Understanding Loss Mechanisms and Identifying Areas of Improvement for HCCI Engines Using Detailed Exergy Analysis

2012 ◽  
Author(s):  
Samveg Saxena ◽  
Iván Dario Bedoya ◽  
Nihar Shah ◽  
Amol Phadke
Keyword(s):  
Exergy Analysis ◽  
Combustion Process ◽  
Operating Conditions ◽  
Operating Efficiency ◽  
Relative Importance ◽  
Detailed Chemical Kinetics ◽  
Loss Mechanism ◽  
Hcci Engines ◽  
Intake Pressure ◽  
Loss Mechanisms

This paper presents a detailed exergy analysis of homogeneous charge compression ignition (HCCI) engines, including a crank-angle resolved breakdown of mixture exergy and exergy destruction. Exergy analysis is applied to a multi-zone HCCI simulation including detailed chemical kinetics. The HCCI simulation is validated against engine experiments for ethanol-fueled operation. The exergy analysis quantifies the relative importance of different loss mechanisms within HCCI engines over a range of engine operating conditions. Specifically, four loss mechanisms are studied for their relative impact on exergy losses, including 1) the irreversible combustion process (16.4–21.5%), 2) physical exergy lost to exhaust gases (12.0–18.7%), 3) heat losses (3.9–17.1%), and 4) chemical exergy lost to incomplete combustion (4.7–37.8%). The trends in each loss mechanism are studied in relation to changes in intake pressure, equivalence ratio, and engine speed as these parameters are directly used to vary engine power output. This exergy analysis methodology is proposed as a tool to inform research and design processes, particularly by identifying the relative importance of each loss mechanism in determining engine operating efficiency.

Understanding Loss Mechanisms and Identifying Areas of Improvement for HCCI Engines Using Detailed Exergy Analysis

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Samveg Saxena ◽  
Iván Dario Bedoya ◽  
Nihar Shah ◽  
Amol Phadke
Keyword(s):  
Exergy Analysis ◽  
Combustion Process ◽  
Operating Conditions ◽  
Operating Efficiency ◽  
Relative Importance ◽  
Detailed Chemical Kinetics ◽  
Loss Mechanism ◽  
Hcci Engines ◽  
Intake Pressure ◽  
Loss Mechanisms

This paper presents a detailed exergy analysis of homogeneous charge compression ignition (HCCI) engines, including a crank-angle resolved breakdown of mixture exergy and exergy destruction. Exergy analysis is applied to a multizone HCCI simulation including detailed chemical kinetics. The HCCI simulation is validated against engine experiments for ethanol-fueled operation. The exergy analysis quantifies the relative importance of different loss mechanisms within HCCI engines over a range of engine operating conditions. Specifically, four loss mechanisms are studied for their relative impact on exergy losses, including (1) the irreversible combustion process (16.4%–21.5%), (2) physical exergy lost to exhaust gases (12.0%–18.7%), (3) heat losses (3.9%–17.1%), and (4) chemical exergy lost to incomplete combustion (4.7%–37.8%). The trends in each loss mechanism are studied in relation to changes in intake pressure, equivalence ratio, and engine speed as these parameters are directly used to vary engine power output. This exergy analysis methodology is proposed as a tool to inform research and design processes, particularly by identifying the relative importance of each loss mechanism in determining engine operating efficiency.

The Effects of Intake Flow Swirl on the Combustion Characteristics of Hydrogen Fueled HCCI Engines

2004 ◽  
Author(s):  
Chengke Liu ◽  
Ghazi A. Karim
Keyword(s):  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Swirl Ratio ◽  
Detailed Chemical Kinetics ◽  
Initial Flow ◽  
Flow Swirl ◽  
Combustion Duration ◽  
Hcci Engines ◽  
Intake Flow

This paper describes the effects of the initial intake flow swirl on the combustion process of hydrogen-air homogeneous mixtures in HCCI engines. CFD KIVA3 code incorporated with detailed chemical kinetics was employed. The effects on the development and extent of non-uniformities in velocity, pressure, and temperature within the cylinder charge were investigated. Moreover, the effects of the initial flow swirl ratio values on the onset of autoignition and its timing, combustion duration, NOx emissions, and the onset of knock were evaluated. It is shown that an increase in the initial flow swirl ratio or speed lengthens the delay period for autoignition and extends the combustion period while reducing NOx emissions. There are optimum values of the initial swirl ratio and engine speed for a certain set of engine operating conditions that can achieve high thermal efficiencies and low NOx emissions while reducing the tendency to knock.

