bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes to the vortical and turbulent structure of jet flows due to mechanical tabs
Authors: Hui H , Kobayashi T , Wu S , Shen G
Published: October 2002

The effect of mechanical tabs on the vortical and turbulent structures in the near fields of jet mixing flows is investigated in the present paper. In order to compare the changes of the vortical and turbulent structures of jet flows with and without mechanical tabs, flow visualization and instantaneous quantitative concentration field measurements were conducted in a water channel by using a laser induced fluorescence (LIF) technique. The flow visualization confirmed the existence of a pair of counter-rotating streamwise vortices produced by each mechanical tab in a jet flow. The generated streamwise vortices can cause an inward indentation of ambient flow into the core jet flow and an outward ejection of core jet flow into the ambient flow. It also showed that the process of Kelvin—Helmholtz vortex pairing was accelerated, the small-scale vortical structure appeared earlier and a large-scale helical coherent structure was found in the near fields of tabbed jet flows. Based on the flow visualization and instantaneous quantitative concentration field measurements, two aspects of the effect of the streamwise vortical pairs induced by mechanical tabs on the jet mixing flows were suggested.
Elastic contact on a double-layered substrate
Authors: Kelly P. A. , Hills D. A. , O'Connor J. J.
Published: October 2002

Results are given for the contact law and state of stress induced in the contact resulting from application of a pressure distribution on a double-layered half-plane, or its indentation by a body of prescribed shape. The geometry is representative of that found widely in biomedical applications, particularly the knee prosthesis, and also in more general engineering problems. The solution is given in a numerically efficient form, and the stress states at the surface and within the structure that are associated with a number of different combinations of materials are displayed.
A full numerical analysis of hydrodynamic lubrication in artificial hip joint replacements constructed from hard materials
Authors: Jin Z. M. , Dowson D
Published: October 2002

A full numerical analysis of the hydrodynamic lubrication problem of artificial hip joint replacements with surfaces of high elastic modulus materials, such as metal-on-metal or ceramic-on-ceramic, under cyclic walking conditions is reported in this paper. The Reynolds equation in spherical coordinates has been solved for both entraining and combined entraining and squeeze film motions under a three-dimensional variation in both the load and the speed experienced in hip joints during walking. It has been shown that a finite lubricating film thickness can be developed during the walking cycle owing to the combined action of the squeeze film and entraining motions under some conditions. It has been found that the design parameters for plain spherical bearings, such as the femoral head radius and the radial clearance between the femoral head and the acetabular cup, have a large effect on the magnitude of the predicted lubricating film thickness.

Some interest has been shown in recent years in the performance of metal-on-metal bearings in which a dimple has been machined at the pole of the acetabular cup. It is shown that a dimple on the acetabular cup can significantly increase the film thickness throughout the walking cycle, particularly for relatively large depths and if the location of the dimple coincides with the direction of the resultant force acting on the joints. It is concluded that there is a good possibility that a full continuous hydrodynamic lubricating film can be developed in ceramic-on-ceramic hip joint replacements, and perhaps for some well-finished metal-on-metal implants with a relatively small radial clearance. For some metal-on-metal configurations, the effect of elastic deformation of the bearing surfaces must be taken into account in the lubrication analysis, particularly for a relatively large radial clearance.
Spectral indicators in structural damage identification: A case study
Authors: Brandon J. A. , Stephens A. E. , Lopes E. M. O. , Kwan A. S. K.
Published: October 2002

A pre-loaded cracked cantilever beam was excited vising a random vibration signal. Excitation levels were within the range of amplitudes that caused no suspicion of non-linear behaviour in an undamaged specimen of identical dimensions and material. Spectral signatures were acquired which made it possible to discriminate between open crack, closed crack and breathing conditions. Systematic effects relating to variations in resonant frequency were largely consistent with the literature for a lightly damaged beam but were unsupported for a beam with more severe damage.
Optimal selection of topologies for the minimum-weight design of continuum structures with stress constraints
Authors: Liang Q Q , Xie Y M , Steven G P
Published: October 2002

This paper presents a method for assisting the optimal selection of topologies for the minimum-weight design of continuum structures subject to stress constraints by using the performance index (PI). A performance index is developed for evaluating the efficiency of structural topologies based on the scaling design approach. This performance index is incorporated in the evolutionary structural optimization (ESO) method to monitor the optimization process when gradually removing inefficient material from the structure. The optimal topology can be identified from the performance index history. Various structures with stress and height constraints are investigated by using this performance index, which is also employed to compare the efficiency of structural topologies generated by different optimization methods. It is shown that the proposed performance index is capable of measuring the efficiency of structural topologies obtained by various structural optimization methods and is a valuable design tool for engineers in selecting optimal topologies in structural design.
A study on the numerical analysis of thermomechanical behaviour in a stud-to-plate laser braze joint
Authors: Park J-S , Na S-J
Published: October 2002

