18 research outputs found
Experimental procedure for the characterization of turbocharger s waste-gate discharge coefficient
No full text[EN] Nowadays, the turbocharger has become one of the key components for automotive spark-ignition engine
improvements (fed with both liquid and gaseous fuels), as a support for the boosting and downsizing concept to reduce
fuel consumption and exhaust emission. In gasoline engines, the usage of the waste-gate valve typically regulates the
maximum boost pressure in the turbocharger system, to protect the engine and the turbocharger at high engine speeds.
To improve the transient response at low engine speeds two-stage turbocharger is widely used. Two-stage systems are
composed of several valves to regulate the flow to control the boosting of the system. Like, a by-pass valve between the
turbines, a check valve between the compressor and a waste-gate valve for the low-pressure turbines. This paper deals
with a methodology for characterizing the discharge coefficient of an electronic waste-gate valve in the turbocharger. To
estimate the gas flow over the same in one-dimensional models, an empirical model is correlated and validated. For this,
a constant stream experimental work has been carried out on a test rig at different valve position openings, with high
turbine inlet temperatures. Finally, an optimal MAP of discharge coefficient has been drawn out through interpolation
method, which can integrate into the full one-dimensional turbocharged engine model system, to calculate the actual
mass flow through the waste-gate valve.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was partially funded by FEDER and Government of Spain through Project TRA2016-79185-R.Serrano, J.; Arnau Martínez, FJ.; Tiseira ., AO.; Samala, V. (2017). Experimental procedure for the characterization of turbocharger s waste-gate discharge coefficient. Advances in Mechanical Engineering. 9(10):1-9. https://doi.org/10.1177/1687814017728242S1991
A holistic methodology to correct heat transfer and bearing friction losses from hot turbocharger maps in order to obtain adiabatic efficiency of the turbomachinery
No full textThis is the author¿s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting,
and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087419834194[EN] Turbocharger performance maps provided by manufacturers are usually far from the assumption of reproducing the isentropic
performance. The reason being, those maps are usually measured using a hot gas stand. The definition of the
effective turbocharger efficiency maps include the mechanical losses and heat transfer that has occurred during the gas
stand test for the turbine maps and only the heat transfer for the compressor maps. Thus, a turbocharger engine model
that uses these maps provides accurate results only when simulating turbocharger operative conditions similar to those
at which the maps are recorded. However, for some critical situations such as Worldwide harmonized Light vehicles
Test Cycles (WLTC) driving cycle or off-design conditions, it is difficult to ensure this assumption. In this article, an internal
and external heat transfer model combined with mechanical losses model, both previously developed and calibrated, has
been used as an original tool to ascertain a calculation procedure to obtain adiabatic maps from diabatic standard turbocharger
maps. The turbocharger working operative conditions at the time of map measurements and geometrical information
of the turbocharger are necessary to discount both effects precisely. However, the maps from turbocharger manufacturers
do not include all required information. These create additional challenges to develop the procedure to obtain approximated
adiabatic maps making some assumptions based on SAE standards for non-available data. A sensitivity study has been
included in this article to check the validity of the hypothesis proposed by changing the values of parameters which are not
included in the map data. The proposed procedure becomes a valuable tool either for Original Equipment Manufacturers
(OEMs) to parameterize turbocharger performance accurately for benchmarking and turbocharged engine design or to turbocharger
manufacturers to provide much-appreciated information of their performance maps.The author(s) disclosed receipt of the following financial support for the research, authorship and/or publication of this article: This work has been partially
supported by FEDER and the Government of Spain
through Grant No. TRA2016-79185-R.Serrano, J.; Olmeda, P.; Arnau Martínez, FJ.; Samala, V. (2020). A holistic methodology to correct heat transfer and bearing friction losses from hot turbocharger maps in order to obtain adiabatic efficiency of the turbomachinery. International Journal of Engine Research. 21(8):1314-1335. https://doi.org/10.1177/1468087419834194S13141335218Sirakov, B., & Casey, M. (2012). Evaluation of Heat Transfer Effects on Turbocharger Performance. Journal of Turbomachinery, 135(2). doi:10.1115/1.4006608Payri, F., Serrano, J. R., Fajardo, P., Reyes-Belmonte, M. A., & Gozalbo-Belles, R. (2012). A physically based methodology to extrapolate performance maps of radial turbines. Energy Conversion and Management, 55, 149-163. doi:10.1016/j.enconman.2011.11.003Chesse, P., Chalet, D., & Tauzia, X. (2011). Impact of the Heat Transfer on the Performance Calculations of Automotive Turbocharger Compressor. Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 66(5), 791-800. doi:10.2516/ogst/2011129Serrano, J. R., Olmeda, P., Arnau, F. J., Reyes-Belmonte, M. A., & Tartoussi, H. (2015). A study on the internal convection in small turbochargers. Proposal of heat transfer convective coefficients. Applied Thermal Engineering, 89, 587-599. doi:10.1016/j.applthermaleng.2015.06.053Tanda, G., Marelli, S., Marmorato, G., & Capobianco, M. (2017). An experimental investigation of internal heat transfer in an automotive turbocharger compressor. Applied Energy, 193, 531-539. doi:10.1016/j.apenergy.2017.02.053Serrano, J., Olmeda, P., Arnau, F., & Dombrovsky, A. (2014). General Procedure for the Determination of Heat Transfer Properties in Small Automotive Turbochargers. SAE International Journal of Engines, 8(1), 30-41. doi:10.4271/2014-01-2857Payri, F., Olmeda, P., Arnau, F. J., Dombrovsky, A., & Smith, L. (2014). External heat losses in small turbochargers: Model and experiments. Energy, 71, 534-546. doi:10.1016/j.energy.2014.04.096Serrano, J. R., Olmeda, P., Tiseira, A., García-Cuevas, L. M., & Lefebvre, A. (2013). Theoretical and experimental study of mechanical losses in automotive turbochargers. Energy, 55, 888-898. doi:10.1016/j.energy.2013.04.042SAE International. Turbocharger gas stand test code, SAE J1826. Technical Report, Society of Automotive Engineers Inc, Warrendale, PA, 1995.SAE International. Supercharger testing standard, SAE J1723. Technical Report, Society of Automotive Engineers Inc, Warrendale, PA, 1995.Serrano, J. R., Olmeda, P., Páez, A., & Vidal, F. (2010). An experimental procedure to determine heat transfer properties of turbochargers. Measurement Science and Technology, 21(3), 035109. doi:10.1088/0957-0233/21/3/03510
