Pulse-Burst-Laser-Based Sensor Suite for High-Speed 2D FuelAir Ratio and HeatRelease Rate Measurements for Combustor/Augmentor Instability

Period of Performance: 01/01/2015 - 12/31/2015


Phase 1 SBIR

Recipient Firm

Spectral Energies, LLC
5100 Springfield Street Array
Dayton, OH 45431
Principal Investigator


ABSTRACT:The objective of the proposed Phase-I research effort is to demonstrate the feasibility of 10-kHz, 2D fuel/air (F/A) ratio and heat release rate (HRR) measurements in laboratory burners at elevated pressures by using pulse-burst-laser (PBL)-based sensor suite. The novelty is the use of advanced PBL technology to generate the desired laser pulses with sufficient pulse energy/intensity at high-repetition-rate for performing three state-of-the-art spectroscopic techniques laser-induced breakdown (LIBS), spontaneous Raman scattering, OH/CH2O planar-laser-induced fluorescence (PLIF) for measuring 2D F/A ratio and HRR. Compared to state-of-the-art commercially available high-speed lasers, the PBL with ~50x more energy per pulse will extend the LIBS, PLIF, and potentially SRS measurements to 2D. Additionally, a wider tuning range of key parameters including pulse duration, pulse shape, wavelength, repetition rate etc. will be utilized to obtain simultaneous OH/CH2O PLIF and enhance the LIBS and Raman scattering signal strength. It will thus provide unprecedented insights into the combustion instability phenomena for combustors and augmentors. The proposed compact sensor suite to be developed in the Phase-II will have major impacts on understanding and reducing combustion instability in gas-turbine engines geared toward the development of next generation war fighters and has great potential to being commercially available for government laboratories, engine companies, and universities.BENEFIT:The primary challenges for laser-based sensors for 2D, high-speed, fuel/air (F/A) ratio and heat release rate (HRR) measurements using the three state-of-the-art spectroscopic techniques (LIBS, Raman scattering, and PLIF) for combustion instability in augmentor and combustors are 1) the extremely high pulse energy/intensity requirement for the spectroscopic techniques and 2) optical interference from the liquid-fuel combustors/augmentors. The present situation is that even the state-of-the-art commercial high-speed lasers (e.g., Edgewave/Credo combo) can only produce sufficient pulse energy/intensity for point or line measurements for LIBS and Raman. Moreover, those lasers are not viable to generate the desire pulses for all the proposed spectroscopic techniques from a single unit laser source. The research effort on developing pulse-burst-laser (PBL)-based sensor suite will alleviate this deficiency; the development will allow to interchangeable use for 2D F/A ratio and HRR detections at 10-kHz repetition rate via single unit laser source, thereby enabling multiple diagnostics to be used at full performance in practical combustors and augmentors in a single measurement campaign. All the proposed techniques are simple single beam approach, which makes them easy to be packaged into one fiber-coupled sensor for practical engine diagnostics. ?We anticipate the novel PBL-based sensor suite developed under this program will enable an array of new marketable products and technologies for investigation of combustion instability in augmentor and combustors. ???1. Immediate benefits to Air Force test facilities and OEMs: ?The development outlined in this proposal will enable high-speed 2D measurements for F/A ratio and HRR measurements, which will provide unique insights into the understanding of combustion stability in augmentors and combustors. Potential applications for defense missions include the reduction of combustion instabilities, pollution reduction, and fuel and fuel additive studies that enhance the performance and facilitate the design of next-generation combustion and propulsion systems. The proposed compact sensor suite should be applicable for nearly all combustion test facilities and as such will have broad commercial appeal covering most of the government laboratories, engine companies (OEMs), and universities etc. ???2. Scientific discovery ?Better understanding of the fundamental behaviors of complex physical coupling between the unsteady heat release and the resonant acoustic modes as well as F/A ratio in practical combustors/augmentors promises a rich field of intellectually stimulating scientific challenges, which in turn can quickly result in revolutionary technologies for advanced gas turbine combustors and augmentors that provide societal benefits via improved combustion stability, higher propulsion efficiencies, low emissions, improved durability, increased ease of manufacturing, and decreased cost. ?????3. Economic security and prosperity: ?The roles of gasoline and turbomachinery engines in the modern life are overwhelming. Even slight combustion efficiency improvement with minor reduction of combustion instability by understanding complex physical coupling between the unsteady heat release and the resonant acoustic modes as well as F/A ratio on the traditional gasoline and turbomachinery engines will have huge impacts on almost every corner of the US economy. In the foreseeable future, combustion of fossil and renewable fuels will be the major power sources for US defense. Other very important application areas include combustion for power generation and transportation. The successful development of these commercial products will help extend the global leadership of the US in R&D and manufacturing of engine technologies. ?