Random Behavior of Kerosene Spray Autoignition in Crossflow

2016 ◽  
Author(s):  
Yongsheng Zhao ◽  
Chi Zhang ◽  
Yuzhen Lin
Keyword(s):  
High Speed ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
High Speed Photography ◽  
Primary Analysis ◽  
Photoelectric Detection ◽  
Random Behavior ◽  
Gauss Distribution ◽  
Autoignition Delay

Based on the flow reactor with rectangle cross-section, this paper studies the spray autoignition characteristics of liquid kerosene injected into air crossflow under high temperature and high pressure conditions. Millisecond-level kerosene injection, millisecond-level photoelectric detection, and high speed photography record experiment techniques are adopted in this research. The operating conditions of this research are as follows: 2.3MPa inlet pressure, 917K inlet temperature, fuel/ air momentum ratio of 52, and Weber number of 355. Photoelectric sensor and photomultiplier equipped with CH filter are used to get the autoignition delay time (ADT). A total of 320 experiments are conducted under the same operating conditions in order to obtain the random ADT probability distribution. The high speed photography is utilized to observe and record the developing process of spray autoignition of kerosene. The results show that the ADT varies from 2.5–5.5millisecond (ms) in the above operating conditions, and confirm the existence of the random behavior of kerosene spray autoignition in the crossflow. These random behaviors of ADT can be correlated well with Gauss distribution. The primary analysis shows that the random behavior stems from the random distributions in the diameter and dispersion due to intrinsic turbulence breakup and transportation which dominate the characteristics of spray autoignition.

Optimisation of CO Turndown for an Axially Staged Gas Turbine Combustor

2020 ◽  
Author(s):  
Jacob E. Rivera ◽  
Robert L. Gordon ◽  
Mohsen Talei ◽  
Gilles Bourque
Keyword(s):  
Residence Time ◽  
Parametric Study ◽  
Gas Turbines ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Independent Effect ◽  
Inlet Temperature ◽  
Operating Characteristics ◽  
Two Stage ◽  
The Impact

Abstract This paper reports on an optimisation study of the CO turndown behaviour of an axially staged combustor, in the context of industrial gas turbines (GT). The aim of this work is to assess the optimally achievable CO turndown behaviour limit given system and operating characteristics, without considering flow-induced behaviours such as mixing quality and flame spatial characteristics. To that end, chemical reactor network modelling is used to investigate the impact of various system and operating conditions on the exhaust CO emissions of each combustion stage, as well as at the combustor exit. Different combustor residence time combinations are explored to determine their contribution to the exhaust CO emissions. The two-stage combustor modelled in this study consists of a primary (Py) and a secondary (Sy) combustion stage, followed by a discharge nozzle (DN), which distributes the exhaust to the turbines. The Py is modelled using a freely propagating flame (FPF), with the exhaust gas extracted downstream of the flame front at a specific location corresponding to a specified residence time (tr). These exhaust gases are then mixed and combusted with fresh gases in the Sy, modelled by a perfectly stirred reactor (PSR) operating within a set tr. These combined gases then flow into the DN, which is modelled by a plug flow reactor (PFR) that cools the gas to varying combustor exit temperatures within a constrained tr. Together, these form a simplified CRN model of a two-stage, dry-low emissions (DLE) combustion system. Using this CRN model, the impact of the tr distribution between the Py, Sy and DN is explored. A parametric study is conducted to determine how inlet pressure (Pin), inlet temperature (Tin), equivalence ratio (ϕ) and Py-Sy fuel split (FS), individually impact indicative CO turndown behaviour. Their coupling throughout engine load is then investigated using a model combustor, and its effect on CO turndown is explored. Thus, this aims to deduce the fundamental, chemically-driven parameters considered to be most important for identifying the optimal CO turndown of GT combustors. In this work, a parametric study and a model combustor study are presented. The parametric study consists of changing a single parameter at a time, to observe the independent effect of this change and determine its contribution to CO turndown behaviour. The model combustor study uses the same CRN, and varies the parameters simultaneously to mimic their change as an engine moves through its steady-state power curve. The latter study thus elucidates the difference in CO turndown behaviour when all operating conditions are coupled, as they are in practical engines. The results of this study aim to demonstrate the parameters that are key for optimising and improving CO turndown.

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).

