Irreversible Dual Cycle Research Articles

Power Density Analysis and Multi-Objective Optimization for an Irreversible Dual Cycle

Abstract Considering the various irreversibility conditions caused by heat transfer and working processes in a dual cycle, the power density performance is optimized by applying finite-time thermodynamics theory, and multi-objective optimization is performed by using NSGA-II. The effects of cut-off ratio, maximum cycle temperature ratio, and various losses by heat transfer and working processes on the relationships between the power density and the compression ratio and between the power density and the thermal efficiency are analyzed. The thermal efficiency and engine size obtained under the conditions of maximum power output and power density are discussed. The results show that for a dual cycle, the heat engine has a smaller size and higher thermal efficiency under the condition of maximum power density. The cycle compression ratio and cut-off ratio are selected as decision variables, and the dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density are selected as objective functions. Multi-objective optimization is performed with different objective combinations. The deviation indexes under the LINMAP, TOPSIS, and Shannon entropy approaches are discussed, and the number of generations when the genetic algorithm reaches convergence are obtained. The results show that the genetic algorithm converges at the 341st generation for the quadru-objective optimization, at the 488th generation for the tri-objective optimization, and at the 399th generation for the bi-objective optimization. When the bi-objective optimization is performed with dimensionless power output and dimensionless ecological function as the objective functions, the deviation index obtained based on the LINMAP approach is 0.1400, which is better than those obtained for other single- and multi-objective optimizations.

Effects of design and operating parameters on entropy generation of a dual cycle

In this paper, a performance analysis based on the entropy generation and thermal efficiency has been carried out for the irreversible dual cycle. The results show that the compression ratio versus entropy generation characteristic, the pressure ratio versus entropy generation characteristic, the compression ratio versus thermal efficiency characteristic, the pressure ratio versus thermal efficiency characteristic and the initial temperature versus thermal efficiency characteristic are approximately parabolic-like curves. There is negative linear relationship between entropy generation and environment temperature, between entropy generation and compression efficiency, and between entropy generation and expansion efficiency. There is positive linear relationship between entropy generation and initial temperature, between thermal efficiency and compression efficiency, and between thermal efficiency and expansion efficiency.

Thermodynamic analysis and optimization of an irreversible nano scale dual cycle operating with Maxwell-Boltzmann gas

In last decades, nano technology was developed. Since, nano scale thermal cycles will be possibly employed in near future. In this research, a nano scale irreversible dual cycle is investigated thermodynamically for optimization of performance. Ideal Maxwell-Boltzmann gas is used for working fluid in the system. It is chosen as working fluid. In this paper, two scenarios are introduced for optimization process. The outcomes of each of the scenarios are evaluated independently. Throughout first scenario, in order to maximize the dimensionless output work and first law efficiency of the system, multi-objective optimization algorithms are employed. Furthermore, in second scenario, two objective functions comprising the dimensionless output work are the dimensionless ecological function are maximized concurrently via employing multi objective optimization algorithms. The multi objective evolutionary approaches (MOEAs) on the basis of NSGA-II method are employed in this paper Decision making is done via three methods including LINAMP and TOPSIS and FUZZY. Finally, error analysis is implemented on the results obtained in this research

Determining of the optimum performance of a nano scale irreversible Dual cycle with quantum gases as working fluid by using different methods

In this paper, a nano scale irreversible Dual cycle working with ideal Bose and Fermi gases is examined. Degeneracy conditions and thermo-size effects on the quantum gases are researched. Thermodynamic analyses of the cycle are conducted by considering irreversibilities. Different thermodynamic assessment methods are applied and then compared to each other. The obtained results are presented numerically. It concluded that ECF is the most convenient method for the Bose gas under weak degeneracy condition and x should be chosen as biggest as possible for all other conditions.

Determining performance of an irreversible nano scale dual cycle operating with Maxwell–Boltzmann gas

In last decades, nano technology developed. Since, nano scale thermal cycles will be possibly used in near future. In this study, a nano scale irreversible dual cycle was analyzed thermodynamically. Ideal Maxwell–Boltzmann gas is used for working fluid in the system. He4 is chosen as working fluid. Results are obtained as numerically. In calculations, different thermodynamic performance evaluation methods are applied and these methods are compared each other to determine the most convenient optimization way.

Heat transfer effects on the performance of an air-standard irreversible dual cycle

The objective of this study is to analyse the effects of heat transfer loss and internal irreversibilites, resulting from adiabatic processes, on an irreversible diesel heat engine. Thermodynamic optimisation has been carried out based on the Maximum Power (MP), Maximum Thermal Efficiency (MEF) and Maximum mean Effective Pressure (MEP) criteria for the dual cycle. Power output, thermal efficiency and mean effective pressure are obtained by introducing variable compression ratio, inlet temperature, combustion and heat transfer constants, and compression and expansion efficiencies. Optimal performance and design parameters of the dual cycle are obtained numerically for the MP, MEF and MEP conditions. The optimal compression ratio and pressure ratio at MEP conditions are compared with those results obtained by using the MP and MEF criteria for different constants of heat transfer and combustion in the characteristic grid curves. The results obtained in this paper may provide a guide to the performance and improvement of practical diesel engines.

Thermodynamic simulation of performance of a dual cycle with stroke length and volumetric efficiency

This article presents finite-time thermodynamics analysis of an irreversible air standard dual cycle. An irreversible dual cycle model which is more close to practice is established. In this model, the effects of stroke length and volume efficiency by considering the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss, the internal irreversibility, and heat transfer loss are analyzed. The results show that if compression ratio is less than certain value, the power output increases with increasing stroke length, while if compression ratio exceeds certain value, the power output first increases and then starts to decrease with increasing stroke length. With further increase in compression ratio, the increase of stroke length results in decreasing the power output. The results also show that, throughout the compression ratio range, the power output increases with the increasing volumetric efficiency. The results obtained in this study are of importance to provide good guidance for performance evaluation and improvement of practical internal combustion engines.

