Development of Hydrodynamic Mechanical Face Seal for Aircraft Engine Gearboxes With Gas–Liquid Hybrid Lubrication

Stationary shoulder friction stir welding has been used to weld 4-mm-thick 2219-T6 aluminium alloy at high rotation speeds. Strain plastic damage was applied to demonstrate the formation mechanism of welding defects at high rotation speeds above 2000 rpm. A three-way converging zone in the joint, in which materials of different microstructure characteristics converged from three directions during high tool rotation speed welding, was found. At the relatively high tool rotation speed, the significant differences in the microstructures would result in weld defects in this zone. It could be attributed to material toughness damage at high strain rate. With increasing tool rotation speed, the tensile strength of the joint constantly decreased. When the tool rotation speed varied from 2000 to 2600 rpm, the tensile strength decreased from 305 MPa (68.2% of the BM) to 238 MPa (53.2% of the BM).

A novel rotation extrusion processing system was self‐designed to prepare high‐performance polyethylene (PE) pipes. In this study, during the extrusion of the PE pipes at a high mandrel rotation speed, compressed air, as a cooling medium, was introduced through their interior to achieve the quick cooling of the inner wall and the effects of the inner wall cooling rate on the microstructure and mechanical properties of the obtained PE pipes were investigated. The experimental results showed that in contrast to conventional extrusion, the molecular orientation deviated from the axial direction under a high mandrel rotation speed and was fixed by the inner wall cooling; with increasing cooling rate, the orientation degree also increased. On the other hand, cooling promoted the augmentation of spherulites. So when the cooling rate reached a certain high point, the effect of cooling on the formation of spherulites was stronger than that on the fixation of the orientation. A much higher cooling rate decreased the orientation degree, which was closely related to the performance of the PE pipe. As a result, there was an optimal cooling rate of the inner wall during the rotation extrusion for better performance of the PE pipe. When the cooling rate was 1.5°C/s, the hoop strength of the PE pipe produced by the novel extrusion method increased from the original 24.1 MPa up to 37.1 MPa without a decrease in the axial strength, and the pipe's crack initiation time increased from 27 to 70 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

In this paper, two sets of H7014C/HQ1P4 bearings underwent test for high-speed performance under spray lubrication. The influence rules of rotation speed, pre-tightening force and oil pressure on the bearing temperature rising and host vibration were analyzed by adjusting the bearing rotation speed, axial pre-tightening force as well as oil pressure and measuring bearing temperature and host vibration. It has been found that the bearing temperature rises sharply as the rotation speed increases. At low rotation speed, the pre-tightening force has little influence on the bearing temperature rise, but at high rotation speed, the pre-tightening force should not be too small and can severely affect the bearing temperature rise. Increasing the amount of lubricate oil can reduce the extent of the bearing temperature rise while excessive addition cannot further improve this effect. It has been found that the bearing experiences an excellent high speed performance within the rotation speed of less than 24000r/min. This paper reviews various recent patents on high speed bearing test over the past three years. The list of patents reviewed here is by no means supposed to be complete or extensive but shows nevertheless evolution trends concerning high speed bearing test. An analysis of the reviewed patents repartition that allows conclusion of the expected future developments in this domain. Keywords: Axial pre-tightening force, H7014C/HQ1P4 bearing, high-speed performance test, oil pressure, rotation speed, temperature rise, vibration.

