scholarly journals Simulation based study on improving the transient response quality of turbocharged diesel engines

2017 ◽  
Vol 23 (3) ◽  
pp. 297-309 ◽  
Author(s):  
Rakesh Mishra ◽  
Syed Mohammad Saad
Keyword(s):  
Steady State ◽  
Diesel Engine ◽  
Quality Indicators ◽  
Transient Response ◽  
Operating Conditions ◽  
Compressor Wheel ◽  
Turbocharged Diesel Engine ◽  
Content Type ◽  
Wide Range

Purpose Use of fossil fuels in automotive sector is one of the primary causes of greenhouse emissions. The automotive engines need to perform at their best efficiency point to limit these emissions. Most of the quality indicators in this regard are based on near steady state global operational characteristics for engines without considering local performance. In the present study, extensive numerical simulations have been carried out covering a wide range of steady state and transient operating conditions to quantify interaction of turbocharger with engines through turbo lag phenomena which may cause increased emissions during the load change conditions. Furthermore possible innovations have been explored to minimize turbo lag phenomena. The paper aims to discuss these issues. Design/methodology/approach In this paper quality indicators have been developed to quantify the performance of turbocharged diesel engine under the transient event of rapid change in fueling rate which has been rarely investigated. The rate of fueling is changed from 40 mm3/injection to 52 mm3/injection at 1,000 rpm engine speed which corresponds to normal operating condition. To improve quality of transient response, torque assistance method and reduction of inertia of compressor wheel have been used. Parametric study has been undertaken to analyze the quality indicators such as outlet pressure of the compressor and the compressor speed. The turbo lag is quantified to obtain the close to optimal transient response of turbocharged diesel engine. Findings It has been shown that, with torque assist the transient response of the internal combustion engine is significantly improved. On the other hand, marginal improvement in transient response is observed by the reduction in inertia of the compressor wheel. Research limitations/implications The findings indicate that turbo lag can be minimized by providing torque assistance by active and passive means. Practical implications The developed methods can be used in practice for efficient operation of vehicles. Social implications The work carried out in the paper provides a way to minimize harmful emissions. Originality/value The quality indicators developed provide a quantitative measure of turbo lag phenomena and address the above mentioned problems.

A Comparison between Experimental and Analytical Transient Test Results for a Turbocharged Diesel Engine

1976 ◽  
Vol 190 (1) ◽  
pp. 267-276 ◽  
Author(s):  
D.E. Winterbone ◽  
R.S. Benson ◽  
G.D. Closs ◽  
A.G. Mortimer
Keyword(s):  
Steady State ◽  
Diesel Engine ◽  
Operating Conditions ◽  
Analogue Computer ◽  
Test Results ◽  
Test Bed ◽  
Turbocharged Diesel Engine ◽  
Computer Based ◽  
Computer Controlled ◽  
Good Agreement

SYNOPSIS A computer controlled diesel engine test-bed is described. The system is capable of excursions into regions of very low air-fuel ratio operation without damage to the engine; this enables the engine “steady-state” characteristics to be measured for off-design operating conditions. A computer-based data acquisition system was developed to acquire test-bed results under engine transient operating conditions. An analogue computer model of the engine was constructed using the steady-state characteristics of the engine as obtained from on- and off-design. This model operated in real-time and was suitable for both studies of engine control systems and the testing of control hardware. Results obtained from the test-bed and the model are compared. It is shown that good agreement can be achieved by minor modifications to the model based on steady state results.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

scholarly journals An Adaptive Bitrate Switching Algorithm for Speech Applications in Context of WebRTC

2021 ◽  
Vol 17 (4) ◽  
pp. 1-21
Author(s):  
Mohannad Alahmadi ◽  
Peter Pocta ◽  
Hugh Melvin
Keyword(s):  
Real Time ◽  
Data Exchange ◽  
Quality Of Experience ◽  
End User ◽  
High Quality ◽  
Content Type ◽  
Switching Algorithm ◽  
Wide Range ◽  
The Impact

Web Real-Time Communication (WebRTC) combines a set of standards and technologies to enable high-quality audio, video, and auxiliary data exchange in web browsers and mobile applications. It enables peer-to-peer multimedia sessions over IP networks without the need for additional plugins. The Opus codec, which is deployed as the default audio codec for speech and music streaming in WebRTC, supports a wide range of bitrates. This range of bitrates covers narrowband, wideband, and super-wideband up to fullband bandwidths. Users of IP-based telephony always demand high-quality audio. In addition to users’ expectation, their emotional state, content type, and many other psychological factors; network quality of service; and distortions introduced at the end terminals could determine their quality of experience. To measure the quality experienced by the end user for voice transmission service, the E-model standardized in the ITU-T Rec. G.107 (a narrowband version), ITU-T Rec. G.107.1 (a wideband version), and the most recent ITU-T Rec. G.107.2 extension for the super-wideband E-model can be used. In this work, we present a quality of experience model built on the E-model to measure the impact of coding and packet loss to assess the quality perceived by the end user in WebRTC speech applications. Based on the computed Mean Opinion Score, a real-time adaptive codec parameter switching mechanism is used to switch to the most optimum codec bitrate under the present network conditions. We present the evaluation results to show the effectiveness of the proposed approach when compared with the default codec configuration in WebRTC.

