COMBUSTION OF LPG-AIR LEAN MIXTURE : A SOLUTION FOR POLLUTION REDUCTION OF MOTORCYCLES IN VIETNAM

Joint Research on Environmental Science and Technology for the Eart

Turbulent burning velocity in combustion chamber of SI engine fueled with compressed biogas

Turbulent burning velocity is the most important parameter in analyzing pre-mixed combustion simulation of spark ignition engines. It depends on the laminar burning velocity and turbulence intensity in the combustion chamber. The first term can be predicted if one knows fuel composition, physico chemical properties of the fluid. The second term strongly depends on the geometry of the combustion chamber and fluid movement during the combustion process. One cannot suggest a general expression for different cases of engine. Thus, for accuracy modeling, one should determine turbulent burning velocity in the combustion chamber of each case of engine individually. In this study, the turbulent burning velocity is defined by a linear function of laminar burning velocity in which the proportional constant is defined as the turbulent burning velocity coefficient. This coefficient was obtained by analyzing the numerical simulation results and experimental data and this is applied to a concrete case of a Honda Wave motorcycle engine combustion chamber that fueled with compressed biogas. The results showed that the turbulent burning velocity coefficient in this case is around 1.3 when the average engine revolutions is in the range of 3000 rpm to 6000 rpm with biogas containing 80% Methane. We can then predict the effects of different parameters on the performance of the engine fueled with compressed biogas by simulation

SMALL POWER ENGINE FUELED WITH BIOGAS

Joint Research on Environmental Science and Technology for the Eart

ENERGY-ENVIRONMENT ISSUE IN TRANSPORT OF VIETNAM

Joint Research on Environmental Science and Technology for the Eart

3D unsteady turbulent flow analysis in a Francis turbine runner at nominal and off-design operating conditions

This paper presents the use of a commercial Navier-Stokes turbulent flow code (FLUENT) as a mean to evaluate the behavior of a Francis turbine runner for the design and off-design conditions. The flow in the runner is analyzed numerically at different operating points. The numerical results permit to observe physical phenomena in the runner that are important in the process of hydraulic turbo machinery design. Values of different velocity components in the flow, blade pressure distribution ... given by the model are compared with experimental data at nominal and off-design flow conditions. Computer resource involves in the flow analysis should be compatible with the need of design process of a runner. Therefore 12 hours of CPU time can be considered as acceptable for calculating at each operating point on a computer workstation of medium size power

Comparison of soot radiation in diesel flame given by mathematical model and by experimental data

An integral unidirectional model is established to calculate radiation heat transfer of Diesel flame in the open air and in combustion chamber of engine. Based on the temperature and soot fraction given by the flamlet theory and soot formation model of Tesner-Magnussen, radiation of soot particulate cloud at different positions of flame is determined and compared with experimental data obtained by the two-color method.The results show that the radiation given by the model is 203 lower than that produced by experiments on the stationary flame in open air. Soot radiation intensity in the Diesel engine increases in function of load and engine speed regimes and its maximum value (about 2000 kW/m2) is reached when the highest pressure is attained in combustion chamber

Calculation of turbulent diffusion jets under effects of gravity and moving surrounding air

The basis theory for the turbulent diffusion of jet and flame has been presented previously [1, 2]. But that one applies only in quiet surrounding air with the effects of buoyancy neglected. In the present paper, the theory is developed further by establishing an integral model for a jet in more general conditions with variable inclined angles, under effects of gravity and surrounding air velocity in any direction compared to the jet axis. The system of equations is closed by turbulence k-E model and is solved by 4th order Runge-Kutta method. In the first stage, the model is applied to predict the velocity field, the concentration field and with development of a 0.3 m diameter jet

Comparison of velocity distribution in turbulent diffusion jet given by the integral model and code CFD FLUENT 6.0

Integral model is simple in utilization, low in CPU time calculation, suitable for a lot of practical applications of turbulent diffusion jet. However the assessment of accuracy of the model should be carried out by experimental data and by results of available multidirectional codes. The present paper shows the comparison of velocity profiles given by the integral model and the CFD FLUENT 6.0 Code. The difference in results given by the two models is lower than 10% when Reynolds number at the exit nozzle below 5000

Phenomenological model for determining velocity field of LPG jet in combustion chamber of direct injection S.I. engine

A phenomenological model has been established to predict the velocity distribution of LPG (Liquefied Petroleum Gas) jet in combustion chamber of spark ignition (SI) engine. A shaped coefficient $\beta$ governing the similarity of velocity profiles of LPG jets has been defined based on the theoretical and experimental analyses of turbulent diffusion jets. The results show that $\beta$ is constant for steady jet but it is not the case for unsteady one. The model will enable us to calculate the velocity profiles of LPG jet after ending injection. This is necessary for research of stratified combustion in direct injection LPG SI engines

Abrasion resistance and compressive strength of unprocessed rice husk ash concrete

This paper investigates the effects of adding natural rice husk ash collected from uncontrolled burning and without previous grinding (NRHA) as cement replacement in concrete. To obtain an adequate particle size, NRHA was mixed with coarse aggregate for a convenient period of time before adding the other components. Compressive strength, water absorption, porosity, and abrasion resistance expressed as weight loss were examined. Test results show that decreasing the particle size through mixing with coarse aggregate improved the compressive strength, reduced the permeability, and increased the abrasion resistance of concrete. By mixing NRHA with aggregate for 8 min, abrasion resistance improved by 10.35 and 23.62% over the control concrete at 28 and 91 days, respectively. Incorporating NRHA in concrete by grinding with coarse aggregate during the mixing process could be suitable for making normal-strength concrete and for applications where abrasion resistance is an important parameter. In addition, using NRHA as a partial replacement cement contributes to the reduction of CO2 emissions due to the production of cement