Spray Penetration Research Articles

An investigation of the effect of chamber temperature on macroscopic spray characteristic under GCI engine conditions

Spray characteristics play an important role in the application of gasoline compression ignition (GCI) engines because it affects engine performance as well as engine design. In this study, the influence of temperature on the non-vaporizing spray process was evaluated through the experimental process on the constant volume chamber (CVC) with simulated conditions of the GCI engine. The experimental matrix was constructed by varying key factors, including chamber temperature, fuel injection pressure, and chamber gas density. The CVC with built-in heaters allows for temperature variations at 323 K, 398 K, and 423 K. To accommodate low load conditions, the fuel injection pressure is varied between 50 MPa and 110 MPa. Simultaneously, chosen variations of gas density, including two levels of chamber density are selected at 15 kg/m3 and 30 kg/m3 respectively. In addition, the injector angles are arranged at 90° (vertical) and 180° (horizontal) to create an overview of the spray characteristics for the case study of GCI engine conditions, viable for future studies using a constant-volume combustion chamber (CVCC), or even rapid compression engine machine (RCEM) in which the injector is commonly set horizontally. The gasoline blended with biodiesel by volume percentage consisting of 80% gasoline and 20% biodiesel was used as the main fuel in this study, namely the GB20 blend. The results of the spray characteristics collected through the images of the spray process based on the Schlieren optical method and the highspeed camera, consisting of the spray evolution and penetration length, spray penetration rate, spray area, as well as the spray cone angle are investigated. The difference in the spray process is denoted as the chamber temperature is increased. The spray penetrates to the chamber wall limit more quickly at elevated temperatures. The results were recorded as a decrease in impingement time by 12% and 9.5%, respectively, at the injection pressure of 50 MPa together with an ambient gas density value of 15 kg/m3. The cone angle of the spray tends to reduce by approximately around 3° to 10° in all experimental cases when the chamber temperature is high. However, when entering the post-phase at 450–600 μs, cone angle differences are negligible during the injection reaching the stable phase.

Experimental study of the lubricant-refrigerant flow in a rotary compressor

Lubricant oil is used in the rotary compressor to lubricate the bearings and to seal the clearance of sliding parts. However, a portion of lubricant oil in the upper cavity will ultimately exhaust from the compressor through the discharge tube, carried by the refrigerant. The accumulated lubricant in the tubes will deteriorate the heat transfer of the condenser and the evaporator, resulting in decreased efficiency. This work focuses on characterizing the pathway of lubricant droplets in a rotary compressor. In-situ measurements include lubricant spray penetration velocity at different phases in a rotating cycle and droplet velocities at different locations, i.e., lower cavity, above the rotor/stator, and at the discharge tube level, different frequencies, and different pressures via time-resolved shadowgraph. Particle Image Velocimetry (PIV) and Optical Flow Velocimetry (OFV) are adopted to quantify the velocities of spray and droplets. The penetration velocity of the lubricant spray in the lower cavity, horizontal swirling velocity above the rotor/stator and at the discharge tube level, and the vertical recirculation velocity above the rotor/stator are characterized. The results support a droplet pathway model in the rotary compressor that can guide the optimization of the next-generation rotary compressors.

Comparative experimental study on macroscopic spray characteristics of various oxygenated diesel fuels

AbstractUnder high ambient pressure (5 MPa) and different injection pressures (90, 120, and 150 MPa), a high‐speed imaging technique was carried out to comparatively investigate the macroscopic spray characteristics of diesel with three different types of blended fuel in a constant volume chamber. The oxygenated fuels were n‐butanol (B), pine oil (P), and 2,5‐dimethylfuran (DMF). All their blending ratio with diesel were 20%. Results showed that less viscosity could be improved the spray characteristics of the fuel in the range of experimental conditions. Then, the tested fuels had a longer penetration and a greater spray area with increasing the injection pressure from 90 to 150 MPa. On the other hand, the percentage increases in the mean spray cone angle of D100, B20, P20, and DMF20 were 3%, 4.4%, 2.4%, and 2.9%, respectively. At the same experimental condition, the spray penetrations of DMF20 and P20 were larger than that of D100, but the spray penetration of B20 was basically similar to D100. Besides, the performance of the spray cone angle and spray area were D100 < B20 < P20 < DMF20. In addition, the comprehensive influence was that blending oxygenated fuels would be a benefit for developing fuel atomization and the air–fuel mixture of conventional diesel fuel.

