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1
Content available remote

Investigation of an Alternative Fuel for Diesel Engines

100%
Keven A., Karaali R.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-282-B-285
EN
Internal combustion engines use generally fossil fuel products. World resources of it is limited. Renewable alternative energy sources are getting important solution for energy demand. Hazelnut oil ethyl ester is obtained from raw hazelnut and mixed with diesel oil in certain proportions to use in a four-stroke direct injected single cylinder diesel engine. In this study the effects of the mixture of diesel oil with hazelnut oil ethyl ester on the engine performance and exhaust gas emissions are investigated for the first time in literature. The fuel injection system is regulated to use the mixture in the engine for the investigation. The results show that, the mixture with 25% ethyl ester extracted from hazelnut oil can be used as an alternative fuel without any change or regulation of the diesel engine.
2
Content available remote

Power Optimization of a Miller Thermal Cycle with respect to Residual Gases and Equivalence Ratio

80%
Ebrahimi R.
Acta Physica Polonica A
|
2013
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vol. 124
|
issue 1
6-10
EN
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.
3
Content available remote

Effects of Equivalence Ratio and Mean Piston Speed on Performance of an Irreversible Dual Cycle

80%
Ebrahimi R.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 3
384-389
EN
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.
4
Content available remote

Thermodynamic Modeling of an Atkinson Cycle with respect to Relative Air-Fuel Ratio, Fuel Mass Flow Rate and Residual Gases

80%
Ebrahimi R.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 1
29-34
EN
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.
5
Content available remote

The Effects of Cycle Temperature and Cycle Pressure Ratios on the Performance of an Irreversible Otto Cycle

80%
Ust Y., Sahin B., Safa A.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 3
412-416
EN
This paper reports the thermodynamic optimization based on the maximum mean effective pressure, maximum power and maximum thermal efficiency criteria for an irreversible Otto heat engine model which includes internal irreversibility resulting from the adiabatic processes. The mean effective pressure, power output, and thermal efficiency are obtained by introducing the compression ratio, cycle temperature ratio, specific heat ratio and the compression and expansion efficiencies. Optimal performance and design parameters of the Otto cycle are obtained analytically for the maximum power and maximum thermal efficiency conditions and numerically for the maximum mean effective pressure conditions. The results at maximum mean effective pressure conditions are compared with those results obtained by using the maximum power and maximum thermal efficiency criteria. The effects of the cycle temperature ratio and cycle pressure ratio on the general and optimal performances are investigated.
6
Content available remote

Effects of Variable Specific Heat Ratio on Performance οf an Endoreversible Otto Cycle

80%
Ebrahimi R.
|
|
issue 6
887-891
EN
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.
7
Content available remote

Performance Analysis of a Diesel Cycle under the Restriction of Maximum Cycle Temperature with Considerations of Heat Loss, Friction, and Variable Specific Heats

80%
Hou S., Lin J.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 6
979-986
EN
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.
8
Content available remote

Performance Analysis of a Dual Cycle Engine with Considerations of Pressure Ratio and Cut-Off Ratio

80%
Ebrahimi R.
|
|
issue 4
534-539
EN
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.
9
Content available remote

Effect of Expansion-Compression Ratio on Performance of the Miller cycle

80%
Ebrahimi R.
Acta Physica Polonica A
|
2012
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vol. 122
|
issue 4
645-649
EN
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.
10
Content available remote

Second Law Analysis on an Air-Standard Miller Engine

80%
Ebrahimi R.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 6
1079-1082
EN
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.
11
Content available remote

Thermoeconomic Analyses of Steam Injected Gas Turbine Cogeneration Cycles

80%
Karaali R., Öztürk İ.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-279-B-281
EN
In this study, three different gas turbine cogeneration systems that are preheating air, preheating air-fuel and simple cycles where steam injected in to combustion chamber are analyzed. The effects of steam injection on thermoeconomic performance are calculated and obtained. By using the first law of thermodynamics, the exergy analysis and economic methods, simulation programs written by the authors in FORTRAN code are obtained to use for the analyses. Thermoeconomic performance of these three different cycles for different stage and variable mass of injected steam are obtained and compared with literature. The effects of injection steam in to combustion chambers of those three cycles for variable compressing ratios, on power, efficiencies, product price and performances are obtained. Consequently, the advantages and the disadvantages of injection steam are evaluated. The results obtained in this study are compared with the results available in the literature. Injection steam into combustion chamber increases the electricity efficiency and electricity power but decreases the heat power of the cycles. Also the produced electricity price for per kWh is increasing.
12
Content available remote

The Influence of Potential Energy Shape on the Total Electrical Efficiency of the Energy Harvester

80%
Kucab K., Górski G.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 1
118-120
EN
In this theoretical work we analyze the total effective electric power versus base acceleration amplitude generated by the energy harvesting system with an electromagnetic transducer. We compare the results for both linear and nonlinear case. The transition from linear to nonlinear behavior of the system can be achieved by the change of device geometry. To improve the power efficiency of our device we also examine the dependence of crossover point of acceleration amplitudes where generated power in the nonlinear system starts to exceed the generated power in the linear regime. We have found that the crossover point can be moved towards relatively small base acceleration values by appropriate selection of system nonlinearity "strength".
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