Development of a Highly Reduced Mechanism for Iso-Octane HCCI Combustion With Targeted Search Algorithm

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Y. F. Tham ◽  
F. Bisetti ◽  
J.-Y. Chen
Keyword(s):  
Numerical Simulations ◽  
Chemical Kinetics ◽  
Search Algorithm ◽  
Compression Ignition ◽  
New Approach ◽  
Reduced Mechanism ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Start Of Combustion ◽  
Skeletal Mechanism

This paper describes recent development of iso-octane skeletal and reduced mechanisms for speeding up numerical simulations of homogeneous charge compression ignition (HCCI) engines. A novel targeted search algorithm is developed to systematically screen species for quasisteady state (QSS) assumption in order to reduce the mechanism size while maintaining accuracy. This new approach is especially found useful when the chemical kinetics involve complex ignition pathways. Using the iso-octane mechanism developed by LLNL, a skeletal mechanism with 215 species (Skeletal-215) and a reduced mechanism with 63 non-QSS species (Reduced-63) were constructed. Evaluations of the performances of the Skeletal-215 and the Reduced-63 were extensively conducted for the operation regimes in HCCI engine applications. Both mechanisms are found satisfactory in predicting start of combustion and minor emission species.

Validation of a Newly Developed n-Heptane Reduced Chemistry and Its Application to Simulations of Ignition Quality Tester, Diesel, and HCCI Combustion

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Hsin-Luen Tsai ◽  
J.-Y. Chen ◽  
Gregory T. Chin
Keyword(s):  
Gas Turbines ◽  
Three Dimensional ◽  
Compression Ignition ◽  
Cfd Simulations ◽  
Reduced Mechanism ◽  
Hcci Combustion ◽  
Reduced Chemistry ◽  
Ignition Quality ◽  
Ignition Quality Tester ◽  
Skeletal Mechanism

A skeletal mechanism (144 species) and a corresponding reduced mechanism (62 species) were developed on the basis of the most recent detailed n-heptane mechanism by Lawrence Livermore National Laboratories (LLNL, version 3.1, 2012) (Mehl et al., 2011, “Kinetic Modeling of Gasoline Surrogate Components and Mixtures Under Engine Conditions,” Proc. Combust. Inst., 33, pp. 193–200), in order to assess the mechanism's performance under various practical combustion conditions. These simplified mechanisms were constructed and validated under shock tube conditions. Three-dimensional computational fluid dynamics (3D CFD) simulations with both simplified mechanisms were conducted for the following modeling applications: ignition quality tester (IQT), diesel engine, and homogeneous charge compression ignition (HCCI) engine. In comparison with experimental data, the simulation results were found satisfactory under the diesel condition but inaccurate for both the IQT and HCCI conditions. For HCCI, the intake temperature used in the simulation had to be increased 30 K in order to be consistent with the engine data provided by Guo et al. (2010, “An Experimental and Modeling Study of HCCI Combustion Using n-Heptane,” ASME J. Eng. Gas Turbines Power, 132(2), 022801). Exploration of possible causes is conducted leading to the conclusion that refinement in the mechanism is needed for accurate prediction of combustion under IQT and HCCI conditions.

A Stochastic Simulation of an HCCI Engine Using an Automatically Reduced Mechanism

2001 ◽  
Author(s):  
Hakan Serhad Soyhan ◽  
Terese Løvås ◽  
Fabian Mauss
Keyword(s):  
Flow Reactor ◽  
Plug Flow ◽  
High Sensitivity ◽  
Ignition Process ◽  
Compression Ignition ◽  
Detailed Chemical Kinetics ◽  
Promising Alternative ◽  
Hcci Engine ◽  
Reduced Mechanism ◽  
Skeletal Mechanism

