Application of a Pre-Turbocharger Catalyst (PTC) on an Indian Multi Utility Diesel Vehicle for Meeting BS IV 2011-26-0024

Diesel engines tend to operate on lower exhaust temperatures, compared to their gasoline counterparts. Exhaust emission control becomes a significant issue at these lower temperatures, as any catalytic converter needs certain light off temperature to commence functioning. The trend so far has been to move the catalytic converters closer to the exhaust manifold, in order to get the benefit of higher temperatures - but most of the applications are limited to the location available after the turbo chargers. This is due the fact that very minute and efficient catalyst is required, if it has to be placed before the turbo charger. This catalyst also needs to be extremely durable to take care of high exotherms which occur within the catalysts and also to prevent any possible damage to the turbo chargers.

Metal substrates have proven to be more suitable in most of these critical applications due to their strong structural rigidity, lower back pressure, ease of packaging and durability characteristics. To address the requirements of placing the catalyst before the turbo charger, Pre Turbo Charger Catalyst (PTC) substrates have been developed. These are tiny substrate, with the cell density and the structure designed for lower back pressure onto the engine. These PTCs can be mounted in the exhaust system between the exhaust manifold outlet and the turbo charger inlet. With suitable precious metal loading, PTCs can offer good emission conversions, there by either enabling to meet the required emission legislations or to optimize the overall emission system by reducing the precious metal loading on the close coupled or underbody catalysts or even eliminating one of them totally [1,2]. However challenges in terms of turbocharger performance & durability needs to be addressed for successful commercialization.

The present work includes application of this PTC concept on a Multi Utility Vehicle with a 3.0 1 Common Rail Direct Injection diesel engine. A very small substrate of 34 cc has been installed before the turbo charger, with suitable precious metal loading. The high temperature available at this location has benefitted in getting better conversion efficiencies of CO and HC emissions, thereby helping to achieve engineering targets for BS IV emission legislations, along with the use of just an underbody catalyst.

Details on the necessity of the PTC for these applications along with the temperature and emission profiles with and without PTC are presented in this paper.