Detonation Research for Propulsion Applications J E Shepherd

Detonation Research for Propulsion Applications J. E. Shepherd, E. Schultz, J. Austin, T. Chao, E. Wintenberger, P. Hung Graduate Aeronautical Laboratories California Institute of Technology Pasadena, CA 91125 USA Sponsored by ONR MURI “Multidisciplinary Study of Pulse Detonation Engines” PSU/CIT/Princeton Team Midyear Review, San Jose, CA, February 10 -11, 2000 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 1

Activities at Caltech • • Cellular structure characterization Initiation Diffraction Structural and thermal response 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 2

Cellular Structure • Purpose: characterize detonations in JP-5, JP-8, JP-10 fuels (l measurement) 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 3

CIT 288 -mm Detonation Tube modifcations: 1. Redesigned using FEM 2. Stronger flange-tube connections 3. Thicker flanges 4. Double number of fasteners 5. Heating system a) 8 zones of control b) 10 k. W total power 6. Higher temperature seals 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 4

Detonation initiation • DDT time scale analysis • Ideal vs real performance with DDT 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 5

DDT Scaling 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 6

Ideal PDE Impulse Computation by H. Hornung using Amrita (AMR) q/RT 1 = 40, g = 1. 2 Taylor-Zeldovich IC 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 7

Diffraction • Test series with H 2, C 2 H 4, C 3 H 8 fuels – Ar, He, N 2, CO 2 dilution. – Model development 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 8

Structural response • Response of tube to detonation loading 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 9

CIT Presentations • Structural response (Joe Shepherd) • Diffraction (Eric Schultz) • DDT and ideal performance (Jo Austin) 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 10

Progress to Date • 288 -mm tube modifications started – mechanical changes done • Diffraction study in 38 -mm tube done – kinetics validation, model development • Preliminary DDT time scale study • Impulse, P(t) measurements initiated • 2 D transient FEM studies 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 11

Structural Response of Detonation Tubes J. E. Shepherd, T. Chao, P. Hung - GALCIT 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 12

Goals • Modeling of thermo-elastic response of tubes to detonation loading • 3 D FEM computations with imposed detonation or shock loading • Develop design criteria • Experiments to examine failure mechanisms and thresholds 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 13

Flexural Wave Excitation • Traveling loads (shock or detonation) excite flexural waves in tubes • Resonance associated with waves traveling at flexural wave speed • Deformations can be up to 4 X static equivalent 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 14

Flexural Wave Excitation 1. 5 mm thick steel tube, 25 mm F, 0. 5 m long Critical velocity 927 m/s, shock speed 950 m/s 2 D Axi-symmetric explicit FEM 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 15

Loading by Flexural Waves Experiments in Caltech 288 -mm detonation tube Measured strain (hoop) Amplification factor 4 6 t (ms) U (m/s) 10 -4 0 2/10/00 2 8 California Institute of Technology Graduate Aeronautical Laboratories 16

Future Directions • More realistic tube configuration • Use gas dynamic simulations to provide boundary conditions • Investigation of stress concentrations • Coupling to thermal effects • Comparison with measurements in model tubes 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 17

Schedule I 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 18

Schedule II 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 19

Schedule III 2/10/00 California Institute of Technology Graduate Aeronautical Laboratories 20