bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration analysis of a misaligned rotor—coupling—bearing system passing through the critical speed
Authors: Prabhakar S , Sekhar A S , Mohanty A R
Published: October 2002

The transient response of a misaligned rotor—coupling—bearing system passing through the critical speed has been analysed by using the finite element method (FEM) for flexural vibrations. The coupling has been modelled in two ways: a frictionless joint and a joint with stiffness and damping. From the vibration analysis, the subcritical speeds at one-half, one-third and one-fourth the critical speed have been found when the misaligned rotor—coupling—bearing system passes through its critical speed. The continuous wavelet transform (CWT) has been used as a tool to extract the silent features from the time response of the rotor system. A parametric study has been carried out to investigate the transient response of this rotor system for different angular accelerations in different types of misalignment.
Two-dimensional finite element simulation of the thermal problem at railway block braking
Authors: Petereson M
Published: October 2002

Rolling noise levels from railways are strongly dependent on the roughness generated on the running surfaces of wheels and rails. As an initial effort concerning the wheels, a two-dimensional finite element (FE) model of the transient thermal convection-diffusion problem at block braking is developed. The streamline diffusion method is used to stabilize the solution. A constitutive law is adopted that describes the division of frictional heat between block and wheel. The model parameters are calibrated using available experimental data, and a sensitivity analysis is carried out. The results are in good agreement with experimentally obtained experience, especially regarding the division of frictional heat.
Three-dimensional inverse heat transfer analysis during the grinding process
Authors: Wang C-C , Chen C-K
Published: October 2002

A three-dimensional inverse analysis is adopted to estimate the unknown conditions on the workpiece surface during a grinding process. The numerical method (linear least-squares error method) requires just one iteration and can solve the inverse problems given only the temperature information at a finite number of locations beneath the working surface within a specified time domain. Results show that the heat source into the grinding zone and the heat transfer coefficient in the cooling region can be obtained by the proposed method even when under the influence of measured errors. Furthermore, it is found that the estimated heat transfer coefficient is more sensitive than the heat source to different measured errors and depths. Analyses of the temperature, heat distribution and heat transfer coefficient of the workpiece will help prevent the occurrence of thermal damage to the workpiece, which are caused by the high temperatures generated during the grinding process.
A model of the tension and transmission efficiency of a bush roller chain
Authors: Lodge C J , Burgess S C
Published: October 2002

This paper describes an improved chain link tension model for a simple two-sprocket roller chain drive. The model includes modified versions of previous models of the tension in the chain links, together with a new model for low-slack span tensions. The model allows the tension of a link to be calculated at any point in the chain drive more quickly and for a wider range of tight and slack span tensions than before. A new chain efficiency model is formulated, based on the losses due to sliding friction. Coupled with the chain link tension model, this can be used to predict the transmission efficiency of a chain. Experimental work undertaken on 0.5 in pitch industrial roller chains and bicycle chains has demonstrated that the chain efficiency model is accurate for moderate and high torque transmissions. At low torque, losses due to impact, adhesion and/or vibration become more significant and impair the accuracy of the model, particularly for heavier, industrial roller chains. The chain efficiency model enables certain design trade-offs to be carried out, such as the selection of the size of the overall system to achieve the right balance of transmission efficiency and weight.
A theoretical model for the contact of elastoplastic bodies
Authors: Li L-Y , Wu C-Y , Thornton C
Published: October 2002

The paper presents a theoretical model for the normal contact of a rigid sphere with an elastic-perfectly plastic half-space or an elastic-perfectly plastic sphere with a rigid wall. Formulae describing the force-displacement relationship for static contact problems and the coefficient of restitution for dynamic impact problems are derived. The present model can be considered as a modification of Johnson's model by using a more detailed pressure distribution function which is based on finite element analysis (PEA) results and considering the variation in the curvature of the contact surface during the contact interaction. In order to verify the theoretical model, finite element analyses are also conducted, and results are compared with those predicted by the model for both contact force-displacement relations and restitution coefficients. Good agreements between the model predictions and the FEA results are found.
Computer aided design of non-standard elliptical gear drives
Authors: Bair B-W
Published: October 2002