A new design tool, incorporating a commercial finite element program ADINA, has been developed for advanced analysis of film-riding face seals. This code is capable of modeling transient fluid-structure interaction inside a general seal configuration, enables designer to predict seal responses to speed, temperature and pressure changes in a timedependent manner. Therefore, through evaluation of influences of different seal parameters, the application envelopes of conventional spiral groove face seal can be extended to larger diameters, higher speed ranges. For applications that experience large seal surface coning due to high speed and large diameter, a new double spiral groove design has been developed with significantly increased angular film stiffness. Test rig results for some large-diameter seals are presented and compared with numerical simulation. INTRODUCTION TM^TMTM TM^TMTMTM« Significant advancement of non-contacting, filmriding face seal technology has been made over the past three decades. Today, film-riding mechanical face seals are used in almost every sector of industrial pumping applications. Because of their extremely low leakage, low friction and low wear, considerable efforts have been made to adopt them in aerospace application in the past few years [1,2]. Research and rig tests have shown that the aerospace sealing applications are much more demanding than the industrial applications. First of all, seals in gas engines experience frequent speed change, startup and shutdown. There are also times that the seals are operating at altitude conditions characterized by high rotational speed and low pressure. It is well known that higher speed requires higher film stiffness so that the stator can track the rotor to avoid face contact or blow open in case of axial rotor runout. But at the low-pressure (near vacuum) condition, conventional groove design will not be able to generate the required film stiffness due to the low air density which limits the hydrodynamic effectiveness. On the other hand, for large diameter applications, the thermal deflection from high speed can cause a divergent or convergent flow path between the seal faces and lead to film breakdown. In 1999, Menendez and Cunningham of PerkinElmer Centurion Mechanical Seals (formerly EG&G Sealol) reported the development of liftoff technology for air/oil axial sealing applications in aircraft APU main shaft, APU & propulsion engine gearbox and engine bearing locations [3]. With help of theoretical study, design code development and test rig investigation, today, the design of small and middle size of filmriding face seal for those applications is not presented as a challenge any more. However, there are still difficulties in hightemperature, high speed, large diameter applications. First, controlling the flatness of the seal faces becomes difficult as the size increases. Second the seal face coning of both the rotor and stator due to the thermal deflection grows proportionally to the fourth power of the seal diameter and second power of the rotational speed [2]. A negative deflection causing a divergent flow path can be disastrous for a standard hydrodynamic face seal, since it tends to cut off the flow of gas into the region between the faces. With standard hydrodynamic face seals, the deflection is expected to be much larger than the film thickness that the'face seal runs on [2]. Large positive coning can also result in failure for large diameter face seals because the resulting weak film stiffness increases * Engineering Specialist, AIAA member f Program Manger, AIAA member Copyright © 2001 by Xiaoqing Zheng and Gerald Berard. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. the chance efface contact. Since early 1990s, GE and Stein Steel have been developing a non-contacting aspirating face seal for large-diameter application [4,5]. It is a clever device which is essentially a hydrostatically balanced seal working solely on pressure difference. At nonor small-pressure difference conditions, the retraction coil springs will hold the seal face open to avoid face contact during startup and shutdown. Like other hydrostatic face seals, operating at lower pressure conditions than designed leads to reduced film stiffness. The weakest point of this seal is at a pressure condition such that the closing force from aspirator tooth and seal face is equal or close to the spring force. Then the film stiffness will be largely

The growth of hypocotyls of thick bean sprouts was examined using the rotary-type box cultivation method from an economical standpoint, by measuring yields, hardness, and color and moisture contents of hypoeotyls as indices of freshness, and total vitamin C content. After steeping in water for 5h at 28-300°C, the raw beans were germinated on a germinating floor (28-30°C) for 2 days and put in the rotary-type cultivation box, and then was water-sprayed at arate of 1l/min every 8h for 10min with 5rpm or 10rpm of rotational movement. By the rotary-type cultivation box method, a low speed rotation at 5rpm led to better growth than high speed rotation at 10rpm. This cultivation method with both rotatlon speeds was judged unacceptable compared with the ordinary method because the yield was markedly reduced, the hardness of hypocotyls was slightly excessive, moistuse content was reduced so much and surface color became yellow. These changes of the hypocotyls led to loss of freshness. The unacceptability of this method was more obvious at high rotation speed than at low speed. The total vitamin C content increased sharply and, thus this cultivation method is effective at least in this regard.