The Relative Importance of Radicals on the N2O and NO Formation and Destruction Paths in a Quartz CFBC

1999 ◽  
Vol 121 (2) ◽  
pp. 131-136 ◽  
Author(s):  
F. Winter ◽  
C. Wartha ◽  
H. Hofbouer
Keyword(s):  
Circulating Fluidized Bed ◽  
Combustion Process ◽  
Operating Conditions ◽  
Fuel Particle ◽  
Relative Importance ◽  
No Formation ◽  
Bed Temperature ◽  
Wide Range ◽  
Ft Ir ◽  
Concentration Changes

In a laboratory-scale circulating fluidized bed combustor (CFBC), which mainly consists of quartz-glass, the relative importance of the radicals, generated by the combustion process, on the N2O and NO formation and destruction paths are studied. The CFBC unit is electrically heated and operating conditions can be nearly independently changed over a wide range; e.g., the bed temperature was varied between 700 and 900°C. The radicals’ importance on the destruction reactions of N2O has been investigated under CFBC conditions by a recently developed iodine-addition technique to suppress the radical concentrations. Additionally, CO, CH4 and H2O have been added to study their influence and to change the pool of radicals. Time-resolved concentration changes at the top of the riser have been measured by using a high-performance FT-IR spectrometer in combination with a low-volume, long-path gas cell. The FT-IR analysis is focused on the carbon-containing species, viz., CO2 CO, CH4 NO2 and other hydrocarbons, as well as on the nitrogen-containing species, viz., NO, NO2, N2O, and HCN. In the continuous combustion tests, petroleum coke has been burned in the CFBC. Concentration profiles and concentration changes at the top of the riser have been measured. Iodine has been added and the bed temperature and the initial fuel particle size are varied. With the knowledge of the N2O destruction reactions, the relative importance of the radicals on N2O and NO formation reactions has been identified and is discussed.

scholarly journals An Analytical Model of Homogeneous Charge Compression Ignition Engine for Performance Prediction

2014 ◽  
Vol 564 ◽  
pp. 8-12
Author(s):  
A. R. Najihah ◽  
A.A. Nuraini ◽  
Othman Inayatullah
Keyword(s):  
Fuel Consumption ◽  
Engine Speed ◽  
Model Simulation ◽  
Combustion Process ◽  
Operating Conditions ◽  
Compression Ignition Engine ◽  
Combustion Duration ◽  
Wide Range ◽  
Intake Pressure ◽  
And Performance

A zero dimensional thermodynamic model simulation is developed to simulate the combustion characteristics and performance of a four stroke homogeneous compression combustion ignition (HCCI) engine fueled with gasoline. This model which applies the first law of thermodynamics for a closed system is inclusive of empirical model for predicting the important parameters for engine cycles: the combustion timing and mass burnt fraction during the combustion process. The hypothesis is the increasing intake temperature can reduce the combustion duration and the fuel consumption at wide range of equivalence ratio. The intake temperature were increased from 373-433 K with increment of 20 K. The engine was operated over a range of equivalence ratios of 0.2 to 0.5 at constant engine speed of 1200 rpm and intake pressure of 89,950 k Pa. Simulations were performed using Simulink® under different engine operating conditions. Increasing intake temperature allows reducing the combustion duration by 0.99 °CA and 0.26 °CA at equivalence ratios of 0.2 and 0.5, respectively. The brake specific fuel consumption decreases about 6.09%-5.76% at 0.2-0.5 of equivalence ratios. Thus, fuel consumption can be reduced by increasing intake temperature.

Use of Detailed Chemical Kinetics to Study HCCI Engine Combustion With Consideration of Turbulent Mixing Effects

2002 ◽  
Vol 124 (3) ◽  
pp. 702-707 ◽  
Author(s):  
S.-C. Kong ◽  
R. D. Reitz
Keyword(s):  
Chemical Kinetics ◽  
Turbulent Mixing ◽  
Combustion Process ◽  
Reaction Rates ◽  
Detailed Chemical Kinetics ◽  
Wide Range ◽  
Hcci Engines ◽  
Heavy Duty Diesel ◽  
Flame Chemistry ◽  
Detailed Chemical

Detailed chemical kinetics was used in an engine CFD code to study the combustion process in HCCI engines. The CHEMKIN code was implemented in KIVA such that the chemistry and flow solutions were coupled. The reaction mechanism consists of hundreds of reactions and species and is derived from fundamental flame chemistry. Effects of turbulent mixing on the reaction rates were also considered. The results show that the present KIVA/CHEMKIN model is able to simulate the ignition and combustion process in three different HCCI engines including a CFR engine and two modified heavy-duty diesel engines. Ignition timings were predicted correctly over a wide range of engine conditions without the need to adjust any kinetic constants. However, it was found that the use of chemical kinetics alone was not sufficient to accurately simulate the overall combustion rate. The effects of turbulent mixing on the reaction rates need to be considered to correctly simulate the combustion and heat release rates.