An oil pump with a larger pumping volume and more compact size than conventional pumps is designed with elliptical gear drives. In this work, an elliptical gear drive with few teeth is used in the design of pumps with a large pumping volume. Also, a mathematical model of a profile-shifted elliptical gear is developed, based on the theory of gearing and the gear generation mechanism. This study also investigates the tooth undercutting of a non-standard elliptical gear, based on the proposed mathematical model of the profile-shifted elliptical gear and the theory of gearing. Pointed teeth generally appear on the major axis of the gear elliptical pitch curve. Moreover, a geometric relation is developed and applied to prevent pointed teeth on non-standard elliptical gears. Moreover, a computer simulation program is developed to generate the tooth profiles of non-standared elliptical gears with few teeth and a compact size, without tooth undercutting and pointed teeth. Numerical examples demonstrate the effectiveness of the computerized design process.
Vibration analysis of single rigid-body systems having planes of symmetry
Authors: Dan B J , Choi Y J
Published: October 2002

By taking a geometrical approach to vibration analysis, the vibration mode shapes of a single rigid body may be better understood. From the geometrical point of view, the eigenvectors represent repetitive twisting motions on the axes of vibrations in a three-dimensional space. The frequency response can be expressed by a scalar multiple of the axis of vibration in Plücker's axis coordinates, which is the reciprocal product of the axis of vibration and applied force. The geometrical interpretation of the frequency response provides the design methodology to eliminate the undesired peaks. The methodology involves making the mutual moment of the axis of vibration and applied force become zero or adjusting the location of the axes of vibrations to the sensing point. In order to implement this geometrical design method, an optical pick-up used in the information storage device has been utilized. Some numerical results show design improvement concerning the frequency response of the pick-up device and thereby the validity of the design technique.
Solution of the conjugate heat exchange problem
Authors: Organ A J
Published: October 2002

An enduring challenge in the field of fluid mechanics and heat transfer has been to predict the response of a thermally conducting duct to transients in the flowing fluid. A coordinate transformation coupled with a change of dependent variable reduces a daunting exercise in Laplace transformation and Bessel functions to elementary numerical quadrature. The simplification makes it possible to advance beyond the canonical statement of the problem to variable particle velocity and variable pressure. The heat transfer coefficient and friction factor may vary in function of local instantaneous Reynolds number with negligible penalty on algebraic complexity.
Application of linear biphasic theory to finite element analysis of head impulse loading
Authors: Park H S , Yoon Y S
Published: October 2002

A finite element model of the human head by linear biphasic theory is developed to study the dynamic response of the human head to impact. Intracranial tissues are modelled as a binary mixture, i.e. the fluid and solid phases. To validate the biphasic finite element formulation, the result of the numerical analysis of a one-dimensional wave propagation problem is compared with that of analytic solution.

The permeabilities of the subarachnoid space and brain which may reproduce the same coup and contre-coup CSF (cerebral spinal fluid) pressures from the monophasic model are searched in the specified range of skull permeability. Then the intracranial pressure distributions from the biphasic model for the frontal impact are compared with those from the monophasic model. In general, the biphasic model produces a more injurious intracranial pressure distribution than the monophasic model. The pressure distribution from the biphasic model shows a little higher contre-coup pressure in the frontal lobe than in the occipital region. This finding is in agreement with those clinical findings that contre-coup injuries are more frequently found in the frontal lobe.

Another numerical simulation is conducted to characterize the effect of the volume ratios between two phases in the skull and subarachnoid space. From the results, it can be seen that the variation of the volume ratio in the subarachnoid space affects the intracranial pressure distribution of the lateral part while the variation in the skull does not.
Geometry and kinematics of multicable spreader lifting gear
Authors: Morrish L , Cartmell M P , Taylor A J
Published: October 2002

This paper presents a novel theoretical study of the geometry and derived kinematics of a typical multicable suspension system as encountered on a rubber tyred gantry (RTG) crane. Machines of this sort are used extensively in the international container handling business but, to date, little has been known about the precise motions of cable suspended spreaders other than general intuitions about fore—aft, lateral and rotational oscillations. Such motions are initiated by driver-controlled motion of the gantry itself (by torques applied to the driving wheels) and by across-the-vehicle motions of the trolley from which the spreader and container payload are suspended.

The work reported here shows the complete derivation for spreader coordinates, relative to the trolley, for any translational and/or rotational displacement. Conventional geometrical and trigonometrical principles are used throughout the development. This research forms an integral part of a larger programme of work to propose strategies for accurate spreader motion control based on non-linear dynamic models.
Synthesis of spherical four-bar path generator satisfying the prescribed tangents at two cusps
Authors: Chang C-F , Lu D-M , Hwang W-M
Published: October 2002

Design equations for spherical four-bar linkages to trace a coupler curve with two prescribed cusps are derived in this study by using a special case of spherical Burmester curves. For the case in which the tangents at two cusps are also prescribed, an analytical method is proposed with the aid of the foregoing design equations associated with the concept of the spherical cross ratio and spherical Bobillier theorem. The proposed method is straightforward and quite useful for those cases in which the tangents at two cusps are neither on the same plane nor on parallel planes. Numerical examples are also provided for illustrating the entire technique.
Classification of the rotating machine condition using artificial neural networks
Authors: McCormick A C , Nandi A K
Published: October 2002

