Self-oscillation Research Articles

Numerical simulation of nonlinear phenomena in a standing-wave thermoacoustic engine with gas-liquid coupling oscillation

• A CFD model of gas-liquid standing-wave thermoacoustic engine is developed and experimentally verified. • Time-domain impedance boundary condition is employed to truncate the modelling of liquid column. • Entire transient evolution of self-excited thermoacoustic oscillation from onset to saturation is captured. • Three different acoustic streamings are observed through inspecting the time-averaged mass flux field. A computational fluid dynamics (CFD) model based on the compressible, nonlinear Navier-Stokes equations is developed to simulate the nonlinear phenomena in a gas-liquid standing-wave thermoacoustic engine, which employs gas as the working fluid and liquid as the phase-matching element. The CFD model is well validated when comparing the simulated onset and steady-state performances with those measured from a real experimental system. Based on the CFD model, the nonlinear phenomena of the engine are analyzed from three aspects. Firstly, the nonlinear dynamic phenomena of self-excited thermoacoustic oscillation from onset to saturation are investigated, focusing on onset temperature difference and steady-state pressure amplitude. Then, the nonlinear acoustic phenomena of the engine operating at steady state are analyzed. The steady-state fluctuating pressure is decomposed into a superimposition of the acoustic modes with different frequencies, which reveals the existence of high-order harmonics. Finally, the nonlinear hydrodynamic phenomena including multi-dimensional flow effect and mass streaming are observed by examining the steady-state flow fields in the engine. The proposed CFD model provides an effective approach to comprehending the mechanism of nonlinear phenomena in gas-liquid coupling thermoacoustic engines.

Experimental investigation on concrete rock breaking performance of self-excited oscillation pulsed waterjet

To obtain the influence of structural parameters, system pressure, standoff distance, rock characteristics on rock breaking volume and specific energy consumption, the rock breaking experiment using self-excited oscillation pulsed waterjet (SOPW) was carried out. The relationship among rock initial crushing pressure, fracturing pressure with rock compressive strength was investigated, and the change trend between rock breaking morphology and standoff distance was also observed. In addition, the order and optimal parameter combination of influential factors on rock breaking performance using SOPW was obtained through an orthogonal test. The research results show that the rock breaking performance under the impact of SOPW is better than that of continuous water jet in the initial stage, and the difference of rock breaking volume under the action of two-type jet is getting larger as the time going on. Moreover, the initial crushing pressure and fracturing pressure increases with the increase of the compressive strength, and the initial crushing pressure and the fracturing pressure is predicted as 54.4 MPa and 125.8 MPa, respectively, when the rock compressive strength is 80 MPa. Furthermore, the primary and secondary order of various factors on rock breaking performance is system pressure, standoff distance, oscillation cavity length, section cone angle, and the optimal combination is 40 MPa, 10 mm, 70 mm, and 140° for the system pressure, standoff distance, oscillation cavity length and section cone angle, respectively.

Characteristics of cavitation onset and development in a self-excited fluidic oscillator

Hydrodynamic cavitation has been widely employed in modern chemical technology. A high-speed camera experiment is conducted to reveal the characteristics of hydrodynamic cavitation generated in one self-excited fluidic oscillator. The images obtained from the high-speed camera system are employed to describe several development stages of the hydrodynamic cavitation. The gray intensity of the images which is the volume of bubbles formed is extracted to distinguish the cavitation bubbles from the water. It is found that three regions in the fluidic oscillator could be divided according to the distance from the entrance. The inception of cavitation occurs in the region nearest the entrance. For a relatively low inlet flow rate, the whole process of cavitation could complete within the region that is the second nearest the entrance as a low pressure area appears periodically in this region. For a high inlet flow rate, the vortexes in the region farthest from the entrance are able to generate sufficient low pressures to induce the generation of cavitation. In addition, the intensity of cavitation could be reflected by the cavitation number in a self-excited fluidic oscillator.

