Methodology to Evaluate the Characteristics of a Twin-Scroll Turbocharger With Various Approaches for the Computation of Thermodynamic Properties

2017 ◽  
Author(s):  
Holger Mai ◽  
André Kaufmann
Keyword(s):  
Thermodynamic Properties ◽  
Test Bench ◽  
Good Practice ◽  
Working Fluid ◽  
Individual Species ◽  
Quality Level ◽  
Humid Air ◽  
Hot Gas ◽  
The Individual ◽  
The Impact

When it comes to evaluating the thermodynamic and fluid dynamic behavior of a turbocharger (TC) and ensuring the best possible matching to the internal combustion engine, a precise measurement of the characteristic maps is required. Measured on a hot-gas test bench under steady-state conditions, the maps of the compressor and turbine give detailed information about the turbocharger performance and provide boundary conditions for simulating the engine processes of a turbocharged engine. At the moment there is no comprehensive standard on how to measure a TC on a test bench. All existing guidelines such as SAE J1826 & J922 and ASME PTC 10 contain more general information with recommendations, but turbocharger mapping on a hot-gas test bench is highly complex and has a large dependence on heat transfer. The characteristics are not determined directly, but have to be computed using the measured quantities and the thermodynamic properties of the working fluid. For that reason, all influences that may occur during the measurement have to be taken into account for the comparability of different turbochargers or the repeatability for the same turbocharger specimen. As a consequence, this paper deals with the methodology of thermodynamic computation for a mono-scroll and a twin-scroll turbocharger in general and the impact of different approaches for computing the thermodynamic properties of the individual species on compressor and turbine efficiencies in particular. For computing the characteristics of a mono-scroll turbocharger, a methodology is used that matches good practice and state-of-the-art technology. For computing the characteristics of a twin-scroll turbocharger, a new methodology is developed to provide a practical approach for the evaluation of pressure ratios and efficiencies of a twin-entry turbine. The use of the closed-loop unit for the extension of the turbine is included. Computing the thermodynamic state changes, power, and efficiencies of the compressor and turbine requires knowledge of the physicochemical properties of the involved fluids. These fluids are humid air (compressor) and exhaust gas (turbine) and depend on the gas composition, pressure, and especially temperature with respect to the relative humidity. Turbocharger efficiencies are very sensitive to deviations in the thermodynamic properties of the individual species. Different forms of polynomials with different levels of complexity and precision are available in literature. In this paper, the most commonly used polynomials for computing the thermodynamic properties such as caloric perfect gas, humid air, VDI 4670, NASA9, CHEMKIN, NIST, and SAE J1826 will be used for the characteristic maps of a twin-scroll turbocharger. The results will be discussed in terms of the impact on turbocharger efficiencies and the relevance to achieving a desired quality level for turbocharger mapping.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part I: Thermodynamics

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
R. M. Kavanagh ◽  
G. T. Parks
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Search Algorithm ◽  
Working Fluid ◽  
Specific Work ◽  
Humid Air ◽  
System Parameters ◽  
Multi Objective ◽  
Air Turbine ◽  
The Impact

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT, and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focuses purely on the thermodynamic performance and the impact of the system parameters on the performance; Part II will study the economic performance. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

Advanced Modeling of Fluid Thermodynamic Properties for Gas Turbine Performance Simulation

2008 ◽  
Author(s):  
Vishal Sethi ◽  
Fulvio Diara ◽  
Sina Atabak ◽  
Anthony Jackson ◽  
Arjun Bala ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Gas Turbine ◽  
Fluid Model ◽  
Simulation Software ◽  
Working Fluid ◽  
Performance Simulation ◽  
Turbine Performance ◽  
Fluid Properties ◽  
Convergence Problems ◽  
The Impact

This paper describes the structure of an advanced fluid thermodynamic model which has been developed for a novel advanced gas turbine simulation environment called PROOSIS. PROOSIS (PRopulsion Object Oriented SImulation Software) is part of the VIVACE-ECP (Value Improvement through a Virtual Aeronautical Collaborative Enterprise - European Cycle Programme) project. The main objective of the paper is to determine a way to achieve an accurate, robust and reliable fluid model. The results obtained demonstrate that accurate modeling of the working fluid is essential to avoid convergence problems of the thermodynamic functions thereby increasing the accuracy of calculated fluid properties. Additionally, the impact of accurately modeling fuel thermodynamic properties, at the point of the injection, is discussed.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part II: Economics