Vibration analysis of rotating machinery can give an indication of possible faults, thus allowing maintenance before further damage occurs. Automating this analysis allows machinery to be run uattended for longer periods of time. This paper describes the use of neural networks as a method for automatically classifying the machine condition from the vibration time series. Several methods for the extraction of features to use as neural network inputs are described and compared. These methods are based upon measuring the zero lag higher-order statistics of the measured vibration time series. The time series for horizontal and vertical vibration signals are considered separately and combined to produce time series based upon the radius of the vibration displacement. The experimental set-up used for simulating unbalance and rub faults is described and classification success rates based upon each method reported. In particular, a classification success rate of over 99 per cent has been achieved.
Coagulation of particles in oil by an a.c. electric field (fundamental experiment)
Authors: Yanada H , Okumura R
Published: October 2002

This paper describes an experimental investigation of the coagulation of particles in oil under the action of an a.c. electric field. The investigation is carried out to acquire fundamental data to develop an electrostatic liquid filter with higher performance. The coagulation process of spherical silica particles is observed using a video-microscope with a CCD (charge coupled device) camera under various conditions and the effects of some mechanical factors such as the strength of the a.c. electric field, the velocity gradient of flow and so on are examined. The electric field is applied perpendicularly to the flow and particles are aligned in the same direction as the a.c. electric field by its action. The experiment shows that a certain frequency of a.c. electric field and a certain velocity gradient of flow exist which render the rate of coagulation maximum. It is pointed out that an interaction between the a.c. electric field and the flow field has a significant influence on the coagulation process.
Partial cancellation of shaking force harmonics by cam modification
Authors: Chiou S-T , Davies T H
Published: October 2002

An optimization procedure for minimizing the shaking force harmonics of machinery is described. Because of constraints imposed by the specification, optimization is unlikely to make any significant reduction in the fundamental, machine frequency, term of the shaking force. That term, normally the largest, must be substantially reduced by other means for the procedure described here to be cost effective. Earlier work describing methods of reducing the fundamental term are cited. An extrusion press machine incorporating two planar mechanisms, one crank driven and one cam driven, provides an example. Two designs of the cam-driven mechanism, referred to here as cams 1 and 2, are in use in installed extrusion press machines. Harmonic analysis of the shaking force as a function of time shows that cam 2 produces smaller amplitudes of shaking force harmonics. The ten variables used in the optimization process are the amplitudes and angles of the first five terms of a trigonometric series defining the acceleration of a reciprocating mass driven by a hypothetical third cam, cam 3, which is similar to cam 2 but stripped of all harmonics of order higher than the fifth. The objective function is the sum of the amplitudes of the horizontal components of the second to fifth shaking force harmonics on the machine as a consequence of accelerations of the moving parts of both mechanisms. Several equality and inequality constraints must be met. For the extrusion press machine the result is a reduction in the amplitudes that would be created if cam 3 were to be used by approximately 10, 75, 65 and 100 per cent respectively. The improvement over cam 1 is greater. The procedure is particularly suited as a retrofit measure where the number of installed machines is large in relation to the future rate of production of new machines: a cam that has been removed from one machine can be re-cut for use on another machine.
On the presence of bending stresses in inflated thin-walled structures
Authors: Chew G G , Howard I C , Patterson E A
Published: October 2002

It is proposed that, in appropriate circumstances, membrane structures can experience bending moments. On uniformly inflating a thin sheet structure, which has a shape consisting of multiple curvatures, the structure will deform in such a way that the final shape will have a single radius of curvature, assuming that failure does not occur. It is the large change of shape from a multicurvature surface to a single curvature surface that causes bending moments to exist within a membrane. The validity of the hypothesis has been demonstrated using four finite element models, including an elliptical cylinder, an ellipsoid, a ‘double’ cone and a trileaflet heart valve.
The influence of manufacturing tolerances on the kinematic performance of mechanisms
Authors: Fogarasy A A , Smith M R
Published: October 2002

The well-established theory of linear dimension and tolerance chains has been extended to include non-linear systems, such as linkage mechanisms, employing a technique based on the use of kinematic constraint equations. The results are interpreted with reference to production and assembly technologies and two examples are analysed to demonstrate the application of the technique.
The effect of friction on crack propagation in the dovetail fixings of compressor discs
Authors: Burguete R L , Patterson E A
Published: October 2002

