Search Results

In view of recent and future US and european regulations the design optimization of 3-way catalytic converters (3WCC) should also account for catalyst durability. The purpose of this paper is to extend the authors' approach for 3WCC modeling and evaluation in the direction of covering some aspects of ageing behavior. After a brief examination of the commonly accepted ageing mechanisms, a new methodology for the assessment of catalyst durability is formulated. This methodology takes into account the effect of thermal loading, high-temperature oxidation and poisoning of the catalyst. Based on the approach presented, along with the 3WCC and other related models and computer codes already in-use by the authors, a comparative assesment of engine bench ageing cycles may be computationally supported. Correlation of vehicle ageing cycles with engine bench cycles may also be accomplished as illustrated by a case study.

The modeling of transient phenomena occurring inside an automotive 3-way catalytic converter poses a significant challenge to the emissions control engineer. Since the significant progress that has been observed with steady-state models cannot be directly exploited in this direction, it is necessary to develop a fully transient model and computer code incorporating dynamic behaviour of the three way catalytic converter in a relatively simple and effective way. The Laboratory of Applied Thermodynamics (LAT), Aristotle University Thessaloniki, is cooperating with the Engine Direction of FIAT Research Center, in the development of a computer code fulfilling these objectives, within the framework of an EEC Brite EuRam cost shared project. The CRF and LAT modeling approaches, along with the underlying philosophy and experimental work, are presented in this paper.

A 2.0 liter displacement gasoline fueled car, with closed-loop control and 3-way catalyst, was adapted to operate on CNG (Compressed Natural Gas). A system allowing the detection and measurement of aldehydes, ketones, polycyclic aromatic hydrocarbons (PAH) and speciated organic materials was set up. Running on different fuels, such as CNG, gasoline and gasoline/oxygenates blends, tests were carried out according to US (FTP '75) and European (ECE+EUDC) procedures with and without the original 3-way catalytic converter. Apart from the absence of evaporative emissions because of the required closed delivery system, test results pointed out that CNG use yields substantial air toxics benefits in terms of regulated and, above all, unregulated emissions.

An apparatus for the laboratory evaluation of the detergent properties of additives in diesel engine oils is described. It consists of an oil sump and high temperature piston/cylinder simulators connected so as to provide a simulation of an engine oil lubrication circuit. The apparatus allows rapid evaluation of all aspects of detergency under controlled operating conditions. The results of a series of tests carried out with this apparatus are also reported. They suggest that good discrimination between the oils containing different detergent additives can be obtained. The results also indicate that the apparatus may be an useful tool in the investigation of various functions performed by detergent additives and the examination of synergistic effects between various additives contained in a fully formulated oil.

The work starts with the investigation of the temporary viscosity loss of engine oils (SAE Paper No. 740976) and extends to the evaluation of the temporary viscosity changes on multigrade engine oils at the crankshaft bearings of European gasoline engines. In view of this, oil temperature is measured and a calculation is made of the distribution of shear rates and pressures acting on the lubricant film at the central crankshaft bearing of a European engine. Then an experimental evaluation is made of the temporary viscosity changes at high temperature of a multigrade oil under the separate action of high shear rates and pressures. A rolling-ball viscometer is used to measure the temporary viscosity of oil under pressure. Finally, an attempt is made to draw up a balance of the temporary viscosity of a multigrade oil in the different points of the bearing under examination.

A study on the temporary viscosity loss under high shear rates of engine lubricants was started in order to: 1. Set up a new viscometer, more correlate with the engine than the present ones. 2. Clarify the influence of this phenomenon on the lubricant performances. Preliminary results on a pressoviscometer are discussed. Namely it is underlined that the temporary viscosity loss affects both multigrade and unigrade oils, even if at different levels, and in different ways.