Low NOx Gas Turbine Combustor Research Articles

Conjugate Heat Transfer Computational Fluid Dynamic Predictions of Impingement Heat Transfer: The Influence of Hole Pitch to Diameter Ratio X/D at Constant Impingement Gap Z

Conjugate heat transfer (CHT) computational fluid dynamic (CFD) predictions were carried out for a 10 × 10 square array of impingement holes, for a range of pitch to diameter ratio X/D from 1.9 to 11.0 at a constant impingement gap Z of 10 mm and pitch X of 15.24 mm. The variation of X/D changes the impingement wall pressure loss for the same coolant mass flow rate and also changes the interaction with the impingement gap cross-flow. The experimental technique to determine the surface averaged heat transfer used the lumped capacity method with Nimonic-75 metal walls with imbedded thermocouples and a step change in the hot wall cooling to determine the heat transfer coefficient h from the transient cooling of the metal wall. The test wall was electrically heated to about 80 °C and then transiently cooled by the impingement flow and the lumped capacitance method was used to measure the locally surface average heat transfer coefficient. The predictions and measurements were carried out at an impingement jet mass flux of 1.93 kg/s m2 bar, which is a typical coolant flow rate for regenerative impingement cooling of low NOx gas turbine combustor walls. The computations were conducted for a fixed hot side temperature of 353 K that was imposed at the hot face of the target wall. The wall temperatures as a function of distance along the gap were computed together with the impingement gap aerodynamics. Surface average heat transfer coefficient h and pressure loss predictions were in good agreement with the experimental measurements. However, there was less good agreement for the axial variation of the local surface averaged h for lower values of X/D. The surface averaged heat transfer to the impingement jet wall was also computed and shown to be roughly 70% of target wall impingement heat transfer.

Development of Dry Low-NOx Gas-Turbine Combustors Equipped with Multi-Hole Co-Axial Jet Burners for IGCC

Development of Dry Low-NOx Gas-Turbine Combustors Equipped with Multi-Hole Co-Axial Jet Burners for IGCC

Effects of CO2 dilution on combustion instabilities in dual premixed flames

There has been a rapid increase in the demand for biogas applications in recent years, and dry low NOx and dry low emission gas turbine combustors are promising platforms for such applications. Combustion instability is the most important drawback in dry low NOx gas turbine combustors and has, therefore, attracted considerable research interest lately. As a fundamental study towards the use of biogas in dry low NOx and dry low emission gas turbine combustors, this article investigates the influence of CO2 in surrogate biogas on combustion instability. Tests were conducted using a dry low NOx type, a dual lean premixed gas turbine combustor. For a dual flame with dual swirl, the pilot fuel mass fraction affects the flame structure, and the flame structure, in turn, determines the temperature distribution in the combustion chamber and the combustion instability. The effects of the pilot fuel mass fraction, which is an important parameter of the combustor, and the CO2 dilution rate, which is a major contributor of biogas combustion, on the combustion characteristics and instability are investigated through dynamic pressure signal and phase-resolved OH* images. Combustion instability decreases for higher CO2 dilution rates, whose effects depend on the pilot fuel mass fraction. The instability reaches its maximum at a pilot fuel mass fraction of 0.3. Tests confirm that combustion instability diminishes with CO2 dilution, as it reduces the perturbation in the heat emission, and the flame speed decreases resulting in a greater flame surface or volume. Further, investigation of the Rayleigh Index, which represents the coupling strength of the heat release fluctuation and the natural frequency, shows that CO2 dilution weakens the coupling strength, resulting in less combustion instability.

Increasing Operational Stability in Low NOX GT Combustor Using Fuel Rich Concentric Pilot Combustor

Lean combustion is a method in which combustion takes place under low equivalence ratio and relatively low combustion temperatures. As such, it has the potential to lower the effect of the relatively high activation energy nitrogen-oxygen reactions which are responsible for substantial NOX formation during combustion processes. However, lowering temperature reduces the reaction rate and deteriorates combustion stability. The objective of the present study is to reduce the lower equivalence ratio limit of the stable combustion operational boundary in lean Gas Turbine (GT) combustors while still maintaining combustion stability.

