Windage Power Loss Research Articles

Novel Calculation Method for Windage Power Loss of Double-Helical Gear Transmission

Abstract This paper presents a novel fast calculation method for windage power loss (WPL) of the meshing double-helical gear pair. Firstly, based on the basic equations of fluid mechanics and computational fluid dynamics simulation method, the calculation method for single-tooth windage torque at the zone of meshing/nonmeshing is established; Secondly, the WPL of meshing gear pair with different gear parameters and operating conditions are obtained according to the single-tooth windage torque during a rotation period and the windage torque at the end faces, and the accuracy of the proposed WPL method is verified through the WPL test measurement and simulation; Finally, the effect of gear parameters and operating conditions on the WPL is studied.

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.

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.

Experimental and Simulation Analysis on Windage Power Loss of Herringbone Gear Pair

Abstract This paper presents a novel windage power loss (WPL) measurement method for the meshing herringbone gear pair. First, the WPL test rig of the herringbone gear pair is put up, and then the measurement sequence of WPL is described. Second, the WPL of different gear pairs is tested and the influence of operation speed, design parameters on the WPL of meshing gear pairs is studied. Finally, the WPL simulation analysis of meshing gear pair is carried out. The generation mechanism of WPL is analyzed and the WPL of each meshing gear pair at different rotational speeds is obtained, which verifies the accuracy of the presented WPL measurement method. The research on the measurement method of WPL can provide support for the optimization design of the high-speed gear pair.

CFD Modelling and Numerical Simulation of the Windage Characteristics of a High-Speed Gearbox Based on Negative Pressure Regulation

Windage power loss plays a leading role in the total power loss of high-speed gears, which seriously affects the transmission efficiency of gear systems and leads to high energy consumption. This paper proposes a negative pressure regulation method to reduce windage power loss. Based on the computational fluid dynamics theory, the flow field distribution and windage power loss in the gearbox under different negative pressure conditions are studied, and the effect of the negative pressure environment and speed on the windage power loss is obtained. In order to further save calculation costs, an optimization algorithm of the BP neural network based on a genetic algorithm is proposed to effectively predict the windage power loss. The results show that the high-speed airflow near the tooth’s surface will produce a large pressure moment, which is the main cause of wind resistance loss. The windage power loss increases with the increase in the negative pressure or speed of the gearbox, but the effect of speed is more obvious. The prediction results of the optimization algorithm are in good agreement with the finite element simulation data and the open literature, which can predict the best parameters for reducing windage power loss.

Mechanism and reduction of windage power losses for high speed herringbone gear

With the objective of reducing windage power losses (WPL) in herringbone gears, WPL experiments involving the use of a shroud are conducted. Based on computational fluid dynamics (CFD), a herringbone gear numerical model is established. Based on the renormalization group (RNG) k–ε two-equation turbulence model and dynamic mesh technique, the features of flow field distribution around the gear; mechanism of reduction of WPL; shroud installation distance, coverage, and installation position; and influence law of WPL are analyzed. The CFD and experimental results, which exhibit good consistency, are used to infer the WPL behavior with respect to the input parameters.

An experimental investigation of windage and oil churning power losses of gears and discs

This study presents comparable sets of churning and windage power loss measurements of a gear. Measurements are performed under windage (air only) and churning (immersion in oil up to a certain level) to quantify load-independent power losses of a family of spur and helical gears along with representative discs. Aiming at quantifying the impact of gear geometry on churning or windage losses to establish a baseline for the case of no enclosures around the gear, the test matrix is designed to investigate three key items: (a) contribution of losses along the periphery and faces, (b) the influences of gear teeth versus a toothless replacement disc as well as key design parameters (gear module and helix angle), and (c) a comparison of churning and windage power losses measured from the same exact set-up. The churning power losses are shown to increase with the static oil levels due to increased solid-fluid interactions. The impact of oil bath temperature (oil viscosity) on churning loss is observed to be more pronounced for higher oil levels. The presence of gear teeth on the rotating specimen (spur or helical) cause churning loss to increase modestly in comparison to the disc specimens. Furthermore, a larger tooth size results in higher churning power losses. The influence of gear teeth (gear vs. disc) on windage loss is shown to be significant, indicating that modeling a gear in a high-speed windage condition as a cylindrical disc might not be an acceptable practice.

