Spray Tip Research Articles

Modeling diesel spray tip and tail penetrations after end-of-injection

Zero-dimensional (0-D) modeling of spray development plays increasingly significant roles in the model-based optimization of parameter designs and control strategies in diesel engine systems. Partially premixed low temperature diesel combustion that has been deemed essential in simultaneous reductions in the nitrogen oxides (NOx) and soot emissions usually features ignition occurrence after the end of fuel injection (EOI). However, so far modeling of the spray development after the EOI is far from adequate. Particularly, a theoretical model for the spray tail penetration is still absent. The objective of this paper is therefore to develop the 0-D model for both diesel spray tip and tail penetrations. The model of spray tip penetration after the EOI is based on the existing models, and the model constant is further developed. The mathematical expression of spray tail penetration is newly deduced with the discrete control volume method. These models are validated against the experimental spray data with varied ambient densities, injection pressures and nozzle hole diameters using the high-speed shadowgraphy and the constant volume chamber. The calculated results by the models agree very well with the experimental ones. The spray tip penetration exhibits a t dependence at the initial stage of injection, a t1/2 dependence at the later stage, and a (t−ti)1/4 dependence after about two injection durations from the start of injection (SOI). While the spray tail penetration is independent of the fuel injection pressures, it exhibits a (t−ti)1/2 dependence. Since the spray tail penetration rate is rather slower than the spray tip, the spray development after the EOI shows a trend with remarkable length extension, causing the quick fuel-air over mixing. These results are believed to be valuable reference for researchers or engineers who are considering the model-based design and control strategy development for diesel engine systems.

Spray Characteristics, Combustion Performance, and Palm Oil Emissions in a Low-Pressure Auxiliary Air Fluid Pulverization Burner

This work presents the experimental results from refined palm vegetable oil atomization and combustion processes in a low-pressure auxiliary air fluid pulverization burner. The physicochemical properties that define palm vegetable oil as a fuel (density, kinematic viscosity, heating value, and elemental analysis) were first determined. The fatty acid composition was then established by proton high-resolution nuclear magnetic resonance spectroscopy. A description was provided of a procedure based on direct photographic imaging in order to determine the macroscopic properties that define the atomization spray, spray tip penetration, and spray cone angle. The influence of varying the fuel and secondary air flows in the atomization and combustion processes was also studied. The polluting emissions and combustion efficiencies in the different test conditions and how these vary depending on the atomization parameters was then evaluated. In general, admissible combustion efficiencies were obtained, with CO and N...

An experimental comparison of the elliptical and circular nozzles spray and mixing characteristics under different injection pressures

This paper presented an experimental comparison of the fuel–air mixing quality and macro spray behaviors for circular and elliptical orifice, through Mie-scattering method based on a laser beam system, at different high injection pressures (120 MPa, 140 MPa, 160 MPa) and backpressures (1 MPa, 3 MPa). It was found that the elliptical orifice exhibited shorter spray tip penetration than the circular one due to the higher air drag force induced by the larger spray surface area. Meanwhile, the difference of penetration between the elliptical and circular sprays was not obvious at the high injection pressure of 160 MPa. Also, the elliptical spray cone angles were always wider than the circular one. The interactions for the elliptical spray cone angle between major and minor planes indicated that the elliptical spray experienced axis-switching even at the high injection pressures. Moreover, the high backpressure can reduce the interaction frequency of the spray cone angle, while the high injection pressure can increase the interaction frequency. Furthermore, the elliptical spray exhibited larger spray areas than the circular spray, which suggested that using an elliptical orifice was helpful to increase the mixture quality of fuel and air. The effect of the elliptical orifice with a small aspect ratio on the spray area was not as significant as the injection pressure and backpressure especially under the high injection conditions. Finally, the elliptical spray had more mass of the entrained air as compared to the circular spray, and the injection pressure and backpressure are all had positive effects on increasing the mass of entrained air. The combination of high injection pressure with the elliptical orifice can increase the mass of entrained air, which can improve the spray and mixing quality greatly.