A mechanical analysis of stud-to-plate laser brazing was performed using the finite element method, and the transient displacement and stress fields in brazing workpieces were calculated. The materials used were small-diameter studs of AISI type 304 stainless steel, thin plates of Al 5052 aluminium and 88Al–12Si braze alloy for the filler metal. The mechanical analysis took account of the thermal aspects of brazing and the transient temperature fields were calculated using a brazing heat transfer model. An incremental plasticity model was employed for thermal elastoplastic analysis, which considered the temperature-dependent mechanical properties and the isotropic hardening effect of the materials. The numerical result showed that high residual tensile stresses remained in the middle of the braze gap, approaching the yield point of type 304 stainless steel. The permanent deformation of workpieces after the brazing was completed was minimal and confined to the area adjacent to the joint. Stress peaks were found to exist along the joining interfaces, which were due to mismatches in thermal and mechanical properties among the materials involved.
A more accurate method for predicting the stresses in a flat steel ribbon wound pressure vessel
Authors: Zheng J Y , Xu P , Wang L Q , Zhu G H
Published: October 2002

Flat steel ribbon wound pressure vessels have been adopted by the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 and Division 2. An excellent safety and service record has been built up in the past 34 years. Based on the interfacial friction model proposed by Zheng [1], a more accurate method for predicting the stresses in a flat steel ribbon wound pressure vessel is offered in this paper, taking account of the axial displacement, the change in the helical winding angle, the interfacial friction between ribbon layers and the effect of lamination. Comparison between experimental results of five test vessels with an inside diameter varying from 350 to 1000 mm, four different helical winding angles (18, 24, 27 and 30°), two width—thickness ratios of the ribbon (20 and 22.86) and results of calculation using the stress formulae available demonstrates that the method in this paper is more accurate and that interfacial friction gives a marked strengthening contribution to the axial strength of the vessel.
On the estimation of the fatigue cycle distribution from spectral density data
Authors: Petrucci G , Zuccarello B
Published: October 2002

This paper deals with the fatigue life prediction of components and structures subjected to random fatigue, i.e. to cyclic loading whose amplitude varies in an essentially random manner. In particular, this study concentrates on the general problem of directly relating fatigue cycle distribution to the power spectral density (PSD) by means of closed-form expressions that avoid expensive digital simulations of the stress process. At present, all the methods proposed to achieve this objective are based on the use of a single parameter of the PSD. In this work, by numerical simulations and theoretical considerations, it is shown that the statistical distribution of fatigue cycles depends on four parameters of the PSD and the methods proposed in the literature provide reliable results only in particular cases. The proposed approach lays the foundation for a more accurate evaluation of the fatigue cycle distribution. As a first result, a closed-form solution for the case of broad-band processes with narrow-band time derivative has been obtained in this paper.
Dynamic analysis of rotationally flexible cam mechanisms
Authors: Balkwill J D G , Morrey D
Published: October 2002

A novel mechanism for the actuation of valves in an internal combustion (IC) engine is described. Previous publications are reviewed and it is shown that the mechanism has received very little attention, in particular no dynamic analysis of it has been published. The mechanism features a shaft driving a cam through a coupling of sufficient rotational flexibility to permit significant angular offsets to develop during the cycle. A differential equation of motion of a simplified system is derived and solved using two methods. The theory requires a knowledge of twelve fundamental system dynamic parameters from which a prediction of angular offset of the camlobe throughout the cycle is produced.

A dataset was obtained from a purpose built apparatus which recorded the angular offset of the camlobe with respect to the camshaft for a range of rotational speed values. Results graphs are presented and the level of agreement between theory and experiment is discussed. The work demonstrates for the first time that useful predictions of simplified mechanism performance can be obtained from the model developed. Recommendations for further work in this area are made.
Technical Note: Investigation and improvement of the resistance against crack propagation for a hot steel rolling tool material
Authors: Tsubouchi K , Akiyama M , Yamamoto E , Mase T
Published: October 2002

Investigations were carried out on the resistance to crack propagation of a tool material for hot steel working. Observations on the tool used on a production line showed that cracks propagate alongside the meshy carbides. A hypothesis was then proposed which stated that crack propagation would be suppressed by changing the carbides into granular shapes. The key to realizing this idea was to heat treat the parent material manufactured by casting, which has never been done in this field. Among the trial and original materials, an appropriate one was selected through laboratory experiments and efficiency was verified on the production line.
Effects of sandpaper roughness and stream turbulence on the turbulent boundary layer
Authors: Gibbings J. C. , Al-Shukri S. M.
Published: October 2002

