Spray Jet Research Articles

Effect of air–fuel mixing quality on characteristics of conventional and low temperature diesel combustion

A comparative study on the effects of air–fuel mixing quality on combustion characteristics was carried out in both conventional and low temperature diesel combustion (LTC) regimes. The injection pressure and intake pressure were considered as variables as they are important factors which influence the air–fuel mixing process. The intake O2 concentration was varied to realize different combustion regimes. Improved air–fuel mixing with a higher injection pressure enhanced the combustion process in both conventional combustion and LTC regimes, resulting in higher peaks of in-cylinder pressure and heat release rate. The combustion phase in the LTC regime was more influenced by injection pressure due to longer premixing time than that of conventional combustion. A higher injection pressure reduced CO and HC emissions over a wide range of intake O2 concentrations. The reduction of CO and HC emissions in the conventional combustion regime was due to higher combustion temperature, while that in the LTC regime was due to decreased under-mixed fuel by improved air–fuel mixing. Soot emissions at a higher injection pressure were reduced, particularly, in the conventional combustion regime where the soot formation rate is high. The increase of intake pressure was also advantageous in reducing CO, HC and soot emissions due to improved air–fuel mixing as well as enrichment of absolute amount of oxygen, which lead to enhanced combustion process. A direct flame image was taken to observe the flame structure of two different combustion regimes to correlate with the exhaust emission results and combustion characteristics. High flame luminosity was observed around the periphery of the spray jet in the conventional combustion regime, which was a direct indication of soot formation and high temperature combustion; while low luminosity was observed around the piston bowl in the swirl direction in the LTC regime, which indicated a longer air–fuel mixing period and low temperature combustion.

High-repetition-rate three-dimensional OH imaging using scanned planar laser-induced fluorescence system for multiphase combustion

Imaging dynamic multiphase combusting events is challenging. Conventional techniques can image only a single plane of an event, capturing limited details. Here, we report on a three-dimensional, time-resolved, OH planar laser-induced fluorescence (3D OH PLIF) technique that was developed to measure the relative OH concentration in multiphase combustion flow fields. To the best of our knowledge, this is the first time a 3D OH PLIF technique has been reported in the open literature. The technique involves rapidly scanning a laser sheet across a flow field of interest. The overall experimental system consists of a 5 kHz OH PLIF system, a high-speed detection system (image intensifier and CMOS camera), and a galvanometric scanning mirror. The scanning mirror was synchronized with a 500 Hz triangular sweep pattern generated using Labview. Images were acquired at 5 kHz corresponding to six images per mirror scan, and 1000 scans per second. The six images obtained in a scan were reconstructed into a volumetric representation. The resulting spatial resolution was 500×500×6 voxels mapped to a field of interest covering 30 mm×30 mm×8 mm. The novel 3D OH PLIF system was applied toward imaging droplet combustion of methanol gelled with hydroxypropyl cellulose (HPC) (3 wt. %, 6 wt. %), as well as solid propellant combustion, and impinging jet spray combustion. The resulting 3D dataset shows a comprehensive view of jetting events in gelled droplet combustion that was not observed with high-speed imaging or 2D OH PLIF. Although the scan is noninstantaneous, the temporal and spatial resolution was sufficient to view the dynamic events in the multiphase combustion flow fields of interest. The system is limited by the repetition rate of the pulsed laser and the step response time of the galvanometric mirror; however, the repetition rates are sufficient to resolve events in the order of 100 Hz. Future upgrade includes 40 kHz pulsed UV laser system, which can reduce the scan time to 125 μs, while keeping the high repetition rate of 1000 Hz.

The Study of Placement Pattern Micro Sprinkler Depends on Hanging Micro Sprinkler Irrigation Against the Value of Irrigation Efficiency

