Thermodynamic Performance Optimization of Reciprocating Internal Combustion (IC) Engines

2008 ◽  
Author(s):  
George A. Adebiyi ◽  
Kalyan K. Srinivasan ◽  
Charles M. Gibson
Keyword(s):  
Performance Optimization ◽  
Combustion Process ◽  
Design Parameters ◽  
Second Law ◽  
Ic Engine ◽  
Thermodynamic Performance ◽  
Second Law Analysis ◽  
Compression And Expansion ◽  
Dual Cycle ◽  
Ic Engines

Reciprocating IC engines are traditionally modeled as operating on air standard cycles that approximate indicator diagrams obtained in experiments on real engines. These indicator diagrams can best be approximated by the dual cycle for both gasoline and diesel engines. Analysis of air standard cycles unfortunately fails to capture second law effects such as exergy destruction due to the irreversibility of combustion. Indeed, a complete thermodynamic study of any process requires application of both the first and second laws of thermodynamics. This article gives a combined first and second law analysis of reciprocating IC engines in general with optimization of performance as primary goal. A practical dual-like cycle is assumed for the operation of a typical reciprocating IC engine and process efficiencies are assigned to allow for irreversibilities in the compression and expansion processes. The combustion process is modeled instead of being replaced simply by a heat input process to air as is common in air standard cycle analysis. The study shows that performance of the engine can indeed be optimized on the basis of geometrical design parameters such as the compression ratio as well as the air-fuel ratio used for the combustion.

“Lost Available IMEP”: A Second-Law-Based Performance Parameter for IC Engines

2016 ◽  
Author(s):  
H. Mahabadipour ◽  
K. K. Srinivasan ◽  
S. R. Krishnan
Keyword(s):  
Natural Gas ◽  
Performance Parameter ◽  
Second Law ◽  
Dual Fuel ◽  
Effective Pressure ◽  
Closed Cycle ◽  
Indicated Mean Effective Pressure ◽  
Second Law Analysis ◽  
Ic Engines ◽  
Engine Size

The second law of thermodynamics is a powerful tool for investigating thermodynamic irreversibilities and to identify pathways for improving efficiencies of energy systems, including IC engines. In the present work, second law analysis is applied to quantify irreversibilities in diesel-ignited natural gas dual fuel low temperature combustion (LTC), which utilizes diesel to ignite natural gas to simultaneously reduce emissions of oxides of nitrogen and particulate matter. A previously validated multi zone thermodynamic model of dual fuel LTC was used as the basic framework to perform the second law analysis. The multi-zone model, which simulates closed cycle processes between intake valve closure (IVC) and exhaust valve opening (EVO), divides the cylinder contents into four main zones: (i) an unburned zone containing a premixed natural gas-air mixture, (ii) a pilot fuel zone (or “packets”) containing diesel vapor and entrained natural gas-air mixture, (iii) a flame zone, and (iv) a burned zone. By applying the second law systematically to each zone, the total entropy generated over the closed cycle (Sgen) and the lost available work (Wlost = T0*Sgen) were quantified. Subsequently, the lost available work was divided by the displaced volume to calculate a new engine performance parameter labeled “lost available indicated mean effective pressure” (LAIMEP). Proceeding analogously from the definition of indicated mean effective pressure (IMEP) as an engine-size-normalized measure of indicated work, the LAIMEP may be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities. Since LAIMEP is independent of engine size, it can be used to compare thermodynamic irreversibilities between engines of various displaced volumes as well as between different engine combustion strategies. Two additional second-law-based parameters: fuel conversion irreversibility (FCI) as the ratio of Wlost to total fuel chemical energy input and normalized LAIMEP as the ratio of LAIMEP to IMEP, were also defined. Parametric studies were performed at different diesel injection timings (SOI ∼ 300–340 CAD), intake temperatures (Tin ∼ 50°–150°C), and intake boost pressures (Pin ∼ 1–2.4 bar) to characterize their impact on LAIMEP and FCI. It was determined that both LAIMEP and FCI increased with SOI advancement (from 340 to 300 CAD) and decreased with increasing Tin and Pin. These trends were explained using predicted combustion parameters, especially burned mass fraction and average in-cylinder temperature at EVO. While the present work focused on diesel-natural gas dual fuel LTC (as an example), the overall methodology adopted for the second law analysis as well as the conceptual definitions of LAIMEP, FCI, etc., are generally applicable to any IC engine operating on any combustion strategy (e.g., SI, CI, LTC, etc.).

scholarly journals The numerical thermodynamic analysis of Otto-Miller Cycle (OMC)

2016 ◽  
Vol 20 (1) ◽  
pp. 363-369 ◽  
Author(s):  
Mehmet Cakir
Keyword(s):  
Heat Transfer ◽  
Thermodynamic Analysis ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Miller Cycle ◽  
Dimensionless Form ◽  
Engine Design ◽  
Thermodynamic Performance ◽  
Compression And Expansion ◽  
Heat Transfer Effects

