Spray Atomization Research Articles

Air-blast atomization and ignition of a kerosene spray in hot vitiated crossflow

Increasingly stringent regulations of pollutant emissions from aviation require rapid implementation of novel combustion technologies. Promising concepts based on moderate or intense low-oxygen dilution (MILD) combustion have been investigated in academia and industry. This MILD regime can be obtained from the recirculation of the hot vitiated combustion products to raise the temperature of the reactants, resulting in distributed reaction regions and lower flame temperatures. In the present work, we consider the air-blast atomization of a kerosene spray in crossflow, which enables efficient mixing between fuel and oxidizer. We investigate experimentally and numerically the effect of the spray air-to-liquid mass-flow ratio (ALR) variation on the reaction front and flame topology of a kerosene spray flame. The spray is injected transversely into a turbulent vitiated crossflow composed of the products of a lean CH4-H2 flame. The spray flame thermal power is varied between 2.5 and 5 kW, along with the atomizer ALR between 2 and 6. The experimental characterization of the reaction zone is performed using OH* chemiluminescence and OH and fuel planar laser-induced fluorescence (PLIF). The Large Eddy Simulations (LES) of the multiphase reactive flow provide good agreement with the experimental observations. Experiments and simulations show that the ALR governs mixing, resulting in different flame stabilization mechanisms and combustion regimes. Low ALR results in a relatively small jet-to-crossflow momentum ratio and a large spray Sauter mean diameter (SMD). A thick windward reaction region is formed due to inefficient shear layer mixing between the fuel spray and the crossflow. Meanwhile, the correspondingly large spray SMD leads to isolated penetration and localized combustion of fuel clusters. At high ALR, the higher penetration and the faster droplet evaporation due to the lower spray SMD result in an efficient entrainment-induced mixing between the two streams, forming more distributed reaction regions.

Comparison of Electrospray And Mechanical Spray Atomization Cooling Performances on Heat Sinks

Endüstride birçok alanda kullanılmakta olan elektrosprey soğutma alanında son yıllarda keşfedilmeye başlanan bir konudur. Bu çalışmada literatürde hakkında oldukça kısıtlı çalışmalar bulunan elektrosprey soğutma ile mekanik sprey soğutmanın ısı alıcı üzerindeki soğutma performansı irdelenmiştir. Aynı şartlarda elektrosprey ile gerçekleşen ısı transferinin verileri deneyler yapılarak elde edilirken, mekanik sprey soğutma verileri Ansys Fluent CFD programı kullanılarak elde edilmiştir. Yapılan deneysel ve sayısal çalışmanın sonucunda daha küçük partikül çapı ve yüklü damlacıkların elde edildiği elektrosprey soğutmada mekanik sprey soğutmaya göre yaklaşık %15 daha iyi bir ısı transfer performansı gösterdiği belirlenmiştir. Elektrosprey metodunda, mekanik spreye göre 3,2 kW/m2 ısı akısında %13, 2,59 kW/m2 ısı akısında %14, 1,88 kW/m2 ısı akısında ise %17 daha iyi soğutma elde edildiği görülmüştür.

Metrological relations between the spray atomization parameters of a cutting fluid and formation of a surface topography and cutting force

Aerosol formation parameters are very important, as they are responsible for the ability of spray-forming droplets to penetrate the area to which they are applied. Research into modifying these parameters can therefore provide a solution for increasing the effectiveness of cooling and lubrication of the cutting zone during machining. This is particularly important for hard-to-cut materials such as titanium alloys, the machining of which requires the selection of effective cooling/lubricating methods to reduce tool wear or improve the machined surface quality. Previous research indicates that any modification in the air or oil flow rates – which form aerosols during cutting in minimized quantity lubrication (MQL) technique – contribute to an increase or decrease in the penetration of droplets into the cutting zone. It can consequently has a significant impact on machining results. This paper presents results on the effect of volumetric air flow rate P and cutting fluid mass flow rate E during the MQL cutting method on the machined surface topography after turning of Ti6Al4V alloy and the values of the cutting force. On the basis of conducted computational fluid dynamics (CFD) simulation studies, it was shown that the droplet size is more influenced by the change in volumetric air flow rate than cutting fluid mass flow rate and also that as the value of P increases, the droplet diameters decrease and the spray angle increases, which promotes the penetration of the cutting zone. As a result of the analysis of selected 3D surface roughness parameters, as well as contour maps, isometric views and material ratio curves, it was shown that the most favorable machined surface topography is being formed during MQL turning method with a volumetric air flow rate above 20 l/min. Whereby, with conditions of P = 30 l/min and E = 1.182 g/min, the machined surface topography is characterized by a uniform distribution of irregularity peaks and valleys, compared to the MQL turning with other tested values of aerosol formation parameters.

