• Journal of Energy Engineering
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• v.17 no.4
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• pp.182-188
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• 2008

This paper is to compare the carbon-balanced and liner air-fuel ratio determination methods for alternative fuels. In the previous work, expansion of Eltinge chart, unburned hydrocarbon compensation, comparison of the results from various methods were discussed. It has been also concluded that Eltinge method might be regarded as the most general equation of AFR determination among the existing ones. In the recent years, however, increasing demand for the environmental preservation, including global warming-up protection, and energy conservation lead to introduce the alternative fuel to the internal combustion engine. Therefore, the exact calculations of AFR for these fuels are needed. Especially, for the fuel that contains oxygen, all AFR calculation equations except Eltinge have to be re-formulated. In this paper, the AFR for alternative fuel were calculated by re-formulated carbon balance, accuracy of which was already confirmed, and linear equations, which are newly proposed by statistical method for each fuel. The results show that AFRs based on carbon balance have a little more error compared with gasoline, however, the accuracy is enough for this formula to apply to various fuel. The proposed linear equation also have excellent accuracy below $\lambda=1.2$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1563-1571
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• 2003

This paper is the second part of several companion papers which compare the method of Air-fuel ratio(AFR) determination. In the previous paper, Eltinge chart was applied to the arbitrary fuel composition and the charts for gasoline, diesel, methanol, M85, liquefied petroleum gas(LPG), natural gas(NG), propane and butane were illustrated. In Eltinge chart, however, unburned hydrocarbon (UHC) is not used for determination of AFR. For improving accuracy, Eltinge suggested UHC compensation after the AFR reading in the chart. This compensation reduced the difference between real and reading value. In the compensation, however, the correction of oxygen and carbon dioxide is uncertain and there might be a mistake in conversion of UHC reading value. Therefore, the error is overestimated comparing with Spindt one which is most widely used. In addition, there is no comparison of the value with other useful methods. In this paper, the compensation of unburned HC was performed in Eltinge chart and the compensated value was compared with Spindts formula over wide range of AFR. The objects of investigating fuel are gasoline, methanol, NG and LPG. The result shows that Eltinge and Spindt method is flawlessly compatible and the difference between the two methods is under 0.3% in a λrange from 0.9 to 1.7. The method fur debugging instrumentation error is also presented.