Analyzing User Participation Across Different Answering Ranges in an Online Learning Community
No full textabstract: Online learning communities have changed the way users learn due to the technological affordances web 2.0 has offered. This shift has produced different kinds of learning communities like massive open online courses (MOOCs), learning management systems (LMS) and question and answer based learning communities. Question and answer based communities are an important part of social information seeking. Thousands of users participate in question and answer based communities on the web like Stack Overflow, Yahoo Answers and Wiki Answers. Research in user participation in different online communities identifies a universal phenomenon that a few users are responsible for answering a high percentage of questions and thus promoting the sustenance of a learning community. This principle implies two major categories of user participation, people who ask questions and those who answer questions. In this research, I try to look beyond this traditional view, identify multiple subtler user participation categories. Identification of multiple categories of users helps to provide specific support by treating each of these groups of users separately, in order to maintain the sustenance of the community.
In this thesis, participation behavior of users in an open and learning based question and answer community called OpenStudy has been analyzed. Initially, users were grouped into different categories based on the number of questions they have answered like non participators, sample participators, low, medium and high participators. In further steps, users were compared across several features which reflect temporal, content and question/thread specific dimensions of user participation including those suggestive of learning in OpenStudy.
The goal of this thesis is to analyze user participation in three steps:
a. Inter group participation analysis: compare pre assumed user groups across the participation features extracted from OpenStudy data.
b. Intra group participation analysis: Identify sub groups in each category and examine how participation differs within each group with help of unsupervised learning techniques.
c. With these grouping insights, suggest what interventions might support the categories of users for the benefit of users and community.
This thesis presents new insights into participation because of the broad range of
features extracted and their significance in understanding the behavior of users in this learning community.Dissertation/ThesisMasters Thesis Computer Science 201
Effectiveness of preoperative facial nerve diffusion tensor imaging tractography for preservation of facial nerve function in surgery for large vestibular schwannomas: Results of a prospective randomized study
No full textBackground:
The goal of surgery in case of a large vestibular schwannoma is complete excision of tumor and preservation of facial nerve function. The identification and preservation of facial nerve is very difficult during surgery, particularly in case of large tumors. This prospective randomized study was conducted to find out the effectiveness of preoperative facial nerve diffusion tensor imaging tractography (DTI) to predict location of the nerve and preservation of facial nerve function in surgery for large vestibular schwannomas.
Materials and Methods:
In this prospective randomized study, we recruited 100 patients with a large vestibular schwannoma(> 3cm). After initial scrutiny, 94 patients were randomized based on a computer generated chart. In group I, preoperative DTI was done and the operating surgeon was informed about the position of facial nerve preoperatively. In group II, DTI was not done. The facial nerve preservation rates and clinical outcome at follow up was compared between the two groups.
Results:
Out of 94 patients, there were 47 patients in group I (DTI group) and 47 patients in group II (Non DTI group). In DTI group, 40 patients were left for comparison after the exclusion criteria was applied. Preoperative DTI predicted that the facial nerve position was concordant with its intraoperative position in 39 patients (97.5% concordance). Facial nerve preservation rates were statistically significant in group I (DTI group) (P value = 0.002).
Conclusion:
The study establishes the role of preoperative DTI tractography for better facial nerve preservation in surgery for large vestibular schwannomas (>3 cm)
Letter: Risk Factors for Seizure Worsening After Epilepsy Surgery in Children and Adults: A Population-Based Register Study
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Smart Air Quality Monitoring Using IoT
No full textInternet of things (IoT) is a system of "Smart Devices" used over the internet through the world were it will sense and connect with our environment and involves with humans and it is a user friendly for the users and another system devices. Air pollution is one of the major issue of our generations. The rate of air pollution gradually increases with time by more number of things like increasing in vehicles, increasing in population, urbanization, industrialization which helps up in harmful disease effect on human life by directly effecting health of country exposed to it .Air quality gets decreases when enough amount of toxic gases in the atmosphere like co2,alchol,smoke,nh3,benzen and no2.In order to survey we are deploying IoT based pollution monitoring system Were it will capture all the air quality over an cyber space .existing monitoring system and no sensitivity and need technical analysis. So improvement of monitoring system are requires. To Control the issue of trending system. We propose a pollution monitoring system it will detect the percentage of pollution in our environment it shows the average density of pollution released by vehicles or any industries etc.If the pollution level get cross by average it may cause more danger to our human health
The development and efficacy of a mobile phone application to improve medication adherence for persons with epilepsy in limited resource settings: A preliminary study
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