Emission Measurements and CH* Chemiluminescence of a Staged Combustion Rig for Stationary Gas Turbine Applications

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Warren G. Lamont ◽  
Mario Roa ◽  
Scott E. Meyer ◽  
Robert P. Lucht
Keyword(s):  
Combustion Zone ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Exhaust Gas ◽  
Staged Combustion ◽  
High Pressure Turbine ◽  
Transverse Jet ◽  
Sampling Probe ◽  
Good Agreement

An optically accessible combustion rig was constructed to study the combustion characteristics of a reactive jet in a vitiated crossflow. The rig features two staged combustion zones. The main combustion zone is a swirl stabilized dump combustor. The second combustion zone, which is axially downstream from the main combustion zone, is formed by a transverse jet injecting either fuel or a premixed fuel/air mixture into the vitiated stream. The rig was designed to investigate the transverse jet conditions, equivalence ratio, and momentum ratios that produce low NOx and give an adequate temperature rise before the simulated high pressure turbine. A water-cooled sampling probe extracts exhaust gas downstream for emission measurements. As a baseline, the main combustion zone was fired without the transverse jet and the results compare closely to the work of previous researchers. The emission survey with the transverse jet found several conditions that show a benefit of staging compared to the baseline of firing only the main combustion zone. The flame structure from the transverse jet was captured using high speed CH* chemiluminescence, which shows the extent of the flame front and its penetration depth into the vitiated stream. The chemiluminescence images were averaged and compared to the Holdeman correlation, which showed good agreement for injection with fuel only but poorer agreement when premixed.

Dynamics and Stability Limits of Syngas Combustion in a Swirl-Stabilized Combustor

2008 ◽  
Author(s):  
Raymond L. Speth ◽  
H. Murat Altay ◽  
Duane E. Hudgins ◽  
Ahmed F. Ghoniem
Keyword(s):  
High Speed ◽  
Equivalence Ratio ◽  
Fluid Dynamic ◽  
Flame Structure ◽  
Low Frequency ◽  
Operating Conditions ◽  
Video Data ◽  
Combustion Dynamics ◽  
Lean Blowout ◽  
Operating Modes

The combustion dynamics, stability bands and flame structure of syngas flames under different operating conditions are investigated in an atmospheric pressure swirl-stabilized combustor. Pressure measurements and high-speed video data are used to distinguish several operating modes. Increasing the equivalence ratio makes the flame more compact, and in general increases the overall sound pressure level. Very close to the lean blowout limit, a long stable flame anchored to the inner recirculation zone is observed. At higher equivalence ratios, a low frequency, low amplitude pulsing mode associated with the fluid dynamic instabilities of axial swirling flows is present. Further increasing the equivalence ratio produces unstable flames oscillating at frequencies coupled with the acoustic eigenmodes. Additionally, a second unstable mode, coupled with a lower eigen-mode of the system, is observed for flames with CO concentration higher than 50%. As the amount of hydrogen in the fuel is increased, the lean flammability limit is extended and transitions between operating regimes move to lower equivalence ratios.

Experimental and Numerical Investigations of MILD Combustion in a Model Combustor Applied for Gas Turbine

2018 ◽  
Author(s):  
Huan Zhang ◽  
Zhedian Zhang ◽  
Yan Xiong ◽  
Yan Liu ◽  
Yunhan Xiao
Keyword(s):  
Gas Turbine ◽  
Reaction Zone ◽  
High Speed ◽  
Equivalence Ratio ◽  
Low Noise ◽  
Combustion Characteristics ◽  
Doppler Velocity ◽  
Exhaust Gas ◽  
Mild Combustion ◽  
Jet Velocity

The Moderate or Intense Low-oxygen Dilution (MILD) combustion is characterized by low emission, stable combustion and low noise for various kinds of fuel. MILD combustion is a promising combustion technology for gas turbine. The model combustor composed of an optical quartz combustor liner, four jet nozzles and one pilot nozzle has been designed in this study. The four jet nozzles are equidistantly arranged in the combustor concentric circle and the high-speed jet flows from the nozzles will entrain amount of exhaust gas to make MILD combustion occur. The combustion characteristics of the model combustor under atmosphere pressure have been investigated through experiments and numerical simulations. The influence of equivalence ratio and jet velocity on flow pattern, combustion characteristics and exhaust emissions were investigated in detail, respectively. Laser Doppler velocity (LDV) was utilized to measure the speed of a series of points in the model combustor. The measurement results show that a central recirculation existed in the combustion chamber. As the jet velocity of the nozzles increases, the amount of entrained mass by the jet increases simultaneously, however, the central recirculation zone is similar in shape and size. The recirculation of the model combustor will remain self-similar when the jet velocity varies in the range. The calculation model and method were verified through comparing with experimentally LDV data and be used to optimize the model combustor. Planar laser-induced fluorescence of hydroxyl radical (OH-PLIF) approaches were adopted to investigate the flame structure, the reaction zone and the OH distribution. OH distribution of the paralleled and crossed sections in the model combustor were measured, the whole reaction zone have been analyzed. The results show that the OH distribution was uniform in whole combustor. The exhaust gas composition of the combustor was measured by the “TESTO 350” Exhaust Gas Analyzer. All measurements emission results were corrected to 15% O2 in volume. Experimental results showed that NOx and CO emissions were less than 10 ppm@15%O2 when the equivalence ratio ranges from 0.63 to 0.8.

