INFLUENCE OF TRACE 2-ETHYLHEXYL NITRATE (EHN) ADDITIVES ON MACRO SPRAY CHARACTERISTICS OF HIGH-PRESSURE DIRECT-INJECTION METHANOL FUEL

Experimental investigation of the effect of duct structure geometry on macroscopic spray characteristics and air entrainment of duct fuel spray

To investigate the effect of fuel physicochemical properties on spray and particulate emissions, fuel spray characteristics were tested on a constant volume chamber (CVC) test rig using a high-speed camera method to investigate the effect of different injection and ambient pressures on spray characteristics. In the engine bench tests, the effects of particulate emissions from five different diesel fuels with different physicochemical properties were analyzed under low-, medium-, and high-load steady-state conditions and 5 s transient loading conditions. The test results showed that the spray tip penetration of different CNs results from the combined effect of the fuel properties. The spray cone angle of the five fuels increased with the increase of injection and ambient pressure, and the impact of ambient pressure on the spray cone angle was more prominent. Spray tip penetration and spray projection area increase with increased injection pressure and decrease with increased ambient pressure; compared with spray tip penetration, the spray cone angle has more influence on spray projection area, especially near-field spray cone angle as the primary influence factor. Fuels with different ignition characteristics have other effects on particulates at different loads. At low loads, choosing CN = 55.3 fuel improved the number and mass of particulates; at medium and high loads, choosing CN = 51 fuel reduced the number of particulate emissions. Fuels with different volatilities have different effects on particulates at other loads. At low loads, CN = 54.9 fuel was chosen with moderate volatility and aromatic content. At medium and high loads, the volatility of the fuel had a lower weight on particulates, and the aromatic content had a higher weight. Under the transient loading condition of 5 s, using fuel with a higher CN, good volatility, and lower aromatic content can appropriately reduce the number of particulate emissions.

Increasing the injection pressure has a significant impact on atomization and combustion characteristics. Spray tip penetration serves as a vital parameter for fuel injection control and engine structure design. However, a reliable spray tip penetration model for ultra-high-pressure injection is currently lacking. To address this gap, this study establishes a theoretical 0-dimensional model for spray tip penetration under ultra-high pressure (300 MPa) conditions. The model is based on the conservation of momentum and phenomenological models. The new model divides spray tip penetration into two stages: Pre-breakup and post-breakup, with fuel injection rate and spray cone angle used as model inputs. To validate the model, high-speed camera observations and constant-volume chamber experiments are conducted to investigate the spray characteristics. The results indicate that the new spray tip penetration model demonstrates improved predictive accuracy across all experimental conditions.

The combustion and emission characteristics of inedible oils and their derivatives are quite different from those of mineral diesel; in particular, inedible oils and their derivatives present higher molecular, relative density, and vaporization characteristics. These properties exert great impacts on the fuel spray as well as the interactions of this spray with air in the combustion chamber. Thus, examining spray characteristics, including spray cone angle, spray tip penetration, spray area, and fuel atomization, is necessary. The spray characteristics of fuel mainly depend on the fuel injection pressure, density, viscosity, ambient pressure, and temperature. Among these parameters, fuel injection pressure significantly affects the spray structure. In this study, experiments were conducted using diesel, jatropha oil methyl ester, karanja oil methyl ester, and two biodiesel blended fuels (JB20 and KB20)] as fuels in a diesel engine with different injection pressures. Optical techniques for spray visualization and image processing are very efficient tools for analyzing the spray parameters of the tested fuels. Macroscopic spray properties, such as spray tip penetration, spray cone angle, and spray area, were acquired from images captured by a high-speed video camera. The Sauter mean diameter and spray volume of all of the tested fuels were also estimated. Experimental results showed that the biodiesel blends demonstrate features different from those of diesel fuel. KB100 presented the highest spray tip penetration and spray area, followed by JB100 JB20, KB20 and diesel. Diesel fuel showed the best spray parameters, followed by JB20, KB20, KB100 and JB100. The tested fuels exhibited better spray characteristics at higher injection pressures than at lower ones.

