Graduate Thesis Or Dissertation
 

Utilizing the thermodynamic properties of E85 to increase the specific efficiency of a high specific output single cylinder Formula SAE engine

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  • Formula SAE is a collegiate engineering competition that has participants from around the globe. Of the 1000 points available throughout the event, 100 (10%) are dedicated to the fuel efficiency of the student built race cars. Competition rules allow either gasoline or E85, a mix of 85% ethanol and 15% gasoline, to be used as the primary fuel source. Because of the reduced specific energy content of E85, scores are normalized by applying a 1.4 divider to the final consumed volume of E85. With the desire to earn more points, a quantifiable way to determine if E85 could be an advantage was needed. To measure fuel consumption on the race track where every gram added to the car matters, a way to characterize flow rate and dead time of the fuel injector in the car was devised by finding the static flow rate and the associated combination of opening and closing times, or dead time. The method devised was designed to be simple to perform and data analysis was automated to make post processing a simple matter of transferring flow rate and dead time numbers into the engine control unit. Data recorded on track at the Formula Student Germany 2013 event and on the Oregon State University engine dynamometer were compared, and a method to estimate fuel consumption on any recorded track from engine dynamometer data was created. The estimation was first compared with recorded results from competition with an error of 2.1%, indicating that the results were reasonable to use for different engine configurations. Engine data was recorded for E85 and run through the estimation to determine how much E85 fuel would have been required to run the same event. The estimation was also used to determine how much work was done on track by the engine, which is another indicator of total system efficiency. Four engine configurations were tested. The baseline engine was the configuration used in the 2013 Global Formula Racing car, consisting of a Honda CRF450X engine, 3.8 liter intake plenum, Bosch 945 fuel injector, 13.5:1 compression piston, and a Megacycle X2 camshaft. This configuration was running on gasoline. Configuration 2 switched to a Honda 16450-MEN-A51 fuel injector. Configuration 3 changed fuel from gasoline to E85. The last configuration increased the compression ratio to 14:1. Configuration 2 had the highest overall efficiency at 34%, with configuration 4 having the highest energy generation over the course of the FSG 2013 endurance at 29.4 MJ. After normalizing energy generation, configuration 4 required the least volume of fuel to complete endurance at 2.5 liters, a reduction from 2.7 liters that the baseline required. This resulted in an approximate point increase of about 4.4. While this is an increase in point, the was determined that it was not enough to justify the use of E85 at FSAE events due to increased procurement and handling difficulty, along with reduced engine starting reliability.
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