Second law analysis of a spark ignition engine under high values of ignition retard

2012 ◽  
Vol 58 (1) ◽  
pp. 79 ◽  
Author(s):  
Hakan Ozcan ◽  
Mustafa Özbey ◽  
M. Sait Söylemez ◽  
Bahattin Topaloglu
Keyword(s):  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Second Law Analysis

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.

Mathematical analysis of spark ignition engine operation via the combination of the first and second laws of thermodynamics

2008 ◽  
Vol 464 (2100) ◽  
pp. 3107-3128 ◽  
Author(s):  
İsmet Sezer ◽  
Atilla Bilgin
Keyword(s):  
Equivalence Ratio ◽  
Engine Speed ◽  
Exergy Analysis ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Operational Parameters ◽  
Engine Operation ◽  
Availability Analysis ◽  
Spark Timing

This study aims at the theoretical exergetic evaluation of spark ignition engine operation. For this purpose, a two-zone quasi-dimensional cycle model was installed, not considering the complex calculation of fluid motions. The cycle simulation consists of compression, combustion and expansion processes. The combustion phase is simulated as a turbulent flame propagation process. Intake and exhaust processes are also computed by a simple approximation method. The results of the model were compared with experimental data to demonstrate the validation of the model. Principles of the second law are applied to the model to perform the exergy (or availability) analysis. In the exergy analysis, the effects of various operational parameters, i.e. fuel–air equivalence ratio, engine speed and spark timing on exergetic terms have been investigated. The results of exergy analysis show that variations of operational parameters examined have considerably affected the exergy transfers, irreversibilities and efficiencies. For instance, an increase in equivalence ratio causes an increase in irreversibilities, while it decreases the first and also the second law efficiencies. The irreversibilities have minimum values for the specified engine speed and optimum spark timing, while the first and second law efficiencies reach a maximum at the same engine speed and optimum spark timing.

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

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