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On the basis of modular pulse converter (MPC) exhaust system the authors present a new swirl exhaust system. Structural parameters on the swirl exhaust system and MPC system for N8160ZC diesel engine were calculated by a mathematical optimum method, and the two systems were tested under the same engine operation for comparison. Experimental results show that the swirl exhaust system has a better engine performance under most of the operating conditions than MPC system, but worse under the low-speed and part-load conditions. In order to understand the mechanism of this swirl exhaust system well, a three-dimensional particle dynamic analyzer (3D-PDA) was utilized to measure the steady turbulent airflow in a swirl three-branched model. The computational fluid dynamics (CFD) code KIVA was modified to simulate the flows. Computational results are in good agreement with measuring ones and reveal the swirl flow behavior in the junction.

A fluid dynamic mathematical model of the room airflow in monolith was established by an equivalent continuum approach. The commercial CFD code STAR-CD was used to simulate multi-dimensional steady flows in automotive catalytic converters. In order to verify the fluid dynamic model of the converter, a three-hole Pitot tube was adopted to measure the velocity distribution at the rear of the monolith. Computing results are in good agreement with experiments, which means the established model is feasible and can be applied to predict the flow performances of various catalytic converters. Then, the enhanced diffusion header (EDH) converters and oblique diffuser converters with different configurations were designed and simulated by the CFD code. Simulation results indicate that EDH and an oblique diffuser can improve the flow uniformity and decrease pressure loss in the converters. These results provide a useful guide for the optimum design of automotive catalytic converters.

A catalyst surfaced on Ag/Al2O3 substrate for the selective catalyst reduction (SCR) of NOx by ethanol was evaluated in a diesel engine, and the effect of the catalyst on the reduction of NOx from the diesel engine under the EURO III ESC test modes was also investigated. The reductant injecting device was designed by means of computational fluid dynamics (CFD) analysis, and the engine test bench including the reductant injection system for the evaluation of the NOx-SCR catalyst performance was established. On the bench, the SCR catalyst with the ethanol reductant was tested at different temperatures and space velocities (SV), and integrated with an oxidation catalyst to reduce the diesel exhaust emissions of NOx, HC and CO. Under the conditions of the SV=30,000 h-1 and the exhaust temperature range of 350∼420°C, the NOx conversion efficiency is high over 90% and low beyond the temperature range.