Spray Behavior Research Articles

A comparative analysis of internal flow and spray characteristics in triangular orifices with diesel and biodiesel

This paper presents an inquiry into the internal flow and spray behavior of diesel and biodiesel in a triangular orifice, using experimental and numerical methods. The inner flow was analyzed through the implementation of Large Eddy Simulation model. Furthermore, two high-speed cameras were utilized to capture spray images of the major and minor axes of the triangle-shaped nozzle simultaneously. The investigation revealed that, in comparison to diesel, biodiesel exhibited a higher discharge coefficient. Additionally, the vorticity magnitudes and turbulence vortex structures for biodiesel were consistently lower than those for diesel. The use of biodiesel can hinder the occurrence of cavitation. Moreover, it was observed that the triangular spray cone angle displayed axis-switching phenomena for both fuels. The axis-switching phenomenon is suppressed by using biodiesel. The research also discovered that the triangular biodiesel spray has a longer spray tip penetration and a smaller angle in all view planes. This could be attributed to the higher viscosity and surface tension of biodiesel, as well as the inhibition of the spray axis-switching during the injection, leading to an increase in the spray tip penetration and a decrease in the spray cone angle for biodiesel.

Effect of natural aging on mechanical properties and corrosion behavior of 2219 aluminum alloy cold sprayed coatings

The study delves into examining how the natural aging (NA) process influences the mechanical properties and corrosion behavior of cold spray (CS) coatings. The results reveal several key insights: the consolidation behavior of auxiliary steel balls weakens, leading to a transition in the microhardness distribution of the coating from a “stepped” pattern to a more “uniform” pattern, with an average microhardness value fluctuating around 120 HV. Tensile strength experienced a reduction of 4.3 %, and elongation increased by 13.4 %. Electrochemical and peeling corrosion experiments revealed that, after aging, the coating still exhibited no signs of peeling. The corrosion resistance of the coating remains significantly superior to that of the base material (BM). Remarkably, the CS coating continues to provide effective protective functionality for joints even after undergoing 1825 days of NA.

Investigation on flash boiling phase change characteristics of two-dimensional slit nozzles using backlit light attenuation with multi-component fuels

Flash boiling atomization is an important topic in fuel preparation and fuel processing with the emergence of alternative fuels or zero-carbon fuels. The phase change of the fuel is crucial in determining the atomization performance since the phase change both affects the primary breakup and the evaporation of the fuel sprays. Typically, it is considered that the superheat index and injector nozzle designs are critical parameters in determining flash boiling spray behavior and tendency. However, the definition of superheat index is not applicable to multi-component fuels that are more commonly seen in fuel applications, such as gasoline and diesel fuels. Furthermore, no consensus has been reached on the mechanisms of flash boiling atomization. This investigation aims to address some of the key issues with optically transparent, two-dimensional slit nozzles with varied geometries. A two-dimension expansion chamber is connected to the nozzle so that the phase change occurred in the near-field downstream of the nozzle exit can be clearly visualized as well. A single-component fuel of pentane and three multi-component fuel surrogates were tested under different fuel temperatures and high-speed measurements were conducted to reveal the two-phase flow patterns and characteristics. The results show that a modified superheat index using the bubble point pressure is well-suited for multi-component fuel applications. The light attenuation in the expansion chamber correlates very well with the phase change characteristics theoretically and experimentally, that could be used as an important basis to develop a quantitative measurement technique for near-field flash boiling spray atomization.

Spray behaviour of hydro-treated ester fatty acids fuel made from used cooking oil at low injection pressures

