Effect of Engine Operating Conditions and Coolant Temperature on the Physical and Chemical Properties of Deposits From an Automotive Exhaust Gas Recirculation Cooler

Abstract

The effect of engine operating conditions on exhaust gas recirculation (EGR) cooler fouling was studied using a 6.4 L V-8 common rail turbodiesel engine. An experimental setup, which included a custom-made shell and tube heat exchanger (EGR cooler) with six surrogate tubes, was designed to control flow variables independently. The engine was operated at 2150 rpm, 203 Nm and 1400 rpm, 81 Nm, representing medium and low load conditions, respectively, and the coolant to the heat exchanger was circulated at 85 °C and 40 °C. Heat exchanger effectiveness and pressure drop was monitored throughout the tests. Deposits from the EGR cooler were collected every 1.5 h for a total of9h, and their microstructure was analyzed using a scanning electron microscope while their chemical composition was analyzed using a pyrolysis GC-MS apparatus, and the elemental weight percentages were obtained using a CHN analyzer. The results of these analyses showed that the effectiveness of the EGR cooler drops rapidly initially and asymptotes in a few hours. The medium load condition had a higher effectiveness loss due to a greater accumulation of deposits inside the EGR cooler, mostly due to increased thermophoresis, and produced smaller and coarse particles. The low load condition had lower effiectiveness loss but produced bigger particles mostly due to excess hydrocarbons. Coolant temperature played a significant role in altering the deposit microstructure and in increasing the amount of condensed hydrocarbons. More deposits were produced for the cold coolant condition, indicating that lower coolant temperature promotes greater hydrocarbon condensation and thermophoresis. These results indicate the complex nature of folding in automotive heat exchangers.

An original nondestructive sampling method to study the effect of gravity on the deposition of micron-sized large particles in exhaust gas recirculation (EGR) cooler fouling

“…Among all fouling problems in automobiles, EGR cooler fouling is one of the most representative scenarios. Past studies have confirmed that cooler type and size, [2][3][4][5] cooling water temperature, [6][7][8][9] exhaust gas composition, [10][11][12][13] and flow rate of exhaust gas [14][15][16][17] are essential factors affecting fouling. Undoubtedly, these studies have greatly improved our understanding of fouling.…”

Thermogravimetric analysis applied to characterisation of the evolution of EGR deposits in a working engine

“…The benefits of its use arise from the CO 2 in the recycle acting as a heat sink to lower adiabatic flame temperature, and the dilution of oxygen content in the intake charge lowering combustion temperature. 1 ‘High-pressure’ (HP) systems, taking exhaust from upstream of any Diesel Particulate Filtre (DPF) and cooling the recirculated stream suffer a drawback. The EGR system, particularly the surface of the heat exchanger, can become fouled with thermally insulating deposits despite considerable mitigation efforts by manufacturers.…”

Effect of Volatiles on Soot Based Deposit Layers

“…Diesel engine-out exhaust gas contains hot soot particulates that deposit on cool surfaces largely due to thermo phoresis [1], Exhaust also contains unburned and partially oxi dized hydrocarbons (HC), derived from both fuel and lube oil, which may condense and also deposit on cooler surfaces [2,3].…”