Christopher Goldenstein

Assistant Professor of Mechanical Engineering

Telephone: (765) 494-5660
More about Christopher Goldenstein


Graduate Students

Garrett C. Mathews
School: Mechanical Engineering
Expected Graduation: 2021
Project/Thesis: High-speed laser-absorption diagnostics for temperature and species measurements in combustion gases of propellants and explosives

Morgan Ruesch
School: Aeronautics and Astronautics
Expected Graduation: 2021
Project/Thesis: Characterization of the flame structure of composite solid rocket propellants using laser diagnostics
Co-Advisor: Steve Son

Ryan J. Tancin
School: Aeronautics and Astronautics
Expected Graduation: 2021
Project/Thesis: Ultrafast laser-absorption spectroscopy in the mid-infrared for spatiotemporally resolved measurements of gas properties


Recent Publications

Design and application of a high-pressure combustion chamber for studying propellant flames with laser diagnostics

Tancin, Ryan J. ; Mathews, Garrett C. ; Goldenstein, Christopher S.
Review of Scientific Instruments, April 2019, Vol.90(4)


This manuscript presents the design and initial application of a high-pressure combustion chamber (HPCC). The HPCC exhibits several unique design attributes to enable high-fidelity studies of propellant-combustion physics at high pressures. The HPCC employs a flangeless and weldless design to provide a compact, easy to access, and relatively light weight (for its size and pressure capability) test chamber. It has a cylindrical test volume of 13.1 L and is capable of operating at pressures from approximately 0.4 mbar to 200 bar. The vessel is equipped with a ZnSe window to enable the laser ignition of propellants and energetic materials and 4 sapphire windows (2″ diameter and 4″ × 2″ slots) to enable the use of multiple optical diagnostics spanning the ultraviolet to mid-infrared. The sapphire windows are mounted in plugs with adjustable length to bring the windows inside of the test volume and facilitate line-of-sight optical measurements. The vessel can be accessed from the top and bottom via removable 5″ diameter plugs, and the bottom plug can be modified to enable studies of gaseous jets and flames. Some of the HPCC’s testing capabilities are demonstrated via high-speed IR imaging and laser-absorption-spectroscopy measurements of temperature and CO in laser-ignited HMX (i.e., 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane) flames at pressures from 2 to 25 bar.


2D mid-infrared laser-absorption imaging for tomographic reconstruction of temperature and carbon monoxide in laminar flames

Tancin, Ryan J ; Spearrin, R Mitchell ; Goldenstein, Christopher S
Optics express, 13 May 2019, Vol.27(10), pp.14184-14198


This manuscript presents the design and initial application of a mid-infrared laser-absorption-imaging (LAI) technique for two-dimensional (2D) measurements and tomographic reconstruction of gas temperature and CO in laminar flames. In this technique, the output beam from a quantum-cascade laser (QCL) is expanded, passed through the test gas, and imaged in 2D using a high-speed mid-infrared camera. The wavelength of the QCL is scanned across the P(0,20) and P(1,14) transitions of CO near 4.8 μm at 50 Hz to provide 2D measurements of path-integrated gas temperature and CO column density across over 3,300 lines-of-sight simultaneously. This enabled the first sub-second (0.1 s), high-resolution (140 μm), 2D laser-absorption measurements and tomographic reconstruction of flame temperature and CO mole fraction using mid-infrared wavelengths. Prior to entering the test gas, the beam was reflected off two diffusers spinning at 90,000 RPM (≈9400 rad/s) to break the laser coherence and prevent diffraction-induced image artifacts. This technique was validated with measurements of CO in an isothermal jet and then demonstrated in laminar, partially premixed, oxygen-ethylene flames despite large background emission from soot and combustion products.


Ultrafast laser-absorption spectroscopy for single-shot, mid-infrared measurements of temperature, CO, and CH4 in flames

Tancin, Ryan ; Chang, Ziqiao ; Gu, Mingming ; Radhakrishna, Vishnu ; Lucht, Robert ; Goldenstein, Christopher
Optics Letters, Jan 15, 2020, Vol.45(2), p.583


This Letter describes the development of an ultrafast (i.e., femtosecond), mid-infrared (mid-IR), laser-absorption diagnostic and its initial application to measuring temperature, CO, and CH4 in flames. The diagnostic employs a Ti:sapphire oscillator emitting 55 fs pulses near 800 nm that were amplified and converted into the mid-IR though optical parametric amplification at a repetition rate of 5 kHz. The pulses were directed through the test gas and into a high-speed mid-IR spectrograph to image spectra across a ≈30nm bandwidth with a spectral resolution of ≈0.3nm. Gas properties were determined by least-squares fitting simulated absorbance spectra to measured single-shot absorbance spectra. The diagnostic was validated with measurements of temperature, CO, and CH4 in a static-gas cell with an accuracy of 0.7% to 1.8% of known values. Single-shot, 5 kHz measurements of temperature and CO column density were acquired near 4.9 µm in a laser-ignited HMX (i.e., 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane) flame and exhibited 1−𝜎 precisions of 0.4% and 2.3%, respectively, at ≈2700K. Further, temperature and CH4 column density measurements were acquired near 3.3 µm in a partially premixed CH4-air flame produced by a Hencken burner and exhibited 1−𝜎 precisions of 0.3% and 1% respectively, at ≈1000K.


