Second-law analyses applied to internal combustion engines operation
Introduction
Internal combustion engine simulation modeling has long been established as an effective tool for studying engine performance and contributing to evaluation and new developments. Thermodynamic models of the real engine cycle have served as effective tools for complete analysis of engine performance and sensitivity to various operating parameters [1], [2], [3], [4], [5], [6].
On the other hand, it has long been understood that traditional first-law analysis, which is needed for modeling the engine processes, often fails to give the engineer the best insight into the engine's operation. In order to analyze engine performance—that is, evaluate the inefficiencies associated with the various processes—second-law analysis must be applied [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. For second-law analysis, the key concept is ‘availability’ (or exergy1). The availability content of a material represents its potential to do useful work. Unlike energy, availability can be destroyed which is a result of such phenomena as combustion, friction, mixing and throttling. The relationships needed to evaluate availability content, the transports of availability and availability destruction can be found in Refs. [7], [8], [9], [10], [11], [12], [13], [14].
The destruction of availability—often termed irreversibility—is the source for the defective exploitation of fuel into useful mechanical work in a compression or spark ignition engine. The reduction of irreversibilities can lead to better engine performance through a more efficient exploitation of fuel. To reduce the irreversibilities, we need to quantify them. That is we need to evaluate the availability destructions-we need the second-law analysis [12], [17], [18].
Objectives of second-law application to internal combustion engines are:
- •
To weigh the various processes and devices, calculating the ability of each one of these to produce work.
- •
To identify those processes in which destruction or loss of availability occurs and to detect the sources for these destructions.
- •
To quantify the various losses and destructions.
- •
To analyze the effect of various design and thermodynamic parameters on the exergy destruction and losses.
- •
To propose measures/techniques for the minimization of destruction and losses, to increase overall efficiency.
- •
To propose methods for exploitation of losses—most notably exhaust gas to ambient and heat transfer to cylinder walls—now lost or ignored.
- •
To define efficiencies so that different applications can be studied and compared, and possible improvements measured.
Many studies have been published in the past few decades (the majority during the last 20 years), concerning second-law application to internal combustion engines—one such review paper is written by Caton [19]. The present work expands considerably upon that paper, with a different philosophy and perspective, providing details about equations used for second-law application to internal combustion engines operation, i.e. state properties, basic first-law equations, fuel chemical availability, availability equations for the engine cylinder and each engine's subsystem, entropy balance equations, second-law efficiency and basic relations for the application of the second-law analysis during transient operation. It also covers all recent publications in light of new developments such as alternative fuels and transient operation. Details about the main data, i.e. engine characteristics, modeling assumptions, etc. and—in particular—the findings of each previous study are given in this paper. Tabulation of energy and availability balances is given for many types of engines, accompanied by figures showing the effect of the most important parameters on the second-law performance of internal combustion engines.
Section snippets
Availability of a system
The availability of a system in a given state can be defined as the maximum useful work that can be produced through interaction of the system with its surroundings, as it reaches thermal, mechanical and chemical equilibrium. Usually, the terms associated with thermomechanical and chemical equilibration are differentiated and calculated separately.
For a closed system experiencing heat and work interactions with the environment, the following equation holds, for the thermomechanical availability
First-law arguments used in tandem with second-law analyses of internal combustion engines2
The majority of studies concerning second-law application to internal combustion engines are based on a preceding first-law mathematical modeling of the various processes inside the cylinder and its subsystems. These will be discussed briefly as they constitute the basis for the second-law analysis.
State properties
For the evaluation of specific internal energy of species i, the following relation can be applied according to JANAF Table thermodynamic data [1], [5], [46], [47]:where constants ain for the above polynomial relation can be found, for example, in Refs. [1], [5]. Two sets of data are available for constants ain, one for temperatures up to 1000 K and another for temperatures from 1000 to 5000 K. The reference temperature is 298 K. Also,The rate of
Engine analysis: application of exergy balance to internal combustion engines
In the following subsections, the equations will be given that deal with the exergy balance applied to the engine cylinder and its subsystems in order to evaluate the various processes irreversibilities. However, the fuel chemical availability must first be defined.
Second-law or exergy or exergetic efficiencies
An efficiency is defined in order to be able to compare different engine size applications or evaluate various improvements effects, either from the first- or the second-law perspective. The second-law (or exergy or availability) efficiency also found in the literature as effectiveness or exergetic efficiency, measures how effectively the input (fuel) is converted into product, and is usually of the form [7], [8], [9], [10], [11], [12], [13], [14], [23]:
Review of various parameters effect on the second-law balance of fundamental modes of steady-state, in-cylinder operation
To the best of the authors' knowledge, the first studies of internal combustion engines operation that included exergy balance in the calculations were, around 1960, the works of Traupel [62], and Patterson and Van Wylen [63]. Most of the studies, however, were published from the second half of the 80s onwards, as will be discussed in the following Subsections. The most important findings of each research group will be presented and analyzed in the following sections. By so doing, we will be
Low heat rejection engines
During the last two decades there has been an increasing interest in the low heat rejection (or sometimes loosely termed ‘adiabatic’) engine. The objective of a low heat rejection cylinder is to minimize heat loss to the walls, eliminating the need for a coolant system. This is achieved through the increased level of temperatures inside the cylinder resulting from the insulation applied to the cylinder walls [1], [2], [3], [4], [5], [33], [88], [89], [90], [91]. By so doing, a reduction can be
Review of second-law balances applied to transient operation
The transient response of naturally aspirated and turbocharged (compression ignition) engines forms a significant part of their operation and is of critical importance, due to the often non-optimum performance involved. For the diesel engines used for industrial applications, such as generators, rapid loading is required together with zero (final) speed droop for the base units, as well as rapid start-up for the stand-by ones. For other less critical (in terms of speed change) applications,
Overall-comparative results
Data and results from the analyses discussed in 7 Review of various parameters effect on the second-law balance of fundamental modes of steady-state, in-cylinder operation, 8 Review of second-law balance of other engine configurations, 9 Review of second-law balances applied to transient operation are summarized below. Table 6 summarizes the basic data of the previous research works in the field of second-law application to internal combustion engines. It includes, among other things,
Summary and conclusions
A detailed survey was presented concerning the works committed so far to the application of the second-law of thermodynamics in internal combustion engines. Detailed equations were given for the evaluation of state properties, the first-law of thermodynamics, fuel chemical availability, the second-law of thermodynamics applied to all engine subsystems and the definition of second-law efficiencies together with explicit examples.