Investigation of the macroscopic characteristics of Hydrotreated Vegetable Oil (HVO) spray using CFD method

The main macroscopic characteristics of Hydrotreated Vegetable Oil (HVO) spray in both injection and post-injection periods are investigated via computational fluid dynamics (CFD) in this research. A 2D CFD work employing the Wave breakup model and the KHRT breakup model are validated by the experimental data from a Constant Volume Vessel (CVV). Spray tip penetration and cone angle are obtained by the CFD model under various conditions, where the rail pressure, fuel temperature, ambient pressure and ambient temperature are independently varying. Results demonstrate that the Wave model has overall higher precision in predicting the spray tip penetration and the average cone angle than the KHRT model. By the End of Injection (EOI), spray tip penetration is significantly increased by increasing rail pressure and decreasing ambient pressure. While the average cone angle is larger at high ambient pressure but not sensitive to rail pressure at the cold ambient condition. The average cone angle during injection can be enlarged by high ambient temperature, especially when the rail pressure is also high. Nevertheless, spray tip penetration can only be slightly promoted by high ambient temperature. Fuel temperature has no comparable impact on spray tip penetration and cone angle during injection. In the post-injection period (after the EOI), ambient temperature becomes dominant and spray tip penetration can be reduced by either ambient temperature or fuel temperature. An empirical model is also correlated via Design of Experiments (DoE) and has high precision in predicting spray tip penetration after the breakup time.

Effect of split injection on particle number (PN) emissions in GDI engine at fast-idle through integrated analysis of optics and mechanics

To reduce toxic engine emissions and meet the strict regulations, split injection has been adopted to optimize engine performance and fast-idle has been selected as the researching condition. Two sets of experiments have been conducted to investigate the effect of split injection on particulate number (PN) emissions at fast-idle. The first set is conducted in a constant volume vessel to get detailed spray characteristics, while the second is conducted in engine bench analyzing the effect of split injection on real engine PN emissions. Establishing direct connection from spray characteristics and real engine PN emissions is the main objective of this paper. Higher ambient temperature can reduce spray angle, while spray tip penetration is insensitive to experimental parameters. Long injection pulse width combined with short height of damper (HOD) will increase the possibility to impingement. Total PN concentration of four injection modes all decreases at first and then increases with increasing coolant temperature, and split injection can obviously reduce total PN to 50% from single injection. With increasing coolant temperature, accumulation mode particles all decrease while nucleation mode particles show different trends under four injection modes. In addition, the last injection within split injection has obvious influence on PN emissions.

Microscopic study on diesel spray under cavitating conditions by injecting fuel into water

Cavitation is a phenomenon which can significantly enhance spray breakup and affect the mixture preparation by introducing air or vapour bubbles. Attempts were made to capture the bubbles due to cavitation by injecting fuel into water based on the difference of density and refraction between water and vapour bubbles apart from the attempts to directly visualize vapour bubbles in an enlarged transparent nozzle. Tests were carried out with the employment of highly resolved microscope and ultra-high speed camera. The spray morphology and primary breakup characteristics in the near field were also investigated. It was found that irregularly shaped bubbles due to cavitation under low pressure can be observed in the nozzle. The increase of injection pressure (thereby increase of velocity) could significantly prolong the bubbles. At the nozzle outlet, the significant variation of pressure prolonged air bubbles into “thread” before collapsing. Vapour bubbles after exiting the injector nozzle were very small and the resolution of 3 µm/pixel was insufficient to capture the bubbles through direct visualization. A tree-shaped spray tip with significant radial propagation was observed. The sucking-in of water when the needle started to lift, the flow regime and the strong water resistance were closely related to the formation of tree-shaped spray tip. In addition, although the increase of fuel temperature generally enhanced the atomization of spray, the primary breakup of spray during the initial stage and end stage when the spray velocity was low surprisingly deteriorated for hot fuel.

