An advanced Lean-Direct-Injection (LDI) turbine engine combustor was developed. Named LDI-II, which stands for second-generation LDI, this technology has vastly improved and expanded the performance characteristics of the initial LDI design by not only exceeding NASA’s N+2 emissions goal, but also meeting the operability requirements of full engine power range. The key enabling feature of the technology is the coherence combination of fuel staging and positioning/sizing of swirler-venturi fuel/air mixer elements.

The venturi-swirler element employed for the LDI-2 is the same as those in the earlier LDI-I.

Earlier versions of LDI configurations have been primarily designed for single-flow-point evaluation for emission performance. They have relative low Technology Readiness Level (TRL l-2) due to the exploring stage of the technology. The LDI-2 has significantly raised the TRL to 3-5 by incorporating the engine product design philosophy into the development process, and vastly expanded the performance envelope as would be seen in production hardware. The result is a steep jump in performance over the first-generation LDI in emissions, operability, and engine realistics.

The fundamental building block of the LD1-2 is the multi-swirler-venturi fuel/air (F/A) mixer elements for low-emission performance. They are laid out in the combustor dome in clustered fashion to form the dome front, and facilitate fuel and air flows and their intimate mixing. Multiple fuel staging (2-4 stages) by shifting and turning on and off the fuel among certain F/A mixer clusters enables the expanded operation envelope. The LDI differentiates itself from the LPP (lean-prevaporization-premix) by eliminating the risk of flashback and auto-ignition. By optimally combining the fuel staging with the swirler-venturi F/A mixer element clusters, the design is able to achieve both emissions and operability goals.

The success of the LDI-2 has led to the further development into LDI-3, with the goal of reaching a TRL of 6 and higher. In the advent of lean combustion technologies for turbine engines in the midst of ever stringent environmental regulations, the achievement so far has demonstrated a near-term potential of the technology adaptation to new engine development. The LDI may well become the interruptive technology replacing the ongoing LPP, due to its low risk, cost, and high-performance potential.

This work was done by Phil Lee of Woodward FST, Inc. for Glenn Research Center. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact http://technology.grc.nasa.gov . LEW-19376-1


NASA Tech Briefs Magazine

This article first appeared in the June, 2016 issue of NASA Tech Briefs Magazine.

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