bluuebunny/crossref_metadata_2025_split huggingface dataset:
Airbag head restraint system
Authors: Latchford J , Chirwa E. C. 
Published: October 2002

The function of a head restraint system is to prevent injurious hyperextension of the occupant's neck in the event of a road vehicle rear end impact, and thus it must have adequate stiffness to limit the movement of the head relative to the torso. Also, it should absorb the kinetic energy progressively so that the head does not sustain any injury and does not roll on the cushion. Practically, a well-designed head restraint will have an optimum balance of these features and thereby offer adequate protection for both the head and the neck. This paper presents some pioneering thinking on head restraint design and develops criteria for qualifying the systems. It presents an airbag head restraint system that has optimum stiffness and good potential for reducing head and neck injuries suffered through rear end collisions. It also presents the results of experimental tests conducted on this novel airbag head restraint system and on several randomly selected existing head restraints. Furthermore, analysis of energy absorption capabilities, head injury criterion (HIC) values and a new criterion, called the equivalent impact power criterion (EIPC), is developed in order to quantify the relation between the rate at which energy is imparted to the head during the impact cycle and injury severity. Current test results show that, the lower the EIPC, the better is the head restraint system and the less is the risk of whiplash and head injuries. Moreover, the work has quantified a number of variables, including the optimum stiffness, as the factors governing the severity of injury to the occupant in a rear impact scenario.
Measurements of cycle resolved air-fuel ratio near the spark plug in a spark ignition engine
Authors: Cho H , Lee J , Lee K 
Published: October 2002

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.
A new type of internal combustion engine based on the porous-medium combustion technique
Authors: Durst F. , Weclas M. 
Published: October 2002

At present, the emissions of internal combustion engines can only be improved by catalytic treatments of the exhaust gases. Such treatments, however, result in high costs and relatively low conversion efficiency. This suggests that a new combustion technique should be developed to yield improved primary combustion processes inside the engine with drastically reduced exhaust gas emissions. In this paper, the authors report on such a technique that is applicable to direct injection, internal combustion engines, either diesel or gasoline fuelled. This technique is based on the porousmedium (PM) combustion technology previously developed in the authors’ laboratory for steady state household and industrial combustion processes. It is shown that the PM combustion technique can be applied to internal combustion engines, i.e. it is demonstrated that improvements obtained in steady state combustion are also realizable in unsteady combustion processes. Theoretical considerations are presented for internal combustion engines, indicating that an overall improvement in thermal efficiency can be achieved for the PM engine. This is explained and the general performance of the new PM engine is demonstrated for a single-cylinder, air-cooled, direct injection diesel engine. Verification experiments are described that were carried out as part of the present study. Initial results are presented and an outlook is given on how the present developments might continue in the future.
Design of continuously variable power split transmission systems for automotive applications
Authors: Mucino V. H. , Lu Z. , Smith J. E. , Kimcikiewicz M. , Cowan B. 
Published: October 2002

The continuously variable power split transmission (CVPST) concept is presented in the context of an automotive application. The system consists of a variable pulley set (variator) coupling two of the three rotating elements of a planetary gear train, namely the sun and the ring gears. The arrangement is such that a ‘power split’ feature is attained in which the input shaft delivers power to the sun gear as well as to the driving pulley, which in turn drives the ring gear of the planetary through the variator. Because the input shaft delivers the input power at two locations (at the sun gear and at the driving pulley), the variator carries only a fraction of the total power flowing through the input shaft. The third rotating element of the planetary gear set (the planet carrier) collects the power flows from the ring and the sun gears, delivering the total power output to the vehicle. This feature allows an increased engine power envelope for potential automotive applications. This feature also reduces the power losses associated with power transmission, especially at the low speed-high torque modes, while providing continuously variable transmission ratio capability. A term dubbed the ‘cross-over coefficient’ is established which can be used to prescribe both the fraction of total power flowing through the variable element and the velocity ratio span for the transmission. An extension of this can be obtained by means of an external gearbox, allowing a stepless span in the optimum range of both engine and transmission. Design procedures are presented for an automotive application in which a stepless extension (synchronized variator) of the useful transmission ratio span is achieved by means of an external step-up gearbox. The two-stage system allows operation in the optimum range of both engine and transmission.
Sensitivity of rearward amplication control of a truck/full trailer to tyre cornering stiffness variations
Authors: Ei-Gindy M. , Mrad N. , Tong X. 
Published: October 2002