Numerical and experimental study on effects of fuel injection timings on combustion and emission characteristics of a direct-injection spark-ignition gasoline engine with a 50 MPa fuel injection system

In this study, an increase in injection pressure was proposed as a solution to the problem of exhaust emissions, such as soot, NOx, CO, HC, in direct-injection spark-ignition gasoline engines. Mixture formation and combustion process were analyzed with KIVA-3V release 2 code. Combustion pressure and emission data were also measured experimentally. To validate the models used in simulation, spray tip penetration for various injection pressures, and combustion pressure for various injection timing and injection pressure combinations were compared with experimental data. The simulation using a constant-tuned models showed reliable results and simulations were carried out using validated models. When the fuel is injected while the intake flow is developing, the mixture homogeneity was reduced and combustion speed decreased. When the fuel is injected after the intake flow has fully developed and injection pressure was high, the combustion speed increased. High injection pressure was effective in increasing the mixture homogeneity in case of late injection timing. Therefore, increasing thermal efficiency without deteriorating exhaust emissions is possible when an injection pressure up to 50 MPa is used with late injection timing.

Microscopic study on the mechanisms for formation of the initial spray morphology

The initial spray morphology reflects the initial nozzle condition (quantity and distribution of residual fuel) derived from the previous injection, which will considerably affect the spray primary breakup. High-speed microscopic imaging technique and a single-hole diesel injector with a transparent Plexiglas nozzle were employed to investigate the mechanisms for the formation of initial spray tip morphologies and the corresponding breakup characteristics under various conditions. It was found that the interaction between liquid fuel and air bubbles, fuel properties and pressure shock-wave strength determined the spray tip morphology. Depending on the initial conditions, several types of morphologies were observed, namely, compact mushroom spray induced by surface tension under initial air-free condition, thin mushroom spray due to the acceleration effect of compressed air under low common rail pressure, drum spray tip (single or double drums) caused by the catastrophic breakup of air bubbles under common rail pressure, and mushroom-drum and central jet under fuel-free condition. Low common rail pressure allowed more time for the air bubbles to be compressed and more energy reserved in the compressed air, resulting in a higher possibility of mushroom spray formation through the accelerating effect. However, strong shock-wave under high pressure caused a high tendency for the catastrophic breakup of the air bubble and thereby production of the dispersed drum. In addition, less residual fuel left by the previous injection under high common rail pressure significantly suppressed the formation of mushroom tip.

Towards a deterministic composite collision outcome model for surface-tension dominated droplets

The focus of the present study is on the modeling and simulation of coalescence of surface-tension dominated liquid droplets in a gaseous environment. In the framework of a four-way coupled Euler-Lagrange approach using the large-eddy simulation technique, an improved composite collision outcome model identifying the four regimes of binary collisions of such droplets (bouncing, fast coalescence, reflexive and stretching separation) is assembled based on well-known correlations. A specific feature is that a hard-sphere model in combination with a deterministic collision detection is applied and hence the stochastic parcel approach often used for spray simulations is obsolete. In this composite model the bounding curves between the regimes mentioned before are taken from available experiments and described by well-known analytic correlations. The main objective is to provide a compilation of the different modeling assumptions resulting in a consistent model for the entire regime. Furthermore, the composite model is improved by introducing an additional condition to consider the overlapping region of the stretching and reflexive separation regimes at high Weber numbers. The outcome of a binary collision is identified based on the collision Weber number, the dimensionless impact parameter and the droplet size ratio. The results of each collision is treated separately with regard to the collision regime found, whereas the formation of satellite droplets during stretching and reflexive separation is currently not taken into account. Additionally, a droplet injection model for spray systems is introduced to specify the injected mass, the position, the velocity and the diameters of the released droplets. In this model the initial droplet diameters mimicking the primary break-up (atomization process) of the jet are modeled by means of a number distribution function. The implementation of the composite collision outcome model is verified using the test case of an inter-impingement spray system consisting of two crossing conical water sprays. Besides correctly reproducing the experimental correlations the composite model predicts a coalescence rate which is within the experimental range found in the literature. Then, the composite collision outcome model is applied to simulate the injection process of a solid-cone non-evaporating diesel spray into a quiescent nitrogen environment and validated against experimental data. The validation study is carried out in terms of the spray tip penetration, since it is one of the most important characteristics of sprays. A detailed comparative study is carried out to investigate the effect of different simulation parameters on the spray tip penetration. The results clearly show that a four-way coupled simulation using the enhanced composite model leads to the best agreement with the experiment.

