Review of thermal management of catalytic converters to decrease engine emissions during cold start and warm up

Catalytic converters mitigate carbon monoxide, hydrocarbon, nitrogen oxides and particulate matter emissions from internal combustion engines, and allow meeting the increasingly stringent emission regulations. However, catalytic converters experience light-off issues during cold start and warm up. This paper reviews the literature on the thermal management of catalysts, which aims to significantly reduce the light-off time and emission concentrations through appropriate heating methods. In particular, methods based on the control of engine parameters are easily implementable, as they do not require extra heating devices. They present good performance in terms of catalyst light-off time reduction, but bring high fuel penalties, caused by the heat loss and unburnt fuel. Other thermal management methods, such as those based on burners, reformers and electrically heated catalysts, involve the installation of additional devices, but allow flexibility in the location and intensity of the heat injection, which can effectively reduce the heat loss in the tailpipe. Heat storage materials decrease catalyst light-off time, emission concentrations and fuel consumption, but they are not effective if the engine remains switched off for long periods of time. The main recommendation of this survey is that integrated and more advanced thermal management control strategies should be developed to reduce light-off time without significant energy penalty

Performance prediction of a vapour-compression heat-pump

ARCAKLIOGLU, Erol/0000-0001-8073-5207WOS: 000224131800007The performance of the heat pump was predicted using a fuzzy-logic controller under various working-conditions and mixing ratios of R12/R22 refrigerant mixtures, instead of requiring an expensive and time consuming experimental study [Int. J. Ref. 13 (1990) 163]. Fuzzy-logic's linguistic terms provide a feasible method for defining the performance of the heat pump. Input data for the fuzzy logic are mixing ratio, evaporator-inlet temperature and condenser pressure. In the comparison of performance, results obtained via analytic equations and by means of the fuzzy-logic controller, the coefficient of performance (COP), and rational efficiency (RE) for all working situations differ by less than 1.5% and 1%, respectively. The statistical coefficient of multiple determinations (R-2-value) equals to 0.9988 for both the COP and the RE. With these results, we believe that fuzzy logic can be used for the accurate prediction of the COP and the RE of the heat pump. (C) 2004 Elsevier Ltd. All rights reserved