AbstractThe spray characteristics significantly affected the combustion performance. The injection pressure and fuel properties are factors that affect the spray cone angle, penetration, and droplet distribution. Although substantial research has been conducted on spray attributes, understanding the complex biofuel spray dynamics in real nozzles and injectors is crucial. This study examines hydro-processed esters and fatty acid (HEFA) spray characteristics of used cooking oil and palm oil biodiesel in a constant-volume chamber. The study was performed by varying the injection pressures ranging from 30 to 120psi for pure fuels and Jet A-1 blends. Experiments were conducted at standard sea-level atmospheric pressure and an ambient temperature of ±297K using an airblast fuel injector. The initial fuel temperature was set at ±302K. Jet A-1 was used as the baseline fuel for the comparative analysis. Particle image velocimetry (PIV) was employed to visualise the microscopic and macroscopic characteristics of the fuel spray. The results revealed a progressive increase in the penetration length corresponding to an increase in the injection pressure. Lower pressures yielded non-uniform particle distributions across the spray area, whereas cone angle augmentation stabilised at elevated pressures. A blend of 60% Jet A-1 and 40% HEFA closely matched Jet A-1 characteristics, indicating alternative aviation fuel potential. These real-time insights into spray behaviour are critical for enhancing the fuel efficiency and mitigating the generation of particulate emissions resulting from spray combustion.

Macroscopic spray behavior in pressurized chamber alongside thermal performance of quaternary castor biodiesel with butanol and 1-butoxybutane

Biofuels derived from non-edible resources such as castor biodiesel have gained considerable attention. However, a combined spray and performance analysis of ternary and quaternary blends of castor biodiesel has not been performed. Hence, we investigated the effect of butanol and 1-butoxybutane on castor biodiesel. Macroscopic spray properties at 500 &1000 bar injection and 2 & 8 bar chamber pressures were investigated, while the performance was evaluated in diesel engine under 4 different loads ranging from 1.43 kW to 4.23 kW. Spray analysis revealed that the 20% castor biodiesel blend on average showed the maximum variation from diesel with difference of +7.24% for penetration length, −13.51% for spray cone angle and −10.12% for spray area. The quaternary blend with 10% butanol and 1-butoxybutane on average showed the least variation from diesel in terms of spray penetration (+2.07%), cone angle (−1.21%) and area (−2.11%). All the fuels showed greater fuel consumption than diesel except BB10BT10 (−2.5%) which also had better thermal efficiency (+1.72%). Hence, BB10BT10 had the optimum performance and spray quality among the tested fuels. The findings will be helpful for environmentally friendly and economically viable renewable energy sources based on castor biodiesel.

Single hole ammonia spray macroscopic and microscopic characteristics at flare and transition flash boiling regions

As a potential zero-carbon fuel for internal combustion engine to mitigate the greenhouse gas emission, ammonia’s unique flash boiling spray behaviors have not been well understood. In this study, the macroscopic and the microscopic characteristics of the liquid ammonia spray at the flare and transition flash boiling regions were experimentally investigated under different pressure ratios (RP, the ambient over the saturated pressure) and ambient temperatures. The spray macroscopic morphologies captured from the high-speed camera in the flare flash boiling region (RP ≤ 0.47) show that the spray expands significantly in radial direction while that in the transition flash boiling region (0.47 < RP ≤ 1.06) is more contracted in the penetration direction. Additionally, in flare flash boiling region, spray tip penetration and velocity increases generally with the increase of RP, while that in the transition flash boiling region in versus. Furthermore, the microscopic droplet statistics clearly demonstrate show that the most probable droplet diameter moves to a larger value with the increase of RP. The peak probability of droplet size and the droplet number density decreases at larger RP cases, resulting in a more uniformly distributed droplet sizes and an increased Sauter Mean Diameter. Finally, the ambient temperature show limited influence on the macroscopic spray penetration behaviors or the microscopic droplet size distribution, but evaporation is significantly enhanced since at highest ambient temperature, there are minimized droplet number density in some of the test locations.

Comparison of ethanol-, isobutanol-, and 2-methyl-3-buten-2-ol–gasoline sprays from a gasoline direct injector

