Kathleen M. Tacina

A Second Generation Swirl-Venturi Lean Direct Injection Combustion Concept

A low-NOx aircraft gas turbine engine combustion concept was developed and tested. The concept is a second generation swirl-venturi lean direct injection (SV-LDI) concept. LDI is a lean-burn combustion concept in which the fuel is injected directly into the flame zone. Three second generation SV-LDI configurations were developed. All three were based on the baseline 9-point SV-LDI configuration reported previously. These second generation configurations had better low power operability than the baseline 9-point configuration. Two of these second generation configurations were tested in a NASA Glenn Research Center flametube; these two configurations are called the flat dome and 5-recess configurations. Results show that the 5-recess configuration generally had lower NOx emissions than the flat dome configuration. Correlation equations were developed for the flat dome configuration so that the landing-takeoff NOx emissions could be estimated. The flat dome landing-takeoff NOx is estimated to be 87–88% below the CAEP/6 standards, exceeding the ERA project goal of 75% reduction.

Fundamental Study of a Single Point Lean Direct Injector. Part I: Effect of Air Swirler Angle and Injector Tip Location on Spray Characteristics

Lean direct injection (LDI) is a combustion concept to reduce oxides of nitrogen (NOx) for next generation aircraft gas turbine engines. These newer engines have cycles that increase fuel efficiency through increased operating pressures, which increase combustor inlet temperatures. NOx formation rates increase with higher temperatures; the LDI strategy avoids high temperature by staying fuel lean and away from stoichiometric burning. Thus, LDI relies on rapid and uniform fuel/air mixing. To understand this mixing process, a series of fundamental experiments are underway in the Combustion and Dynamics Facility at NASA Glenn Research Center. This first set of experiments examines cold flow (non-combusting) mixing using air and water. Using laser diagnostics, the effects of air swirler angle and injector tip location on the spray distribution, recirculation zone, and droplet size distribution are examined. Of the three swirler angles examined, 60 degrees is determined to have the most even spray distribution. The injector tip location primarily shifts the flow without changing the structure, unless the flow includes a recirculation zone. When a recirculation zone is present, minimum axial velocity decreases as the injector tip moves downstream towards the venturi exit; also the droplets become more uniform in size and angular distribution.

A Comparison of Three Second-generation Swirl-Venturi Lean Direct Injection Combustor Concepts

Three variations of a low emissions aircraft gas turbine engine combustion concept were developed and tested. The concept is a second generation swirl-venturi lean direct injection (SV-LDI) concept. LDI is a lean-burn combustion concept in which the fuel is injected directly into the flame zone. All three variations were based on the baseline 9- point SV-LDI configuration reported previously. The three second generation SV-LDI variations are called the 5-recess configuration, the flat dome configuration, and the 9- recess configuration. These three configurations were tested in a NASA Glenn Research Center medium pressure flametube. All three second generation variations had better low power operability than the baseline 9-point configuration. All three configurations had low NO(sub x) emissions, with the 5-recess configuration generally having slightly lower NO(x) than the flat dome or 9-recess configurations. Due to the limitations of the flametube that prevented testing at pressures above 20 atm, correlation equations were developed for the at dome and 9-recess configurations so that the landing-takeoff NO(sub x) emissions could be estimated. The flat dome and 9-recess landing-takeoff NO(x) emissions are estimated to be 81-88% below the CAEP/6 standards, exceeding the project goal of 75% reduction.

Evolution of Combustion-Generated Particles at Tropospheric Conditions

ABSTRACT This paper describes particle evolution measurements takenin the Particulate Aerosol Laboratory (PAL). The PAL consists ofa burner capable of burning jet fuel that exhausts into an altitudechamber that can simulate temperature and pressure conditionsup to 13,700 m. After presenting results from initial tempera-ture distributions inside the chamber, particle count data mea-sured in the altitude chamber are shown. Initial particle countdata show that the sampling system can have a significant effecton the measured particle distribution: both the value of particlenumber concentration and the shape of the radial distribution ofthe particle number concentration depend on whether the mea-surement probe is heated or unheated. Nomenclature B Buoyancy fluxd 0 Nozzle diameterd Equivalent source diameter, d =d 0 q r 0 r ¥ g Gravitational constantJ Momentum fluxl c Coflow length scalel M Morton length scalem Mass fluxQ Volume fluxR Richardson numberr Radial coordinateRe Reynolds numberT Temperatureu Velocityx Axial distance from the jet exit planex

CFD Predictions of N+3 Cycle Emissions for a Three-Cup Gas-Turbine Combustor [STUB]

The National Combustion Code (OpenNCC) was used to perform non-reacting and two-phase reacting flow computations for a unique pre-filming type LDI-3 fuel injector for a three-cup, nineteen-element flametube configuration. All computations were performed with a consistent approach of mesh-generation, spray modeling, reduced finite-rate kinetics and turbulence-chemistry interaction, as developed for CFD analysis of single-element and multielement LDI-3 designs with OpenNCC. Emissions and flowfield characteristics were predicted for a generic NASA N+3 engine cycle, with particular focus on the 7% and 30% ICAO power operating conditions. For both the conditions studied, the CFD analysis provided very good predictions for EINOx when compared with experimental data measured at NASA Glenn Research Center.