Gearbox Efficiency Research Articles

Efficiency and temperature of spur gears using spray lubrication compared to dip lubrication

Increased machine efficiency is a requirement in today’s world and geared transmissions are no exception. A back-to-back gear test rig was used to compare dip lubrication with spray lubrication regarding gearbox efficiency, mesh efficiency, gear temperature and surface roughness. Gears lubricated at the inlet of the mesh show a lower measured temperature when compared to spray lubrication at the outlet of the mesh. Spray lubrication, when compared to dip lubrication, yields the same efficiency for both rotating directions at the tested speeds of 0.5 to 20 m/s. Spray lubrication shows a significantly higher total gearbox efficiency at higher speeds, higher measured tooth temperature and no measurable change in surface roughness.

Model Wind Turbines Tested at Full-Scale Similarity

The enormous length scales associated with modern wind turbines complicate any efforts to predict their mechanical loads and performance. Both experiments and numerical simulations are constrained by the large Reynolds numbers governing the full- scale aerodynamics. The limited fundamental understanding of Reynolds number effects in combination with the lack of empirical data affects our ability to predict, model, and design improved turbines and wind farms. A new experimental approach is presented, which utilizes a highly pressurized wind tunnel (up to 220 bar). It allows exact matching of the Reynolds numbers (no matter how it is defined), tip speed ratios, and Mach numbers on a geometrically similar, small-scale model. The design of a measurement and instrumentation stack to control the turbine and measure the loads in the pressurized environment is discussed. Results are then presented in the form of power coefficients as a function of Reynolds number and Tip Speed Ratio. Due to gearbox power loss, a preliminary study has also been completed to find the gearbox efficiency and the resulting correction has been applied to the data set.

Efficiency of worm gearboxes

Within a research project, experimental investigations of large-sized worm gears (pairing steel worm with bronze worm wheel) with centre distance a = 315 mm are carried out. The primary aim is to gain verified knowledge regarding load-carrying capacity and efficiency for this worm gear size. The paper describes the conducted tests in detail and shows basic examples of experimental test results. In the course of these investigations, an overall worm gearbox efficiency of up to η = 96% is measured.

Applying thermophysics for wind turbine drivetrain fault diagnosis using SCADA data

Cost-effective wind turbine (WT) diagnosis using supervisory control and data acquisition (SCADA) data is a promising technology for future intelligent wind farm operation and management. This study presents a thermophysics-based method for WT drivetrain fault diagnosis. A synthesised thermal model is formed by incorporating thermal mechanisms of the drivetrain into a WT system model. Applications of the model are demonstrated in case studies of the gearbox and generator comparing simulation results and SCADA data analysis. The results show non-linearity of the gearbox oil temperature rise with wind speed/output power that can effectively indicate gearbox efficiency degradation, which may be attributed to gear transmission problems such as gear teeth wear. Electrical generator faults such as ventilation failure and winding voltage unbalance will cause changes to heat transfer and result in temperature changes that can be used for diagnosis purposes. This is shown by different patterns of stator winding temperature associated with power generation, while the simulation reveals the thermal mechanism. The method can be applied to diagnose some failure modes which are hard to identify from vibration analysis. The developed thermal model can play a central role for the purpose of fault diagnosis, by deriving relationships between various SCADA signals and revealing changes in the thermophysics of WT operation.

Power loss prediction: Application to a 2.5 MW wind turbine gearbox

A 2.5 MW wind turbine gearbox design was considered to perform a power loss prediction using different wind turbine gear oil formulations. A gearbox power loss model, previously validated with experimental results, was used to predict the efficiency of a full wind turbine planetary gearbox. The power loss model account the gears and rolling bearing losses using well established models calibrated with a method proposed by the author. The calculations clearly showed that significant energy savings can be achieved by selecting different base oils, modifying gear tooth geometry, or combining both.

Mathematical Modelling and Analysis for the Efficiency of Wind Power Gearbox Based on the Toroidal Drive

This paper proposed a kind of gearbox based on the toroidal drive to step up the speed of rotor rotation to a value suitable for standard induction generators for wind power field. In the inversion mechanism of the proposed gearbox, the system transmission ratio formula is obtained. Then the force analysis of the meshing components including a sun worm, a planet worm gear and an internal toroidal gear has been done respectively and the efficiency calculation formula of the gearbox system is deduced. Besides, the influences of the pressure angle and the helix angle of the sun worm and the internal toroidal gear for the gearbox have been further discussed. Finally, the verification of the efficiency analysis results of the gearbox is accomplished based on computer modelling and simulation.