Sprays of alcohol–gasoline fuel blends from a direct-injector were visualized with a high-speed camera utilizing a diffuse back-illuminated imaging technique. Blends of ethanol, isobutanol (2-methyl-1-propanol), and methylbutenol (2-methyl-3-buten-2-ol) with gasoline were injected into an environment representative of engine conditions. Ethanol was blended at 10, 20, and 30% by volume (E10, E20, and E30). Isobutanol and methylbutenol blends were matched to the ethanol blends on an oxygen weight percent basis resulting in blends of 16, 32, and 49% and 18, 37, and 56% by volume for isobutanol and methylbutenol, respectively. Changes in spray behavior were largely driven by changes in vapor pressure. Low-level blends of isobutanol and methylbutenol behaved nearly identically to the neat base gasoline due to their similar vapor pressures. Higher blends of isobutanol and 2-methyl-3-buten-2-ol reduced flash-boiling while ethanol blends increased it. The ambient-to-saturation pressure ratio was found to be sufficient to describe the flash-boiling transitions for all of the fuels. Measurements of spray width were found to become more dependent on ambient density with downstream distance. It was found that blending isobutanol or 2-methyl-3-buten-2-ol into gasoline in lieu of ethanol can result in significant changes to spray behavior depending on the blend level.

Evaluation of Spray and Combustion Models for Simulating Dilute Combustion in a Direct-Injection Spark-Ignition Engine

Abstract Dilute combustion in spark-ignition engines has the potential to improve thermal efficiency by mitigating knock and by reducing throttling and wall heat losses. However, ignition and combustion processes can become unstable for dilute operation due to a lowered laminar flame speed, resulting in excessive cycle-to-cycle variability (CCV) of the combustion process. To compensate for the slower combustion in less reactive mixtures, a modified intake port geometry can be employed to generate a strong tumble flow in the cylinder and elevate turbulence levels around the spark plug, thereby promoting a faster transition to turbulent deflagration. Consequently, optimizing combustion chamber geometry and operating strategy is crucial to maximizing the benefits of using dilute combustion with enhanced in-cylinder turbulence across a wide range of operating conditions. Computational fluid dynamics (CFD) simulations can be utilized for virtual engine optimization tasks, but this would require the models to be truly predictive regarding the impact of changes to the engine design and operational parameters. In this study, multicycle large-eddy simulations (LES) are performed for a direct-injection spark-ignition engine to investigate the model performance in predicting engine combustion characteristics with respect to changes in the intake configuration. A tumble plate that blocks the lower part of the intake port inlet is used to vary the tumble. A set of CFD models that have been recently developed are employed, which takes into account the drag of nonspherical droplets, flash-boiling behavior of liquid sprays, spray-wall interaction, surrogate formulation of a research-grade E10 gasoline, and fast chemical kinetic solvers. Simulation results are compared to experimental engine data in terms of cylinder pressure, apparent heat release rate, mass fraction burned timing, and flame images. It is found that LES employing the state-of-the-art CFD models are capable of properly predicting the spray processes and reproducing the measured mean cylinder pressure for the case with the tumble plate. On the other hand, the LES over-predicts the combustion rate during the early combustion stage and under-estimates the CCV, and these discrepancies become larger when the tumble plate is removed.

Investigation on Flame and Spray Characteristics of Butanol and Lemon Peel Oil Blends With Gasoline Using Optical Engine

Abstract The current research investigates the spray behavior of lemon peel oil (LPO) and butanol in a controlled environment under various engine-like conditions. The liquid spray morphology of both fuel blends is captured using a standard Mie scattering technique, and the liquid spray penetration length is compared to a baseline fuel isooctane. In order to simulate and create engine-like conditions, these experiments are carried out in a constant volume chamber under various pressure and temperature conditions. Furthermore, the combustion quality of binary and ternary blends is studied using an optical gasoline direct injection engine at three different injection timings. According to the constant volume spray study, isooctane has the shortest penetration. Because of its higher boiling point, LPO has a longer liquid spray penetration length. Despite its lower boiling point, butanol penetrates better than isooctane. The temperature was also discovered to influence liquid spray tip penetration length more than pressure significantly. In-cylinder combustion imaging results also revealed that injection timing significantly impacts combustion. Although butanol improves combustion, LPO-dominant blends demonstrated more diffusion burning due to poor evaporation characteristics. The blends prepared for the study were similar to gasoline in combustion conditions. It was discovered that these blends ran optimally without requiring any modifications to existing engines, even though late injection is recommended to improve combustion quality and peak performance.

