Motivation

1. A Comprehensive JP-8 Mechanism for Vitiated Flow: Validation of ModelMegan Celia Chirby, RET Fellow 2009Community Links High SchoolRET Mentor: Dr. Kenneth Brezinsky, PhDNSF- RET Program Introduction Abstract A B C D 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. • 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 afterburner, as well as the species contained in JP-8 may affect the production of pollutants Objectives • 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 Figure 1: Sampling a flame produced by xylene combustion Materials and Methods Build System Sample Flame Determine Concentrations 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 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 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 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 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 2: A schematic of the apparatus used for experimentation Results Acknowledgements Conclusions • 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) • 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 • NSF EEC-0743068 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 Figure 5: 100% sampling velocity (blue) versus 56% sampling velocity (red) Figure 6: 1.2 mm (red) versus 4.8 mm (blue) from top of flame at 64% velocity.