Predicting physical properties of oxygenated gasoline and diesel range fuels using machine learning

Understanding the physical properties of distillate petroleum fuels like gasoline and diesel is very critical to ensure the normal operation of internal combustion (IC) engines with regards to processes like spray atomization, heating, evaporation etc. Two of most important physical properties are density and viscosity. Many factors such as molecular structure, molecular weight, temperature etc. effect the physical properties of the fuel. The present work deals with the development of a machine learning model for predicting the density and viscosity of petroleum fuels containing oxygenated chemical classes such as alcohols, esters, ketones and aldehydes. The model was developed using the molecular structure of the compounds expressed in the form of functional groups as inputs. The density and viscosity of 164 pure compounds spanning various chemical families and 14 blends of known compositions was collected from the literature. An artificial neural network model (ANN) for predicting density and viscosity was developed using the neural network tool in Matlab. Each of the ANN model was tested against 15% of the data and the results show that the models were able to successfully predict the density and viscosity of the unseen data points to a good accuracy. A regression coefficient of 0.99 (for density) and 0.98 (for viscosity) was obtained for the test set. The developed models can be used to predict and screen the density and viscosity of real petroleum fuels containing drop in oxygenated bio-fuels.

Research and application of self-powered induction spray dust removal system for long-distance belt conveying in underground coal mines

A self-powered induction spray dust removal system for long-distance belt conveying in underground coal mines was developed. In the system, the kinetic energy of the conveyor belt can be converted into the electrical energy required by the infrared sensing atomization spray device. When the rotational speed of the roller reaches 230 r/min, 12.33 V electricity can be steadily generated. Further proposed to install multiple sets of dust reduction systems with an optimal spacing of 240 m. The effectiveness of this installation method was verified by turning systems on one by one in the 25211 transportation roadway of the Hongliulin coal mine. The total dust concentration was reduced from 11.78 mg/m3 to 3.88 mg/m3, and the respirable dust concentration was reduced from 6.33 mg/m3 to 2.48 mg/m3. The results show that the developed self-powered induction spray dust removal system can dramatically improve the long-distance belt conveying environment in coal mines.

Identification of weakly to strongly-turbulent three-wave processes in a micro-scale system

We find capillary wave turbulence (WT) spanning multiple dynamical regimes and geometries, all within a 40μL volume microfluidic system. This study is made viable with recent advances in ultra-high-speed digital holographic microscopy, providing 10μs time and 10nm spatial resolutions for images across the entire field at speeds sufficient to capture the salient wave phenomena. The observed WT types are: (i) discrete wave turbulence (DWT) dominated by finite domain effects, (ii) kinetic wave turbulence (KWT) that approximately satisfies weak wave turbulence (WWT) theory, and (iii) intermediate wave turbulence (IWT) that exhibits features from both DWT and KWT. We show that WT regime depends on input power and wavenumber, and we provide simple nondimensional parameters – derived from WWT theory – for intra-spectrum regime classification. Using the nondimensional parameters, a bulk nonlinearity metric is defined that employs bicoherence-based weighting. Analysis of experimental results reveals a correspondence between the theoretical regime classifiers and the observed phenomena. At sufficiently high input powers, the phenomena substantially depart from the WWT theory and reveal a regime of strongly nonlinear wave turbulence (SWT) defined by shallower spectral slopes that achieve a constant slope value over a range of input powers. This may suggest a corresponding power-law solution to the governing equations. This work augments current understanding of WT regimes and behaviors, and directly applies to many fields beyond fluid mechanics. For example, SWT appears upon the fluid interface at powers less than required for atomization, indicating that further study of SWT is needed to properly understand ultrasound-driven fuel spray atomization and drug and agricultural nebulization.

