Case Analysis

And Introduction
When taking their first thermodynamics course, engineering students learn about the Otto cycle (usually
during the sophomore year). The internal combustion engine with spark ignition (SI) is theoretically
based on this cycle (ICE). The conventional analysis of the Otto cycle (the air-standard analysis) is Given
appropriate information, the work per cycle for a given engine may be determined, however the
dynamic performance of a SI ICE cannot be predicted by a static thermodynamic analysis. The air-
standard analysis can be expanded to incorporate a calculation of the dynamic performance of a SI ICE,
though, by making three straightforward adjustments. The first of these changes is the choice of
representative values for the working fluid for each operation for certain heats and specific heat ratios.
This increases the analysis's accuracy. The second is an equation that connects important engine
characteristics (the fuel-air ratio and the compression ratio) to the heat released during combustion. The
third is the addition of an equation that describes how the engine's volumetric efficiency changes with
engine speed. This takes into account the single biggest loss and produces performance that is reliant on
engine speed. The derived analysis rather accurately forecasts the dynamic performance of modern SI
ICE engines (power and torque as a function of engine speed). The fact that engineering students taking
their first thermodynamics course can easily comprehend and perform this analysis is perhaps its most
significant benefit. Students have used this research to assess conventional engines for a range of
applications (different types of passenger cars, pick-up trucks, SUVs, Formula 1 cars, and even "monster"
trucks), with outstanding results.
Reversible gas cycle models of internal combustion engines are useful for illustrating
design parameters influencing engine performance. Recently, much attention has been
paid to optimize reciprocating heat engines by using reversible and irreversible gas cycles.
Design parameters at maximum power (mp) and maximum thermal efficiency were
investigated for the air standard Diesel cycle optimization. Yilmaz proposed a new
performance criterion for heat engine performance analysis, called efficient power, which
is defined as the multiplication of power by efficiency of the cycle. This criterion was
successfully applied to the Carnot and Brayton cycles. Rocha-Martinez et al. studied two
thermal cycles, the Otto and the Diesel cycles, under heat fluctuations. Ebrahimi examined
the effect of stroke length on performance of air standard Diesel cycle, Hou and Lin
examined the influences of heat loss, Adnan Parlak performed a Diesel cycle analysis
concerning heat transfer and combustion effects, Al-Hinti et al. presented the investigation
of air-standard Diesel cycle under irreversible heat transfer conditions, Yingru Zhao et al.
established an irreversible cycle model of the Diesel heat engine, Ebrahimi analyzed the
performance of an air standard Diesel cycle by using finite-time thermodynamics, and
Osman Azmi Ozsoysal analyzed the effects of varying air-fuel ratio on the performance of a
theoretical Diesel cycle. Ge et al. and Al-Sarkhi et al. used finite-time thermodynamics to
analyze the performance of an air-standard Diesel cycle with heat transfer loss and variable
specific heats of working fluid. Fallahipanah et al. reviewed the irreversible cycle of
biodiesel fuel and its compounds by means of thermodynamics laws and finite time
thermodynamics. Ebrahimi and Chen investigated the effects of the variable specific heat
ratio of the working fluid on the performance of a Diesel cycle, with considerations of heat
transfer and friction like term losses. Performance optimization of a Diesel cycle is carried
out based on efficient power criterion, mpd and mep. A cycle model is established and the
power output and efficiency of the cycle are maximized with respect to the main
parameters affecting the cycle performance. The optimal parameters are presented as
characteristic curves.
The fuel conversion efficiency (FCE) is a measure of engine efficiency. It is determined by