Micro-sprinkler Irrigation which emitter are laid in hanging position was one’s alternative on water given technology to getting high and uniform irrigation efficiencies. Sprinkler irrigation efficiency determined by the value of a Coefficient of Uniformity (CU) and value of Distribution Uniformity (DU). This research purpose is seeking to locate and test placement pattern and the distance spaces between sprinkler to obtain a better value of irrigation efficiency on each type of micro sprinkler. This research was carried out in September-October 2012, which are located in the greenhouse of Faculty of Agriculture, Padjadjaran University. The method of performed on this research is descriptive analysis, with a two pattern of the placement that are tested which is a square in a serial manner and square in parallel, with three spaces between the tested sprinklers i.e. 55%, 60% and 65% of the wetting diameter on three kinds of micro sprinkler in three repetitions. This research concluded that the best distance spaces between the sprinkler on hanging position the type of microspin ie equal to 4,8 meters (60 %), on the type of modular the best sprinkler distance spaced amounting to 5,2 meters (65 %) and a square parallel pattern was the best sprinkler placement pattern on both of this type . Whereas on the type of spray jet the best sprinkler spaces are 1,65 meters (55%) and a pattern of a square series is the best pattern on the type of this . the value of a coefficient of uniformity (CU ) and distribution uniformity (DU) there are most properly on the type of microspin with the result of the value of CU amounting to 91,43 % , and the results value of DU by 86,52 % .

Characterization of Modified Tapioca Starch Solutions and Their Sprays for High Temperature Coating Applications

The objective of the research was to understand and improve the unusual physical and atomization properties of the complexes/adhesives derived from the tapioca starch by addition of borate and urea. The characterization of physical properties of the synthesized adhesives was carried out by determining the effect of temperature, shear rate, and mass concentration of thickener/stabilizer on the complex viscosity, density, and surface tension. In later stage, phenomenological analyses of spray jet breakup of heated complexes were performed in still air. Using a high speed digital camera, the jet breakup dynamics were visualized as a function of the system input parameters. The further analysis of the grabbed images confirmed the strong influence of the input processing parameters on full cone spray patternation. It was also predicted that the heated starch adhesive solutions generate a dispersed spray pattern by utilizing the partial evaporation of the spraying medium. Below 40°C of heating temperature, the radial spray cone width and angle did not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The discharge coefficient, mean flow rate, and mean flow velocity were significantly influenced by the load pressure but less affected by the temperature.

0606 液滴衝撃エロージョンに関する実験的研究

This paper presents an experimental study on the liquid droplet impingent erosion of aluminum material using the high-speed spray jet. The flow configuration studied is the pin-hole type erosion, which has the erosion depth comparatively larger than the spray width. The experimental result shows that the growth rate of the erosion is decreased with an increase in the erosion depth due to the influence of liquid film and their relationship is formulated.

石英基片精密干冰清洗效果的红外光谱差示法

A given kind of silica substrates, which low hydroxy group is contained by, was made (quantitative analysis) by the way of infrared differential spectroscopy. Some characteristic absorption peaks of methylene and methyl were measured as a measurement of organic compound. As many data before and after fine CO2 jet spray cleaning were obtained, some rules appeared statistically. Cleaning rate connects to the polluted degree. The higher the polluted degree is, the faster the cleaning rate is. Cleaning rate can also be reduced by the mixture of mineral and big particles. Furthermore, topography affects cleaning rate, too. All of them support the research method, and the process and results claim that for research and production process optimization, it is very important to find a way to insure the consistency of polluted degree on the surface before fine CO2 jet spray cleaning.

Non-Aqueous Cleaning Challenges for Preventing Damage to Fragile Nano-Structures: A Review

With semiconductor-device geometry shrinking and becoming more complex, highly diluted chemicals are used during aqueous silicon wafer cleaning. The use of physical cleaning aids such as megasonic agitation with dilute chemistry or high-pressure atomizing jet sprays to avoid reduction of particle removal efficiency is prone to cause structural damage to both fragile freestanding MEMS and high-aspect-ratio LSI structures. The surface tension of water can also cause pattern collapse of nano-structures. In addition to this, ultra-pure water can cause several other problems resulting in the degradation of device characteristics. These problems make the development of novel damage free non-aqueous cleaning methods a high priority. In this paper, several water-caused problems to bring damage to silicon devices are discussed with some possible solutions and, as the ultimate solutions to overcome the shortcomings of water-based cleaning, various alternative damage-free non-aqueous cleaning techniques are overviewed and discussed, which include low pressure, elevated temperature HF vapor cleaning, cryogenic aerosol nitrogen cleaning, supercritical carbon dioxide cleaning, and pinpoint dry cleaning that employs lasers, nano-probes, or nano-tweezers. There will be more research challenges and opportunities in these environmentally-benign damage-free cleaning technologies in the near future.