The cavitation flow and spray characteristics of gasoline-diesel blends in the nozzle of a high-pressure common-rail injector

In compression-ignition engines, gasoline-diesel blends have been widely concerned for its potential to reach 50% thermal efficiency and ultra-low emissions. Due to physical property difference between the two fuels, the spray atomization characteristics of the blended fuels are different from that of a single fuel, and the cavitation flow characteristics of the blends in the high-pressure nozzle and their impact on the spray are not well understood. In this paper, the visualization of cavitation flow and spray characteristics of five different proportion blended fuels (D100G0, D80G20, D60G40, D40G60, D20G80) was carried out. The influence of fuel properties corresponding to the gasoline-diesel mixing ratio on the initial generation of vortex-induced cavitation, the development of transient cavitation flow process and the injection rate and spray characteristics were studied respectively. For the tapered orifice nozzle, string cavitation is captured mainly concentrating in the needle opening initial period and closing end period, which is the main factor of spray instability and fluctuations. At the injection starting, the addition of gasoline into the diesel fuel resulted in a significant increase in string cavitation strength and larger injection rate compared to the pure diesel, even if the percentage of gasoline added is small. However, the different gasoline addition ratios have little effect on the maximum intensity of string cavitation and the duration of string cavitation in the nozzle. Accordingly, the addition of gasoline increased the overall spray cone angle and spray fluctuations throughout the injection process. Meanwhile, as the injection volume increased, the injection rate curve in the initial process is flat at first and then become steep which was precisely related to the cavitation of the vortex line in the nozzle. The findings of this paper are important guidelines for the determination of fuel injection strategies and spray analysis of gasoline-diesel blends for compression-ignition engines.

Effects of the atomisation spray on heating transfer in evaporative condensers: A numerical study

Nowadays, due to the excellent performance of evaporative condenser, it has been widely applied in various industrial fields. Improving the heat transfer performance of evaporative condensers is of great importance to save water and energy. Spray features have a significant impact on the evaporative volume and efficiency of a heat-carrying agent (water) in an evaporative condenser, further dominating the condenser’s heat transfer performance. Therefore, it is important to improve the spray characteristics to enhance the heat transfer capacity of evaporative condensers. In this study, atomisation spray technology was introduced to an evaporative condensation system to optimise the spray process parameters. The objective is to elucidate the heat transfer capacity affected by the atomisation spray parameters, including spray density, spray distance, liquid particle size, air velocity, and air temperature. In addition, it is one of the aims of this paper to investigate the degree to which each parameter affects the heat transfer performance. This paper uses numerical simulations to investigate the relationship between the atomisation spray parameters and the heat transfer performance. A tube bundle model in an evaporative condenser was developed and Lagrangian method was used to treat the discrete phase. The results showed that a decrease in either liquid particle size or air temperature could improve the heat flux. In contrast, the heat flux exhibits a para-curve trend with an increase in any of the other three parameters. When other conditions are certain, the heat flux could reach up to 54.6 kW/m2 at an optimal atomisation spray density of 3.89 × 10−3 kg/(m·s). However, it could decrease by 53.23% with the increase in liquid particle size from 0.05 to 0.26 mm. What’s more, the atomisation spray density and liquid particle size are proven to be the two most critical factors; their grey relational coefficient exceeded 0.85. Moreover, the enhancements in the heat transfer capacity are found to be probably attributed to efficient liquid evaporation (removing substantial heat) and uniform liquid film distribution (avoiding dry zone and high thermal resistance). These findings can provide support information to enhance heat transfer via the atomisation spray technique for further research on evaporative condensers.