A high-dimensional model to study the self-excited oscillations of rotary drilling systems

This paper analyzes the self-excited axial and torsional vibrations of rotary drilling systems with a model that combines a multi-degrees of freedom representation of the drilling structure with a rate-independent bit-rock interface law. The state-dependent delay introduced by the bit-rock interaction is captured by a bit trajectory function, which leads to the formulation of a nonlinear system of coupled partial differential equation (PDE) and ordinary differential equations (ODEs). This paper describes an algorithm that utilizes the Chebyshev spectral method to convert the system of PDE–ODEs into a system of coupled ODEs. The use of Chebyshev polynomials rather than Fourier series leads to a computationally more efficient algorithm, in view of the non-periodic nature of the bit trajectory function. By linearizing the system of coupled PDE–ODEs, this algorithm is further extended to assess numerically the stability of the high-dimensional model. The predictions of the linear stability analysis are validated with published results as well as with time-domain simulations. It is shown, as anticipated by Liu et al. (2014), that the stable region in the space of the operating parameters shrinks with increasing spatial resolution of the high-dimensional model, suggesting that the effects of damping on the stability of drilling system is generally negligible in the range of practical drilling parameters. Extensive parametric studies have been carried out using the high-dimensional model to analyze the influence of various factors on the torsional stick–slip oscillations. The bit wearflats are shown to play an important role in delaying or even suppressing the occurrence of torsional stick–slip oscillations. Finally, the axial vibrations propagating along the drillstring are revealed in the form of traveling waves, whereas the torsional vibrations take the form of standing waves, whose frequency is the same as the torsional resonance of the drillstring excited by the bit-rock interaction.

Research on Oscillation Suppression Methods in Shunt Active Power Filter System

The shunt active power filter (SAPF) system oscillation is a massive threat to the security and stability of the power grid. This study classifies SAPF oscillation into two categories according to the difference in mechanisms. The SAPF oscillation in one category is caused by the resonant characteristics of a switching noise filter and is called external loop amplification. The SAPF oscillation in the other category is induced by the presence of a capacitor in the load current for SAPF and is called self-excited oscillation. Unlike previous studies, this study tried to reveal the internal relationship between the two kinds of SAPF oscillation, present a general shunt virtual-damping-based SAPF oscillation suppression strategy covering the previous resonant damping method, and provide the discrete domain stability criterion of the control system. The sampling frequency was at least six times the resonant frequency. The stability region was enlarged with an increase in the sampling frequency and narrowed with a rise in the resonant frequency. As to the harmful self-excited oscillation problem, this study proposes a composite control strategy combining selective harmonic compensation and grid-side current feedback. Moreover, this study considers the more general resistance–inductance–capacitance load situations and analyzes the stability of the SAPF–Thyristor Switched Capacitor (TSC) hybrid compensation system. Simulations and experiments demonstrated that the proposed compound control method can reduce the primary harmonics of the system by more than 90% and has a better oscillation suppression performance than previous suppression methods. In particular, if we selected the TSC series reactance rate following more than 6%, self-excited oscillation could usually be avoided.

Study on Self-Excited Oscillation Suppression of Supersonic Inlet Based on Parallel Cavity

Aiming at the problem of self-excited oscillation in a supersonic inlet, the oscillation suppression of parallel cavities in a shock system is studied. Based on the shock dynamic model, the theoretical calculation model of parallel cavity under dynamic shock is established, and the effects of cavity volume and oscillation frequency on shock oscillation flow field parameters are analyzed. On this basis, an integrated numerical model including cavity and inlet and outflow fields is established, and the effects of cavity on the inlet flow field parameter distribution and parameter oscillation are compared by using unsteady numerical calculation algorithm. The theoretical calculation results show that the parallel cavity can reduce the amplitude of flow field pressure oscillation, and increasing the cavity volume is beneficial to suppress parameter oscillation. The unsteady numerical calculation of three groups of working conditions shows that the cavity changes the amplitude of parameter oscillation, and the high amplitude frequency point also decreases compared to the model without cavity. Through the alternating change of pressure between the channel and cavity during the movement of the shock wave, the cavity gas filling and overflow dampen the shock wave forward and pressure change of the mainstream, so as to suppress the self-excited oscillation.

Oscillation of Cavitating Vortices in Draft Tubes of a Simplified Model Turbine and a Model Pump–Turbine

The self-oscillation of the cavitating vortices is one of the dangerous phenomena of hydraulic turbine operation near full-load conditions. This work is an attempt to generalize data and expand insight on the phenomenon of self-excited oscillations by comparing the experimental results obtained on a simplified turbine and scaled-down pump–turbine models. In both cases, a series of high-speed imaging was carried out, which made it possible to study these phenomena with high temporal resolution. The high-speed imaging data was subjected to additional processing such as binarization, cropping, and scaling. For a simplified turbine model, the volume of the vapor cavity was calculated based on the assumption of the axial symmetry of the cavity, after which fast Fourier transform (FFT) analysis was carried out. A proper orthogonal decomposition (POD) analysis was also performed to examine individual modes in the original digital imaging data. For the pump–turbine, visualization data on the cavitation cavity oscillations were supplemented by pressure measurements in the draft tube cone to determine the frequency characteristics. Based on obtained experimental data, an improved one-dimensional model describing the oscillations of the cavitation cavity arising behind the hydraulic turbine runner is proposed.