Simulation technique enabling calibration-free frequency-modulation spectroscopy measurements of gas conditions and lineshapes with modulation frequencies spanning kHz to GHz

Goldenstein, Christopher ; Mathews, Garrett
Applied Optics, Feb 10, 2020, Vol.59(5), p.149


A simulation technique enabling calibration-free measurements of gas properties (e.g., temperature, mole fraction) and lineshapes via wavelength- or frequency-modulation spectroscopy (WMS or FMS) is presented. Unlike previously developed models, this simulation technique accurately accounts for (1) absorption and dispersion physics and (2) variations in the WMS/FMS harmonic signals, which can result from intensity tuning induced by scanning the laser’s carrier frequency [e.g., via injection-current tuning of tunable diode lasers (TDLs)]. As a result, this approach is applicable to both WMS and FMS experiments employing a wide variety of light sources and any modulation frequency [typically kilohertz (kHz) to gigahertz (GHz)]. The accuracy of the simulation technique is validated via comparison with (1) simulated signals produced by established WMS and FMS models under conditions where they are accurate and (2) experimental data acquired under conditions where existing models are inaccurate. Under conditions where existing WMS and FMS models are accurate, this simulation technique yields nearly identical (within 0.1%) results. For experimental validation, the wavelength of a TDL emitting near 1392 nm was scanned across a single absorption line of H2O with a half-width at half-maximum of 350 MHz while frequency modulation was performed at 100 MHz. The best-fit first-harmonic (1𝑓) signal produced by this simulation technique agrees within 1.6% of the measured 1𝑓 signal, and the H2O mole fraction and transition collisional width corresponding to the best-fit 1𝑓 spectrum agree within 1% of expected values.


Wavelength-Modulation Spectroscopy for MHz Thermometry and H2O Sensing in Combustion Gases of Energetic Materials

Mathews, Garrett; Goldenstein, Christopher
AIAA SciTech 2019 Forum, AIAA-2019-1609


This paper presents the initial validation and application of a tunable diode laser (TDL) absorption sensor capable of measuring gas temperature and H2O concentration in combustion gases at rates up to 1 MHz. The sensor employs wavelength-modulation spectroscopy with 1f-normalized 2f-detection (WMS-2f/1f) to provide high-speed (up to 1 MHz), calibration-free measurements in harsh combustion environments despite small absorbance signals (≈0.004 to 0.10 here). During operation, two frequency-multiplexed TDLs emitting near 7185.59 cm−1 and 6806.03 cm−1 are injection-current modulated at 35 and 45.5 MHz, respectively, while they are scanned across the peak of H2O absorption transitions at 1 MHz. The sensor is demonstrated with measurements of gas temperature and H2O during: 1) laser ignition of a 6 mm diameter, grade 3, class-B HMX pellet and 2) the formation of a nitrocellulose fireball; thereby demonstrating the potential of this sensor to study highly transient combustion environments produced by energetic materials. High-speed (2350 frames-per-second) mid-infrared imaging was also performed during laser-ignition experiments to gain additional insight into the ignition process and facilitate interpretation of the path-integrated WMS-2f/1f signals.


Wavelength-Modulation-Spectroscopy Diagnostics for Characterizing Metallized and Halogenated Fireballs of Energetic Materials

Mathews, Garrett; Goldenstein, Christopher
AIAA SciTech 2020 Forum, AIAA-2020-0301


This paper presents the development of a three-color wavelength-modulation-spectroscopy (WMS) diagnostic for measuring temperature, H2O and atomic iodine (I) at 100 kHz in fireballs of HMX laden with H-5 micro-aluminum and iodine (I2) powder. This diagnostic employs three tunable diode lasers (TDLs) that were scanned across the peaks of H2O and iodine absorption transitions near 7185.6 cm−1, 6806.0 cm−1, and 7603.1 cm−1 at 100 kHz while being modulated at 35 MHz, 45.5 MHz, and 61.5 MHz, respectively. WMS with 1f -normalized 2f-detection (WMS-2f/1f) was performed using modulation frequencies approaching 100 MHz to facilitate simultaneous three-color measurements on a single line-of-sight via frequency multiplexing. The diagnostic was applied to study fireballs with various initial formulations and the results indicate that the addition of H-5 micro-aluminum improves combustion performance and yields higher peak fireball temperatures, while the addition of I2 crystals significantly hinders fireball combustion.


Scanned-Wavelength-Modulation Spectroscopy in the Mid-Infrared for Measurements of Temperature and CO in Aluminized Composite-Propellant Flames

Ruesch, Morgan; Mathews, Garrett; Blaisdell, Matthew; Son, Steven; Goldenstein, Christopher
AIAA SciTech 2020 Forum, AIAA-2020-0527


This work presents the application of a scanned-wavelength-modulation spectroscopy diagnostic for measuring the bulk gas temperature and CO concentration in flames of aluminized composite propellants of ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB). The temperature of two propellant flames (one with and one without aluminum) was measured at atmospheric pressure and various heights above the propellant surface. The maximum quasi-steady flame temperatures were 2544 and 2389 K for the propellants with and without aluminum, respectively. The temperature measured closest to the propellant surface (0.2 cm above the surface) was more than 150 K lower in the aluminized-propellant flame due to the delayed ignition of the aluminum particles. Measurements of path-integrated CO mole fraction indicate that air entrainment has a significant impact on the thermochemical structure of these flames. The results presented are the first to quantify how the bulk gas temperature of an aluminized composite-propellant flame varies with the distance above the burning surface.