Modification of the Reaction Zone Using a Smart Fuel Injector for Control of Instabilities in Liquid Fueled Combustors

2005 ◽  
Author(s):  
T. Conrad ◽  
A. Bibik ◽  
D. Shcherbik ◽  
E. Lubarsky ◽  
B. T. Zinn
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Instability Modes ◽  
Droplet Sizes ◽  
Mass Flow Rates ◽  
The Stability ◽  
Flow Experiments

This paper describes an experimental investigation of suppressing combustion instabilities in a liquid fueled (n-heptane) atmospheric combustor incorporating an array of “smart” fuel injectors. These injectors were designed so that their spray properties could be manipulated without changing the overall operating conditions (power, mass flow rates, equivalence ratio, etc.) of the combustor. The dependence of these spray properties upon the smart injector settings was determined for a single injector using a series of cold flow experiments, including spray images and PDPA measurements of spray velocities and droplet sizes. The stability characteristics of a combustor incorporating seven such injectors were then determined and correlations were drawn between these characteristics, the single injector spray properties, and combustion behavior measurements taken for a single injector. It was shown that both longitudinal and tangential instability modes were excited in this combustor; the mechanisms of excitation and damping of these modes were then further investigated using high speed photography and spectroscopy measurements. Finally, suppression of both modes of instabilities in this combustor were demonstrated by slow tuning of the injector spray properties.

Vortex ring-like structures in gasoline fuel sprays under cold-start conditions

2009 ◽  
Vol 10 (4) ◽  
pp. 195-214 ◽  
Author(s):  
S Begg ◽  
F Kaplanski ◽  
S Sazhin ◽  
M Hindle ◽  
M Heikal
Keyword(s):  
Vortex Ring ◽  
High Speed ◽  
Phenomenological Study ◽  
Theoretical Models ◽  
High Speed Photography ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Fuel Sprays ◽  
Phase Doppler Anemometry ◽  
Ring Model

A phenomenological study of vortex ring-like structures in gasoline fuel sprays is presented for two types of production fuel injectors: a low-pressure, port fuel injector (PFI) and a high-pressure atomizer that injects fuel directly into an engine combustion chamber (G-DI). High-speed photography and phase Doppler anemometry (PDA) were used to study the fuel sprays. In general, each spray was seen to comprise three distinct periods: an initial, unsteady phase; a quasi-steady injection phase; and an exponential trailing phase. For both injectors, vortex ring-like structures could be clearly traced in the tail of the sprays. The location of the region of maximal vorticity of the droplet and gas mixture was used to calculate the temporal evolution of the radial and axial components of the translational velocity of the vortex ring-like structures. The radial components of this velocity remained close to zero in both cases. The experimental results were used to evaluate the robustness of previously developed models of laminar and turbulent vortex rings. The normalized time, , and normalized axial velocity, , were introduced, where tinit is the time of initial observation of vortex ring-like structures. The time dependence of on was approximated as and for the PFI and G-DI sprays respectively. The G-DI spray compared favourably with the analytical vortex ring model, predicting , in the limit of long times, where α = 3/2 in the laminar case and α = 3/4 when the effects of turbulence are taken into account. The results for the PFI spray do not seem to be compatible with the predictions of the available theoretical models.

Forensic Uncertainty Quantification for Experiments on the Explosively Driven Motion of Particles

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Kyle Hughes ◽  
S. Balachandar ◽  
Nam H. Kim ◽  
Chanyoung Park ◽  
Raphael Haftka ◽  
...  
Keyword(s):  
Uncertainty Quantification ◽  
High Speed ◽  
Early Time ◽  
Operating Conditions ◽  
Quality Data ◽  
High Speed Photography ◽  
Particle Array ◽  
X Ray Imaging ◽  
Drag Models ◽  
Air Force Research Laboratory

Six explosive experiments were performed in October 2014 and February of 2015 at the Munitions Directorate of the Air Force Research Laboratory with the goal of providing validation-quality data for particle drag models in the extreme regime of detonation. Three repeated single particle experiments and three particle array experiments were conducted. The time-varying position of the particles was captured within the explosive products by X-ray imaging. The contact front and shock locations were captured by high-speed photography to provide information on the early time gas behavior. Since these experiments were performed in the past and could not be repeated, we faced an interesting challenge of quantifying and reducing uncertainty through a detailed investigation of the experimental setup and operating conditions. This paper presents the results from these unique experiments, which can serve as benchmark for future modeling, and also our effort to reduce uncertainty, which we dub forensic uncertainty quantification (FUQ).