This paper reports experimental measurements of two-dimensional turbulent boundary layers over sandpaper surfaces under turbulent streams to complement the Nikuradse experiments on pipe flow. The study included the recovery region downstream of the end of transition. Correlations are given for the thickness, the shape factor, the skin friction and the parameters of the velocity profile of the layer. Six further basic differences from the pipe flow are described to add to the five previously reported.
Rotational sensorless scalar control of three-phase induction motors and its application to automotive electric power assist steering
Authors: Masrur M Abul , Hampo R. J. , Miller J. M.
Published: October 2002

A rotational position/velocity sensorless scalar control method for three-phase induction motors is described. Although voltage/frequency ( V/f) scalar control requiring such a sensor appears quite frequently in the literature, a general scheme without rotational sensors using a scalar method is not common. The method described in this work is simple in terms of algorithm and computationally less demanding, and hence can be implemented with inexpensive microprocessors. To illustrate an application, the electric actuator assisted power steering for automobiles is considered where torque is the object of control. For this particular application with near-zero or zero speed operation in general, the scalar method described in this work is considered to be a competitive alternative to the rotational sensorless field-oriented control (FOC) method for induction motors. This is particularly due to the fact that the algorithm for position sensorless FOC is computationally quite intensive for such low-speed torque tracking operations when compared with the scalar method, and in general requires expensive digital signal processors. Although this work was undertaken with automotive steering applications in mind, the methodology can also be applied to other automotive and non-automotive applications where actuators are used.
Performance of multicone synchronizers for manual transmissions
Authors: Abdel-Halim N. A. , Barton D. C. , Crolla D. A. , Selim A. M.
Published: October 2002

Theoretical performance equations are derived for multicone synchronizers which have replaced the traditional single-cone device in certain upmarket passenger vehicles. The equations are used to demonstrate the potential improvements in shift quality for a typical vehicle. Experimental studies of equivalent single- and triple-cone synchronizers within the same gearbox test rig are also reported for transmission oil temperatures ranging from cold start (0°C) to maximum operating conditions (75°C). The results confirm the overall much improved performance of the multicone synchronizer compared with the single-cone equivalent, except at low oil temperatures, where some difficulty in dissipating the oil from the multiple friction surfaces was apparent.
A study of exhaust noise in a motor vehicle using statistical energy analysis
Authors: Steel J. A. , Fraser G , Sendall P
Published: October 2002

This work uses statistical energy analysis (SEA) to study noise transmission through a commercial motor vehicle and in order to do this various sound and vibration power inputs associated with flanking transmission via the exhaust and engine noise are calculated. A modern commercial motor vehicle that has an exhaust noise sensitivity problem is studied in this work. The aim of this work is to demonstrate the application of SEA and to study the effects on noise transmission when the exhaust is incorrectly fitted (misaligned).

Airborne and structural paths for sound and vibration transmission to a vehicle saloon are considered. Also, the SEA framework is used to identify the relative importance of each structural and airborne power input in relation to the sound power that is transmitted to the vehicle saloon. It is shown that the importance of each sound power input varies with frequency. At low frequencies, sound transmission through the vehicle structure is most important. At high frequencies, airborne flanking noise transmission to the floor is important. In this case, exhaust vibration transmission is most important at frequencies between 250 Hz and 1 kHz when the engine is running at 5700 r/min, and the SEA model predicts the change in performance associated with exhaust misalignment.
Ambient temperature influence on catalytic outlet—inlet temperature difference
Authors: Botsaris P. N. , Sparis P. D.
Published: October 2002

The present paper investigates the effects of ambient temperature on catalyst efficiency monitoring via temperature measurements. This approach utilizes the raw data obtained from outlet-inlet temperature sensors and after a statistical treatment yields the necessary information about the catalyst level of efficiency. An increase in ambient temperature is accompanied with an increase in catalyst average efficiency. This is reflected by the outlet-inlet temperature difference of the catalyst which also increases linearly. The improvement in catalyst efficiency as a result of the ambient temperature effect is stronger for a new catalyst than for an older one. The present paper also describes an algorithm that takes into account this phenomenon for the diagnostic monitoring of catalyst performance.
Differential evolution based identification of automotive hydraulic engine mount model parameters
Authors: Kyprianou A , Giacomin J , Worden K , Heidrich M , Bocking J
Published: October 2002

Hydraulic engine mounts are commonly used in automotive applications, and numerical models exist for performing full-vehicle noise, vibration and harshness (NVH) studies by means of multibody simulation. The parameters of these models are usually determined by the manufacturer from first-principle numerical calculations, or by means of direct testing of the individual components. This paper describes, instead, a four-step identification method developed to determine the parameter values of a specific hydromount numerical model, the Freudenberg hydromount equations, a set of highly non-linear piecewise-continuous differential equations. The identification procedure is based on two concepts, the first being the use of the differential evolution algorithm for determining optimal parameter values, while the second is the use of data obtained from a series of experimental tests of progressively higher displacement amplitude. Identified parameters provide models whose mean square errors between the calculated output force time history and the experimentally measured force time history are typically of the order of 1-2 per cent.
Theoretical and experimental investigation into an adjustable automotive damper
Authors: Purdy D. J.
Published: October 2002