Abstract Homogeneous Charge Compression Ignition (HCCI) Engines are a promising alternative to the existing Spark Ignition Engines and Compression Ignition Engines. In an HCCI engine, the premixed fuel/air mixture ignites when sufficiently high temperature and pressure is reached. The entire bulk will auto-ignite at almost the same time because the physical conditions are similar throughout the combustion chamber. Therefore it is a justified assumption to consider the chemical reactions to be the rate-determining step for the ignition process. This gives us the opportunity to formulate a simple zero-dimensional model with detailed chemical kinetics for the calculations of the ignition process. Ignition calculations using this model have predicted a high sensitivity to fluctuations in temperature and fuel compositions. These predictions have later been confirmed by experiments. Partially stirred plug flow reactor (PaSPFR) can be used to conquer the assumption of homogeneity. The assumption is replaced by that of statistical homogeneity and thus statistical fluctuations caused by inhomogeneities can be studied. However, the CPU-time needed for this approach is increased considerably and the usage of mechanism reduction becomes evident. In this paper, we demonstrate how a reduced mechanism for natural gas as fuel is derived automatically. The original mechanism by Warnatz (589 reactions, 53 species) is first reduced to a skeletal mechanism (481 reactions, 43 species). By introduction of the quasi steady state assumption, the skeletal mechanism is reduced further to 23 species and 20 global reactions. The accuracy of the final mechanism is demonstrated using the stochastic reactor tool for an HCCI engine.

The effect of fuel octane and dilutent on homogeneous charge compression ignition combustion

2005 ◽  
Vol 219 (5) ◽  
pp. 665-675 ◽  
Author(s):  
M J Atkins ◽  
C R Koch
Keyword(s):  
Fuel Consumption ◽  
Octane Number ◽  
Homogeneous Charge Compression Ignition ◽  
Specific Fuel Consumption ◽  
Compression Ignition ◽  
Hcci Combustion ◽  
Excess Air ◽  
Combustion Properties ◽  
Start Of Combustion ◽  
Homogeneous Charge

This paper presents some experimental operating and combustion properties of homogeneous charge compression ignition (HCCI) combustion. HCCI operating range, start of combustion, burn duration, indicated mean effective pressure, indicated specific emissions, and indicated specific fuel consumption are evaluated as charge dilution and octane number are varied. Primary reference fuels with octane numbers of 20, 40, and 60 are used in this study. The autoignition properties of the air-fuel mixture are varied by changing the fuel octane number, percentage of exhaust gas recirculation (EGR), and air-fuel ratio, while holding the intake temperature, engine speed, and compression ratio constant. Results show that both the start of combustion and the burn duration are sensitive to mixture dilution (excess air or EGR). The fuel octane number is not an effective method of controlling the start of combustion or the burn duration but can be used to increase the load range of the HCCI engine. Both the NO x emissions and the indicated specific fuel consumption increase as the octane number is increased due to lower dilution and higher peak temperatures. Correct amounts of dilution are critical in controlling HCCI combustion. Separating dilution into EGR and excess air, it is found that a given amount of EGR is more effective at controlling the start of combustion and the burn duration than the same amount of excess air.

Effects of Fuel Octane Number on Homogeneous Charge Compression Ignition (HCCI) Combustion with Rapid Compression Machine

2012 ◽  
Vol 455-456 ◽  
pp. 339-343
Author(s):  
You Kun Wang ◽  
Peng Cheng ◽  
Yun Kai Wang ◽  
Hua Li ◽  
Ying Nan Guo
Keyword(s):  
Octane Number ◽  
Homogeneous Charge Compression Ignition ◽  
Maximum Pressure ◽  
Compression Ignition ◽  
Rapid Compression Machine ◽  
Hcci Combustion ◽  
Combustion Duration ◽  
Rapid Compression ◽  
Start Of Combustion ◽  
Homogeneous Charge

The effects of fuel octane number (RON) on homogeneous charge compression ignition (HCCI) combustion were studied under different combustion boundary conditions on a rapid compression machine. The results show that the maximum pressure raise rate and maximum combustion temperature decreased as the RON increased while the start of combustion is delayed and the combustion duration is shortened at the same time.

