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Research Papers: Internal Combustion Engines

# Air Separation Membranes: An Alternative to EGR in Large Bore Natural Gas Engines

[+] Author and Article Information
Munidhar Biruduganti, Sreenath Gupta, Bipin Bihari, Steve McConnell, Raj Sekar

Argonne National Laboratory, Argonne, IL 60439

J. Eng. Gas Turbines Power 132(8), 082804 (May 27, 2010) (7 pages) doi:10.1115/1.4000296 History: Received May 21, 2009; Revised June 11, 2009; Published May 27, 2010; Online May 27, 2010

## Abstract

Air separation membranes (ASMs) could potentially replace exhaust gas recirculation (EGR) technology in engines due to the proven benefits in $NOx$ reduction but without the drawbacks of EGR. Previous investigations of nitrogen-enriched air (NEA) combustion using nitrogen bottles showed up to 70% $NOx$ reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single-cylinder spark-ignited natural gas engine. Low temperature combustion is one of the pathways to meet the mandatory ultra low $NOx$ emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, brake thermal efficiency (BTE), and unburned hydrocarbon emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from $ψ:1.0$ to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio $(Ψ)$ increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source, such as LI, could pave the pathway for realizing lower $NOx$ emissions with a slight penalty in BTE.

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## Figures

Figure 1

Air separation membrane

Figure 2

Schematic of experimental setup

Figure 3

Photograph of spark plug and laser plug

Figure 4

Specific NOx as a function of ψ

Figure 5

Ignition timing as a function of ψ

Figure 6

BTE as a function of ψ

Figure 7

ASM pressure drop as a function of ψ

Figure 8

Specific UHC as a function of ψ

Figure 9

Specific CO as a function of ψ

Figure 10

Exhaust CO2 as a function of ψ

Figure 11

Exhaust O2 as a function of ψ

Figure 12

BSFC versus specific NOx at different ψ

Figure 13

Ignition delay as a function of ψ

Figure 14

Combustion duration as a function of ψ

Figure 15

Peak cylinder pressure as a function of ψ

Figure 16

COVIMEP as a function of ψ

Figure 17

Variation in load, BMEP, as a function of ψ

Figure 18

Variation in load, IMEP, as a function of ψ

## Errata

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