Comparative Spray Atomization and Evaporation Characteristics of Dimethyl Ether and Mineral Diesel

Abstract Dimethyl ether is a new-generation alternative fuel to mitigate cold-start issues in compression ignition engines. It has a higher cetane number and can efficiently lead to superior atomization and evaporation characteristics. This computational study compares Dimethyl ether and baseline diesel sprays in a constant-volume spray chamber. This simulation study compares spray and evaporation characteristics en-hancement due to Dimethyl ether adaptation. Fuel properties greatly influence spray atomization and evaporation characteristics. This study is based on the Eu-lerian-Lagrangian approach adopted in the Reynolds-averaged Navier-Stokes framework. The liquid spray penetration obtained by simulations matched well with the experimental results of Dimethyl ether and baseline diesel. Spray model con-stants were tuned for diesel and Dimethyl ether separately, as the fuel properties of both test fuels are completely different. These tuned models were used to simulate Dimethyl ether and diesel sprays at fixed fuel injection timings and ambient condi-tions. Results showed a lower spray penetration length for Dimethyl ether than die-sel because of the flash boiling of Dimethyl ether. Smaller diameter droplets formed due to Dimethyl ether's lower viscosity, density, surface tension, and higher evapora-tion rate. The reduction in Sauter mean diameter was quite sharp after the start of injection for the Dimethyl ether. Diesel spray showed retarded atomization and evaporation compared to Dimethyl ether. The vapour penetration length of both fuels was almost the same; however, the vapor mass fraction was higher for Dime-thyl ether than baseline diesel. Dimethyl ether spray showed superior spray atomi-zation and improved evaporation of Dimethyl ether droplets.

Primary spray breakup from a nasal spray atomizer using volume of fluid to discrete phase model

Spray atomization process involves complex multi-phase phenomena. Abundant literature and validation of spray modeling for industrial applications like fuel injection in internal combustion and turbine jet engines are available. However, only a handful of studies, primarily limited to discrete phase modeling, of low-pressure applications, such as nasal spray exists. This study aims to provide insight into the external and near-nozzle spray characterization of a continuous spray and establishes good validation against the experiment. A three-dimensional (3D) x-ray scanner was used to extract the internal nasal spray nozzle geometry which was reconstructed to build a 3D computational model. A novel volume-of-fluid to discrete phase transition model was used to track the liquid phase and its transition to droplets, which was based on the shape and size of the liquid lumps. In this study, an early pre-stable and stable phase of spray plume development was investigated. Qualitative and quantitative analyses were carried out to validate the computational model. A liquid column exited a nozzle which distorted at its base with advancement in time and eventually formed a hollow-cone liquid sheet. It then disintegrated due to instability that produced fluctuations to form ligaments resulting in secondary breakup. This study provides in-depth understanding of liquid jet disintegration and droplet formation, which adds value to future nasal spray device designs and techniques to facilitate more effective targeted nasal drug delivery.

Numerical simulation of the dynamic wetting of coal dust by spray droplets

The dust particles generated during coal mining and processing are generally removed by spray dust reduction. The dynamic process via which spray droplets wet and wrap coal dust can directly affect the spray dust reduction efficiency. Here, we analyzed the contact wetting and wrapping process of dust particles by droplets under different particle size ratios and different initial droplet velocities. The results show that the larger the particle size ratio θ of the droplets and dust particles, the greater the variation in the dimensionless spreading coefficient. When the particle size ratio is more than 2, the droplets can completely wrap the coal dust particles. If the initial velocity is too small, the droplets will shrink and return to form a single sheet after coming into contact with the coal dust. With increasing velocity, the dimensionless spreading coefficient increases rapidly, and the coal dust is moistened and rapidly wrapped. By experimenting with various spray atomization characteristics, when the spray pressure is 6 MPa，the droplet size distribution in the spray field accounting for the highest proportion is 10 μm. Under the optimized parameters, the settling efficiency of respirable dust at each measuring point of mine return air duct reaches 86.2% on average.