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
R. M. Kavanagh ◽  
G. T. Parks
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Search Algorithm ◽  
Working Fluid ◽  
Specific Work ◽  
Humid Air ◽  
System Parameters ◽  
Multi Objective ◽  
Air Turbine ◽  
The Impact

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focused on the thermodynamic performance and the impact of the system parameters on the performance, Part II studies the economic performance of these cycles. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

Investigation of Gas Properties for Combustion Products of Organic Fuels

2006 ◽  
Author(s):  
SooYong Kim ◽  
Valeri P. Kovalevsky ◽  
Dae-Seung Kim
Keyword(s):  
Thermodynamic Properties ◽  
Combustion Products ◽  
Ideal Gas ◽  
Cycle Performance ◽  
Design Stage ◽  
Working Fluid ◽  
Organic Fuel ◽  
Humid Air ◽  
Gas Combustion ◽  
Gas Properties

In making cycle performance calculation, it is first necessary to establish data relating to the properties of the working fluid of turbo-machinery. Because the composition of natural gas combustion products varies, along with the fuel chemistry, unique formulae for their gas properties do not exist, hence the calculation becomes more complex. Thermodynamic properties depend not only on composition of gases but also on assumptions concerning the change of composition during each process in which temperature, pressure or some other thermodynamic state functions may be shifting. In the present study, a calculation method of gas constants, heat capacity, enthalpy of dry, humid air and combustion products of organic fuel are studied. A theoretical base of thermodynamic properties of gas mixtures constructed on a model of ideal gas is formulated. The composition products are represented by the mixture of ideal gases, humid air and steam directly participating in the burning process and the products of stoichiometric combustion of any organic fuel. The developed calculation procedure is validated through comparison with tabulated data in open literatures and it presented satisfactory results. Recommendation for the application of the suggested method with restriction in relation to range of temperature for static and dynamic calculation is also given. It is supposed that the present method and its result can be used in the preliminary design stage of heat exchangers, high temperature gas turbine units and boilers.

Maximum flood depth characterizes above-ground biomass in African seasonally shallowly flooded grasslands

2007 ◽  
Vol 23 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Paul Scholte
Keyword(s):  
Dry Season ◽  
Perennial Grasses ◽  
Individual Species ◽  
Above Ground Biomass ◽  
Nutrient Quality ◽  
Flood Duration ◽  
Ground Biomass ◽  
Flood Depth ◽  
The Individual ◽  
The Impact

Flood depth has been frequently used to explain the distribution of plant species in seasonally flooded grasslands, but its relation with vegetation production has remained ambiguous. The relationship between flooding and above-ground biomass at the end of the flooding season and during the dry season was studied to assess the impact of reflooding on the Logone floodplain, Cameroon. Above-ground biomass of a combination of all species and of the individual perennial grasses Oryza longistaminata and Echinochloa pyramidalis showed a positive linear relationship with maximum flood depth up to 1 m. The gradient of these relationships became steeper and their fit better during the 2 y following the installation of the flooding, showing the response lag to floodplain rehabilitation. Flood duration only explained the above-ground biomass of the combination of all species and not of the individual species. Above-ground biomass data from other floodplains in the three main African geographic regions showed a similar relationship with maximum flood depth less than 1 m. Dry-season regrowth, important because of its high nutrient quality during forage scarcity, was not directly related to maximum flood depth, possibly because of its dependency on the period of burning and soil moisture. Presented data indicate that a rise of water level of 1 cm corresponds to an increase in above-ground biomass of c. 150 kg DM ha−1.

scholarly journals Microbiome interactions shape host fitness

2018 ◽  
Vol 115 (51) ◽  
pp. E11951-E11960 ◽  
Author(s):  
Alison L. Gould ◽  
Vivian Zhang ◽  
Lisa Lamberti ◽  
Eric W. Jones ◽  
Benjamin Obadia ◽  
...  
Keyword(s):  
Life History ◽  
Bacterial Species ◽  
Gut Bacteria ◽  
Individual Species ◽  
Multiple Traits ◽  
Community Interactions ◽  
Host Fitness ◽  
Core Species ◽  
The Individual ◽  
The Impact

