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Wyświetlanie 1-11 z 11
Tytuł:
Thermodynamic Modeling of an Atkinson Cycle with respect to Relative Air-Fuel Ratio, Fuel Mass Flow Rate and Residual Gases
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399496.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
The performance of an air standard Atkinson cycle is analyzed using finite-time thermodynamics. The results show that if the compression ratio is less than a certain value, the power output increases with increasing relative air-fuel ratio, while if the compression ratio exceeds a certain value, the power output first increases and then starts to decrease with increase of relative air-fuel ratio. With a further increase in compression ratio, the increase in relative air-fuel ratio results in decrease of the power output. Throughout the compression ratio range, the power output increases with increase of fuel mass flow rate. The results also show that if the compression ratio is less than a certain value, the power output increases with increase of residual gases, on the contrast, if the compression ratio exceeds a certain value, the power output decreases with increase of residual gases. The results obtained herein can provide guidance for the design of practical Atkinson engines.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 29-34
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Second Law Analysis on an Air-Standard Miller Engine
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1398906.pdf
Data publikacji:
2016-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
Performance analysis has been carried out for air-standard Miller engine using second law analysis. The relations of the second law efficiency versus compression ratio, the second law efficiency versus first law efficiency as well as the exergy versus compression ratio are obtained. The results show that the curve of second law efficiency versus first law efficiency is a parabolic-like one. The results also show that, throughout the compression ratio range, the second law efficiency increases when the expansion-compression ratio increases.
Źródło:
Acta Physica Polonica A; 2016, 129, 6; 1079-1082
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Power Optimization of a Miller Thermal Cycle with respect to Residual Gases and Equivalence Ratio
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399491.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
88.20.td
Opis:
The performance of an air standard Miller cycle is analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio and between the power output and the thermal efficiency are derived by detailed numerical examples. The results show that, throughout the compression ratio range, the power output decreases with increasing residual gases. The results also show that if compression ratio is less than certain value, the power output decreases with increasing equivalence ratio, while if compression ratio exceeds certain value, the power output first increases and then starts to decrease with increasing equivalence ratio. The conclusions of this investigation are of importance when considering the designs of actual Miller engines.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 6-10
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physical Model of the Pulmonary Circulation Designed for Investigation on Cardiac Output Measurement by Means of the Thermodilution Method
Autorzy:
Gawlikowski, M.
Pustelny, T.
Powiązania:
https://bibliotekanauki.pl/articles/1493354.pdf
Data publikacji:
2011-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.19.Hh
47.63.Ec
82.60.Fa
Opis:
The "gold clinical standard" of cardiac output measurements is the thermodilution method, implemented by the Swan-Ganz catheter. The unreliability of obtained results is difficult to estimate experimentally, due to the lack of reference methods or the risk of serious interferences in the measured object. Moreover, the pulsating blood flow produced by the heart is difficult to measure. Therefore it is advisable to develop the physical model of the pulmonary circulation, designed to investigate the accuracy of cardiac output measurements by means of the thermodilution method.
Źródło:
Acta Physica Polonica A; 2011, 120, 4; 798-802
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Analysis of a Dual Cycle Engine with Considerations of Pressure Ratio and Cut-Off Ratio
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1535596.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
The dual cycle is a better approximation to the modern high speed compression ignition engine than either the Diesel cycle or the Otto cycle. Therefore, this study is aimed at investigating the effects of pressure and cut-off ratios on the dual cycle performance with considerations of heat transfer loss, variable specific heat ratio and friction irreversible losses. By using finite-time thermodynamics theory, the relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between power output and the efficiency of the cycle are obtained. The results show that if compression ratio is smaller than certain value, the increase of pressure ratio and the decrease of cut-off ratio make the power output bigger. While if compression ratio exceeds certain value, the power output first increases and then starts to decline as pressure ratio and cut-off ratio are increased. With further increase in compression ratio, the power output decreases with increasing pressure ratio and decreasing cut-off ratio. The effects of pressure and cut-off ratios on the variation of the thermal efficiency with compression ratio are similar to those for the power output. The results obtained in this work can provide significant guidance for the performance evaluation and improvement of modern high speed compression ignition engines.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 534-539
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Analysis of a Diesel Cycle under the Restriction of Maximum Cycle Temperature with Considerations of Heat Loss, Friction, and Variable Specific Heats
Autorzy:
Hou, S.
Lin, J.
Powiązania:
https://bibliotekanauki.pl/articles/1492763.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
The objective of this study is to examine the influences of heat loss characterized by a percentage of fuel's energy, friction and variable specific heats of working fluid on the performance of an air standard Diesel cycle with the restriction of maximum cycle temperature. A more realistic and precise relationship between the fuel's chemical energy and the heat leakage that is constituted on a pair of inequalities is derived through the resulting temperature. The variations in power output and thermal efficiency with compression ratio, and the relations between the power output and the thermal efficiency of the cycle are presented. The results show that the power output as well as the efficiency where maximum power output occurs will increase with the increase of maximum cycle temperature. The temperature-dependent specific heats of working fluid have a significant influence on the performance. The power output and the working range of the cycle increase while the efficiency decreases with increasing specific heats of working fluid. The friction loss has a negative effect on the performance. Therefore, the power output and efficiency of the cycle decrease with increasing friction loss. It is noteworthy that the effects of heat loss characterized by a percentage of fuel's energy, friction and variable specific heats of working fluid on the performance of a Diesel-cycle engine are significant and should be considered in practice cycle analysis. The results obtained in the present study are of importance to provide a good guidance for the performance evaluation and improvement of practical Diesel engines.