Stress frozen photoelasticity has been used to model dovetail compressor blade fixings. During loading a known coefficient of friction was applied and the effect of the variation of this parameter on crack initiation and propagation was investigated. Data were recorded from the specimen using an automated computer aided polariscope based on the method of phase stepping. Isochromatic and isoclinic data were collected and used to determine the stress distribution, the stress intensity factor and the crack propagation direction. The method to predict the direction of crack propagation has been improved so that photoelastic data can be used reliably for this purpose. Three values of the coefficient of friction were used for two different dovetail geometries. It was found that the initial values of the mode II stress intensity factors were higher for a lower friction coefficient. An increase in crack length produced a corresponding decrease in the mode I stress intensity factor and a decrease in the mode II value. It was concluded that the coefficient of friction influenced crack growth at all stages of crack growth because it affects the relative levels of the mode I and mode II stress intensity factors. This has an effect on the direction of the maximum principal stress direction and so on the direction of crack propagation.
Buckling of curved panels under combined shear and compression
Authors: Featherston C A , Ruiz C
Published: October 2002

The analytical work which has been carried out to determine the buckling load and post-buckling behaviour of curved panels under various types of loading and different boundary conditions is not as comprehensive as that for flat plates. Only elementary loading and boundary conditions have been analysed. In addition to this, many of the theories developed have not been tested experimentally.

This paper outlines a series of tests carried out to determine the accuracy of the theoretical buckling loads. The experimental results are then used to examine whether or not finite element analysis can be used as an alternative to determine collapse loads and post-buckling behaviour, especially in cases where no theoretical solutions exist.
Estimating turbogenerator foundation parameters
Authors: Smart M , Friswell M I , Lees A W , Prells U
Published: October 2002

Turbogenerators in power stations are often placed on foundation structures that are flexible over the running range of the machine and can therefore contribute to its dynamics. Established methods of obtaining structural models for these foundations, such as the finite element method or modal testing, have proved unsuccessful because of complexity or cost. Another method of foundation system identification, using the unbalance excitation applied by the rotor itself during maintenance run-downs, has previously been proposed but has not yet been experimentally verified. In this paper the necessary theory is developed and certain issues critical to the success of the estimation are examined. The method is tested in both simulation and experiment using a two-bearing rotor rig and good fits between model and measurement are obtained. The predictive capacity of the estimated models when the system is excited with a different unbalance is not as good, and it is surmised that this may be due among other things to inaccurate bearing models.
Modal interactions in a frame under support motions
Authors: Tabaddor M
Published: October 2002

This paper presents the results from an experimental investigation into the planar, multi-mode response of a metallic portal frame to a harmonic support excitation. Forcing frequency and amplitude sweeps near the frequencies of the eighth and tenth modes of the structure revealed multi-mode responses. In the frequency interval surrounding that of the eighth mode, two additional lower-frequency modes, the fourth and the sixth, were excited. The mechanism responsible for the multimode behaviour of the frame is a combination internal resonance of the additive type. In addition, for a brief interval, a non-resonant interaction involving the eighth mode and the first mode was observed. Forcing amplitude sweeps for forcing frequencies below the eighth linear natural frequency produced a saturation-type phenomenon and a chaotically modulated motion. For the frequency interval surrounding that of the tenth mode, the response contained contributions from seven modes; these modes were excited through the simultaneous satisfaction of several internal resonance conditions.
Electromagnetic bearing actuator for active vibration control of a flexible rotor
Authors: Yu Z , Meng L T , King L M
Published: October 2002

This paper presents a detailed description of the electromagnetic actuator for active vibration control of a flexible rotor bearing system. The transfer characteristics of the electromagnetic actuator are investigated theoretically and experimentally. The linearized relationship of the electromagnetic force/input control voltage can be achieved by employing the analogue square root control circuits. A control algorithm which allows the control force of the actuator to be computed to minimize the synchronous rotor vibration is discussed. Computer simulation on a simple rotor bearing system is presented to demonstrate the effectiveness of the control algorithm in synchronous vibration reduction using the electromagnetic actuator.
Oscillations of liquids in single-outlet vessels
Authors: Kubie J
Published: October 2002

This paper considers the oscillatory behaviour of liquids in single-outlet vessels, i.e. vessels in which the outflowing liquid is replaced by another fluid which enters the vessel through the same opening. A theoretical model is developed and an equation for the natural frequency of oscillations obtained. The model is in good agreement with the available experimental data. It is shown that the natural oscillations of the liquid govern the hydrodynamic processes involved.
Vibration control of a flexible rotor/magnetic bearing system subject to direct forcing and base motion disturbances
Authors: Cole M O T , Keogh P S , Burrows C R
Published: October 2002