Macroscopic and Microscopic Spray Characteristics of Diesel and Gasoline in a Constant Volume Chamber

The aim of this study is to investigate the spray characteristics of diesel and gasoline under various ambient conditions. Ambient conditions were simulated, ranging from atmospheric conditions to high pressure and temperature conditions such as those inside a combustion chamber of an internal combustion engine. Spray tip penetration and spray cross-sectional area were calculated in liquid and vapor spray development. In addition, initial spray development and end of injection near nozzle were visualized microscopically, to study spray atomization characteristics. Three injection pressures of 50 MPa, 100 MPa, and 150 MPa were tested. The ambient temperature was varied from 300 K to 950 K, and the ambient density was maintained between 1 kg/m3 and 20 kg/m3. Gasoline and diesel exhibited similar liquid penetration and spray cross-sectional area at every ambient density condition under non-evaporation. As the ambient temperature increased, liquid penetration length and spray area of both fuels’ spray were shortened and decreased by fuel evaporation near the spray boundary. However, the two fuels were characterized by different slopes in the decrement trend of spray area as the ambient temperature increased. The decrement slope trend coincided considerably with the distillation curve characteristics of the two fuels. Vapor spray boundary of gasoline and diesel was particularly similar, despite the different amount of fuel evaporation. It was assumed that the outer spray boundary of gasoline and diesel is always similar when using the same injector and injection conditions. In microscopic spray visualization, gasoline spray displayed a more unstable and asymmetric spray shape, with more dispersed and distributed fuel ligaments during initial spray development. Large amounts of fuel vapor cloud were observed near the nozzle at the end of the injection process with gasoline. Some amounts of this vapor cloud were attributed to the evaporation of residual fuel in the nozzle sac.

In-Cylinder Spray and Combustion Investigations in a Heavy-Duty Optical Engine Fueled With Waste Cooking Oil, Jatropha, and Karanja Biodiesels

In this experimental study, spray and combustion characteristics of a single cylinder optical engine were evaluated by varying the fuel injection pressure (FIP) (40, 80, and 120 MPa). Karanja, Jatropha, and waste cooking oil (WCO) biodiesels were the test fuels and their results were compared with baseline mineral diesel. There was no significant difference observed in the spray tip penetration amongst all test fuels, however the spray cone angles of biodiesels were slightly higher than baseline mineral diesel. Mineral diesel showed relatively shorter injection delay compared to biodiesels at 40 and 80 MPa FIP. Jatropha and Karanja biodiesels showed higher flame luminosity at all FIPs, while WCO biodiesel showed lower flame luminosity, especially at higher FIPs of 80 and 120 MPa, primarily due to lower viscosity of WCO biodiesel. Flame spatial fluctuation (FSF) and flame nonhomogeneity (FNH) were also found to be higher for biodiesels at lower FIP of 40 MPa. Karanja and Jatropha biodiesels showed higher FSF and FNH at higher FIPs compared to WCO biodiesel.

