“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.).

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.

A comparative study on the first and second law analysis and performance characteristics of a spark ignition engine using either natural gas or gasoline

Fuel ◽  
2015 ◽  
Vol 158 ◽  
pp. 488-493 ◽  
Author(s):  
A. Gharehghani ◽  
R. Hosseini ◽  
M. Mirsalim ◽  
Talal F. Yusaf
Keyword(s):  
Natural Gas ◽  
Comparative Study ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Performance Characteristics ◽  
Second Law ◽  
Second Law Analysis ◽  
And Performance

Characterization of the stability indices of a methanol induced partially premixed diesel dual fuel operation under varying split injection profiles: An experimental endeavour

2021 ◽  
pp. 1-16
Author(s):  
Dipankar Kakati ◽  
Sumit Roy ◽  
Rahul Banerjee
Keyword(s):  
Peak Pressure ◽  
Single Injection ◽  
Pressure Rise ◽  
Dual Fuel ◽  
Maximum Pressure ◽  
Effective Pressure ◽  
Split Injection ◽  
Indicated Mean Effective Pressure ◽  
Rise Rate ◽  
The Stability

Abstract The present investigation attempts to explore the prospects of the engine operational stability of a methanol induced partially premixed dual fuel operation under split injection strategy operating on a conventional single cylinder diesel engine coupled with a dedicated CRDI. The operation of such LTC regimes often deals with the stability concerns which are primarily characterized as the harshness of the operations and the non-repeatability of the combustion cycles. These two markers of operational stability have been mapped in this study through a comprehensive set of metrics of maximum pressure rise rate (ROPRmax) and Coefficient of Variation of Indicated Mean Effective Pressure (COVIMEP), Peak Pressure (COVPP) and Crank Angle of 50% mass fraction burn (COVCA50). The parametric investigation has been carried out at three different injection timings and pilot mass percentages at predefined methanol injection durations. The results have shown tremendous reductions in the non-repeatability of the combustion cycles and the harshness of the engine operation under split injection strategy, indicated by the lower scores of the stability indicators in comparison to the baseline single injection operation. Subsequently, the lowest scores of the maximum pressure rise rate and the Coefficient of Variation of indicated mean effective pressure, peak pressure and CA50 for the entire scope of investigation were registered as 0.62bar/CA, 0.75%, 0.48% and 1%, which were apparently observed as 65.5%, 86.36%, 94% and 53% lower than the corresponding scores registered in the baseline single injection operation.

Response surface method optimization of a natural gas engine with dedicated exhaust gas recirculation

2021 ◽  
pp. 146808742199652
Author(s):  
Chris A Van Roekel ◽  
David T Montgomery ◽  
Jaswinder Singh ◽  
Daniel B Olsen
Keyword(s):  
Natural Gas ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Effective Pressure ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Indicated Mean Effective Pressure ◽  
Surface Method ◽  
Rsm Optimization ◽  
Gas Recirculation

Stoichiometric industrial natural gas engines rely on robust design to achieve consumer driven up-time requirements. Key to this design are exhaust components that are able to withstand high combustion temperatures found in this type of natural gas engine. The issue of exhaust component durability can be addressed by making improvements to materials and coatings or decreasing combustion temperatures. Among natural gas engine technologies shown to reduce combustion temperature, dedicated exhaust gas recirculation (EGR) has limited published research. However, due to the high nominal EGR rate it may be a technology useful for decreasing combustion temperature. In previous work by the author, dedicated EGR was implemented on a Caterpillar G3304 stoichiometric natural gas engine. Examination of combustion statistics showed that, in comparison to a conventional stoichiometric natural gas engine, operating with dedicated EGR requires adjustments to the combustion recipe to achieve acceptable engine operation. This work focuses on modifications to the combustion recipe necessary to improve combustion statistics such as coefficient of variance of indicated mean effective pressure (COV of IMEP), cylinder-cylinder indicated mean effective pressure (IMEP), location of 50% mass fraction burned, and 10%–90% mass fraction burn duration. Several engine operating variables were identified to affect these combustion statistics. A response surface method (RSM) optimization was chosen to find engine operating conditions that would result in improved combustion statistics. A third order factorial RSM optimization was sufficient for finding optimized operating conditions at 3.4 bar brake mean effective pressure (BMEP). The results showed that in an engine with a low turbulence combustion chamber, such as a G3304, optimized combustion statistics resulted from a dedicated cylinder lambda of 0.936, spark timing of 45° before top dead center (°bTDC), spark duration of 365 µs, and intake manifold temperature of 62°C. These operating conditions reduced dedicated cylinder COV of IMEP by 10% (absolute) and the difference between average stoichiometric cylinder and dedicated cylinder IMEP to 0.19 bar.