Highway safety and vehicle performance are two important considerations in the design of a heavy vehicle combination. In this paper a performance measure called the ‘rearward amplification ratio’ (RWA) is used as a control criterion in the design of a vehicle-handling controller. This approach is different to conventional control techniques. The RWA is defined as the ratio of the peak lateral acceleration at the rearmost trailer's centre of gravity (CG) to that of the lead unit during a lane-change manoeuvre. The vehicle under consideration is a six-axle truck/full trailer, which usually exhibits a high level of RWA leading to roll-over during obstacle avoidance manoeuvres. In this study, several control strategies are examined, namely active yaw control at the truck CG, active yaw control at the dolly CG and active yaw control at the trailer CG. These could be employed individually or in combination. The effect of an active control torque applied to various vehicle units is examined by using an optimal linear quadratic regulator approach combined with a simplified four degrees-of-freedom linear vehicle model. The controller performance index parameters are determined for the vehicle based on acceptable RWA target values. The sensitivity of the controller to tyre cornering stiffness variation is further evaluated. Simulation results indicate that the RWA can be reduced without significant change of the uncontrolled vehicle trajectory when active yaw torque is applied to the dolly. The controller can be more effective in improving the dynamic performance and roll stability of this type of commercial vehicle, if applied to the lead unit (truck) or to the last unit (trailer). However, the path of the vehicle will be strongly influenced and driving difficulties can be experienced. For active yaw control at the dolly CG, the optimal controller is found to be most sensitive to the dolly's tyres' cornering stiffness variations and least sensitive to steering axle from the RWA point of view. It is also found that the controller is most sensitive to steering axle parameter variations for path following.
Development of cavitation and enhanced injector models for diesel fuel injection system simulation
Authors: Lee H-K , Russell M F , Bae C S , Shin H D 
Published: October 2002

To expedite the application of fuel injection equipment to diesel engines, powertrain engineers are simulating the rate of injection with computer models. Many of the simple models give quite substantial errors if fuel cavitation in the high pressure system and the variations in bulk modulus with temperature and pressure are not included. This paper discuses cavitation and a companion paper discusses the treatment of non-linear bulk modulus. Diesel fuel injection nozzle hole size has been reduced and the injection pressures have been raised, to improve combustion, and the termination of the injection has been accelerated, to reduce carbon particle mass in the exhaust. High injection pressures and rapid termination set up very large hydraulic waves in the pipes and drillings of the fuel injection system, be it pump-pipe-nozzle or accumulator/common rail in type. The fuel momentum generated in these vigorous wave actions leaves such low pressures in parts of the system that vapour bubbles form in the fuel. Cavitation changes the bulk modulus of the fuel and the collapse of the cavities imparts sudden high pressure pulses to the fuel columns in the system and changes injection characteristics significantly. When modelling devices to control injection rate, the cavitation and non-linear bulk modulus have to be incorporated into the model. To this end, the concept of ‘condensation’ has been useful. The cavitated pipe section is divided into liquid and liquid + vapour mixture columns and modified momentum and mass conservation equations are applied separately. The model has been validated with a particular application of a rotary distributor pump to a high speed direct injection diesel engine, which is one of the more difficult fuel injection systems to model in which cavitation occurs at several operating conditions. The simulation results show the cavitation characteristics very well. This cavitated flow calculation model may be applied to other one-dimensional flow systems In addition, a more comprehensive injector model is introduced, which considers two loss factors at the needle seat and holes, sac volume, and viscous drag and leakage. This enhanced injector model shows some improvement at low load conditions
Characterization of automotive dampers using higher order frequency response functions
Authors: Cafferty S , Tomlinson G. R. 
Published: October 2002

