Laser Raman Gas Diagnostics

The Laser Raman Workshop on the r"eas urement of Gas Properti es i sone of aseries of occasional meetings organized in an informal workshop format through the stimulation of Project SQUID, Office of Naval Research. This workshop is the second to be organized on gas-phase applications of Raman scattering. Both Raman workshops were supported by Project SQUID, ONR, and the Air Force Aero Propulsion Laboratory, Wright-Patterson Air Force Base. The first Raman Workshop was held at the AVCO Everett Research Laboratory, Everett, Massachusetts, with their co-sponsorship in January 1972 under the chairmanship of D. A. Leonard. The present meeting was co-sponsored by the General Electric Research and Development Center, and held at their facility in Schenectady, New York. We are grateful to Project SQUID, AFAPL, and GE for their generous financial support of this Workshop, and to Project SQUID for underwriting the publication costs of the Proceedings. As is always the case for successful meetings, many people contributed substantially to the organization and execution of this workshop. Professor Robert Goulard supported, aided, and encouraged us in the most helpful ways, and we are indebted to him. We received further valuable support and assistance from Dr. Ralph Roberts, Director, and Mr. James R. Patton, Jr., of the Power Branch, Office of Naval Research; from Dr. William H. Heiser, Chief Scientist of the Aero Propulsion Laboratory; and from Dr. James M.

Updated and expanded from the original Japanese edition, Laser-Aided Diagnostics of Gases and Plasmas takes a unique approach in treating laser-aided diagnostics. The book unifies the subject by joining applications instead of describing each application as a totally separate system. In taking this approach, it highlights the relative strengths of each method and shows how they can complement each other in the study of gases and plasmas. The first part of the book presents a general introduction to the laser-aided study of gases and plasmas, including the various principles and hardware needed for each method, while the second part describes the applications of each general system in detail. Beneficial to a wide spectrum of academic and industrial researchers, this book provides a solid examination of the various options and methods available when involved in the analysis and diagnostics of gases and plasmas.

The laser Raman scattering technique shows potential as a diagnostic method for determining the chemical and thermodynamic state of high-temperature gases. To investigate the utility of this technique for shock-tube diagnostics, and to validate the method at known elevated temperatures, vibrational Raman intensities were measured behind an incident shock wave. Intensity history data through the wave front, vibrational excitation times of oxygen in air, along with temperature and density measurements for oxygen and nitrogen in air were obtained over a range of postshock conditions. The measured densities and temperatures were found to be in good agreement with shock-wave theory. An excitation time measurement also agreed well with shock-tube data obtained with other diagnostic methods. In general, the results indicated that the Raman scattering technique was accurate at elevated temperatures and should prove useful in determining the thermochemical state of gases in continuous flows as well as in shock tubes and other impulse facilities.

This book examines the variety of potential laser diagnostic techniques and presents a considerable theoretical foundation elucidating physics relevant to the laser diagnostics. It explains the Raman-based approaches for major species and temperature measurements.

Laser-Raman scattering has been utilized to discover nonequilibrium N2 vibrational levels in a continuous, resistance-heated wind tunnel (Tunnel C) and in an arc-heated wind tunnel (Tunnel F). Vibrational temperatures of up to two times the bulk reservoir temperature have been measured in the Tunnel F free stream. A double-diaphragm device for delay of the Tunnel F nozzle expansion was found to significantly reduce the vibrational temperature level. In tunnel C, the vibrational temperatures were found to be dependent upon the water vapor concentration in the flow. It is hypothesized that water vapor-induced de-excitation of the vibrationally excited nitrogen molecules results in a significant rise in local static temperature and corresponding reduction in Mach number. (Author).