Effect of Pilot Injection with Various Starts of Second Injection Command (SOIC2) and Fuel Injection Pressures on Gasoline Compression Ignition Combustion

This experimental study was conducted using a single-cylinder compression ignition (CI) engine with a pilot injection strategy to determine the effect of fuel injection pressure and the timing of the second start of injection (SOI2) on combustion and emission characteristics. This experiment used a mixture of 80% commercial gasoline (G80%) and 20% soybean biodiesel (B20%), by volume. The pilot injection strategy was applied with varying SOI2. Meanwhile, the first start of injection (SOI1) was constant at -350° ATDC and 900 bar fuel injection pressure. A range of fuel injection pressures from 400 to 900 bars and varied injection timing from -44 to -36 CA ATDC was applied at SOI2 to analyze the effect of injection timing and injection pressure on combustion characteristics and emissions. The increasing fuel injection pressure of GB20 in early injection timing will cause a longer ignition delay. The autoignition resistance of GB20 and the improvement of spray velocity enhance the wall wetting probability, consequently reducing the autoignition capability as fuel deposits were formed in the cylinder wall vicinity. Closer injection timing to TDC inhibits spray penetration due to higher room pressure and density, causing lower ignition delay. For GB20, 700 bar fuel injection pressure became the turning point in the ignition delay due to a lower fuel penetration velocity as a higher fuel injection pressure was applied. NOx emissions were identified as a sign of high temperature produced during combustion. The lowest CO2 emissions and the longest ignition delay appeared at the 700-bar injection pressure. Because incomplete combustion resulted in fuel deposits in the vicinity of the cylinder and temperature decrease, injection timings earlier than 40°CA BTDC initiated low thermal reaction (LTR) conditions, causing a temperature decrease during combustion.

Experimental investigation on effect of gas/spray interactions on transient diesel spray behaviors

The ever-increasing rail pressure in diesel engines may cause the injection induced shock waves. In the present study, different gases (N2 and CO2) were used as the ambient mediums in order to understand the effect of shock waves induced by the high-speed jets on the near-field spray penetration. The tests were carried out in an optically-accessible constant volume vessel and a single-hole diesel injector was used. The injection pressure ( Pinj) ranged from 80 to 150 MPa and the ambient density ( ρambient) are 11.25, 22.52, and 33.81 kg/m3, respectively. Schlieren imaging was used to capture the shock waves ahead of the sprays with a frame speed of 100,000 fps and high-speed imaging was used to capture the spray penetration evolution with a frame speed of 300,000 fps in order to provide sufficient high temporal and spatial resolutions of the spray development. Shock waves can be observed under CO2 atmosphere over all the tested conditions and almost invisible under N2 atmosphere. The timings of occurrence and detachment of the shock waves are advanced with the increase in ρambient, but less sensitivity to Pinj. The difference in penetration lengths for N2 and CO2 atmosphere are not consistent as Pinj and ρambient varied, indicating the complicated role of shock waves in influencing the spray behaviors. Several mechanisms for the generation of shock waves were discussed, as well the physical meaning of the timing to the peak velocity of the spray tip with breakup time.

Experimental study of combustion process of NH3 stratified spray using imaging methods for NH3 fueled large two-stroke marine engine

To achieve greenhouse gas emission reductions from the maritime sector, there is a growing demand for the development of NH3 fueled marine engines. Since NH3 is difficult to ignite and burn, it is valid to assist the NH3 combustion by a supporting fuel, which is easily ignited and burned. A new NH3 spray combustion concept for a large two-stroke marine engine has been proposed, which is a “three-layer stratified fuel injection comprising supporting fuel / liquid NH3 / supporting fuel (i.e., NH3 stratified injection)”. The advantages of the NH3 stratified injection concept are the symmetrical combustion support effect in the spray axis at important timing (ignition and late combustion). The supporting fuel used was n-hexadecane (nC16H34, cetane). The characteristics of the NH3 stratified spray under non-combustion conditions were investigated in an optically accessible constant volume combustion chamber using a reflective shadowgraph imaging system. The spray penetration length and the spray cone angle were similar to those of the 100% nC16H34 spray and typically estimated equations. Moreover, the combustion process of an NH3 stratified spray was investigated using high-speed direct imaging. The flame lift-off position moved downward and the rapid combustion by the third layer was different compared to those of the 100% nC16H34 spray. The burnt gas lump was confirmed to have initially played an important role in the flame lift-off position. The rapid combustion stems from the multipoint ignition, flame propagation, and downward movement of the flame by the jet stream. Additionally, the NH3 combustion in the NH3 stratified spray was investigated using imaging spectroscopy. The spectra of chemiluminescence revealed that the NH3 combustion progressed after forming the initial burnt gas lump, and the NH2* ammonia α-band was observed in the combustion area. Consequently, the combustion process of an NH3 stratified spray was clarified from these experimental results.