Numerical Simulation on Windage Power Loss of High-Speed Spur Gear with Baffles

Windage power loss (WPL) is significant and cannot be neglected in a study on transmission efficiency and reducing the energy consumption of high-speed gear. The influence mechanism of the baffle on the reduction of WPL needs to be further studied. Based on computational fluid dynamics (CFD) technology, this paper puts stress on analyzing the influence of axial and radial baffles on viscous and pressure effects in WPL and the influence of baffles with groove structures on reducing WPL. The numerical calculation model of windage torque considering the baffle’s regulation is established, and the calculation results of WPL with different baffle configurations are obtained. The results indicate that the radial baffle mainly reduces pressure loss, while power loss caused by the viscous effect is mainly affected by the axial baffle. The baffle with the smallest clearance achieves the most significant suppression effect on windage. On this basis, adding groove structures to a smooth baffle can have a positive or negative impact on reducing WPL, and the baffles with circular grooves can further promote the reduction of WPL by 8.2%, compared with smooth baffles. This paper provides a reference for the optimal design of baffles in engineering applications.

Windage Loss Characteristics of Aviation Spiral Bevel Gear and Windage Reduction Mechanism of Shroud

With the increasing speed of aviation gear, windage loss has been the main component of power loss. Reducing windage is of great significance to improving the transmission efficiency of aviation spiral bevel gear. Firstly, the calculation model of enclosed spiral bevel gear was established, and the basic physical mechanism of windage power loss was illustrated by numerical simulation, so as to obtain the mechanical and energy characteristics of windage loss. Then, the influence of the geometry and clearance parameters of the shroud on the windage loss was studied by orthogonal test, variance analysis and optimization design. The mechanism of the shroud to reduce the windage loss under the multi-factors was also studied, and their interaction was obtained. The results show that the tooth surface clearance, heel clearance and meshing opening are significant factors, and the most significant factor is the heel clearance. The non-significant factor is the interaction of each factor. The least significant factor is the toe clearance. In other words, the windage power loss can be reduced to the greatest extent by simultaneously reducing the meshing opening of the shroud and the clearance value between shroud and the surface of the gear. Finally, based on the mechanism of reducing windage loss of shroud, the optimization design principle affecting the structural performance of shroud is put forward, which provides theoretical guidance for the practical application of shroud in windage reduction engineering.

Numerical Calculation Analysis and Characteristic Research on Windage Loss of Oil-Jet Lubricated Aviation Gear Pair

The VOF (volume of fluid) multiphase transient simulation model of the windage loss of the gear pair under oil-jet lubrication was carried out by using the dynamic mesh technology with the powerful parallel computing capabilities of the Super Cloud Computing Center. Firstly, a two-phase (oil-gas) turbulence numerical model was established in the process of oil-jet lubrication. The numerical simulation test was designed by orthogonal experiment. The influence of the oil-jet lubrication parameters and their interaction on the windage power loss was studied by means of variance analysis. The results showed that the influence of injection speed on the windage power loss was the largest and proportional, followed by injection temperature and injection pressure, and the latter two factors were inversely proportional. Then, the fitting calculation formula of windage loss related to each influencing factor is obtained based on the numerical simulation results. Furthermore, by observing the velocity vector distribution of the internal flow field of the gearbox with different time, the formation mechanism of windage loss is understood intuitively, and the measures to reduce windage loss are put forward. Finally, the mechanical and energy characteristics of the windage loss under different oil injection parameters are proposed, by analyzing and calculating the differential pressure force, viscous force, turbulent kinetic energy, and turbulent dissipation rate around the gear pair. This paper provides a method guidance for the calculation of windage power loss and efficiency of aviation gear pair under elastohydrodynamic lubrication in engineering application.