A non-linear model of an adjustable automotive damper is developed, which includes the compressibility of the fluid, trapped gas and expansion of the cylinder. The parameters for the model are selected by fitting the model to experimentally obtained data from the damper. The model is shown to give an excellent representation of the damper under investigation. The performance of the damper model is examined as the parameters are varied, and the results are discussed.
The effect of aromatic hydrocarbons and oxygenates on diesel engine emissions
Authors: Xiao Z , Ladommatos N , Zhao H
Published: October 2002

Tests were conducted in a Cooperative Fuel Research (CFR) diesel engine aimed at discerning the effects of fuel aromatic and oxygenate compounds on exhaust emissions. The base fuel was heptane to which were added increasing amounts of monoaromatic toluene and diaromatic methylnaphthalene. Blends of heptane and toluene containing oxygenated compounds (methanol, ethanol, heptanol and diglyme) were also tested. The results indicate that both toluene and methylnaphthalene increase smoke, oxides of nitrogen (NOx) and unburned hydrocarbon (UHC) emissions substantially. The results also showed that increases in ignition delay could account for some of these rises in exhaust emissions. The oxygenated fuel blends tested caused reductions in NOx and smoke emissions. The exception was heptanol, which showed no reduction in smoke emission. This may be associated with the fact that heptanol had the lowest amount of molecular-bound oxygen.
Recent advances in antilock braking systems and traction control systems
Authors: Austin L , Morrey D
Published: October 2002

Antilock braking systems (ABS) are closed-loop devices designed to prevent locking and skidding during braking. Traction control systems (TCS) limit the amount of traction force generated at the wheels to prevent loss of traction. Both systems contain an electronic control unit (ECU), which compares signals from each wheel sensor. In ABS systems, the pressure to one or more of the wheels is regulated, whereas in TCS systems, the drive torque to the wheels is reduced.

Recent advances include the use of wireless accelerometers, developments in the control software that take into account the dynamics of the tyres and suspension, the estimation of parameters such as lateral acceleration and wheel slip and the use of adaptive control and fuzzy logic. More recently, these systems have been integrated into other vehicle systems, such as four-wheel steering and active suspension. Future improvements might include the use of smart materials for sensor development, and the use of roadside-to-vehicle control.
The dimensional quality of sheet metal assembly with welding-induced internal stress
Authors: Shiu B. W. , Shi J , Tse K. H.
Published: October 2002

The present paper is the first to propose a minimum stress criterion for the minimum dimensional variation during sheet metal assembly. The weld sequence affects the dimensional variation owing to the welding process. A case study illustrates the minimum stress criterion on dimensional variation. This paper proposes a generic design criterion for sheet metal products and processes that would produce minimal stress-induced dimensional variation for spot-welded sheet metal assemblies. The process design proposes a minimum strees build-up by using the ‘sheet metal ironing welding technique’ in the weld sequencing design. The product design proposes a minimum stress build-up design criterion to manage the accumulation of stress. The proposed product and process design methods enable automotive body design engineers to create a quality product with minimum dimensional variation caused by the manufacturing stress within the body-in-white structure. Moreover, this facilitates the industry's objective of building a high quality automotive body with minimum stress. This is an important factor in contributing to the superior quality of the body panel fits. It also helps to reduce the quality-related warranty costs.

This paper primarily focuses on the development of a joint design guideline by exploring the relationship between the dimensional variation and the stress build-up. First, the automotive assembly process design will be introduced. A simple analysis of a one-dimensional assembly is produced. A three-dimensional structural analysis of a box assembly is investigated for the effect of stress build-up within a structure on the dimensional instability or variation. Then a three-dimensional finite element analysis of an assembly with weld sequencing of two imaginary parts is produced. An experimental industrial trial has confirmed the validity of the simulation methodology. Then a welding sequence design guideline is produced based on the previous simulation result, followed by a joint design guideline to help improve the design of dimensionally robust design.
Simulation and assessment of power control strategies for a parallel hybrid car
Authors: Paganelli G , Guerra T. M. , Delprat S , Santin J-J , Delhom M , Combes E
Published: October 2002

