scholarly journals Optimized Piston Motion for an Alpha-Type Stirling Engine

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 700 ◽  
Author(s):  
Robin Masser ◽  
Abdellah Khodja ◽  
Mathias Scheunert ◽  
Karsten Schwalbe ◽  
Andreas Fischer ◽  
...  
Keyword(s):  
Waste Heat ◽  
Stirling Engine ◽  
Piston Motion ◽  
Performance Improvements ◽  
Engine Model ◽  
Wide Range ◽  
The Individual ◽  
Parameter Values ◽  
The Impact ◽  
Alpha Type

The Stirling engine is one of the most promising devices for the recovery of waste heat. Its power output can be optimized by several means, in particular by an optimized piston motion. Here, we investigate its potential performance improvements in the presence of dissipative processes. In order to ensure the possibility of a technical implementation and the simplicity of the optimization, we restrict the possible piston movements to a parametrized class of smooth piston motions. In this theoretical study the engine model is based on endoreversible thermodynamics, which allows us to incorporate non-equilibrium heat and mass transfer as well as the friction of the piston motion. The regenerator of the Stirling engine is modeled as ideal. An investigation of the impact of the individual loss mechanisms on the resulting optimized motion is carried out for a wide range of parameter values. We find that an optimization within our restricted piston motion class leads to a power gain of about 50% on average.

scholarly journals Efficiency Reduction in Stirling Engines Resulting from Sinusoidal Motion

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2887 ◽  
Author(s):  
Salvatore Ranieri ◽  
Gilberto Prado ◽  
Brendan MacDonald
Keyword(s):  
Thermal Efficiency ◽  
Thermal Power ◽  
Heat Sources ◽  
Sinusoidal Motion ◽  
Wide Range ◽  
Stirling Engines ◽  
Isothermal Analysis ◽  
The Impact ◽  
Alpha Type ◽  
The Ideal

Stirling engines have a high potential to produce renewable energy due to their ability to use a wide range of sustainable heat sources, such as concentrated solar thermal power and biomass, and also due to their high theoretical efficiencies. They have not yet achieved widespread use and commercial Stirling engines have had reduced efficiencies compared to their ideal values. In this work we show that a substantial amount of the reduction in efficiency is due to the operation of Stirling engines using sinusoidal motion and quantify this reduction. A discrete model was developed to perform an isothermal analysis of a 100cc alpha-type Stirling engine with a 90 ∘ phase angle offset, to demonstrate the impact of sinusoidal motion on the net work and thermal efficiency in comparison to the ideal cycle. For the specific engine analyzed, the maximum thermal efficiency of the sinusoidal cycle was found to have a limit of 34.4%, which is a reduction of 27.1% from Carnot efficiency. The net work of the sinusoidal cycle was found to be 65.9% of the net work from the ideal cycle. The model was adapted to analyze beta and gamma-type Stirling configurations, and the analysis revealed similar reductions due to sinusoidal motion.

A Simplified Method to Evaluate the Impact of Component Design on Engine Performance

2007 ◽  
Author(s):  
Francesco Montella ◽  
J. P. van Buijtenen
Keyword(s):  
Design Process ◽  
Engine Performance ◽  
Simulation Software ◽  
Fast Method ◽  
Engine Simulation ◽  
Engine Model ◽  
Component Design ◽  
Wide Range ◽  
Engine Component ◽  
The Impact

This paper presents a simplified and fast method to evaluate the impact of a single engine component design on the overall performance. It consists of three steps. In the first step, an engine system model is developed using available data on existing engines. Alongside the cycle reference point, a sweep of operating points within the flight envelop is simulated. The engine model is tuned to match a wide range of conditions. In the second step, the module that contains the engine component of interest is analyzed. Different correlations between the component design and the module efficiency are investigated. In the third step, the deviations in efficiency related to different component configurations are implemented in the engine baseline model. Eventually, the effects on the performances are evaluated. The procedure is demonstrated for the case of a two-spool turbofan. The effects of tip leakage in the low pressure turbine on the overall engine performance are analyzed. In today’s collaborative engine development programs, the OEMs facilitate the design process by using advanced simulation software, in-house available technical correlations and experience. Suppliers of parts have a limited influence on the design of the components they are responsible for. This can be rectified by the proposed methodology and give subcontractors a deeper insight into the design process. It is based on commercially available PC engine simulation tools and provides a general understanding of the relations between component design and engine performance. These relations may also take into account of aspects like production technology and materials in component optimization.

