The effect of using different Biodiesel fuels on jet development in a Diesel engine

The fuel properties and the injection rate-shape play an important role in the improvement of the combustion process of Diesel engines. In this work, the influences of using the forthcoming renewable biodiesel fuels on fuel jet development utilizing a computer simulation model created with the AVL Hydsim software were studied. Biodiesel fuels B20, B30 and B100 were considered and compared with the original pure Diesel fuel D100. The injection system behaviour under research was that one existing on a tractor engine equipped with Delphi DP200 pump and Delphi injectors. Two engine speeds of 1400 rpm and 2400 rpm were considered representative for the engine operation. For these speeds, the fuel jet characteristics as penetration, spray cone angle and Sauter mean diameter were analyzed. It can emphasize that in similar conditions of needle lift and injection rate-shape variation the usage of biodiesel fuels does not significantly alter the injection pressure and the Sauter mean diameter. However, the specific physical properties of biodiesel fuels affect substantially the spray penetration and its cone angle.

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.

Analysis of elliptical diesel nozzle spray dynamics using a one-way coupled spray model

The elliptical nozzle has the potential ability to increase the air-fuel mixture quality. A one-way coupled spray model and Homogenous Relaxation Model (HRM) was adopted to investigate the spray behaviors and the air-fuel mixture progress in real diesel combustion chamber with the application of elliptical and circular diesel nozzle. The results indicated that the spray cone angle and the air entrainment mass of elliptical nozzle were larger than that of the circular nozzle, while the spray penetration of the elliptical nozzle which the aspect ratio is 1.5 and 2 was shortened by 11% and 8.3% as compared to circular spray respectively. Also, the air entrainment mass of the elliptical spray with a ratio of 1.5 and 2 increased by 60% and 35% as compared with circular spray respectively. Furthermore, the partial equivalent ratio and the high concentration area in the cylinder is reduced for elliptical nozzle, and the air-fuel mixture is more uniform. The fuel evaporation rate of elliptical spray is always higher than that of the circular spray.

Investigation on Flat-Fan Spray Characterization in High-Speed Air Coflow for Gas Turbine Online Water Washing Application

Fouling in compressor blades due to dirt deposition is a major issue in land-based gas turbines as it impedes the compressor performance and degrades the overall engine efficiency. The online water washing approach is an effective alternate for early-stage compressor blade cleaning and to optimize the time span between offline washing and peak availability. In such case, typically a series of flat-fan nozzles are used at the engine bell mouth to inject water sprays into the inflowing air. However, optimizing the injector operating conditions is not a straightforward task mainly due to the tradeoff between blade cleaning effectiveness and material erosion. In this context, the knowledge on spray characteristics prior to blade impingement play a vital role, and the experimental spray characterization is crucial not only to understand the basic process but also to validate numerical models and simulations. The present paper investigates spray characteristics in a single flat-fan nozzle operated in the presence of a coflowing air within a wind-tunnel. A parametric investigation is carried out using different air flow velocity in the tunnel and inlet water temperature, while the liquid flow rate was maintained constant. The spray cone angle and liquid breakup length are measured using back-lit photography. The high-speed shadowgraphy technique is used for capturing the droplet images downstream of the injector exit. The images are processed following depth-of-filed correction to measure droplet size distribution. Droplet velocity is measured by the particle tracking velocimetry (PTV) technique. As both droplet size and velocity are known, the cross-stream evolution of local droplet mass and momentum flux are obtained at different axial locations which form the basis for studying the effectiveness of the blade cleaning process due to droplet impingement on a coupon coated with foulant of known mass.

An Experimental Study On Cryogenic Spray Quenching of a Circular Metal Disk I. Effects of Mass Flux, Spray Fluid Inlet Subcooling, and Gravity

This is the first part of a two-paper series that reports the design, experimentation, and results of a spray quenching experiment of a circular metal disk in terrestrial gravity conditions. The objective of this experiment is to provide experimental data and corresponding analysis on the heat transfer characteristics and chilldown performance of the cryogenic spray quenching process. In this paper, the presented continuous-flow spray quenching results include the spray-cone angle visualization, spray cooling heat transfer characteristics represented by chilldown curves and boiling curves, gravity effects, and Leidenfrost rewet point temperatures. Additionally, detailed discussion is given on the film boiling heat transfer and rewet temperature in terms of various contributing factors such as gravitational acceleration, spray mass flux, and radial position on the plate. Based on experimental data, empirical correlations for film boiling heat transfer coefficient and rewet temperatures are provided. We expect that, the current terrestrial study would offer invaluable information for the design of a robust in-space cryogenic propellant storage tank spray chilldown system.