The aim of this paper is to propose a power control strategy for hybrid electrical vehicles. This strategy uses a fuel consumption criterion with battery charge sustaining. It is based on an instantaneous minimization of the equivalent fuel flow. Two comparisons are performed to evaluate the proposed strategy. The first one uses the loss minimization strategy of Seiler and Schröder [1], which appears to be realistic and efficient for real-time control. This strategy is also based on an instantaneous optimization and allows the battery state of charge to be taken into account. The second comparison is made with an optimal solution found for a given driving schedule. Although not realistic for real-time control, this solution is derived through a global optimization algorithm, the well-known simulated annealing method.
Prediction of the air-fuel ratio in transient conditions using a model of liquid fuel behaviour in the intake port of a spark-ignition engine
Authors: Cho H , Min K , Hwang S-h , Lee J-h
Published: October 2002

A wall fuel-film flow model is developed to predict the effect of wall fuel film on the air-fuel ratio in transient conditions in spark-ignition engines. Fuel redistribution in the intake port due to backflow and simple liquid fuel behaviour in the cylinder are included. Liquid fuel film flow is calculated for every crank angle degree using the instantaneous air flowrate. The calculated results are compared with the experimental results from a four-cylinder DOHC engine. The predicted results agree well with the experimental results. To maintain a constant air-fuel ratio for the rapid throttle opening/closing conditions and a cold start, the fuel injection rate control can be obtained from the simulation results.
Prediction of knock onset and the autoignition site in spark-ignition engines
Authors: Lee Y , Pae S , Min K , Kim E. S.
Published: October 2002

A three-dimensional model of knock is developed to predict knock occurrence and the autoignition site in spark-ignition engines. A premixed turbulent combustion model, which falls within the flame area evolution category, and a flame wall quenching model are applied to simulate flame propagation. A reduced kinetic model is used to simulate autoignition in the unburned gas region.

Engine experiments are performed to calibrate the reduced kinetic model and to verify the results of this modelling. A spark plug integrated pressure transducer and 11 ion probes are installed in the cylinder head to detect knock occurrences, flame arrival angles and autoignition sites.

The model predictions show good agreement with the cylinder pressures, flame arrival angles, knock occurrences and autoignition site of the engine experiments with the variations in spark timing.
Instantaneous friction components model for transient engine operation
Authors: Zweiri Y. H. , Whidborne J. F. , Seneviratne L. D.
Published: October 2002

An engine friction model is developed in order to determine the instantaneous friction components at any crank angle during the overall engine response. In order that it can be meaningfully incorporated in overall engine control models, the engine friction model should represent the relevant trends but be relatively simple to compute. The main friction components are the piston assembly, the bearing, the valve train and the auxiliaries. The model includes new analytically derived equations for the friction components of the ring assembly, the bearing with mixed lubrication and the valve train. Many factors contribute to the successful starting of diesel engines and one of them is the effect of engine friction due to high oil viscosity (cold start) on engine startability. The model takes into consideration the effect of temperature variations on the viscosity of the oil. The friction equations are based on theoretical calculations for hydrodynamic and mixed lubrication (where the oil film has collapsed). They rely on Reynolds equation and dynamic analysis. Simulation results are presented, which compared with experimental data indicate an accuracy of more than 97 per cent.
A comparison of the relative effects of fuel composition and ignition energy on the early stages of combustion in a natural gas spark ignition engine using simulation
Authors: Yossefi D , Belmont M. R. , Ashcroft S. J. , Maskell S. J.
Published: October 2002

Spark ignition engines operating on natural gas (NG) show advantages over petrol and diesel alternatives in terms of precatalyst emissions. However, such engines are affected much more than their petrol counterparts by the long combustion delay of the main fuel component, methane. The sensitivity of combustion delay to fuel/diluent chemistry means that this issue is exaggerated by the presence in the NG of variable concentrations of higher hydrocarbons and of inorganic components, arising from the worldwide variability of NG or from the use of exhaust gas recirculation.

The present article reports on a study using a large-scale three-dimensional simulation, incorporating computational fluid dynamics (CFD) and fully detailed chemical kinetics, of the early stages of NG combustion in a spark ignition engine. The focus is on comparing the relative influences of gas composition (i.e. the ethane content of the NG, and carbon dioxide in the oxidant/diluent) with the effects of ignition source location and energy on the early progress of the combustion. The results of the studies show that, although the presence of ethane enhances the combustion propagation rate and reduces delay time, and carbon dioxide has the reverse effect, the influences of the characteristics (energy and location) of the ignition source dominate over quite large changes in mixture composition. These findings have practical ramifications for the development of strategies for reducing combustion delay time in NG-fuelled engines.
Importance of inter-ring crevice volume as a source of unburned hydrocarbon emissions-numerical considerations
Authors: Kim C. G. , Bae C. S. , Choi S. M.
Published: October 2002

The influence of the inter-ring crevice, the volume between the top and the second piston rings, on unburned hydrocarbon (UHC) emissions has been numerically investigated with the aid of experimental results. The main goal of this study was to estimate the level of UHC emissions induced by the blow-up of the unburned gas trapped in the inter-ring crevice (inter-ring mixture). For this purpose, the relationship between the inter-ring mixture and UHC emissions was established from the experimental results. A physical flow model integrated with a ring dynamics model was constructed to predict the gas flows through the inter-ring crevice.

