Reduction Gearbox Research Articles

Research on Energy-saving Technology of Crank Balanced Pumping Unit

In order to saving energy and emission reduction, a secondary balance technology was used to reform the conventional beam pumping unit. The output torque from the reduction gearbox of conventional beam pumping units is usually characterized by its periodic drastic changes. Based on the idea of

The Dynamic Analysis of Reduction Gearbox of NC Gear Shaper Based on ADAMS

The key factors of NC gear shaper working steadily are directly influenced by the mechanical properties of reduction gearbox of NC gear shaper .The reasons of the reduction gearbox of NC gear shaper producing vibration have been studied in condition of unstable load when it works based on ADAMS . The speed of shafts and the meshing force of gears are obtained from the dynamic simulation analysis by the virtual prototyping technology . It shows that the reduction gearbox of strength of the vibration increases from input shaft to output shaft and the vibration strength which reduction gearbox works in the unstable input speed is greater than that in unstable load torque.

Additional Damping Conditions Analysis and Calculation for Exciting Force and External Load

This paper firstly starting mechanism of vibration and noise from gear, gear noise mechanism is explained, and analyze the factors and the impact of noise on the gear reducer. Secondly, the establishment of a complete solid model of gear reducer and reducer model for finite element model, the reduction gear box gear reducer of modal analysis and finite element modal calculation, and points out the dynamic analysis of structure, size and weight factor is proportional to the reciprocal of the modal frequencies of each mode is the with the frequency is low, that is, the greater the weight. Once again, the main measure of load and control of gear noise of gear is analyzed, including the calculation, for exciting force reduction gear reducer gear load computation. The analysis and calculation are the theoretical basis of gear structure design and its performance evaluation.

IC 센서를 이용한 고속철도차량 구동장치의 무선 온도 모니터링 시스템

Driving gear units can be affected by various problems, including those associated with external or internal defects in the bearing, problems with the lubricant oil, high-loading of the railway, and frequent impacts generated by rail joints. Temperature monitoring is a basic method in diagnosing abnormal conditions in the reduction gear and other components. This paper describes a new wireless monitoring system for the temperature diagnosis of abnormal conditions of the reduction gear. Integrated circuit (IC)-type temperature sensors were installed in the reduction gear box of a high-speed railway car. The temperature data from the reduction gear were acquired and analyzed in situ during high-speed rail operation. Analysis of these data was used to alert the driver and/or maintenance personnel when problems occurred.

Condition monitoring of gearboxes using synchronously averaged electric motor signals

Due to their prevalence in rotating machinery, the condition monitoring of gearboxes is extremely important in the minimization of potentially dangerous and expensive failures. Traditionally, gearbox condition monitoring has been conducted using measurements obtained from casing-mounted vibration transducers such as accelerometers. A well-established technique for analyzing such signals is the synchronous signal average, where vibration signals are synchronized to a measured angular position and then averaged from rotation to rotation. Driven, in part, by improvements in control methodologies based upon methods of estimating rotor speed and torque, induction machines are used increasingly in industry to drive rotating machinery. As a result, attempts have been made to diagnose defects using measured terminal currents and voltages. In this paper, the application of the synchronous signal averaging methodology to electric drive signals, by synchronizing stator current signals with a shaft position estimated from current and voltage measurements is proposed. Initially, a test-rig is introduced based on an induction motor driving a two-stage reduction gearbox which is loaded by a DC motor. It is shown that a defect seeded into the gearbox may be located using signals acquired from casing-mounted accelerometers and shaft mounted encoders. Using simple models of an induction motor and a gearbox, it is shown that it should be possible to observe gearbox defects in the measured stator current signal. A robust method of extracting the average speed of a machine from the current frequency spectrum, based on the location of sidebands of the power supply frequency due to rotor eccentricity, is presented. The synchronous signal averaging method is applied to the resulting estimations of rotor position and torsional vibration. Experimental results show that the method is extremely adept at locating gear tooth defects. Further results, considering different loads and different gears in the gearbox suggest some potential advantages and limitations of the method and provide some motivation for future investigations.

Application of the AE Technology to Fault Diagnosis in Gezhouba Dam Shiplock Mechanical Hoist Reducer

Acoustic emission detection principle was used in testing the working status of Gezhouba Dam ship lock mechanical hoist reducer. According to wavelet analysis technology, high frequency signals of the acoustic emission is decomposed and reconstructed so as to eliminate noise and improve the signal-to-noise ratio. Then the Hilbert envelope transformation analysis is adopted to identify fault information. The results show that wavelet envelope spectrum analysis of the acoustic emission signals can be effectively used in fault diagnosis of reduction gearbox.

