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Novel water management and reactant distribution strategies are critical to next generation polymer electrolyte membrane fuel cell systems (PEMFCs). Improving these strategies in PEMFCs leads to higher power density and reduced stack size for vehicle applications, which reduces weight and improves the price competitiveness of these systems. Interdigitated flow fields induce convective transport (cross flow) through the porous GDL between adjacent channels and are superior at water removal beneath land areas, which can lead to higher cell performance. However, the head loss due to flow, among other factors, may cause cross flow maldistribution of reactants down the channel. Such maldistribution may lead to areas of low or areas of excess cross flow. This, in turn, can cause areas of low oxygen concentration and water build up, and therefore higher pressure losses and uneven membrane hydration, all of which reduce overall cell performance.

Textbook engine thermodynamics predicts that SI (Spark Ignition) engine efficiency η is a function of both the compression ratio CR of the engine and the specific heat ratio γ of the working fluid. In practice the compression ratio of the SI engine is often limited due to “knock”. Knock is in large part the effect of end gases becoming too hot and auto-igniting. Knock results in increase in heat transfer to the walls which negatively affects efficiency. Not to mention damages to the piston. One way to lower the end-gas temperature is to cool the intake gas before inducting it into the combustion chamber. With colder intake gases, higher CR can be deployed, resulting in higher efficiencies. In this regard, we investigated the efficiency of a standard Waukesha CFR engine. The engine is operated in the SI engine mode, and was operated with two differing mixtures at different temperatures.

High-efficiency, clean-combustion strategies for heavy-duty diesel engines are critical for meeting stringent emissions regulations and reducing the costs of aftertreatment systems that are currently required to meet these regulations. Results from previous constant-volume combustion-vessel experiments using a single jet of fuel under quiescent conditions have shown that mixing-controlled soot-free combustion (i.e., combustion where soot is not produced) is possible with #2 diesel fuel. These experiments employed small injector-orifice diameters (≺ 150 μm) and high fuel-injection pressures (≻ 200 MPa) at top-dead-center (TDC) temperatures and densities that could be achievable in modern heavy-duty diesel engines.

The integration of CAD/CAM/CAE in product development is the key to realize concurrent engineering. Generally, different systems are employed in product development department. These different systems create a lot of troubles such as difficult communication, misunderstanding and so on. A new approach to integrate CAD/CAM/CAE in one system based on CATIA for the end-to-end process in cylinder head development is presented. Multi-Model Technology (MMT) is used to create consistent and associated CAD models for the end-to-end process in cylinder head development. The concept and method to create and organize multi- models are discussed. A typically four-layer structure of MMT for mechanical products is defined. The multi-level structure of the cylinder head models based on MMT is provided. The CAD models of cylinder head created based on MMT can be used as the consistent model.

A study of the influence of dilution, attained by air excess, upon the dynamic stage of combustion - the nucleus of a work producing cycle - in a diesel engine, is reported as a sequel of SAE 2000-01-0203. While the latter has been restricted to variation in dilution obtained by bleeding air compressed by the supercharger, here the scope of engine tests was expanded by incorporating an additional stage of compression. Besides revealing the mechanism of the dynamic stage, the paper demonstrates that its effectiveness is a linear function of the air excess coefficient, irrespectively how it is attained.

The current is an investigation of the effects of charge motion, namely tumble, on the burn characteristics of the new Chrysler Hemi SI engine. In order to reduce prototyping, several combustion system designs were evaluated; some of which were eliminated prior to design inception solely based on CFD simulations. The effects of piston top and number of spark plugs were studied throughout the conceptual stage with the AVL-FIRE CFD code. It has been concluded that large-scale, persistent and coherent tumbling flow structures are essential to charge motion augmentation at ignition only if such structures are decimated right before ignition. Piston top had a detrimental effect on tumbling charge motion as the piston approaches the TDC. When compared to single spark plug operation, dual spark plug reflected considerable improvement on burn characteristics and engine performance as a consequence. The CFD simulations demonstrated good correlation with early dynamometer data.

Presented here is a reportage of the panel debate on the proposition: “Is there a future for internal combustion engines beyond the technologies of Otto and Diesel?,” held at the SAE 2001 Congress. This is preceded by a recount of all the panel discussions on the future of combustion in engines, which have taken place at the SAE Congresses since 1997. In a commentary following the reportage, a prospective view of the future is provided. It puts forth the concept that the technology, inherited over a hundred years ago from Otto and Diesel, by which the exothermic process of combustion is executed in an engine cylinder, can be advanced significantly by adopting the best that modern micro-electronic and MEMS technology can offer.

The paper is based on the premise that the sole purpose of combustion in piston engines is to generate pressure for pushing the expansion process away from the compression process (both expressed in terms of appropriate polytropes) to create a work producing cycle. This essential process, referred to as the dynamic stage of combustion, is carved out of the cycle and its salient properties deduced from the measured pressure profile, as a solution of an inverse problem: deduction of information on an action from its outcome. An analytical technique, construed for this purpose, is first presented and, then, applied to a direct injection, spark-ignition, methanol fueled four-stroke engine.