Synthesis of ZnO nanoparticles via spray atomization assisted inductively coupled plasma technique

Spray atomization-assisted inductively coupled plasma system, for the first time, was utilized to synthesize ZnO nanoparticles at atmospheric pressure from a liquid precursor with varying process parameters, such as precursor concentrations and flow rates, carrier gas flow rates, and with or without the utilization of quenching gas (dry air or oxygen). The ZnO nanoparticles were characterized by FTIR, XRD, TEM, and SAED methods to evaluate the effect of process parameters on the morphology, particle size and size distribution of the final particles. The particles were in equiaxed morphology with mean particle sizes varying between 17.5 ± 9.5 nm and 25.7 ± 11.2 nm.

A Study on Dust-Control Technology Used for Large Mining Heights Based on the Optimization Design of a Tracking Spray Nozzle

Intense cutting-induced dust production in fully mechanized mining faces (FMMFs) with large mining heights produces a high amount of dust that is difficult to capture and severely affects the working environment, threatening the health of occupational staff. The effective spray range and atomization performance of tracking sprays are counteracted by the influences of the mine’s height and ventilation airflow in FMMFs. Thus, optimizing the spray’s parameters and relationship between the effective spray range and atomization performance to reduce dust levels is the main priority of dust-control techniques. In this study, a new swirl-core atomization nozzle is developed based on fluid mechanics and the solid–liquid coalescence mechanism. The liquid generates a circumferential velocity when passing through the swirl core, which considerably increases the droplet breaking power and reduces the droplet cohesion factor, achieving a remarkable atomization effect. The spray angle of the new nozzle is 57°, which is 80.9% greater than the GZPW-16 mine-use nozzle (31.5°); the effective spray range increases from 5.2 to 5.9 m; and the spray’s mist saturation is significantly better than the GZPW-16 mine-use nozzle. Under different test pressures, the particle size range of the droplets produced by the new nozzle and dust particles on site satisfied the best synergy of droplet–dust coalescence. The total and respirable dust-reduction rates were 78% and 75.1%, respectively, which were 42% and 65% higher than those of the original nozzle. The new nozzle effectively improves the efficiency of the single dust-control technique of the tracking spray, which is significant for the dust-prevention and -control technology of FMMFs with large mining heights.

Influence of split injection strategies and Trade-off study on the CRDI engine characteristics powered with waste cooking Oil/Diesel blend

An investigation has been conducted on a CRDI (common-rail diesel injection) engine utilizing a blended fuel with waste cooking oil (WCO20) to explore the influence of fuel injection strategies (i.e., split injection strategy with different fuel injection pressure) on the engine characteristics. It is observed that specific fuel consumption (BSFC) and nitrogen oxide emission (NOx) increased with a decrease in brake thermal efficiency (BTE) in the case of WCO20 at a base FIP of 40 MPa. The volatility and viscosity (physical properties) of the WCO20 fuel blend influenced the combustion phenomena resulting in a reduction in engine performance. The higher viscosity of the methyl ester blend restricts the fuel atomization process during the injection. Fuel injection pressure (Pinj) was raised from 40 to 100 MPa in increments of 25 MPa in the first phase to maximize the use of the WCO20 blend. High injection pressures (100 MPa) have higher BTE (12.33%) and better combustion characteristics (2.86 %) than lower fuel injection pressures (40 MPa). The concentrations of smoke (3.62 %), CO (15.6 %), and HC (2.8 %) were reduced as injection pressure was raised, owing to the better formation of the mixture and improved spray atomization. When used as a pilot injection before the main injection (BMI), 5% WCO20 reduces HC and CO emissions and NOx (7.82%) and smoke emissions while compromising only a marginal amount of thermal efficiency in the second phase.

An Analysis of the Process of Applying Technical Lubricating Coatings

The results of research on the process of applying lubricating coatings are presented in this work. For this purpose, plastic greases were used, in which the base oil is perfluoropolyether (PFPE) and the thickener is poly(tetrafluoroethylene) (PTFE). Due to their consistency, these materials are classified into different classes according to the National Lubricating Grease Institute (NLGI). The research was carried out using a time-pressure valve at varying atomization pressure values. Based on the obtained results, the width of the obtained material path and the angle of spray atomization were determined. The research indicated linear relationships between the atomization pressure and the degree of uniformity of the obtained spray.

