An Analysis of Alternative Fuels for Automotive Engines Joey Dille 1
Problem Hundreds of millions of people use the car as their preferred method of transportation, but cars pollute the air and contribute to global warming with their emissions. Which environmental friendly fuels are comparable to gasoline in heating value? 2
Hypothesis Hypothesis: Ethanol will provide the best alternative to gasoline. Why: Ethanol has similar properties to gasoline. Also, ethanol can be very green because is is made from plants. It requires engine modifications to run optimally. Countries like Brazil have already adopted it as their major vehicle fuel. 3
Combustion When fuel is burned, a combustion reaction occurs. C x H y O z + O 2 H 2 O + CO 2 Fuels with their own oxygen require less air to combust. 4
Calorimeter Design A calorimeter to burn the fuels had to be constructed. Some things had to be considered: The calorimeter must have reliable way to burn the fuel There must be an air intake There must be an exhaust outlet The heat must be directed toward the water Heat loss must be minimized There must be a way to measure everything accurately 5
Calorimeter Diagram Exhaust Thermometer Water Stirrer Body Tube with Insulation Combustor Fuel Tank Precision scale The Calorimeter Air Intake 6
Heat Flow Diagram Exhaust as hot air Exhaust as hot air Heat into water Air combusts fuel Air in at room temperature Air in at room temperature 7
Heat Flow Balance The first law of thermodynamics states that energy can't be created or destroyed. Heat in-heat out=heat stored Here is a sample calculation that shows how the heating value was calculated. Item Calculation Value Units Heat of evaporated water Mass Loss H2O*Hvp 0 J Heat Added to Water Cp(H2O)*( Tw) 173602 J Heat of Air Cp(air)* T(air)*m(air) 8518 J Heat of Fuel 182121 J Mass of Fuel Burned 8.50 g Heating Value of Fuel 21426 J/g 8
Heat Balance Equation H H C M T e H M v T C C M T a M v pe e f ( C pe M e Te ) + ( H vpw M w) + ( M w Tw C pw) ( C pa M a T = M = Heating Value of = Specific Heat of = Mass of = Temperature of w pw pa a = Heat of = Mass of = Change in Temperature of = Specific Heat of = Specific Heat of = Mass of = Temperature of f f vpw w = Mass of Exhaust Vaporization of Water Air Fuel Exhaust Air Exhaust Water Air Fuel Water Water f This is the equation used to compute the heating value of the fuel when the constants and measurements were added and some stoichiometry work was done. 9 a )
Fuels Used 1. Gasoline (control) 2. Kerosene (similar to diesel) 3. Ethanol (from ecological sources) 4. E85 (FlexFuel) 5. Biofuel (methyl soy) 6. Used Cooking Oil (being used as a diesel) 10
Ecology Some fuels have a greater ecological impact than others. Fossil fuels release more greenhouse gases like CO 2 into the air. Biofuels use plants that already absorbed CO 2 and then release the same amount they absorbed back the atmosphere when they are burned. This makes the process carbon-neutral and more green. 11
Stoichiometry Calculations were made to determine how much air went into the reaction based on the hydrogen, carbon, and oxygen contents of the fuels. 2H 2 + O 2 --> 2H 2 O C + O 2 --> CO 2 Fuel Molar Percent H Molar Percent C Molar Percent O Moles of Air per Mole of Fuel Fuel-Air Ratio Kerosene 66.1% 33.9% 0.0% 2.40 14.71 Gasoline 67.5% 32.5% 0.0% 2.35 14.89 Ethanol 66.7% 22.2% 11.1% 1.32 11.50 Biofuel 64.1% 32.4% 3.6% 2.13 13.68 Used Cooking Oil 63.6% 32.9% 3.5% 2.16 13.65 E85 66.8% 23.8% 9.4% 1.48 12.16 12
Heating Value Procedure 1. Measure fuel mass, water mass, air temperature, exhaust temperature and water temperature. 2. Burn fuel for about 30-40 minutes in calorimeter. 3. Measure exhaust temperature, water temperature, fuel mass and water mass again. 4. Repeat 3 times for each fuel. 5. Analyze fuels across several other categories. 6. Present data through project. 13
Measured Heating Values of Fuels Measured Lower Heating Value in kj/kg 35000 30000 25000 20000 15000 10000 5000 0 Kerosene Gasoline Ethanol Biofuel Used Cooking Oil E85 14
Density Procedure Fuel is usually sold by the unit volume, so a volume comparison is also valuable. The density of each fuel is needed to convert between mass and volume measurements. 1. Record volume of fuel. 2. Record mass of fuel. 3. Repeat 3 times for every fuel. 15
Density Average Densities of Fuels 1 0.95 Density in g/ml 0.9 0.85 0.8 0.75 0.7 Gasoline Kerosene Ethanol Biofuel Used Cooking Oil E85 16
Measured Volume Based Heating Value 30000 25000 Heating Value in kj/l 20000 15000 10000 5000 0 Kerosene Gasoline Ethanol Biofuel Used Cooking Oil E85 17
Fuel/Engine Compatibility Gasoline, Ethanol, and E85 are fuels are suitable for a spark-ignition engine. Gasoline is the most volatile and has the lowest flash point. It's vapors are flammable and easily ignited by a spark. Biofuel, Kerosene, and Used Cooking Oil are suitable for a diesel engine, which is about 30% more efficient (US EPA). 18
Measured Heating Values Compared to Published Values 40000 35000 Heating Value in kj/kg 30000 25000 20000 15000 10000 5000 0 Kerosene Gasoline Ethanol Biofuel Used Cooking Oil E85 Calculated Ihv Published lhv 19
Conclusions Biofuel, vegetable oil, ethanol, and E85 proved to be possible alternatives to gasoline in regards to heating value. The testing apparatus used had an inefficient design that led to an average of -40% error. 20
Combustion Issues Biofuel E85 Ethanol Gasoline Kerosene Used Cooking Oil 21
Measurement Errors Don t Explain All the Error 30.0% 25.0% 20.0% 15.0% ±10 10.0% 5.0% ±1 ±1 ±1 ±.1 0.0% 22 Control Air Temperature Exhaust Temperature Fuel Mass Water Temperature Water Mass Total Calculated Max Observed
Errors There was a lot of unburned carbon, especially in gasoline. This may have led to gasoline's strange results. Unaccounted heat loss from the body of the calorimeter. 23
Errors II One source of error is the fact that excess air that was not measured. Average Volumetric HV of Biofuel Heating Value in J/l 35000 30000 25000 20000 15000 10000 5000 0 1 2 3 5 10 Excess Air Ratio 24
Extensions and Applications Next year, I could explore the energy cost of producing each fuel and the "carbon footprint" of such processes. I could explore the possibilities of biofuel. I could also explore alternative heating fuels rather than engine fuels. This could be applied to the average person's car or truck's fuel and also on a national level like Brazil. 25