This paper presents a thermodynamic analysis for an irreversible Otto-Miller Cycle (OMC) by taking into consideration heat transfer effects and internal irreversibilities resulting from compression and expansion processes. In the analyses, the influences of the miller cycle ratio, combustion and heat loss constants and inlet temperature have been investigated relations with efficiency in dimensionless form. The dimensionless power output and power density and thermal efficiency relations have been computationally obtained versus the engine design parameters with respect to combustion and heat transfer constants. The results demonstrate that the heat transfer and combustion constants have considerable effects on the cycle thermodynamic performance. This situation theoretically verified for OMC.

Numerical investigation for second law analysis of ferrofluid inside a porous semi annulus

2019 ◽  
Vol 29 (3) ◽  
pp. 1079-1102 ◽  
Author(s):  
M. Sheikholeslami ◽  
R. Ellahi ◽  
Ahmad Shafee ◽  
Zhixiong Li
Keyword(s):  
Hartmann Number ◽  
Control Volume ◽  
Combustion Process ◽  
Exergy Loss ◽  
Second Law ◽  
Bejan Number ◽  
Porous Space ◽  
Content Type ◽  
Proposed Model ◽  
Second Law Analysis

PurposeThe purpose of this paper is to present the entropy analysis of ferrofluid inside a porous space with magnetic force. Homogenous model with second law analysis is also taken into account.Design/methodology/approachInnovative model has been proposed and designed using control volume finite element method.FindingsExperimental results demonstrate that Bejan number augments with augment of Rayleigh. As Hartmann number rises, exergy loss enhances. Exergy loss increases by increasing Hartmann number, whereas magnetic entropy generation reduces with the decrease of Ha. The proposed model can be used for combustion process and optimizing the performance of energy conversion system like gas turbine.Originality/valueTo the best of authors’ knowledge, this model is reported for the first time.

Thermodynamic Performance Assessment of Gas Turbine Trigeneration System for Combined Heat Cold and Power Production

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Abdul Khaliq ◽  
Rajesh Kumar
Keyword(s):  
Gas Turbine ◽  
Thermal Energy ◽  
Pressure Ratio ◽  
Energy Ratio ◽  
Second Law ◽  
Exergy Destruction ◽  
Thermodynamic Performance ◽  
Second Law Analysis ◽  
Process Heat ◽  
Gas Turbine Cycle

The thermodynamic performance of the combustion gas turbine trigeneration system has been studied based on first law as well as second law analysis. The effects of overall pressure ratio and process heat pressure on fuel utilization efficiency, electrical to thermal energy ratio, second law efficiency, and exergy destruction in each component are examined. Results for gas turbine cycle, cogeneration cycle, and trigeneration cycle are compared. Thermodynamic analysis indicates that maximum exergy is destroyed during the combustion and steam generation process, which represents over 80% of the total exergy destruction in the overall system. The first law efficiency, electrical to thermal energy ratio, and second law efficiency of trigeneration system, cogeneration system, and gas turbine cycle significantly varies with the change in overall pressure ratio but the change in process heat pressure shows small variations in these parameters. Results clearly show that performance evaluation of the trigeneration system based on first law analysis alone is not adequate and hence more meaningful evaluation must include second law analysis.

Second-Law Analysis of Diesel Engine Combustion

1990 ◽  
Vol 112 (1) ◽  
pp. 129-137 ◽  
Author(s):  
J. H. Van Gerpen ◽  
H. N. Shapiro
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Combustion Process ◽  
Second Law ◽  
Zone Model ◽  
System Availability ◽  
Second Law Analysis ◽  
Correct Determination ◽  
Chemical Availability ◽  
First Time

A second-law analysis of the combustion process in a diesel engine is presented for a single-zone model. Expressions for availability and the availability balance are developed in detail from the energy and entropy balances and applied in a manner that allows the irreversibility due to combustion to be separated from that associated with heat transfer to the walls. Availability is divided into two components: thermomechanical and chemical availability. For the first time, chemical availability of the cylinder contents is dealt with rigorously, which allows for a correct determination of combustion irreversibilities. The analysis is applied in a parametric study of the effects of combustion timing, mass burning rate, and heat transfer rate on the irreversibility and system availability.

scholarly journals Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 419
Author(s):  
Congzheng Qi ◽  
Zemin Ding ◽  
Lingen Chen ◽  
Yanlin Ge ◽  
Huijun Feng
Keyword(s):  
Power Output ◽  
Performance Optimization ◽  
External Load ◽  
Thermal Contact ◽  
Heat Engine ◽  
Design Parameters ◽  
Load Effect ◽  
Heat Engines ◽  
Heat Leakage ◽  
Steady Current

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.

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