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The progressive reduction in permissible tailpipe emissions levels from automobiles has been achieved through the adoption of ever more complex engine control systems and aftertreatment components. This, in turn, has resulted in the development of increasingly sophisticated monitoring systems that can detect the failure or gradual degradation of any of these components and thereby fulfill the requirements of the stringent On-Board Diagnostic (OBD) legislation. Traditional monitoring techniques involve a physical model approach, which describes the system under investigation. This approach has limitations, such as available knowledge base and computational load. Neural networks, on the other hand, have been recognized as a powerful tool for modeling systems which exhibit nonlinear relationships between measured variables, such as internal combustion engines.

The adoption of each new level of automotive emissions legislation often requires the introduction of additional emissions reduction techniques or the development of existing emissions control systems. This, in turn, usually requires the implementation of new sensors and hardware which must subsequently be monitored by the on-board fault detection systems. The reliable detection and diagnosis of faults in these systems or sensors, which result in the tailpipe emissions rising above the progressively lower failure thresholds, provides enormous challenges for OBD engineers. This paper gives a review of the field of fault detection and diagnostics as used in the automotive industry. Previous work is discussed and particular emphasis is placed on the various strategies and techniques employed. Methodologies such as state estimation, parity equations and parameter estimation are explained with their application within a physical model diagnostic structure.

Restricting the airflow to the engine is a convenient, and therefore common, method of regulating engine performance in many forms of motor sport. Formula SAE, and its European counterpart Formula Student, impose such restrictions on engine configuration. The capacity of the engines must not exceed 610cc but, more specifically to this study, the intake system must be fitted with a 20mm diameter restrictor through which all the air must pass. There are, however, a number of geometrical parameters which can be changed to maximise the performance of the restricted engine. In this study, the effects of modifying the restrictor design, intake runner length, intake camshaft profile, exhaust geometry, and silencer design were measured using a transient dynamometer. These tests were performed on a 600cc four-stroke, four-cylinder Yamaha YZF R6 engine.

This paper describes a model of a 1.8-litre four-cylinder four-stroke gasoline engine fitted with a close-coupled three-way catalyst (TWC). Designed to meet EURO 3 emissions standards, the engine includes some advanced emission control features in addition to the TWC, namely: variable valve timing (VVT), swirl control plates, and exhaust gas recirculation (EGR). Gas flow is treated as one-dimensional (1D) and unsteady in the engine ducting and in the catalyst. Reflection and transmission of pressure waves at the boundaries of the catalyst monolith are modelled. In-cylinder combustion is represented by a two-zone burn model with dissociation and reaction kinetics. A single Wiebe analysis of measured in-cylinder pressure data is used to determine the mass fraction burned as a function of crank angle (CA) at each engine speed. Measured data from steady-state dynamometer tests are presented for operation at wide open throttle (WOT) over a range of engine speeds.

The incorporation of one-dimensional simulation codes within engine modelling applications has proved to be a useful tool in evaluating unsteady gas flow through elements in the exhaust system. This paper reports on an experimental and theoretical investigation into the behaviour of unsteady gas flow through catalyst substrate elements. A one-dimensional (1-D) catalyst model has been incorporated into a 1-D simulation code to predict this behaviour. Experimental data was acquired using a ‘single pulse’ test rig. Substrate samples were tested under ambient conditions in order to investigate a range of regimes experienced by the catalyst during operation. This allowed reflection and transmission characteristics to be quantified in relation to both geometric and physical properties of substrate elements.

The most common mode of deactivation suffered by catalysts fitted to two-stroke engines has traditionally been thermal degradation, or even meltdown, of the washcoat and substrate. The high temperatures experienced by these catalysts are caused by excessively high concentrations of HC and CO in the exhaust gas which are, in turn, caused by a rich AFR and the loss of neat fuel to the exhaust during the scavenging period. The effects of catalyst poisoning due to additives in the oil is often regarded as a secondary, or even negligible, deactivating mechanism in two-stroke catalysts and has therefore received little attention. However, with the introduction of direct in-cylinder fuel injection to some larger versions of this engine, the quantities of HC escaping to the exhaust can be reduced to levels similar to those found on four-stroke gasoline engines.

A technique has been developed to study the axial static pressure profile through the channels of a 400 cells per square inch (cpsi) catalytic converter monolith. The shape of the profile proved different from the accepted laminar flow profile, although the flow conditions are clearly laminar within the channels of the converter. The fact that the inner surfaces of the channels are extremely rough, and that this roughness is highly irregular, is thought to have an effect on the developed pressure profile. The measured profile was compared against the pressure profiles predicted by the most popular models in the published literature. A two-point criterion was developed to distinguish among those models. It was observed that Shah's model [1]* for the pressure drop along a square duct is the most appropriate. Additional static pressure measurements were taken both before and after the catalyst element and used to calculate the entrance and exit total pressure loss coefficients.

One-dimensional (1-D) modelling codes are now commonplace in engine simulation programs. Thermodynamic analysis associated with the unsteady gas flow through engine ducting is an important element within the modelling process. This paper reports on a new approach in analysing mass and energy transport through a pipe system using the mesh method. A new system has been developed for monitoring wave energy and gas properties, using a two-dimensional grid to represent the time-mesh boundary domain. This approach has allowed for refinement of the current mesh method by allowing more accurate monitoring of gas properties. The modified method was tested using measured results from a Single-Shot Rig. A CFD analysis was also conducted and compared with the new method. The new method performed very well on the range of pipe geometries tested.

With the legislative demands increasing on recreational vehicles and utility engined applications, the two-stroke engine is facing increasing pressure to meet these requirements. One method of achieving the required reduction is via the introduction of a catalytic converter. The catalytic converter not only has to deal with the characteristically higher CO and HC concentration, but also any oil which is added to lubricate the engine. In a conventional two-stroke engine with a total loss lubrication system, the oil is either scavenged straight out the exhaust port or is entrained, involved in combustion and is later exhausted. This oil can have a significant effect on the performance of the catalyst. To investigate the oiling effect, three catalytic converters were aged using a 400cm3 DI two-stroke engine. A finite level of oil was added to the inlet air of the engine to lubricate the internal workings. The oil flow rate is independent of the engine speed and load.

Washcoat sintering and substrate meltdown have traditionally been the principle deactivating mechanisms of catalysts fitted to two-stroke engines. The reduction of the excessively high HC and CO levels responsible for these effects has therefore been the focus of considerable research which has led to the introduction of direct in-cylinder fuel injection to some larger versions of this engine. However, much less attention has been paid to the effects of oil and its additives on the performance and durability of the two-stroke catalyst. The quantity of oil emitted to the exhaust system of the majority of two-stroke engines is much greater than in four-stroke engines of comparable output due to the total loss lubrication system employed. The fundamental design of the two-stroke also permits some of this oil to ‘short-circuit’ to the exhaust in a neat or unburned form.