the ratio of the work produced per cycle to the amount of fuel energy supplied per cycle
that can be released in the combustion process. Fuel energy is described by the mass of
fuel supplied to the engine per cycle times the heating value of fuel. The original
contribution of this paper is based on any fraction of the fuel’s chemical energy not fully
released inside the engine during actual combustion process due to incomplete
combustion. The utilization ratio introduces the combustion efficiency. The mass of fuel
supplied to the engine per cycle is fixed and a fraction of the fuel’s chemical energy, Qin,
can be transferred into the working fluid. Combustion efficiency (or utilization ratio of fuel’s
energy) can be described as the ratio of Qin to Qfuel. The ratio of the waste energy Q waste
to the fuel’s chemical energy Qfuel denotes the unutilized portion of fuel’s energy. Internal
combustion engines are an open system which exchange heat and work with their
surrounding environment. The availability conversion efficiency is the ratio of actual work
to maximum work, which is equivalent to increment in Gibbs free energy when combustion
is complete. This paper studies an irreversible Dual cycle model with considering
irreversibility’s coming exclusively from expansion and compression processes. It aims to
investigate the effects of combustion efficiency on an irreversible Dual cycle with varying
fuel–air ratio. The developed mathematical model and combustion efficiency approach
could lead to a qualitative understanding of how engine loss can be reduced. The classical
equilibrium thermodynamic is the most useful choice for modeling thermal engines, as it
provides the limiting cases of possible processes and employs reversible cycles to obtain
upper bounds of engine efficiencies. Heat transfer irreversibility between the working fluid
and the cylinder walls should not be neglected when approaching a real cycle analysis. Dual
cycle studies are categorized in two groups based on the classical thermodynamic
approach and finite time thermodynamic approach. Any and all results of finite-time
thermodynamic works can be developed using classical thermodynamic approaches. In
recent years, many performance optimization studies about internal combustion engines
have been established on the heat leak loss through the cylinder walls. These studies
generally use a simple expression of the heat leak loss that obeys a Newtonian law.
Preliminary models leading to a qualitative understanding of how engine loss could be
reduced are introduced by Mozurkewich and Berry for an ideal Otto cycle. Heat transfer to
the cylinder walls was assumed to be a linear function of the difference between the
average gas and cylinder wall temperatures during the energy release processes. Effects of
combustion on a power-optimized Endo reversible dual cycle were given by Blank and Wu.
Effects of heat transfer on the network for an air-standard Diesel cycle were carried out by
Chen et al. Similar models were also developed by Akash for an air-standard Diesel cycle.
Suitable models for an air-standard Dual cycle were presented in Lin et al. and Hou. How
irreversible work and efficiency be able to maximize in an Otto cycle and in a Brayton cycle
was explained in Aragon-Gonzales et al.
Objects
 This study developed a First Law of Thermodynamics analysis to predict

performance curves for contemporary automotive engines. It uses the assumptions
of the idealized Otto cycle, with two exceptions: the mass of air in the cylinder is
dependent on engine speed, geometry, and ambient temperature and pressure.
The specific heats used are assumed constant, but their numerical values are
determined at mean temperatures. The quantity of heat transferred during the
heating process is related to engine parameters.
 This work aims to determine and optimize the utilizable work output in an
irreversible Dual cycle. The dual cycle model contains irreversibility’s coming
exclusively from expansion and compression processes, and the mass of fuel
supplied to the engine per cycle is fixed. Combustion efficiency is utilized as a factor
to investigate how effects on an irreversible Dual cycle with varying fuel–air ratio.
The developed mathematical model leads to a qualitative understanding of how
engine loss can be reduced, and the upper limit for compression ratio is evaluated
by means of using some constraints for realizing the Dual cycle. Thermal efficiency,
irreversible work, cut-off ratio, pressure ratio and fuel conversion efficiency are
obtained in terms of isentropic efficiencies, maximum and minimum temperatures,
combustion efficiency and air–fuel ratio. Valid ranges of the mentioned constants
are explained and discussed in the following section.
 This study compares the performance of a reversible air standard Diesel cycle based
on three performance criteria: maximum power, maximum power density and
maximum efficient power. The results show that design parameters at mep
conditions lead to more efficient engines than at mp conditions, and that the mep
criterion may have a significant power advantage compared to mpd.

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And Introduction

The fuel conversion efficiency (FCE) is a measure of engine efficiency. It is determined by

 This study developed a First Law of Thermodynamics analysis to predict

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