In a direct injection sprayer (DI), the delay time to change the concentration of chemicals in the spray tip can have a substantial effect on sprayer performance. Delay time is the most important variable in evaluating the performance of a DI system in real time herbicide application. The flow of solution from the injection point to the nozzles was mathematically modeled to quantitatively evaluate the effect of tube volume and carrier flow rate on dynamic specifications, such as delay time. Plug-Flow and Well-Mixed models were used to model solution flow in DI systems. A DI system was designed and built to allow comparison between the mathematical model and tests results. ANOVA (Duncan test) at a 5% confidence level was used to determine the effect of change of the parameters on the delay time. A factorial completely randomized block design and SPSS 15 software were used for statistical analysis of the data. Comparison of the mathematical model with the test results showed that, for time response, the Well-Mixed model had a more appropriate response time than did the Plug-Flow model. The Well-Mixed model is suggested for predicting the dynamic behavior of a DI system. Both models produced stable state values that were slightly different from test results.

In order to comply with stringent pollutant emissions regulations, a detailed analysis of the engine combustion and emission is required. In this field, computational tools like CFD and engine cycle simulation play a fundamental role. Therefore, the goal of the present work is to simulate a high speed DI diesel engine and study the combustion and major diesel engine emissions with more details, by using the AVL-FIRE commercial CFD code. The predicted values of the in cylinder pressure, heat release rate, emissions, spray penetration and in-cylinder isothermal contour plots by this code are compared with the corresponding experimental data in the literature and is derived good agreement. This agreement makes the model a reliable tool that can use for exploring new engine concepts.

Proper design of the combustion chamber geometry and selection of the optimal fuel injection angle are key factors in reducing fuel consumption and pollutant emissions in direct injection diesel engines. In this paper, a numerical study of different combustion chamber geometries and injection angles for the 16RK215heavy-duty diesel engine has been conducted. Four different combustion chamber designs and four fuel injection angles, ranging from 130 to 160 degrees were examined. Using numerical simulations with the AVL-Fire computational code, the most suitable combustion chamber design and compatible fuel injection system were selected. An injection angle of 150 degrees and geometry number one showed the best overall performance. The highest NOx emissions were observed in geometry number one, the highest unburned hydrocarbons and soot emissions in geometry number four. The heat release rate, as a crucial parameter of combustion efficiency, reached its peak value in geometry number one. In all geometries, the highest peak temperature and average pressure were obtained at a 150-degree injection angle.

Experimental and numerical investigation of multihole gasoline direct injection (GDI) sprays at high injection pressure and temperature are performed. The primary objective of this study is to analyse the role of gas entrainment and spray plume interactions on the global spray parameters like spray tip penetration, spray angles and atomization. Three-hole 90° spray cone angle and six-hole 60° spray cone angle injectors are used for current work to examine the effect of the geometry of the injector on the spray interactions. The numerical results from Reynolds Average Navier Stokes (RANS) simulations show a reasonable comparison to experiments. The simulations provide further insight to the gas entrainment process highlights the fact that a stagnation plane is formed inside the spray cone which basically governs the semi collapse of spray that in turn affects the spray direction and cone angle.

Porous media (PM) has interesting advantages compared with free flame combustion due to the higher burning rates, the increased power range, the extension of the lean flammability limits, and the low emissions of pollutants. Future internal combustion (IC) engines should have had minimum emissions level under possible lowest fuel consumption permitted in a wide range of speed, loads and having good transient response. These parameters strongly depend on mixture formation and combustion process which are difficult to be controlled in a conventional engine. This may be achieved by realization of homogeneous combustion process in engine. This paper deal with the simulation of direct injection IC engine equipped with a chemically inert PM, with cylindrical geometry to homogenize and stabilize the combustion of engine. A 3D numerical model for PM engine is presented in this study based on a modified version of the KIVA-3V code.Due to lack of any published data about PM engine, numerical combustion wave propagation in a porous medium are compared with experimental data of methane-air mixture under filtration in packed bed and very good agreement is seen. Methane as a fuel is injected directly inside hot PM that is assumed, mounted in cylinder head. Lean mixture is formed and volumetric combustion occurs in PM. Mixture formation, pressure and temperature distribution in both phases of PM and in-cylinder fluid with the production of pollutants CO and NO and also effect of injection time, in the closed part of the cycle are studied.

In the present work, the simultaneous effects of fuel injection rate and injection of air jet into the combustion chamber on exhaust emissions, combustion process and performance parameters in a direct injection diesel engine were investigated. In order to create an air jet, a design was presented in which a secondary chamber (air cell) was created inside the cylinder and was joined to the main chamber by throats. The obtained results showed that creating the air cell had no major effect on the power and specific fuel consumption, and brought about the reduction of emitted smoke particles from the combustion chamber in all four conditions of 100% load, 75% load, 50% load and 25% load. In comparison with the base engine, the rates of oxides of nitrogen (NOx) emissions decreased at 100% and 75% loads, yet increased at 50% and 25% loads. The outcomes of the current study were compared with those existing in the relevant literature and displayed acceptable behavior.

Porous media (PM) combustion has interesting advantages compared with free flame burners due to raised burning rates, increased power ranges, extended lean flammability limits, and reduced pollutant emissions. in future internal combustion engines pollutant emissions and fuel consumption should be minimized under a wide range of speed and loads. These parameters strongly depend on mixture formation and combustion processes which are difficult to control in a conventional engine. This may be achieved by realization of a homogeneous combustion process in engine. This paper deals with the simulation of a direct injection internal combustion engine equipped with a chemically inert PM of hemispherical geometry used to homogenize and stabilize the combustion. A 3D numerical model for PM engine is presented in this study based on a modified version of the KIVA-3V code. Due to lack of any published data about the PM engine, numerical combustion wave propagation in the porous medium were compared with experimental data of methane-air mixture under filtration in a packed bed which showed very good agreement. Methane was injected directly inside the hot PM which was assumed to be mounted on the cylinder head. A lean mixture was formed and volumetric combustion occurred in the PM. The mixture formation, pressure and temperature distribution in both phases of PM and in-cylinder fluid, the production rates of co and NO, and effect of injection time in the closed part of the cycle were studied.

Hydrogen is a specified one among alternative fuels named for reducing carbon dioxide in exhaust gas. Hydrogen can be injected into runner or directly within the combustion chamber. However; direct injection would be desired because it would reduce the risk of preignition and backfiring besides recovering volumetric efficiency losses. Injection parameters play a significant role in direct injection engines. In this paper, a direct injection hydrogen fueled engine is simulated in AVL-Fire commercial software and the results are validated with experimental data from reference works. The effects of injection pressure, injector angle and spark plug position have been investigated. Results showed that increasing injection pressure would improve engine performance with increase in nitrogen oxide pollutant. Tilting the injector toward spark plug would make a rich zone near spark thus better combustion process. The study was continued focusing on spark plug position and selecting the best position due to charge stratification.

In this research, a 3D-CFD model was created to investigate the behavior of spray and combustion in a three-cylinder GDI engine using a six-hole nozzle injector. To validate the model, in-cylinder data pressure was conducted at Iran Khodro Power Train Company (IPCO) under wide-open throttle and 5500 rpm conditions. The obtained data were incorporated into the CFD model to simulate the spray evolution and combustion process inside the cylinder during fuel injection. Droplet temperature and lambda distribution from 30 deg to 279 deg after injection Were displayed. Temperature distribution during 2 to 40 deg ATDC was illustrated in the paper. Finally, evaporated fuel and wall film of the cylinder head, liner, and piston. Intake and exhaust valves and equivalence ratio in the combustion chamber have been studied.