bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new strategy for improving the warm-up performance of a light-off auto-catalyst for reducing cold-start emissions
Authors: Jeong S-J , Kim W-S 
Published: October 2002

Light-off catalysts are often used to minimize cold-start emissions. The improved coldstart performance of light-off catalysts (LOCs) needs the optimal design in terms of flow distribution, geometric surface areas (GSA), precious metal (PM) loading, cell density and space velocity (SV). In this study, these influential factors are numerically investigated using an integrated numerical technique by considering not only the three-dimensional fluid flow but also the heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading by depositing highly active catalyst materials upstream of the monolith is beneficial during the warm-up period, but its effect is severely deteriorated when the SV is above 100 000 h-1. To maximize light-off performance, this study suggests that: (a) the LOC be designed as a double-substrate type; (b) a substrate with high GSA and high PM loading at the face be placed at the front; (c) the cell density of the rear monolith be lower to reduce the pressure drop. In this paper, some initial results towards a new strategy of dual substrates are also reported to shorten the light-off time and improve conversion efficiency during warm-up. The proposed approach was very effective in reducing back pressure and cold-start emissions during the early seconds of engine operation.
Divergence analysis of an emissions-based air—fuel ratio model and exhaust oxygen estimation
Authors: Chan S. H. , Zhu J 
Published: October 2002

This paper claims that, instead of relying on direct fuel and air flowrate measurements, exhaust gaseous emissions analysis should be considered as the standard method for the determination of time-resolved air—fuel ratio (AFR), in particular for petrol powered engines. Various sensitivity parameters are defined and the maximum possible relative divergences of the air—fuel ratio are calculated to support the above claim. It is proved that to obtain the air—fuel ratio with the same order of accuracy for a petrol engine near stoichiometric conditions, the resolution of the instruments used for fuel and air flowrate measurements should be at least ten times more accurate than the emission analysers. Estimation of oxygen concentration is also conducted based upon other measurable emission constituents, viz. oxides of carbon (COx) and hydrocarbons. Two methods are proposed, one depends on known air—fuel ratio whereas the other one does not require that the air—fuel ratio is known. Estimation of oxygen concentration using the former method is not affected essentially by the effect of the presence of water vapour in the analyser on the measured emission constituents.
Automotive active suspensions Part 2: Practical considerations
Authors: Williams R A 
Published: October 2002

Part 1 of the paper demonstrated the compromises required in suspension design brought about by the conflicting demands of ride and handling, and the constraints applied by the need to minimize body acceleration within a limited suspension travel. It then went on to show how a state feedback controller can be used to provide improvements in ride which are not achievable with standard passive components. This second part discusses the hardware employed, which ranges from simple switched dampers, through semi-active dampers, and low-bandwidth/soft active suspensions, to high-bandwidth/stiff active suspensions. The benefits to be derived from each of the technologies is assessed, together with the practical implications.
Three-way catalyst assessment via outlet—inlet temperature measurements: Driving tests
Authors: Sparis P D , Botsaris P , Karkanis A , Tatsios J 
Published: October 2002

This paper presents and discusses experimental data obtained during driving tests simulating the test cycle, ECE 15, and relates exhaust gas levels of hydrocarbon (HC) and carbon monoxide (CO) to catalyst outlet—inlet temperature differences. It also presents the preliminary results from the operation of a microcontrolled on-board diagnostics (OBD) II catalyst efficiency assessment system based on a statistical analysis of the catalyst outlet—inlet temperature difference thermocouple signal. There are indications that this system performs satisfactorily after an adequate warm-up period, if a sampling period in the order of 300—400 s is allowed. Although this operating principle is supported by considerable experimental evidence, there are several technical problems that must be overcome before it can comply to the OBD II requirements. Firstly, as engine loads increase, the efficiency of all catalysts tested is improved considerably by the high exhaust gas temperatures. Furthermore, as the catalyst outlet—inlet temperature difference tends to decrease, so does the sensitivity of the measurements. During driving, catalyst outlet—inlet temperature differences could also be affected by other external factors such as the car speed, rain or snow etc., or long-term temperature sensor drift. Present results indicate that catalyst outlet—inlet temperature difference is also influenced by the ambient temperature. A preliminary analysis of the data indicates that a linear relationship may exist between these two quantities, however, more tests are required for a statistical proof of this assertion. In spite of these problems, the results presented here tend to support the idea that a catalyst performance assessment system using temperature probes is technically feasible. However, further tests are required under various engine operating conditions and environments before a final conclusion can be drawn.
Thermodynamics in a turbocharged direct injection diesel engine
Authors: Chan S H 
Published: October 2002

