摘要:

The flow field in the inlet, mid- and exit planes of the pump of an automotive torque converter was measured using laser velocimetry. Three turbine/pump speed ratios (0.065, 0.600, and 0.800) were tested and average velocities are presented and analyzed. Data presented in this paper embody the most detailed velocity measurements in torque converters available. The highest through flow velocities generally occurred at the shell side of the blades in all measurement planes and at all speed ratios. For all speed ratios the flow entered the pump inlet plane with a velocity deficit occurring at the core side. The flow was able to become more uniform before it reached the mid-plane at the speed ratio of 0.065, while at the higher speed ratios the flow field demonstrated a large separation region at the mid-plane in the suction side/core quadrant. The flow field was more uniform in the exit plane at all speed ratios and separation was not observed. The secondary flow in the pump mid-plane is counter-clockwise. On the other hand, the secondary flow in the pump exit plane is clockwise. Rotational secondary flows were not observed in the inlet plane. The slip factor was determined at the mid- and exit planes and compared to predicted values for conventional centrifugal pumps. At the mid-plane the values compared well with previous correlations. However, at the exit plane the slip factors for the torque converter pump were higher than for a centrifugal pump. The torque distribution was found between the inlet and mid-planes and mid- and exit planes. The chord-wise distribution was uneven and more torque was delivered to the fluid between the mid- and exit plane.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982271

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Laser velocimetry was used to measure the flow field in the turbine and stator of an automotive torque converter. The data complements that of data in a pump at the same operating conditions. Average velocities are presented and analyzed in this paper for three turbine/pump speed ratios (0.065, 0.600, and 0.800). Data presented in this paper embody the most detailed velocity measurements in torque converters available. At all speed ratios and in all turbine measurement planes the highest through flow velocities generally occurred at the pressure side of the channel. At the turbine inlet a velocity deficit near the core was observed. This is due to the velocity deficit at the pump exit that transmits to the turbine inlet. At the lowest speed ratio flow entered the turbine with significant “pre-swirl” causing the flow to separate on the suction surface between the inlet and the mid-plane, resulting in a separation region in the core-suction quadrant. Strong circulatory secondary flows were not observed in the turbine planes as they were in the pump planes. The measured vorticity was highest at the inlet plane. The torque distribution was found between the inlet and mid-planes and mid- and exit planes of the turbine. The chord wise distribution was uneven and most of the torque was derived from the fluid between the inlet and mid-plane. The stator flow field is relatively uniform at the inlet at the highest speed ratio but much less so at the lower speed ratios. Some separation is seen at the lowest speed ratio at the inlet. At the highest speed ratio flow enters the stator with little incidence to the blades. At lower speed ratios significant incidence was measured resulting in separation on the suction surface. For the highest two speed ratios a significant separation region was observed at the exit plane in the suction/shell quadrant of the stator. The torque distribution was found between the stator inlet and mid-planes and mid- and exit planes. The total torque delivered to the working fluid at the 0.065 speed ratio is significant, indicating the presence of torque multiplication. At the 0.800 speed ratio the torque distribution between all planes is minimal, indicating minimal torque multiplication. The chord-wise torque distribution is relatively even.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982272

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A computational study was conducted to make comparisons regarding heat generation, frictional torque, and ball wear between conventional all steel bearings using M50 steel balls and hybrid bearings using silicon nitride (Si3N4) ceramic balls. Both were modeled using M50 steel races and the study was accomplished for radially loaded bearings only. Although most realistic applications also include axial loads on angular contact ball bearings, this study helps to recognize and quantify the performance increases of hybrid bearings due to slip and tractive rolling losses. Performance benefits for the hybrid bearings due to reduced centrifugal loads and the higher elastic modulus of silicon nitride balls are primarily demonstrated. Lubrication is assumed and reflected in the wear and friction coefficients, although hydrodynamic losses were nor accounted for. This configuration could occur with air/oil or grease lubrication or with dry lubricating films where environmental conditions might preclude the use of wet lubrication. Including hydrodynamic losses could be a future extension of this work. The predicted losses are calculated based mainly on the micro-slippage mechanism Poritsky (1) and elastic deformation mechanisms Johnson (2) in Hertzian contact regions. As part of the study, software was developed to predict micro-slippage, tractive forces, and traction coefficients between bearing races and balls. Energy losses (heat generation and torque) and wear rate are predicted for varying race curvature ratios and angular velocities. Predictions are for bearings with an outer race of 152.4 mm and ten 25.4 mm diameter rolling elements. Example calculations predict Si3N4, ceramic ball bearings reduce frictional losses over M50 steel ball bearings by approximately 20 percent and wear rates are reduced by about 50 percent.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982273

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper describes a systematic attempt to isolate various parameters that affect the material removal rate for diamond grinding of silicon nitride ceramics. The influence of different coolants and operating parameters such as force, depth of cut, and diamond grit size on the material removal rates under controlled conditions of single pass grinding is determined. Several parameters were developed to aid in interpretation of the grinding results. The parameters include grinding force coefficient, retained grinding efficiency, and instantaneous grinding rate. A grinding map concept was developed to allow rapid visual evaluation of grinding performance for a given coolant and a set of operating conditions.