A Light-Powered Liquid Crystal Elastomer Spring Oscillator with Self-Shading Coatings.

The self-oscillating systems based on stimuli-responsive materials, without complex controllers and additional batteries, have great application prospects in the fields of intelligent machines, soft robotics, and light-powered motors. Recently, the periodic oscillation of an LCE fiber with a mass block under periodic illumination was reported. This system requires periodic illumination, which limits the application of self-sustained systems. In this paper, we creatively proposed a light-powered liquid crystal elastomer (LCE) spring oscillator with self-shading coatings, which can self-oscillate continuously under steady illumination. On the basis of the well-established dynamic LCE model, the governing equation of the LCE spring oscillator is formulated, and the self-excited oscillation is studied theoretically. The numerical calculations show that the LCE spring oscillator has two motion modes, static mode and oscillation mode, and the self-oscillation arises from the coupling between the light-driven deformation and its movement. Furthermore, the contraction coefficient, damping coefficient, painting stretch, light intensity, spring constant, and gravitational acceleration all affect the self-excited oscillation of the spring oscillator, and each parameter is a critical value for triggering self-excited oscillation. This work will provide effective help in designing new optically responsive structures for engineering applications.

Determination of the heat conduction transfer function within the thermoacoustic instability limit cycle in a Rijke tube

In this work, experimental measurements of the heat conduction transfer function (HCTF) within the limit cycle of thermoacoustic instabilities were conducted associated with a feedback controller. The responses of the heat conduction from the heater to the air in the vicinity to the oncoming flow disturbance can be described as the HCTF. When self-excited thermoacoustic instability occurs, it is not possible to measure the HCTF. The measurement experiment is twofold. Firstly, the active feedback control is applied to suppress the self-excited thermoacoustic oscillation in the Rijke tube. Secondly, the two-microphone method is applied to achieve the measurement of the HCTF at different working conditions. Experimental results show that the mean air flow velocity has an effect on the attenuation time of the thermoacoustic oscillation. Both of the mean air flow velocity and the electric-heating power have a significant effect on HCTFs.

Large-eddy simulations of self-excited thermoacoustic instability in a premixed swirling combustor with an outlet nozzle

Reducing the footprint of greenhouse gases and nitrogen oxides (NOx) emissions from combustion systems means that they have been operating under lean or ultra-lean fuel–air premixed conditions. Under such conditions, self-excited large-amplitude pulsating thermoacoustic instabilities may occur, characterized by deafening combustion noises and even “violent” structural vibrations, which is, therefore, highly undesirable in practice. By conducting chemical reaction-thermodynamics-acoustics-swirling flow coupling investigations, we have numerically explored the generation and mitigation mechanisms of self-excited pulsating oscillations in a methane-fueled swirling combustor in the presence and absence of an outlet nozzle. Hence, a large-eddy simulation was performed on a fully three-dimensional compressible flow via an open-source platform, OpenFOAM. Furthermore, a thorough assessment was made to understand the fundamental physics of the interaction of the swirling flame, either constructively or destructively, to the acoustic pressure perturbations by examining the local Rayleigh criterion/index. A further explanation was made on implementing the outlet nozzle that can mitigate such periodic pulsating combustion via attenuating the fuel fraction fluctuations, vortices processing, and changing temperature field. It was also found that the dominant pulsating mode is switched from the 1/4 standing-wave wavelength mode to the 3/4 wavelength mode. Finally, more physical insights were obtained by conducting a proper orthogonal decomposition analysis on the energy distribution between the thermoacoustic modes.