Development of meat-bone separator for small scale fish processing

The belt and drum type meat-bone separator was developed for small-scale fish processing and evaluated using Tilapia fish (Oreochromis mossambicus) in terms of capacity, yield, percentage yield, bone content, colour and power consumption. It consists of a perforated drum (3mm), single phase electric motor, speed reduction gear box and drive system. The machine was evaluated using two food grade belt viz., natural rubber (Belt A-35 shore) and canvas belt (Belt B-65 shore) for three drum speeds. The machine capacity was in the range of 45.59 to 68.54kg h(-1) for belt A with a yield of 1.148, 1.069 and 1.066kg, and 49.13 to 78.13kg h(-1) for belt B with a yield of 1.253, 1.312 and 1.269kg at drum speeds of 14, 20 and 24rpm, respectively. For belt A, the highest yield (1.148kg) was obtained at 14rpm drum speed which was 63.78% on dressed weight basis and for belt B, the highest yield (1.312kg) was obtained at 20rpm drum speed which was 72.89% on dressed weight basis. The increased number of passes for meat recovery increased the chances of insertion of bone fragments into minced meat and decreased the colour values (L-a-b). The total energy consumption did not vary significantly.

Kinetic Analysis of Planetary Gear Box

Structure noise of marine gearbox seriously affects warship’s concealment, stability of transmission system and amenity of crew working environment. There are many ways to control structural vibration. To add damping in reduction gear box is an effective measurement to suppress box resonance. The key to design damping structure is to determine the parameters of the structure. In most instances, the structural parameters depend on experience and many experiments, which is lengthy and expensive. This paper made an analysis at design stage of reduction gear product by finite element method. This can determine the parameters of box structure, and reduce the input effectively. This method has important theoretical value and application prospect.

Failure Analysis of a Herringbone Gear

Herringbone gears are extensively used in numerous engineering applications including gearboxes. Premature failures of such gears could lead to many serious consequences such as process downtime and late delivery which are critically important in this day and age of intense competition. This paper reports the results of failure investigation of a herringbone gear in a reduction gearbox used in a hot rolling steel re-bar mill in Thailand. The gear fractured after only 24 hours of service. The fractured gear was inspected visually and macroscopically, and all critical dimensions were measured. Chemical compositions of the materials were analysed. Fracture surfaces and microstructure of gear material were examined, and microhardness measured. Stress analysis was performed using finite element methodology. It was found that the premature failure of the gear, which appeared as a longitudinal crack, was due to excessive stress. The crack originated at the root of the keyway. Careful examination revealed that there was a slight misalignment between the key and the keyway which resulted in excessive stress. The lesson learned from this failure is that manufacturing defects, however slight, could lead to premature failures of key components such as gears, and could be very costly. It is recommended that apart from proper designs of components, good manufacturing practices are also necessary to minimize the chance of premature failures.

Effect of MoS2-based composite coatings on tribological behavior and efficiency of gear

MoS2-based Ti composite coatings were deposited on the SCM420 alloy and gears using an RF magnetron sputtering (RFMS) system. While MoS2 coating had been coated on the silicon substrate. The coatings structures were compared to each other to find the effect of Ti. The composite coatings have been tested in a ball-on-disk tribometer to investigate tribological behavior at various conditions. The scratch test was conducted to characterize adhesion force between composite coatings and substrates. The structure of the coatings has been extensively studied by a variety of techniques, including optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc. The composite coatings were also applied to the gears of a reduction gearbox. The efficiency of uncoated and MoS2-based Ti coated gear was measured and compared at various input rotating speed under absorption oil film condition. It was found that the efficiency of gear had significantly improved after MoS2-based Ti composite coatings deposition.

Optimal design of a tilling machine reduction gearbox using Matlab

This paper describes the optimal design of the reduction gearbox of a tillage machine. The minimum center diameter was selected as the objective, and the contact fatigue strength, bending fatigue strength, condition of nonintervention, and oil film thickness ratio of the gearbox were applied as constraint conditions. The optimal model was solved by a Matlab program. The results show that the center diameter of the reduction gearbox decreased by about 10%. The resulting decrease in weight and volume led to a reduction in the amount of gearbox material and a consequent decrease in production cost.