Dynamic spray development of 2-methylfuran compared to ethanol and isooctane under ultra-high injection pressure

Understanding spray behaviors is key for the successful employment of high injection pressure systems and biofuels such as 2-methylfuran (MF) and ethanol (ETH) in modern direct-injection gasoline engines. In this present work, the MF spray characteristics in the near-field (up to 1.6 mm) and far-field (up to 48 mm) were experimentally investigated under ultra-high injection pressure of 30, 40 and 50 MPa compared to those of ETH and isooctane (ISO). The effects of injection pressure and fuel properties on the spray morphology, tip penetration and cone angle development have been analyzed. The results showed that MF had a unique spray tip structure with a bubble attached to a mushroom tip at 30 and 40 MPa. The formation of this mushroom tip and bubble was closely related and strongly influenced by the Weber number. Among the three fuels tested, MF presented the lowest spray tip velocity at both near-field and far-field due to its large density. Compared to ETH, MF and ISO always had wider macro cone angles due to their lower viscosity.

Breakup of fuel sprays under cavitating and flash boiling conditions

Cavitation and flash boiling are important phenomena for fuel sprays of IC engines and can significantly boost spray breakup by introducing vapour bubbles, enhancing combustion, energy conversion efficiency and reducing emissions. In this study, attempts were made to capture the bubbles either due to cavitation or flash boiling under cavitating and flash boiling conditions by injecting fuels into liquid. The differences in density and refraction between water and vapour bubbles enable the bubbles to be visualized. The evolution of vapour bubbles in transparent nozzle was investigated. The direct visualization of vapour bubbles was carried out with the employment of highly resolved microscope and ultrahigh-speed camera. The spray morphology and primary breakup characteristics in the near field and macroscopic characteristics in the far field were also investigated. It was found that vapour bubbles due to cavitation or flash boiling were very small with the diameter of less than 9 µm after the primary breakup at the nozzle outlet. A tree-shaped spray tip with significant radial propagation was observed for diesel and isooctane fuels but not for dieseline (75% gasoline and 25% diesel) under liquid ambient condition. The increase of fuel temperature generally enhanced the spray atomization for the steady stage but surprisingly suppressed the primary breakup during the initial stage and end stage when the spray velocity is low. In addition, the strong disturbance of flow led to considerable radial propagation for cold diesel spray (20 °C) while the strong cavitation or flipping flow resulted in the significant radial expansion for hot gasoline spray (140 °C).

Comparison of macroscopic spray characteristics between biodiesel-pentanol blends and diesel

Spray characteristics of biodiesel-pentanol blends (with 0 v/v%, 10 v/v%, 20 v/v%, 30 v/v% and 40 v/v% pentanol) were investigated and compared with those of diesel in this work. Experiments under a variety of working conditions were carried out on a common-rail system and a constant volume chamber. High-speed Schlieren photography was used to capture the spray images. The analysis revealed that biodiesel and diesel showed the longest and the shortest spray tip penetration, the smallest and the largest spray cone angle, the smallest and the largest R (ratio between the liquid core area and the spray area), respectively. As the percentage of pentanol increased, the spray tip penetration of biodiesel-pentanol blends decreased, while the spray cone angle and R increased. BDP40 (60% biodiesel and 40% pentanol) showed similar spray characteristics as that of diesel. The comparison of tip velocities also showed that pentanol would reduce the initial axial momentum of injected fuels. Biodiesel showed the largest initial axial momentum while diesel owned the smallest one. Additionally, spray structures of blended fuels were more likely to fluctuate compared to biodiesel and diesel. The empirical equations of H-A model were used to verify the experimental results and showed great agreement between experimental results and predicts.

Numerical investigation on transient internal cavitating flow and spray characteristics in a single-hole diesel injector nozzle: A 3D method for cavitation-induced primary break-up

