Commissioning of a Combined Hot-Streak and Swirl Profile Generator in a Transonic Turbine Test Facility

Abstract

By enhancing the premixing of fuel and air prior to combustion, recently developed lean-burn combustor systems have led to reduced NOx and particulate emissions in gas turbines. Lean-burn combustor exit flows are typically characterized by nonuniformities in total temperature, or so-called hot-streaks, swirling velocity profiles, and high turbulence intensity. While these systems improve combustor performance, the exiting flow-field presents significant challenges to the aerothermal performance of the downstream turbine. This paper presents the commissioning of a new fully annular lean-burn combustor simulator for use in the Oxford Turbine Research Facility (OTRF), a transonic rotating facility capable of matching nondimensional engine conditions. The combustor simulator can deliver engine-representative turbine inlet conditions featuring swirl and hot-streaks either separately or simultaneously. To the best of our knowledge, this simulator is the first of its kind to be implemented in a rotating turbine test facility.The combustor simulator was experimentally commissioned in two stages. The first stage of commissioning experiments was conducted using a bespoke facility exhausting to atmospheric conditions (Hall and Povey, 2015, “Experimental Study of Non-Reacting Low NOx Combustor Simulator for Scaled Turbine Experiments,” ASME Paper No. GT2015-43530.) and included area surveys of the generated temperature and swirl profiles. The survey data confirmed that the simulator performed as designed, reproducing the key features of a lean-burn combustor. However, due to the hot and cold air mixing process occurring at lower Reynolds number in the facility, there was uncertainty concerning the degree to which the measured temperature profile represented that in OTRF. The second stage of commissioning experiments was conducted with the simulator installed in the OTRF. Measurements of the total temperature field at turbine inlet and of the high-pressure (HP) nozzle guide vane (NGV) loading distributions were obtained and compared to measurements with uniform inlet conditions. The experimental survey results were compared to unsteady numerical predictions of the simulator at both atmospheric and OTRF conditions. A high level of agreement was demonstrated, indicating that the Reynolds number effects associated with the change to OTRF conditions were small. Finally, data from the atmospheric test facility and the OTRF were combined with the numerical predictions to provide an inlet boundary condition for numerical simulation of the test turbine stage. The NGV loading measurements show good agreement with the numerical predictions, providing validation of the stage inlet boundary condition imposed. The successful commissioning of the simulator in the OTRF will enable future experimental studies of lean-burn combustor–turbine interaction.

Effect of a Combined Hot-Streak and Swirl Profile on Cooled 1.5-Stage Turbine Aerodynamics: An Experimental and Computational Study

“…As discussed by Adams et al [34], a significant drop in the hot stream total temperature was measured across the combustor simulator due to convective heat loss to the simulator hardware. This resulted in a mass-mean total temperature at turbine inlet of T 01 = 446.4 K (averaged over 20 runs), which is 6.0% below the design value of 475 K. Measurement of this temperature drop was conducted only after completion of the OTRF experimental investigation discussed in this paper and thus T 01 was not exactly matched between tests with uniform and nonuniform conditions.…”

“…[32,33]. The integration and commissioning of the combustor simulator in the OTRF was described by Adams et al [34]. During a test run, hot gas is supplied to the turbine inlet through an annular array of 20 discrete swirlers, which are aligned with the mid-span LE of every second HP vane.…”

“…Measurement Instrumentation. The measurements of the uniform and nonuniform inlet profiles were described by Adams et al [34]. For measurement of HP vane loading distributions, two HP vanes were instrumented, each with eight pneumatic tappings at 50% and 90% span.…”

Design and Commissioning of a Combustor Simulator Combining Swirl and Entropy Wave Generation

“…A modern aero-engine features an high degree of swirl angles with magnitudes up to ±40° [7,14]. In order to match this target, three different swirler generators are tested in the wind tunnel.…”

“…According to the same idea, the EWG proposed in [13] was designed, where only temperature perturbations were generated while vorticity perturbations were possibly imposed by tilting the injector axis with respect to the turbine axial direction. In [14], the only example of a combustor simulator featuring swirl and hot streaks implemented in a rotating turbine test facility is described. Another example of an EWG is described in [15].…”