Software has been developed for the calculation of the thermodynamic cycle and the entropy changes in a turbocharged, direct injection, diesel engine based upon the measured cylinder pressure and a shaft encoder output. Assumptions of homogeneous mixture and equilibrium thermodynamic properties are made for the products of combustion and the temporal variation in the fluid thermodynamic state is followed in a quasi-steady manner through a series of adjacent equilibrium states, each separated by finite intervals of one degree crank angle (1°CA). The thermodynamic properties are calculated by either of two equivalent formulations — equilibrium constants or minimization of Gibbs free energy, and are expressed in algebraic equations for the partial derivative of internal energy and gas constant with respect to temperature, pressure and equivalence ratio. The effect of the engine operating conditions on the thermodynamic cycle is studied. Results show that the dynamic fuel injection timing and hence the ignition delay are strongly influenced by the operating conditions, and this explains the reasons for incorporating a fuel injection control system in modern vehicular engines for the optimization of the engine combustion cycle.
The effects of carbon dioxide in exhaust gas recirculation on diesel engine emissions
Authors: Ladommatos N , Adelhalim S M , Zhao H , Hu Z 
Published: October 2002

The investigation was conducted on a high-speed direct injection diesel engine and was concerned with the effects of exhaust gas recirculation (EGR) on diesel engine combustion and emissions. In particular, the effects of carbon dioxide (CO2), a principal constituent of EGR, on combustion and emissions were analysed and quantified experimentally. The use of CO2 to displace oxygen (O2) in the inlet air resulted in: reduction in the O2 supplied to the engine (dilution effect), increased inlet charge thermal capacity (thermal effect), and, potentially, participation of the CO2 in the combustion process (chemical effect). In a separate series of tests the temperature of the engine inlet charge was raised gradually in order to simulate the effect of mixing hot EGR with engine inlet air. Finally, tests were carried out during which the CO2 added to the engine air flow increased the charge mass flowrate to the engine, rather than displacing some of the O2 in the inlet air. It was found that when CO2 displaced O2 in the inlet charge, both the chemical and thermal effects on exhaust emissions were small. However, the dilution effect was substantial, and resulted in very large reductions in exhaust oxides of nitrogen (NO x) at the expense of higher particulate and unburned hydrocarbon (uHC) emissions. Higher inlet charge temperature increased exhaust NO x and particulate emissions, but reduced uHC emissions. Finally, when CO2 was additional to the inlet air charge (rather than displacing O2), large reductions in NOx were recorded with little increase in particulate emissions.
Simulation models for hybrid buses
Authors: Berta G L , Durelli E , Nymann I 
Published: October 2002

Design and production of hybrid buses in Italy are assisted by a range of engineering tools that enable simulation and optimization of the hybrid bus performance. A review of these tools is given, involving the study and development of typical driving patterns and behaviour, the mathematical models of the components in the hybrid powertrain and, finally, the application of the computer codes. Initially simulation is a design tool. Moreover, it is found that simulation is useful for verifying the suitability of hybrid buses for the required service. By means of more or less complex algorithms, customers can be advised to adapt bus lines and to adjust powertrain parameters.
A new total variation diminishing scheme for the calculation of one-dimensional flow in inlet and exhaust pipes of internal combustion engines
Authors: Vandevoorde M , Vierendeels J , Dick E , Sierens R 
Published: October 2002

Total variation diminishing (TVD) schemes have been recently introduced for the calculation of the one-dimensional unsteady flow in the inlet and outlet pipes of internal combustion engines. This paper describes the flux difference splitting technique (with first- or second-order upwind fluxes) for the classic TVD schemes. To avoid problems at nodes with a section change, a new TVD scheme is developed. This paper further describes a method to impose the boundary condition at the pipe end, independent of the numerical scheme used. This is shown for a reservoir inlet of the pipe and a subsonic outlet flow. For two test cases (the shock-tube and the tapered-pipe calculation), the new TVD algorithm is compared with the classic TVD schemes. The evaluation shows that the new cell—vertex TVD scheme with superbee limiter in two stage form combines a high accuracy with an exact representation of the mass flow in each of the nodes.
Evaporation of hydrocarbon compounds, including gasoline and diesel fuel, on heated metal surfaces
Authors: Fardad D , Ladommatos N 
Published: October 2002