Efficiency of the eccentric rolling transmission

The aim of the article is to investigate the efficiency of the novel eccentric rolling transmission, which is a simplification of the cycloidal reducer, with parallel but not overlapping shaft axes. In this paper, a kinematic and load distribution analysis are presented with a view to determining the forces and rotational speeds necessary for efficiency calculation. The developed efficiency model involved power losses in rolling bearings, at meshing, as well as churning and windage power losses. For the verification, a transmission prototype with a 10:1 gear ratio and a dedicated test stand were designed and built. The results of the research showed that most substantial power losses occurred in the bearings and were several times greater than the losses associated with friction between the active surfaces of its main components. The transmission efficiency improved with increasing load and decreased with increasing rotational speed, reaching a maximum of 96% at nominal torque. The proposed model allows predicting the efficiency of the transmission at the stage of its design, which can further facilitate the optimization of the transmission parameters considering expected operational conditions.

On windage power loss reduction achieved by flanges

On windage power loss reduction achieved by flanges

Optimal Design of Computational Fluid Dynamics: Numerical Calculation and Simulation Analysis of Windage Power Losses in the Aviation

Based on the theory of computational fluid dynamics (CFD), with the help of the Fluent software and the powerful parallel computing capability of the super cloud computer, the single-phase flow transient simulation calculation of the windage power loss of the engagement spiral bevel gear pair (SBGP) was performed. The two-equation SST k-ω turbulence model based on the assumption of eddy viscosity was adopted, which was improved from the standard k-ε model combined with the Wilcox k-ω model. The SST k-ω turbulence model inherited the respective advantages of the Wilcox k-ω model in the near-wall region and the k-ε model in the free shear layer and could more accurately describe the resistance and separation effect of the gear tooth surface on the airflow. The simulation analyzed the airflow characteristics around SBGP and the mechanism of the windshield to reduce the windage loss of the gear. It also studied the influence of the windshield clearance and opening size on the windage power loss. Then the orthogonal experimental analysis method was adopted to perform numerical simulation analysis. The windage torque was studied under different clearance values between the windshield and the gear tooth surface, as well as the large end and the small end. The variance analysis was performed on the numerical simulation data. The results showed that when the windshield clearance value was 1 mm and the engagement opening was 30°, the windage torque was the smallest, and the effect of reducing the windage power loss was the best. According to the changes in the pressure, velocity, and turbulent kinetic energy cloud diagram of the flow field in the reducer during multi-group simulation tests, the local optimal windshield configuration was obtained, which provided a method for further research on the multi-objective optimization of the windshield and the windage loss of the gear pair under the oil–gas two-phase flow and also provided a reference for the practical engineering application of the windshield.

On the estimation of the windage power losses of spiral bevel gears: An analytical model and CFD investigation

Windage power loss, a form of load-independent power loss, is always one of the hotspots for reducing fuel consumption and overall weight in aero-engine applications. This paper represents a considerable improvement in the analytical model for estimating the losses of spiral bevel gears and proposes a novel overset mesh method for the prediction of the windage losses. The improved analytical model details the total windage losses as the sum of air dragging effects on the periphery and toe/heel. Once each loss is calculated, the total losses could be then determined. Furthermore, by leveraging the computational fluid dynamics (CFD) software and exploiting the overset mesh strategy, the windage behavior of the gear is evaluated. Moreover, direct comparisons between theoretical /numerical results and experimental findings demonstrate that both methods are capable of estimating the windage power loss values. The results clearly show that pressure effect is the chief cause of the overall windage loss for the spiral bevel gear and the major windage losses are located nearby the gear teeth, much greater than the toe/heel.

Application of an unstructured overset method for predicting the gear windage power losses

Enhancing the efficiency of gear systems is of significance to reduce fuel consumption and overall weight. Windage power losses become prevailing in high-speed gear systems, such as aero-engine applications. To avoid the shortages and limitations of commonly used methods (e.g. negative volume in dynamic mesh method and one moving object in sliding meshing method), this paper describes an unstructured overset computational fluid dynamics technology to simulate the airflow pattern in a gearbox and calculate the windage losses. A disk, a spur gear and a helical gear, spinning in the air at rotational speed up to 7200 r/min are studied respectively, the windage power losses obtained by the numerical method show good agreement with experimental data and analytical findings in the open literature. Meanwhile, the associated deceleration torques exerted by pressure and viscous forces on spinning gear surfaces are also determined. Furthermore, the overset method facilitates to estimate the windage losses of a non-meshing gear pair. The results of this paper indicate that the overset method can accurately predict the windage power losses and provide a new route to investigate the flow pattern surrounding the gears. This method can serve as an effective tool for engineering applications in the future.