<div class="section abstract"><div class="htmlview paragraph">High-pressure gasoline fuel injection is a means to improve combustion efficiency and lower engine-out emissions. The objective of this study was to quantify the effects of fuel injection pressure on transient gasoline fuel spray development for a wide range of injection pressures, including over 1000 bar, using a constant volume chamber and high-speed imaging. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar into the chamber, which was pressurized with nitrogen at 1, 5, 10, and 20 bar at room temperature (298 K). Bulk spray imaging data were used to quantify spray tip penetration distance, rate of spray tip penetration and spray cone angle. Near-nozzle data were used to evaluate the early spray development.</div><div class="htmlview paragraph">The bulk characteristics of the high pressure gasoline sprays were consistent with trends previously observed at lower fuel injection pressures, e.g. spray tip penetration distance increased with increased fuel injection pressure after the spray break-up time and sprays with higher cone angles were produced with increasing chamber pressure at constant fuel injection pressure. The spray break-up time was a strong function of the chamber pressure at lower fuel injection pressures, but the sensitivity to chamber pressure was negligible for fuel injection pressures over 1200 bar. The experimental results for spray tip penetration distance, spray tip penetration rate and spray break-up time were compared with several correlations from the literature. For the majority of the conditions, the spray tip penetration distance was under-predicted and the spray break-up time was over-predicted. Cavitation was not observed at any condition; however, the near-nozzle imaging results showed evidence of vapor pre-jets. The frequency of occurrence of the pre-jets transitioned from no observations at a chamber pressure of one bar to ~80% for chamber pressures of 20 bar, regardless of fuel injection pressure.</div></div>

The purpose of this study is to investigate the effect of injection parameters on the injection and spray characteristics of dimethyl ether and diesel fuel. In order to analyze the injection and spray characteristics of dimethyl ether and diesel fuel with employing high-pressure common-rail injection system, the injection characteristics such as injection delay, injection duration, and injection rate, spray cone angle and spray tip penetration was investigated by using the injection rate measuring system and the spray visualization system. In this work, the experiments of injection rate and spray visualization are performed at various injection parameters. It was found that injection quantity was decreased with the increase of injection pressure at the same energizing duration and injection pressure In the case of injection characteristics, dimethyl ether showed shorter of injection delay, longer injection duration and lower injected mass flow rate than diesel fuel in accordance with various energizing durations and injection pressures. Also, spray development of dimethyl ether had larger spray cone angle than that of diesel fuel at various injection pressures. Spray tip penetration was almost same development and tendency regardless of injection angles.

Spray characteristics of a gasoline-diesel blend (ULG75) using high-speed imaging techniques

Spray and atomization characteristics of isobutene blended DME fuels

— The spray characteristic of the injected fuel is mainly depends upon fuel injection pressure, temperature, ambient pressure, fuel viscosity and fuel density. An experimental study was conducted to examine the effect of injection pressure on the spray was injected into direct injection (DI) diesel engine in the atmospheric condition. In Diesel engine, the window of 20 mm diameter hole and the transparent quartz glass materials were used for visualizing spray characteristics of combustion chamber at right angle triangle position. The varying Injection pressure of 180 - 240 bar and the engine was hand cranked for conducting the experiments. Spray characteristics for Jatropha oil methyl ester (JOME) and diesel were studied experimentally. Spray tip penetration and spray cone angle were measured in a combustion chamber of Direct Injection diesel engine by employing high speed Digital camera using Mie Scattering Technique and ImageJ software. The study shows the JOME gives longer spray tip penetration and smaller spray cone angle than those of diesel fuels. The Spray breakup region (Reynolds number, Weber number), Injection velocity and Sauter Mean Diameter (SMD) were determined for diesel and JOME. SMD decreases for JOME than diesel and the Injection velocity, Reynolds Number, Weber Number Increases for JOME than diesel.

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.

Experimental study of spray characteristics of biodiesel derived from waste cooking oil

In this study, spray characteristics of biodiesel blending with di-n-butyl ether (DBE15, DBE30) were investigated by experiment and analysis. Spray characteristics parameters including spray tip penetration and spray cone angle were used to compare the atomization effect under different injection pressures and ambient pressures. The spray tip penetration was logarithmically used to analyze the breakup time and to correct the empirical formula available from literature. The results show that the spray tip penetration of the blends added a certain proportion of di-n-butyl ether was shortened, and the spray cone angle was increased. In addition, the correction formula for introducing the density term was more suitable for the data of this experiment than the conventional empirical formula for predicting the spray tip penetration.

