DESIGN AND IMPLEMENTATION OF AN INSTANTANEOUS FUEL MASS FLOW MEASUREMENT SYSTEM FOR USE IN VERIFICATION OF LOCOMOTIVE EMISSIONS

DESIGN AND IMPLEMENTATION OF AN INSTANTANEOUS FUEL MASS FLOW MEASUREMENT SYSTEM FOR USE IN VERIFICATION OF LOCOMOTIVE EMISSIONS Adam W. James Located in Altoona, PA, the Juniata Thoroughbred Emissions Research lab has provided emissions testing and research for several locomotive companies such as CSX, Electro Motive Diesel (EMD), and General Electric (GE). The emissions laboratory measures locomotive emissions through partial flow dilution (PFD) sampling for particulate matter (PM) using a Sierra Instruments BG3 and measures raw gaseous emissions using a MEXA 7100D gaseous emission analyzer. Fuel consumption is measured on a gravimetric basis and is used in verification of proportional sampling of exhaust flow. There were two research goals for this study which were (1) verify that the emissions measurement system used at the Juniata emissions lab is compliant to 40 CFR Parts 1033 and 1065 specifically that verification of proportional sampling can be performed and met using gravimetric fuel measurement and (2) design and implement an instantaneous fuel mass flow measurement system for use in verification of locomotive emissions. The emissions data acquisition (DAQ) system used at the Juniata lab, Scimitar, was used to compare a MATLAB® code that performed a carbon balance of the raw gaseous emissions and was used to calculate brake-specific emissions and exhaust flow rates. The brake-specific emissions from MATLAB® were compared to Scimitar as other factors were used in verification compliance calculations. For this study, a 2016 EMD SD60E with a model year 1990 engine was evaluated. Emissions calculations were performed for Idle and Notch 8 as they provided the extremes of fuel flow. The percent differences between MATLAB® and Scimitar brake-specific emissions for Idle were 2.10%, 0.00%, 2.25%, and 3.86% for the constituents CO2, CO, NOx, and THC, respectively, and 0.12%, 0.24%, 4.96%, and 11.6% for the same constituents at Notch 8. It was concluded that differences between each constituent came from their magnitude (i.e. low number brake-specific emissions caused higher errors). Furthermore, the dilution flow from the BG3 was compared against the sample flow of PM for verification of proportional flow per federal regulation using standard estimate of the error (SEE) calculations. Allowable per proportional verification regulation, the first 5% of data points were omitted during the notch. The SEE was calculated at 2.63% at Notch 8, and 5.62% at Idle. While the Idle SEE was not within regulation, the omission techniques used were changed to reduce the SEE. For this example, omitting 5% of the highest or lowest data points outside of the mean exhaust flow rate plus or minus one standard deviation (ṅexh ± σ) resulted in a new Idle SEE of 3.17%, which was compliant to 1065.545. While in this particular example the SEE was met, moving towards instantaneous methods of fuel flow for instantaneous exhaust flow calculations was more desirable as several factors such as EMD Notch 6 engine speed increase, or radiator fans cycling on mid-notch can alter the fuel consumption of the engine which would not be accounted for and provide inaccurate verification of proportional flow during the notch. Volumetric fuel consumption was evaluated with two KRAL-USA volumetric flow meters. The meters were placed in the supply and return lines of the gravimetric system to measure the difference between the flows which would provide the net flow of fuel that the locomotive’s engine consumed. For the same SD60, the SEE was calculated at 2.67% for Notch 8, which was consistent with gravimetric analysis, and 11.69% at Idle. While the SEE was non-compliant, it was due to the large errors of fuel consumption measurement. For this study, Notch 8 average fuel flow had a ±0.29% error and Idle fuel flow had a ±20.8% error. The maximum instantaneous errors were ±0.38% at Notch 8 and greater than ±3200% at Idle. It was determined that the large errors due to the subtraction of the flows at lower engine power levels affected the measured fuel flow rates significantly, which was undesirable and thus direct mass flow measurement was hypothesized to reduce the errors as a single flow measurement would be taken. A Coriolis mass flow measurement system was designed and implemented for the verification of proportional sampling. The mass flow measurement system was designed to measure fuel level in a temperature conditioned reservoir tank and work in PID control with a flow controller. Fuel burned by the locomotive dropped the level in the fuel reservoir tank. Fuel was replaced by a positive displacement pump through a flow controller which allowed fuel back into the reservoir tank. The replaced fuel was measured by a Coriolis meter which provided direct mass flow measurement. For this study, a 2003 SD70M with a model year 2003 EMD engine was tested with the mass flow measurement system. Manual PID control techniques were used to control level set point for fuel level reading. For this test, only PI terms used and set to 5. Carbon balances for Idle and Notch 8 were performed and the results were used to calculate the molar exhaust flow rate of the locomotive. The calculated exhaust flow rates were compared against the diluted flow rates from the BG3 for SEE evaluation. The SEE was calculated to be 1.38% during Notch 8, and 39.89% during Idle. It was determined that PI control of level was sufficient for proportional verification of exhaust flow during Notches 5, 6, 7, and 8 but not for other notches. Issues arose due to overshoot and undershoot of the level set point which caused large fluctuations in mass flow measurement. This resulted in inaccurate exhaust flow rates. It was concluded that further PID control tuning would be required to address the issues of overshoot.