On the influence of wall distance and geometry for high-pressure n-dodecane spray flames in a constant-volume chamber

2019 ◽  
Vol 21 (2) ◽  
pp. 406-417 ◽  
Author(s):  
Noud Maes ◽  
Mark Hooglugt ◽  
Nico Dam ◽  
Bart Somers ◽  
Gilles Hardy
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Constant Volume ◽  
Operating Conditions ◽  
Orifice Diameter ◽  
Fuel Injector ◽  
Flat Wall ◽  
Wall Distance ◽  
Wall Interaction ◽  
End Wall

To isolate the effect of flame–wall interaction from representative operating conditions of an internal combustion engine, experiments were performed in a constant-volume pre-burn vessel. Three different wall geometries were studied at distances of 32.8, 38.2, and 46.2 mm from a single-hole 0.09-mm orifice diameter fuel injector. A flat wall provides a simplified case of flame–wall interaction. To mimic the division of a jet into two regions by the piston bowl rim in an engine, a two-dimensional confined wall is used. A third, axisymmetric confined wall geometry allows a second simplified comparison to numerical simulations in a Reynolds-averaged Navier–Stokes framework. As a limiting situation for a free jet, the distance from the injector orifice to the end wall of the chamber is 95 mm. Thermocouples installed in the end wall provided insights into local heat losses for reference cases without a wall insert. The test conditions were according to the Engine Combustion Network Spray A guidelines with an ambient temperature of 900 K and an ambient density of 22.8 kg/m3 with 15% O2. Flame structures were studied using high-speed OH* chemiluminescence with integrated single-shot OH PLIF and combined with pressure-based apparent heat release data to infer combustion progress and spray behavior. Soot was studied in a qualitative manner using high-speed natural luminosity imaging with integrated high-speed laser-induced incandescence. Overall, increased mixing upon interaction with the surfaces is observed to increase early heat release rate and to significantly reduce soot, with the nearest wall distance showing most effect. The flat wall gives rise to the most significant effects in all cases.

Studies of Swirl Burner Characteristics, Flame Lengths and Relative Pressure Amplitudes

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
A. Valera-Medina ◽  
N. Syred ◽  
P. Bowen ◽  
A. Crayford
Keyword(s):  
High Speed ◽  
Fossil Fuels ◽  
Fuel Injection ◽  
Flame Length ◽  
Swirl Flow ◽  
High Speed Photography ◽  
Relative Pressure ◽  
Fuel Injector ◽  
Swirl Burner ◽  
Potential Oscillations

Swirl stabilized combustion is a technology which, for stationary combustion, consumes more than 70 to 80% of the world’s fossil fuels. There have been many reviews of this technology, but there are still many gaps in understanding. This paper focuses on the general characteristics of a 100kW swirl burner, originally designed for poor quality fuels, in terms of flame characteristic, length and pressure fluctuations, to give a relative measure of the propensity of the system to respond to outside perturbations. Studied effects include swirl number, symmetry of the swirl flow system, type of fuel injector and mode of fuel injection. A range of techniques, including High Speed Photography (HSP), Particle Image Velocimetry (PIV) and fluctuating pressure measurements were used to create flame maps, flame length detail, and relative pressure amplitudes graphs. The results are discussed in the context of potential oscillations and coupling mechanisms including the effect of the precessing vortex core (PVC), recirculation and shear flow instabilities.

1997 Best Paper Award—Turbomachinery Committee: A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1998 ◽  
Vol 120 (3) ◽  
pp. 393-401 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Short Length ◽  
Operating Conditions ◽  
Length Scale ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms in a low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short length-scale disturbance known as a “spike,” and the second with a longer length-scale disturbance known as a “modal oscillation.” In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented that relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: Long length-scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed that explains the type of stall inception pattern observed in a particular compressor. Measurements from a single-stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1997 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Stability Criteria ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms a in low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short lengthscale disturbance known as a ‘spike’, and the second with a longer lengthscale disturbance known as a ‘modal oscillation’. In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented which relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: long lengthscale disturbances are related to a two-dimensional instability of the whole compression system, while short lengthscale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed which explains the type of stall inception pattern observed in a particular compressor. Measurements from a single stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

Autoignition of Hydrogen / Natural Gas / Nitrogen Fuel Mixtures at Reheat Combustor Operating Conditions

2012 ◽  
Author(s):  
Julia Fleck ◽  
Peter Griebel ◽  
Manfred Aigner ◽  
Adam M. Steinberg
Keyword(s):  
Natural Gas ◽  
High Speed ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Mixing Zone ◽  
Fuel Injector ◽  
Jet Penetration ◽  
Penetration Depths

Previous autoignition studies at conditions relevant to reheat combustor operation have indicated that the presence of relatively small amounts of natural gas (NG) in H2/N2 fuel significantly changes the autoignition behavior. The present study further elucidates the influence of NG on autoignition, kernel propagation, and subsequent flame stabilization at conditions that are relevant for the practical operation of gas turbine reheat combustors (p = 15 bar, Tinlet > 1000 K, hot flue gas, appropriate residence times). The experimental investigation was carried out in a generic, optically accessible reheat combustor. Autoignition events in the mixing zone were recorded by a high-speed camera at frame rates of up to 30,000 fps. This paper describes the autoignition behavior as the H2 volume fraction is increased (decreasing NG) in a H2/NG/N2 fuel mixture for two different jet penetration depths. Additionally, the subsequent flame stabilization phenomena and the structure of the stabilized flame are discussed. The results reveal that autoignition kernels occurred even for the lowest H2 fuel fraction, but they did not initiate a stable flame in the mixing zone. Increasing the H2 volume fraction decreased the distance between the initial position of the autoignition kernels and the fuel injector, finally leading to flame stabilization. The occurrence of autoignition kernels at lower H2 volume fractions (H2/(H2+NG) < 85%) was not found to be significantly influenced by the fluid dynamic and mixing field differences related to the different jet penetration depths. In contrast, autoignition leading to flame stabilization was found to depend on jet penetration; flame stabilization occurred at lower H2 fractions for the higher jet penetration depth (H2/(H2+NG) ≈ 89 compared to H2/(H2+NG) ≈ 95 vol. %).