Low temperature spray combustion of acetone–butanol–ethanol (ABE) and diesel blends

The combustion characteristics of acetone–butanol–ethanol (ABE) and diesel blends were studied in a constant volume chamber under both conventional diesel combustion and low temperature combustion (LTC) conditions. In this work, 20vol.% ABE without water (ABE20) was mixed with diesel and the vol.% of acetone, butanol and ethanol were kept at 30%, 60% and 10% respectively. The advantageous combustion characteristics of ABE-diesel include higher oxygen content which promotes soot oxidation compared to pure diesel; longer ignition delay and soot lift-off length allowing more air entrainment upstream of the spray jet thus providing better air–fuel mixing. Based on the analysis, it is found that at low ambient temperature of 800K and ambient oxygen of 11%, ABE20 presented close-to-zero soot luminosity with better combustion efficiency compared to D100 suggesting that ABE, an intermediate product during ABE fermentation, is a very promising alternative fuel to be directly used in diesel engines especially under LTC conditions. Meanwhile, ABE–diesel blends contain multiple components possessing drastically different volatilities, which greatly favor the occurrence of micro-explosion. This feature may result in better atomization and air–fuel mixing enhancement, which all contribute to the better combustion performance of ABE20 at LTC conditions.

An empirical evaluation of an integrated inclined solar water desalination system with spray jets variation

In this study, the productivity of an integrated inclined solar water desalination system with spray jets was empirically investigated. The effects of the feed water flow rate, solar radiation, ambient temperature, absorber plate temperature, cavity air temperature, glass cover temperature, variation in number of spray jets, and inlet and outlet temperature of the feed water on the daily production of the system were studied. The results show that the system productivity increases with two spray jets rather than with four and six jets tested on the system. The daily production also increases by cooling the system glazing and by solar radiation intensity. The inclusion of a wick (black cloth) on the absorber plate has a significant effect on the system production. The wick improved the daily production of the system by 23%. The daily production of the system with a wick on the absorber plate in the summer season is recorded as 6.41 kg/m2 while the daily production with a bare plate absorber is recorded as 5.19 kg/m2. The system (with wick) has a daily production of 3.327 kg/m2 in the winter season. The experimental results in this study were compared with published data related to solar desalination units.

Visual Study of Hollow Cone Water Spray Jet Breakup Process at Elevated Temperatures and Pressures

The liquid jet breakup is a ubiquitous phenomenon in nature and a classic problem in hydrodynamics. The understanding of the jet breakup mechanism of hot liquids is still a challenge for researchers. The objective of this work was to understand and control the hot water spray jet breakup mechanism at moderate pumping pressures and elevated temperature. For this purpose, the visual and comparative studies were conducted on hollow cone water spray patterns generated by three hollow cone spray nozzles which were installed in an in-house built intermittently forced liquid spraying system. Using a high speed camera, the jet breakup dynamics were visualized as a function of system input parameters. The analysis of the grabbed images confirmed the strong influence of these processing parameters on spray characteristics. It was also predicted that heated liquids generate the dispersed spray patterns and the induction of thermal energy into the system enhances the jet disintegration ability. The spray cone width and angle were not varied significantly whereas the Weber and Reynolds numbers along with other spray parameters showed an appreciable response to the load pressure and water heating temperature at early stages of water injection.

Pool Fires Of Biofuels And Their Blends With Petroleum Diesel

The combustion characteristics of pool fires of biofuels, canola methyl ester (CME), soy methyl ester (SME), and their blends with a petroleum fuel (No. 2 diesel) were studied. The fuels were burned in cups of two sizes (0.042 m and 0.057 m in diameter and 0.038 m height) that simulated convection-dominated small pool fires of liquids. Blends of CME and SME with diesel fuel were tested with biofuel concentrations of 25, 50, and 75% by volume. The mass burn rate, the fuel surface regression rate, the radiation emission from the flames, the flame temperature field, and the emission indices of CO and NOx were recorded. The fuel surface regression rate in both containers was comparable. Both the fuel mass burning rate and surface regression rate varied non-monotonically with the volume concentration of biofuel in the blend. The radiation fraction of heat release and the temperature profiles were similar for all the flames. The CO emission index decreased with the biofuel content in the fuel. The NOx emission index did not show a systematic and significant dependence on the fuel blend; however, it was smaller than that measured in the turbulent gas jet and liquid spray flames of the corresponding fuels.