An investigation was carried out on the evaporation of various hydrocarbon liquids on heated surfaces. Single and multicomponent hydrocarbon compounds were used, including hexane, heptane, octane, a hexane—octane mixture, gasoline and diesel fuel. The heated surfaces included aluminium, mild steel, cast iron and copper. Tests were also carried out with different surface textures and surface coatings. The motivation for this work was a desire to improve understanding of the evaporation processes taking place in the inlet port and, to a lesser extent, within the combustion chamber of internal combustion engines. The hydrocarbon compounds were released on to the heated surfaces as individual small droplets, and the subsequent evaporation was recorded using a CCD (charge coupled device) camera. These observations were then used to ascertain the effects of material, surface temperature, surface texture, surface coating and liquid composition on the heat flux and other aspects of droplet behaviour.
Pipeline system identification through cross-correlation analysis
Authors: Beck S B M , Williamson N J , Sims N D , Stanway R 
Published: October 2002

The pipeline systems used to carry liquids and gases for the ventilation of buildings, water distributions networks, and the oil and chemical industries are usually monitored by a multiplicity of pressure, flow, and valve position sensors. By comparing the input signal to a valve with the pressure reading from the network using cross-correlation analysis, the technique described in this paper enables a single sensor to be used for monitoring. Specifically, the offset and gradient change of the cross-correlation function show the time delay between the input wave and the acquired output signal. These reflections arise from junctions, valves, and terminations, which can be located effectively using the cross-correlation technique. Investigations using a T-shaped pipe network have been conducted with a valve inserted in the pipeline to introduce artificial water hammer-type perturbations into the system. Both computational and experimental data are presented and the results are compared with the actual pipe network geometry. It is shown that it is possible to identify the location of various features of the network from the reflections and thus to perform either system characterisation or condition monitoring.
Velocity measurements in a ceramic candle filter element undergoing pulse cleaning
Authors: Biffin M , Panagiotidis P , Pitsillides C 
Published: October 2002

Ceramic candle filters have been developed for cleaning high-temperature gas streams. They have demonstrated high collection efficiencies under normal operating conditions, but the brittle materials can fail suddenly with disastrous consequences. Reverse pulse cleaning has been shown to introduce severe thermal stressing of the material. Modelling of the flows to estimate the life of the element is difficult due to non-uniformities in the material. It is important to obtain experimental measurements of flows in the candle to provide input to stress models. In addition it is essential to ensure uniform cleaning of the filter and knowledge of the pulse cleaning flow processes are also important for this. This paper reports velocity measurements obtained using a hot-wire probe located at different positions along the length of a ceramic candle filter. The data have been analysed to estimate the outflow along the length of the candle filter to investigate the cleaning potential of different configurations and operating parameters. The effect of pulse length on cleaning performance was investigated for cases with and without a venturi educer. It was found that the maximum peak mean velocity was produced at a pulse duration of 0.2 s. Longer duration pulses did not have a significant influence on the maximum velocity levels inside the filter.
Fault diagnosis of pumping machinery using artificial neural networks
Authors: Ilott P W , Griffiths A J 
Published: October 2002

Pumping costs within British industry are enormous, with the potential for considerable financial savings through fault diagnosis and condition-based maintenance. Accurate condition monitoring data interpretation is a key requirement in pump fault diagnosis. However, the human skills required to transform monitored data into maintenance information are often unavailable. Artificial neural networks (ANNs) are proposed for automation of this skill in the development of a pumping system decision support tool, the key requirement of which is accurate pump fault diagnosis. The cumulative sum charting procedure was used to establish a knowledge base of fault data for ANN implementation based on historical parameter measurements. Various preprocessing techniques were investigated in relation to generalization ability and convergence rates during the learning phase. Preprocessing predominantly aVected ANN convergence rate, with the quality of training data crucial to generalization ability. ANNs could provide accurate, incipient fault diagnosis of pumping machinery based on real industrial data corresponding to historical pump faults.
Detection of incipient cavitation in pumps using acoustic emission
Authors: Neill G D , Reuben R L , Sandford P M , Brown E R , Steel J A 
Published: October 2002

