Experimental investigation of cold start emission using parallel and telescopic catalytic converters in a multi cylinder spark ignition engine

Abstract

The need of the hour is to control the pollution in general and air pollution generated from automobiles in particular Emission in Internal Combustion Engines I C Engines affects the quality of air leading to global warming and degeneration of human health I C Engines generally use fuels derived from crude oil as source of energy Combustion of gasoline ideally leads to the formation of carbon dioxide COtwo and water vapour At the same time due to incomplete combustion potentially harmful products like unburnt hydrocarbons HC carbon monoxides CO and various oxides of nitrogen NOx are also produced Catalytic converters are capable of converting CO into COtwo hydrocarbons in to COtwo and water vapour and NOx in to Nitrogen and oxygen The Catalytic converters become effective only after they reach the activation temperature light off temperature which would generally take two to three minutes during the cold start The untreated harmful emission during this period is referred to as cold start emission Control of harmful emissions during cold start of the engine has become a challenging task over the years due to the ever increasing stringent emission norms Positioning of the catalytic converter closer to the exhaust manifold is an efficient way of achieving rapid light off temperature On the other hand the resulting higher thermal loading under high load engine operation may substantially cause thermal degradation and accelerate catalyst ageing The objective of the present work is to reduce the light off time of the catalyst and at the same time to reduce the thermal degradation and ageing of the catalyst to the minimum possible extent In the present work two innovative approaches namely Parallel Catalytic Converter System PCCS and Telescopic Catalytic Converter System TCCS have been adopted to reduce the light off time of the catalyst The tests were conducted on a four cylinder Spark Ignition Engine under cold start condition In parallel catalytic converter system two catalysts namely Close Coupled Catalyst CCC and a Main Catalyst MC were used in parallel In this system initially the exhaust was allowed to flow through CCC and MC When the MC reached light off temperature the exhaust was allowed to flow directly through MC so as to protect CCC from thermal degradation The emission characteristics and light off behavior of CCC and MC were discussed It has been found that the minimum CO light off time for CCC was achieved in thirty seconds and for MC in hundred seconds Also HC light off time for CCC was achieved in thirty six seconds and HC light off in hundred and fourteen seconds newlineIn the second approach a Telescopic Catalytic Converter System TCCS was used to reduce the cold start emission Using TCCS the catalyst was kept very close to the exhaust manifold at fifteen cm from exhaust manifold during cold start and once it reached light off temperature the same catalyst was moved to a far away position at ninety cm from the exhaust manifold thereby the catalyst could be protected from thermal degradation and early ageing It was established that considerable reduction in the light off time was achieved by using TCCS Further reduction in the light off time was achieved by using pre catalysts forty percentage vol and twenty percentage vol and hot air injection It has been found that thirteen percentage reduction in CO light off time was achieved with pre catalyst forty percentage vol fifty percentage reduction with pre catalyst twenty percentage vol and sixty six percentage reduction with hot air injector system when compared to TCCS Also fourteen percentage reduction in HC light off time was achieved with pre catalyst forty percentage vol forty three percentage reduction with pre catalyst twenty percentage vol and sixty three percentage reduction with hot air injection system when compared to TCCS It was also established that light off time of TCCS can be brought down to ten seconds using hot air injection newline