This study examines the spray characteristics of biodiesel, diethyl carbonate (DEC), and their mixtures in a common-rail injection system. Using the schlieren method, the spray tip penetration, spray cone angle, spray tip velocity, spray area, and spray liquid core ratio were observed with a high-speed camera. The test results show that the spray pressure and ambient pressure have significant effects on the spray characteristics. Increasing the spray pressure and decreasing the ambient pressure can increase the spray tip penetration, decrease the spray cone angle, and increase the spray area. After the addition of DEC to biodiesel, with increasing the mixing ratio, the viscosity and surface tension of the mixed fuel are reduced, but the density is increased. This increases the spray cone angle and spray area of the mixed fuel, and it reduces the Sauter mean diameter (SMD). The SMD of droplets were calculated, and it was found that DEC30 has the smallest SMD, and it is of the same order as that of diesel. An improved calculation model for the spray tip penetration of the DEC and biodiesel mixture under high injection pressure was obtained by modifying the exponent of an existing model. By comparing the linear relationship between the injection pressure and the spray tip penetration, it was found that the spray tip penetration of DEC10 has the largest increase.

In this research, three basic macroscopic spray characteristics (spray tip penetration, spray cone angle, and spray area) of long-chain alcohol-biodiesel blends were studied to investigate the differences of macroscopic spray characteristics of long-chain alcohol-biodiesel blends with different mixing ratios and to further investigate the effects of blending long-chain alcohols into biodiesel on the spray characteristics. Two kinds of long-chain alcohols, n-butanol, and n-pentanol, were selected to study effects of difference kinds of long-chain alcohols on macroscopic spray characteristics of long-chain alcohol-biodiesel blends. Results show that with the increase of proportion of n-butanol or n-pentanol in blends, spray tip penetration decreased while spray cone angle and spray area increased; in terms of the effects brought by different long-chain alcohols, n-pentanol-biodiesel blends showed slightly longer spray tip penetration, smaller spray cone angle and smaller spray area compared to n-butanol-biodiesel blends in the same mixing ratios, and the difference trends between those two kinds blends could easily be opposite due to the very similar properties of n-butanol and n-pentanol. Furthermore, a modified spray tip penetration model was proposed based on previous model and showed good agreement with experimental results.

The qualitative aspects of the fuel spray particularly spray length and cone angle play a significant role not only in the temporal sequence of clean and efficient combustion, but also in the control of engine exhaust emissions and efficiency optimization. This paper investigates the effect of injection duration and ambient pressure on spray development, spray tip penetration (L) and cone angle ( β ) of biodiesel-diesel (20%/80%:v/v) blend (B20) and diesel, and hence compares the quality of the fuels. Both ‘L’ and ‘ β ’ play a key role in the fuel evaporation and mixing of fuel with air in the combustion chamber. It was found that the injection pressure, spray tip penetration and cone angle of the fuels increased with the increase in injection duration. Furthermore, the injection pressure of B20 was higher than that of diesel because of its higher incompressibility, which increased the droplet momentum and tip penetration. The ambient pressure displayed a stronger impact on ‘L’ and ‘ β ’ of the fuels, compared with injection duration. The ‘L’ was increased, while ‘ β ’ decreased with the decrease in P amb due to the decrease in resistance to penetration velocity. The shapes of spray images of two fuels were almost similar. However, B20 exhibited larger ‘L’ and ‘ β ’ due to higher initial velocity and mass of droplet, compared with diesel. This indicates that relative to diesel fuel, B20 has a stronger impact on the spray performance, and thus improves both ‘L’ and ‘ β ’. During the earlier phase of time after start of injection, the relative difference between two fuels in terms of their spray tip penetration was smaller. This difference augmented, and then became roughly stable. Before the commencement of a comparatively steady phase of time after the start of injection, the test fuels revealed an appreciable relative difference in terms of their ‘ β ’.