During operation, a rotor/magnetic bearing system may be subject to various sources of vibration, either directly applied to the rotor or transmitted through the bearings owing to base motion. This paper considers controller designs that are capable of attenuating vibration arising from either source. It advances the current state of research in the area since other controller designs have considered only the direct forcing case. If base motion is not considered in the design of the controller then this disturbance may cause the bearing clearance limits to be reached. Controller design is formulated as an H∞ optimization problem, with mixed design objectives. A new controller is derived that can simultaneously reduce vibration and minimize the effect of base motion on relative rotor to bearing displacement. Account is taken of the fact that the bearings can apply only limited control force. The design study was complemented by a programme of experimental work. The base of a rig was subjected to impulse inputs and the results show the effectiveness of the new controller design. It is demonstrated that proportional, integral and derivative (PID) controllers, or controllers designed for unbalance vibration attenuation only, may result in rotor contact with retainer bushes, while the new controller may prevent contact. The potential now exists for continuing safe operation of flexible rotor/magnetic bearing systems such as compressors, gas turbines, generators, etc., in transport applications, during seismic events or in environments with expected base input disturbances.
Accuracy of large eddy simulation for turbulent flow by the finite element method
Authors: Uchiyama T
Published: October 2002

This paper investigates the computational accuracy and CPU (central processing unit) time of large eddy simulation (LES) for turbulent flows performed by the finite element method. The investigations are accomplished by simulating a fully developed turbulent channel flow, which was analysed by Kim et al. using the direct numerical simulation (DNS) technique. When the advection term is discretized in gradient form, the turbulence decays and disappears with the passage of time. In using a multipass algorithm to solve the velocity field, the numerical result obtained by discretizing the advection term in divergent form agrees very well with that of the DNS. The multipass algorithm with the number of iterations k = 2 and 3 predict almost the same results. Thus, the algorithm with k = 2, allowing calculation with less CPU time, is successfully applicable to LES.
Effect of thread pitch on the fatigue strength of steel bolts
Authors: Dragoni E
Published: October 2002

The paper explores the effect of the thread pitch on the fatigue strength of ISO steel bolts fitted with standard nuts. By means of boundary element analyses and cross-comparison with theory and photoelasticity, the load capacity of the bolt is ultimately related to a comprehensive notch factor which embodies both stress concentration and notch sensitivity dependencies. The notch factor is conveniently plotted as a function of nominal diameter and thread pitch for a selection of steel grades. The charts show that the endurance load slightly increases as the pitch is decreased for small bolts of low-grade steel. Conversely, the endurance load markedly increases with the pitch (improvements above 40 per cent can be achieved) for large bolts of high-grade steel.
The simulation of gas dynamics in engine manifolds using non-linear symmetric difference schemes
Authors: Pearson R J , Winterbone D E
Published: October 2002

Symmetric difference schemes, such as the two-step Lax—Wendroff method or MacCormack's method, are used extensively in engine simulation codes in order to achieve second-order accuracy. These schemes, however, produce spurious oscillations when shock waves and contact surfaces are encountered and require the addition of non-linear terms (flux limiters) to cope with such phenomena. The paper reviews briefly the general theory behind the formulation of such nonlinear algorithms and examines the performance of two schemes in particular. The flux corrected transport (FCT) technique has been adopted by several research groups for this purpose and appears to operate satisfactorily for many flows in engine manifolds. It is shown in the present work that, under some circumstances, this method can distort the solution and produce large errors in mass conservation. The symmetric flux limiter due to Davis, based on the total variation diminishing (TVD) criterion, is shown here to avoid such problems and requires similar computational effort to the FCT approach.
Radial compressor design for industrial compressors
Authors: Dalbert P , Ribi B , Kmeci T , Casey M. V.
Published: October 2002

Industrial centrifugal compressors have a very large field of applications in chemical, petrochemical and gas transport applications with an enormous variety of gases, pressure levels and suction volumes. This paper describes the special design features of this type of compressor and sheds light on a method of standardization to overcome the large diversity of machine types. It reviews the aerodynamic and thermodynamic aspects in the design of impellers and diffusers, discusses the importance of the stage matching and illuminates the effect of stage components on stability.
On the performance of a cascade of turbin rotor tip section blading in wet steam Part 4: Droplet measurements
Authors: Bakhtar F , Rassam S. Y. , Zhang G
Published: October 2002

