A Simulation Based Study to Improve Active Diesel Particulate Filter Regeneration through Waste-gate Valve Opening Modulation

Abstract

Nowadays, automotive vehicles are generally equipped with diesel particulate filter (DPF) systems in order to meet the strict particulate matter (PM) emission legislations. DPFs are highly practical systems; however, they need periodic active regeneration to clean the collected PM on their filters. Those regeneration processes are mostly effective when engine outlet temperature is above 500oC. At medium load diesel engine operations, exhaust temperatures generally remain below 500oC which is insufficient to maintain active DPF regeneration. Therefore, the aim of this study is to elevate exhaust temperatures above 500oC at those engine loads via modulating waste-gate valve opening (WGVO).In the analysis, a medium-duty diesel engine is modeled via using Lotus Engine Simulation (LES) software. It is set to operate at 1700 RPM engine speed and within 5.75-7.75 bar brake mean effective pressure (BMEP) engine load. WGVO modulation can control the mass flow rate of hot exhaust gas which bypasses the turbine and moves directly to the DPF. Lower exhaust expansion on turbine due to open waste-gate decreases compressor effectiveness and thus reduces volumetric efficiency. Reduced airflow causes an increase in exhaust temperature from 35oC to 100oC in the load range. While exhaust system can be warmed up above 500oC at 6.75 bar BMEP in half open waste-gate mode, this can only be achieved at 7.5 bar BMEP in waste-gate closed mode. The method is highly effective; however, it results in fuel penalty (up to % 9.2) due to increased cylinder heat loss which needs to be considered.