scholarly journals Earth-based observations of impact phenomena

1996 ◽  
Vol 156 ◽  
pp. 81-109
Author(s):  
Philip D. Nicholson
Keyword(s):  
Hubble Space Telescope ◽  
Common Pattern ◽  
Mid Infrared ◽  
Wide Range ◽  
Impact Phenomena ◽  
Infrared Wavelengths ◽  
Positive Correlations ◽  
The Individual ◽  
The Impact ◽  
Size Estimates

Earth-based observations at near- and mid-infrared wavelengths were obtained for at least 15 of the SL9 impacts, ranging from the spectacular G, K and L events to the barely-detected N and V impacts. Although there were a few exceptions, most of the IR lightcurves fit a common pattern of one or two relatively faint precursor flashes, followed several minutes later by the main infrared event as the explosively-ejected plume crashed down onto the jovian atmosphere. Correlations with the impact times recorded by the Galileo spacecraft and plumes imaged by the Hubble Space Telescope lead to an interpretation of the twin precursors in terms of (i) the entry of the bolide into the upper atmosphere, and (ii) the re-appearance of the rising fireball above Jupiter's limb. Positive correlations are observed between the peak IR flux observed during the splashback phase and both pre-impact size estimates for the individual SL9 fragments and the scale of the resulting ejecta deposits. None of the fragments observed to have moved off the main train of the comet by May 1994 produced a significant impact signature. Earth-based fireball temperature estimates are on the order of 750 K, 30-60 sec after impact. For the larger impacts, the unexpectedly protracted fireball emission at 2.3 μm remains unexplained. A wide range of temperatures has been inferred for the splashback phase, where shocks are expected to have heated the re-entering plume material at least briefly to several thousand K, and further modelling is required to reconcile these data.

On Compressor Station Layout

2003 ◽  
Author(s):  
Rainer Kurz ◽  
Sebouh Ohanian ◽  
Matt Lubomirsky
Keyword(s):  
Gas Turbine ◽  
Electric Motor ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
General Context ◽  
Operational Flexibility ◽  
Gas Engine ◽  
Wide Range ◽  
The Individual ◽  
The Impact

This paper discusses issues that influence the decision on the arrangement of compressors and the type of equipment in gas pipeline compressor stations. Different concepts such as multiple small units versus single large units are considered, both regarding their impact on the individual station and the overall pipeline. The necessity of standby units is discussed. Various concepts for drivers (gas turbine, gas motor and electric motor) and compressors (centrifugal and reciprocating) are analyzed. The importance of considering all possible operating conditions is stressed. With the wide range of possible operating conditions for the pipeline in mind, the discussion will be brought into the general context of operational flexibility, availability, reliability, installation issues, remote control, and operability of gas turbine driven centrifugal compressors compared to other solutions such as electric motor driven compressors or gas engine driven reciprocating compressors. The impact of different concepts on emissions and fuel cost is discussed. Among the assumptions in this paper are the performance characteristics of the compressor. It will be outlined how these performance characteristics influence the conclusions.

scholarly journals PLAYBACK-THEATRE IN THE SYSTEM OF SOCIALIZATION AND RE-SOCIALIZATION OF PERSONALITY

2018 ◽  
pp. 17-20
Author(s):  
M. Dergach
Keyword(s):  
Psychological Adaptation ◽  
Psychological Support ◽  
Psychological Climate ◽  
Psychological State ◽  
Wide Range ◽  
Important Means ◽  
The Common ◽  
Main Thing ◽  
The Individual ◽  
The Impact

The article reveals the peculiarities of playback theater as a psychodramatic technique, analyzes the current practice of using playback theater in the system of socialization and re-socialization. The author found that socialization, as a necessary process for interaction with the outside world, is manifested in the assimilation and appropriation of social experience for the purpose of productive functioning in it and to construct an image of the common and own world (as a part of the common), which allows a person to live a life while preserving individuality. and creatively influence the world. Within this provision, playback theater should be regarded as a technology of the paratheater system of dramatherapy, which is relevant at any stage of the socialization of the individual or as a means in the mechanisms of socialization. Playback theater contributes to the development of tolerance for social differences, the acceptance of another with all its features, values. Thanks to him, we learn to listen to understand others, because in the performance the main thing is the story of the viewer, the realization of which is impossible in reality without careful perception. The author has found that playback theater as a paratheater system of drama is a rather interesting and important means of socialization and re-socialization of the personality, it can be used in any group of people to solve problems of a wide range. The article describes in detail the content of the playback theater application, namely: social integration of individual subgroups into society; social and psychological adaptation of personality; social-psychological and therapeutic support for people who are in emotional and psychological state; creation of a more favorable social and psychological climate for the team; social and psychological support in complex events; development of personal qualities of children in educational institutions; social and psychological support of people in recreational activities; playback theater as a means of creating space for social networking. Prospects for further research on the topic of the article are to study the attitude of the audience to the performances of the playback theater, the search for the means of expression of the actors, the impact of playback on the children's audience.