In the course of expansion of steam in turbines the state path crosses the saturation line and the fluid nucleates to become a two-phase mixture. These conditions can be reproduced under blow-down conditions by the equipment employed. This paper is the fourth of a set describing an investigation into the performance of a cascade of rotor tip section blading in wet steam and presents the results of droplet measurements which have been carried out by light extinction.
Measuring the kinematic accuracy of worm gears
Authors: Munro R. G.
Published: October 2002

A special-purpose machine has been designed and installed to measure the kinematic accuracy of precision worm gears. The primary measurement is the transmission error (TE) between the worm and wheel, and several measuring methods were considered. The chosen method uses optical gratings and a digital system to process the signals, which has particular advantages for this application. This method then makes it a straightforward step also to measure pitch errors of both the worm and the wheel, and lead errors of the worm. A novel method of measuring backlash very accurately is also described.
Flows and temperatures in compressor and turbine wheelspaces
Authors: Bayley F. J.
Published: October 2002

This paper sets out principles by which the turbomachine designer can determine the flows and hence the temperatures in the spaces between the rotating and stationary surfaces beneath, or inside, the mainstream annular flow region of axial flow machines. The geometry of these ‘wheelspaces’ ranges between slender single volumes of low hub-tip ratios to complex segmented regions of lower aspect ratio with large hub-tip ratios. Fluid temperatures in these spaces are determined by the supply of a secondary cooling air stream from near the engine axis, ingress of mainstream fluid from the external annulus, and leakage through the labyrinth glands separating axially adjacent wheelspaces. The paper uses the inviscid form of the momentum equation for rotating flows to determine the pressures in these spaces and simple Bernoulli principles to determine the corresponding flows and, from a heat balance, the fluid temperatures. Such a simplified analysis of what, in practice, are very complicated flow systems inevitably requires an input of empirical coefficients to define the flows, especially coefficients of discharge for the controlling restrictions in the rotating flows. There is a substantial amount of published data from deeper wheelspaces that yield a remarkably self-consistent set of coefficients. These are used to compare the predicted performance of sealing systems with observations, taking account of conditions in the external mainstream, including the effect of pressure perturbations and results from a full turbine stage. Similar predictions are made for stator wells, on which there is little relevant published information, although the critical flow parameters are apparent from the analysis.
A numerical analysis of vortex shedding within a confined channel flow
Authors: Scanlon T. J. , Stickland M. T. , Oldroyd A
Published: October 2002

The numerical analysis of two-dimensional laminar vortex shedding from a rectangular cylinder within a confined channel flow is presented. This study, carried out using a computational fluid dynamics (CFD) code based on the SIMPLEST algorithm, considers the influence of numerical diffusion on the prediction of the vortex shedding frequency. The computational analysis compares the commonly used first-order accurate UPWIND scheme with the well-known third-order scheme QUICK and its derivative SMART, used for the discretization of convective transport. For the temporal differencing, a fully implicit scheme has been adopted. Plots of Strouhal number against Reynolds number suggest that the implementation of a higher-order scheme is beneficial for the accurate capture of the vortex shedding transient in unsteady flows of this nature.
Analytical model of a particular type of positive displacement blower
Authors: Mimmi G , Pennacchi P
Published: October 2002

Many papers exist in the literature that deal with the twin-screw compressor. This usually has two different rotors, a male and a female, and is commonly used to produce compressed gas for industrial uses. However, a different type of positive displacement rotary compressor with two screws is sometimes used, one of its typical applications being in car engine supercharging. The present paper deals with the latter type, which is defined as a two-screw blower. This blower has two identical helical rotors, each with three lobes. The kinematics and the geometry of the rotors are analysed here, and a complete mathematical model for the rotor is defined. Moreover, different possible shapes of the rotors, depending on the design parameters, are analysed and the limitations in the choice of the design parameters are presented. Finally, an analysis of the theoretical specific slipping of the rotors is presented, showing which zones of the profile are the most stressed. This model will be useful for further studies on rotor pressure loads and blower dynamics.
Fuzzy logic controller for a vehicle active suspension system
Authors: Huang S-J , Chao H-C
Published: October 2002

An active suspension system has been proposed to improve the ride comfort. Its dynamic performance was investigated by using computer simulation results. A quarter-car 2 degree-of-freedom (DOF) system is designed and constructed on the basis of the concept of a four-wheel independent suspension to simulate the actions of an active vehicle suspension system. Since the mathematical model of this hydraulic actuating suspension system is non-linear and complicated, it is difficult to derive an accurate system model for designing a model-based controller. Therefore, a model-free fuzzy control algorithm is employed to design a controller for achieving vibration isolation. The experimental results show that the tyre deformation influences significantly the control performance of the active suspension system. Hence, a grey predictor is introduced to predict the tyre deformation and filter it from the feedback error signal. The control performance of this fuzzy control strategy with grey predictor is significantly improved.
Theoretical investigation into the use of controllable suspensions to minimize road damage
Authors: Kitching K. J. , Cole D. J. , Cebon D
Published: October 2002