Atomization characteristics of different water/heavy fuel oil emulsions in a pressure-swirl injector

In the present study, different water in heavy fuel oil (HFO) emulsion fuels containing 5, 10, 15% water content have been prepared under ultrasound irradiation without surfactant. The stability of the prepared emulsion fuels has been investigated. The best stability was observed for the emulsion fuel containing 5% water (E5) due to its more uniform water droplet size distribution. Then, the atomization behavior and spray characteristics of the emulsion fuels have been investigated in a pressure-swirl injector using a high speed camera. The examined ranges for temperature and pressure were (60–110 °C), and (10–25 bar), respectively. The breakup length for each fuel sample in each operating condition was calculated through the image processing analysis. It was found that the micro explosion phenomena associated with the evaporation of the water droplets in the fuels has the most impact on the emulsion fuel spray characteristics. The best atomization performance was observed for E5 considering all examined fuel samples. A 68% decrease in the breakup length was observed for E5 compared to the neat HFO at 90 °C and 15 bar.

Optimization-Design and Atomization-Performance Study of Aerial Dual-Atomization Centrifugal Atomizer

The aerial atomizer is the most essential component of the plant protection UAV (unmanned aerial vehicle). However, the structural optimization of existing aerial atomizers lacks comprehensive consideration of spray parameters and structural parameters, and there is a shortage of available atomizer spray models, resulting in the unstable effect of UAV application. In our previous work, an aerial dual-atomization centrifugal atomizer was developed. In order to obtain an aerial atomizer with good atomization effect and its atomization model, structural optimization at different rotation speeds and flow rates of the atomizer, and its atomization performance, are studied in this paper. Firstly, with the droplet volume median diameter (VMD) and spectral width (SRW) as the evaluation index, through the single-factor, Plackett–Burman and Box–Behnken tests, the influence of rotation speed, flow rate, tooth number and tooth shape were studied. The regression models of the droplet VMD and SRW were established using multiple quadratic regression fitting of the test data. Secondly, in order to achieve the lowest droplet VMD and SRW, the response surface method and post-hoc multiple comparison method were used to obtain the optimized structure of the atomizer’s rotation ring at different rotation speeds (600–7000 r/min) and flow rates (500–1000 mL/min). Lastly, with the effective swath width (ESW) of the optimized atomizer as the evaluation index, through the Box–Behnken test, the influence of rotation speed, flow rate and spray height were studied. The multiple quadratic regression model of ESW was established with the test data. The test results indicated that rotation speed, flow rate and tooth number had a significant effect on droplet VMD and SRW; tooth shape had no significant effect on the droplet VMD and SRW, however, the square tooth shape had the best atomization effect; and rotation speed, flow rate and spray height had a significant effect on ESW. The optimized structural parameters were tooth shape: square, and tooth number: 20. The determination coefficient R2 of the regression model of VMD, SRW and ESW were 0.9976, 0.9770 and 0.9974, respectively, which indicates that the model was accurate, and can evaluate and predict the spray effect. This paper provides an optimized dual-atomization centrifugal atomizer, and its regression models of VMD, SRW and ESW for UAV applications can provide a reference for efficient UAV spraying.

Evaluationof compact air-induction flat fan nozzles for herbicide applications: Spray drift and biological efficacy.

Nozzles are the most critical component of a sprayer for pesticide applications. Recently, air-induction nozzles and twin flat-fan air-induction nozzles have started to be used for herbicide applications. In order to evaluate the potential of compact air-induction nozzles for herbicide spraying, this paper compares the effects of air-induction nozzles and standard flat-fan nozzles on spray atomization, deposition, drift, and weed control efficacy in maize and wheat. Droplet spectra were measured by a laser particle size analyzer, and drift potential values were determined using a drift test bench (ISO 22401). A field study was conducted to compare the spray drift and biological efficacy between Lechler standard flat-fan nozzles and compact air-induction nozzles including different nozzle sizes. In the range from 0.2 to 0.4 MPa, the droplet size classes of the LU and ST nozzles were very similar and ranged from fine to very fine, while the droplets of the air-induction nozzles IDK and IDKT were medium or coarse depending on the spray pressure and nozzle size. The drift potential trials showed that the droplet size characteristics, mainly V 100, are strongly linked with the drift reduction potential. Both drift potential and field results showed that the compact air-induction nozzles had a good performance in drift reduction. In terms of weed control biological efficacy, there were no significant differences between standard flat-fan nozzles and air-induction nozzles. In all cases, the efficacy values were above 80% both in maize and in wheat. In conclusion, air-induction nozzles are recommended for herbicide applications as they provide good biological efficacy while significantly reducing the amount of spray drift, which is of great significance for the protection of the environment and the surrounding sensitive crops.