Hydraulic slotting technology is typically used in coal mines to enhance permeability and prevent gas outbursts. Because a coal seam contains many cleats and joints, this study investigated the influence of conventional application parameters on the hydraulic slotting effect by numerical simulation and experimental testing. The cleats in the coal generated stress concentration and initiated with the water jet impact, which promoted the formation of a complex fracture network. The optimized arrangement included angles with an inclination of 20–45° between the borehole and the coal seam strike. The water jet pressure and rotation speed determined the shape of the slot. A high water jet pressure and low rotation speed promoted the formation of cracks at the end of the slot and strengthened the permeability-enhancing effect. Coal fragments could more easily peel off from the sides of the seam and block the borehole. The high water pressure and low rotation speed application parameters were optimized without blocking the borehole. Results obtained by field application revealed that the gas extraction flow after optimization was 1.3 times that of conventional hydraulic slotting. An appropriate angle between the cleats and borehole can more effectively increase the permeability of the coal seam and results in higher gas drainage flow. The results of this study can be useful as guidelines for field applications of hydraulic slotting technology.

This article proposes an instantaneous rotational speed (IRS) sensing method that utilizes a circumferential constant-density-sine fringe pattern (CCDSFP) captured by a linear array sensor (LAS). A novel mathematical imaging model has been established to develop a mapping relationship between the correlation coefficient (CC) value of adjacent frame fringe signals and the IRS. The influence of various factors on the sensing performance was thoroughly investigated through simulations and experiments. The results indicate that this method demonstrates satisfactory measurement accuracy within the measurement range from 0 r/min to the maximum measurable rotation speed. The innovation of this method lies in using only a single line of fringe signal captured by LAS for sensing the rotation speed, which offers significant advantages in rotation speed sensing and computational efficiency compared to the area-array camera-based method. Moreover, the new speed encoding and estimation methods exhibit very high sensitivity and accuracy for very low and high rotation speeds. Compared to encoders based on pulse counting during a unit time or time interval estimation between two pulses, the proposed method provides higher temporal resolution and angular resolution for rotation speed measurement. Furthermore, this novel sensing method offers a nonintrusive approach that has no additional mass effect on the shaft, and it could be used for the development of a new kind of IRS sensor.

Rotating electrodes can effectively improve the processing performance of micro-electrical discharge machining (micro-EDM), but there is still a lack of systematic research on the specific effects of electrode rotation and rotational speed changes. In this paper, the effects of electrode rotation and rotational speed on the discharge channel, debris stress, and debris motion in micro-EDM were analyzed theoretically. An AISI304 sheet was used as the workpiece and helical tungsten carbide alloy as the electrode. The through-hole drilling experiments of micro-EDM were carried out at low and high discharge energy and different electrode rotational speeds. In terms of processing efficiency, the effects of electrode rotation and rotational speed on material removal rate (MRR), relative tool wear ratio (RTWR), and short circuit number were analyzed. The results show that MRR increases first and then decreases, RTWR and short circuit number decrease first and then increase. In the aspect of processing precision, the impacts of electrode rotation and rotational speed on taper angle and overcut were analyzed. The results show that the electrode rotational speed has little effect on the change of the taper angle. In addition, when the electrode rotational speed is small, there is no obvious change in overcut. When the speed is too high, the overcut increases obviously and shows a trend of continuous increase. Finally, by comparing the experimental results, the optimal electrode rotational speeds of micro-EDM with two kinds of discharge energy were determined. The final experimental results also verify the correctness of the previous theoretical analysis.

Dynamics of a powered disk in clay soil

Current studies on rotor dynamic response mainly focus on the unbalance forces caused by mass eccentricity, while little attention is paid to the rotary inertial moments caused by the skew angle of the principal axis of inertia. Especially for the rotors operating at high rotational speeds, the influence of rotary inertial moments on rotor response could not be ignored. Therefore, it is necessary to study the influence of rotary inertial moments on the rotor response and provide corresponding response suppression methods. This paper established a dynamic model based on the key structural characteristics of aero-engine high-pressure rotors. The excitations from mass eccentricity and skew of the principal axis of inertia are both considered. Numerical analysis was performed, which shows that the dynamic response excited by the unbalance force remains at a low level after passing the critical speed, however, the response excited by the rotary inertial moment increases continuously with the rotational speed, because of the self-centering of the principal axis of inertia at the high speed. Experiments are conducted on a test rig, results show that the decrease of local angular stiffness around the disk could reduce the influence of rotary inertial moments, eventually suppressing the dynamic response at high rotational speed.

