Application of Adaptive Control to Reduce Cyclic Dispersion Near the Lean Limit in a Small-Scale, Natural Gas Engine

2004 ◽  
Author(s):  
K. Dean Edwards ◽  
Robert M. Wagner
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Large Scale ◽  
Small Scale ◽  
Target Point ◽  
Combustion Dynamics ◽  
Current Cycle ◽  
History Of ◽  
Lean Limit ◽  
Prediction Strategy

Predictive feedback control is applied to achieve reduction in cyclic dispersion in an analytical, lean, spark-ignition model and a two-cylinder, four-stroke, natural gas Kohler Command 25 engine operating at lean conditions. Recent observations of the combustion dynamics are used to define a desired target point for control and to predict future combustion events which may stray from the target point. Fueling perturbations are applied to steer the system back toward the desired behavior. Overall control perturbations are constrained to maintain a constant average fuel-to-air ratio. We present two methods for obtaining the prediction of future combustion events. In the first method, the recent history of cycle heat release is used to construct an adaptive, low-order map which relates the current-cycle heat release to the next-cycle heat release. The second method uses symbolic analysis to determine the relative frequency of successive-cycle combustion events and predict the most probable successor to the current cycle. Results are presented which show a moderate reduction in cycle-to-cycle variation near the lean limit in both the model and the engine. Similarities in behavior have been shown to exist-ignition engines suggesting that a similar prediction strategy could be successfully applied to control cyclic dispersion in large-scale reciprocating engines.

Conclusion

2017 ◽  
Keyword(s):  
National Identity ◽  
Geographical Distribution ◽  
Crucial Role ◽  
Large Scale ◽  
Small Scale ◽  
Modern History ◽  
Late Modernity ◽  
History Of ◽  
Definition Of

This chapter extends the book’s insights about nature, technology, and nation to the larger history of the modern period. While the modern nation loses its grip as a locus of identity and analysis, attempts to understand the operation, disruption, and collapse of continental and global infrastructures continue to mix the natural and the machinic in ways that define them both. Those vulnerabilities emphasize large-scale catastrophe; historiographically, they mask the crucial role of small-scale failures in the experience and culture of late modernity, including its definition of nature. Historical actors turned the uneven geographical distribution of small-scale failures into a marker of distinctive local natures and an element of regional and national identity. Attending to those failures helps not only situate cold-war technologies in the larger modern history of natural and machinic orders; it helps provincialize the superpowers by casting problematic “other” natures as central and primary.

Change

2020 ◽  
pp. 310-338
Author(s):  
Hans-Jörg Schmid
Keyword(s):  
Large Scale ◽  
Language Change ◽  
Small Scale ◽  
Systematic Description ◽  
Change Direction ◽  
History Of

This chapter discusses how the Entrenchment-and-Conventionalization Model explains language change. First, it is emphasized that not only innovation and variation, but also the frequency of repetition can serve as important triggers of change. Conventionalization and entrenchment processes can interact and be influenced by numerous forces in many ways, resulting in various small-scale processes of language change, which can stop, change direction, or even become reversed. This insight serves as a basis for the systematic description of nine basic modules of change which differ in the ways in which they are triggered and controlled by processes and forces. Large-scale pathways of change such as grammaticalization, lexicalization, pragmaticalization, context-induced change, or colloquialization and standardization are all explained by reference to these modules. The system is applied in a case study on the history of do-periphrasis.

scholarly journals The Clearing: Heidegger’s Lichtung and The Big Scrub

2010 ◽  
Vol 16 (1) ◽  
Author(s):  
Rob Garbutt
Keyword(s):  
Large Scale ◽  
North Coast ◽  
Small Scale ◽  
South Wales ◽  
History Of ◽  
A Chain ◽  
Settler Society ◽  
Rural Places ◽  
The Mind ◽  
History Of Migration

Clearings make settlement possible. Whether on a small scale using an axe and other hand implements to make way for a dwelling and a garden, or on a large scale with a chain strung between two D9 bulldozers in preparation for a major agribusiness development, the process of clearing creates spaces for installing something new. This paper uses the idea of (the) clearing, as practice, process, outcome and metaphor, to examine the installation of the locals in a settler society. Using Lismore on the far-north coast of New South Wales, Australia, as a case example, the particular work of clearing that is discussed here is a practice that enables a form of colonisation and settlement that distances itself from its history of migration. This is a history of settler locals who were 'always here', and a colonial form of clearing clears the land and the mind of troubling pasts and of troubling presences. For the locals within a place, then, clearing manages and simplifies a complex set of social and material relations, histories and identities.Using Anthony Appiah's concept the 'space clearing gesture', the paper concludes with a reflection on the space in which the idea of "the clearing" and this paper appears. Do places, in this instance rural places, provide a type of clearing in which certain ideas might appear that may not appear elsewhere? If situatedness matters then the diversity of places where thinking is done is important for our ecology of thought, and in connection with this, perhaps what 'rural cultural studies' does is clear a particular type of space for thinking.