Composition-Property Relationships of pH-Responsive Poly[(2-vinylpyridine)-co-(butyl methacrylate)] Copolymers for Reverse Enteric Coatings.

The taste-masking of bitter-tasting active pharmaceutical ingredients is key to ensuring patient compliance when producing oral pharmaceutical formulations. This is generally achieved via the incorporation of pH-responsive, reverse enteric polymers, that prevent the dissolution of the formulation in the oral environment, but rapidly mediate it within the gastric environment. Reverse enteric polymers are commonly applied as coatings on oral dosage forms via spray atomisation (e.g., fluidised-bed spray coating), and generally exhibit the most efficient taste-masking. However, currently used reverse enteric coatings require high mass gains (% w/w) during coating to mediate taste-masking, and thereby exhibit delayed release within the gastric environment. Therefore, there remains a need for the development of new reverse enteric coatings, that can efficiently taste-mask at low mass gains and maintain rapid release characteristics within the gastric environment. Herein we report the synthesis and evaluation of a series of addition copolymers of 2-vinylpyridine and butyl methacrylate, methyl methacrylate and isobornyl methacrylate. The thermal, solubility, and water absorption properties of the copolymers were effectively tuned by altering the mol% fraction of the constitutive monomers. Based on their physical properties, selected copolymers were preliminarily evaluated for their compatibility with fluidised-bed spray coating, and effectiveness as taste-masking reverse enteric coatings. The copolymers poly[(2-vinylpyridine)-co-(butyl methacrylate)] (mol% ratio 40:60) and poly[(2-vinylpyridine)-co-(butyl methacrylate)-co-(methyl methacrylate)] (mol% ratio 40:50:10) were found to exhibit excellent taste-masking properties following fluidised-bed spray coating onto Suglets® sugar spheres. Suglets® bearing a film coating of either copolymer (5.2-6.5% w/w mass gain) were found to effectively impede the release of a model drug formulation for up to 72 h in a simulated salivary environment, and rapidly release it (<10 min) within a simulated gastric environment. The results demonstrated the potential of poly[(2-vinylpyridine)-co-(butyl methacrylate)] copolymers to form effectively taste-masked, reverse enteric dosage forms, and suggested that these copolymers may provide improved performance compared to currently available polymers.

A novel approach of water injection optimization applied in gasoline engines: An investigation on heated water injection

Water injection technique is a promising solution for accurate combustion control, but oil emulsion obstacle its commercial application. The present study proposes a practical approach for optimizing water spray atomization and evaporation, in which water is heated through exhaust gas recovery and directly injected into combustion chamber with a flash boiling. Firstly, a heated water injection (HWI) system was designed and established. Then, experiments were conducted to explore the effects of HWI parameters on engine combustion and emissions characteristics in terms of water injection strategies. The results present that HWI increase water evaporation rate and improves combustion efficiency. The HWI lowers flame propagation speed and improves specific heat ratio of air–fuel mixture. Elevated injection temperature lowers duration of flame kernel formation, which shortens ignition delay prolonged under conventional water injection. CA10 is advanced 4.5°CA under same spark advance while compared to conventional water injection. Moreover, HWI can not only reduce production of NOX and CO emissions but also effectively lower HC emissions by 26.2%, as water injection temperature increased to 205℃. However, excessive water injection mass and inappropriate water injection timing may worsen ignition and flame propagation, increasing unburned loss and misfire probability. The present results provide considerable evidence for the application of HWI within modern gasoline engines.