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Wyświetlanie 1-10 z 14
Tytuł:
Effect of Volume Ratio of Heat Rejection Process on Performance of an Atkinson Cycle
Autorzy:
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1030546.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
Atkinson cycle
heat rejection process
Opis:
The objective of this study is to analyze the effect of volume ratio of heat rejection process on the performance of dual cycle. Using finite-time thermodynamics, the relations between the volume ratio of heat rejection, the thermal efficiency, the power output, the heat transfer losses, the friction power and the compression ratio for an air standard Atkinson cycle have been derived. In the model, the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss and heat leakage loss are considered. The results show that the power output and the thermal efficiency first increase with the increase of volume ratio of heat rejection process and then start to decrease. The optimum value of the volume ratio of heat rejection which maximizes the power output is higher than that which maximizes the thermal efficiency, while the optimum value of the compression ratio which maximizes the power output is lower than that which maximizes the thermal efficiency. 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; 2018, 133, 1; 201-205
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
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:
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:
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:
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:
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:
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:
Efficiency of CaCl2 spray at different fruit development stages on the fruit mineral nutrient accumulation in cv. Hayward kiwifruit
Autorzy:
Shiri, M.A.
Ghasemnezhad, M.
Moghadam, J.F.
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1188065.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie / Polskie Towarzystwo Magnezologiczne im. Prof. Juliana Aleksandrowicza
Tematy:
Actinidia deliciosa
fruit
development stage
mineral nutrient
nutrient accumulation
Hayward cultivar
kiwi fruit
calcium absorption
calcium chloride spray
Opis:
Despite the importance of calcium in many fruit species and the effects of calcium application, there is little or no reliable information on the effect of CaCl2 spray at different fruit development stages on the fruit mineral nutrient content during the growing season and at harvest. Therefore, this study has been conducted to evaluate the effect of calcium chloride (CaCl2, 15 g L-1) spray at different fruit development stages on the accumulation Ca and other macronutrients in cv. Hayward kiwifruit grown at two locations. In order to find the absorbality of Ca at different spraying times, fruits were harvested 7 days after a Ca treatment. Additionally, the mineral composition of kwifruit was determined at the stage of harvest ripeness. The results showed that the absorbality of Ca by kiwifruit from Ca spray decreased significantly with the progressing fruit development. The highest fruit Ca content was found when the fruit plants were sprayed at 35+80 DAFB and 35+80+120 DAFB, irrespectively of the location of an orchard. At a later Ca spraying application, the N content in kiwifruit significantly decreased, but the K and Mg content slightly increased. In contrast, the K/Ca, N/Ca, Mg/Ca and (K+Mg)/Ca ratios of CaCl2 sprayed fruits was lower than in the control and the ratio values were more balanced in the Ca treated fruit than in the control. Overall, three CaCl2 (15 g L-1) sprays could effectively improve the fruit quality by balancing the Ca ratio to other macronutrients. Therefore, Ca spray treatments could be a recommended treatment in growing cv. Hayward kiwifruit.
Źródło:
Journal of Elementology; 2016, 21, 1; 195-209
1644-2296
Pojawia się w:
Journal of Elementology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficiency of CaCl2 spray at different fruit development stages on the fruit mineral nutrient accumulation in cv. Hayward kiwifruit
Autorzy:
Shiri, M.A.
Ghasemnezhad, M.
Moghadam, J.F.
Ebrahimi, R.
Powiązania:
https://bibliotekanauki.pl/articles/15935.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie / Polskie Towarzystwo Magnezologiczne im. Prof. Juliana Aleksandrowicza
Tematy:
Actinidia deliciosa
fruit
development stage
mineral nutrient
nutrient accumulation
Hayward cultivar
kiwi fruit
calcium absorption
calcium chloride spray
Opis:
Despite the importance of calcium in many fruit species and the effects of calcium application, there is little or no reliable information on the effect of CaCl2 spray at different fruit development stages on the fruit mineral nutrient content during the growing season and at harvest. Therefore, this study has been conducted to evaluate the effect of calcium chloride (CaCl2, 15 g L-1) spray at different fruit development stages on the accumulation Ca and other macronutrients in cv. Hayward kiwifruit grown at two locations. In order to find the absorbality of Ca at different spraying times, fruits were harvested 7 days after a Ca treatment. Additionally, the mineral composition of kwifruit was determined at the stage of harvest ripeness. The results showed that the absorbality of Ca by kiwifruit from Ca spray decreased significantly with the progressing fruit development. The highest fruit Ca content was found when the fruit plants were sprayed at 35+80 DAFB and 35+80+120 DAFB, irrespectively of the location of an orchard. At a later Ca spraying application, the N content in kiwifruit significantly decreased, but the K and Mg content slightly increased. In contrast, the K/Ca, N/Ca, Mg/Ca and (K+Mg)/Ca ratios of CaCl2 sprayed fruits was lower than in the control and the ratio values were more balanced in the Ca treated fruit than in the control. Overall, three CaCl2 (15 g L-1) sprays could effectively improve the fruit quality by balancing the Ca ratio to other macronutrients. Therefore, Ca spray treatments could be a recommended treatment in growing cv. Hayward kiwifruit.
Źródło:
Journal of Elementology; 2016, 21, 1
1644-2296
Pojawia się w:
Journal of Elementology
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 14

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