Automotive dampers are an important element of a vehicle's suspension system for controlling road handling and passenger ride comfort. Many automotive dampers have non-linear asymmetric characteristics to accommodate the incompatible requirements between ride comfort and road handling, thus the ride comfort engineer requires techniques that can characterize this non-linear behaviour and provide models of the dampers for use in ride performance simulations of the full suspension system. The work presented in this paper is concerned with developing a frequency domain technique using higher order frequency response functions (HFRFs) to characterize a Monroe automotive damper. The principal diagonals and multidimensional surfaces of the HFRFs up to third order are obtained. Non-linear damping coefficients for the damper are derived from the HFRFs and the energy transfer properties are investigated. The results show that the majority of the HFRFs contain no peaks or resonances, indicating that the damper has no preferred frequencies for energy transfer. The accuracy of the damping coefficients determined from the HFRFs is poor. This is due to the inability of the technique to measure the pure HFRFs and separate the effects of non-linearities in the input actuator from those in the damper. It is concluded that these constraints currently impose some limit on the use of the methodology.
Sensing tyre pressure, damper condition and wheel balance from vibration measurements
Authors: Craighead I A 
Published: October 2002

The majority of disturbance and control forces affecting a vehicle are transmitted through the tyre-ground interfaces. For optimum performance, components at each wheel station should be regularly inspected and maintained. Failure to maintain tyre pressures at correct levels results in increased tyre wear, increased fuel consumption, reduced ride comfort and degradation of vehicle handling. Worn dampers also reduce ride comfort and are detrimental to handling. Unbalanced wheels lead to vibration and wear in steering linkages. A system is proposed which will monitor these parameters while the vehicle is being driven in the normal way. The system is based upon measuring the vertical vibration at each wheel/axle station. Subsequent signal processing enables a dashboard indication of tyre pressures, damper effectiveness and wheel unbalance to be made available to the driver.
The role of computer aided engineering in the design optimization of exhaust after-treatment systems
Authors: Konstantinidis P. A. , Koltsakis G. C. , Stamatelos A. M. 
Published: October 2002

The goals of employing computer aided engineering (CAE) tools have always been the improvement of product quality and the simultaneous reduction of the related time-to-market and development costs. The latter may be achieved when the optimization procedure is carried out without the need to construct and test numerous prototypes. CAE tools and methodologies, apart from the design phase, can also be employed for dedicated prediction and analysis purposes, with the intention to fully exploit the capabilities of the catalytic exhaust system. A set of fundamental CAE tools and the accompanying (CAE) methodology, aiming to assist the design optimization of catalytic exhaust systems for spark-ignition-engined vehicles, are presented. The set comprises the following individual cooperating modules: a transient exhaust system heat transfer code, a transient three-way catalytic converter (3W-CC) computer code with an accompanying kinetics tuning procedure, a 3W-CC database and an ageing assessment methodology. The CAE methodology may be exploited in the directions of exhaust system design and optimization, addressing the catalytic exhaust system as an entity that consists of interrelated components. In that context, specific examples of real practice are demonstrated. This methodology is already being extensively used by the authors in research and development of automotive exhaust after-treatment systems, with promising results.
Stresses and deformations in overlapped diesel engine crankshafts, Part 2: Evaluation of results
Authors: Bickley I , D'Olier V , Fessler H , Hyde T. H. , Warrior N. A. 
Published: October 2002

The extensive results presented in Part 1 (in the previous issue*) have been supplemented and analysed further. A large number of cross-sections which could be reasonably used to calculate nominal stresses has been listed and evaluated. An inclined (flat, rectangular) section through the web is shown to be the best to calculate nominal stresses due to torsion, pure radial bending and bending due to crankpin forces; its width is h (see Fig. 1), the length of the shortest line joining crankpin and journal fillets in the plane of symmetry. Stress concentration factors based on these nominal stresses show only modest scatter from single curves for crankpin and journal fillets for torsion and radial bending. Predictions using the most commonly used method underestimate shear stresses due to torsion and overestimate bending stresses.
Combustion analysis and cycle-by-cycle variations in spark ignition engine combustion Part 1: An evaluation of combustion analysis routines by reference to model data
Authors: Ball J. K. , Raine R. R. , Stone C. R. 
Published: October 2002

