Investigation into the combustion instability of synthetic natural gases using high speed flame images and their proper orthogonal decomposition

2016 ◽  
Vol 41 (45) ◽  
pp. 20731-20743 ◽  
Author(s):  
Ouk Choi ◽  
Min Chul Lee
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Instability ◽  
Orthogonal Decomposition ◽  
Natural Gases ◽  
Proper Orthogonal

Advanced Identification of Coherent Structures in Swirl-Stabilized Combustors

2016 ◽  
Author(s):  
Moritz Sieber ◽  
Christian Oliver Paschereit ◽  
Kilian Oberleithner
Keyword(s):  
Heat Release ◽  
Proper Orthogonal Decomposition ◽  
Coherent Structures ◽  
High Speed ◽  
Low Frequency ◽  
Orthogonal Decomposition ◽  
Time Resolved ◽  
Operation Conditions ◽  
Natural Dynamics ◽  
Proper Orthogonal

We present an application of a newly introduced method to analyze the time-resolved experimental data from the flow field of a swirl-stabilized combustor. This method is based on classic proper orthogonal decomposition (POD) extended by a temporal constraint. The filter operation embedded in this method allows for continuous fading from the classic POD to the Fourier mode decomposition. This new method — called spectral proper orthogonal decomposition (SPOD) — allows for a clearer separation of the dominant mechanisms due to a clean spectral separation of phenomena. In this paper, the fundamentals of SPOD are shortly introduced. The actual focus is put on the application to a combustor flow. We analyze high-speed PIV measurements from flow fields in a combustor at different operation conditions. In these measurements, we consider externally actuated, as well as natural dynamics and reveal how the natural and actuated modes interact with each other. As shown in the paper, SPOD provides detailed insight into coherent structures in swirl flames. Two distinct PVC structures are found that are very differently affected by acoustic actuation. The coherent structures are related to heat release fluctuations, which are derived from simultaneously acquired OH* chemiluminescence measurements. Besides the actuated modes, a low frequency mode was found that significantly contribute to the global heat release fluctuations.

Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Penghui Ge ◽  
David L. S. Hung
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Process ◽  
Flow Characteristics ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Flow Fields ◽  
Swirl Flow ◽  
Orthogonal Decomposition ◽  
Proper Orthogonal

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct injection (SIDI) engine affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under high swirl conditions. In addition, the cycle-to-cycle variations (CCVs) of swirl flow often degrade the air–fuel mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry (PIV) in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valves. Moreover, higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.

Study of Time-Resolved Vortex Structure of In-Cylinder Engine Flow Fields Using Proper Orthogonal Decomposition Technique

2014 ◽  
Author(s):  
Hanyang Zhuang ◽  
David L. S. Hung ◽  
Hao Chen
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Vortex Structure ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Flow Fields ◽  
Orthogonal Decomposition ◽  
Small Scale ◽  
Vortex Center ◽  
Time Resolved ◽  
Proper Orthogonal

The structure of in-cylinder flow field makes significant impacts on the processes of spray injection, air-fuel interactions, and flame development in internal combustion engines. In this study, the implementation of time-resolved Particle Image Velocimetry (PIV) in an optical engine is presented. Images at different crank angles have been taken using a high-speed double-pulsed laser and a high-speed camera with seeding particles mixed with the intake air. This study is focused on measuring the flow fields along the swirl plane at 30 mm below the injector tip under different intake air swirl ratios. A simple algorithm is presented to identify the vortex structure and to track the location and motion of vortex center at different crank angles. Proper Orthogonal Decomposition (POD) has been used to extract the ensemble and variation information of the vortex structure. Experimental results reveal that strong cycle-to-cycle variations exist in almost all test conditions. The vortex center is difficult to identify since multiple, but small scale, vortices exist during the early stage of the intake stroke. However, during the compression stroke when only one vortex center exists in most cycles, the motion of vortex center is found to be quite similar at different intake swirl ratios and engine speeds. This is due to the dominant driving force exerted by the piston’s upward motion on the in-cylinder air.

Proper Orthogonal Decomposition Analysis of Non-Swirling Turbulent Stratified and Premixed Methane/Air Flames

2014 ◽  
Author(s):  
M. Mustafa Kamal ◽  
Christophe Duwig ◽  
Saravanan Balusamy ◽  
Ruigang Zhou ◽  
Simone Hochgreb
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Large Scale ◽  
Bluff Body ◽  
Decomposition Analysis ◽  
Orthogonal Decomposition ◽  
Stereoscopic Particle Image Velocimetry ◽  
Large Scale Flow ◽  
Proper Orthogonal

This paper reports proper orthogonal decomposition (POD) analyses for the velocity fields measured in a test burner. The Cambridge/Sandia Stratified Swirl Burner has been used in various studies as a benchmark for high resolution scalar and velocity measurements, for comparison with numerical model prediction. Flow field data was collected for a series of bluff-body stabilized premixed and stratified methane/air flames at turbulent, globally lean conditions (ϕ = 0.75) using high speed stereoscopic particle image velocimetry (HS-SPIV). In this paper, a modal analysis was performed to identify the large scale flow structures and their impact on the flame dynamics. The high speed PIV system was operated at 3 kHz to acquire a series of 4096 sequential flow field images both for reactive and non-reactive cases, sufficient to follow the large-scale spatial and temporal evolution of flame and flow dynamics. The POD analysis allows identification of vortical structures, created by the bluff body, and in the shear layers surrounding the stabilization point. In addition, the analysis reveals that dominant structures are a strong function of the mixture stratification in the flow field. The dominant energetic modes of reactive and non-reactive flows are very different, as the expansion of gases and the high temperatures alter the unstable modes and their survival in the flow.

Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition

2016 ◽  
Author(s):  
Penghui Ge ◽  
David L. S. Hung
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Process ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Flow Fields ◽  
Swirl Flow ◽  
Orthogonal Decomposition ◽  
Fuel Spray ◽  
Proper Orthogonal

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct-injection (SIDI) affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under higher conditions. In addition, the cycle-to-cycle variations of swirl flow often degrade the fuel spray mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles during the intake and compression strokes. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the time coefficients of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valve. Moreover, the higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.

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