Suppression of GO2/GH2 Combustion Instability Using CH4 Addition

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

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Extension of the Combustion Stability Range in Dry Low NOx Lean Premixed Gas Turbine Combustor Using a Fuel Rich Annular Pilot Burner

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4026186 ◽

2014 ◽

Vol 136 (5) ◽

Cited By ~ 5

Author(s):

L. Rosentsvit ◽

Y. Levy ◽

V. Erenburg ◽

V. Sherbaum ◽

V. Ovcharenko ◽

...

Keyword(s):

Gas Turbine ◽

Combustion Zone ◽

Combustion Instability ◽

Experimental Results ◽

Nox Emission ◽

Combustion Stability ◽

Stability Range ◽

Numerical Effort ◽

Lean Premixed ◽

Pilot Burner

The present work is concerned with improving combustion stability in lean premixed (LP) gas turbine combustors by injecting free radicals into the combustion zone. The work is a joint experimental and numerical effort aimed at investigating the feasibility of incorporating a circumferential pilot combustor, which operates under rich conditions and directs its radicals enriched exhaust gases into the main combustion zone as the means for stabilization. The investigation includes the development of a chemical reactors network (CRN) model that is based on perfectly stirred reactors modules and on preliminary CFD analysis as well as on testing the method on an experimental model under laboratory conditions. The study is based on the hypothesis that under lean combustion conditions, combustion instability is linked to local extinctions of the flame and consequently, there is a direct correlation between the limiting conditions affecting combustion instability and the lean blowout (LBO) limit of the flame. The experimental results demonstrated the potential reduction of the combustion chamber's LBO limit while maintaining overall NOx emission concentration values within the typical range of low NOx burners and its delicate dependence on the equivalence ratio of the ring pilot flame. A similar result was revealed through the developed CHEMKIN-PRO CRN model that was applied to find the LBO limits of the combined pilot burner and main combustor system, while monitoring the associated emissions. Hence, both the CRN model, and the experimental results, indicate that the radicals enriched ring jet is effective at stabilizing the LP flame, while keeping the NOx emission level within the characteristic range of low NOx combustors.

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Robust feedback control of combustion instability

Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207) ◽

10.1109/acc.1998.702976 ◽

1998 ◽

Cited By ~ 2

Author(s):

Boe-Shong Hong ◽

A. Ray ◽

V. Yang

Keyword(s):

Feedback Control ◽

Combustion Instability

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Large-scale coherent structures as drivers of combustion instability

10.2514/6.1987-1326 ◽

1987 ◽

Cited By ~ 2

Author(s):

K. SCHADOW ◽

E. GUTMARK ◽

T. PARR ◽

D. PARR ◽

K. WILSON

Keyword(s):

Coherent Structures ◽

Large Scale ◽

Combustion Instability

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Active Control of Combustion Instability Using Symmetric and Asymmetric Premix Fuel Modulation

Volume 6: Turbo Expo 2007, Parts A and B ◽

10.1115/gt2007-27342 ◽

2007 ◽

Cited By ~ 5

Author(s):

Daniel Guyot ◽

Christian Oliver Paschereit

Keyword(s):

Heat Release ◽

Closed Loop ◽

Modulation Frequency ◽

Combustion Instability ◽

Open Loop ◽

Closed Loop Control ◽

Nox Emissions ◽

Loop Control ◽

Asymmetric Modulation ◽

Control Schemes

Active instability control was applied to an atmospheric swirl-stabilized premixed combustor using open loop and closed loop control schemes. Actuation was realised by two on-off valves allowing for symmetric and asymmetric modulation of the premix fuel flow while maintaining constant time averaged overall fuel mass flow. Pressure and heat release fluctuations in the combustor as well as NOx, CO and CO2 emissions in the exhaust were recorded. In the open loop circuit the heat release response of the flame was first investigated during stable combustion. For symmetric fuel modulation the dominant frequency in the heat release response was the modulation frequency, while for asymmetric modulation it was its first harmonic. In stable open loop control a reduction of NOx emissions due to fuel modulation of up to 19% was recorded. In the closed loop mode phase-shift control was applied while triggering the valves at the dominant oscillation frequency as well as at its second subharmonic. Both, open and closed loop control schemes were able to successfully control a low-frequency combustion instability, while showing only a small increase in NOx emissions compared to, for example, secondary fuel modulation. Using premixed open loop fuel modulation, attenuation was best when modulating the fuel at frequencies different from the dominant instability frequency and its subharmonic. The performance of asymmetric fuel modulation was generally slightly better than for symmetric modulation in terms of suppression levels as well as emissions. Suppression of the instability’s pressure rms level of up to 15.7 dB was recorded.

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