Źródło:
Acta Physica Polonica A; 2011, 120, 6; 979-986
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Analysis of DSC Curves for Characterization of Intrinsic Properties of NiTi Shape Memory Alloys
Autorzy:
Ziółkowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1419019.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
81.30.Kf
81.70.Pg
82.60.Fa
62.20.fg
87.85.J-
Opis:
Differential scanning calorimetry is discussed as a tool for characterization of shape memory alloy materials with the example of $Ni_{51at.%}-Ti$ polycrystalline material. Some inconsistencies connected with the differential scanning calorimetry analysis results present in the contemporary literature are indicated, for example large discrepancies in the registered heats of phase transition or differences in registered heats of forward and reverse phase transition, especially in the case of multi-stage phase transition sequences. An attempt is undertaken to explain some of the discrepancies. The overall conclusion from the present work is that forward and reverse sensible heats of phase transition are equal, and discrepancies reported in the literature are artefacts. It is recommended that as a standard practice of differential scanning calorimetry analysis of shape memory alloy materials not only characteristic temperatures but also sensible heat of phase transition should be reported, which can be done at practically no additional cost.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 601-605
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhanced External Counterpulsation in Patients with Advanced Ischemic Cardiomyopathy
Autorzy:
Przywara-Chowaniec, B.
Gawlikowski, M.
Kuczaj, A.
Bachorz, M.
Czechowski, P.
Kowalski, P.
Geodecki, M.
Kawecki, D.
Barańska, K.
Paluch, M.
Pluszczyk, M.
Opara, M.
Puzio, A.
Nowalany-Kozielska, E.
Powiązania:
https://bibliotekanauki.pl/articles/1418031.pdf
Data publikacji:
2012-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.63.Ec
82.60.Fa
Opis:
A significant increase in the number of patients with heart failure of varied etiology has been observed in the recent years. Apart from pharmacological and surgical therapies, new, non-invasive assistance methods of cardiovascular system are still sought. One of them is external counterpulsation. Within this study, effectiveness of such a form of therapy has been examined in a group of 10 patients with an ischemic left ventricular systolic dysfunction. It has been shown that external counterpulsation has a beneficial influence onto the result of a six-minute walk test and causes a slight decrease in the creatinine concentration in the patients undergoing the tests.
Źródło:
Acta Physica Polonica A; 2012, 122, 5; 866-869
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Variable Specific Heat Ratio on Performance οf an Endoreversible Otto Cycle
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1537648.pdf
Data publikacji:
2010-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
Using finite-time thermodynamics, the relations between the work output and the compression ratio, between the thermal efficiency and the compression ratio for an endoreversible Otto cycle are derived with variable specific heat ratio of working fluid. The results show that if compression ratio is less than certain value, the increase of specific heat ratio makes the work output and the thermal efficiency higher; on the contrary, if compression ratio exceeds certain value, the increase of specific heat ratio makes the work output and the thermal efficiency less. The results also show that the maximum work output, the compression ratio at the maximum work output point, the working range of the cycle and the compression ratio at maximum thermal efficiency point decrease as the specific heat ratio increased. The results obtained from this work can be helpful in the thermodynamic modeling and in the evaluation of real Otto engines.
Źródło:
Acta Physica Polonica A; 2010, 117, 6; 887-891
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Equivalence Ratio and Mean Piston Speed on Performance of an Irreversible Dual Cycle
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1493377.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
Opis:
In the present study, the performance of an air standard dual cycle is analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the power output and the thermal efficiency are derived by detailed numerical examples. The results show that the maximum power output and the power output at the maximum efficiency point increase and then decrease as the equivalence ratio and/or the mean piston speed increases. The results also show that the optimal compression ratio corresponding to maximum power output point and the working range of the cycle remain constant as the mean engine speed is increased, but they increase and then decrease as the equivalence ratio is increased. It is noteworthy that the results obtained in the present study are of significance for providing guidance with respect to the performance evaluation of practical internal combustion engines.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 384-389
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Expansion-Compression Ratio on Performance of the Miller cycle
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1418112.pdf
Data publikacji:
2012-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.Ln
82.60.Fa
88.05.-b
88.20.td
Opis:
The objective of this study is to analyze the effect of expansion-compression ratio on the performance of dual cycle. Using finite-time thermodynamics, the relations between thermal efficiency, power output and compression ratio for an air standard Miller cycle have been derived. In the model, the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss computed according to the mean velocity of the piston, and heat transfer loss are considered. The results show that the power output first increases with the increasing expansion-compression ratio and then starts to decrease. Comparisons of the power output of the Miller, Otto, and Atkinson cycles show that if compression ratio is less than certain value, the power output for Otto cycle is higher, while if compression ratio exceeds certain value, the power output for the Miller cycle is higher. With further increase in compression ratio, the power output for Atkinson cycle is higher. In high compression ratio, the power output of the Miller cycle is higher. The results obtained in the present study provide guidance to the performance evaluation and improvement for practical internal combustion engines.
Źródło:
Acta Physica Polonica A; 2012, 122, 4; 645-649
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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