The research in the field of the second-law application to internal
Acknowledgements
The authors would like to thank Assistant Prof D.C. Kyritsis with University of Illinois at Urbana-Champaign for his kind assistance with literature gathering, and Dr E.G. Pariotis for his valuable consultation in preparing the figures.
References (100)
Thermoeconomic analysis and optimization of energy systems
Prog Energy Combust Sci
(1993)- et al.
Exergy-aided cost minimization
Energy Convers Manage
(1997) - et al.
Availability analysis of a turbocharged diesel engine operating under transient load conditions
Energy
(2004) - et al.
Choice of a reference state for exergetic analysis
Energy
(1990) - et al.
Validation and sensitivity analysis of a two-zone diesel engine model for combustion and emissions prediction
Energy Convers Manage
(2004) - et al.
Analysis of combustion chamber insulation effects on the performance and exhaust emissions of a DI diesel engine using a multi-zone model
Heat Recov Syst CHP
(1995) - et al.
Second-law analysis of an ideal otto cycle
Energy Convers Manage
(1988) Ambient temperature and humidity effects on the performance and nitric oxide emission of spark ignition engined vehicles in Athens/Greece
Solar Wind Technol
(1988)Butanol—a single-cylinder engine study: availability analysis
Appl Therm Eng
(1997)- et al.
The effect of thermal barrier coating on a turbo-charged diesel engine performance and exergy potential of the exhaust gas
Energy Convers Manage
(2005)
Development of cumulative and availability rate balances in a multi-cylinder turbocharged IDI diesel engine
Energy Convers Manage
Chemical energies and exergies of fuels
Energy
On the destruction of availability (exergy) due to combustion processes—with specific application to internal-combustion engines
Energy
Thermodynamic cycle simulation of the diesel cycle: exergy as a second law analysis parameter
Int Commun Heat Mass Transfer
Energy–exergy analysis of a diesel engine
Heat Recov Syst CHP
Availability accumulation and destruction in a DI diesel engine with special reference to the limited cooled case
Heat Recov Syst CHP
Speed and load effects on the availability balances and irreversibilities production in a multi-cylinder turbocharged diesel engine
Appl Therm Eng
The effect of heat transfer on performance of the diesel cycle and exergy of the exhaust gas stream in an LHR diesel engine at the optimum injection timing
Energy Convers Manage
Performance characteristics of a diesel engine power plant
Energy Convers Manage
Fundamentals of analyses of processes
Energy Convers Manage
Evaluation of a spark ignition engine cycle using first and second law analysis techniques
Energy Convers Manage
Entropy generation in a diesel engine turbocharging system
Energy
Components heat transfer studies in a low heat rejection DI diesel engine using a hybrid thermostructural finite element model
Appl Therm Eng
The influence of cylinder wall temperature profile on the second-law diesel engine transient response
Appl Therm Eng
Comparative second-law analysis of internal combustion engine operation for methane, methanol and dodecane fuels
Energy
Simulation and exergy analysis of transient diesel engine operation
Energy
Internal combustion engine fundamentals
Internal combustion engines
Introduction to internal combustion engines
Internal combustion engines
Fundamentals of thermodynamics
Equilibrium thermodynamics for engineers and scientists
Availability analysis: a guide to efficient energy use
Advanced engineering thermodynamics
Fundamentals of engineering thermodynamics
Thermal design and optimization
Thermodynamics
Thermodynamics
Available energy: II. Gibbs extended
Trans ASME J Energy Res Technol
The component equations of energy and exergy
Trans ASME J Energy Res Technol
The application of availability and energy balances to a diesel engine
Trans ASME J Eng Gas Turbines Power
Second-law analysis of diesel engine combustion
Trans ASME J Eng Gas Turbines Power
Cited by (410)
Exergy destruction behavior of chemical reactions during the auto-ignition of methane doped with hydrogen
2024, International Journal of Hydrogen EnergySecond law analysis of an internal combustion engine for different fuels consisting of NaBH<inf>4</inf>, ethanol and methanol mixtures
2024, International Journal of Hydrogen EnergyEffects of temperature and pressure fluctuations on exergy loss characteristics of hydrogen auto-ignition processes
2023, International Journal of Hydrogen Energy