The magnetic bearings described here has been developed for high speed rotating machinery. The manufactured experimental model is 4-axis-active type with simple structure. Since the model is so called outer-rotor type, resonance frequency of the rotor could set higher than rotating frequency, and only first resonance frequency of the stator shaft is in the rotating region. In this paper, we describe the analysis and experimental results to obtain stable high speed rotation. Firstly, stability of the gyroscopic motion of rigid mode is examined at low speed rotation. Subsequently, influence of flexibility of the stator shaft on stability is discussed. Then we indicate that nonlinearity of the power amplifier plays an important role in stability of the system. Finally, a suppression method using notch-filters and inter-axis cross coupling feedback at relatively high speed rotation is discussed.

Influence of welding parameters on intermetallic compounds formation in dissimilar steel/aluminum friction stir welds

In the industrial field, the drive system integrated the high speed motor and the gear is required to effectively utilize the limited space. However, mechanical gears often require their lubrication and cooling, they generate whilst noise and vibration. To overcome these problems, the magnetic gears have been expected. Magnetic gears achieve the system with maintenance-free, low noise and low vibration characteristics by contact-less power transformation. However, conventional magnetic gears are not suitable system for high speed motors because the mechanical strength is weak due to permanent magnets of the high speed rotor. Adding that, the magnet eddy current loss in the high speed rotor seriously decreases the gear efficiency in high speed drive. This paper presents a novel reluctance magnetic gear for the super high speed motor. The high speed rotor of the proposed magnetic gear is constructed by only iron core. Therefore, the structure is very simple and robust and it is possible to rotate in the high speed region. Moreover, the magnetic gear achieves high efficiency in the high speed region because the magnet eddy current loss in the high speed rotor is not generated because of having no magnets. The downsizing of the system and high efficiency power transfer are realized by applying the reluctance magnetic gear.

Currently, automotive products, especially two wheels (motorbikes), are equipped with an automatic transmission system. The type of automatic transmission used is CVT (Continously Variable Transmission). A roller is a material that is composed of Teflon as the outer surface and copper or aluminum as the inner layer. The function of the roller is to press the inner wall of the primary pulley during high rotation. RPM (Revolution Per Minute) is the number of rounds done in one minute. The purpose of this study is to determine the results of RPM on the effect of roller use and to determine the comparison of the effect of using a weight variation of a 13 gram (standard) roller and a 10 gram (racing) roller on the RPM of a 2015 Honda Beat FI motorcycle. 4 steps. The research method used is an experimental method, namely by starting the engine and holding the throttle at 1400-1500 RPM after stabilizing then the throttle is rotated spontaneously up to 9000-9500 RPM. The results of this study can be concluded that the 10 gram roller on the primary and secondary pulleys only get good acceleration and RPM at low rotation speeds. Whereas at high rotational speed the RPM acceleration is less than optimal.

This paper aims at the inner race dynamics of a high-speed ball bearing incorporated with Elastic Ring Squeeze Film Damper (ERSFD). Dynamic model of the inner race with three degrees of freedom (DOFs) is established in an ERSFD integrated ball bearing. Ball contact force and operating contact angle are characterized through an improved quasi-static model where the geometric relationship between the bearing displacement and elastic deformation is developed by considering the outer race movement. Numerical simulations were performed for bearings with or without ERSFD. The model was validated using Campbell diagram, measured displacement response and center trajectory of the inner race at different rotor speeds. The results show that the ERSFD provides adequate stable traction on the ball and limits excessive increase in the inner race contact angle. Such load-carrying condition benefits for decrease in ball orbital revolution skid at high rotor speeds. The ERSFD helps rotor unbalance force dominate bearing motion, leading to a stable periodic motion for the inner race at high rotor speeds. For ball bearings without ERSFD inner race possess stable motion at low and moderate rotor speeds, but is more prone to instability at high rotor speeds.