Simulations of ammonia spray evaporation, cooling, mixture formation and combustion in a direct injection compression ignition engine

This study investigates the novel approach of direct liquid ammonia injection into the combustion chamber of a compression ignition engine. Unlike traditional gaseous ammonia port injection, this method shows promise in reducing ammonia slip and emissions. To simulate and analyze the behavior of the liquid ammonia spray, we employed numerical models based on existing literature on flashing and non-flashing spray simulations, as well as recent experimental studies on ammonia spray characteristics using a gasoline direct injection (GDI) injector. Our approach utilized a Lagrangian discrete phase modelling technique to perform a series of three-dimensional computational fluid dynamics (CFD) simulations. The primary objectives of this research were to evaluate the evaporation process of ammonia and its cooling effect, as well as to gain insights into mixture formation within the engine cylinder under different operating conditions. The simulations encompassed the entire engine cycle, considering a multi-hole GDI ammonia spray in conjunction with pilot n-heptane, a diesel surrogate, in equal proportions on an energy basis. Three distinct injection timings for ammonia were examined, leading to varying thermodynamic conditions within the combustion chamber during each spray formation. Consequently, different modelling parameters and initial conditions were necessary to accurately replicate the spray behavior. To address this, we proposed a systematic procedure for assigning pre-defined spray angles. The non-reacting, evaporating spray simulations yielded valuable insights into the mixture formation process, which guided our analysis. Finally, reacting conditions were considered to evaluate engine performance and resulting exhaust gas emissions. This study provides a comprehensive overview of critical aspects related to direct ammonia injection in internal combustion engine (ICE) systems. Moreover, it uncovers performance trends that can serve as a foundation for future investigations in this field.

Experimental study on wall heat transfer from diesel spray flame in two-dimensional combustion chamber operated with rapid compression and expansion machine (RCEM)

Heat transfer phenomenon in internal combustion diesel engine is one of problems to be solved. This study was conducted to investigate the relationship between diesel spray impingement, combustion processes, and heat loss using a rapid compression and expansion machine (RCEM). Furthermore, spray combustion and heat transfer processes were investigated using multiple injection strategies with a 6-holes injector. The amounts of diesel fuel used in the pilot, pre-injection, and main injection sprays were 3.964, 0.747, and 11.205 mg, respectively. Variations in common rail pressure conditions (30, 120, and 180 MPa) were applied to properly investigate spray evaporation, air–fuel mixture formation, and heat transfer in the combustion chamber. In addition, a local wall heat flux sensor was installed in the cylinder (head and liner) and piston cavity (upper lip, lip, and bottom) to measure the heat flux distribution, and a diffused backlight illumination method was used to visualize the spray and flame behavior in the combustion chamber and 2D piston cavity. The results showed that the impingement flame surrounding the cylinder head contributed to the highest magnitude and longest duration of the heat flux on the cylinder side owing to the spray flame velocity, impingement, and residence time. Meanwhile, the highest different temperature at cavity bottom induced more heat flux on the cavity side than that on the squish side. In addition, the higher injection pressure increased the spray momentum and spray tip penetration which led to a better air–fuel mixture, better evaporation rate, and less flame residence that contributed to reduce the accumulated heat loss in combustion chamber. Furthermore, a low common rail pressure was found to induce a greater difference in the accumulated heat flux ratio than a high common rail pressure which is owing to longer flame residence time in the combustion chamber. They were approximately 14% and 6% greater than that compared to the baseline common rail pressure which mean that a high common rail pressure contributes for the improving thermal efficiency in spray combustion.

