https://orcid.org/0000-0001-8015-076X
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ABSTRACT
The energy losses of engines are usually estimated based on the first law of thermodynamics; however, it is incapable to reveal the quality of these losses. In this framework, the engagement of second law analysis (availability) has become progressively attractive. This paper aims to thermodynamically assess the availability and efficiency of a gasoline spark ignition internal combustion engine. For this purpose, a new subroutine of the second law of thermodynamic model was incorporated with an adapted program of the first law of thermodynamic model, which was formerly developed based on the two-zone combustion hypothesis. Details of an experimental setup were employed for model buildup. The measured results were adopted for model validation. In terms of the first law analysis, the modified model was well matched with the experimental observation of the in-cylinder pressure trend. In addition to influence of equivalence ratio and engine speed, analysis was performed to consider not extensively assessed parameters, namely, the combustion duration and residual gas fraction. The results showed that the stoichiometric condition (ϕ = 1) gave the best trends of the availability components. While, these trends were deteriorated as the combustion duration extended, and the residual gas fraction increased. In terms of availability distribution, its lost with exhaust gases was the highest one for all investigated parameters. Furthermore, the medium engine speed, 2000 rpm for current study, was nominated as the optimum operating condition. Maximum levels of engine efficiencies obtained for the first and second laws analyses were about 47.574% and 43.728%, respectively. The developed model can be extending for further evaluation in terms of alternative fuels aspect.
Nomenclatures
| Symbol | = | Description and Unit |
| Aex | = | Availability of exhaust, kJ/kg |
| AQ | = | Availability of heat, kJ/kg |
| AT | = | Total availability, kJ/kg |
| Atm | = | Thermomechanical availability, kJ/kg |
| Aw | = | Availability of work, kJ/kg |
| afch | = | Fuel chemical availability, kJ/kg |
| a0 | = | Availability of combustion |
| B | = | Bore of engine cylinder, m |
| (F/A)act | = | Actual fuel/air ratio |
| (F/A)st | = | Stoichiometric fuel/air ratio |
| f | = | Residual gas fraction |
| = | Standard state Gibbs function | |
| H | = | Enthalpy, kJ |
| h | = | Specific enthalpy, kJ/kg |
| = | Heat transfer coefficient | |
| I | = | Irreversibility, kJ/kg |
| = | Mass in a control volume, kg | |
| = | Mass flowrate, kg/s | |
| N | = | Engine speed, rpm |
| p | = | Pressure, Pa |
| = | Motoring pressure, Pa | |
| = | Heat transfer, kJ/kg | |
| r | = | Compression ratio |
| T | = | Temperature, K |
| t | = | Time interval, s |
| = | Internal energy, kJ | |
| = | Mean piston speed, m/s | |
| = | Specific Internal energy kJ/kg | |
| = | Volume, m3 | |
| = | Displaced volume, m3 | |
| = | Work, kJ/kg | |
| = | Average gas velocity, m/s | |
| = | Work per unit mass, kJ/kg | |
| = | Mole fraction | |
| = | Mass fraction burned | |
| Greek Symbols | = | |
| = | First and second law efficiency | |
| = | Equivalence ratio | |
| = | Specific heat ratio | |
| = | Relative ratio | |
| = | Chemical potential | |
| = | Instantaneous crank angle | |
| = | Spark timing | |
| = | Combustion duration | |
| = | Angular velocity, rad/s | |
| Subscripts | = | |
| a | = | Air |
| b | = | Burned zone |
| f | = | Fuel |
| l | = | Loss |
| o | = | At standard condition |
| p | = | Product |
| r | = | Reactant |
| u | = | Unburned zone |
Acknowledgments
The authors appreciate the given opportunity to perform the experimental work at University of Kirkuk with collaboration of Hawija Institute of Technology. Furthermore, authors are thankful to Dr. Ismail Altin from Karadeniz Technical University, Trabzon, Turkey, for his consultancy regarding the improvement of the model.
Additional information
Notes on contributors
Yahya F. Taha
Yahya F. Taha has awarded both the BSc and MSc degrees in Mechanical Engineering from College of Engineering - Tikrit University 2016 and 2019, respectively. His research area includes the thermodynamic analysis and simulation of ICEs as well as the alternative fuels aspect.
Hamed J. Khalaf
Hamed J. Khalaf is a senior lecturer of Mechanical Engineering at College of Engineering - Tikrit University. His research area includes the thermodynamic analysis and simulation of ICEs as well as the alternative fuels aspect.
Khalaf I. Hamada
Khalaf I. Hamada is an Assistant Professor of Mechanical Engineering at College of Engineering - Kirkuk University. He has awarded both the BSc and MSc degrees in Mechanical Engineering from College of Engineering - Tikrit University 2003 and 2006, respectively, while his PhD degree was given by University Malaysia Pahang at 2012. His research area includes the renewable energy, heat transfer, CFD, thermodynamic analysis and simulation of ICEs as well as the alternative fuels aspect.