California Institute of Technology

Explosion Dynamics Laboratory

|Detonation Physics | Explosion Dynamics | Blast and fracture | Shock tubes | Projects |
Detonation Physics Laboratory This laboratory is designed to explore the physics of detonations in gases. There are two main detonation tubes or channels permanently set up in this laboratory.
The original detonation tube facility was been designed and constructed by Raza Akbar, Pavel Svitek, and Mike Kaneshige from 1993-1996. New flanges were designed by Tony Chao with help from Patrick Hung. In 2000 Tony designed a heating system, and Florian Pintgen installed and made this operational. Florian moved the data acquisition system from Sun Unix to Linux in 2003. A compansion narrow channel facility was designed and built by Jo Austin in 2002 with help from Marty Grunthaner. This facility is 18 X 150 mm and has a novel planar initiation developed by Marty and Scott Jackson.
Detonation tube,
initiator end The GALCIT detonation tube is 7.3 m (24-ft) long, 280 mm (11-in.) inner diameter and constructed of 3 cast stainless steel (304) segments joined together by flanges and high-strength fasteners. The tube is equipped with a gas control system to precisely create test mixtures of fuel, oxidizer and diluents; a gas mixer system; a vacuum system; instrumentation and data acquisition systems. Gas composition is determined by the method of partial pressures.
A short slug of oxygen-acetylene mixture is injected just prior to initiation as booster charge. The driver is initiated by an exploding wire created by discharging a capacitor through a copper wire. The driver produces a blast wave with an peak amplitude of about 0.4 MPa (60 psig) at the first pressure transducer, sufficient to initiate mixtures with cell widths up to 400 mm.
detonation tube, side Strain gauges and accelerometers are used to measure the tube motion and piezo-electric pressure transducers are used for detonation timing. Data are recorded on multichannel CAMAC-based digitizers and high-speed (1 GHz) digital oscilloscopes. A network of Unix-based workstations and PCs is used to acquire and analyze the data.
Detonation cell width is measured by inserting into the tube sooted foils 3 ft x 4 ft rolled into a cylindrical shape and riveted to a stiffening ring. For flow visualization studies, a cookie cutter is used to attach a 6-in by 6-in square section optical test section to the round tube and windows are directly attached to the narrow channel. High-speed (up to 1 MFPS and ns exposure times) framing, streak and still cameras are available for conventional photography and holographic interferometry. An excimer/dye laser and gated UV-sensitive CCD camera are available for PLIF measurements. A 1-m VIS-UV spectrometer is available for low resolution spectrum recording.
Studies carried out in this laborotory include:
  • Measurement of detonation structure (cell width) in Jet A, JP-10 and in HC fuel blends.
  • Correlation of detonation cell widths with detailed chemical reaction mechanisms
  • Measurements and Models of detonation diffraction openings and tubes.
  • Investigation of flexural waves created in shock tubes and detonation tubes.
  • Measurement of detonation front structure using high-speed imaging and OH PLIF
  • Spectroscopic investigation of detonations
  • Behavior of detonations in narrow channels and with acoustic absorbing walls
  • Photochemical initiation of detonation
Explosion Dynamics Laboratory Transient
Jet COmbustion Facility This laboratory is designed to examine issues related to flammability, flame propagation and deflagration-to-detonation transition. Four explosion vessels are available with volumes between 1 and 1200 liters, capable of containing pressures up to 100 atm. High-speed data acquisition systems, schlieren systems with video and rotating drum cameras, and instrumentation for pressure and temperature measurement are provided for these test systems. 400
 liter test vessel A flexible gas supply system and precision pressure measurements are used to create mixtures of various fuel-air types. Gas chromatography measurements are also available. A network of Unix-based workstations and PCs is used to acquire and analyze the data. A two-component laser-doppler-velocimeter is set up for measuring flow velocities during explosions.
Studies carried out in this laboratory include:
  • Transient jet initiation and DDT in hydrogen-air-steam mixtures
  • Ignition energy measurements in aviation kerosene
  • Inerting concentration measurements
  • Flammability limits in multicomponent mixtures.
  • Automated measurement of flame speeds by optical techniques.
  • Modification of fuels by thermal and oxidative methods.
  • A pulse detonation engine simulation facility.
Blast Wave and Dynamic Fracture Laboratory This laboratory is designed to examine issues related to high explosives and propulsion. A test cell rated to 25 g of high explosive and a test chambers with up to 100 g high explosive capacity are available. Detonation tubes and a ballistic pendulum are available to measure impulse, for pulse detonation engine applications. A special facility is available for creating dynamic fracture with detonation waves. Blast wave measurement capability is available for use with small charges.

Research studies in this laboratory have included:

  • Effect of DDT on measured impulse for pulse detonation engines.
  • Effect of obstacle type and spacing on DDT.
  • Effect of area changes on pulse detonation engine impulse
  • Effect of initiator size and type on pulse detonation engine impulse.
  • Dynamic fracture of tubes by detonations
  • Production of shock waves by rich fireballs
Shock Tubes and Other Facilities A number of other resources are available at GALCIT. These include a general-purpose shock tube (150 mm diam), the T5 hypervelocity facility, machine and electronic shops, photographic darkrooms and other technical support such as the GC-MS available through the EAC.

A set of modifications to the T5 facility have been developed to enable launching projectiles into combustible gas mixtures. This facility has been used to study the initiation and stabilization of detonation waves on spherical projectiles.
The 150-mm (6-in) shock tube has been used to study a number of issues in recent years, including:
  • Interaction of shock waves with liquid layers
  • The production of high-velocity water jets through shock loading.
  • Ignition of combustion by shock-heated air jets
  • The excitation of flexural waves by shocks inside thin-walled tubes.
  • Fracture of plates by shock loading
  • Initiation of detonation by annular gas jets and imploding shock waves
  • Initiation of detonation by shock focusing

Copyright © 1993-2014 by California Institute of Technology, Joseph E. Shepherd