Liftoff behaviors and flame structure of dimethyl ether jet flame in CH4/air vitiated coflow

2019 ◽  
Vol 233 (8) ◽  
pp. 1039-1046 ◽  
Author(s):  
Wei Fu ◽  
Fengyu Li ◽  
Haitao Zhang ◽  
Bolun Yi ◽  
Yanju Liu ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Jet Flames ◽  
Jet Flame ◽  
Field Temperature ◽  
Vitiated Coflow

The objective of this paper is to investigate the flame structure and liftoff behaviors of a dimethyl ether central jet in CH4/air vitiated coflow in a coflow burner. The liftoff behaviors of dimethyl ether jet flames in the air flow were studied firstly. The flame stability of the burner was analyzed by measuring the flow field temperature with thermocouples. By changing the coflow rate and CH4 equivalence ratio, the liftoff behaviors of dimethyl ether jet flames under different vitiated coflow environments were discussed. The jet flame structure was also analyzed qualitatively by high-speed photography.

Application of Proper Orthogonal Decomposition to High Speed Imaging for the Study of Combustion Oscillations

2017 ◽  
Author(s):  
Siddhartha Gadiraju ◽  
Suhyeon Park ◽  
David Gomez-Ramirez ◽  
Srinath V. Ekkad ◽  
K. Todd Lowe ◽  
...  
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Low Frequency ◽  
Orthogonal Decomposition ◽  
Pressure Measurements ◽  
High Speed Imaging ◽  
Flame Structures ◽  
Proper Orthogonal

The flame structure and characteristics generated by an industrial low emission, lean premixed, fuel swirl nozzle were analyzed for understanding combustion oscillations. The experimental facility is located at the Advanced Propulsion and Power Laboratory (APPL) at Virginia Tech. The experiments were carried out in a model optical can combustor operating at atmospheric pressures. Low-frequency oscillations (<100 Hz) were observed during the reaction as opposed to no reaction, cold flow test cases. The objective of this paper is to understand the frequency and magnitude of oscillations due to combustion using high-speed imaging and associate them with corresponding structure or feature of the flame. Flame images were obtained using a Photron Fastcam SA4 high-speed camera at 500 frames per second. The experiments were conducted at equivalence ratios of 0.65, 0.75; different Reynolds numbers of 50K, 75K; and three pilot fuel to main fuel ratios of 0%, 3%, 6%. In this study, Reynolds number was based on the throat diameter of the fuel nozzle. Since the time averaged flame images are not adequate representation of the flame structures, proper orthogonal decomposition (POD) was applied to the flame images to extract the dominant features. The spatiotemporal dynamics of the images can be decomposed into their constituent modes of maximum spatial variance using POD so that the dominant features of the flame can be observed. The frequency of the dominant flame structures, as captured by the POD modes of the flame acquisitions, were consistent with pressure measurements taken at the exit of the combustor. Thus, the oscillations due to combustion can be visualized using POD. POD was further applied to high-speed images taken during instabilities. Specifically, the instabilities discussed in this paper are those encountered when the equivalence ratio is reduced to the levels approaching lean blowout (LBO). As the equivalence ratio is reduced to near blowout regime, it triggers low-frequency high amplitude instabilities. These low-frequency instabilities are visible as the flapping of the flame. The frequencies of the dominant POD modes are consistent with pressure measurements recorded during these studies.

Emission Measurements and OH-PLIF of Reacting Hydrogen Jets in Vitiated Crossflow for Stationary Gas Turbines

2012 ◽  
Author(s):  
Mario Roa ◽  
Warren G. Lamont ◽  
Scott E. Meyer ◽  
Peter Szedlacsek ◽  
Robert P. Lucht
Keyword(s):  
Gas Turbines ◽  
Combustion Zone ◽  
Flame Structure ◽  
Combustion Process ◽  
Test Rig ◽  
Gas Turbine Combustor ◽  
Depth Of Penetration ◽  
Jet In Crossflow ◽  
Air Jet ◽  
Sampling Probe

An optically accessible gas turbine combustor test rig was constructed to study the combustion characteristics of a coaxial hydrogen/air jet injected into a vitiated swirl crossflow. The test rig has two combustion zones. The main combustion zone (MCZ) is a swirl stabilized dump combustor, and the secondary combustion zone (SCZ) is a reacting crossflow jet, referred to as the jet-in-crossflow (JIC). The SCZ is located downstream of the MCZ. The JIC is a coaxial hydrogen/air jet that penetrates radially into the vitiated stream. The combustor was designed to study the effects of JIC conditions on the SCZ combustion process and in particular on NOx production. The jet velocity and equivalence ratio were systematically varied. A water-cooled sampling probe was used to extract exhaust gases downstream of the SCZ for emission measurements. The JIC flame structure was captured by OH-PLIF images which show the extent of the flame front and the depth of penetration into the vitiated stream. The OH-PLIF images were averaged to determine the JIC reaction zone and were compared to the Holdeman correlation.