This paper describes a theoretical investigation into the reduction of road damage through use of active and semi-active suspensions. Two new linear state feedback control strategies are described. These regulate aspects of the vehicle response that are believed to be closely related to road damage. Comparisons are made with two established control strategies. The relative performance of the four controllers is examined using a two-axle planar heavy vehicle model, with both active and semi-active suspensions.

Significant improvements are predicted for the three control strategies which account for correlation between the road roughness inputs at the front and rear of the vehicle, both for the active and semi-active suspensions. The state feedback preview control strategy previously developed by Sharp and Wilson [1] is found to give the best all-round performance for a suspension with semi-active suspension dampers.
Elastic foundation effects on the dynamic response of engine mount systems
Authors: Kim J-H , Lee J-M
Published: October 2002

This paper discusses flexible foundation effects on the dynamic response of engine mount systems using computer simulation techniques. The dynamic flexibility of the foundation is represented by a finite element modal model, and the equations of motions are derived for the engine mount system and foundation, which are coupled together. The developed computational method is applied to a Jeep-type passenger car, and the natural frequencies and forced vibration responses of an engine mount system can be simulated accurately. It is shown that the flexibility of the vehicle frame structure may have significant effects on the dynamic response of the engine mount systems, especially near the natural frequencies of the vehicle frame structure, and by applying the proposed method to the optimization routine it is also shown that improved optimization results can be obtained by considering the foundation flexibility.
Performance of an hydraulically restricted differential of a spur gear type
Authors: Dziama A , Golenko A
Published: October 2002

This paper presents the design of an hydraulically restricted differential of a cylindrical gear type and the results of its laboratory testing. In the differential, the externally meshing sections of the pinion gears were tightly sealed and employed for pumping action. A test stand was designed and a test programme established to evaluate the most important characteristics of the differential. It was concluded that the tested mechanism would be capable of developing the required level of resistance torque on condition that the vehicle was fitted with a hub reduction gear and the temperature of the oil did not exceed 50°C. The efficiency of a simple system of oil delivery was also controlled and assessed as satisfactory.
Study on the performance and emissions of a compression ignition engine fuelled with dimethyl ether
Authors: Wang H. W. , Zhou L. B. , Jiang D. M. , Huang Z. H.
Published: October 2002

The paper presents the research results of a light-duty direct injection diesel engine operating on dimethyl ether (DME). The effects of the main parameters of the combustion system, such as plunger diameter, nozzle type, fuel delivery advance angle, protruding distance of the nozzle tip from the bottom plane of the cylinder head and swirl ratio, on the performance of the DME engine are investigated. The indicator diagrams are taken after optimizing the combustion system and characteristics of combustion and emissions are measured for DME and diesel operation. The results show that, by adding a pressure pump in the fuel supply system, the vapour lock of DME in the fuel system is eliminated. The engine runs smoothly on DME over a wide range of speeds and loads. The effective thermal efficiency of the DME engine is 3 per cent higher than that of the diesel engine, and a low rate of pressure rise, low combustion noise, smokeless combustion and low NO x emissions of the DME engine can be achieved. The results demonstrate good characteristics in reducing emissions for a diesel engine operating on DME.
A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements
Authors: Reeves M , Taylor N , Edwards C , Williams D , Buckberry C. H.
Published: October 2002

The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.
A review of current sensor technologies and applications within automotive and traffic control systems
Authors: Turner J. D. , Austin L
Published: October 2002

This paper reviews the current practice in sensors and sensor applications for automotive and traffic control systems. Sensors to control engine fuelling, ignition and transmission (known as the powertrain) are reviewed, and the likely course of future development is discussed in the light of regulatory and market requirements as well as trends in sensor design and manufacture. Sensor needs for suspension, braking and traction control are also reviewed, and the likely introduction of wheel and tyre sensors to enhance driving safety is discussed. The recent trend towards vehicle-mounted devices to sense the vehicle environment (such as radar, optical, ultrasound, capacitive and image-based systems) is discussed, and the sensor implications of the introduction of safety-critical automotive systems such as adaptive cruise control (ACC) are discussed. Sensors for initiating the deployment of safety systems such as airbags are reviewed, together with transducers for disconnecting fuel pumps and vehicle batteries in the event of a crash. The paper includes a brief discussion of highway-based sensors for measuring vehicle speed and presence, and concludes with a discussion of the likely future developments in the field.
Safety of driver interaction with in-vehicle information systems
Authors: Stevens A
Published: October 2002

