Recent studies have shown that a compact self-mixing interferometer can be used for the characterization of shock waves. It measures dynamically (> 10MHz) the changes in the refractive index induced by the shock wave. Associated to an appropriate acousto-optic model, the pressure profile is computed with a 34mbar resolution. In the present work, we compare shock wave induced refractive index variations measurements by another method using a Michelson-type fiber-optic interferometer with phase analysis that has been developed for Photonic Doppler Velocimetry applications. The output signals of this system are processed in triature, which consists in analyzing the phase shift between the three interferometric signals. This bulkier system provides, in theory, a better resolution than the self-mixing interferometry sensing scheme. In the present paper, we compare these two optical methods to measure a shock wave pressure through experiments that were carried out with an open shock tube instrumented with commercial, bandwidth limited, pressure sensors. This configuration creates a spherical shock wave similar to those observed during on-field experiments with explosives. We describe the two measurement systems and the experimental setup design used for overpressure characterizations. Both sensing approaches have been carried out in the same experimental conditions and with shock wave pressure peak amplitudes of a few bars. We detail the two types of signal processing and we discuss the results obtained with the two optical methods, which are also compared to a piezoelectric reference sensor.
Recent advances in infrared sensor technologies made improvements in spatial resolution and frame rates. How- ever, these progresses have been done at the cost of other performances, such as the conversion of charge to voltage. This is especially problematic for fast emission spectroscopy, where an infrared camera measures the radiation that has been previously dispersed by a grating. In this situation, the measured radiation level is low even at high temperature, because of the spectral width (here, a 40 nm spectrum is dispersed over 488 pixels). Because of the size reduction of pixels, each one collects less energy. Calibration becomes challenging because it is carried out in conditions where the response of the detector is not linear. The work presented suggests the correction of the nonlinear response of an InSb sensor of a FLIR camera. Measurements with a former camera are used to correct the FLIR sensor's response with a linear and a logarithmic function. An application is presented with the temperature determination of a H2, O2, N2, CO2 and Al particles deflagration by spectroscopy.
Studying radiative properties of molecules, for instance to identify species during fast phenomena, is not always simple because fast detection systems are required. With the experimental setup presented, high-resolution spectra in the visible (VIS) and the near infrared (NIR) range can be recorded at high frame rates for gaseous deflagrations. For such phenomenon, the flame front spreads in a few tens of meters per second. In the setup, the deflagrations are performed in a stainless steel cylindrical combustion chamber, which includes a sapphire window and incorporates a high-speed piezoelectric sensor to measure pressure variations. The emitted radiation is focused into the slit of a monochromator, and at its exit slit a camera records spectra in real time.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.