Modeling Direct-Injection Gasoline HCCI Combustion Using Detailed Chemistry and CFD

2001 ◽  
Author(s):  
Song-Charng Kong ◽  
Rolf D. Reitz
Keyword(s):  
Turbulent Mixing ◽  
Direct Injection ◽  
Combustion Process ◽  
Reaction Rates ◽  
Injection Timing ◽  
Detailed Chemical Kinetics ◽  
Detailed Chemistry ◽  
Hcci Combustion ◽  
Wide Range ◽  
Hcci Engines

Abstract Detailed chemical kinetics was implemented into an engine CFD code to study the combustion process in Homogeneous Charge Compression Ignition (HCCI) engines. The CHEMKIN code was implemented into KIVA-3V such that the chemistry and flow solutions were coupled. Effects of turbulent mixing on the reaction rates were also considered. The model was validated using experimental data from a direct-injection Caterpillar engine operated in the HCCI mode using gasoline. The results show that good levels of agreement were obtained using the present KIVA/CHEMKIN model for a wide range of engine conditions including various injection timings, engine speeds, and loads. It was found that the effects of turbulent mixing on the reaction rates needed to be considered to correctly simulate the combustion phasing. It was also found that the presence of residual radicals could enhance the mixture reactivity and hence shorten the ignition delay time. The NOx emissions were found to increase as the injection timing was retarded, in agreement with experimental results.

scholarly journals Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Alberto Palma ◽  
Javier Mauricio Loaiza ◽  
Manuel J. Díaz ◽  
Juan Carlos García ◽  
Inmaculada Giráldez ◽  
...  
Keyword(s):  
Activation Energy ◽  
Acid Hydrolysis ◽  
Energy Production ◽  
Combustion Process ◽  
Operating Conditions ◽  
Raw Material ◽  
Energy Of Combustion ◽  
Increasing Temperature ◽  
Hydrolysis Of ◽  
Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

scholarly journals Exergy analysis of a biomass-based multi-energy system

2019 ◽  
Vol 113 ◽  
pp. 02017
Author(s):  
Mariagiovanna Minutillo ◽  
Alessandra Perna ◽  
Alessandro Sorce
Keyword(s):  
Exergy Analysis ◽  
Energy System ◽  
H2 Production ◽  
Operating Conditions ◽  
Processing Unit ◽  
Storage Unit ◽  
Fuel Processing ◽  
Fuel Processor ◽  
Energy Processes ◽  
And Storage

This paper focuses on a biofuel-based Multi-Energy System generating electricity, heat and hydrogen. The proposed system, that is conceived as refit option for an existing anaerobic digester plant in which the biomass is converted to biogas, consists of: i) a fuel processing unit, ii) a power production unit based on the SOFC (Solid Oxide Fuel Cell) technology, iii) a hydrogen separation, compression and storage unit. The aim of this study is to define the operating conditions that allow optimizing the plant performances by applying the exergy analysis that is an appropriate technique to assess and rank the irreversibility sources in energy processes. Thus, the exergy analysis has been performed for both the overall plant and main plant components and the main contributors to the overall losses have been evaluated. Moreover, the first principle efficiency and the second principle efficiency have been estimated. Results have highlighted that the fuel processor (the Auto-Thermal Reforming reactor) is the main contributor to the global exergy destruction (9.74% of the input biogas exergy). In terms of overall system performance the plant has an exergetic efficiency of 53.1% (it is equal to 37.7% for the H2 production).

Study on Characteristics of the Linear Air-Conditioner Compressor at Varied Operating Conditions

2011 ◽  
Vol 201-203 ◽  
pp. 632-636 ◽  
Author(s):  
Jie Fei Xie ◽  
Xin Hua Li ◽  
Hong Zhang
Keyword(s):  
Engineering Application ◽  
Axial Direction ◽  
Operating Conditions ◽  
Air Conditioner ◽  
Design Development ◽  
Runge Kutta Method ◽  
Moving Body ◽  
Cylinder Piston ◽  
Compressor Performance ◽  
Intake Pressure

This paper mainly introduces a novel linear air conditioner compressor which is driven by the linear oscillatory motor with two divided moving body, of which the Cylinder-piston assembly presents symmetrical distribution along the axial direction. The compressor dynamics equations were built and solved numerically with the fourth order Runge-Kutta method. in the meantime, this paper emphatically analyzes the influence of those factors, such as the intake pressure, the exhaust pressure, the suction gas superheat, the cooling degree, on the compressor performance at varied operating conditions. These works shows that improving the suction gas pressure and reducing the exhuast pressure can help to increase the refrigeration capacity and energy efficiency ratio of the air conditioner compressor. Those analysis results provide theory foundation for design,development, and engineering application of this linear air-conditioner compressor.

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