Consideration of the effects of increasing spray cone angle and turbulence intensity on heavy-duty diesel engine pollution and specific outputs using CFD

In this article, the effects of increasing spray cone angle and turbulence intensity on the performance and emission of heavy-duty diesel engine has been examined in two separate stages using AVL-Fire CFD code. First, the injector and its spray have been simulated with various geometries. In this step, the Eulerian-Eulerian model has been applied for injector simulation and the Eulerian -Lagrangian model has been applied for spray simulation. The numerical results of this step indicate that creating swirly flow inside the nozzle decreasing penetration length while, fuel spray cone angle increasing during the injection process. In the subsequent step, the heavy-duty diesel engine has been simulated with its conventional and different nozzle hole geometries. In this step, the Eulerian-Lagrangian model has been applied to simulate the engine cycle. The numerical results of this step show that the nozzle with spiral rifling like guides has better performance and lower emission compared to other nozzle geometries. In this case, the fuel consumption is decreasing 32% than cylindrical nozzle hole, while the engine power and its torque increasing 63%. In addition, the amount of nitrogen oxide (NOx) and carbon monoxide (CO) for the spiral convergent conical nozzle geometry reducing 15% and 30% respectively than cylindrical nozzle hole while engine has no soot emission problem. Diesel injector and engine CFD results and experimental data have been validated from previous researches.

New insights on manipulating the material removal characteristics of Jet-Electrochemical machining through nozzle design

Jet-Electrochemical machining (Jet-ECM) is a novel variation of traditional electrochemical machining in which electrically conductive material is removed through anodic dissolution by means of a fine jet of electrolyte. In this study, the effect of nozzle geometry on material removal characteristics are investigated through physical experiments performed on a Jet-ECM system under development at the university of Manchester. A total of 8 nozzles with holes encompassing converging, diverging and rounded features are studied at flow rates between 0.125 and 0.225 l/min. The results show that the nozzle hole geometry has a significant effect on the machined profile produced due to variations in flow velocity, pressure, and electric current distribution with converging hole nozzles providing an increased depth of cut than the symmetrical cylindrical channel by up to 9.7%. A 2D Star CCM+ simulation is also proposed, and numerical results developed and compared with experimental ones to investigate the feasibility of using simulation to develop future nozzle designs. The simulated results show good profile comparison to the experimental results, however, the model needs developing to improve the process repeatability for future use in nozzle design.

Direct Numerical Simulation of Bubble Formation Through a Submerged “Flute” with Experimental Validation

Direct Numerical Simulation (DNS) is often used to uncover and highlight physical phenomena that are not properly resolved using other Computational Fluid Dynamics (CFD) methods due to shortcuts taken in the latter to cheapen computational cost. In this work we use DNS along with interface tracking to take an in-depth look at bubble formation, departure, and ascent through water. To form the bubbles air is injected through a novel orifice geometry not unlike that of a flute submerged underwater, which introduces phenomena that are not typically brought to light in conventional orifice studies. For example, our single-phase simulations show a significant leaning effect wherein pressure accumulating at the trailing nozzle edges leads to asymmetric discharge through the nozzle hole, and an upward bias in the flow in the rest of the pipe. In our two-phase simulations, this effect is masked by the surface tension of the bubble sitting on the nozzle, but it can still be seen following departure events. After bubble departure, we observe the bubbles converge towards an ellipsoidal shape, which has been validated by experiments. As the bubbles rise, we note that local variations in the vertical velocity cause the bubble edges to flap slightly, oscillating between relatively low and high velocities at the edges. Thus, causing the bubble edges to periodically lag and lead the bulk bubble mass.

Improving the performance of a diesel engine by changing injectors characteristics after reduction on the compression ratio

In order to repair internal combustion engines, sometimes it is necessary to replace the components of these engines with each other. Therefore changes in engine performance are inevitable in these conditions. In the present study, by changing the coneccting rod and the crank of the OM457 turbo diesel-fueled engine with the OM444, it was observed that the performance of the engine decreases. Numerical simulations have been carried out to study the Possible ways to mitigate this reduction. One way to achieve this goal is to change the fuel injector’s characteristics such as, fuel injector’s nozzle hole diameter, number of nozzle holes, and start time of fuel injection. In this study, the impact of these parameters on the performance and emissions of these engines were analyzed. Another scenario is an increase in inlet fuel and air by the same amount. The results indicate that By reducing the diameter of fuel injector holes and hole numbers, the performance of the engine was increased. on the other hand, the NOx emissions were increased while the amount of soot emission decreased. The same results were concluded by retarding the start time of injection. Subsequently, a case study of changing fuel injector parameters for mitigation of decreased performance was performed. These parameters were simultaneously applied, and results were compared. The performance of the engine with improved injector’s characteristics was close to the main OM457. Similar results were obtained by increasing the amount of inlet air and fuel.

Effects of nozzle hole size and rail pressure on diesel spray and mixture characteristics under similar injection rate profile – experimental, computational and analytical studies under non-evaporating spray condition

In the present work, effects of nozzle hole size and rail pressure under non-evaporating spray condition are demonstrated. Three single hole injectors with the bore size of 0.101, 0.122, and 0.133 mm are experimented with injection pressures of 140, 45, and 38 MPa respectively to achieve similar injection rate profile. Diesel spray experiments implement Diffused Backlight Illumination Technique where diffused background is obtained for the High Speed Video camera imaging. Experimental results are then validated with computational and analytical studies. The CFD simulation requires the injection rate profile and spray cone angle as a primary input; thus, based on the High Speed Video Camera start of injection frame the 5 kHz Butterworth low-pass frequency filter is applied to the injection rate raw data. While, the spray cone angle is predicted using a simple model obtained from the relationship between the injection velocity, fluctuating velocity at the nozzle exit and total pressure loss factor of the injector. The experimental spray tip penetration of all three injectors is almost identical as the similar injection rate profile is adopted. Although, the mixture characteristics are better for 0.101 mm hole diameter since the smaller hole diameter with highest injection pressure depicts larger spray angle and better atomization. The computational study agrees with experiments qualitatively; however, the quantitative and qualitative agreements are seen in the analytical study.

Simulation and Injector Bench Test Validation of Different Nozzle Hole Effect on Pyrolysis Oil-Diesel Oil Mixtures

The tire pyrolysis oil is a waste-derived fuel with a lower cetane number and higher den-sity than diesel fuel, but this is a promising waste-based fuel for compression ignition en-gines. In the European Union, it is necessary to increase the bio-share of fuels, and the second-generation waste-derived blend components are essential for achieving the 2030 goals. The injection characteristics of tire pyrolysis oil and diesel oil were investigated on a Bosch solenoid type common rail (CR) injector. Six different premixed ratios were investi-gated, including in a low volume percentage 250 ppm and higher 10%, 20%, and 100% pyrolysis oil and 100% diesel oil. The simulation investigation was done in the AVL Fire software, the experimental investigations were done on a LDX CR injection test bench, and the videos were taken on an Olympus Ispeed 3 camera. The scope of the research was to record the flow pattern of the fuel mixture, flowing out of the high-pressure injector, from which the mixing with air and the quality of the resulting combustion can be deduced, which has a significant effect on the emissions.