Torque loss and wear of FZG gears lubricated with wind turbine gear oils using an ionic liquid as additive

This work presents a study of the tribological behavior of a mineral fully-formulated wind turbine gear oil additised with [BMP][NTf2] ionic liquid. The target application is the wind turbine gearboxes, thus the fully formulated oil with and without ionic liquid additive was tested in a rolling bearings test rig to measure the thrust rolling bearing torque loss and was also tested in a FZG gear test rig to measure the gears torque loss at operating conditions similar to the observed in a wind turbine gearbox.The results show that a wind turbine gear oil additised with ionic liquid can reduce the torque loss and improve the gearbox efficiency while producing less wear particles as observed in the oil analysis.

Numerical Simulation of Oil Jet Lubrication for High Speed Gears

The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined.

The Researches and Experiments of the Dynamic Operating Characteristic of Construction Machinery Gearbox

The operating characteristic of hydro-mechanical gearbox is vital to the vehicle performances. Basing on the testing terms of bench test and studying the dynamic operating performances of hydro-mechanical gearbox, a dynamic gearbox simulation model is built with the use of AMESim interface, which includes the engine model, torque converter model and the electro-hydraulic control model. The gearbox efficiency, the power loss without load, the oil pressure curve of clutch shift, all the parameters above could be simulated with the model. The results of gearbox experiments made sure that the gearbox is qualified the designing requirements and working in a good performance, which could be compared with the results of simulation to testify the correctness of the model, meanwhile, proved the perspectiveness and instructiveness of simulation model in gearbox designing and researching.

Research on Mechanical Gearbox Transmission Efficiency Test

Automobile gearbox transmission efficiency is an important parameter which can directly reflect the gearbox design and manufacturing level . This paper analysis detailed the effect factors on measurement, test method, and data processing for transmission efficiency of automobile gearbox, summed up the actual test experience whereby the mechanical transmission efficiency measurement , plays a reference and guidance role on improving test precision.

Gear Strength Optimization Analysis of Automobile Gearbox Based on the Software of MASTA

Automobile gear, as key part of automobile gearbox, bears the torque of automobile transmission, whose strength will directly affect the transmission efficiency of automobile gearbox and the service life of transmission system. On the basis of gear transmission theory, This paper focuses on gear pair of an automobile transmission as the research object, with the help of the professional transmission system software of MASTA, to realize the gear meshing analysis of the automobile gearbox, establish the simulation model of the automobile gearbox, simulate the actual load condition to complete the process analysis of the gear transmission. Finally, the strength optimization analysis of gear pair is implemented to obtain the reasonable gear design, which is more close to the gear meshing transmission process. There are great benefits to improve the overall performance of the automobile gearbox, effectively reduce the test cost, shorten development cycle, and optimize product structure. Therefore, it will provide guidance for the development and application of new transmission gear in the future, and present a new perspective and approach for the optimization analysis of gear strength.

Influence factors on gearbox power loss

PurposeBesides other approaches, fuel savings in automotive applications and energy savings, in general, also require high‐efficiency gearboxes. Different approaches are shown regarding how to further improve gearbox efficiency. This paper aims to address these issues.Design/methodology/approachThe paper takes the following approach: theoretical and experimental investigations of bearing arrangements and gear design as well as lubricant type and lubricant supply to the components lead to efficiency optimisation.FindingsNo‐load losses can be reduced, especially at low temperatures and part‐load conditions when using low‐viscosity oils with a high viscosity index and low oil immersion depth or low spray oil supply of the components. Bearing systems can be optimised when using more efficient systems than cross‐loading arrangements with high preload. Low‐loss gears can contribute substantially to load‐dependent power loss reduction in the gear mesh. Low‐friction oils are available for further reduction of gear and bearing mesh losses. All in all, a reduction of the gearbox losses in an average of 50 per cent is technically feasible.Originality/valueResults from different projects of the authors and from the literature are combined to quantitatively evaluate the potential of power loss reduction in gearboxes.

An Experimental Investigation of Spur Gear Efficiency

In this study, a test methodology was developed for the measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000rpm and transmitted power levels to 700kW. A precision torque measurement system was implemented, and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of modules and two surface roughness levels, operating in a dry sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on both load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.