Design of a Nasal Spray Based on Cardiospermum halicacabum Extract Loaded in Phospholipid Vesicles Enriched with Gelatin or Chondroitin Sulfate

The extract of Cardiospermum halicacabum L. (C. halicacabum) obtained from flower, leaf and vine was loaded into modified phospholipid vesicles aiming at obtaining sprayable, biocompatible and effective nasal spray formulations for the treatment of nasopharyngeal diseases. Penetration enhancer-containing vesicles (PEVs) and hyalurosomes were formulated, and stabilized by adding a commercial gelatin from fish (20 mg/mL) or chondroitin sulfate from catshark cartilages (Scyliorhinus canicula, 20 mg/mL). Cryo-TEM images confirmed the formation of spherical vesicles, while photon correlation spectroscopy analysis disclosed the formation of small and negatively-charged vesicles. PEVs were the smaller vesicles (~100 nm) along with gelatin-hyalurosomes (~120 nm), while chondroitin-PEVs and chondroitin-hyalurosomes were larger (~160 nm). Dispersions prepared with chondroitin sulfate were more homogeneous, as the polydispersity index was ~0.15. The in vitro analysis of the droplet size distribution, average velocity module and spray cone angle suggested a good spray-ability and deposition of formulations in the nasal cavity, as the mean diameter of the droplets was in the range recommended by the Food and Drug Administration for nasal targets. The spray plume analysis confirmed the ability of PEVs, gelatin-PEVs, hyalurosomes and gelatin-hyalurosomes to be atomized in fine droplets homogenously distributed in a full cone plume, with an angle ranging from 25 to 30°. Moreover, vesicles were highly biocompatible and capable of protecting the epithelial cells against oxidative damage, thus preventing the inflammatory state.

Effect of application of electric force to diesel fuel droplets charged through Millikan oil-drop experiment on physical and thermal characteristics of flame

This paper proposes a new feasible method to allow continuous change in the primary injection spray cone angle of liquid fuel droplets, which are injected from nozzles in liquid fuel combustion systems, to control the flame shape and thermal characteristics of the flame. The method is based on electric force applied to fuel droplets charged through frictional effects between the internal surface of the nozzle and the fuel flow as the liquid fuel is sprayed (based on the Millikan oil-drop experiment). A sprint computational fluid dynamics (CFD) code was developed to investigate the effect of application of electric force to charged diesel fuel droplets, which were injected from a pressure swirl atomizer, on physical and thermal characteristics of a two-dimensional axisymmetric turbulent jet diffusion flame. The results show that an electric field applied to charged fuel droplets (electric force) changes the spatial distribution of the liquid fuel droplets in the flame reaction zone. An applied electric force in (−y) direction diverts the fuel droplets towards the axis centerline of the furnace and, consequently, decreases the primary injection cone angle and increases the concentration of the evaporated droplets around the axis centerline, which enhances the fuel-oxidant mixing rate and raises the flame temperature. Unlike an applied electric force in (−y) direction, an applied electric force in (+y) direction decreases the flame temperature. However, as the primary injection cone angle is decreased, an applied electric force in (+y) direction increases the flame temperature.

Research on the internal flow and macroscopic characteristics of a diesel fuel injection process

The internal flow and macroscopic spray behaviors of a fuel injection process were studied with schlieren spray techniques and simulations. The injection pressures(Pin)and ambient pressures(Pout)were applied in a wide range. The results showed that increasing the Pin is likely to decrease the flow performance of the nozzle. Furthermore, increasing the Pin can increase the spray tip penetration. However, the effect of Pin on the spray cone angle was not evident. The spray cone angle at an injection pressure of 160MPa was 21.7% greater than at a pressure of 100MPa during the initial spraying stage. Additionally, the discharge coefficient increased under high Pout, and the decrease in Pout can promote the formation of cavitation. Finally, increasing the Pout can decrease the penetration, while the spray angle becomes wider, especially at the initial spray stage, and high Pout will enhance the interaction of the spray and the air, which can enhance the spray quality.

Computational assessment of performance parameters of an aero gas turbine combustor for full flight envelope operation

This paper presents the computational study carried out on an aero gas turbine combustor to assess important performance parameters. The CFD results are compared with experimental dataobtained from the full scale combustor tested at ground test stand simulating various operational conditions. The CFD predictions have agreed very well with the experimental data. The model is then extended to predict combustor exit temperature pattern factors, pressure loss, and combustion efficiency and exhaust gas constituents over a wide range of operating pressure and temperature conditions. The paper also presents the studies carried out on the effect of atomizer spray cone angle, particle size and fuel flow variations expected due to manufacturing tolerances in various flow passages as well as due to operational degradations on temperature pattern factors. The pattern factors are also analyzed on cold and hot day environment. The radial pattern factor (RPF) at mid height is found to increase as altitude increases from sea level to 12 km. Spray cone angle is found to have a predominant effect on temperature non-uniformity at exit, lower cone angle increasing both radial and circumferential pattern factors. The findings of this study are valuable inputs for engine performance estimation.