Experimental and numerical investigation of effect of fuel on ion sensor signal to determine combustion timing in homogeneous charge compression ignition engines

2005 ◽  
Vol 6 (5) ◽  
pp. 465-474 ◽  
Author(s):  
P Mehresh ◽  
D Flowers ◽  
R W Dibble
Keyword(s):  
High Efficiency ◽  
Homogeneous Charge Compression Ignition ◽  
Combustion Process ◽  
Ion Concentration ◽  
Compression Ignition ◽  
Ion Sensors ◽  
Pressure Transducers ◽  
Hcci Engines ◽  
Start Of Combustion ◽  
Homogeneous Charge

Homogeneous charge compression ignition (HCCI) engines offer promise owing to low emissions and high efficiency. However, the control of the combustion process in HCCI engines, specifically the control of the start of combustion (SOC) or ignition timing, remains a challenge. Piezoelectric pressure transducers are used in research engines for determination of the start of combustion; however, these pressure transducers are too expensive and fragile for applications in commercial engines. Recent work by the authors as well as other investigators has shown the potential of inexpensive ion sensors in HCCI engines fuelled with propane or gasoline. However, the working range of ion sensors is limited in HCCI engines owing, in large part, to the fact that the peak cycle temperature in HCCI combustion is quite low (∼ 1700–1900 K). With the guidance of detailed chemical kinetic modelling it is shown that fuels or additives producing a higher concentration of CH radicals will probably produce higher ion concentrations. Acetylene (HC=CH) is known to produce large concentrations of CH radicals. Hence, various mixtures of propane and acetylene are numerically and experimentally studied. The ion concentration substantially increases with the addition of a small amount of acetylene. This research is an effort to understand the ion generation mechanism in HCCI engines with a view towards improving the ion signal.

A Control-Oriented Two Zone Thermo-Kinetic Model of a Single Cylinder HCCI Engine

2008 ◽  
Author(s):  
Varun Tandra ◽  
Nilabh Srivastava
Keyword(s):  
Kinetic Model ◽  
Compression Ignition Engine ◽  
Control Laws ◽  
Combustion Dynamics ◽  
Single Cylinder ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Homogeneous Composition ◽  
Start Of Combustion

Over the past two decades, homogeneous charge compression ignition engine technology (HCCI) has aroused a great deal of interest in the automotive sector owing to its ability to generate ultra-low exhaust emissions and to be fuel-flexible. The current work proposes a control-oriented two-zone thermo-kinetic model of such a single cylinder HCCI engine. Earlier control laws were derived by using single zone mathematical models of HCCI combustion; however, these models fail to accurately capture the combustion dynamics of an HCCI engine owing to the assumption of homogeneous composition and temperature in the cylinder. Certain multi-zone models of HCCI engines emphasizing the shortcomings of these single zone models have also been reported in literature. However, such models are far too complex and unwieldy for the development of fast and efficient controllers for HCCI engines. The present work outlines the modeling approach of a single-cylinder two-zone HCCI engine by incorporating the first law of thermodynamics and the temperature and concentration inhomogeneities. The results showed good conformity to those obtained from literature-based multi-zone models. A comparative analysis between the single zone and two-zone models, in the context of predicting cylinder pressures, exhaust gas temperatures, emission concentrations, and start of combustion (SOC), is also discussed.

scholarly journals Performance and Emission Parameters of Homogeneous Charge Compression Ignition (HCCI) Engine: A Review

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3557 ◽  
Author(s):  
M. Mofijur ◽  
M.M. Hasan ◽  
T.M.I. Mahlia ◽  
S.M. Ashrafur Rahman ◽  
A.S. Silitonga ◽  
...  
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Engine Performance ◽  
Spark Ignition ◽  
Emission Characteristics ◽  
Compression Ignition ◽  
Combustion Mode ◽  
Performance And Emission ◽  
Hcci Combustion ◽  
Hcci Engines ◽  
Homogeneous Charge