Community Replacement Pathways: What Do Fossil Sequences Reveal About Marine Ecosystem Transitions?

1990 ◽  
Vol 5 ◽  
pp. 262-272
Author(s):  
William Miller
Keyword(s):  
Fossil Record ◽  
Large Scale ◽  
Marine Ecosystem ◽  
Small Scale ◽  
Data Sets ◽  
Mass Extinctions ◽  
Ultimate Cause ◽  
Long Time ◽  
History Of ◽  
Time And Energy

Paleontologists have lavished much time and energy on description and explanation of large-scale patterns in the fossil record (e.g., mass extinctions, histories of monophyletic taxa, deployment of major biogeographic units), while paying comparatively little attention to biologic patterns preserved only in local stratigraphic sequences. Interpretation of the large-scale patterns will always be seen as the chief justification for the science of paleontology, but solving problems framed by long time spans and large areas is rife with tenuous inference and patterns are prone to varied interpretation by different investigators using virtually the same data sets (as in the controversy over ultimate cause of the terminal Cretaceous extinctions). In other words, the large-scale patterns in the history of life are the true philosophical property of paleontology, but there will always be serious problems in attempting to resolve processes that transpired over millions to hundreds-of-millions of years and encompassed vast areas of seafloor or landscape. By contrast, less spectacular and more commonplace changes in local habitats (often related to larger-scale events and cycles) and attendant biologic responses are closer to our direct experience of the living world and should be easier to interpret unequivocally. These small-scale responses are reflected in the fossil record at the scale of local outcrops.

Enhanced dissipation for quasi-geostrophic motion over small-scale topography

2000 ◽  
Vol 407 ◽  
pp. 105-122 ◽  
Author(s):  
JACQUES VANNESTE
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Additional Term ◽  
Equation Of Motion ◽  
Small Scale ◽  
Two Dimensional ◽  
Turbulent Dissipation ◽  
Dissipative Term ◽  
History Of ◽  
Large Scale Flow

The effect of a small-scale topography on large-scale, small-amplitude oceanic motion is analysed using a two-dimensional quasi-geostrophic model that includes free-surface and β effects, Ekman friction and viscous (or turbulent) dissipation. The topography is two-dimensional and periodic; its slope is assumed to be much larger than the ratio of the ocean depth to the Earth's radius. An averaged equation of motion is derived for flows with spatial scales that are much larger than the scale of the topography and either (i) much larger than or (ii) comparable to the radius of deformation. Compared to the standard quasi-geostrophic equation, this averaged equation contains an additional dissipative term that results from the interaction between topography and dissipation. In case (i) this term simply represents an additional Ekman friction, whereas in case (ii) it is given by an integral over the history of the large-scale flow. The properties of the additional term are studied in detail. For case (i) in particular, numerical calculations are employed to analyse the dependence of the additional Ekman friction on the structure of the topography and on the strength of the original dissipation mechanisms.

Flame Area Fluctuation Measurements in Velocity-Forced Premixed Gas Turbine Flames

2015 ◽  
Author(s):  
Alexander J. De Rosa ◽  
Janith Samarasinghe ◽  
Stephen J. Peluso ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Small Scale ◽  
Flame Velocity ◽  
Unstable Combustion

Fluctuations in the heat release rate that occur during unstable combustion in lean premixed gas turbine combustors can be attributed to velocity and equivalence ratio fluctuations. For a fully premixed flame, velocity fluctuations affect the heat release rate primarily by inducing changes in the flame area. In this paper, a technique to analyze changes in flame area using chemiluminescence-based flame images is presented. The technique decomposes the flame area into separate components which characterize the relative contributions of area fluctuations in the large scale structure and the small scale wrinkling of the flame. The fluctuation in the wrinkled area of the flame which forms the flame brush is seen to dominate its response in the majority of cases tested. Analysis of the flame area associated with the large scale structure of the flame resolves convective perturbations that move along the mean flame position. Results are presented that demonstrate the application of this technique to both single-nozzle and multi-nozzle flames.

Social capital in large-scale environmental collaboration: the case of the Platte River Recovery Implementation Program

Water Policy ◽  
2014 ◽  
Vol 17 (3) ◽  
pp. 472-483 ◽  
Author(s):  
Christine Reed ◽  
Anthony Campbell ◽  
Mike George ◽  
Deniz Leuenberger ◽  
John McCarty
Keyword(s):  
Social Capital ◽  
Water Policy ◽  
Large Scale ◽  
Collaborative Governance ◽  
Wildlife Habitat ◽  
Small Scale ◽  
Platte River ◽  
Implementation Program ◽  
Grassroots Initiatives ◽  
History Of

Environmental collaborative governance arrangements have the potential to build social capital, leading to long-term cooperation among parties with a history of conflict over water use, in particular in irrigation, hydropower production and riverine wildlife habitat. Previous research on social capital in the context of collaborative governance has emphasized small-scale grassroots initiatives where actors hold common membership in civic associations. This study explores a large-scale policy level collaborative arrangement as a case of collective action facilitated by elements of social capital, with a special emphasis on the concept of the institution as social capital. The Platte River Recovery Implementation Program is the basis for initial findings that social capital formation and cooperative implementation of innovative approaches to water policy can occur at both the local action and large-scale policy levels of collaboration.

