A review of active control approaches in stabilizing combustion systems in aerospace industry

Unsteady Combustor Physics

Feedback control of combustion oscillations

Open-loop control of self-excited flame pulsating oscillations and thermo-acoustic instability is considered in this work. The performance of the control strategy is numerically evaluated in a 2D Rijke-type combustor with a perforated pipe implemented. It is found that approximately 38 dB sound pressure level (SPL) reduction can be achieved by actively tuning the cooling flow through the perforated pipe. Furthermore, the vorticity-induced damping performance is contributing to the breaking up of flame-acoustics coupling. However, the shedding of vortices is not uniformly distributed along the perforated pipe. To apply the control strategy in practice and to validate the findings, experimental studies are performed on a customer-designed Rijke-type combustor with a perforated liner implemented. To mimic practical engines, a cooling flow generated by a centrifugal pump is provided to pass through the perforated pipe. Properly tuning the cooling flow rate is found to lead to the unstable combustor being successfully stabilized. SPL is reduced by approximately 35 dB at ω 1 / 2 π ≈ 245  Hz, and harmonic thermoacoustic modes are completely attenuating. Further study is conducted by suddenly removing the perforated pipe section. The combustion system is found to be associated with not only classical thermo-acoustic limit cycle oscillations with a dominant mode at 2.45 × 10 2  Hz, but also beating oscillations at 1.4 × 10 0  Hz. It is revealed that increasing acoustic losses by implementing the perforated pipe is another critical mechanism contributing to attenuating flame pulsating instability. The present work opens up an applicable means to attenuate both self-excited high-frequency thermoacoustic and low-frequency flame pulsating oscillations.

Mitigating self-excited flame pulsating and thermoacoustic oscillations using perforated liners

The continuous detonation engine (CDE) is based on detonation waves and is a new jet engine concept that is expected to bring a technical revolution to current aviation and aerospace propulsion sys...

Recent Progress, Development Trends, and Consideration of Continuous Detonation Engines

Time-resolved PIV of lean premixed combustion without and with porous inert media for acoustic control

High strength porous inert media (PIM) placed in the reaction zone of a swirl-stabilized lean-premixed combustor is a passive method of controlling combustion noise and instabilities. In this study, the effect of swirler location and swirl number on combustion without and with PIM has been investigated experimentally, using a methane-fueled quartz combustor at atmospheric pressure. Three axial swirlers were designed with 8 vanes, a solid centerbody, and vane angles of 30, 45, and 55 degrees to yield calculated swirl numbers of 0.45, 0.78, and 1.10, respectively. Swirler location was varied to obtain recess depth in the premixer tube of 0.0 cm, 2.5 cm, and 5.0 cm. A downstream bluff body was used with the recessed swirlers to stabilize the flame at the dump plane. Experiments were conducted at constant air flow rate of 300 SLPM and equivalence ratios of 0.70, 0.75, and 0.80. PIM annular rings with increasing and decreasing cross-sectional area in the flow direction were tested, referred to as diverging and converging PIM. The performance of each test case is compared by observing the flame behavior and measuring sound pressure level (SPL) with a microphone probe. Results include total SPL and SPL in one-third octave bands. PIM proved effective in mitigating combustion noise and instability for all flush-mounted swirlers with total SPL reductions of up to 7.6 dBA. The effectiveness of the PIM generally improved with increasing equivalence ratio. Combustion instability that occurred within the frequency band centered about 630 Hz was suppressed with both PIM configurations. These results confirm that PIM is an effective method to control combustion noise and instabilities in swirl-stabilized LPM combustion.Copyright © 2012 by ASME

Swirler Effects on Passive Control of Combustion Noise and Instability in a Swirl-Stabilized Combustor

Pressure gain combustion (PGC) has gained significant attention in airbreathing gas turbine applications due to its increased thermodynamic efficiency over a constant-pressure Brayton cycle. Rotati...

/pdf/novel-approach-for-computational-modeling-of-a-non-premixed-40cq5smsve.pdf

Novel Approach for Computational Modeling of a Non-Premixed Rotating Detonation Engine

In this study, a porous insert is placed at the dump plane of a swirl-stabilized lean premixed combustor to passively suppress thermoacoustic instabilities. The diffuser-shaped annular ring of poro...

https://journals.sagepub.com/doi/pdf/10.1177/1756827716642193

Passive control of thermoacoustic instabilities in swirl-stabilized combustion at elevated pressures:

In this study, ring-shaped porous inserts made from high-strength, temperature-resistant ceramic materials are utilized within the combustor to passively reduce noise and thermo-acoustic instabilities in lean direct injection (LDI) combustion. Inserts of 85% porosity; pore density of 18 pores per cm; and converging, diverging, and hyperbolic configurations are considered. Kerosene fuel atomized by an air-blast fuel injector is introduced in the swirl-stabilized combustor operated at atmospheric pressure. For a fixed equivalence ratio, emissions and acoustics measurements are obtained at different heat release rates and atomizing air to liquid mass ratios. Results show negligible effects of porous inserts on NOx and CO emissions at the combustor exit. Porous inserts are, however, very effective in suppressing both noise and thermo-acoustic instabilities for a range of operating conditions. The measured trends in acoustic absorption are predicted using a simplified thin-layer model of the porous material, a...

Joseph Meadows

Papers

Time-resolved PIV of lean premixed combustion without and with porous inert media for acoustic control

Swirler Effects on Passive Control of Combustion Noise and Instability in a Swirl-Stabilized Combustor

Novel Approach for Computational Modeling of a Non-Premixed Rotating Detonation Engine

Passive control of thermoacoustic instabilities in swirl-stabilized combustion at elevated pressures:

Porous Inserts for Passive Control of Noise and Thermo-Acoustic Instabilities in LDI Combustion