scholarly journals Power-Optimized Sinusoidal Piston Motion and Its Performance Gain for an Alpha-Type Stirling Engine with Limited Regeneration

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4564 ◽  
Author(s):  
Mathias Scheunert ◽  
Robin Masser ◽  
Abdellah Khodja ◽  
Raphael Paul ◽  
Karsten Schwalbe ◽  
...  
Keyword(s):  
Power Output ◽  
Waste Heat ◽  
Primary Energy ◽  
Primary Energy Consumption ◽  
Performance Gain ◽  
Piston Motion ◽  
Stirling Engines ◽  
Remarkable Result ◽  
Performance Gains ◽  
Alpha Type

The recuperation of otherwise lost waste heat provides a formidable way to decrease the primary energy consumption of many technical systems. A possible route to achieve that goal is through the use of Stirling engines, which have shown to be reliable and efficient devices. One can increase their performance by optimizing the piston motion. Here, it is investigated to which extent the cycle averaged power output can be increased by using a special class of adjustable sinusoidal motions (the AS class). In particular the influence of the regeneration effectiveness on the piston motion is examined. It turns out that with the optimized piston motion one can achieve performance gains for the power output of up to 50% depending on the loss mechanisms involved. A remarkable result is that the power output does not depend strongly on the limitations of the regenerator, in fact—depending on the loss terms—the influence of the regenerator practically vanishes.

Factors Contributing to the Occurrence of Leptospirosis, and the Impact on Public Health in Saint Lucia 2008-2019

2020 ◽  
Vol 8 (4) ◽  
pp. 69-78
Author(s):  
Edward L. Emmanuel
Keyword(s):  
Public Health ◽  
Secondary Data ◽  
Educational Programme ◽  
Easy Access ◽  
Bacterial Disease ◽  
Mortality And Morbidity ◽  
Wide Range ◽  
Saint Lucia ◽  
The Individual ◽  
The Impact

Leptospirosis is a bacterial disease that affects humans and animals. The causative agent is a spirochete of the genus Leptospira. In humans, it causes a wide range of symptoms, however, asymptomatic presentation is not uncommon. Without proper treatment, leptospirosis can lead to kidney damage, meningitis, liver failure, and respiratory distress. Death may occur in some patients. The aim of the study is to identify the factors contributing to the occurrence of leptospirosis, and the impact on public health in Saint Lucia 2008-2019. The study design is a mixed – method, comprising quantitative and qualitative data. A stratified sampling design using probability proportionate to size sampling at the settlement level was used. Secondary data on the incidence of leptospirosis were obtained from the Ministry of Health, and rainfall data were obtained from the Meteorology Office. Analysis of the data reveals several factors contributing to the occurrence of leptospirosis in Saint Lucia: poor garbage disposal; a large rodent population with easy access to garbage; and a lack of knowledge of leptospirosis. The impact on public health is manifested in the mortality and morbidity of individuals primarily men, and the health, social, and economic impact on the country. Reducing the impact of leptospirosis on the individual and country necessitates an island wide multi - sectoral control and prevention educational programme; an evaluation of the collection, storage, and disposal of household garbage; and the enforcement of legislation governing the proper collection, storage and disposal of garbage.

Impact of subjective modeling decisions on hydrological modeling

2021 ◽  
Author(s):  
Ashlin Ann Alexander ◽  
Dasika Nagesh Kumar
Keyword(s):  
Hydrological Modeling ◽  
Systematic Evaluation ◽  
Suitable Model ◽  
Model Simulations ◽  
Model Configuration ◽  
Wide Range ◽  
Model Components ◽  
Parameter Values ◽  
The Impact ◽  
Subjective Modeling

