Nohara, T., Komatsu, K., Morimoto, T., and Naito, K., "Applications to the Off-Road Engines by Ultra-Small DOC Containing Metal Special Structure Design Substrates - Compact & Cost Effective with Small Aftertreatment System," SAE Technical Paper 2012-32-0036, 2012, doi:10.4271/2012-32-0036.
Off-road engines are requested with limited space due to variety of end products, and it is also requested reasonable costs for the limited end products prices. For that purpose, several small off-road engines have to comply with emission legislations by only engine modifications. However, the additional engine control and devices (=High pressure direct injection, combustion chamber modification, electrical control, turbo charging control, etc.) must be expensive, and increasing the total engine costs and manpower for developments. These are very critical issues for long term possibility of same engine productions which cover to new legislations in each country.Thanks to drastic fuel condition improvement for passenger cars / trucks around the world, it would be aroused one of the best solution by DOC (Diesel Oxidation Catalyst) systems rather than the engine modifications. However, the small DOC systems would lead to low emission conversion efficiencies by large gas-flow and high temperature (=larger SV (Space Velocity)) as an effect of high load applications.This paper describes ultra-small DOC systems with metal special structure design (LS: Longitudinal Structure design) substrate. For compact, HC/PM reductions issues, Hydrodynamic, heat transfer and gas dispersion of perspective, the metal LS substrate is firstly calculated for optimization of off-road application. Then, the hypothesis is evaluated by gas rig and actual engine tests for the emission conversion efficiencies under significant catalytic converter volume reduction and PGM reduction by considering the space and cost limitations. For off-road engine applications, it is confirmed that the LS substrate has advantages compared to conventional other types of substrates in ultra-small DOC systems.