Gut bacteria can affect key aspects of host fitness, such as development, fecundity, and lifespan, while the host, in turn, shapes the gut microbiome. However, it is unclear to what extent individual species versus community interactions within the microbiome are linked to host fitness. Here, we combinatorially dissect the natural microbiome of Drosophila melanogaster and reveal that interactions between bacteria shape host fitness through life history tradeoffs. Empirically, we made germ-free flies colonized with each possible combination of the five core species of fly gut bacteria. We measured the resulting bacterial community abundances and fly fitness traits, including development, reproduction, and lifespan. The fly gut promoted bacterial diversity, which, in turn, accelerated development, reproduction, and aging: Flies that reproduced more died sooner. From these measurements, we calculated the impact of bacterial interactions on fly fitness by adapting the mathematics of genetic epistasis to the microbiome. Development and fecundity converged with higher diversity, suggesting minimal dependence on interactions. However, host lifespan and microbiome abundances were highly dependent on interactions between bacterial species. Higher-order interactions (involving three, four, and five species) occurred in 13–44% of possible cases depending on the trait, with the same interactions affecting multiple traits, a reflection of the life history tradeoff. Overall, we found these interactions were frequently context-dependent and often had the same magnitude as individual species themselves, indicating that the interactions can be as important as the individual species in gut microbiomes.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

Investigating the Relationship Between Self-Esteem and Stigma Among Young Adults With History of Suicide Attempts

Crisis ◽  
2016 ◽  
Vol 37 (4) ◽  
pp. 265-270 ◽  
Author(s):  
Meshan Lehmann ◽  
Matthew R. Hilimire ◽  
Lawrence H. Yang ◽  
Bruce G. Link ◽  
Jordan E. DeVylder
Keyword(s):  
Young Adults ◽  
Suicide Attempts ◽  
Self Esteem ◽  
High Risk Population ◽  
High Functioning ◽  
People With Mental Illness ◽  
History Of ◽  
The Individual ◽  
The Impact ◽  
The Relationship

Abstract. Background: Self-esteem is a major contributor to risk for repeated suicide attempts. Prior research has shown that awareness of stigma is associated with reduced self-esteem among people with mental illness. No prior studies have examined the association between self-esteem and stereotype awareness among individuals with past suicide attempts. Aims: To understand the relationship between stereotype awareness and self-esteem among young adults who have and have not attempted suicide. Method: Computerized surveys were administered to college students (N = 637). Linear regression analyses were used to test associations between self-esteem and stereotype awareness, attempt history, and their interaction. Results: There was a significant stereotype awareness by attempt interaction (β = –.74, p = .006) in the regression analysis. The interaction was explained by a stronger negative association between stereotype awareness and self-esteem among individuals with past suicide attempts (β = –.50, p = .013) compared with those without attempts (β = –.09, p = .037). Conclusion: Stigma is associated with lower self-esteem within this high-functioning sample of young adults with histories of suicide attempts. Alleviating the impact of stigma at the individual (clinical) or community (public health) levels may improve self-esteem among this high-risk population, which could potentially influence subsequent suicide risk.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

The Role of Threat and Economic Uncertainty in Support for Scottish Independence

2014 ◽  
Vol 23 (1) ◽  
pp. 103-124 ◽  
Author(s):  
Daniel Kopasker
Keyword(s):  
Economic Consequences ◽  
Perceived Threat ◽  
Constitutional Change ◽  
Lack Of Information ◽  
Economic Expectations ◽  
Scottish Independence ◽  
The Individual ◽  
The Impact ◽  
Levels Of Support

Existing research has consistently shown that perceptions of the potential economic consequences of Scottish independence are vital to levels of support for constitutional change. This paper attempts to investigate the mechanism by which expectations of the economic consequences of independence are formed. A hypothesised causal micro-level mechanism is tested that relates constitutional preferences to the existing skill investments of the individual. Evidence is presented that larger skill investments are associated with a greater likelihood of perceiving economic threats from independence. Additionally, greater perceived threat results in lower support for independence. The impact of uncertainty on both positive and negative economic expectations is also examined. While uncertainty has little effect on negative expectations, it significantly reduces the likelihood of those with positive expectations supporting independence. Overall, it appears that a general economy-wide threat is most significant, and it is conjectured that this stems a lack of information on macroeconomic governance credentials.

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