The spray development and atomization are strongly influenced by the internal nozzle flow. In this study, a 3D cavitation-induced primary break-up method is proposed based on cavitation characteristics studies. The reason why to develop this advanced standard method and abandon the total Eulerian approach has been discussed. The transient cavitation characteristics inside a single-hole diesel injector nozzle were numerically investigated. Combined with previous experimental studies, a dynamic mesh method and its related numerical model were utilized to investigate the inner cavitating flow characteristics for cases of different maximum needle lift values, injection pressures and ambient pressures. It is found that the mass flow rate increases significantly with the increase of maximum lift position for low needle lift cases. The cavitating flow for low needle lift cases requires necessary simulations and the traditional standard method with only empirical equations is not enough. It is also found that for high needle lift cases, the internal flow keeps stable for over 90 percent of the total injection process. The 3D method aims to incorporate as much flow information as possible to avoid using the total Eulerian approach. The 3D method allows for nozzle cross section with both two-dimensional and three-dimensional data. The spray experiment in a constant chamber with different injection pressure and the same ambient pressure is employed to validate the 3D method. The 3D method with transient internal flow profiles is implemented into the AVL Fire CFD codes. The 3D method, together with the typical standard method (with or without 1D method) are applied to the experimental data, including spray tip penetration (STP), spray shape and droplet diameter. The results show that the 3D method has good predictive ability on the spray development and shape, and it has better performance on droplet diameter prediction.

Experimental study of the effect of n-butanol additive on spray characteristics of biodiesel in a high-pressure common-rail injection system

The aim of this study was to investigate the spray characteristics of biodiesel and n-butanol/biodiesel blended fuel. The spray tip penetration and the spray cone angle were tested and analyzed. A constant volume chamber and high-speed camera were used to observe the spray evolution and a common-rail system was employed to change the injection pressure. The results show that the spray tip penetration and the spray cone angle of biodiesel are larger than those of blended fuel in most cases. n-Butanol additive changes the relationship between angle and density ratio to a certain degree. The experimental trend lines support the penetration model proposed by Hiroyasu and Arai in terms of similar proportional relation on time after start of injection, and the empirical equations provide reasonable agreement with the experimental data of the spray tip penetration.

Effects of water content on evaporation and combustion characteristics of water emulsified diesel spray

Due to its potential of reducing NOx and soot emissions simultaneously while improving thermal efficiency, water emulsified diesel is considered as one of the most promising fuels for compression ignition engines. In this study, spray and combustion characteristics of neat diesel and water emulsified diesel with various water contents (10%, 20% and 30% by mass) were investigated. The influence of micro-explosion on high pressure spray characteristics of water emulsified diesel was optically observed and discussed. Experiments were conducted in a constant volume combustion chamber with a high-speed schlieren system to capture the spray and combustion processes. The results show that water content plays a significant role in affecting spray and combustion characteristics of water emulsified diesel. Under non-evaporating condition, the spray tip penetration increases with the water content but the corresponding spray angle decreases with the water content. Such an effect was found diminishing under evaporating condition. The spray volume of test fuels increases from non-evaporating to evaporating condition, and the relative volume increase of water emulsified diesel is at least 5 times higher than that of neat diesel. Both the ignition delay and flame lift-off length increase with water content. Consequently, the integrated natural flame luminosity decreases with the increase of water content. In addition, indirect evidences have proven that the occurrence of micro-explosion can enhance the breakup and evaporation processes of water emulsified diesel spray, and the use of water emulsified diesel can effectively reduce soot emission.

Internal flow and spray characteristics for elliptical orifice with large aspect ratio under typical diesel engine operation conditions