This work concerns the detection of incipient cavitation in pumps using acoustic emission (AE). Three activities have been pursued in this context: (a) the construction of a small-scale rig for the investigation of cavitation detection using AE sensors; (b) the acquisition of data on a 75 kW single-stage centrifugal pump in an industrial test loop under normal running and cavitation conditions; (c) the determination of parameters that could be used for the early diagnosis of cavitation within pumps. In the laboratory-scale apparatus water was pumped around a short loop by a 3 kW centrifugal pump. The flow loop contained a section specifically designed to induce cavitation by means of reducing the pressure level to that of the vapour pressure of the fluid. This apparatus was used to produce a variety of well-controlled cavitation conditions which were useful in determining the suitability of AE for the detection of cavitation. The industrial-scale tests consisted of progressively reducing the net positive suction head in a 75 kW pump while recording the AE signals at various points on the test loop and pump. Results are presented from both laboratory and full-scale tests which demonstrate the feasibility of detecting incipient cavitation using AE in the face of background noise from normal running of the pump. The features of AE which are indicative of cavitation are also seen to change continuously as NPSH is decreased. Thus early detection of cavitation is possible, certainly before any indication is seen on the dynamic head.
Process plant condition monitoring and fault diagnosis
Authors: Sharif M A , Grosvenor R I 
Published: October 2002

The paper reviews current research work in the field of process condition monitoring and fault diagnosis. The review compares and contrasts the applicability and efficiency of different techniques, and concentrates on methods which monitor the main process variables. From the wide range of methods and process variables, temperature, flowrate and liquid level are used here in comparing the limitations and applications of each method. The scope of the paper ranges from basic, well established techniques to the latest reported monitoring strategies for each of the process variables. Furthermore, the different methods of fault diagnosis deemed to be relevant in process plant are reviewed. The detection of the internal leakage in the control valves and motor faults are discussed in detail, as examples of the monitoring of vital process plant components. The paper then outlines areas of future work, such as the development of a user friendly interface. This interface is based on state transition diagrams (STDs) as well as on the use of a knowledge based system (KBS) to model and diagnose faults in vital process plant components such as control valves.
A methodology for risk-based inspection of pressurized systems
Authors: Hagemeijer P M , Kerkveld G 
Published: October 2002

This paper describes a methodology for risk-based inspection and focuses on the planning of inspection activities. Brunei Shell Petroleum (BSP) operates a large number of ageing production and evacuation facilities in the South China Sea, and is facing the challenge to identify the optimal inspection effort in a period of time when more production is required and operating costs have to be minimized. Since 1989 major investments (annual costs about 15 million US$) were made to perform base line inspections which resulted in corrective work and a large repository of equipment integrity data. These data require analysis and updating, as defined in this methodology. The challenge is for BSP to implement risk-based inspection of static equipment, which so far has been very successful. The methodology is based on the determination of risk by evaluating the consequences and the likelihood of equipment failure. Likelihood of failure is assessed, by means of extrapolation, at the future planned maintenance campaign to identify the necessary corrective work. The extrapolation is based on historical inspection and maintenance data as well as on anticipated future operating conditions. Such an analysis requires in-depth knowledge of the equipment regarding functions, operating conditions, materials, imposed potential failure modes and causes, and their controlling parameters (integrity parameters). The novelty of the method is that equipment integrity is expressed in terms of integrity parameters, which can be measured and trended. Consequently, based on defined limits for the integrity parameters (i.e. anomaly classifications), actions for managing risk to an acceptable low level can be identified. The transparent linkage between monitoring activities (e.g. inspection) and integrity parameters offers an effective framework to manage and to demonstrate integrity against clear quantifiable acceptance limits. By pursuing the above methodology for all equipment, a list of inspection activities, prioritized on equipment condition and the risk of failure, can be derived. Within BSP this has resulted in a demonstrated increased efficiency of the inspection effort, a focused strategy for repairs executed on a campaign basis, and an improved quantification of BSP's facilities integrity. The approach has been proven in the company to be practical and it can be implemented relatively quickly.
Design of small-rate feeders for non-free-flowing materials: A case study
Authors: Bradley M S A , Pittman A N , Dawson M J 
Published: October 2002

This paper uses a case study to illustrate the problems which can occur when using small feeders to dose at low rates, with materials which are not totally free flowing. The general principles of good design for small feeders are enlarged upon, together with issues to look for when trouble shooting these equipment items. The system in question used a screw to dose a moist pelleted talc into a process at a nominal rate which was variable at around 1 t/h and originally suffered from poor flow in the hopper, a variable dosing rate and binding of the screw, thus needing constant attention from the operator to keep it working. Various types of mechanical flow assistance device had been tried, most of which made the problem worse. The Wolfson Centre redesigned the screw and hopper of the unit, and the performance problems were cleared. The problems with the original and intermediate designs serve to illustrate very well the points that need to be observed, in obtaining good performance from small feeders.