scholarly journals Simultaneous Pressure Measurement and High-Speed Photography Study of Cavitation in a Dynamically Loaded Journal Bearing

1993 ◽  
Vol 115 (1) ◽  
pp. 88-95 ◽  
Author(s):  
D. C. Sun ◽  
D. E. Brewe ◽  
P. B. Abel
Keyword(s):  
Pressure Measurement ◽  
Cavitation Bubble ◽  
High Speed ◽  
Journal Bearing ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Pressure Data ◽  
Oil Film ◽  
Dynamically Loaded ◽  
Insight Into

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and non-occurrence of cavitation. It was found that (1), cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2), for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

scholarly journals Kinematic Analysis of a Clamp-Type Picking Device for an Automatic Pepper Transplanter

Agriculture ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 627 ◽  
Author(s):  
Md Nafiul Islam ◽  
Md Zafar Iqbal ◽  
Mohammod Ali ◽  
Milon Chowdhury ◽  
Md Shaha Nur Kabir ◽  
...  
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Model Simulation ◽  
Mechanical Damage ◽  
Maximum Velocity ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Virtual Model ◽  
Significant Difference ◽  
Simulation And Validation

Pepper is one of the most vital agricultural products with high economic value, and pepper production needs to satisfy the growing worldwide population by introducing automatic seedling transplantation techniques. Optimal design and dimensioning of picking device components for an automatic pepper transplanter are crucial for efficient and effective seedling transplantation. Therefore, kinematic analysis, virtual model simulation, and validation testing of a prototype were conducted to propose a best-suited dimension for a clamp-type picking device. The proposed picking device mainly consisted of a manipulator with five grippers and a picking stand. To analyze the influence of design variables through kinematic analysis, 250- to 500-mm length combinations were considered to meet the trajectory requirements and suit the picking workspace. Virtual model simulation and high-speed photography tests were conducted to obtain the kinematic characteristics of the picking device. According to the kinematic analysis, a 350-mm picking stand and a 380-mm manipulator were selected within the range of the considered combinations. The maximum velocity and acceleration of the grippers were recorded as 1.1, 2.2 m/s and 1.3, 23.7 m/s2, along the x- and y-axes, respectively, for 30 to 90 rpm operating conditions. A suitable picking device dimension was identified and validated based on the suitability of the picking device working trajectory, velocity, and acceleration of the grippers, and no significant difference (p ≤ 0.05) occurred between the simulation and validation tests. This study indicated that the picking device under development would increase the pepper seedling picking accuracy and motion safety by reducing the operational time, gripper velocity, acceleration, and mechanical damage.

Auto-Ignition of In-Line Injected Hydrogen/Nitrogen Fuel Mixtures at Reheat Combustor Operating Conditions

2015 ◽  
Author(s):  
Christoph Schmalhofer ◽  
Peter Griebel ◽  
Michael Stöhr ◽  
Manfred Aigner ◽  
Torsten Wind
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Fuel Injector ◽  
High Speed Imaging ◽  
Capture Process ◽  
Carrier Medium ◽  
Auto Ignition ◽  
Ignition Limits

De-carbonization of the power generation sector becomes increasingly important in order to achieve the European climate targets. Coal or biomass gasification together with a pre-combustion carbon capture process might be a solution resulting in hydrogen-rich gas turbine (GT) fuels. However, the high reactivity of these fuels poses challenges to the operability of lean premixed gas turbine combustion systems because of a higher auto-ignition and flashback risk. Investigation of these phenomena at GT relevant operating conditions is needed to gain knowledge and to derive design guidelines for a safe and reliable operation. The present investigation focusses on the influence of the fuel injector configuration on auto-ignition and kernel development at reheat combustor relevant operating conditions. Auto-ignition of H2-rich fuels was investigated in the optically accessible mixing section of a generic reheat combustor. Two different geometrical in-line configurations were investigated. In the premixed configuration, the fuel mixture (H2 / N2) and the carrier medium nitrogen (N2) were homogeneously premixed before injection, whereas in the co-flow configuration the fuel (H2 / N2) jet was embedded in a carrier medium (N2 or air) co-flow. High-speed imaging was used to detect auto-ignition and to record the temporal and spatial development of auto-ignition kernels in the mixing section. A high temperature sensitivity of the auto-ignition limits were observed for all configurations investigated. The lowest auto-ignition limits are measured for the premixed in-line injection. Significantly higher auto-ignition limits were determined in the co-flow in-line configuration. The analysis of auto-ignition kernels clearly showed the inhibiting influence of fuel dilution for all configurations.

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