Active control of combustion oscillations in a lean premixed combustor by secondary fuel injection coupling with chemiluminescence imaging technique

2007 ◽  
Vol 31 (2) ◽  
pp. 3225-3233 ◽  
Author(s):  
Shigeru Tachibana ◽  
Laurent Zimmer ◽  
Yoji Kurosawa ◽  
Kazuo Suzuki
Keyword(s):  
Active Control ◽  
Fuel Injection ◽  
Imaging Technique ◽  
Lean Premixed ◽  
Secondary Fuel

Damping of Combustion Instabilities Through Pseudo-Active Control

2018 ◽  
Author(s):  
Jesús Oliva ◽  
Ennio Luciano ◽  
Javier Ballester
Keyword(s):  
Combustion Chamber ◽  
Active Control ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Pressure Oscillation ◽  
Practical Reasons ◽  
Fuel Injector ◽  
Secondary Fuel ◽  
Pilot Fuel ◽  
Instability Control

Active instability control techniques have demonstrated very good capabilities to correct combustion oscillations but, due to high costs and other practical reasons, have not achieved the success expected in gas turbines engines. A different approach, named here as ‘pseudo-active instability control’, has been explored and the first results are presented in this work. In this case, the flow of non-premixed pilot fuel is modulated by passive methods: the pressure oscillation in the combustion chamber induces a velocity fluctuation at the secondary fuel injector. In principle, damping of the instability may be achieved if the heat release oscillations due to the secondary fuel are out of phase with those of the main flame. This work reports a first exploration of this strategy, aimed mainly at performing a proof of the concept. An experimental study has been carried out in a laboratory premixed combustor with pilot fuel injection. The relationship between the fluctuations of pressure in the combustion chamber and those of velocity at the injector was studied both experimentally (hot wire anemometry) and theoretically (1-D acoustic model of the injection line). Combustion tests in limit cycle conditions demonstrated that modifications in the geometry of the secondary injection affected the pressure fluctuations inside the combustion chamber. Depending on the geometry (and, hence, acoustic impedance), the instability was enhanced or damped. This demonstrates that the proposed ‘pseudo-active control’ can produce similar effects (at least, qualitatively) to those of active control, but only using passive means, as initially postulated.

Active Control of Combustion Instabilities in Gas Turbine Burners

2006 ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
Gas Turbine ◽  
Active Control ◽  
Closed Loop ◽  
Fuel Injection ◽  
Nox Emissions ◽  
Modulation Amplitude ◽  
Symmetric Mode ◽  
Instability Mode ◽  
Secondary Fuel ◽  
Symmetric Instability

This paper gives an overview of open and closed loop active control methodologies used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main pre-mixed combustion or alternatively in secondary pilot fuel. For the main premix fuel supply two methods of fuel injection modulations were tested: symmetric and asymmetric injection. The tests showed that the closed loop asymmetric modulations were more effective in the suppression of the symmetric mode instability than symmetric fuel excitation. Symmetric excitation was quite efficient in abating the symmetric mode as well, however, at a certain range of phase shift the combustion was destabilized to an extent that caused blow out of the flame. Using premixed open loop fuel modulations the symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. Secondary fuel injection in a pilot flame was used to control low frequency symmetric instability and high frequency helical instability. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20 dB was recorded.

Industrial Trent Combustor — Combustion Noise Characteristics

1999 ◽  
Author(s):  
Thomas Scarinci ◽  
John L. Halpin
Keyword(s):  
Fuel Injection ◽  
Power Level ◽  
Technical Problem ◽  
Combustion Noise ◽  
Ambient Conditions ◽  
Noise Mapping ◽  
Noise Characteristics ◽  
Lean Premixed ◽  
In Series ◽  
Three Stages

Thermoacoustic resonance is a difficult technical problem that is experienced by almost all lean-premixed combustors. The Industrial Trent combustor is a novel dry-low-emissions (DLE) combustor design, which incorporates three stages of lean premixed fuel injection in series. The three stages in series allow independent control of two stages — the third stage receives the balance of fuel to maintain the desired power level — at all power conditions. Thus, primary zone and secondary zone temperatures can be independently controlled. This paper examines how the flexibility offered by a 3-stage lean premixed combustion system permits the implementation of a successful combustion noise avoidance strategy at all power conditions and at all ambient conditions. This is because at a given engine condition (power level and day temperature) a characteristic “noise map” can be generated on the engine, independently of the engine running condition. The variable distribution of heat release along the length of the combustor provides an effective mechanism to control the amplitude of longitudinal resonance modes of the combustor. This approach has allowed the Industrial Trent combustion engineers to thoroughly “map out” all longitudinal combustor acoustic modes and design a fuel schedule that can navigate around regions of combustor thermoacoustic resonance. Noise mapping results are presented in detail, together with the development of noise prediction methods (frequency and amplitude) that have allowed the noise characteristics of the engine to be established over the entire operating envelope of the engine.

Combustion Instability and Emission Control by Pulsating Fuel Injection

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
High Frequency ◽  
Fuel Injection ◽  
Low Frequency ◽  
Nox Emissions ◽  
Modulation Amplitude ◽  
Pulsation Frequency ◽  
Symmetric Mode ◽  
Instability Mode ◽  
Secondary Fuel ◽  
Symmetric Instability

Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20dB was recorded. High frequency instabilities were suppressed by 38dB, and CO emissions reduced by using low frequency modulations with 10% duty cycle.

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