Date of Graduation

2018

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Marc C Besch

Committee Co-Chair

Derek R Johnson

Committee Member

Arvind Thiruvengadam Padmavathy

Abstract

Natural gas (NG) reserves have been discovered in abundance with the aid of various technological advancements in the field of directional drilling and hydraulic fracturing. Prime movers of unconventional well development were previously identified to be over-the-road (OTR) trucks, drilling engines, and hydraulic stimulation engines. The increased NG reserves have driven the industry to shift from using diesel fueled engines to natural gas engines. This allows the industries to take advantage of the produced natural gas to be directly used as energy source to fuel the prime movers involved with unconventional well development.;The primary objective of this study is to characterize gaseous emissions, Particle Number (PN) concentrations and the Particulate Matter (PM) mass emissions from an engine operated on different natural gas fuel compositions, namely; i) 'pump quality' CNG, and blends with ii) higher ethane, and iii) higher propane contents. These fuel blends were selected as their properties are typical of extracted and untreated shale gas within major US shale gas formations and will potentially be used to fuel prime movers during hydrocarbon extraction. For this purpose, a Cummins 8.9L ISL-G engine was operated over three custom designed test cycles to replicate the prime movers' in-use engine speed and load conditions, pertinent to drilling, fracturing and over-the-road (OTR) activities. The ISL-G engine, a spark-ignited, and three-way catalyst (TWC) equipped heavy-duty engine typically used in on-road vocational applications was utilized as a surrogate for a Waukesha LI7044 engine, typically applied for drilling operations, due to its similarity in technology. The minimum recommended methane number for the ISL-G engine is 75 and thus, the methane numbers for the custom fuel blends were targeted at 75.5 (propane blend) and 75.3 (ethane blend).;The OTR truck cycle produced higher brake-specific emissions of CO 2, CO, NOx and lower HC emissions compared to the FTP cycle when operated with 'pump' CNG fuel. For the same fuel the drilling and fracturing cycles tended to have lower CO2 and HC emissions but higher CO emissions when compared to the off-road engine certification cycle. The two custom fuel blends were only used on the in-use cycles. As expected, CO2 emissions increased with increasing alkane concentration, while opposite trends were shown for THC and CH4. NOx emissions also tended to increase with higher ethane and propane blends, across all cycles. For all cycles and fuels, HC emissions were predominately CH 4 -- 94--97%. The PN concentrations were, in general, lower for the fracturing cycle, which was expected from a high load operating cycle. The OTR truck cycle, which is characterized by increased idle time, low load activity, and transient operation produced the highest PN concentrations when compared to the other two in-use cycles. When operating on 'pump' CNG, PN concentrations emitted over the OTR truck cycle were similar to the FTP. The custom fuel blends showed higher PN concentrations when compared to CNG over all test cycles. The drilling cycle being a high load cycle showed, generally, lower PM emissions when compared to the other cycles. In comparison to CNG, the two blends produced lower PM emissions over all cycles except when operated over the OTR truck cycle.

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