Smokeless and low NOx combustion in a dual-fuel diesel engine with induced natural gas as the main fuel

2003 ◽  
Vol 4 (1) ◽  
pp. 1-9 ◽  
Author(s):  
H Ogawa ◽  
N Miyamoto ◽  
C Li ◽  
S Nakazawa ◽  
K Akao
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Specific Energy Consumption ◽  
Injection Pressure ◽  
Mixture Composition ◽  
Dual Fuel ◽  
Stoichiometric Ratio ◽  
Compression Ignition Engine ◽  
Pressure System ◽  
Indicated Mean Effective Pressure

In a compression ignition engine, using a rich and lean biform mixture composition that avoids both slightly lean and extremely over-rich regions would be effective in suppressing NOx formation without increasing smoke when the overall air-fuel ratio approaches the stoichiometric ratio. To realize the formation of rich and lean mixtures and the control of ignition timing, a dual-fuel diesel engine with an induced gas with resistance to self-ignition as the main fuel and with a small quantity of diesel fuel for the ignition source has potential merits. However, this method has the problem of knocking and misfiring when the percentage of inducted fuel is increased. In this research smokeless and very low NOx combustion without knocking over a wide operating range was established in a single-cylinder dual-fuel diesel engine with induced natural gas as the main fuel. Optimizations of the combustion chamber shape and operating factors, including exhaust gas recirculation (EGR) and intake air throttling, which determine conditions of the in-cylinder gas, were investigated at several i.m.e.p. (indicated mean effective pressure) conditions. The results of the experiments showed that a combination of the divided cavity, EGR and intake air throttling was effective in simultaneously eliminating knocking and reducing total hydrocarbon (THC) and NOx over a wide i.m.e.p. range. At high i.m.e.p. silent and smooth combustion without knocking was achieved, even with a large amount of induced natural gas. Moreover, the maximum i.m.e.p. increased in comparison with conventional diesel operation with a lower injection pressure system because smoke emission was not a limitation. At medium i.m.e.p. it was effective to adopt EGR and intake air throttling for very low NOx under relatively lower THC. However, at low i.m.e.p. it was difficult to avoid increases in THC and i.s.e.c. (indicated specific energy consumption) while realizing very low NOx and smokeless operation. At lower overall excess air ratio conditions, NOx reduction was shown with a biform mixture composition without slightly lean or extremely rich regions.

Improving Machine Learning Model Performance in Predicting the Indicated Mean Effective Pressure of a Natural Gas Engine

2020 ◽  
Author(s):  
Jinlong Liu ◽  
Christopher Ulishney ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Machine Learning ◽  
Natural Gas ◽  
Decision Trees ◽  
Engine Speed ◽  
Model Performance ◽  
Learning Model ◽  
Operating Conditions ◽  
Effective Pressure ◽  
Indicated Mean Effective Pressure ◽  
Machine Learning Model

Abstract Converting existing compression ignition engines to spark ignition approach is a promising approach to increase the application of natural gas in the heavy-duty transportation sector. However, the diesel-like environment dramatically affects the engine performance and emissions. As a result, experimental tests are needed to investigate the characteristics of such converted engines. A machine learning model based on bagged decision trees algorithm was established in this study to reduce the experimental cost and identify the operating conditions of special interest for analysis. Preliminary engine tests that changed spark timing, mixture equivalence ratio, and engine speed (three key engine operation variables) but maintained intake and boundary conditions were applied as model input to train such a correlative model. The model output was the indicated mean effective pressure, which is an engine parameter generally used to assist in locating high engine efficiency regions at constant engine speed and fuel/air ratio. After training, the correlative model can provide acceptable prediction performance except few outliers. Subsequently, boosting ensemble learning approach was applied in this study to help improve the model performance. Furthermore, the results showed that the boosted decision trees algorithm better described the combustion process inside the cylinder, as least for the operating conditions investigated in this study.

scholarly journals Indicated Mean Effective Pressure Oscillations in a Natural Gas Combustion Engine

2009 ◽  
Vol 64 (5-6) ◽  
pp. 393-398 ◽  
Author(s):  
Grzegorz Litak ◽  
Michał Gęca ◽  
Bao-Feng Yao ◽  
Guo-Xiu Li
Keyword(s):  
Natural Gas ◽  
Combustion Engine ◽  
Combustion Process ◽  
Spark Ignition Engine ◽  
Effective Pressure ◽  
Gas Combustion ◽  
Indicated Mean Effective Pressure ◽  
Natural Gas Combustion ◽  
Measured Pressure ◽  
Lean Conditions

Fluctuations in a combustion process of natural gas in the internal spark ignition engine have been investigated. We measured pressure of the cyclic combustion and expressed its cyclic oscillations in terms of indicated mean effective pressure per cycle. By applying the statistical and multifractal analysis to the corresponding time series we show the considerable changes in engine dynamics for a different equivalence ratio decreases from 0.781 to very lean conditions.

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