Interference fold patterns of the early Precambrian Rock Groups in the Songshan area, China

1982 ◽  
Vol 119 (5) ◽  
pp. 433-461 ◽  
Author(s):  
Shutian Suo ◽  
Ruqi Liu ◽  
Xingyuan Ma
Keyword(s):  
Large Scale ◽  
North China ◽  
Small Scale ◽  
Deformation History ◽  
North China Platform ◽  
Early Proterozoic ◽  
The North ◽  
Regional Deformation ◽  
History Of ◽  
Insight Into

SummaryThe Songshan area is located in the southern part of the North China platform, which is one of the most completely cratonized tectonic units of China. Its basement has experienced a complex evolutionary history and was eventually consolidated at the end of early Proterozoic time about 1.7 Ga ago.A systematic study has been made of the deformation history of the lower Proterozoic Songshan Group and the Archean Dengfeng Group. At least two widespread episodes of deformation can be recognised in the early Proterozoic Zhongyue tectonic cycle and three in the Archean Songyang cycle. Large scale and small scale interference patterns of the superimposed folding are investigated with the aim of recognizing possible regularities in their occurrence and of gaining an insight into the regional deformation history. Two important aspects of superimposition relationships are illustrated: the control of earlier structures upon later ones and the reform of the former by thelatter; their geometrical regularities are also dealt with respectively.

scholarly journals From hunter-gatherers to nomadic pastoralists: forager bands do not tell the whole story of the evolution of human cooperation

2019 ◽  
Author(s):  
Marius Warg Næss
Keyword(s):  
Large Scale ◽  
Evolution Of Cooperation ◽  
Small Scale ◽  
Hunter Gatherers ◽  
Close Link ◽  
Nomadic Pastoralists ◽  
Fertile Ground ◽  
History Of

The history of humanity is a story of cooperation. Issues pertaining to the origin of human cooperation have, however, been characterized by a forager bias, the assumption being that they have a close link to our evolutionary past. In contrast little effort has been spent on documenting and explaining cooperative herding among nomadic pastoralists. As the Mongolian empire attest to nomadic pastoralists—in contrast to foragers—can form large-scale empires. In combination with the prevalence of small-scale cooperative herding groups, nomadic pastoral societies thus provide a fertile ground for expanding our understanding of the evolution of cooperation. In this paper I aim to extend our understanding of human cooperation through a comparison of the most well-known cooperative herding groups—namely the Mongolian khot ail and the Saami siida—and the most well-studied forager bands, namely the Hadza camp and Ache band.

scholarly journals Numerical Simulation of Interaction between Large-Scale Congestion and Vent during the Natural Gas Explosion in a Kitchen

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Lei Pang ◽  
Mengjie Jin ◽  
Qianran Hu ◽  
Kai Yang
Keyword(s):  
Natural Gas ◽  
Flow Field ◽  
Flame Propagation ◽  
Combustion Rate ◽  
Large Scale ◽  
Small Scale ◽  
Propagation Mode ◽  
Gas Explosion ◽  
Flame Propagation Velocity ◽  
Explosion Process

The influence of large-scale congestion on a confined natural gas explosion in a typical Chinese kitchen was studied using the computational fluid dynamics technology. It was found that opening the explosion venting surface promotes the development of turbulence, flame propagation velocity, and multipeak overpressure in the explosion flow field. Large-scale congestion can significantly strengthen the influence of the explosion venting surface on the flow field; the congestion and the explosion venting surface have a synergistic effect on the explosion flow field. At the moment of gas explosion, the flow fields in each area of the kitchen exhibit different distribution characteristics. A flow field near small-scale congestion is more likely to produce greater turbulence, combustion rate, and flame speed. The obstruction effect of large-scale congestion perpendicular to the flame propagation direction is dominant. The indoor flame propagation speed and overpressure development speed increase and the peak combustion rate and indoor peak overpressure decrease with an increase in obstacle blockage. Increases in the large-scale volume congestion rate and volume blockage in the kitchen induce changes in the indoor flame propagation mode and increase the external explosion overpressure. This paper investigated the correlation behavior between large-scale congestion and vent surface in a typical Chinese civil kitchen during natural gas explosion process and provided important support for understanding the mechanism of congestion on gas explosion process and the distribution of explosion hazards in a kitchen.

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