Optoelectronic, photocurrent sensitivity and photocatalytic dye degradation behaviour of spray deposited Cr doped SnO2 thin films

Undoped and SnO2:Cr doped thin films (Cr: 0.25, 0.50, 0.75 and 1 wt%) were deposited by economically home-made spray pyrolysis method. The characteristic behaviour of the deposited films was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Photoluminescence (PL), Ultraviolet–visible (UV–vis.) spectroscopy, Current-Voltage (I–V) and photocatalytic studies. The XRD analysis confirms the tetragonal rutile structure of SnO2 with predominant orientation along the (2 1 1) plane and the decrease in crystallite size from 48 to 30 nm by Cr-doping. The EDAX and XPS studies reveal the elements and its chemical state of Sn, O and Cr. The SnO2:Cr thin films exhibit an 85% average optical transmittance in the visible region of the electromagnetic spectrum. The SEM micrographs clearly show the well-defined grains with boundaries, and it is evident that grain size drastically reduces from 155 nm to 48 nm as a function of Cr-doping. Photoluminescence analysis confirms the defect-related emission (360 nm, 440 and 490 nm). The photocatalytic activity of all thin films is assessed using malachite green (MG) dye under UV light irradiation. 0.75 wt% Cr-doped SnO2 film shows improved photocatalytic performance (60.37%) than undoped thin film (32.03%). The I–V characteristics of undoped and SnO2:Cr thin films are performed in visible light, showing photo-linear response behaviour. The highest figure of merit (FOM) obtained for SnO2:Cr (0.75 wt%) thin film is 7.07 × 10−6 Ω−1. The obtained values of the FOM and photocatalytic performance are discussed in the context of the suitability of these materials for transparent and conducting window materials in solar cells and photocatalytic degradation applications.

Further Development of Gasoline from the bioliq® Process with Focus on Particulate and Hydrocarbon Emissions

The production of CO2-neutral fuels is a key technology to achieve the European Union’s targets of greenhouse gas reduction in the transport sector. For a straightforward application such as drop-in fuel, regenerative gasoline must meet emission requirements without causing significant changes in engine parameters. The objective of this work was to demonstrate the emission reduction potential of fuel from the bioliq® plant by reducing the content of heavy aromatics in the product refinement. For three blends with varying contents of bioliq® fuel, the spray behavior was studied in a pressurized chamber and the particulate and hydrocarbon emissions were investigated using a single-cylinder research engine. With increasing bioliq® fuel content, atomization was degraded by lower flash boiling at low pressure. This effect vanished at higher chamber pressures. Measurements of particulate and hydrocarbon emissions showed significant improvements of 50% to 100% and 10%, respectively, compared to previously investigated bioliq® fuel fractions from 2017. The formation of particulate emissions is virtually unaffected by the blending of bioliq® fuel, due to the absence of heavy aromatics in the refined bioliq® product. Hydrocarbon emissions increased by 20% with higher bioliq® fuel content and late injection timings due to inferior mixture formation as a result of slightly reduced atomization. However, near the optimum injection timing, the hydrocarbon emissions are independent of the bioliq® fuel admixture.

An Experimental Study on the Injection Characteristics and the Macroscopic Spray Characteristics of Rapeseed Oil-Diesel Fuel Blends

In this study, the injection processes and spray behavior of diesel fuel (DF), rapeseed oil (RO) and their fuel blends (RO25, RO50, RO75) have been qualitatively and quantitatively analyzed to identify the differences in the injection rate and the spray parameters. The volumetric and mass injection rates, the spray penetration, the spray cone angle and the spray area under non-evaporation conditions in a nitrogen-filled camber were analyzed. The results showed that rapeseed oil leads to a decrease in the peak injection rate due to its higher density and viscosity. Moreover, rapeseed oil and its blends with mineral diesel oil exhibited smoother rising slopes at the start of injection. The spray tip penetration was the longest for the rapeseed oil and the spray tip penetrations of the fuel blends RO25, RO50 and RO75 were arranged between the values of DF and RO. As the injection pressure increased, the differences in the spray tip penetrations diminished. Increasing the amount of rapeseed oil in fuel blends resulted in a smaller spray cone angle compared to diesel fuel. The spray area of all tested fuels increased significantly with increasing spray tip penetration, the spray area of RO was consistently lower than that of diesel fuel.

