Assessment of engine combustion network recommendations for measurement of ignition and lift-off length

2020 ◽  
pp. 146808742092264
Author(s):  
Boni F Yraguen ◽  
Farzad Poursadegh ◽  
Caroline L Genzale
Keyword(s):  
Ignition Delay ◽  
High Speed ◽  
Operating Conditions ◽  
Bias Error ◽  
Ambient Conditions ◽  
Intensity Histogram ◽  
Wide Range ◽  
Engine Combustion ◽  
Length Measurements ◽  
Lift Off

The engine combustion network recommends two different imaging-based diagnostics for the measurement of diesel spray ignition delay and lift-off length, respectively. To measure ignition delay, high-speed imaging of broadband luminosity, spectrally filtered to limit collected wavelengths below 600 nm, is recommended. This diagnostic is often referred to as broadband natural luminosity. For lift-off length measurements, the engine combustion network recommends imaging of OH* chemiluminescence. This diagnostic requires using an image-intensified camera to detect narrowly filtered light around 310 nm. Alternatively, it has been shown that the lift-off length can be measured using broadband natural luminosity, avoiding the need for an intensifier and ultraviolet-transmitting optics. However, care is needed in the collection and processing of this diagnostic to accurately isolate the chemiluminescence signal. Particularly, standard intensity thresholding techniques are not sufficient for isolating the chemiluminescence signal in broadband natural luminosity images. Thus, an intensity-histogram-based thresholding method is introduced. This article assesses the feasibility and practicality of measuring lift-off length using broadband natural luminosity using a detailed comparison to OH* chemiluminescence measurements. It is shown that lift-off length measurements using broadband natural luminosity are prone to user bias error in the optical setup and data processing, especially under moderate- to high-sooting conditions. We conclude that while OH* imaging provides the most reliable and accurate measurement of lift-off length at a wide range of ambient conditions, an intensity-histogram analysis can help discriminate the high-temperature chemiluminescence signal from others in a broadband natural luminosity image at higher-sooting operating conditions than demonstrated in current literature.

Characteristics of air entrainment during dynamic wetting failure along a planar substrate

2014 ◽  
Vol 747 ◽  
pp. 119-140 ◽  
Author(s):  
E. Vandre ◽  
M. S. Carvalho ◽  
S. Kumar
Keyword(s):  
High Speed ◽  
Water Solution ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Operating Conditions ◽  
Dynamic Wetting ◽  
Glycerol Water ◽  
Planar Substrate ◽  
Wide Range ◽  
Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Ambient Condition Effects on NOx and CO Emissions From Process Heaters

2008 ◽  
Author(s):  
Wesley R. Bussman ◽  
Charles E. Baukal
Keyword(s):  
Atmospheric Pressure ◽  
Ambient Air ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Ambient Conditions ◽  
Fuel Gas ◽  
Natural Draft ◽  
Actual Operating ◽  
Wide Range ◽  
Pollution Emissions

Because process heaters are typically located outside, their operation is subject to the weather. Heaters are typically tuned at a given set of conditions; however, the actual operating conditions may vary dramatically from season to season and sometimes even within a given day. Wind, ambient air temperature, ambient air humidity, and atmospheric pressure can all significantly impact the O2 level, which impacts both the thermal efficiency and the pollution emissions from a process heater. Unfortunately, most natural draft process burners are manually controlled on an infrequent basis. This paper shows how changing ambient conditions can considerably impact both CO and NOx emissions if proper adjustments are not made as the ambient conditions change. Data will be presented for a wide range of operating conditions to show how much the CO and NOx emissions can be affected by changes in the ambient conditions for fuel gas fired natural draft process heaters, which are the most common type used in the hydrocarbon and petrochemical industries. Some type of automated burner control, which is virtually non-existent today in this application, is recommended to adjust for the variations in ambient conditions.

scholarly journals Cyclic NO2:NOx ratio from a diesel engine undergoing transient load steps

2019 ◽  
Vol 22 (1) ◽  
pp. 284-294 ◽  
Author(s):  
FCP Leach ◽  
MH Davy ◽  
MS Peckham
Keyword(s):  
Diesel Engine ◽  
High Speed ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Formation Mechanisms ◽  
Exhaust Gas ◽  
Work Cycle ◽  
Wide Range ◽  
Gas Recirculation ◽  
Aftertreatment Systems

As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO2/NOx ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NOx aftertreatment systems. In this work, cycle-to-cycle NO and NOx emissions have been measured using a Cambustion CLD500, and the cyclic NO2/NOx ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NOx, and hence NO2/NOx ratio, are instantaneous upon a step change in engine load. NO2/NOx ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO2 than have been previously reported in the literature are observed.