This paper investigates a number of new approaches to mass fraction burned analysis for application to spark ignition engine combustion processes. The rationale for these new approaches is to retain the simplicity and computational efficiency of the technique of Rassweiler and Withrow, but to overcome some of the limitations inherent in the standard methods. The approaches investigated include the use of a two-zone model to determine information about the burned and unburned gas temperatures and the modification of the standard Rassweiler and Withrow expression to incorporate polytropic indices for compression and expansion. The investigation makes use of an engine simulation model, which was used to generate the pressure data. This technique provided a ‘known’ burn rate against which to evaluate the methods investigated. Some experimental data taken from a Rover K4 optical access engine is also presented. The successful aspects of this investigation are the use of the Rassweiler and Withrow equation with different compression and expansion indices, and the application of this analysis to investigate crevice gas burn-up. What was found to be not successful was the use of a two-zone model for calculating gas temperatures. The results indicate that the model is, in general, not reliable for computing temperatures and this is due to the temperature gradient in the burnt zone and the disproportionately high rate of heat transfer from the mixture that burns first during combustion. The mass fraction burned calculations using this model were also found to be not as accurate as those based on simpler models.
Combustion analysis and cycle-by-cycle variations in spark ignition engine combustion Part 2: A new parameter for completeness of combustion and its use in modelling cycle-by-cycle variations in combustion
Authors: Ball J. K. , Raine R. R. , Stone C. R. 
Published: October 2002

This paper investigates a technique of calculating the completeness of combustion on a cycle- by-cycle basis. The technique introduces the normalized pressure rise due to the combustion parameter, ψ to describe the completeness of combustion. This parameter is based on the Rassweiler-Withrow method of calculating the mass fraction burned and is derived from the pressure-crank angle record of the engine. Experimental data were obtained from a Rover K4 optical access engine and analysed with a combustion analysis package. A computer simulation was then used to model the data on a cycle-by-cycle basis, both with and without the completeness of combustion parameter. The paper discusses the conditions under which it is suitable to model mean engine cycles, compared with the need to model cycle-by-cycle variability, and comments on the situations in which each type of modelling would be most appropriate. The engine simulation model is also used to investigate cycle-by-cycle variability of NO emissions that have recently been obtained experimentally. The successful aspects of this investigation are that the cycle-by-cycle variability in the completeness of combustion can be determined by use of the parameter ψ, that the inclusion of the completeness of combustion parameter improves the simulation's ability to model the experimental data both in a statistical sense (the coefficient of variation of the indicated mean effective pressure) and on a cycle-by-cycle basis and that cycle-by-cycle NO modelling results are found to compare well with experiment.
Engagement behaviour of a paper-based wet clutch Part 1: Influence of drive torque
Authors: Holgerson M , Lundberg J 
Published: October 2002

Owing to increasing demands when designing wet clutches for automatic transmissions, more knowledge about their behaviour is needed. In cars with power shifting automatic transmissions, an engine torque is continuously transmitted through the gear box. Most experimental and theoretical work concerning investigations of wet clutches today uses the inertia type of test apparatus, e.g. the SAE test machine 2. However, this type of test machine has no possibility of investigating the influence of a drive torque from the power supply. In order to investigate the influence of drive torque on wet clutch engagements, a new type of apparatus was built, which can operate with different combinations of inertia and drive torque. This apparatus can perform engagements more similar to those in automatic transmissions. The aim of this paper was to compare experimental outputs obtained using these principles of testing, concerning the influence of drive torque. It was found that the friction characteristics of wet clutches are independent of how the input energy is produced. This means that friction can be investigated with both principles. It was also found that an apparatus using only inertia gives shorter engagement times and higher temperatures than an apparatus including a drive torque at the same level of input energy. This can be explained by different power characteristics. Therefore, when investigating temperatures of wet clutch engagements, one must be careful when translating the results into reality.
Enhanced oil recovery using the rotating-disc skimmer
Authors: Najar A M , Turner J T 
Published: October 2002

It is now common practice to use disc skimming systems to recover oil floating on the surface of water. However, the performance of these devices is dependent on a large number of parameters and is certainly not understood completely. This paper describes a fundamental study in which experimental techniques have been developed to enable the performance of model skimmers to be measured. This has enabled the importance of the various parameters to be examined in a more systematic and detailed way than ever before. Based upon an improved understanding of the flow behaviour inherent in the oil collection process, a number of enhanced disc skimming systems are discussed. Results are presented for these systems to show the capabilities of the new forms of disc skimmer when operated as oil recovery devices.