Investigation of Mechanical Behavior and Surface Characteristics of Cold Spray Metallized B4C/AA7075 Composites Coated by AZ64 Alloy through Plasma Electrolytic Oxidation

Metallized cold-spray coatings were employed to make B4C/AA7075 and aluminum + plasma electrolytic oxidation (PEO) duplex coatings on AZ64. In addition, the phase structure, mechanical characteristics, wear, and PEO ceramic coatings examine the corrosion resistance. According to the findings, the PEO ceramic coating comprises α-aluminum oxide and γ-aluminum oxide, with some remnants of B4C still being preserved. PEO ceramic coatings outperformed their corresponding CS counterparts regarding mechanical characteristics and wear resistance. For example, the PEO-B4C coating achieved a hardness of 13.8 GPa and an elastic modulus of 185.5 GPa, which were 21.0% and 23.5%, respectively, more significant than the comparable values for the coating with CS. The PEO-B4C coating was 58% and 15.7% less abrasive than the equivalent CS coating due to its lower wear rate of 4.84 × 10−5 mm3/Nm and relatively lower of 0.64. The density of corrosion current in the PEO-treated B4C-AA7075 coating (3.735 × 106 A/cm2) is similar to the corrosion current density in the untreated CS coatings. Finally, compared to untreated CS B4C-AA7075, the coating’s mechanical characteristics and wear resistance are considerably enhanced by the PEO treatment.

Optical measurements of two cylindrical and conical heavy-duty diesel injector nozzels – A comparison of reference diesel, HVO, and RME fuels

In the present work, a constant volume/constant pressure combustion chamber was utilized to measure the major parameters of vapour/liquid phases and combustion of fuel spray introduced by two heavy-duty, large-diameter diesel injectors. A conical nozzle (K factor 4) with a 300 µm outlet diameter and a 1300 µm length and a cylindrical nozzle (K factor 0) with a 300 µm outlet diameter and a 650 µm length display notably distinct impacts on the formation of the mixture, the air entrainment process, and the combustion behaviour. Several parameters, including jet and liquid spray penetration lengths, jet cone angle, and jet projected area are combined to describe spray characteristics in an inert background gas, and ignition incidence, flame lift-off length, and soot appearance time parameters are calculated to explain the combustion trend of the nozzles in a reactive gas background. These observations were conducted using four distinct optical techniques, two of Schlieren and Mie-Scattering for inert condition, and two of OH* Chemiluminescence and Natural Flame Luminosity for reactive condition. This study collects a wide variety of boundary conditions, comprising ambient pressure/temperature and fuel rail pressure, with diverse fuels, including reference diesel, HVO, and RME fuels.The findings are categorized by the jet and liquid spray behaviours in the first part, demonstrating that the jet cone angle is an injector geometry-based parameter and that the cylindrical nozzle has a larger cone angle and a shorter liquid spray length. Three distinct scenarios of the computed air-to-fuel mass ratio at the same axial positions, time steps, and injected fuel mass indicate a marginally higher air entrainment in the cylindrical nozzle and, presumably, a faster and better mixture formation. The thorough examination of the combustion characteristics indicates that a quicker formation of the initial stoichiometric region in the cylindrical nozzle results in a shorter ignition delay at most experimental locations, which ultimately results in a faster soot initiation. However, depending on the flame lift-off length and the boundary conditions, the interval between ignition and the development of soot varies considerably. Finally, it is demonstrated that, with the exception of fuel pressure variation, the flame lift-off length, which is crucial in providing the initial mixture formation prior to combustion occurrence, follows the ignition delay trend and exhibits a shorter length with a shorter ignition delay.

Experimental investigation on collision characteristics of dual-spray with different physical-chemical fuel properties: A case study of butanol-biodiesel fuel combination