The sole purpose of combustion in a piston engine is to generate pressure in order to push the piston and produce work. Pressure diagnostics provides means to deduce data on the execution of the exothermic process of combustion in an engine cylinder from a measured pressure profile. Its task is that of an inverse problem: evaluation of the mechanism of a system from its measured output. The dynamic properties of the closed system in a piston engine are expressed in terms of a dynamic stage - the transition between the processes of compression and expansion. All the phenomena taking place in its course were analyzed in the predecessor of this paper, SAE 2002-01-0998. Here, on one hand, its concept is restricted to the purely dynamic effects, while on the other, the transformation of system components, taking place in the course of the exothermic chemical reaction to raise pressure, are taken into account by the exothermic stage.

In this article model-based controller design techniques are investigated for the transient operation of a common-rail diesel engine in order to optimize driveability and to reduce soot emissions. The computer-aided design has benefits in reducing controller calibration time. This paper presents a nonlinear control concept for the coordinated control of the exhaust gas recirculation (EGR) valve and the variable geometry turbocharger (VGT) in a common-rail diesel engine. The overall controller structure is set up to regulate the total cylinder air-charge with a desired fresh air-charge amount by means of controlling the intake manifold pressure and estimating the fresh air-charge inducted into the cylinders. During varying engine operating conditions the two control loops are coordinated by a compensation of the EGR valve action through the VGT controller.

Significant improvement of engine performance can be achieved by ushering in a micro-electronic system to control the execution of combustion - an exothermic process whose sole purpose is to generate pressure. Hence, the primary feedback for the controller is provided by a pressure transducer. The activators are piezo-electrically activated pintle valves of MEMS type. The task of the micro-electronic processor is to provide an accurate feed-forward signal for the actuators on the basis of the information obtained from the feedback signal, within a time interval between consecutive cycles. Furnished here for this purpose is an algorithm for an interface module between the pressure sensor and the governor. Concomitantly, the gains thus attainable in the reduction of fuel consumption and curtailment of pollutant formation are thereby assessed. The implementation of this method of approach is illustrated by application to a HCCI engine.

The paper describes results from investigating Common Rail (CR) injection in a dedicated optical engine with optimum access to the whole cross section of the engine cylinder through piston. This engine maintains all production-type details of the combustion chamber geometry being crucial to the flow fields required for optimum engine performance. This optical engine is used along with 2D optical diagnostics for temperature, soot and OH as well as spray shadowgraphy to analyze all phases of injection and combustion under virtually real engine conditions. By using special prototype CR injectors, the effects of engine design and operation strategies on ignition, combustion and pollutant formation are studied and controlling parameters are isolated. Special emphasis is devoted to the effects of injector stability, spray symmetry, nozzle geometry, injection rate, pilot injection and swirl effects.

For studying the effects of injection system properties and combustion chamber conditions on the penetration lengths of both the liquid and the vapor phase of fuel injectors in Diesel engines, a holistic injection model was developed, combining hydraulic and spray modeling into one integrated simulation tool. The hydraulic system is modeled by using ISIS (Interactive Simulation of Interdisciplinary Systems), a one dimensional in–house code simulating the fuel flow through hydraulic systems. The computed outflow conditions at the nozzle exit, e.g. the dynamic flow rate and the corresponding fuel pressure, are used to link the hydraulic model to a quasi–dimensional spray model. The quasi–dimensional spray model uses semi–empirical 1D correlation functions to calculate spray angle, droplet history and droplet motion as well as penetration lengths of the liquid and the vapor phases. For incorporating droplet vaporization, a single droplet approach has been used.

The potential for improving the efficiency of a heavy duty turbocharged diesel engine by closed loop Air-Fuel Ratio (AFR) management has been evaluated. Testing conducted on a 12 liter diesel engine, and subsequent data evaluation, has established the feasibility of controlling the performance through electronic control of air management hardware. Furthermore, the feasibility of using direct in-cylinder pressure measurement for control feedback has been established. A compact and robust fiber optics sensor for measuring real time in-cylinder pressure has been demonstrated on a test engine. A preferred method for reducing the cylinder pressure data for control feedback has been established for continued development.

The NO distribution in a directly-injected Diesel engine with realistic combustion chamber geometry was investigated with laser-induced fluorescence (LIF) imaging with KrF excimer laser excitation. The highest possible level of selectivity has been ensured using spectrally resolved LIF investigations inside the Diesel engine. To minimize interference from both, oxygen and polycyclic aromatic hydrocarbon (PAH) LIF the NO signal was detected around 237 nm, blue-shifted compared to the excitation wavelength resulting in a background contribution below 10% at the earliest detection timing possible in the engine under study (20°ca after top dead center, TDC). The in-cylinder NO LIF intensities were compared for different injection systems and operating conditions and correlated to variations in pressure traces and soot temperature measurements.

In response to ever more stringent emission limits (EURO IV, SULEV), engine developers are increasingly turning their attention to engine start-up and warm-up phases. Since in this phase the catalytic converter has not yet reached its operating temperature, problems occur especially with regard to hydrocarbon emissions (HC) which are emitted untreated. Secondary air injection represents one option for heating up the catalytic converter more quickly. The engine is operated during the heating up cycle with retarded ignition angles and a rich mixture. Ambient air (secondary air) is injected close to the exhaust valve seat. During the spontaneously occurring post oxidation phase, the reactive exhaust components ignite and heat up the catalytic converter while simultaneously reducing HC. The various processes which affect the post oxidation, are not well known up to now. In order to achieve concrete improvements, detailed knowledge of its influences are necessary.