Gear Windage: A Review

The efficiency of power and propulsive systems is increasingly being targeted as a means of reducing environmental impact. This has caused a renewed interest in industry in the losses associated with meshing gears. Gearbox efficiency varies from 98% to 99% for the best designed high power applications, but that can still equate to losses in megawatts. There are different mechanisms for losses that have been identified within gearboxes; these are meshing losses, bearing losses, windage losses, and churning losses. Depending on the application, the relative importance of these mechanisms varies. This paper reviews information on windage power loss. The motivation for this is that for some applications, this power loss can be a significant component, particularly lightly loaded high-speed applications. For instance, within some aeroengines, gears are mounted internally within bearing chambers. The component of windage power loss becomes significant in this case, and the flows associated with windage power loss have a significant impact on the amount of heat transferred to the oil within the chamber, which is a critical design consideration. This paper provides a review of experimental investigations and available models of gear windage power loss for spur, helical, and bevel gears. The aim of the review is to provide a comprehensive compilation of published information on windage power loss to assist gearbox designers in identifying relevant experimental and modeling information. While it is clear from the review of published work that the rotational speed, gear geometrical parameters, degree of confinement, and density of the fluid surrounding the gear are important, the degree of effect and general solutions for reducing power loss are less clear.

Influence of low friction coatings on the scuffing load capacity and efficiency of gears

The influence of multilayer composite surface coatings on gear scuffing load carrying capacity, gear friction coefficient and gearbox efficiency is discussed in this work. The deposition procedures of molybdenum disulphide/titanium (MoS 2/Ti) and carbon/chromium (C/Cr) composite coatings are described. Tests reported in the literature, such as Rockwell indentations, ball cratering, pin-on-disc and reciprocating wear, confirm the excellent adhesion to the substrate and the tribological performance of these coatings, suggesting they can be applied with success in heavy loaded rolling–sliding contacts, such as those found in gears. FZG gear scuffing tests were performed in order to evaluate the coatings anti-scuffing performance, which both improved very significantly in comparison to uncoated gears. These results in conjunction with the friction power intensity (FPI) scuffing criterion allowed the determination of a friction coefficient factor X SC to include the coating influence on the friction coefficient expression. The composite coatings were also applied to the gears of a transfer gearbox and its efficiency was measured and compared at different input speeds and torques with the uncoated carburized steel gears. Significant efficiency improvement was found with the MoS 2/Ti coating.

Molybdenum disulphide/titanium low friction coating for gears application

Multi-layer composite surface coatings made of MoS 2/titanium, exhibit good mechanical and tribological properties in several industrial applications. Its applicability to industrial gears is discussed in this work. Several tests, like Rockwell indentations, ball cratering, pin-on-disc and reciprocating wear tests, were performed in order to evaluate the adhesion to the substrate and the tribological performance of this coating. Twin-disc tests, performed at high-contact pressure and high-slide-to-roll ratios, confirmed the good adhesive and tribological properties of the MoS 2/titanium coating and left good indications about the applicability of the MoS 2/titanium coating to gears. Scuffing gear tests were performed in the FZG machine in order to evaluate the anti-scuffing performance of this coating. Finally, the MoS 2/titanium coating was applied to the gearing in a gearbox and its influence on the gearbox efficiency was studied.

Tribological Study of Grease Lubricated Plastic Wormgear for Automotive Applications

Plastic wormgear has many application opportunities in automotive industry because of its low noise and lightweight properties. Three major concerns about plastic wormgear are bending strength, efficiency or friction, and wear. Since standard worm and wormgear designs are developed mainly for metal gears, they are not applicable for the design of plastic wormgear. This paper presented a non-standard design to increase the bending strength of plastic wormgear. By increasing gear contact ratio, the maximum contact stress on the plastic gear tooth was reduced to prevent wear of the plastic wormgear flank. The load, speed, and grease effects on gearbox efficiency and friction coefficient were experimentally studied. While load had a major effect on friction coefficient of grease lubricated plastic wormgear, the speed had much less influence on the friction coefficient of the plastic wormgear. Misalignment of the worm shaft had significant impact on the efficiency of the worm gearbox. Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Cancun, Mexico October 27–30, 2001

Nonlinear Adaptive Control of a CVT Based Parallel Hybrid Passenger Car

The driveline of the Autark Hybrid Vehicle, which is developed at the TU München, is based on a CVT (Continuously Variable Transmission). Due to the CVT the model used to design the driveline controller is inherently nonlinear. Moreover several clutches make the model multistructural. Varying vehicle mass and an operating point dependent gearbox efficiency require the application of robust control methods. In this paper a robust controller design based on Sliding Mode Control (SMC) is presented. Since it can be proven that this approach is not robust to a varying gearbox efficiency the controller is extended by an adaptive approach.

自動車用歯車装置の伝達効率について

自動車用歯車装置の伝達効率について