The dual direct injection strategy can flexibly control the reactivity distributions and equivalence ratio, which shows a great potential in realizing clean and efficient combustion. However, the sprays’ collision is inevitable when the fuel sprays are injected into the combustion chamber simultaneously owing to limited in-cylinder space, which is rarely investigated. The investigation aims to explore the atomization and combustion characteristics of collision between biodiesel and butanol sprays at different injection delay times of biodiesel (0, 0.5, 1, 1.5, 2 ms). Experiments are conducted in a constant volume combustion chamber. The collision spray and combustion images are captured by optical diagnosis techniques. Several macroscopic parameters are obtained, including spray behavior, spray area, ignition delay, ignition location, flame behavior, flame lift-off length, and natural luminosity intensity. Results show that the variation of injection delay time can effectively change the spray distribution and realize the concentration stratification. The liquid-phase diffusion region increases with an increased premixed charge of butanol spray, but the total evaporation time has a tiny difference. The sprays’ collision can promote the ignition process, but the ignition location is slightly affected by the injection delay time of biodiesel. A trade-off relationship between the vapor-phase diffusion area and combustion characteristics is found. When the injection delay time exceeds 0.5 ms, a longer injection delay time can lead to a larger vapor-phase area, which causes smaller equivalent ratio, longer flame-off length, and lower luminosity intensity. However, a longer injection delay would lead to an uncomplete combustion of the n-butanol spray. At the experimental cases, the injection delay time of biodiesel should be 1/2–2/3 injection duration to realize complete combustion and small emissions.

Diesel Spray Liquid Length Imaging at High Pressure

Engine efficiency and emissions depend on the fuel atomization and dispersion. The fuel atomization and dispersion depend heavily on the ambient pressure and temperature. In this work, to study Diesel sprays in engine conditions, an electrically heated, constant-volume, pressurized vessel was designed and manufactured. The controlling electronics and software were developed and tested to ensure safe and precise operation. A commercial Bosch six-hole automotive Diesel injector was used. The spray spatial and temporal development were studied. In the literature, spray liquid length and cone angle are extensively used to quantify fuel dispersion. In this work, these parameters were quantified using a high-speed shadowgraph technique. Models were derived to describe the temporal evolution of the liquid core. Such models can be used to predict the Diesel spray behaviour and the engine performance.

Experimental Investigation of High-Pressure Liquid Ammonia Injection under Non-Flash Boiling and Flash Boiling Conditions

Liquid ammonia is an ideal zero-carbon fuel for internal combustion engines. High-pressure injection is a key technology in organizing ammonia combustion. Characteristics of high-pressure liquid ammonia injection is lack of research. Spray behaviors are likely to change when a high-pressure diesel injector uses liquid ammonia as its fuel. This study uses high-speed imaging with a DBI method to investigate the liquid penetration, width, and spray tip velocity of high-pressure liquid ammonia injection up to 100 MPa. Non-flash and flash boiling conditions were included in the experimental conditions. Simulation was also used to evaluate the results. In non-flash boiling conditions, the Hiroyasu model provided better accuracy than the Siebers model. In flash boiling conditions, a phenomenon was found that liquid penetration and spray tip velocity were strongly suppressed in the initial stage of the injection process, this being the “spray resistance phenomenon”. The “spray resistance phenomenon” was observed when ambient pressure was below 0.7 MPa during 0–0.05 ms ASOI and was highly related to the superheated degree. The shape of near-nozzle sprays abruptly changed at 0.05 ms ASOI, indicating that strong cavitation inside the nozzle caused by needle lift effects is the key reason for the “spray resistance phenomenon”.

Characteristics of penetration and distribution of a liquid jet in a divergent cavity-based combustor

The atomization process of a liquid jet in a divergent cavity-based combustor was investigated experimentally using high-speed photography and schlieren techniques under a Mach number 2.0 supersonic crossflow. Gas-liquid flow field was studied at different divergent angles and injection schemes. It is found that complex wave structures exist in the divergent cavity-based combustor. The spray field can be divided into three distinct zones: surface wave-dominated breakup zone, rapid atomization zone and cavity mixing zone. A dimensionless spray factor is defined to describe the concentration of spray inside the cavity qualitatively. As a result, it is revealed that for the large divergent angle cavity, the injection scheme near the upstream inlet has a higher penetration depth but a lower spray distribution, where the injection scheme near the cavity has a more spray distribution. For the small divergent angle cavity, the injection scheme near the upstream inlet also has a higher penetration depth and the injection scheme near the start point of the divergent section has a more sufficient spray distribution. The small divergent angle cavity-based combustor with the upstream wall transverse injection is an optimized injection scheme to improve both penetration and spray distribution inside the cavity. Finally, a penetration depth formula is proposed to explain the spray and distribution behaviors in the divergent cavity-based combustor.