Design relations for predicting surface-ice clearing capacity of open channels

2000 ◽  
Vol 27 (6) ◽  
pp. 1230-1239 ◽  
Author(s):  
I Morin ◽  
R D Townsend ◽  
B Morse
Keyword(s):  
Environmental Parameters ◽  
Operating Conditions ◽  
Water Current ◽  
Ambient Conditions ◽  
Navigation Channel ◽  
Wide Range ◽  
Ice Concentration ◽  
Wind Characteristics ◽  
Surface Ice ◽  
The Impact

Numerical simulations are performed to evaluate the impact of various hydraulic and environmental parameters on the ice clearing capacity of a Lac St-Pierre navigation channel. The Lagrangian particle-dynamics (Pdyn) model is used to simulate a wide range of "operating" conditions that are representative of conditions observed on Lac St-Pierre. Simple relationships are developed that express both ice velocity and flux as functions of the geometry of the channel (width and plan-form shape) and ambient conditions (ice concentration, thickness, water current, wind magnitude and direction). These relationships reflect the importance of wind characteristics and areal ice concentration in regard to predicting both surface ice velocities and flux.Key words: ice clearing, channel geometry, ambient conditions.

Integrated Dynamic Thermo-Mechanical Modeling of High Speed Spindles, Part 2: Solution Procedure and Validations

2004 ◽  
Vol 126 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Hongqi Li ◽  
Yung C. Shin
Keyword(s):  
High Speed ◽  
Solution Procedure ◽  
Operating Conditions ◽  
Test Results ◽  
Mechanical Modeling ◽  
Spindle Bearing ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Models Validation ◽  
Validation Tests

This paper presents a new solution procedure for an integrated thermo-dynamic spindle model and validation results. Based on the model presented in Part 1 of this paper, a computer program has been developed to generate comprehensive solutions for high speed spindle-bearing systems, such as bearing stiffness, contact load and temperature, spindle dynamic characteristics and response, temperature distributions, and thermal expansions. The model and the solution procedure are modular such that solutions for different spindle set-ups can be easily generated by combining a given spindle model with different toolholder models. Validation test results for thermal and dynamic predictions are presented for four different spindle systems, including the thermal and dynamic validation tests on a specially constructed spindle testbed. The validation results show the model has accurate predictive capabilities for a wide range of operating conditions and various spindle designs.

Compression Technology Selection for Downhole Application in Gas Wells

2019 ◽  
Author(s):  
Ameen Malkawi ◽  
Ahmed AlAdawy ◽  
Rajesh Kumar V. Gadamsetty ◽  
Rafael Lastra Melo
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Gas Flow ◽  
Optimal Solution ◽  
Operating Conditions ◽  
Technology Selection ◽  
Well Performance ◽  
Ambient Conditions ◽  
Gas Wells ◽  
Selection For

Abstract Downhole gas compression technology is an artificial lift method that aims to boost production, maximize recovery and delay onset of liquid loading in gas wells. There are different available compression technologies that can be considered for downhole applications, such as screw, scroll, centrifugal and axial compressors. Selection of the appropriate type mainly depends on expected well performance, ambient conditions, compressor operating envelope, technology characteristics, limitations and size constraints. The objective of this study is to perform a feasibility evaluation of compression solutions applicable for a given set of candidate gas wells. Aerodynamic and hydraulic models are used to determine operating conditions, compressor performance, and to select equipment specifications such as impeller diameter, compressor envelope, shaft HP requirement and number of stages among other parameters. A Pugh analysis is performed for all compression technologies and their characteristics to down-select the most suitable solutions for the given set of wells. The results of the analysis indicated an optimal downhole compression technology that covers most of the gas flow rate requirements and meet the performance expectations. The study also provided critical specifications for the compressor, including high-speed operation needed to provide the required flow rates and compression ratio for a relatively small housing diameter. The study also finds that other technologies may be applicable but only to certain population of wells, as the flow rate spectrum is narrower than the optimal solution at the studied conditions. The analysis for the discarded compression technologies in this study showed relatively significant disadvantages for downhole application when compared to the selected compressor. This study presents a holistic analysis for compression technology selection for gas wells that, as per to the understanding of the authors, is unique in the existing literature of gas well applications.

Influence of Stator Blade Geometry on Torque Converter Cavitation

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Cheng Liu ◽  
Wei Wei ◽  
Qingdong Yan ◽  
Brian K. Weaver ◽  
Houston G. Wood
Keyword(s):  
High Speed ◽  
Torque Converter ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Speed Ratio ◽  
Capacity Loss ◽  
Wide Range ◽  
Stator Blade ◽  
Torque Converters ◽  
Blade Geometry

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.

Evaluation of a Cyclone-Based Particulate Filtration System for High-Speed Diesel Engines

1994 ◽  
Vol 208 (4) ◽  
pp. 269-279 ◽  
Author(s):  
C Arcoumanis ◽  
L N Barbaris ◽  
R I Crane ◽  
P Wisby
Keyword(s):  
Diesel Engines ◽  
High Speed ◽  
Direct Injection ◽  
Operating Conditions ◽  
Exhaust Pipe ◽  
Filtration System ◽  
High Speed Diesel ◽  
Wide Range ◽  
Mass Flowrate ◽  
Particulate Filtration

A cyclone-based filtration system has been developed and its potential for reduction of exhaust particulates in high-speed direct injection diesel engines is evaluated; the filtration efficiency of the four cyclones has been enhanced by means of particulate agglomeration induced by cooling in a heat exchanger. With this system installed in the exhaust pipe of a 2.5 litre direct injection engine, tests covering a wide range of speed, load and exhaust gas recirculation (EGR) fraction resulted in reductions of up to 77 per cent in emitted particulate mass flowrate. The dependence of the system's performance on engine operating conditions, EGR configuration and cyclone geometry is presented and discussed.

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