<p>Modelers often make different decisions in building hydrologic models based on their experience and modeling philosophy. Consequently, a wide range of models is developed, which differ in many aspects of conceptualization and implementation. This diversity of models has been useful to explore a myriad of scientific and applied questions, but it has also led to great confusion on choosing the appropriate model configurations in compliance with the dominant processes in the study area. Also, modeling decisions during model configuration introduce subjectivity from the modeler. To provide guidance to select the best-suited model configuration for a catchment it is required to examine and evaluate the different model representations of hydrological processes and their impact on model simulations. In this study, we show that modeling decisions during the model configuration, beyond the model choice, also impact the model results. The framework, Structure for Unifying Multiple Modeling Alternatives (SUMMA; Clark et al., 2015a, b) is used in this study to disentangle the model components which helps to have a controlled and systematic evaluation of multiple models representations. The area chosen for the study is the Malaprabha catchment in the Karnataka state of India. The impact of the choice of parameterizations and parameter values on the model simulations are shown. To improve upon the traditional model evaluation methods, hydrological signatures are made use to have a hydrologically meaningful evaluation of model simulations. This study helped to identify the suitable model configuration for the Malaprabha catchment. Multiple working hypotheses during model configuration which is possible with the help of such flexible framework like SUMMA can provide insights on the impact of subjective modeling decisions.</p>

scholarly journals Estimating gene flow in island populations

1996 ◽  
Vol 67 (2) ◽  
pp. 147-158 ◽  
Author(s):  
Bruce Rannala ◽  
J. A. Hartigan
Keyword(s):  
Gene Flow ◽  
Island Model ◽  
Least Mean Square ◽  
Island Populations ◽  
Wide Range ◽  
Continuous Generation ◽  
Subdivided Populations ◽  
The Individual ◽  
Pseudo Maximum Likelihood ◽  
Parameter Values

SummaryA new method is presented for estimating the rate of gene flow into island populations using the distribution of alleles in samples from a number of islands. The pseudo maximum likelihood estimator (PMLE) that we derive may be applied to species with either discrete or continuous generation times. For Wright's discrete-generation island model, the method provides an estimate of θ = 2Nm where N is the (haploid) population size on each island and m is the fraction of individuals replaced by immigrants in each generation. For a continuous-generation island model, the corresponding parameter φ is the ratio of the immigration rate φ to the individual birth rate λ. Monte Carlo simulations are used to compare the statistical properties of the PMLE with those of two alternative estimatorsof θ derived from Wright's F-statistics. The PMLE is shown to have greatest efficiency (least mean square error) in most cases for a wide range of sample sizes and parameter values. The PMLE is applied to estimate θ using mtDNA haplotypes and allozymes for subdivided populations of African elephants and Channel Island foxes.

A Comparison of a Mono, Twin and Double Scroll Turbine for Automotive Applications

2015 ◽  
Author(s):  
Jason Walkingshaw ◽  
Georgios Iosifidis ◽  
Tobias Scheuermann ◽  
Dietmar Filsinger ◽  
Nobuyuki Ikeya
Keyword(s):  
Mass Flow ◽  
Flow Characteristics ◽  
High Mass ◽  
Flow Rates ◽  
Engine Simulation ◽  
Engine Model ◽  
Trade Offs ◽  
Mass Flow Rates ◽  
The Individual ◽  
The Impact

As a means of meeting ever increasing emissions and fuel economy demands car manufacturers are using aggressive engine downsizing. To maintain the power output of the engine turbocharging is typically used. Due to the miss-match of the mass flow characteristics of the engine to the turbocharger, at low engine mass flow rates, the turbocharger can suffer from slow response known as “Turbolag”. Mono-scroll turbines are capable of providing good performance at high mass flow rates and in conjunction with low inertia mixed flow turbines can offer some benefits for transient engine response. With a multi-entry system the individual volute sizing can be matched to the single mass flow pulse from the engine cylinders. The exhaust pulse energy can be better utilised by the turbocharger turbine improving turbocharger response, while the interaction of the engine exhaust pulses can be better avoided, improving the scavenging of the engine. The behaviour of a mono-scroll turbocharger with the engine using engine simulation tools has been well established. What requires further investigation is the comparison with multi-entry turbines. CFD (Computational Fluid Dynamics) has been used to examine the single admission behaviour of a twin and double scroll turbine. Turbocharger gas stand maps of the multi-entry turbines have been measured at full and single admission. This data has been used in a 0D engine model. In addition, the turbine stage has been tested on the engine and a validation of the engine model against the engine test data is presented. Using the validated engine model a comparison has been made to understand the differences in the sizing requirements of the turbine and the interaction of the mono-scroll and multi-entry turbines with the engine. The impact of the different efficiency and mass flow rate trends of the mono and multi-entry turbochargers are discussed and the trade-offs between the design configurations regarding on engine behaviour are investigated.

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