A Numerical Investigation on the Influence of Engine Shape And
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A Numerical Investigation on the Influence of Engine Shape and Mixing Processes on Wave Engine Performance A Thesis Presented to The Academic Faculty by Robert R. Erickson In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy School of Aerospace Engineering Georgia Institute of Technology December 2004 A Numerical Investigation on the Influence of Engine Shape and Mixing Processes on Wave Engine Performance Approved by: Professor Ben T. Zinn Professor Tim Lieuwen School of Aerospace Engineering School of Aerospace Engineering Georgia Institute of Technology, Adviser Georgia Institute of Technology Professor Jeff Jagoda Dr. Richard Gaeta School of Aerospace Engineering Advanced Transportation and Advanced Georgia Institute of Technology Systems (ATAS) Laboratory Georgia Tech Research Institute Professor Suresh Menon School of Aerospace Engineering Georgia Institute of Technology Date Approved: 16 December 2004 ACKNOWLEDGEMENTS First of all, I would like to acknowledge my thesis advisor, Ben Zinn, for his continued support of this project. I recognize that under the circumstances, he displayed a large amount of patience and always provided very helpful advice and guidance. I also appreciate his flexibility with my employment situation and his willingness to work with me on all issues, both personal and related to this research. Thanks. I also would like to acknowledge the assistance and guidance from Tim Lieuwen, Nikos Markopolous, and Yedidia Neumeier towards my initial and continued progress with this work. Next, I would like to acknowledge Chris Stone for his significant and often time con- suming assistance with computational/modeling issues as well as Suresh Menon for compu- tational combustion group resources. Additionally, I also acknowledge certain graduate students and friends including Nate Weiland, Akiva Sklar, Brian Ritchie, and all of the aerospace combustion lab students and employees for very helpful discussions and time. Finally, I would like to acknowledge the support of my family and Kelli McNeill. The support from my family began long before I entered graduate school, and I sincerely believe that I would not be the person I am today without the positive influence from both Kelli and my family. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS .............................. iii LIST OF TABLES ................................... vi LIST OF FIGURES .................................. vii SUMMARY ........................................ xv I BACKGROUND AND MOTIVATION .................... 1 1.1 Pre World War II . 2 1.2 World War II and the Luftwaffe . 4 1.3 Post War Research and Development . 7 1.4 Fundamental Wave Engine Operating Principles . 12 II PRELIMINARY DUCT SHAPE INVESTIGATION ........... 18 2.1 Model Equations . 19 2.2 Solution Technique . 21 2.3 Trial Functions . 22 2.4 Results . 24 III WAVE ENGINE MODEL DEVELOPMENT AND NUMERICAL IM- PLEMENTATION ................................. 36 3.1 Detailed Wave Engine Operation . 37 3.2 Formulation . 39 3.2.1 Model Equations . 40 3.2.2 Boundary Conditions . 41 3.2.3 Mixing Model . 44 3.2.4 Heat Release Models . 47 3.2.5 Numerical Implementation . 48 IV INITIAL NON-REACTING AND REACTING FLOW WAVE ENGINE SIMULATIONS .................................. 55 4.1 Non-Reacting Simulations . 56 4.1.1 Closed/Closed Systems . 56 4.1.2 Closed/Open Systems . 58 iv 4.2 Reacting Flow Results . 62 4.2.1 Detailed Chemical Kinetics Simulation Results . 63 4.2.2 Comparison of Heat Release Models . 71 4.2.3 Simplified Heat Release Model Validation . 72 4.3 Calculation of Thrust and Specific Fuel Consumption . 78 4.3.1 Thrust Calculation Formulation . 78 4.3.2 Positive Exhaust Outflow . 80 4.3.3 Backflow . 81 4.3.4 Example . 81 4.4 Exhaust Boundary Condition Investigation . 81 V WAVE ENGINE PERFORMANCE AS A FUNCTION OF INLET VALVE RESISTANCE AND MIXING CHARACTERISTICS .......... 89 5.1 Inlet Valve Resistance . 90 5.2 Mixing and Unsteady Heat Release Rates . 95 5.2.1 Large Scale Mixing Event Size . 97 5.2.2 Small Scale Mixing RMS velocity . 101 5.2.3 Turbulent Mixing Event Size . 113 VI WAVE ENGINE PERFORMANCE AS A FUNCTION OF ENGINE SHAPE ........................................ 116 6.1 Tailpipe Diameter . 117 6.1.1 Harmonic Content of Unsteady Heat Release Rates and Wave Engine Oscillations . 121 6.2 Exhaust Nozzle/Flare Study . 133 VII CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE STUD- IES ........................................... 140 7.1 Conclusions . 140 7.2 Recommendations for Future Studies . 143 7.2.1 Model Improvements . 143 REFERENCES ..................................... 147 VITA ............................................ 151 v LIST OF TABLES Table 1 Calculation of natural acoustic mode frequencies for straight and horn shaped ducts based on Eq. 21. Assumed sound speed and flare constant of 330m/s and 5.75, respectively. 