Effect of Different Cooling Methods on Thermal Performance of Single Loop Pulsating Heat Pipe

A pulsating heat pipe (PHP) is a promising two-phase passive thermal device that consists of a capillary tube meandering between an evaporator and a condenser. Heat is transferred from the evaporator to the condenser by the self-excited oscillation of vapor and liquid. The complete knowledge of the heat transport mechanisms, particularly at the operating limit of PHPs, is far from satisfactory. In PHP, the phase-change acts as a driving force of the self-excited oscillation of the fluid. In this context, the condensation highly affects the performance of PHPs, while few studies have investigated the effect of the sink temperature or the cooling methods. In this study, a single metallic loop is tested to understand the local phenomena focusing on the impact of cooling methods of the condenser section: natural convection and forced air convection. Regardless of the cooling methods, the PHP showed the intermittent and unstable oscillation at low power input just after the start-up, and then continued to operate stably until the heater turned off after the evaporator temperature exceeds 140 °C. The resistance of natural convection cooling is more than 1 K/W lower than that of forced convection cooling, for the same heat input conditions. However, the resistance of both cooling methods at the same evaporator temperature shows a good agreement. The resistance is inversely proportional to the evaporator temperature as well as the heat input.

Numerical investigation on oscillations characteristics of self-excited thermoacoustic system forced by acoustic wave

Self-excited thermoacoustic oscillations usually occur in many practical systems such as rocket motors, gas turbines and cryogenic distribution systems. We study the dynamics of a self-excited cryogenic thermoacoustic system subjected to acoustic forcing. The effect of the driving phase on the amplitude of the coupled oscillation is analyzed and the results present two states. To provide a guide for the selection of driving signal, the dynamics of a self-excited cryogenic thermoacoustic system subjected to acoustic forcing are investigated. When ϕ=30°, the radius of the limit cycle gradually shrinks, and self-oscillation amplitude is suppressed by 99.5%. For small driving phase, the self-oscillation can be suppressed, while for large driving phase, the phase portraits depict period-1 limit cycle oscillations. The results show that excessive driving phase has unfavorable effect on self-excited oscillation, and small drive phase can achieve oscillation suppression better. To reveal the coupling mechanism of externally forced oscillation and system self-excited oscillation, the phase relationships between self-excited oscillations and coupling pressure fluctuation waves in different periods are analyzed. Hence, the work indicates that under low-frequency disturbances, the system oscillation will have a phase delay, which will cause the hysteresis dissipation and restrain the system oscillation.

Study on nonlinear dynamic behavior and stability of aviation pressure servo valve-controlled cylinder system

In this paper, aiming at the phenomenon of self-excited oscillation caused by nonlinear factors in a large aircraft wheel brake control system, the nonlinear dynamic behavior of the pressure servo valve-controlled cylinder system (PSVCS) is studied, and the influence law of the key parameters on the nonlinear self-excitation behavior is obtained. On this basis, the stability of the PSVCS is analyzed both in time domain and frequency domain, and it is proved in principle that the PSVCS is a stable self-closed-loop control system. Firstly, the nonlinear dynamics model of the PSVCS is established in this paper. Secondly, using the method of phase plane analysis, the nonlinear dynamic behavior of the PSVCS and the influence law of key parameters on the system are studied. Thirdly, the nonlinear system of the PSVCS is transformed into a segmented local linear system, and the stability of the prestage and the power stage is analyzed, respectively. Finally, through a performance test platform, which is used to simulate the load of PSVCS, the theoretical analysis results of this paper are verified experimentally under different working conditions. The final experimental results show that both the nonlinear dynamic model established in this paper and the influence law of the key parameters obtained by the phase plane analysis on the nonlinear self-excited oscillation behavior are correct, and the relevant conclusions can provide a reference for the design of the braking system control system.

Effect of an external sound superimposed on the self-excited oscillation in a loop-tube thermoacoustic system

The influence of an external sound applied to a loop-tube type thermoacoustic system on the energy conversion efficiency is experimentally examined. The investigation is carried out by studying the effect of a loudspeaker (SP) set as an external sound source. As a result, it is found that the location of the SP affects the sound field in the system and that the amount of energy generated increases or decreases. The increasing or decreasing effect differs depending on the location of the SP. Furthermore, it is confirmed that, provided the SP is located near the particle velocity node, the sound energy can be increased by more than the input power to the SP without changing the sound field in the tube. From these results it can be confirmed that, similar to a straight-tube type thermoacoustic system, the energy conversion efficiency can be enhanced by locating the SP at a suitable position even in a loop-tube type system without end surfaces.

