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Research Papers: Internal Combustion Engines

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

[+] Author and Article Information
André L. Boehman

e-mail: boehman@ems.psu.eduDepartment of Energy and Mineral Engineering,
EMS Energy Institute,
The Pennsylvania State University,
405 Academic Activities Building,
University Park, PA 16802

1Corresponding author.

Contributed by the IC Engine Division of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received March 26, 2012; final manuscript received September 29, 2012; published online January 10, 2013. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(2), 022801 (Jan 10, 2013) (9 pages) Paper No: GTP-12-1090; doi: 10.1115/1.4007784 History: Received March 26, 2012; Revised September 29, 2012

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 of 9 h, 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 effectiveness 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 fouling in automotive heat exchangers.

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References

Figures

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Fig. 1

Test rig with in-house EGR cooler, flowmeter, high temperature valve, and recirculating chiller

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Fig. 2

Effect of engine operating condition on temperature profiles, ○ 2150 rpm, 203 Nm, exhaust; □ 2150 rpm, 203 Nm, EGR inlet; △ 2150 rpm, 203 Nm, EGR outlet; • 1400 rpm, 81 Nm, exhaust; ▪ 1400 rpm, 81 Nm, EGR inlet; ▴ 1400 rpm, 81 Nm, EGR outlet

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Fig. 3

Time varying effect of engine operating conditions on EGR cooler effectiveness change, ○ 2150 rpm, 203 Nm and ▪ 1400 rpm, 81 Nm

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Fig. 4

Time varying effect of engine operating conditions on deposit mass, ○ 2150 rpm, 203 Nm and ▪ 1400 rpm, 81 Nm

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Fig. 5

Variation of deposit microstructure (low magnification) as a function of time, (a) 1.5 h, (b) 3.0 h, (c) 4.5 h, (d) 6.0 h, and (e) 7.5 h

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Fig. 6

Variation of deposit microstructure (high magnification) as a function of time, (a) 1.5 h, (b) 3.0 h, (c) 4.5 h, (d) 6.0 h, (e) 7.5 h, and (f) 9.0 h

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Fig. 7

Py-GC chromatographs of species eluted as a function of time, (a) 1.5 h, (b) 3.0 h, (c) 4.5 h, (d) 6.0 h, (e) 7.5 h, and (f) 9.0 h

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Fig. 8

Variation of aromatics and aliphatics percentage as a function of time, 1.5 h, 3.0 h, 4.5 h, 6.0 h, ▪ 9.0 h, and data unavailable for 7.5 h condition

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Fig. 9

Effect of engine operating condition on EGR cooler deposit microstructure, (a) 2150 rpm, 203 Nm and (b) 1400 rpm, 81 Nm

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Fig. 10

Py-GC chromatographs of species eluted as a function of engine operating condition, (a) 2150 rpm, 203 Nm and (b) 1400 rpm, 81 Nm

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Fig. 11

Variation of aromatics and aliphatics percentage as a function of engine operating condition, 2150 rpm, 203 Nm, and ▪ 1400 rpm, 81 Nm

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Fig. 12

Effect of engine operating condition on temperature profiles, ○ 85 °C, exhaust; □ 85 °C, EGR inlet; △ 85 °C, EGR outlet; • 40 °C Nm, exhaust; ▪ 40 °C, EGR inlet; ▴ 40 °C, EGR outlet

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Fig. 13

Time varying effect of coolant temperature on EGR cooler effectiveness change, ○ 85 °C and ▪ 40 °C

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Fig. 14

Time varying effect of coolant temperature on the mass of deposits, ○ 85 °C and ▪ 40 °C

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Fig. 15

Effect of coolant temperature on deposit microstructure, (a) 85 °C coolant and (b) 40 °C coolant

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Fig. 16

Py-GC chromatographs of species eluted as a function of coolant temperature, (a) 85 °C coolant and (b) 40 °C coolant

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Fig. 17

Variation of aromatics and aliphatics percentage as a function of coolant temperature, 85 °C coolant and ▪ 40 °C coolant

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