408 筒状火炎を用いたガスタービン用低NOx多段希薄予混合燃焼器の試作(熱工学 I,2.学術講演)

408 筒状火炎を用いたガスタービン用低NOx多段希薄予混合燃焼器の試作(熱工学 I,2.学術講演)

Application of Turbulent Reacting Flow Analysis in Gas Turbine Combustor Development

Developing a low NOX gas turbine combustor usually requires many experiments on flow and combustion. Computational prediction technology in the field of combustion has progressed with advances in computer technology and turbulent combustion models. This report covers applications of CFD for the development of the gas turbine combustor and some discrepancies between CFD and test results as well as improved methods for resolving such discrepancies.

Advanced Catalytic Pilot for Low NOx Industrial Gas Turbines

This paper describes the design and testing of a catalytically stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high-pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598 K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single-injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.

Combustion instability mechanism of a lean premixed gas turbine combustor

Lean premixed combustion has been considered as one of the promising solutions for the reduction of NOx emissions from gas turbines. However, unstable combustion of lean premixed flow becomes a real challenge on the way to design a reliable, highly efficient dry low NOx gas turbine combustor. Contrary to a conventional diffusion type combustion system, characteristics of premixed combustion significantly depend on a premixing degree of combusting flow. Combustion behavior in terms of stability has been studied in a model gas turbine combustor burning natural gas and air. Incompleteness of premixing is identified as significant perturbation source for inducing unstable combustion. Application of a simple convection time lag theory can only predict instability modes but cannot determine whether instability occurs or not. Low frequency perturbations are observed at the onset of instability and believed to initiate the coupling between heat release rate and pressure fluctuations.

Performance of a Dry Low-NOx Gas Turbine Combustor Designed With a New Fuel Supply Concept

This paper describes the performance of a dry low-NOx gas turbine combustor designed with a new fuel supply concept. This concept uses automatic fuel distribution achieved by an interaction between the fuel jet and the airflow. At high loads, most of the fuel is supplied to the lean premixed combustion region for low-NOx, while at low loads, it is supplied to the pilot combustion region for stable combustion. A numerical simulation was carried out to estimate the equivalence ratio in the fuel supply unit. Next, through the pressurized combustion experiments on the combustor with this fuel supply unit using natural gas as fuel, it was confirmed that NOx emissions were reduced and stable combustion was achieved over a wide equivalence ratio range.

D143 MGC 材料適用ガスタービン用低 NOx 燃焼器の研究

D143 MGC 材料適用ガスタービン用低 NOx 燃焼器の研究

A Computational Study of Pressure Effects on Pollutant Generation in Gas Turbine Combustors

A numerical study of the effect of pressure on the formation of NOx and soot in an axisymmetric 30 deg counterrotating axial swirler lean low-NOx gas turbine combustor has been conducted. This has previously been studied experimentally and this CFD investigation was undertaken to explain the higher than expected NOx emissions. The combustion conditions selected for the present study were 300 K inlet air, 0.4 overall equivalence ratio, and pressures of 1 and 10 bar. The numerical model used here involved the solution of time-averaged governing equations using an elliptic flow-field solver. The turbulence was modeled using algebraic stress modeling (ASM). The thermochemical model was based on the laminar flame let formulation. The conserved scalar/assumed pdf approach was used to model the turbulence chemistry interaction. The study was for two pressure cases at 1 and 10 bar. The turbulence–chemistry interaction is closed by assumption of a clipped Gaussian function form for the fluctuations in the mixture fraction. The kinetic calculations were done separately from the flowfield solver using an opposed laminar diffusion flame code of SANDIA. The temperature and species profiles were made available to the computations through look-up tables. The pollutants studied in this work were soot and NO for which three more additional transport equations are required, namely: averaged soot mass fraction, averaged soot particle number density, and finally averaged NO mass fraction. Soot oxidation was modeled using molecular oxygen only and a strong influence of pressure was predicted. Pressure was shown to have a major effect on soot formation.

Low NOx and Fuel Flexible Gas Turbine Combustors

The work described in this paper is a part of the DOE/LeRC “Advanced Conversion Technology Project” (ACT). The program is a multiple contract effort with funding provided by the Department of Energy and technical program management provided by NASA LeRC. Testing has been done burning a petroleum distillate fuel (ERBS fuel), a coal derived fuel (SRC II middle distillate), a petroleum residual fuel, and various blends of these fuels. Measurements are made of NOx CO, and UHC emissions, and other measurements are made to evaluate combustor performance. Results to date indicate that rich-lean diffusion flames, with low fuel bound nitrogen conversion, are achievable with very high combustion efficiencies.