An Investigation of the Effects of Fuel Staging on Flame Structure in a Gas Turbine Model Combustor

2013 ◽  
Author(s):  
J. D. Gounder ◽  
I. Boxx ◽  
P. Kutne ◽  
F. Biagioli ◽  
H. Luebcke
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Laser Diagnostics ◽  
Thermal Power ◽  
Flame Structure ◽  
Operating Conditions ◽  
Fuel Staging ◽  
Turbine Model

Gas turbine (GT) flames at lean operating conditions are susceptible to instabilities that can lead to unsteady operation, flame extinction, and thermoacoustic oscillations. High speed (10 kHz) laser and optical diagnostic techniques have been used to investigate the effect of fuel staging on the mechanisms involved in such instabilities and the overall performance of a gas turbine model combustor. The GT burner used in this study consists of coaxial swirlers which allow for fuel staging capability, where the fuel is varied from 100% to 20% fuel injection in the inner swirler. The burner is equipped with a combustion chamber with large quartz windows, allowing for the application of optical and laser diagnostics. Simultaneous high speed OH Planar Laser Induced Fluorescence (PLIF) and OH* chemiluminescence (CL) imaging, exhaust gas sampling and acoustic measurements were applied to characterize the flames and determine the operability limits of the combustor. Methane air flames at atmospheric pressure have been investigated at a constant thermal power of 58 kW. The global equivalence ratio was kept constant, while the fuel staging was varied. The bulk flow velocity at the exit plane was kept constant at 20 m/s. Simultaneous high speed particle image velocity (PIV) and OH PLIF measurements were performed at a repetition rate of 10 kHz on specifically chosen flames with a fixed staging and equivalence ratio. This paper will present the flame and the flow field structure resolved using the kHz measurement technique. The interaction between the velocity field and the flame front marked by the OH LIF will be presented. The mean PIV image provides the location of the inner and outer recirculation zones. The flame structure presented in this paper will also show the effectiveness of fuel mixing as the staging is varied. The changes in flame shape with variation in fuel staging is determined using the OH* chemiluminescence images. As the fuel flow in the inner swirler is reduced, the NOx and CO emissions also reduce and reach a minimum at a staging of 45% fuel being injected in the inner swirler. As fuel injection in the outer swirler increases beyond 60% the NOx and CO emissions start also increasing.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

Implementing variable valve actuation on a diesel engine at high-speed idle operation for improved aftertreatment warm-up

2019 ◽  
Vol 21 (7) ◽  
pp. 1134-1146
Author(s):  
Kalen R Vos ◽  
Gregory M Shaver ◽  
Mrunal C Joshi ◽  
James McCarthy
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
Exhaust Valve ◽  
Exhaust Gas ◽  
Warm Up ◽  
Aftertreatment System ◽  
Idle Speed ◽  
Variable Valve Actuation ◽  
Brake Mean Effective Pressure ◽  
Valve Opening

Aftertreatment thermal management is critical for regulating emissions in modern diesel engines. Elevated engine-out temperatures and mass flows are effective at increasing the temperature of an aftertreatment system to enable efficient emission reduction. In this effort, experiments and analysis demonstrated that increasing the idle speed, while maintaining the same idle load, enables improved aftertreatment “warm-up” performance with engine-out NOx and particulate matter levels no higher than a state-of-the-art thermal calibration at conventional idle operation (800 rpm and 1.3 bar brake mean effective pressure). Elevated idle speeds of 1000 and 1200 rpm, compared to conventional idle at 800 rpm, realized 31%–51% increase in exhaust flow and 25 °C–40 °C increase in engine-out temperature, respectively. This study also demonstrated additional engine-out temperature benefits at all three idle speeds considered (800, 1000, and 1200 rpm, without compromising the exhaust flow rates or emissions, by modulating the exhaust valve opening timing. Early exhaust valve opening realizes up to ~51% increase in exhaust flow and 50 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder via an early blowdown of the exhaust gas. This early blowdown of exhaust gas also reduces the time available for particulate matter oxidization, effectively limiting the ability to elevate engine-out temperatures for the early exhaust valve opening strategy. Alternatively, late exhaust valve opening realizes up to ~51% increase in exhaust flow and 91 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder to pump in-cylinder gases across a smaller exhaust valve opening. In short, this study demonstrates how increased idle speeds, and exhaust valve opening modulation, individually or combined, can be used to significantly increase the “warm-up” rate of an aftertreatment system.

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