A Cycle Simulation Including the Second Law of Thermodynamics for a Spark-Ignition Engine: Implications of the Use of Multiple-Zones for Combustion

2002 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Second Law Of Thermodynamics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Cycle Simulation

Utilizing a Cycle Simulation to Examine the Use of EGR for a Spark-Ignition Engine Including the Second Law of Thermodynamics

2006 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Combustion Process ◽  
Second Law Of Thermodynamics ◽  
Thermodynamic Cycle ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Base Case ◽  
Nitric Oxides ◽  
Automotive Engine ◽  
Cycle Simulation

The use of exhaust gas recirculation (EGR) for a spark-ignition engine was examined using a thermodynamic cycle simulation including the second law of thermodynamics. Both a cooled and an adiabatic EGR configuration were considered. The engine was a 5.7 liter, automotive engine operating from idle to wide open throttle, and up to 6000 rpm. First, the reduction of nitric oxides is quantified for the base case condition (bmep = 325 kPa, 1400 rpm, φ = 1.0 and MBT timing). Over 90% reduction of nitric oxides is obtained with about 18% EGR for the cooled configuration, and with about 26% EGR for the adiabatic configuration. For constant load and speed, the thermal efficiencies increase with increasing EGR for both configurations, and the results show that this increase is mainly due to decreasing pumping losses and decreasing heat losses. In addition, results from the second law of thermodynamics indicated an increase in the destruction of availability (exergy) during the combustion process as EGR levels increase for both configurations. The major reason for this increase in the destruction of availability was the decrease in the combustion temperatures. Complete results for the availability destruction are provided for both configurations.

First and Second Law Analyses of a Spark-Ignition Engine Using Either Isooctane or Hydrogen: An Initial Assessment

2006 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Nitric Oxide ◽  
Thermal Efficiency ◽  
Equivalence Ratio ◽  
Performance Metrics ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Cycle Simulation ◽  
Nitric Oxide Emissions

The use of either hydrogen or isooctane for a spark-ignition engine was examined using a thermodynamic cycle simulation including the second law of thermodynamics. The engine studied was a 5.7 liter, automotive engine operating from idle to wide open throttle. The hydrogen or isooctane was assumed premixed with the air. Two features of hydrogen combustion that were included in the study were the higher flame speeds (shorter burn durations) and the wider lean flammability limits (lean equivalence ratios). Three cases were considered for the use of hydrogen: (1) standard burn duration and an equivalence ratio of 1.0, (2) a shorter burn duration and an equivalence ratio of 1.0, and (3) a shorter burn duration and variable, lean equivalence ratios. The results included thermal efficiencies, other performance metrics, second law parameters, and nitric oxide emissions. In general, for the cases with an equivalence of 1.0, the brake thermal efficiency was slightly lower for the hydrogen cases due to the higher temperatures and higher heat losses. For the variable, lean equivalence ratio cases, the thermal efficiency was higher for the hydrogen case relative to the isooctane case. Due to the higher temperatures, the hydrogen cases had over 50% higher nitric oxide emissions compared to the isooctane case at the base conditions. In addition, the second law analyses indicated that the destruction of availability during the combustion process was lower for the base hydrogen case (11.2%) relative to the isooctane case (21.1%).

Studying the effects of hydrogen addition on the second-law balance of a biogas-fuelled spark ignition engine by use of a quasi-dimensional multi-zone combustion model

2008 ◽  
Vol 222 (11) ◽  
pp. 2249-2268 ◽  
Author(s):  
C D Rakopoulos ◽  
C N Michos ◽  
E G Giakoumis
Keyword(s):  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Combustion Model ◽  
Second Law ◽  
Si Engine ◽  
Engine Operation ◽  
Hydrogen Addition ◽  
Cycle Simulation ◽  
Hydrogen Enrichment