MONTE CARLO RELIABILITY SIMULATION OF WATER SYSTEM OF LONGWALL SHEARER MACHINE

The water system of coal shearer machine consists of three main subsystems namely spray jets, water & hoses, and filters which are connected and working in series configuration. In this paper, the Kamat–Riley Monte Carlo simulation method was used for reliability analysis of the considered system. The studied data was collected from an Iranian longwall coal mine for analysis. The MATLAB software was used for simulation and then reliability plot of water system in shearer machine was determined. The results show that the reliability of shearer machine reduces to almost zero in a period of 300 h. Comparison between the results of analytical method and simulated reliability plot presents that for analyzed data set, in high reliability levels (28% ≤), the simulation approach estimates the higher reliability than analytical method. The maximum difference between the results of analytical and simulation methods is 23%. However, in low reliability levels (≤ 28%) there is no remarkable difference between the methods.

A General “Surface‐Locking” Approach toward Fast Assembly and Processing of Large‐Sized, Ordered, Mesoporous Carbon Microspheres

Drying to meet you: Using microfluidic jet spray drying technology in conjunction with the evaporation-induced self-assembly strategy gives fast assembly (2 s) of mesoporous carbon microspheres. The key feature of the drying is the formation of a rigid silica crust which locks the particle size and shape.

200kW 급 태양광발전 어레이 표면의 냉각/세정에 대한 장기 실증 실험

태양광 발전은 일사량이 높을수록 발전량이 증가된다. 그러나 일사량이 높아짐에 따라 셀의 온도도 같이 증가하여 발전효율은 감소하게 된다. 일반적으로 태양광 셀(Cell) 표면의 온도를 1℃ 감소시키면 약 0.5%의 발전량의 증가가 있다고 알려져 있다. 본 논문은 태양광 발전량 증가를 위해 냉각/세정 장기 실증 실험을 수행하였다. 기전력과 집광량을 높이기 위해 모듈 표면 온도를 낮추고 오염물질을 제거하는 냉각/세정 기술을 이용하였다. 실험 방법은 냉각/세정 설비가 설치된 곳과 설치되지 않은 곳의 이용률을 비교하였다. 장기 실증 시험을 결과 냉각/세정 설비의 구동으로 인한 발전량이 최소 13%에서 최대 19%까지 증가하였다.

Adapting of the Background-Oriented Schlieren (BOS) Technique in the Characterization of the Flow Regimes in Thermal Spraying Processes

In thermal spraying technique, the changes in the in-flight particle velocities are considered to be only a function of the drag forces caused by the dominating flow regimes in the spray jet. Therefore, the correct understanding of the aerodynamic phenomena occurred at nozzle out let and at the substrate interface is an important task in the targeted improvement in the nozzle and air-cap design as well as in the spraying process in total. The presented work deals with the adapting of an innovative technique for the flow characterization called background-oriented Schlieren. The flow regimes in twin wire arc spraying (TWAS) and high velocity oxygen fuel (HVOF) were analyzed with this technique. The interfering of the atomization gas flow with the intersected wires causes in case of TWAS process a deformation of the jet shape. It leads also to areas with different aero dynamic forces. The configurations of the outlet air-caps in TWAS effect predominantly the outlet flow characteristics. The ratio between fuel and oxygen determine the dominating flow regimes in the HVOF spraying jet. Enhanced understanding of the aerodynamics at outlet and at the substrate interface could lead to a targeted improvement in thermal spraying processes.

A statistical method to identify the main parameters characterizing a pressure swirl spray

In this paper a spray behaviour based on digitalised images is presented for a specific fluid the working range of a spray, the main parameters indicating the spray performances, e.g DeLavan data sheet, cone angle, supply pressure and mass flow rate are defined. Such parameters determine the spray behaviour but they don’t give any answer about the main parameter whose variation determines a different pattern of the atomization. To atomize a high viscous fluid and to achieve an efficient lubrication, the drops of the spray jet have to coalesce and form a continuous liquid film in a very short time. To achieve this kind of behaviour the spray has to generate the droplets in a particular range of diameters so, their deformation after the impact, have to minimize the coalescence time. In this paper the behaviour of a pressure swirl spray working with a high viscous fluid its spectra of droplets and a numerical simulation of the internal flow are presented.