Calculated results showed that some of the inter-ring mixture returned to the combustion chamber, while the cylinder pressure fell below the inter-ring pressure late in the expansion stroke. The amount of inter-ring mixture returning to the combustion chamber after exhaust valve open was calculated and converted to the corresponding UHC emissions using the relationship between the inter-ring mixture and UHC emissions obtained from the experiments. The calculated level of UHC emissions caused by the inter-ring mixtures was 10-30 per cent of the entire UHC emissions over a range of speeds (1250—3500 r/min) and loads [185—556 kPa brake mean effective pressure (b.m.e.p.)]. The contribution was highest at the medium speed and medium load (2500 r/min and 432 kPa b.m.e.p.) for the test condition, which corresponds to the engine condition frequently required for normal running. These findings confirm the importance of inter-ring crevice volume in the UHC emissions in spark ignition engines.
Idle regulation strategies using stepper motor idle valves: Observation on engine simulator
Authors: Mahieu V , Leduc B
Published: October 2002

Engine control by electronic central unit (ECU) can be quickly described by information coming from sensors sent to the ECU, and by calculated and setting values sent to actuators by the ECU [1]. This paper describes idle regulation observations on an engine simulator, allowing an existing ECU, coming from an existing vehicle, to be emulated. Various submodels, such as starting models or road simulation models, allow idle pintle motion patterns to be generated. The paper shows what kind of idling strategies an engine control system has to take into consideration.
Simulation of a transient torque response for engine performance in a spark ignition engine
Authors: Cho H. , Song H. , Lee J. , Kauh S.
Published: October 2002

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes an inducted air mass model, a fuel delivery model and a mean torque production model. The inducted air mass model and fuel delivery model, considering the dynamic behaviours of air induction and fuel delivery, were proposed to predict the air-fuel ratio excursions under transient conditions. The mean torque production model reflects thermal efficiency, volumetric efficiency, friction and the effect of spark timing. In the spark timing model, knock limit and acceleration retardation are considered.

Experiments were carried out to validate the simulation model for step changes of the throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed conditions. Using this model, fuelling strategies were varied with open fast throttle while air-fuel ratio excursion and indicated mean effective pressure were predicted.
Development of an optimum design technique for the bus window pillar member
Authors: Kim M. H. , Suh M. W. , Bae D. H.
Published: October 2002

The body structure of a bus is generally assembled by using various spot-welded box members. The window pillar member is ordinarily built up with a T-type member. This is a very important member connecting the upper and lower structures of the bus body. However, it has been known that the T-type member has some problems such as high stress concentration, low fatigue strength and low structural rigidity. Because these problems cause degeneration of the performance and the durability of the bus body, there is a need to improve them. In this study, a new approach for optimum design of the bus window pillar member was investigated. Stress distribution and fatigue strength were estimated through finite element analysis and experiment. To optimize the shape of the outer gusset connecting the vertical and horizontal members of the T-type window pillar member, a B-spline was applied. To verify the results, stress analyses on the spot welding points, which were fatigue crack initiation points, were performed. It was found that the new approach could effectively alleviate stress concentration at the spot welding point and the outer gusset and improve structural rigidity. In particular, the new bus window pillar member designed through optimization has the following characteristics: (a) the configuration of the structure is very simple; (b) the fabrication process is not complicated in comparison with the current model.
Lateral dynamics and robust control synthesis for automated car steering
Authors: You S. S. , Kim H. S.
Published: October 2002

In this paper, lateral controllers are designed for the automatic steering of vehicles. The vehicle dynamics is derived for lateral motions of highway driving. To cope with various uncertainties, robust control synthesis using H∞-μ methodology is presented for a car moving along a curved path. A controller reduction technique is also introduced for implementation. The simulation tests reveal that the resulting lateral controller possesses the inherent advantages that are robust to mixed realcomplex uncertainties for typical driving manoeuvres. Finally, it can be concluded that the proposed control approach can significantly improve the stability and performance of an active car steering system.
A three-dimensional numerical study of the effect of pulsating flow on conversion efficiency inside a catalytic converter
Authors: Jeong S.-J. , Kim W. S.
Published: October 2002