Strict emission regulations and demand for better fuel economy are driving forces for finding advanced engines that will be able to replace the conventional internal combustion engines in the near future. Homogeneous charge compression ignition (HCCI) engines use a different combustion technique; there are no spark plugs or injectors to assist the combustion. Instead, when the mixtures reach chemical activation energy, combustion auto-ignites in multiple spots. The main objective of this review paper is to study the engine performance and emission characteristics of HCCI engines operating in various conditions. Additionally, the impact of different fuels and additives on HCCI engine performance is also evaluated. The study also introduces a potential guideline to improve engine performance and emission characteristics. Compared to conventional compression ignition and spark ignition combustion methods, the HCCI combustion mode is noticeably faster and also provides better thermal efficiency. Although a wide range of fuels including alternative and renewable fuels can be used in the HCCI mode, there are some limitation/challenges, such as combustion limited operating range, phase control, high level of noise, cold start, preparation of homogeneous charge, etc. In conclusion, the HCCI combustion mode can be achieved in existing spark ignition (SI) engines with minor adjustments, and it results in lower oxides of nitrogen (NOx) and soot emissions, with practically a similar performance as that of SI combustion. Further improvements are required to permit extensive use of the HCCI mode in future.

A Stand-Alone Multi-Zone Model for Combustion in HCCI Engines

2005 ◽  
Author(s):  
Paitoon Kongsereeparp ◽  
Behzad Kashani ◽  
M. David Checkel
Keyword(s):  
Equivalence Ratio ◽  
Homogeneous Charge Compression Ignition ◽  
Residual Fraction ◽  
Zone Model ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Operating Variables ◽  
Hcci Combustion ◽  
Combustion Duration ◽  
Hcci Engines

Because they have the potential for ultra low NOx emissions and high efficiency, Homogeneous Charge Compression Ignition (HCCI) engines have the potential to develop a significant niche. However, a narrow operating range, (bracketed by severe knock and misfire problems), presents a formidable obstacle to developing usable HCCI combustion systems. HCCI combustion is influenced by a complex array of operating variables including fuel octane quality, intake preheating temperature, compression ratio, equivalence ratio, exhaust gas recirculation and engine component temperature. These variables affect the two critical combustion parameters: ignition timing and combustion duration. If these two parameters can be controlled by appropriate settings of the operating variables, a good HCCI combustion scheme could be achieved. Therefore, the theoretical prediction of these two combustion parameters as a function of the key operating variables is necessary for development of HCCI combustion. This paper describes a stand-alone, single-zone and multi-zone combustion model which have been developed for the specific purpose of investigating HCCI combustion control. In the multi-zone model, temperature and composition in each zone were adjusted in order to study the effect of in-homogeneity which is critical to understanding ignition timing and combustion duration in real HCCI engines. The models simulated HCCI combustion using two fuels: hydrogen, (11 species, 23 reactions- from CHEMKIN library), and natural gas, (53 species, 325 reactions- from GRI mech). The capabilities of the two models to predict ignition timing, combustion duration and peak pressure were verified against experimental and simulation results of Fiveland et al [2, 11]. The models were then used to study the effect of different in-homogeneity levels of equivalence ratio, intake temperature and residual fraction. The single zone model could only predict ignition timing while the multi-zone model shows the capability to mimic realistic HCCI combustion phenomena. The study showed that some degree of in-homogeneity is critical to predicting performance of the homogeneous charge compression ignition engine. Further, stratification of equivalence ratio was relatively ineffective at changing combustion while stratification of mixture temperature was very effective. Stratification of the residual fraction proved to be the most promising method of controlling combustion parameters and the mechanism was primarily thermal.

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