A Numerical Study of Inlet Geometry for a Low Inertia Mixed Flow Turbocharger Turbine

2014 ◽  
Author(s):  
Thomas M. Leonard ◽  
Stephen Spence ◽  
Juliana Early ◽  
Dietmar Filsinger
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Cone Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Performance ◽  
Blade Angle ◽  
Low Velocity ◽  
Mixed Flow

Mixed flow turbines can offer improvements over typical radial turbines used in automotive turbochargers, with regards to transient performance and low velocity ratio efficiency. Turbine rotor mass dominates the rotating inertia of the turbocharger, and any reductions of mass in the outer radii of the wheel, including the rotor back-disk, can significantly reduce this inertia and improve the acceleration of the assembly. Off-design, low velocity ratio conditions are typified by highly tangential flow at the rotor inlet and a non-zero inlet blade angle is preferred for such operating conditions. This is achievable in a Mixed Flow Turbine without increasing bending stresses within the rotor blade, which is beneficial in high speed and high inlet temperature turbine design. A range of mixed flow turbine rotors was designed with varying cone angle and inlet blade angle and each was assessed at a number of operating points. These rotors were based on an existing radial flow turbine, and both the hub and shroud contours and exducer geometry were maintained. The inertia of each rotor was also considered. The results indicated that there was a trade-off between efficiency and inertia for the rotors and certain designs may be beneficial for the transient performance of downsized, turbocharged engines.

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 Rotordynamics analysis of solar hybrid microturbine for concentrated solar power

2020 ◽  
Vol 11 (1) ◽  
pp. 38
Author(s):  
Maulana Arifin
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Direct Normal Irradiance ◽  
Linear Vibrations ◽  
Parabolic Dish ◽  
Design Speed ◽  
Rotor Assembly ◽  
Tip Displacement

Microturbine based on a parabolic dish solar concentrator runs at high speed and has large amplitudes of subsynchronous turbo-shaft motion due to the direct normal irradiance (DNI) fluctuation in daily operation. A detailed rotordynamics model coupled to a full fluid film radial or journal bearing model needs to be addressed for increasing performance and to ensure safe operating conditions. The present paper delivers predictions of rotor tip displacement in the microturbine rotor assembly supported by a journal bearing under non-linear vibrations. The rotor assembly operates at 72 krpm on the design speed and delivers a 40 kW power output with the turbine inlet temperature is about 950 °C. The turbo-shaft oil temperature range is between 50 °C to 90 °C. The vibrations on the tip radial compressor and turbine were presented and evaluated in the commercial software GT-Suite environment. The microturbine rotors assembly model shows good results in predicting maximum tip displacement at the rotors with respect to the frequency and time domain.

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.

Investigations of Arc Behavior and Particle Formation in the Wire Arc Spray Process Using High Speed Photography

2000 ◽  
Author(s):  
N.A. Hussary ◽  
J. Heberlein
Keyword(s):  
Thermal Spray ◽  
High Speed ◽  
Imaging System ◽  
Metal Droplet ◽  
Droplet Formation ◽  
Operating Conditions ◽  
Arc Spraying ◽  
High Speed Photography ◽  
Spray Process ◽  
The Wire

Abstract The wire arc spraying process, one of several thermal spray processes, gained a sizable part of the thermal spray market, however, more control is needed for this process to be used for high precision coatings. This study is aimed at investigating the liquid metal droplet formation process in order to identify methods for droplet trajectory control. A high speed Kodak imaging system has been used to observe the droplet formation for different operating conditions. Decreasing the upstream pressure and the current levels lead to the reduction in the asymmetric melting of both anode and cathode. By decreasing the interactions of the large eddy structures with the formed metal agglomerates one can achieve better control of the particle trajectories and jet divergence. Thus, coatings can be obtained with higher definition and improved reliability.

Numerical Analysis of Energy Flow Paths in Exhaust Gas Turbochargers by Means of Conjugate Heat Transfer

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Bjoern Hoepke ◽  
Maximilian Vieweg ◽  
Stefan Pischinger
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Conjugate Heat Transfer ◽  
Operating Conditions ◽  
Maximum Speed ◽  
Inlet Temperature ◽  
Special Focus ◽  
Minor Effect ◽  
Exhaust Gas ◽  
Low Speeds