ISSN:1040-2004    

DOI:10.1080/10402009908982274

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Hydrodynamic gas film bearings are used for supporting high-speed, lightly loaded rotating machinery. Stepped-type gas film bearings are often used for such machinery because of theïr simple structure, high stability and load carrying capacity. This paper describes the measurements of compressibility effects on the static and dynamic characteristics of stepped thrust gas film bearings. In the experiments, the minimum film thickness, friction torque on the bearing surface and stiffness and damping coefficients of gas films are measured for a range of rotational speed from 10,000 rpm to 20,000 rpm under a constant stator mass and a fixed step height. The measured data are compared with the theoretical results and the gas film compressibility effects on the static and dynamic characteristics of the bearings are discussed. The experimental results agree well with the predicted results based on the compressible lubrication theory.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982275

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A comparison of a computational model for flow and thermal analysis of a mechanical seal with experimental results is presented. The computational model adequately predicts the flow field in the seal chamber and temperature distribution within the stator of a mechanical seal. This model is used to determine Nusselt numbers on the wetted surfaces of the seal components. The Nusselt numbers can be used to calculate the temperature distribution on the seal face. Flow velocity and pressure, and temperature fields within the seal chamber fluid, stator and rotor are presented. The largest magnitude of the heat flux occurs on the rotor surface near the interface between the rotor and stator.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982276

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A general formulation of the instrumental variable filter (IVF) method for parameter identification of a n-DOF (Degrees Of Freedom) mechanical linear system is presented. The IVF is a frequency domain method and an iterative variation of the least-squares approximation to the system flexibilities. Weight functions constructed with the estimated flexibilities are introduced to reduce the effect of noise in the measurements, thus improving the estimation of dynamic force coefficients. The IVF method is applied in conjunction to impact force excitations to estimate the mass, stiffness, and damping coefficients of a test rotor supported on a squeeze film damper (SFD) operating with a bubbly lubricant. The amount of air in the lubricant is varied from nil to 100 percent to simulate increasing degrees of severity of air entrainment into the damper film lands. The experimental results and parameter estimation technique show that the SFD damping force coefficients increase as the air volume fraction in the mixture increases to about 50 percent in volume content. The damping coefficients decrease rapidly for mixtures with larger air concentrations. The unexpected increase in direct damping coefficients indicates the complexity of the SFD bubbly flow field and warrants further experimental verification.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982277

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Six additives were synthesized and evaluated as boundary lubrication enhancers for perfluoropolyalkylethers. These additives included a phosphate, a thiophosphate, a β-diketone, a benzothiazole, an amide/thiol and a sulfite. These additives were evaluated in a vacuum four-ball apparatus, at a one weight percent concentration in a perfluoropolyalkylether based on hexafluoropropene oxide. Tests were performed in vacuum (<6.7 × 10−4Pa), at room temperature (∼23°C), at an initial Hertzian stress of 3.5 GPa (200N load), and a sliding velocity of 28.8 mm/sec (100 rpm). Infrared (IR) and Raman spectroscopies were used to analyze the steel (AISI 52100) specimens after testing. Wear rates for each formulation were determined from the slope of wear volume as a function of sliding distance. All additives yielded reductions in mean wear rates of at least 50 percent, with the exception of the benzothiazole which had no effect. Two of the additives, an amide/thiol and a sulfite, reduced the mean wear rate by at least 80 percent. IR and Raman analysis indicated the severity of wear can be correlated to the amount of surface fluorinated polymeric acid species (RfCOOH) and graphitic amorphous carbon, in and around the wear scar.Presented as a Sociey of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

ISSN:1040-2004    

DOI:10.1080/10402009908982278

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In order to improve the lubrication between cam and follower of internal combustion engines, the influences of materials or oil viscosity and additives on the friction and scuffing characteristics have been examined with a test rig by increasing the contact load at a constant revolution speed. Also the effects of oil supply through the oil-hole of the camshaft on the reduction of friction and the prevention of scuffing have been examined. From the experiments the following results were made obvious.

ISSN:1040-2004    

DOI:10.1080/10402009908982279

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

One of the important issues in mixed lubrication is the contact problem involving frictional heating in the interface of contacting bodies. Due to contact and rubbing, temperature in the solid media varies, causing the contact conditions to change as a consequence of thermal distortion. A thermoelastic model for rough surfaces is developed for asperity contact subject to steady-state heat transfer. In this model, asperity distortion due to thermal and elastic-plastic deformations is considered. The thermal deformation is related to the contact pressure through a thermal influence function. Matrices for thermal and elastic influence functions are solved with the finite element method and the contact problem is computed with a mathematical programming method. Numerical analyses on the thermoelastic contact involving a rough surface reveal that asperity thermal distortion affects the contact pressure and surface separation at high frictional heat and deep asperity penetration.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982280

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor