmission.

Ghost fishing efficiency by lost, abandoned or discarded pots in snow crab (Chionoecetes opilio) fishery

Marine pollution by lost, abandoned or otherwise discarded fishing gear (ALDFG) often has negative impact on the ecosystem through plastic pollution and continuous capture of marine animals, so-called “ghost fishing”. ALDFG in pot fisheries is associated with high ghost fishing risk. The snow crab (Chionoecetes opilio) pot fishery is conducted in harsh weather conditions increasing the risk of fishing gear loss. Due to plastic materials used in the pot construction, lost gear can most likely continue fishing for decades. This study presents a method to quantify ghost fishing efficiency relative to catch efficiency of actively fished pots. On average, the ghost fishing pots captured 8.29 % (confidence intervals: 4.33–13.73 %) target-sized snow crab compared to the actively fished pots, demonstrating that lost pots can continue fishing even when the bait is decayed. Given the large number of pots lost each year, the ghost fishing efficiency is a considerable challenge in this fishery.

Research on characteristics of splash lubrication and power losses of reducer based on MPS method

AbstractThe distribution of lubricant flow field inside the two‐stage transmission reducer is very complicated during splash lubrication, which is difficult to be visually simulated and analysed using traditional finite element methods (FEM). There are many problems in model processing, algorithm selection, mesh division, and computational workload. Through sufficient investigation and experimental validation based on literature, the moving particle semi‐implicit (MPS) method is proposed to study the splash lubrication characteristics of a rail vehicle reducer. Through this method, the visual simulation calculation of multiple working conditions of reducer with complex structure is realised, and the unreasonable structure of the gearbox body is optimised. The model of oil supply demand in the Hertz contact zone of gear transmission is established, and the time‐domain variation law of oil particles number in the contact zone and oil supply state are analysed. It is found that the optimised reducer model can meet the demand of oil supply under the four typical working conditions of the rail vehicle. The higher the initial oil volume is, the more sufficient the oil supply is. Compared with the working temperature conditions of 20 and 80 °C, the lubrication effect is better at 40 and 60 °C. By analysing the power loss proportion of each gear, it is found that the sum of power loss of gear 1 and gear 2 is dominant under different working conditions, reaching 76%–99.5% of the total churning power losses.

The octopus pot on the North Atlantic Iberian coast: A plague of plastic on beaches and dunes

This baseline focuses on the octopus pot, a litter item found on the North Atlantic Iberian coast. Octopus pots are deployed from vessels in ropes, with several hundred units, and placed on the seabed, to capture mostly Octopus Vulgaris. The loss of gears due to extreme seas state, bad weather and/or fishing-related unforeseen circumstances, cause the octopus pots contaminating beaches and dunes, where they are transported by sea current, waves and wind actions.This work i) gives an overview of the use of octopus pot on fisheries, ii) analyses the spatial distribution of this item on the coast, and iii) discusses the potential measures for tackling the octopus pot plague on the North Atlantic Iberian coast.Overall, it is urgent to promote conducive policies and strategies for a sustainable waste management of octopus pots, based on Reduce, Reuse and Recycle hierarchical framework.

Experimental Study and Numerical Analysis on Windage Power Loss Characteristics of Aviation Spiral Bevel Gear with Oil Injection Lubrication

With the increasing speed of aviation spiral bevel gears, the load-independent windage power losses caused by hydrodynamic have increasingly more influence on gear transmission efficiency. Firstly, a test rig for the windage power loss of spiral bevel gear under oil-jet lubrication is established, and on this basis, a method for measuring windage torque is proposed. Next, the interactive effects of different injection lubrication parameters on the windage power loss were studied by orthogonal experiment, and the formula for calculating the windage loss was obtained by fitting the experimental data. Then, the fluid distribution, velocity field and pressure field around the gear were analysed by using a computational fluid dynamics (CFD) numerical model, and the mechanical and energy characteristics of the gear windage power loss were obtained. Finally, the dimensionless processing of the windage moment was carried out, and the variation of the dimensionless windage moment coefficient with the rotational Reynolds number is obtained. The comparison between the dimensionless windage moment coefficient of experimental data and simulation results shows that the CFD values are in good agreement with the measured data. This study provides experimental and methodological guidance for the calculation of windage power loss and windage reduction design of aviation gear pair under oil injection lubrication.

Effect of gillnet twine thickness on capture pattern and efficiency in the Northeast-Arctic cod (Gadus morhua) fishery

Gillnets are among the most common fishing gears worldwide. They are often made of thin twine, which is prone to wear and tear, limiting the lifespan of the gillnet. This increases gillnet turnover, and consequently increased risk of gear discarding, gear loss, ghost fishing and marine pollution. This might be mitigated by increasing twine thickness, and thereby breaking strength. However, the tolerable increase in thickness for gillnet durability without compromising the catch efficiency is unknown. Therefore, this study conducted gillnet fishing trials under commercial conditions in the Northeast-Arctic cod gillnet fishery analysing and comparing ways of capture and efficiency between gillnets with two different twine thicknesses for two different mesh sizes. The results demonstrated that a 30 % increase in breaking strength and twine stiffness did not affect catch performance. Therefore, thicker gillnet twine can potentially reduce marine litter by plastic debris from damaged and lost gears without compromising catch performance.

Stochastic microcontact model for the prediction of gear mechanical power loss

Gears serve as the primary power transmission element in many industrial and automotive applications. Power loss in the form of heat generation contributes both to reduced fuel economy and elevated transmission operating temperatures which can lead to premature failure of components. The power loss is made up of both load independent losses and load dependent losses. Gear designers need engineering tools to estimate both components to determine overall system efficiency. This research seeks to utilize stochastic descriptions of surface asperity profiles with simplified Elastohydrodynamic lubrication (EHL) metrics to estimate the effective friction coefficient in mixed lubrication gear contacts. Power loss experiments are performed to measure load dependent gear losses and compare them to the model results.