Experimental Study of Airless Spray Jet Breakup at Elevated Temperature and Pressure

The presented research work was focused onto the understanding of the jet behavior of the sprays of heated water during the low pressure atomization process. This task was accomplished using an in-house built intermittently forced liquid spraying system capable of lowering the liquid viscosity and surface tension to a desired value and then atomizing it into a full cone spray patterns in the ambient air surrounding. Using a high speed camera, the jet breakup dynamics were visualized as a function of system input parameters. The analysis of the grabbed images confirmed the strong influence of these processing parameters on full cone spray characteristics. It was also predicted that heated liquids generate a dispersed spray pattern by utilizing the partial evaporation of the spraying medium that is the induction of thermal energy enhances the jet disintegration ability. The spray cone width and angle did not vary significantly whereas the Weber and Reynolds numbers along with other nozzle flow parameters showed an appreciable response to the load pressure and temperature at early stages of water injection. The ultimate objective of the work was to understand and control the airless spray jet breakup mechanism under reduced load pressure and high water temperature.

Synthesis and Characterization of BaTiO<sub>3</sub> Fine Powders by Pulse Jet Spray Pyrolysis

BaTiO3 precursor powders were synthesized by two types of pulse jet spray pyrolysis1000 and 2000 kcal/h typesusing an aqueous solution of metal salt. All as-prepared powders crystallized to the cubic and other phases. However, the powders almost reached the tetragonal phase through calcination at 900 °C in air for 2 h. The crystallinity of the powders obtained from 2000 kcal/h type pyrolysis was higher than those obtained from the 1000 kcal/h type. When Ba (NO3)2 was used, nanoparticle formation at an average particle size of approximately 150 nm, with a narrow size distribution, was observed. The relative density of the sintered body was 87 %. The relative dielectric constant of the BaTiO3 body was 1450, and its tanδ value was 0.017 at room temperature.

Effects of Turbulence, Evaporation and Heat Release on the Dispersion of Droplets in Dilute Spray Jets and Flames

The dispersion characteristics of a selection of non-evaporating non-reacting, evaporating non-reacting, and reacting dilute spray jets issuing in ambient air (Gounder et al, Combust Sci Technol 182:702–715, 2010; Masri and Gounder, Combust Flame 159:3372–3397, 2010) and in a hot coflow (Oloughlin and Masri, Flow Turbul Combust 89:13–35, 2012) are analysed. Other than the cases found in those contributions, two additional sprays of kerosene have been investigated in order to systematically study the effects of evaporation. The burners are well designed such that boundary conditions may be accurately measured for use in numerical simulations. The dynamics and dispersion characteristics are analysed by conditioning results on the droplet Stokes numbers and by systematically investigating changes in dispersion and dynamics as a function of carrier air velocity, liquid loading, ignition method, and location within the flame or spray jet. The tendency for droplet dispersion defined by the ratio of radial rms velocity to axial mean velocity varies significantly between reacting and non-reacting flows. However, dispersion is found to be largely unaffected by evaporation. The total particle concentration, or number density of droplets within the spray has also been used as a direct measure of spray dispersion with the effect of evaporation on a turbulent polydisperse spray being isolated by investigating acetone and kerosene sprays with similar boundary conditions. The rate of change of droplet size with radial position is almost identical for the kerosene and acetone cases. The dispersion characteristics, closely related to the ‘fan spreading’ phenomenon are dependant on the carrier air velocity and axial location within the spray.

Acetylene Ignition Process in Combustion Thermal Spray

The acetylene ignition process in combustion thermal spray is typical of a laminar diffusion jet. It has all the features of a free jet. The aim of this research is to obtain the detail sparking ignition evolution process and the chemical reaction time scale and calculate the critical radius and minimum energy input required to produce a self-propagating flame in an acetylene fuel jet. Experiments are carried out by using a unique high-speed continuous CCD camera. The results show that the full sparking ignition time needs about 8 ms and this time scale can be used in the calculation of the flame flow fields in the combustion thermal spray jet.