Numerical Study on Flow-Induced Noise of Deflector Jet Servo Valve Based on LES/Lighthill Hybrid Method

The flow-induced noise occurring in the prestage of the deflector jet servo valve (DJV) significantly affects the performance of DJV, which is a critical issue for electrohydraulic servo valves. To capture the root causes of flow-induced noise, DJV is numerically studied using computational aeroacoustics (CAA) methods in this paper. The acoustic field is investigated with Lighthill’s acoustic analogy based on the pulsation data from a large eddy simulation (LES). The flow-induced noise generation mechanism in DJV is revealed by analyzing the sound pressure level and vorticity distribution at different moments. Moreover, a kind of oscillation cavity model based on the Helmholtz oscillator is built, which reveals that the flow-induced noise is caused by self-excited oscillation and vortex. In addition, the result shows that continuous broadband dipole noise with medium- and high-frequency components of 1100 Hz and 2501 Hz dominates the DJV flow field. In order to avoid unexpected resonance, the natural frequency of the prestage should not coincide with the frequency of the flow oscillation frequency. Thus, this work can benefit the design and optimization of the prestage structure.

Single-frequency continuous-wave laser based on the novel Er/Yb-doped composite phosphosilicate fiber

Optical and laser properties of a new Er/Yb-doped composite optical fiber manufactured according to the “rod-in-tube” technique are presented. The fabricated composite fiber with a standard outer diameter of 125 μm was single-mode at the wavelength of 1.55 μm. A Fabry-Perot laser cavity was manufactured on a 25 mm long fiber segment using the femtosecond technique of Bragg gratings inscription. The resulting laser with an effective cavity length of 12 mm generated strictly continuouswave single-frequency radiation at a wavelength of 1548.3 nm at room temperature (295 K). The key advantage of the studied Er/Yb-doped composite fiber laser is the excellent temporal stability of the laser output without any tendency for self-excited oscillation mode at any pump level.

Flame describing function and combustion instability analysis of non-premixed coaxial jet flames

This study examines the effect of nonlinear flame dynamics on combustion instabilities in coaxial jet flames. The flame describing function (FDF) was used to establish this nonlinearity experimentally. The FDF gain was approximately constant despite velocity oscillation changes. However, the phase difference caused constructive interference to be converted into destructive interference as the velocity oscillations increased. With a closed boundary and external forcing, the initial velocity oscillation is damped from 200 to 240 Hz and amplified from 260 to 340 Hz. In the damping frequency range, the magnitude of the initial velocity oscillation decreases as the combustion chamber length decreases. When the velocity oscillates between 260 and 340 Hz, the combustion length that shows the maximum velocity oscillation varies from 200 to 500 mm and also decreases as the forcing frequency increases. This can be related to the resonant frequency that increases as the combustion chamber length decreases. There is no damping or amplification with other excitation frequencies. The self-excited pressure oscillations also occurred at a similar frequency range, which can amplify the initial velocity oscillation, but only for a combustor length of 350 mm. The second resonant frequency calculated via low-order combustion instability simulation, OSCILOS, is within the pressure oscillation range. The growth rate computed via OSCILOS exhibited a negative value, except for a combustor length of 350 mm. The growth rate also became negative as the velocity oscillations increased from 0.15 to 0.2 m/s. This could be related to a phase difference change in the FDF. The phase difference of the FDF is varied at only 300 Hz, and changes from in-phase to out-of-phase as the velocity oscillation increases from 0.1 to 0.15 m/s. The results of this study emphasize the importance of the FDF for combustion instability analysis.

Synchronization and chimeras in a network of four ring-coupled thermoacoustic oscillators