Optimal filtering of gear signals for early damage detection based on the spectral kurtosis

In this paper, we propose a methodology for the enhancement of small transients in gear vibration signals in order to detect local tooth faults, such as pitting, at an early stage of damage. We propose to apply the optimal denoising (Wiener) filter based on the spectral kurtosis (SK). The originality is to estimate and apply this filter to the gear residual signal, as classically obtained after removing the mesh harmonics from the time synchronous average (TSA). This presents several advantages over the direct estimation from the raw vibration signal: improved signal/noise ratio, reduced interferences from other stages of the gearbox and easier detection of excited structural resonance(s) within the range of the mesh harmonic components. From the SK-based filtered residual signal, called SK-residual, we define the local power as the smoothed squared envelope, which reflects both the energy and the degree of non-stationarity of the fault-induced transients. The methodology is then applied to an industrial case and shows the possibility of detection of relatively small tooth surface pitting (less than 10%) in a two-stage helical reduction gearbox. The adjustment of the resolution for the SK estimation appears to be optimal when the length of the analysis window is approximately matched with the mesh period of the gear. The proposed approach is also compared to an inverse filtering (blind deconvolution) approach. However, the latter turns out to be more unstable and sensitive to noise and shows a lower degree of separation, quantified by the Fisher criterion, between the estimated diagnostic features in the pitted and unpitted cases. Thus, the proposed optimal filtering methodology based on the SK appears to be well adapted for the early detection of local tooth damage in gears.

Determination of Turboprop Reduction Gearbox System Fatigue Life and Reliability

Two computational models to determine the fatigue life and reliability of a commercial turboprop gearbox are compared with each other and with field data. These models are (1) Monte Carlo simulation of randomly selected lives of individual bearings and gears comprising the system and (2) two-parameter Weibull distribution function for bearings and gears comprising the system using strict-series system reliability to combine the calculated individual component lives in the gearbox. The Monte Carlo simulation included the virtual testing of 744,450 gearboxes. Two sets of field data were obtained from 64 gearboxes that were first-run to removal for cause, were refurbished and placed back in service, and then were second-run until removal for cause. A series of equations were empirically developed from the Monte Carlo simulation to determine the statistical variation in predicted life and Weibull slope as a function of the number of gearboxes failed. The resultant L 10 life from the field data was 5,627 h. From strict-series system reliability, the predicted L 10 life was 774 h. From the Monte Carlo simulation, the median value for the L 10 gearbox lives equaled 757 h. Half of the gearbox L 10 lives will be less than this value and the other half more. The resultant L 10 life of the second-run (refurbished) gearboxes was 1,334 h. The apparent load-life exponent p for the roller bearings is 5.2. Were the bearing lives to be recalculated with a load-life exponent p equal to 5.2, the predicted L 10 life of the gearbox would be equal to the actual life obtained in the field. The component failure distribution of the gearbox from the Monte Carlo simulation was nearly identical to that using the strict-series system reliability analysis, proving the compatibility of these methods.

Investigation of a failed axle of a reduction gearbox

After 11,300 h of operation, one of the axles of the reduction gearbox of the hoist mechanism of a dockside crane failed due to the propagation of a fatigue crack. The axle contained two gears, the largest of which was mounted swith a key, while the smallest gear was an integral part of the axle. On both ends of the axle a bearing was mounted: one cylindrical bearing and one spherical roller bearing (locating bearing). The axle was made from 17CrNiMo6 steel, and the machined gear teeth were case carburised. The failure of the axle occurred in the middle between both bearings of the axle, on a non-contacting part of the gear machined on the axle. During visual inspection striations were observed on the fracture surface and three separate crack initiation zones could be observed on three neighbouring gear teeth. The ratio of final fracture versus fatigue fracture was low, indicating a low nominal stress on the axle. The three initiation sites were investigated with optical microscopy and SEM, and clear indications of a ductile overload fracture were found. In an etched longitudinal section of one of the gear teeth where initiation took place several cracks could be observed in the hardened case of the tooth. The hardness at the initiation site was found to be 777 HV, while the hardness at the final fracture (diametric position relative to the initiation of the crack) was found to be lower, namely 722 HV. It was concluded that at the initiation site during the case carburisation quenching cracks were formed, which then propagated through the whole section of the axle under relatively low operation load.

Design and Development of a Two-Megawatt, High Speed Permanent Magnet Alternator for Shipboard Application

Conventional gas turbine generator sets consist of a high speed turbine coupled to a low speed alternator through a speed reduction gearbox. This is required to maintain the alternator output frequency at 50 Hz or 60Hz, as output frequency is directly proportional to speed. Since power is also directly proportional to speed, the conventional system is bulky and possesses a very large footprint. The advent of solid-state inverters with their unique ability to efficiently and cost effectively change the alternator output frequency has made it possible to eliminate the need to link the alternator speed to the required 50/60 Hz output frequency. This output can be produced with a high-speed alternator, eliminating the need for a gearbox and greatly reducing the size, complexity, and weight of the machine by trading speed for torque. A direct drive system in which an alternator is coupled directly to a gas turbine is much more compact and highly efficient and requires much less maintenance. In this paper we will review the design and development of a high-speed permanent magnet alternator in an advanced cycle gas turbine system for shipboard applications. In addition to the alternator's design features, we will discuss design considerations including electromagnetic design, thermal design and structural design of high speed electrical machines, and review the alternator development including risk mitigation.