Although a first-law analysis can show the improvement that hydrogen addition impacts on the performance of a biogas-fuelled spark-ignition (SI) engine, additional benefits can be revealed when the second law of thermodynamics is brought into perspective. It is theoretically expected that hydrogen enrichment in biogas can increase the second-law efficiency of engine operation by reducing the combustion-generated irreversibilities, because of the fundamental differences in the mechanism of entropy generation between hydrogen and traditional hydrocarbon combustion. In this study, an experimentally validated closed-cycle simulation code, incorporating a quasi-dimensional multi-zone combustion model that is based on the combination of turbulent entrainment theory and flame stretch concepts for the prediction of burning rates, is further extended to include second-law analysis for the purpose of quantifying the respective improvements. The analysis is applied for a single-cylinder homogeneous charge SI engine, fuelled with biogas—hydrogen blends, with up to 15 vol% hydrogen in the fuel mixture, when operated at 1500r/min, wide-open throttle, fuel-to-air equivalence ratio of 0.9, and ignition timing of 20° crank angle before top dead centre. Among the major findings derived from the second-law balance during the closed part of the engine cycle is the increase in the second-law efficiency from 40.85 per cent to 42.41 per cent with hydrogen addition, accompanied by a simultaneous decrease in the combustion irreversibilities from 18.25 per cent to 17.18 per cent of the total availability of the charge at inlet valve closing. It is also illustrated how both the increase in the combustion temperatures and the decrease in the combustion duration with increasing hydrogen content result in a reduction in the combustion irreversibilities. The degree of thermodynamic perfection of the combustion process from the second-law point of view is quantified by using two (differently defined) combustion exergetic efficiencies, whose maximum values during the combustion process increase with hydrogen enrichment from 49.70 per cent to 53.45 per cent and from 86.01 per cent to 87.33 per cent, respectively.

scholarly journals EXERGY DESTRUCTION AND CHEMICAL IRREVERSIBILITIES DURING COMBUSTION IN SPARK – IGNITION ENGINE USING OXYGENATED AND HYDROCARBON FUELS

2013 ◽  
pp. 7-11
Author(s):  
MUNAWAR NAWAB KARIMI ◽  
SANDEEP KUMAR KAMBOJ
Keyword(s):  
Combustion Engine ◽  
Second Law Of Thermodynamics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Exergy Destruction ◽  
Efficient Utilization ◽  
Dead State ◽  
Energy Economy ◽  
Volume Entropy

The growing concern for energy, economy and environment calls for efficient utilization of natural resources in developing useful work. Second law of thermodynamics provides different perspective compared with first law. This paper provides an overview of the quantitative levels of exergy destruction and chemical irreversibilities during the combustion. For the adiabatic combustion at constant volume, entropy generation approach with second law of thermodynamics is applied. The result of this study is based on a spark ignition, single cylinder combustion engine with stoichiometric condition. Iso-octane, methane, methanol and ethanol are the fuels examined. This study shows that exergy destruction during combustion decreases with the increase in reactant temperature and compression ratios, for all the fuels. Exergy destruction during combustion using entropy balance approach for compression ratio range of 7 to 11 found to vary between 16.18 to 21.52%. Chemical irreversibilities calculated at the restricted dead state are found to be in the range of 2.99 to 3.6% for different fuels

A Turbocharged, Spark-Ignition Engine: Results From an Engine Cycle Simulation Including the Second Law of Thermodynamics

2009 ◽  
Author(s):  
Vaibhav J. Lawand ◽  
Jerald A. Caton
Keyword(s):  
Combustion Process ◽  
Engine Performance ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Base Case ◽  
Mixing Processes ◽  
Automotive Engine ◽  
Cycle Simulation