A study is made of the flow and conversion characteristics of the pulsating flow of an automotive catalytic converter. To investigate the unsteady flow effects of a dual monolithic catalytic converter of double-flow type, a numerical methodology coupled with wave action simulation based on gas dynamic theory is developed. The flow inside the converter is treated as three dimensional, unsteady compressible and isothermal. Conversion rates through the monolithic channels are calculated under the assumption of being diffusion controlled. The present study indicates that this integrated numerical model successfully represents the conditions of severe interaction among the exhaust flows, the extreme filling and the empty processes that affect the flow distribution and conversion efficiency. The simulation results also show that the level of flow maldistribution in the monolith heavily depends on the curvature and angles of separation streamline of the mixing pipe that homogenizes the exhaust gas from the individual cylinders. It is also found that, on a double-flow converter system, there are severe interactions of each pulsating exhaust gas flow at the junctions, and consequently junction geometry greatly influences the degree of flow distribution.
Studies of NOx, CO, soot formation and oxidation from a direct injection stratified-charge engine using the k-ɛ turbulence model
Authors: Mansouri S. H. , Bakhshan Y.
Published: October 2002

In this investigation, a model has been developed to predict the performance and emissions—NOx, CO and soot—in a direct injection stratified-charge engine with a Texaco controlled combustion system. This model uses the k-ε turbulence model to determine characteristic velocities for heat transfer calculations and has only an empirical constant, by comparison with the Woschni equation in which separate constants are used for each process in the four-stroke cycle to determine the velocity for use in the Reynolds number. The modified Keck and Blizard model is used for combustion calculation by considering the rapid compression effects on the turbulence intensity. An extended Zel'dovich mechanism has been used to predict NOx emissions. To predict CO emissions, the Zeleknik and McBride models have been used. The model of Hiroyasu and Kodota has been used to predict the mass of soot formed and oxidized. Comparison of the model predictions with available experimental data shows a good agreement. Moreover, the program has a high flexibility for parametric studies to calculate the effect of engine parameters such as fuel-air ratio, engine speed, injection timing period and percentage of exhaust gas recirculation on the performance and emissions characteristics of the engine.
An investigation of intelligent cruise control laws for passenger vehicles
Authors: Yi K , Lee S , Kwon Y D
Published: October 2002

This paper describes intelligent cruise control (ICC) laws for passenger vehicles. ICC systems consist of a vehicle detection sensor, a controller and throttle/brake actuators. For the control of a throttle/brake system, a solenoid valve controlled electronic vacuum booster (EVB) and a step motor controlled throttle actuator have been used. A non-linear computer model for the electronic vacuum booster has been developed and the simulations were performed using a complete non-linear vehicle model. The proposed control law in this paper consists of an algorithm that generates the desired acceleration/deceleration profile in an ICC situation, a throttle/brake switching logic and a throttle/brake control algorithm. The control performance has been investigated through computer simulations and vehicle tests. The test vehicle is equipped with a millimetre wave radar distance sensor, an Intel 80C196 controller, a solenoid valve controlled EVB and a step motor controlled throttle actuator. The results indicate that the proposed throttle/brake control laws can provide satisfactory vehicle-to-vehicle distance and velocity control performance.
Non-linear time series analysis of combustion pressure data for neural network training with the concept of mutual information
Authors: Heister F , Froehlich M
Published: October 2002

In recent years, after a period of disillusion in the field of neural processing and adaptive algorithms, neural networks have been reconsidered for solving complex technical tasks. The problem of neural network training is the presentation of input/output data showing an appropriate information content which represent a given problem. The training of a neural structure will definitely lead to poor results if the relation between input and output signals shows no functional dependence but a pure stochastic behaviour. This paper is concerned with the identification of the most relevant input-output data pairs for neural networks, using the concept of mutual information. A general, quantitative method is demonstrated for identifying the most relevant points from the transient measured data of a combustion engine. In this context mutual information is employed for the problem of determining the 50 per cent energy conversion point solely from the combustion chamber pressure during one combustion cycle.
Hybrid modelling and simulation of the torsional vibration of vehicle driveline systems
Authors: Farshidianfar A , Ebrahimi M , Bartlett H
Published: October 2002

Vehicle drivelines are lightly damped non-linear systems possessing many degrees of freedom with dynamic interactions between the various subsystems. There are many sources of excitation such as torsional impact caused by the take-up of backlash in the power train system. Such sources of excitation exist in transmission backlash, in driveline splines and in pinion to ring gear contact in the differential. Abrupt application or release of the throttle in slowly moving traffic or rapid engagement of the clutch can be followed by noise and vibration responses referred to in the industry as ‘clonk’. This paper presents a method of modelling a vehicle driveline which can identify the phenomena known as ‘clonk’ and ‘shuffle’. This model is based on the assumption that vehicle drivelines can be considered as partially lumped and partially distributed, which for systems of this type is wholly appropriate. In doing this it is possible to derive an analytical solution to the governing equations, which has not been considered previously. The results from this model are compared with a totally lumped model of the vehicle driveline for comparison.
An experimental and finite element study of the torsional behaviour of T-joints in automotive structures
Authors: Lee M M K , Pine T , Jones T B
Published: October 2002