Heat transfer effects play a significant role in assessing the performance of automotive turbochargers. Thermal effects are becoming increasingly relevant due to reduced machine sizes and increased exhaust gas temperatures. In this work, a study of the individual energy flows is conducted by simulation of a complete turbocharger comprising compressor (dC = 51 mm), turbine, and bearing housing using conjugate heat transfer. Special focus is given to the analysis of the various heat flows occurring in the machine aiming to identify the major heat transfer paths and their sensitivity with respect to varying operating conditions. Cooling of the bearing housing is shown to be a powerful thermal isolator mitigating the heat transferred to the compressor by up to 60%. Moreover, the rotating speed largely dictates the amount of heat transfer in the compressor and the direction of the heat flow: Whereas at low speeds (22% of max. speed), 117 W are introduced into the fluid and 338 W are being discharged from the fluid at maximum speed. At high speed operation, the heat transfer is shown to be insignificant compared to the aerodynamic work. At low speeds, however, it can reach up to 35% of the aerodynamic work. While the turbine inlet temperature largely governs the overall heat that is lost from the exhaust gas passing the turbine (from 630 W at 300 °C up to 3.72 kW at 1050 °C), only a minor effect on the compressor heat transfer is detected.

Parametric Effects on Exergetic Efficiency During H2-O2 Combustion Including Singlet Oxygen

2014 ◽  
Author(s):  
DeVon A. Washington ◽  
Howard N. Shapiro
Keyword(s):  
Singlet Oxygen ◽  
Ignition Temperature ◽  
Equivalence Ratio ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Exergy Destruction ◽  
Exergetic Efficiency ◽  
Inlet Concentration ◽  
Optimal Range

Previous work conducted by the authors showed that for a stoichiometric inlet fuel-oxidizer ratio at 1 atm and 1200 K, an optimal range of exergetic efficiency exists for H2 combustion when singlet oxygen composes 0–20% of the oxidizer; with the maximum occurring at approximately 10%. Additionally, in the optimal range, 60% of the total exergy destruction occurs before ignition. These results provide encouraging evidence that it is possible to improve the exergetic efficiency of combustion inherently and thereby reduce fuel usage for a desired energy transfer. The focus of this study is to determine if the exergetic efficiency of combustion can be further optimized by varying other combustion parameters in addition to the inlet concentration of singlet oxygen. The chemical kinetics simulation was accomplished by developing an adiabatic plug flow reactor model in CHEMKIN-PRO® and employing the Moscow State University H2-O2 mechanism. The ranges of parameters considered were: equivalence ratio 0.7–1.3, inlet temperature 1100–1300 K, inlet concentration of singlet oxygen 0–20%, and diluent type (Ar, N2, no dilution). Pressure was held fixed at 1 atm. The calculated quantities were: exergetic efficiency, exergy destruction before ignition, molar conversion of H2, exit temperature, ignition temperature, and ignition distance. Results of the study show that over the optimum range the maximum exergetic efficiency occurs for an equivalence ratio of 1.3, with no dilution at 1300 K. Furthermore, the data show that for 20% inlet singlet oxygen there is significant variability in exergy destruction before ignition, ignition temperature, and ignition distance. Understanding how varying traditional combustion parameters impacts the enhancing effect that singlet oxygen has on the exergetic efficiency of H2 combustion provides a framework for directing future research efforts for hydrocarbon combustion under a broader range of operating conditions of practical engineering interest.

Determination of Void Fraction, Incipient Point of Boiling, and Initial Point of Net Vapor Generation in Sodium-Heated Helically Coiled Steam Generator Tubes

1978 ◽  
Vol 100 (2) ◽  
pp. 268-274 ◽  
Author(s):  
H. C. U¨nal
Keyword(s):  
Heat Flux ◽  
Mass Velocity ◽  
High Speed ◽  
Initial Point ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Centrifugal Forces ◽  
Vapor Generation ◽  
Volumetric Rate ◽  
Rate Ratios

Void fraction was measured with high-speed photography in a 26.7 m and a 40.1 m long, sodium-heated helically coiled steam generator tube of 0.018 m ID. The ratio of coil diameter to tube diameter was 38.9. The operating conditions for the tests were as follows: Pressure: 4–18 MN/m2, mass velocity: 429–1518 kg/m2s, heat flux: 0.013–0.42 MW/m2, outlet subcooling: 0.3–12.5 K, outlet steam quality: 0.000032–0.075. For vapor volumetric rate ratios greater than 0.4, the so-called distribution parameter is not affected by centrifugal forces, and is equal to 0.875. For vapor volumetric rate ratios smaller than 0.4, this parameter is affected by centrifugal forces and the aforesaid ratio. The incipient point of boiling and initial point of net vapor generation were determined with high-speed photography in the aforementioned 26.7 m long helical coil for the following range of operating conditions: Pressure: 4–18 MN/m2, mass velocity 757–1518 kg/m2s, heat flux: 0.082–0.413 MW/m2, outlet subcooling: 4.4–12.5 K. The data were correlated by using both the average and local values of the operating conditions.

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