Multidimensional modeling of the application of catalytic combustion to homogeneous charge compression ignition engine

Journal of Thermal Science (Impact Factor: 0.4). 12/2006; 15(4):371-376. DOI: 10.1007/s11630-006-0371-5


The detailed surface reaction mechanism of methane on rhodium catalyst was analyzed. Comparisons between numerical simulation
and experiments showed a basic agreement. The combustion process of homogeneous charge compression ignition (HCCI) engine
whose piston surface has been coated with catalyst (rhodium and platinum) was numerically investigated. A multi-dimensional
model with detailed chemical kinetics was built. The effects of catalytic combustion on the ignition timing, the temperature
and CO concentration fields, and HC, CO and NOx emissions of the HCCI engine were discussed. The results showed the ignition timing of the HCCI engine was advanced and the
emissions of HC and CO were decreased by the catalysis.

1 Follower
1 Read
  • [Show abstract] [Hide abstract]
    ABSTRACT: Controlling autoignition timing over a wide range of speeds and loads is challenging. Overcoming this challenge in practical HCCI engines requires an improved understanding of the in-cylinder processes and how these processes can be favorably altered by various control techniques. In the current study, a zero-dimensional thermodynamic model that contains a simple heat release sub-model and an autoignition model was used in a predictive fashion to better understand the in-cylinder processes and the efficiency potential of a natural gas engine in the HCCI mode. The model was also used for parametric studies to evaluate HCCI control strategies that can be tested on the research engine. The results indicated that if the initial conditions of the mixture are known precisely at intake valve closing, the autoignition timing is controllable. A thermal efficiency close to 0.45 is possible with an IMEP range from 4 to 5 bar for the described engine, also.
    Energy Conversion and Management 01/2005; 46(1-46):101-119. DOI:10.1016/j.enconman.2004.02.013 · 4.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The catalytically stabilized combustion (CST) of a lean (equivalence ratio Φ = 0.4) methane-air mixture was investigated numerically in a laminar channel flow configuration established between two platinum-coated parallel plates 50 mm long and 2 mm apart. A two-dimensional elliptic fluid mechanical model was used, which included elementary reactions for both gaseous and surface chemistry. Heat conduction in the solid plates and radiative heat transfer from the hot catalytic surfaces were accounted for in the model. Heterogeneous ignition occurs just downstream of the channel entrance, at a streamwise distance (x) of 4 mm. Sensitivity analysis shows that key surface reactions influencing heterogeneous ignition are the adsorption of CH4 and O2 and the recombinative desorption of surface-bound O radicals; the adsorption or desorption of radicals other than O has no effect on the heterogeneous ignition location and the concentrations of major species around it. Homogeneous ignition takes place at x = 41 mm. Sensitivity analysis shows that key surface reactions controlling homogeneous ignition are the adsorption/desorption of the OH radical and the adsorption/desorption of H2O, the latter due to its direct influence on the OH production path. In addition, the slope of the OH lateral wall gradient changes from negative (net-desorptive) to positive (net-adsorptive) well before homogeneous ignition (x = 30 mm), thus exemplifying the importance of a detailed surface chemistry scheme in accurately predicting the homogeneous ignition location. The effect of product formation on homogeneous ignition was studied by varying the third body efficiency of H2O. Product formation promotes homogeneous ignition due to a shift in the relative importance of the reactions H + O2 + M → HO2 + M and HCO + M → CO + H + M.
    Combustion and Flame 01/1999; 116(1):243-258. DOI:10.1016/S0010-2180(98)00036-4 · 3.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper represents an experimental and numerical study of the ignition of catalytic combustion of methane in a cylindrically shaped honeycomb monolith coated with platinum. The objective is the achievement of a better understanding of transient processes in catalytic combustion monoliths. In the experiment, cold methane/oxygen/argon mixtures are fed into the monolith, which is placed in a furnace used to heat up the monolith until ignition occurs. The ignition process is monitored by thermocouples and mass spectroscopy.In the numerical study, the time-dependent temperature distribution of the entire catalytic solid structure and the two-dimensional laminar flow fields of the single monolith channels are simulated. The latter predict the gaseous velocity, species concentrations, and temperature based on a boundary-layer approximation. A multistep heterogeneous reaction mechanism is used, and the surface coverage with adsorbed species is calculated as function of the position in the monolith. The heat balance for the solid structure is coupled with the single channel simulations by axial wall temperature profiles, representing the temperature boundary condition in the single channel simulation, and by heat source terms, derived from the gaseous heat convection and chemical heat release in the single channels. The procedure employs the difference in timescales of the temperature variation of the solid, which is on the order of seconds, and of the flow, which is on the order of miliseconds. Experimentally determined and numerically predicted ignition temperatures, as well as time-varying monolith exit temperatures, and fuel conversion during ignition are compared for several CH4/O2 ratios. At the conditions applied, ignition starts at the rear end in the outmost channels.
    Proceedings of the Combustion Institute 01/2002; 29(1-29):1005-1011. DOI:10.1016/S1540-7489(02)80127-4 · 2.26 Impact Factor
Show more