The use of turbocharging systems for spark-ignition engines has seen increased interest in recent years due to the importance of fuel efficiency, and in some cases, increased performance. An example of a possible strategy is to use a smaller displacement engine with turbocharging rather than a larger engine without turbocharging. To better understand the tradeoffs and the fundamental aspects of a turbocharged engine, this investigation is aimed at determining the energy and exergy quantities for a range of operating conditions for a spark-ignition engine. A 3.8 liter automotive engine with a turbocharger and intercooler was selected for this study. Various engine performance and other output parameters were determined as functions of engine speed and load. For the base case (2000 rpm and a bmep of 1200 kPa), the bsfc was about 240 g/kW-h. At these conditions, the second law analysis indicated that the original fuel exergy was distributed as follows: 34.7% was delivered as indicated work, 16.9% was moved via heat transfer to the cylinder walls, 23.0% exited with the exhaust gases, 20.6% was destroyed during the combustion process, 2.5% was destroyed due to inlet mixing processes, and 1.9% was destroyed due to the exhaust processes. The turbocharger components including the intercooler were responsible for less than 1.0% of the fuel exergy destruction or transfer.

Flow characteristics of misfired gas in the exhaust manifold of a spark ignition engine

2000 ◽  
Vol 214 (4) ◽  
pp. 373-381 ◽  
Author(s):  
Y Chung ◽  
H Kim ◽  
S Choi ◽  
C Bae
Keyword(s):  
Analytical Model ◽  
Oxygen Concentration ◽  
Oxygen Sensor ◽  
Flow Characteristics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Exhaust Manifold ◽  
Cycle Simulation ◽  
Twin Peaks ◽  
Wide Range

Misfiring in spark ignition engines should be avoided, otherwise unburned fuel and oxygen are brought into the catalyst, and subsequent combustion greatly increases the temperature, possibly resulting in immediate damage to the catalyst. As a new concept of misfire detection method, the signal fluctuation of a wide-range oxygen sensor has been introduced to monitor the fluctuation of the oxygen concentration at the exhaust manifold confluence point. The current research aims to develop a tool that is capable of predicting the variation in oxygen concentration at the exhaust manifold confluence point, and to investigate the flow characteristics of the misfired gas in the exhaust manifold under misfiring conditions in a cylinder. The oxygen concentration at the confluence point could be predicted by comparing the gas flowrate from the misfiring cylinder with the total exhaust gas flowrate. The gas flowrates from each of the cylinders were calculated using a one-dimensional engine cycle simulation including a gas dynamic model of the intake and exhaust systems. The variation in oxygen concentration was also determined experimentally using a fast-response hydrocarbon analyser. The trend of the oxygen concentration fluctuation calculated by the analytical model was compared with the experimental results. The analytical model could duplicate the measured trend of the fluctuation of oxygen concentration at the confluence point, which was characterized by twin peaks for one misfiring. The twin peaks are mainly caused by the mixing of the misfired gas with the burned gas from normally operating cylinders. The effects of engine load and speed on the characteristics of the variation in oxygen concentration were also investigated analytically and experimentally.

Illustration of the Use of an Instructional Version of a Thermodynamic Cycle Simulation for a Commercial Automotive Spark-Ignition Engine

2002 ◽  
Vol 30 (4) ◽  
pp. 283-297 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Thermodynamic Cycle ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Adjustment Factor ◽  
Cycle Simulation ◽  
Crank Angle ◽  
Overall Performance ◽  
Specific Heat Capacities ◽  
Model Components

The development and use of an instructional version of a thermodynamic engine cycle simulation for classroom use is described. This simulation is based on well-established features, but which are not necessarily the most advanced. The major simplification of this instructional simulation is the use of constant specific heat capacities as opposed to the use of variable composition and properties. The cycle simulation was developed with an elementary set of conventional sub-model components. To account for the unsteady flow dynamics, an empirical adjustment factor was used. With the exception of this empirical adjustment factor, all of the constants associated with the sub-models are used as suggested by the original publications. Students, therefore, are readily able to develop and use this simulation. This paper then demonstrates the usefulness of such a basic simulation in describing the overall performance of a commercial automotive spark-ignition engine for a range of engine speeds and operating conditions. A modern, four-valve per cylinder, two-camshaft engine was selected for this study. Although the cycle simulation was based on elementary conventional features, a number of important engine characteristics were correctly obtained. These included the overall performance for engine speeds up to 7000 rpm, and details such as the time (crank angle) of peak pressure for optimum performance.

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