The most common violations of regulatory indicators of the quality of electric energy in electric networks

2021 ◽  
pp. 44-49
Author(s):  
A. G. Soshinov ◽  
T. H. Aisin
Keyword(s):  
Quality Indicators ◽  
Electric Energy ◽  
Electrical Equipment ◽  
Operating Conditions ◽  
Regulatory Requirements ◽  
Electric Networks ◽  
High Quality ◽  
The Asymmetry

Work on ensuring the quality of electric energy in accordance with the requirements of GOST 32144-2013 is currently relevant and requires prompt and high-quality solutions. The article lists the main consumers of electric energy that negatively affect its quality, provides the results of measurements of electric energy quality indicators and the most common violations of regulatory requirements, analyzes the influence of voltage asymmetry on the operating conditions of electrical equipment. The basic formulas for calculating the asymmetry coefficients and ways to reduce the voltage asymmetry are proposed.

The impact of leadership churn on quality management in Australian hospitals

2019 ◽  
Vol 33 (7/8) ◽  
pp. 809-820
Author(s):  
Sandra Leggat ◽  
Cathy Balding
Keyword(s):  
Quality Of Care ◽  
Quality Management ◽  
Quality Indicators ◽  
Health Sector ◽  
Quality System ◽  
Board Members ◽  
Governing Board ◽  
Content Type ◽  
The Impact

Purpose The purpose of this paper is to explore the relationship between frequent turnover (churn) of the chief executive officer (CEO), quality manager and members of the governing board with the management of quality in eight Australian hospitals. Design/methodology/approach A mixed method three-year longitudinal study was conducted using validated quality system scales, quality indicators and focus groups involving over 800 board members, managers and clinical staff. Findings There were unexpected high levels of both governance and management churn over the three years. Churn among CEOs and quality managers was negatively associated with compliance in aspects of the quality system used to plan, monitor and improve quality of care. There was no relationship with the quality of care indicators. Staff identified lack of vision and changing priorities with high levels of churn, which they described as confusing and demotivating. There was no relationship with quality processes or quality indicators detected for churn among governing board members. Practical implications Governing boards must recognise the risks associated with management change and minimise these risks with robust clinical governance processes. Originality/value This research is the first that we are aware of that identifies the impact of frequent leadership turnover in the health sector on quality management.

Numerical simulations of non-stationary distributions of electrochemical potentials in SOFC

2017 ◽  
Vol 34 (6) ◽  
pp. 1956-1988 ◽  
Author(s):  
Mayu Muramatsu ◽  
Keiji Yashiro ◽  
Tatsuya Kawada ◽  
Kenjiro Tarada
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Chemical Potential ◽  
Simulation Method ◽  
Open Circuit ◽  
Operating Conditions ◽  
Stationary Distributions ◽  
Experimental Conditions ◽  
Content Type ◽  
Numerical Examples

Purpose The purpose of this study is to develop a simulation method to calculate non-stationary distributions of the chemical potential of oxygen in a solid oxide fuel cell (SOFC) under operation. Design/methodology/approach The initial-boundary value problem was appropriately formulated and the appropriate boundary conditions were implemented so that the problem of non-stationary behavior of SOFC can be solved in accordance with actual operational and typical experimental conditions. The dependencies of the material properties on the temperature and partial pressure of oxygen were also elaborately introduced to realize actual material responses. The capability of the proposed simulation method was demonstrated under arbitrary operating conditions. Findings The steady state calculated with the open circuit voltage condition was conformable with the analytical solution. In addition, the transient states of the spatial distributions of potentials and currents under the voltage- and current-controlled conditions were successfully differentiated, even though they eventually became the same steady state. Furthermore, the effects of dense materials assumed for interconnects and current collectors were found to not be influential. It is thus safe to conclude that the proposed method enables us to simulate any type of transient simulations regardless of controlling conditions. Practical implications Although only uniaxial models were tested in the numerical examples in this paper, the proposed method is applicable for arbitrary shapes of SOFC cells. Originality/value The value of this paper is that adequate numerical simulations by the proposed method properly captured the electrochemical transient transport phenomena in SOFC under various operational conditions, and that the applicability was confirmed by some numerical examples.

The QEB questionnaire as an instrument to examine opinions on food and nutrition and indicators of the quality of diet

2019 ◽  
Vol 121 (6) ◽  
pp. 1342-1353
Author(s):  
Agata Wawrzyniak ◽  
Agnieszka Elżbieta Woźniak ◽  
Anna Anyzewska ◽  
Małgorzata Kwiatkowska ◽  
Anna Kołłajtis-Dołowy
Keyword(s):  
Quality Indicators ◽  
Diet Quality ◽  
Large Population ◽  
Age Groups ◽  
Further Education ◽  
Eating Behaviours ◽  
Content Type ◽  
Nutrition And Diet ◽  
Food And Nutrition

Purpose The purpose of this paper is to assess the Questionnaire Eating Behaviours (QEB), developed by the Science Committee of Human Nutrition of the Polish Academy of Sciences, as an instrument to examine the opinions on food and nutrition and diet quality indicators in women in various age groups. Design/methodology/approach The study involved 161 healthy Polish women aged 18–92, divided into four age groups to assess the QEB questionnaire, as an instrument to examine the opinions on food and nutrition and diet quality indicators. Findings Women provided statistically significant responses to 40 per cent of the statements in the test. In the case of 60 per cent of responses proper answers increased with the age of the participant. Questionnaire determines that people whose opinions were more compliant with nutritional knowledge more often applied the principles of proper nutrition. Dependencies between the number of points from the test of opinions about food and nutrition and the Prohealthy-Diet-Index (pHDI-8) or the sum of points from the test and the Non-healthy-Diet-Index (nHDI-8) were indicated. People who obtained the higher pHDI-8 and the lower nHDI-8 coefficient better evaluated their diet. Originality/value The QEB questionnaire can be an effective, quick and cheap instrument recommended to examine the association between the opinion about food and nutrition and the quality of diet of people at various ages and useful in determining the directions of further education and improvement in the quality of diet, including its assessment in large population groups.

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.

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