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

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

Finite-time thermodynamic modeling and analysis for an irreversible Dual cycle

The performance of an air standard Dual cycle is analyzed by using finite-time thermodynamics. An irreversible Dual cycle model which is more close to practice is established. 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, the internal irreversibility described by using the compression and expansion efficiencies, and heat transfer loss are considered. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, and the optimal relation between power output and the efficiency of the Dual cycle are derived by detailed numerical examples. Moreover, the effects of internal irreversibility, heat transfer loss, frictional loss and pressure ratio on the cycle performance are analyzed. The power output versus compression ratio and efficiency versus compression ratio curves of the Diesel and Otto cycles are the maximum and minimum envelope lines of the performance of the Dual cycle, respectively. The results obtained herein may provide guidelines for the design of practical internal combustion engines.

Optimization of an Irreversible Diesel Cycle: Experimental Results of a Ceramic Coated Indirect-Injection Supercharged Diesel Engine

In this work, an irreversible dual cycle analysis has been performed for enhancing the characteristics of a low heat rejection (LHR) supercharged single-cylinder indirect-injection (IDI) diesel engine. A relation which gives the maximum power (MP) and the corresponding efficiency has been derived analytically. Optimization of the diesel cycle has been performed for power and thermal efficiency with respect to the pressure ratio and temperature ratio. Optimum values of the pressure ratio and cutoff ratio of the diesel cycle, depending on the temperature ratios, have been derived analytically and compared to the results of an experimental study of the LHR engine, whose optimum performance was obtained by increasing the temperature in the combustion chamber. Effects of a ceramic coating on performance and exhaust emissions in the LHR engine have been compared to those obtained from the standard (STD) diesel engine based on the comparison of the STD and the LHR engines for identical airflow and brake mean effective pressure. Intake pressure was adjusted to give the same air consumption as the corresponding STD engine for the same brake mean effective pressure (BMEP) and engine speed to avoid a reduction in the volumetric efficiency of the LHR engine. In comparison to the STD engine, satisfactory performance was obtained with the LHR engine. Specific fuel consumption was decreased up to 4.5%, and brake efficiency was increased by 1.5%. NOx emissions were increased by 12% because of the higher flame temperature in the LHR engine.

Effects of heat transfer, friction and variable specific heats of working fluid on performance of an irreversible dual cycle

The thermodynamic performance of an air standard dual cycle with heat transfer loss, friction like term loss and variable specific heats of working fluid is analyzed. 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 derived by detailed numerical examples. Moreover, the effects of variable specific heats of the working fluid and the friction like term loss on the irreversible cycle performance are analyzed. The results show that the effects of variable specific heats of working fluid and friction like term loss on the cycle performance are obvious, and they should be considered in practical cycle analysis. The results obtained in this paper may provide guidance for the design of practical internal combustion engines.

Performance analysis and optimization of an irreversible dual-cycle based on an ecological coefficient of performance criterion

An ecological performance analysis for an irreversible dual cycle has been performed by employing the new thermo-ecological criterion as the objective function. The objective function is the ecological coefficient of performance (ECOP) and defined as the power output per unit loss rate of availability. A comprehensive numerical study is carried out to investigate the general and optimal performances of the irreversible dual-cycle having a finite-rate of heat transfer, heat leak and internal irreversibilities based on the ECOP objective function. Comparisons with an alternative ecological function defined in the literature and also with the maximum power output condition are provided to establish the utility of the new ecological performance coefficient. The results indicate that the dual cycle considered working at maximum ECOP conditions has a significant advantage in terms of entropy-generation rate and thermal efficiency.

04/02510 Performance optimisation of an irreversible dualcycle with respect to pressure ratio and temperature ratio-experimental results of a ceramic coated IDI diesel engine: Parlak, A. et al. Energy Conversion and Management, 2004, 45, (7–8), 1219–1232

04/02510 Performance optimisation of an irreversible dualcycle with respect to pressure ratio and temperature ratio-experimental results of a ceramic coated IDI diesel engine: Parlak, A. et al. Energy Conversion and Management, 2004, 45, (7–8), 1219–1232

Optimal performance of an irreversible dual-cycle

The finite-time thermodynamic performance of an air-standard dual cycle, with heat transfer and friction-like term losses, is analyzed and optimized in this paper. The relations between the power output and the compression ratio, and between the thermal efficiency and the compression ratio of the cycle are derived. Moreover, the effects of heat transfer and global losses lumped in a friction-like term on the performance of the cycle are shown by detailed numerical examples.

Performance optimisation of an irreversible dual cycle with respect to pressure ratio and temperature ratio––experimental results of a ceramic coated IDI Diesel engine

An irreversible dual cycle analysis has been performed. Optimisation of the cycle has been performed for power and thermal efficiency with respect to pressure ratio and temperature ratio. Optimum values of pressure ratio and cut-off ratio of the dual cycle, depending on temperature ratios, have been derived analytically and compared with the results of an experimental study of a low heat rejection indirect injection Diesel engine, whose optimum performance was obtained by retarding the injection timing related to the temperature increase in the combustion chamber. Injection timing was retarded from 38 crank angle (CA) to 32 CA. Optimum performance was obtained at 34 CA. At this injection timing, in comparison to the standard Diesel engine, the decrease in the specific fuel consumption and the increase in the brake thermal efficiency were about 6% and 2%, respectively.