A fully coupled computational fluid dynamics and multi-zone model with detailed chemical kinetics for the simulation of premixed charge compression ignition engines

2005 ◽  
Vol 6 (5) ◽  
pp. 497-512 ◽  
Author(s):  
A Babajimopoulos ◽  
D N Assanis ◽  
D L Flowers ◽  
S M Aceves ◽  
R P Hessel
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Chemical Kinetics ◽  
Zone Model ◽  
Compression Ignition ◽  
Detailed Chemical Kinetics ◽  
Fully Integrated ◽  
Fully Coupled ◽  
Detailed Chemical ◽  
The Ideal

Modelling the premixed charge compression ignition (PCCI) engine requires a balanced approach that captures both fluid motion as well as low- and high-temperature fuel oxidation. A fully integrated computational fluid dynamics (CFD) and chemistry scheme (i.e. detailed chemical kinetics solved in every cell of the CFD grid) would be the ideal PCCI modelling approach, but is computationally very expensive. As a result, modelling assumptions are required in order to develop tools that are computationally efficient, yet maintain an acceptable degree of accuracy. Multi-zone models have been previously shown accurately to capture geometry-dependent processes in homogeneous charge compression ignition (HCCI) engines. In the presented work, KIVA-3V is fully coupled with a multi-zone model with detailed chemical kinetics. Computational efficiency is achieved by utilizing a low-resolution discretization to solve detailed chemical kinetics in the multi-zone model compared with a relatively high-resolution CFD solution. The multi-zone model communicates with KIVA-3V at each computational timestep, as in the ideal fully integrated case. The composition of the cells, however, is mapped back and forth between KTVA-3V and the multi-zone model, introducing significant computational time savings. The methodology uses a novel re-mapping technique that can account for both temperature and composition non-uniformities in the cylinder. Validation cases were developed by solving the detailed chemistry in every cell of a KIVA-3V grid. The new methodology shows very good agreement with the detailed solutions in terms of ignition timing, burn duration, and emissions.

Progress in the Development of Chemical Kinetics Databases for the Combustion of Real Fuels

2008 ◽  
Author(s):  
Wing Tsang
Keyword(s):  
Fluid Dynamics ◽  
Chemical Kinetics ◽  
Liquid Fuel ◽  
Chemical Kinetic ◽  
Vlsi Circuits ◽  
Wind Tunnel Testing ◽  
Detailed Chemical Kinetics ◽  
Combustion Technology ◽  
Kinetics Of ◽  
Detailed Chemical

Modern Computational Fluid Dynamics codes have increasing capabilities for taking into account detailed chemical kinetics [1, 2]. This opens the possibility of simulating the combustion of real fuels in industrial devices. This will bring combustion technology in line with modern developments in cutting edge science. One could not design VLSI circuits without simulations. Similarly, the design of modern airplanes depends on simulations before final wind tunnel testing. A key to the proper simulation of the chemistry in combustion is the kinetics database. The aim of this paper is to describe the current situation in this area. We will begin by discussing the special problems posed by the nature of the fuel. We will then define the elements in a proper chemical kinetic database. Currently used databases for the simulation of combustion will be critically examined. The importance of a more fundamentally based database will be emphasized. Finally some recent work pertaining to the chemical kinetics of real liquid fuel molecules will be described.

Computational Fluid Dynamics Simulations of the Effect of Water Injection Characteristics on TSCI: A New, Load-Flexible, Advanced Combustion Concept

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Mozhgan Rahimi Boldaji ◽  
Aimilios Sofianopoulos ◽  
Sotirios Mamalis ◽  
Benjamin Lawler
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Thermal Stratification ◽  
High Efficiency ◽  
Water Injection ◽  
Compression Ignition ◽  
Cfd Model ◽  
Detailed Chemical Kinetics ◽  
Advanced Combustion ◽  
Rate Of Combustion

Homogeneous charge compression ignition (HCCI) combustion has the potential for high efficiency with very low levels of NOx and soot emissions. However, HCCI has thus far only been achievable in a laboratory setting due the lack of control over the start and rate of combustion and its narrow operating range. In the present work, direct water injection (WI) was investigated to solve the aforementioned limitations of HCCI. This new advanced combustion mode is called thermally stratified compression ignition (TSCI). A three-dimensional computational fluid dynamics (3D CFD) model was developed using CONVERGE CFD coupled with detailed chemical kinetics to gain a better understanding of the underlying phenomena of the water injection event in a homogeneous, low temperature combustion (LTC) strategy. The CFD model was first validated against previously collected experimental data. The model was then used to simulate TSCI combustion and the results indicate that injecting water into the combustion chamber decreases the overall unburned gas temperature and increases the level of thermal stratification prior to ignition. The increased thermal stratification results in a decreased rate of combustion, thereby providing control over its rate. The results show that the peak pressure and gross heat release rate (HRR) decrease by 37.8% and 83.2%, respectively, when 6.7 mg of water were injected per cycle at a pressure of 160 bar. Finally, different spray patterns were simulated to observe their effect on the level of thermal stratification prior to ignition. The results show that the symmetric patterns with more nozzle holes were generally more effective at increasing thermal stratification.

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