Advances in vehicle instrumentation are driven by customer demand, by the desire of manufacturers to add value and by technology that offers increasingly sophisticated and cost effective options. The range of information and communications equipment available to the driver has grown considerably over the past 5 years. Trip computers and radio data systems (RDS) are now standard on many vehicles, and the use of in-vehicle telephones has also increased. Other driver information products, such as congestion warning and route guidance systems, are becoming increasingly common.

Much development of in-vehicle information has, necessarily, focused on getting the technology to work. Now, as products are emerging, the real needs of drivers and their interaction with new systems is receiving much greater attention. The human-machine interface (HMI) is emerging as a key area that has a significant impact on the overall usability and safety of in-vehicle systems. This paper discusses HMI safety and how it is being addressed through standards, codes of practice and design guidelines.
Fluctuation analysis of M25 loop data
Authors: Rhodes C. J.
Published: October 2002

By calculating exponents relating to the flow velocity of traffic on the M25 motorway in the United Kingdom, evidence is given for scale-free behaviour in the dynamics of traffic at near-capacity flow. Specifically, it is demonstrated that during periods of high demand the flow is well described by a strongly antipersistent fractional Brownian motion. This approach to traffic flow analysis provides a robust and accurate quantitative characterization of the flow which can be used to inform choices of traffic flow prediction methods. Additionally, the quantities calculated here can be used to assess the performance of individual-based traffic simulation models which are finding increasingly widespread use as a means of understanding the impact of potential modifications to motorway networks.
Comparison of the Q3 and Hybrid III 3-year-old dummy head and neck response during side air bag loading
Authors: Duma S. M. , Crandall J. R. , Seki K , Aoki T
Published: October 2002

This paper presents the results of 20 tests designed to compare the head and neck response of the Q3 dummy and the Hybrid III 3-year-old dummy subject to loading by a deploying side air bag. In a static test environment, experiments were conducted in two positions using three seat-mounted thoracic side air bags that varied only in the level of inflator output. Substantial kinematic and kinetic differences were observed owing to differences in head geometry and mass, and neck stiffness between the two dummies. The Hybrid III head is 18 per cent heavier than the Q3 and resulted in peak head centre of gravity accelerations significantly lower ( p = 0.01) than those observed in the Q3. The stiffer Hybrid III neck resulted in 41 ± 29 per cent higher neck flexion moment compared with the Q3. While the stiffness properties for the Q3 neck are similar in all directions, the Hybrid III neck has preferred anterior-posterior stiffness properties. This difference was observed in tests where lateral loading of the head forced lateral bending in which the Hybrid III recorded a 101 ± 80 per cent higher lateral bending moment compared with the Q3. Although there is considerable uncertainty as to the validity of published injury criteria owing to the lack of child biomechanical data, these tests suggest that separate injury criteria are needed for each dummy.
Effects of fuels with a low aromatic content on diesel engine exhaust emissions
Authors: Ladommatos N , Xiao Z , Zhao H
Published: October 2002

Tests were conducted on a Co-operative Fuel Research (CFR) diesel engine using fuels with low aromatic content. The aim of the tests was to gain a better understanding of the way in which diesel fuel components affect exhaust emissions. A set of 14 diesel fuels was used, having aromatic content between 0 and 27 per cent; three of these fuels were oxygenated using diglyme and butyl-diglyme (diethylene glycol dimethyl either and diethylene glycol dibutyl ether). The results showed that the exhaust smoke and oxides of nitrogen (NO x) emissions correlated highly with the fuel monoaromatic content. When some of the fuel monoaromatic content was replaced by a diaromatic compound, there was a slight increase in exhaust smoke, but no clear effects on NO x and unburned hydrocarbon emissions. Oxygenated fuels showed lower smoke and NO x emissions. A statistical analysis of the CFR exhaust emissions suggested that the greatest influence on smoke emission was the fuel density, followed by the carbon-hydrogen mass ratio, 50 per cent distillation temperature and viscosity. A similar analysis suggested that the greatest influence on NO x was the 5 per cent distillation temperature, followed by density, 95 per cent distillation temperature, carbon-hydrogen mass ratio, 50 per cent distillation temperature, cetane number and viscosity. Finally, a high correlation was found between the engine exhaust emissions and the laminar flame-sooting tendency of some of the fuels.