Search Results

Air pollution caused by engines is an international problem. Antipollution technology provides many technical solutions that may be effective in some countries and be inapplicable in others. The need for air pollution control and the shortage of petroleum-based fuels lead to the use of renewable sources of fuels, the biofuels. Quantities of alcohols can be used as fuel in order to substitute some part of gasoline in internal combustion engines. Methanol is an alternative fuel and can be produced from non-petroleum feed stocks such as coal or biomass. This paper examines the use of methanol-gasoline mixtures in an internal combustion engine of a small displacement that is used for the movement of a small alternative electrical generator. Different mixtures of methanol-gasoline (10%, 20% and 30% methanol) were used as fuel. The engine functioned without load at first and then under full load conditions (1KW).

It is generally accepted that the process of catalyst deactivation originates from the entrance sections of the converter and gradually progress towards the exit. The purpose of this paper is to investigate the possibility of a catalyst operating life extension via a mounting inversion, when the catalyst is close to its limits in the normal position. The experimental results indicate that under full load conditions at 3000 rpm improvement of catalyst efficiency can be accomplished reaching approximately 30% for CO and HC. This mounting inversion can be easily accomplished by an appropriate symmetric design of the monolith casing and mounting flanges, so that smooth gas flow conditions can be attained in both flow directions.

The present paper examines the possibility of chemical treatment of old catalysts (a catalyst that has exceeded exhaust limits) for the purpose of improving catalytic efficiency. The proposed method inserts the catalyst in a bath of a strong organic solvent that dissolves oil, soot and fuel residues cleaning the active surface of the catalyst. The preliminary experimental results based on CO, HC and catalyst inlet-outlet temperature difference measurements indicate that after this treatment the catalytic efficiency improves considerably (>30%). Therefore, there are strong indications that if car catalysts underwent a similar treatment at regular service intervals, for example, engine emissions could be considerably reduced and catalyst operational life extended. However more tests under variable engine speed (FTP-test) and load are clearly required in the future, before a definite conclusion can be made.

The present paper analyses the results from a series of experiments involving tests of catalysts under a stepwise constant engine idle speed schedule in the form of a step pyramid. This test speed schedule consists of an acceleration sequence formed by a number of abrupt speed increments followed by constant speed periods, and a deceleration sequence formed by the same speed changes executed in the reverse order. During the experiments the CO, HC, as well as the catalyst outlet - inlet temperature difference were monitored. The experimental results indicated that as the catalyst efficiency deteriorated with age, the rise of pollution levels was accompanied by significant changes in the CO and temperature difference signals. The HC signal was not as strongly affected. There are positive indications that the outlet - inlet temperature difference signal can be used as an input to a microcontrolled catalyst efficiency assessment system, capable of operating under driving conditions.

The present paper introduces a new method of assessing catalyst performance based on inlet-outlet temperature difference measurements. These preliminary experimental results indicate that at idle speed the age and catalytic efficiency affects this temperature difference reducing outlet temperature as the catalyst ages. The reduced efficiency of the catalyst increases also the time required for the equalization of the inlet and outlet temperature. An additional phenomenon present in these experiments is the gradual appearance of nonlinear time delayed effects as catalyst age increases that are reflected in the autocorrelation function of the temperature difference signal. These effects can be used for a catalyst performance assessment using temperature probes instead of the normal exhaust gas chemical analyzers.