We take a complex systems approach to investigating experimentally the collective dynamics of a network of four self-excited thermoacoustic oscillators coupled in a ring. Using synchronization metrics, we find a wide variety of emergent multi-scale behaviour, such as (i) a transition from intermittent frequency locking on a $\mathbb {T}^{3}$ quasiperiodic attractor to a breathing chimera, (ii) a two-cluster state of anti-phase synchronization on a periodic limit cycle, and (iii) a weak anti-phase chimera. We then compute the cross-transitivity from recurrence networks to identify the dominant direction of the coupling between the heat-release-rate ($q^{\prime }_{\mathbb {X}}$) and pressure ($p^{\prime }_{\mathbb {X}}$) fluctuations in each individual oscillator, as well as that between the pressure ($p^{\prime }_{\mathbb {X}}$ and $p^{\prime }_{\mathbb {Y}}$) fluctuations in each pair of coupled oscillators. We find that networks of non-identical oscillators exhibit circumferentially biased $p^{\prime }_{\mathbb {X}}$–$p^{\prime }_{\mathbb {Y}}$ coupling, leading to mode localization, whereas networks of identical oscillators exhibit globally symmetric $p^{\prime }_{\mathbb {X}}$–$p^{\prime }_{\mathbb {Y}}$ coupling. In both types of networks, we find that the $p^{\prime }_{\mathbb {X}}$–$q^{\prime }_{\mathbb {X}}$ coupling can be symmetric or asymmetric, but that the asymmetry is always such that $q^{\prime }_{\mathbb {X}}$ exerts a greater influence on $p^{\prime }_{\mathbb {X}}$ than vice versa. Finally, we show through a cluster analysis that the $p^{\prime }_{\mathbb {X}}$–$p^{\prime }_{\mathbb {Y}}$ interactions play a more critical role than the $p^{\prime }_{\mathbb {X}}$–$q^{\prime }_{\mathbb {X}}$ interactions in defining the collective dynamics of the system. As well as providing new insight into the interplay between the $p^\prime_{\mathbb{X}}\text{--}p^\prime_{\mathbb{Y}}$ and $p^\prime_{\mathbb{X}}\text{--}q^\prime_{\mathbb{X}}$ coupling, this study shows that even a small network of four ring-coupled thermoacoustic oscillators can exhibit a wide variety of collective dynamics. In particular, we present the first evidence of chimera states in a minimal network of coupled thermoacoustic oscillators, paving the way for the application of oscillation quenching strategies based on chimera control.

Asynchronous and synchronous quenching of a globally unstable jet via axisymmetry breaking

We explore experimentally whether axisymmetry breaking can be exploited for the open-loop control of a prototypical hydrodynamic oscillator, namely a low-density inertial jet exhibiting global self-excited axisymmetric oscillations. We find that when forced transversely or axially at a low amplitude, the jet always transitions first from a period-1 limit cycle to $\mathbb {T}^2$ quasiperiodicity via a Neimark–Sacker bifurcation. However, we find that the subsequent transition, from $\mathbb {T}^2$ quasiperiodicity to $1:1$ lock-in, depends on the spatial symmetry of the applied perturbations: axial forcing induces a saddle-node bifurcation at small detuning but an inverse Neimark–Sacker bifurcation at large detuning, whereas transverse forcing always induces an inverse Neimark–Sacker bifurcation irrespective of the detuning. Crucially, we find that only transverse forcing can enable both asynchronous and synchronous quenching of the natural mode to occur without resonant or non-resonant amplification of the forced mode, resulting in substantially lower values of the overall response amplitude across all detuning values. From this, we conclude that breaking the jet axisymmetry via transverse forcing is a more effective control strategy than preserving the jet axisymmetry via axial forcing. Finally, we show that the observed synchronization phenomena can be modelled qualitatively with just two forced coupled Van der Pol oscillators. The success of such a simple low-dimensional model in capturing the complex synchronization dynamics of a multi-modal hydrodynamic system opens up new opportunities for axisymmetry breaking to be exploited for the open-loop control of other globally unstable flows.

Hybrid CFD/low-order modeling of thermoacoustic limit cycle oscillations in can-annular configurations

We propose a hybrid strategy for modeling non-linear thermoacoustic phenomena, e.g. limit-cycle (LC) oscillations, in can-annular combustion systems. The suggested model structure comprises a compressible CFD simulation limited to the burner/flame zone of one single can, coupled to a low-order model (LOM) representing the remaining combustor. In order to employ the suggested strategy for modeling non-linear phenomena like LC oscillations, the LOM must capture non-linear flame dynamics in the cans, which are not resolved by CFD. Instead of identifying such non-linear flame models in preliminary simulations, we aim at learning the non-linear dynamics “on-the-fly”, while simulating the self-excited system under consideration. Based on the observation of flame dynamics in the CFD domain, the parameters of the employed non-linear models are estimated during run time. The present study reveals that block-oriented models, which comprise a linear dynamic part followed by a static non-linear function, are well suited for this purpose. The proposed hybrid model is applied to a laminar can-annular combustor. Results agree well with the monolithic CFD simulation of the entire combustor, while the computational cost is drastically reduced. The employed flame models, whose parameters are identified during the simulation of the self-excited LC oscillation, represent well the relevant non-linear dynamics of the considered flame.