Single box sections and T-joints (two box sections joined together at right angles) are commonly used to represent automotive components, such as pillars and sills, in laboratory testing. In the work presented herein, the torsional properties of T-joints were determined both experimentally and numerically. A factorial-design test programme comparing adhesive-bonded and spot-welded T-joints was carried out. Numerical models, generated using a general-purpose finite element program and validated against the test results, were used to investigate further the behaviour of the connection between the two box sections in a T-joint. The joining technique and the joint eccentricity at the connection (the distance of the join from the vertical box section) were found to influence the torsional properties of T-joints. Finally, an automotive T-component was analysed to examine the applicability of the T-joint results to more complex components.
Performance simulations of engine-gearbox combinations for lightweight passenger cars
Authors: Soltic P , Guzzella L
Published: October 2002

This paper compares the fuel consumption of lightweight passenger cars with three different types of engine (one low speed and one high speed naturally aspirated spark ignited, one turbo-charged compression ignited) and two different types of transmission [continuously variable transmission (CVT) and automated gear drive]. All fuel consumption results are obtained using a quasi-static driving cycle simulator. The implemented models are described in detail. The engines are represented through their eficiency maps, which are obtained by scaling published data. Effciency of the transmission (CVT or gear drive) is modelled in dependence on speed, torque and gear ratio. The simulations show that low fuel consumption can be achieved with all those concepts. CVTs show similar results to automated gear drives. The CVT's theoretical advantage of operating the engine at its most fuel-efficient points is compensated by the relatively low efficiency.
Performance, emissions and wear characteristics of an indirect injection diesel engine using coconut oil blended fuel
Authors: Masjuki H. H. , Kalam M. A. , Maleque M. A. , Kubo A. , Nonaka T.
Published: October 2002

Dynamometer tests have been carried out to evaluate the performance, emissions and wear characteristics of an indirect injection diesel engine when fuelled by 10, 20, 30, 40 and 50 per cent blends of ordinary coconut oil (COCO) with ordinary diesel fuel (OD). The test was conducted for 100 h using each of the test fuels to monitor the effect of COCO blends on the wear and lubricating oil performance. OD fuel was also used for comparison purposes.

The operating performance of the engine and the emission characteristics of exhaust gases were compared. The effect of blended fuel on the engin's wear and lubrication characteristics in terms of wear metal (Fe), water concentration, oxidation, viscosity, total base number and additive depletion was analysed.

The performance and emissions characteristics results showed that 10-30 per cent coconut oil blends produced slightly higher performance in terms of brake power than OD. All the COCO blends produced lower exhaust emissions including polycyclic aromatic hydrocarbons and particulate matter. The wear and lubrication oil characteristics results showed that COCO blends up to 30 per cent produced similar results to OD. This programme will give useful information for further research and development in the future if COCO is used as an alternative to OD.
Case Study: Vibration analysis of a prototype of a small-scale high-speed generator for a hybrid electric vehicle
Authors: Lee S. U. , Besant C. B.
Published: October 2002

A series of high-speed generators (HSGs) for a hybrid electric vehicle is being researched at Imperial College. One of the key features of these products is their compactness (about 10 per cent of the weight of a comparable diesel generator set), making them highly portable. A brief description of an HSG is given here. In order to operate these generators safely, it is very important to be able to predict and analyse their dynamic behaviour. For this purpose, a systematic procedure is proposed to develop a finite element (FE) model to predict natural frequencies under operating conditions. In the procedure, the relationships between FE analyses, modal analyses and results of a running test are established. A prototype of a 100 kW HSG was made by adopting a new concept which used a hollow shaft to achieve very efficient cooling. Vibration analyses of the prototype using the proposed procedure were carried out. Finally, the results of computations and experiments for the prototype are presented and compared.
Estimation of instantaneous exhaust gas flowrate based on the assumption of a polytropic process
Authors: Shin Y. G.
Published: October 2002

Estimation of instantaneous exhaust gas flowrate is very useful in engine-related studies such as calculation of crank angle resolved mass flowrates of hydrocarbons, boundary conditions for exhaust gas flow study and so on. The study provides a simple but reasonably accurate tool to calculate the flowrates based on the assumption of a polytropic gas expansion process. The only information needed to calculate the flowrates is cylinder pressure. The polytropic exponent n is obtained from the logarithmic-scale plot of measured cylinder pressure. The calculated instantaneous mass flowrates of the exhaust gas confirm accuracy of within ±5 per cent except for low engine speed, compared with measured intake flowrates. The characteristics of the flowrates also show blowdown and displacement flow regimes typically observed in internal combustion engines.