24 Table 2 Summary of engine performance as a function of inflow resistance in terms of maximum average thrust. The time lag refers to the start of mixing in terms of the fraction of a period after the start of injection of reactants (i.e. the opening of the inlet valves). 92 Table 3 Summary of engine performance as a function of rms velocity of small scale mixing in terms of maximum average thrust. The time lag refers to the start of mixing in terms of the fraction of a period after the start of injection of reactants (i.e. the opening of the inlet valves). 103 Table 4 Amplitudes and phase coefficients for the Fourier reconstruction of the log normal energy addition function using five modes. 126 Table 5 Natural acoustic mode frequencies for the investigated wave engines with spatially uniform mean temperature of 2100K. 131 Table 6 Natural acoustic mode frequencies for the investigated engine geometries with a mean flow of 20 g/s and a non-uniform mean temperature field. 133 Table 7 Shift of natural acoustic mode frequencies away from harmonics of funda- mental corresponding to values in Table 6. 133 vi LIST OF FIGURES Figure 1 Karavodine gas turbine combustor. (1908) . 3 Figure 2 Marconnet valveless pulsejet design. (1908-09) . 3 Figure 3 Argus valveless pulsejet burner. (1940) . 5 Figure 4 The first V-1 prototype developed by Argus Aeroengines with Paul Schmidt. (1940) . 5 Figure 5 V-1 Thrust as a function of ram pressure. Lettered curves represent design iterations. 6 Figure 6 (a): Schematic of SNECMA Escopette along with particle location vs time figure. (b): Figure from U.S. patent of combined cycle pulsejet ramjet by J. Bertin of SNECMA motors. 8 Figure 7 Schematic of different engine geometries experimentally examined by Lo- gan and co-workers[34]. 9 Figure 8 Specific impulse vs. tailpipe length for methane and propane fuels and combustion chamber diameters of 3.0 in (a) and 3.5 in (b). Taken from [34]. 10 Figure 9 Valveless pulsejet described in Lockwood U.S. patent 3,462,955. 12 Figure 10 (a) Simplified wave engine schematic, and (b) qualitative time dependence of inlet pressure, inlet velocity, and total heat release rate. 14 Figure 11 Large vortex formation as a result of impulsive injection[24].Top row: re- sults from vortex dynamics model. Black indicates reactants. Bottom row: Schlieren data with particle path indicators. Left: Peak of injection. Middle: Onset of reaction. Right: Peak of reaction. 17 Figure 12 Illustration of forced acoustic resontor used in this investigation. 19 Figure 13 Comparison of driven pressure oscillations within straight ducts using the Galerkin method with two other published results. Results from Galerkin method for comparison with Ilinskii et al.[21] data correspond to larger forcing amplitude than that of the Chun and Kim[9] study. 26 Figure 14 (a): Time evolution of pressure at a closed end of a cylindrical duct forced at the fundamental natural frequency starting from rest. (b): Enlarged view of the limit cycle behavior. 27 Figure 15 (a) Time dependence of finite amplitude, limit cycle pressure oscillations driven in a straight duct (F0 = 5e−4, Ω = 1.0, c0 = 330m/s, L = 0.165m), and (b), the corresponding FFT. Duct shape is shown in the upper right portion of (b). Note that the power in the FFT is normalized with respect to the power in the fundamental mode. 28 Figure 16 Frequency dependence of limit cycle pressure oscillations for different forc- ing amplitudes in a straight duct. 29 vii Figure 17 Time dependence (a) and frequency content (b) of driven oscillations at the small end of horn shaped duct (α = 5.75, F0 = 5E − 4, Ω = 1.36, c0 = 330m/s, L = 0.224m). The frequency content in (b) corresponds to the calculations including 20 modes (solid line in (a)). 30 Figure 18 Pressure oscillations excited in straight and horn shaped closed ducts of equal volume using single frequency sinusoidal forcing. 31 Figure 19 Dependence of compression ratio on flare constant for exponential horn shaped acoustic resonators. 32 Figure 20 Pressure oscillations at an end of three different duct shapes motivated by study of Hamilton et al[19]. For duct shapes displayed on the right, the top, middle, and lower ducts correspond to a2 = 0, a3 = −0.5, a2 = −0.5, a3 = −0.5, and a2 = −0.5, a3 = 0, respectively. 34 Figure 21 Illustration of important physical processes occurring each cycle accompa- nied by axial pressure and velocity profiles. 38 Figure 22 Block inversion of a scalar field with event center located at l0 and size l. 45 Figure 23 Illustration of two length scale mixing using the LEM model. 46 Figure 24 Temperature dependence of simplified consumption model and Arrhenius fuel consumption rates. 49 Figure 25 Temperature dependence of constant pressure specific heats for major species. 51 Figure 26 Illustration of grid transformation. 54 Figure 27 Piston forced oscillation within a closed 0.3m long straight duct. (a) details three limit cycle oscillations extracted from (b). 57 Figure 28 Piston forced oscillation within a closed 0.5m long straight duct with open pressure release boundary condition. (a) shows detailed limit cycle oscil- lations extracted from (b).