The nozzle orifice geometry has great impact on the internal flow and spray characteristics, and thus affects the fuel-air mixture quality for diesel engines. This paper presents experimental and numerical research on the internal flow and spray behaviors with biodiesel for elliptical orifice with large aspect ratio and circular orifice of diesel nozzles, under high injection pressure and backpressure conditions. Large Eddy Simulation (LES) and Schnerr and Sauer cavitation model were adopted to study the internal flow, and the numerical models were validated firstly in terms of the mass flow rate, center line pressure and cavitation morphology. The elliptical spray images at the minor and major planes were acquired simultaneously with two CCD cameras through shadowgraph method. The results showed that the discharge coefficient of elliptical orifice was higher than that of circular orifice, which indicated that the elliptical orifice has better flow performance as compared to circular orifice. In addition, the vapor volume fraction at the circular orifice exit was larger than that of elliptical orifice, while the vorticity magnitudes were consistent lower than that of elliptical nozzle at the same injection pressure. And also, the elliptical orifice has more turbulence vortex structures near the nozzle exit than that of circular orifice, and the number of turbulence vortex structures increased as the injection pressure increases. Moreover, the cavitation distribution in the elliptical orifice in the direction of major axis shows longer length than that in the minor axis direction. The cavitation morphology at the elliptical orifice exit showed a unique horseshoe shape, while the cavitation morphology for circular orifice was still distributed symmetrically. Another important point is that the cavitation domain was similar with distribution of the turbulence vortex structures. Furthermore, the variation trend of elliptic spray cone angle proved that the elliptical spray underwent axis-switching even under high injection pressure and backpressure. Finally, the circular orifice spray held longer spray tip penetration in comparison to elliptical spray, while the elliptical exhibited much larger spray cone angle in all view planes. Because the elliptical spray underwent greater air dynamic drag induced by larger spray surface area. And the higher vorticity magnitude and more turbulence vortex structures at the elliptical orifice exit could also promote the initial spray breakup and thus inhibit the development of spray tip penetration. The axis-switching of elliptical spray can also increase the air entrainment ratio, which was conductive to increase the spray cone angle.

Nozzle internal flow and spray primary breakup with the application of closely coupled split injection strategy

Nozzle internal flow dictates the spray breakup, fragmentation and combustible mixture preparation. The dynamics of nozzle internal flow and the closely followed primary breakup under various injection pressures were studied by employing high-speed microscopic imaging technique. The effects of interaction between split injection by varying dwell interval and distribution of energizing duration between split injections on the nozzle internal flow were also investigated by using multiple injection strategy. It was found that the initial in-nozzle condition and injection pressure governs the spray tip morphology and breakup process through the strength of interaction between liquid fuel and air bubbles. Throttling effect introduced a large cloud of cavitation vapor bubbles at the needle seat during the initial stage and when stage when effective injection pressure is low. During steady flow stage, high pressure suppressed the initiation of cavitation through throttling but enhanced the cavitation generation through flow redirection. When multiple injection strategy is employed, cavitation was overall weakened, especially for flow redirection at the nozzle inlet due to reduced effective injection pressure. The injected fuel mass was reduced, and breakup quality deteriorated significantly, especially under low injection pressure. It is therefore unwise to use closely coupled split injection strategy under low injection pressure. This studied is believed to be useful for injection control and related modeling.

A Review: Non-Evaporating Spray Characteristics of Biodiesel Jatropha and Palm Oil and Its Blends

The study on the Non-evaporating spray characteristics in biodiesel is imperative to comprehend the conduct of the spray in different biodiesel. Non evaporating spray characteristics give some parameters, such as spray cone (plume) angle, spray (tip) penetration and droplet size. This paper reviews that methyl ester or biodiesel fuel from Jatropha (BDFJ) and biodiesel fuel from palm oil (BDFP) have similar characteristics of Diesel Fuel (DF). Biodiesel derived from palm oil and Jatropha oil have longer cone angle and spray (tip) penetration than DF. In biodiesel, high surface tension and viscosity, caused by the slower separation, can lead to shorter cone angle and higher penetration. Spray tip penetration will increment with the increasing of mixing proportion in biodiesel blends. In the cone angle, palm methyl ester gives a smaller angle than DF. The characteristic of cone angle is decreased when the percentage of the proportion of biodiesel is expanded. In Sauter Mean Diameter (SMD), diesel fuel sprays are smaller than the biodiesel spray. The SMD diminishes when the injection pressure is expanded. It happens because of the biodiesel has high viscosity that can expand the friction among the fuels to the surface of the nozzle. Hence, a study of biodiesel is needed before conducting the experiment of non-evaporating spray. Mainly, the fuel properties such as surface tension, viscosity and density play critical parts in the conduction of non-evaporating spray characteristics of biodiesel and its blends.