Presentation on theme: "Motivation The oxidation chemistry of JP-8, the fuel used to power the US Air Force fleet, is unknown JP-8 contains components that emit large amounts."— Presentation transcript:
Motivation The oxidation chemistry of JP-8, the fuel used to power the US Air Force fleet, is unknown JP-8 contains components that emit large amounts of pollutants Jet operating conditions in the, as well as the species contained in JP-8 may affect the production of pollutants Jet operating conditions in the afterburner, as well as the species contained in JP-8 may affect the production of pollutants AbstractIntroduction Results Objectives Materials and Methods Conclusions NSF EEC Grant Dr. Kenneth Brezinsky, Research Mentor Prof. Andreas Linninger, RET Program Director Dr. Gerardo Ruiz, RET Program Managing Director Dr. Bradley Culbertson, Department of Mechanical Engineering, Energy Systems Laboratory, UIC University of Illinois- Chicago Acknowledgements Probe inner diameter greatly affects the relative concentrations of combustion products in the sample Flame velocity needs to be measured to ensure that the sampling velocity is appropriate Collections taken towards the middle of the flame yield a more diverse sample; further experimentation is needed to determine the optimal sampling location Build System Sample Flame The Air Force uses JP-8 fuel to power their air fleet. After combustion, JP-8 products are major pollutants when released into the atmosphere. A better understanding of the chemical kinetics of JP-8 fuel in the afterburner in jet engines is necessary in order to reduce potentially hazardous emissions. Currently, there is limited knowledge on this subject. The overall scope of the project is to develop a robust computer model of the micro level kinetics in JP-8 combustion and after burn. Validation of the computer model is done by sampling gas species combusted in a counterflow burner, which mimics afterburn conditions. This project focuses on how to achieve isokinetic sampling and a stable flame in order to accurately determine the species in the surrogate fuels post combustion. Experiments thus far have shown that sampling probe inner diameter, sampling probe location in the flame and sampling velocity are important factors in precise species determination. Determine Concentrations Build a system that can mimic the conditions in a jet afterburner Produce a flame to initiate a combustion reaction Sample the flame to analyze the combustion products Determine the concentrations of species resulting from fuel combustion Probe Sampling Sample at varying heights within the flame with a quartz probe at different velocities (4 probes with varying inner diameters were tested) Transfer the sample to a gas chromatographer for species analysis Build Apparatus Build a system using a counterflow burner in which fuel flows from the bottom and the oxidizing gas mixture flows from the top A vaporizer for the fuel and a furnace for the oxidizing gas mixture are used to heat reactants to mimic temperature conditions in a jet afterburner Produce Flame Using a syringe pump, flow fuel towards the burner at a rate of 15 mL/hr. To initiate flow, use nitrogen as a carrier gas, flowing at 1.2 L/min. Flow the oxidizing mixture (29% oxygen, 71% nitrogen) towards the burner at a rate of 1.7 L/min Ignite the reactants with a spark at the burner opening to initiate combustion Probe A displays the most quantitative results for relative concentrations of products (Figure 4) Higher sampling velocities display the most quantitative results for relative concentrations of products (Figure 5) The height of the sampling probe in the flame affects the concentrations of combustion products in the sample (Figure 6) Figure 5: 100% sampling velocity (blue) versus 56% sampling velocity (red) Figure 1: Sampling a flame produced by xylene combustion A Comprehensive JP-8 Mechanism for Vitiated Flow: Validation of Model Megan Celia Chirby, RET Fellow 2009 Community Links High School RET Mentor: Dr. Kenneth Brezinsky, PhD NSF- RET Program Figure 2: A schematic of the apparatus used for experimentation A B C D Figure 3: The 4 probes used for flame sampling. Probe A – 310 μm Probe B – 110 μm Probe C – 80 μm Probe D – 6.35 mm Identity and Concentration of Products Analyze the graph resulting from gas chromatography to identify what species are present in the products and in what relative concentrations Figure 4: A graph resulting from flame analysis by gas chromatography. Measured in units of mV versus time (minutes), each peak represents a different species contained in the product. This graph shows probe A (blue) and probe B (red) at 78% velocity. Figure 6: 1.2 mm (red) versus 4.8 mm (blue) from top of flame at 64% velocity.