Power Flow and Efficiency Analysis of High-Speed Heavy Load Herringbone Planetary Transmission Using a Hypergraph-Based Method

The existing research problem is that the hypergraph-based method does not comprehensively consider the power loss factors of the mechanical transmission system, especially the existing windage power loss. In the power flow diagram, it is difficult to express and calculate the power loss separately, based on the power loss mechanism. Furthermore, the hypergraph-based methods purposed by some researches are not suitable for high-speed and heavy-load conditions. This paper presents a new hypergraph-based method for analyzing the transmission efficiency of complex planetary gear trains. In addition, a formula for calculating transmission efficiency is derived. The power loss model is established for a high-speed heavy-load herringbone planetary transmission pair considering several sources of power losses such as gear meshing friction, windage, and bearing friction. Then, the efficiency of a two-stage herringbone planetary transmission system is calculated using the proposed method. Furthermore, the influence of input speed, input power, and lubrication state on transmission efficiency is investigated. Finally, the proposed method is verified by comparing calculated values with values published in the literature.

Experimental Investigations About the Power Loss Transition Between Churning and Windage for Spur Gears

Abstract Oil sump lubrication is commonly used in gearboxes. When considering consistent speeds, oil immersion is usually set to low level in order to reduce associated power losses. This configuration is already used in some parts of helicopter mechanical transmissions, and it is under consideration as a lubrication solution for future electric powertrain where gearbox input speeds may be very high. The gear drag power losses are generally evaluated from either a churning power loss model for classic oil sump lubrication or a windage power loss model for oil jet lubrication. One may thus wonder how to estimate drag losses when considering a gear that only a small part is immersed. In this study, the authors investigate the transition between churning and windage phenomena for a spur gear. A series of torque measurements on a single spur gear rotating in an oil bath at numerous oil immersion levels have been carried out. Based on these results, a criterion to indicate which power loss model to use is proposed.

Development of an analytical model to estimate the churning power losses of a spiral bevel gear

A quasi-analytical model based on fluid mechanics is established to estimate the no-load power losses of a spiral bevel gear with splash lubrication. The no-load losses are defined as the sum of churning power loses and windage power losses. Then, the model is applied to different spiral bevel gears to measure the distributions of each individual power loss in the overall no-load losses, and the results agree well with sets of experimental findings. Considering windage effects, the impacts of rotating speeds, lubricating oil properties, and gear geometries parameters on churning losses are also quantified at low or moderate speed. Finally, by introducing the dynamic immersion depth, efforts are also made to explain uncommon behavior of the churning drag that the torque decreases with increasing of the rotating speed. A simplified evolution model of the dynamic immersion depth related to the Froude number inspired by the published work is presented to understand the churning behavior of bevel gears at moderate speed.

CFD modelling and numerical simulation on windage power loss of aeronautic high-speed spiral bevel gears

With the widespread of spiral bevel gears in aero-engines applications, it becomes a burning challenge to reduce the windage power loss owing to the high-speed rotation of these gears. As shrouding the gears has been manifested as an effective approach to reducing windage power losses and restricting the flow in the vicinity of gear teeth, a shroud in this paper is introduced to enclose the high-speed unmeshed spiral bevel gear. By leveraging the CFD software and selecting multi reference frame (MRF), the windage behavior of our proposed model is evaluated and compared with that without a shroud, and the influence of rotational speed of the bevel gear on windage power loss is also analyzed. Furthermore, further attention has been paid to the effects of the spacing between the bevel gear and the shroud. including the toe clearance, the face clearance and the heel clearance. Simulation results demonstrate that the windage power loss dramatically increases with the increment of the gear speed, and the windage power loss of the enclosing bevel gear declines rapidly by 80 percent relative to the bevel gear without a shroud. Moreover, it observes that the trend of windage power loss reducing with the decreasing spacing between the shroud and the bevel gear, finding the optimal spacing. This paper provides prerequisites towards pursuing the researches on the windage loss of meshing spiral bevel gears under oil-jet lubrication.