고무 탄성커플링을 갖는 선박 추진축계 비틀림의 동특성 개선

As for the marine propulsion shafting system using 4 stroke diesel engine, it is common to apply a reduction gear box between diesel engine and shafting to increase propulsion efficiency, which requires inevitably a certain elastic coupling to avoid chattering and hammering inside of gear box. In this study, the optimum method of rectifying propulsion shafting system in case of 750 ton fishing vessel is theoretically studied in a view of dynamic characteristics of torsion. After the replacement of diesel engine and gear box, the torsional vibration get worse and so some countermeasures are needed. The elastic coupling is modified from a present rubber coupling of block type having relatively high torsional stiffness to a rubber coupling haying two serially connected elements. Torsional vibration damper was installed at crankshaft free end additionally and moment of inertia of flywheel was adjusted. The dynamic characteristics of shafting system was improved by these modification. The theoretical analysis of torsional vibration are compared to measurement results using two laser torsion meters during the sea trial.

WS.3-2 英国 BOWMAN POWER 社の MGT コジェネレーションシステム

This paper describes an outline of micro gasturbine (MGT) cogeneration system that was developed by BOWMAN POWER Limited in England. The system is a fully integrated, compact micro gasturbine cogeneration package with 80kW electrical output and 150kW thermal output power, including stainless steel waste heat boiler. A high-speed, permanent magnet alternator, compressor and turbine are mounted on one shaft with no reduction gearbox. The shaft is supported with reliable oil-lubricated bearings. The power conditioner regulates and inverts a high frequency alternating current from the alternator output to 3phase, 400 to 480V, 50 or 60Hz alternating current. A Bowman unit can operate independently or in parallel to a commercial utility grid. The generator electrical efficiency of 28% and the overall thermal efficiency of the total cogeneration package over 80% are achieved.

Parts from aluminum alloys (body of the wheelpair reduction gearbox)

Parts from aluminum alloys (body of the wheelpair reduction gearbox)

Development of a novel gas turbine driven centrifugal compressor

The purpose of the paper is to provide design and operational information for the conversion of small turboprop engines into land-based shaft power drives. These can provide economical solutions to individual power requirements such as standby electrical generators, combined heat and power units, fan drives or centrifugal compressor drives. Considerable numbers of ex-military engines are currently becoming available at economical prices. One such engine is the Rolls-Royce Dart turboprop gas turbine which, although there are over 2000 still in civil and military service worldwide, is now being phased out of Royal Air Force operation. This paper describes the modification of a Dart RDa 12 engine to drive a centrifugal compressor from a smaller RDa 7, Mk 552, engine for a compressed air facility on a university campus. The modified engine has a power of over 2400 hp (1790 kW) at 15000 r/min and the compressor was driven directly from the engine output shaft supplying 10.5 kg/s of air at a pressure ration of 3.3:1. To achieve this, the turboprop's main reduction gearbox was removed, the teeth on the engine drive pinion ground down and a flexible coupling fitted to it to drive the RDa 7 compressor which was flange mounted on the engine gearbox-air intake casing. The removal of the main gearbox removed the drives to the lubricating oil pumps the fuel pump and the engine control system. The manner in which these problems were overcome and the method of operating the system are described. One of the most important considerations in starting such a direct drive system is the complete closing off of the air intake to the driven compressor and the design of an annular valve to perform this duty is described. The operating parameters including the flow, pressure ratio and engine turbine entry temperatures for this system are given.

Hybrid modelling, simulation and torque control of a marine propulsion system

A propulsion dynamics investigation of a single-screw powered ship, driven by two gas turbines in a combined gas and gas (COGAG) arrangement is presented. Distributed-lumped (hybrid) modelling techniques are applied to the propulsion drive-train consisting of two prime movers, a primary drive shaft, a reduction gearbox, a secondary drive shaft and a propeller. The study in this paper, unlike earlier studies, does not lump the drive-train components as discussed by Rubis [1] into analytically simple but unrepresentative pointwise models. By way of contrast, modelling and simulation techniques for distributed-lumped systems are presented herein, enabling the torsional vibration and stress analysis of the long drive shafts to be investigated with accuracy. As a result of this a torque control scheme can be derived for fuel flow regulation purposes, enabling superior speed and shaft torque control to be achieved. The results presented show the simulated dynamic responses associated with the propulsion unit, shaft and propeller following fuel flow changes.