Comprehensive assessment of methanol as an alternative fuel for spark-ignition engines

A promising pathway to defossilize the operation of spark-ignition engines is to use methanol as a fuel. This clean alternative liquid energy carrier offers major efficiency and emission benefits compared to gasoline. Its high knock-resistance and high heat of vaporization allow knock-free operation at high compression ratios while maintaining low emissions of nitrogen oxides. In addition, it is the simplest alcohol to synthesize and the distribution infrastructure for existing liquid fuels can be used. Previous research on mixture formation and combustion of methanol in passenger car sized spark-ignition engines is limited, reported on various experimental configurations, and mainly focused on one particular aspect. This study sets out to provide a coherent evaluation of the mixture formation and performance of methanol in a spark-ignition engine in comparison to gasoline by successively addressing and combining fundamental and optical spray measurements, engine experiments and complementing numerical analyses all with matching boundary conditions for these aspects. First, a theoretical analysis regarding the primary spray break-up behavior was performed using methanol and the gasoline surrogate iso-octane, which showed a comparable atomization performance between the two fuels. This theoretical result was then experimentally validated under realistic engine operating conditions on a low-pressure chamber by means of shadowgraph imaging. These investigations showed no notable differences in spray penetration length and spray angle between methanol and gasoline under the same boundary conditions. However, under realistic engine operation, the spray penetration length of methanol increased by up to 64.5% due to the increased injection duration required because of its lower energy content. In a next step, methanol was experimentally studied on a thermodynamic single-cylinder research engine with a compression ratio of 10.8. Using the same fuel injector, the combustion and emission behavior was investigated in comparison with gasoline. A load variation at an engine speed of 2500 1/min and a variation of the relative air/fuel ratio at the same engine speed and a net indicated mean effective pressure of 16 bar were performed. Depending on the engine load, methanol achieved 7%–24% higher net indicated efficiencies and a 9 bar higher maximum load compared to gasoline. At lean-burn operation, methanol not only enabled higher net indicated efficiencies exceeding 45%, however, also an extended lean-burn limit of 0.1 units. The experimental engine investigations were complemented with 0D/1D simulations, which showed that especially the wall heat transfer and the burn duration are significantly lower in the case of methanol. Finally, 3D computational fluid dynamics simulations were performed using a newly developed methanol spray model which showed that an increased fuel mass impinges the combustion chamber walls with methanol. However, toward the end of compression, the methanol wall film dropped to the level of gasoline.

Schlieren and mie-scattering visualization of an evaporating spray under marine diesel engine conditions

Due to the critical influence on combustion, extensive research has been carried out to deepen the understanding of diesel spray evolution. However, for the greater share of land-based diesel engines, most of the studies have focused on the injectors with small nozzle diameter and rare studies can be found on marine diesel engines, which has a larger mass flow rate and longer injection duration with large nozzle diameter. In this study, the influence of injection pressure, ambient temperature, ambient density and nozzle diameter on spray morphology for medium speed marine diesel engine injectors (with nozzle diameter up to 0.53 mm) were investigated under various non-reacting but evaporative conditions. The experiments were performed via a highly enhanced constant volume chamber (highest temperature of 900 K and highest pressure of 8 MPa) with an optical window diameter of 205 mm. Liquid and vapor penetration of sprays were recorded by Mie-scattering and schlieren optical configurations respectively. Results show that the vapor penetration velocity is mainly affected by injection pressure. Ambient temperature has the most significant effect on liquid penetration length, but less effect can be found on the vapor penetration velocity. Given the obvious deviation from heavy duty engine sprays, the empirical correlations for liquid penetration length and vapor spray evolution are updated to fit the spray characteristics of medium speed marine diesel engine injectors, which is helpful to understand the spray behavior for large nozzle diameter injector under marine diesel engine conditions.

INFLUENCE MECHANISM OF STAGNATION-POINT FLOW ON LIQUID-PHASE SPRAY PENETRATION LENGTH UNDER ENGINE-LIKE CONDITIONS

Formulation of liquid-phase spray penetration length (LPL) is one of the basic research works of direct injection (DI) engines. To predict the spray evolution and LPL in the limited space more accurately, the diffused background-illumination extinction imaging (DBI) technology and highspeed schlieren method were employed to detect the liquid- and vapor-phase spray development in a constant volume combustion chamber (CVCC). The experimental results show that the LPL of the impinging spray is significantly smaller than that of the free spray when the LPL is close to the impinging distance. When the LPL is much smaller than the impinging distance, the LPL of impinging spray is the same as that of free spray. Furthermore, based on the CFD simulation and the stagnation-point flow theory, the spatial distribution of velocity, pressure, and density at the near-wall surface was analyzed in detail. Due to part of the spray kinetic energy was converted into potential energy, creating a sharp increase in pressure and density near the stagnation point, which suppressed the movement of fuel droplets, resulting in a significantly smaller LPL. Moreover, a novel LPL prediction model is introduced, which considering the inhibiting effect of wall on spray penetration and demonstrates enhanced predictive capability of experimental results.

MACROSCOPIC SPRAY CHARACTERISTICS OF GASOLINE, METHANOL, AND ETHANOL IN DIRECT INJECTION SPARK IGNITION ENGINE-LIKE CONDITIONS

In recent decades, stringent emission norms have been enforced upon the engine research community and OEMs to encourage them to develop new spark ignition engine technologies, such as variable valve lifts, turbocharging, and direct injection spark ignition (DISI) engines. For further development, greater control of parameters such as in-cylinder air motion, spray characteristics, injection, and ignition events is required. Spray characterizations are crucial for understanding the mixing phenomena in heated and pressurized engine combustion chamber conditions. Spray pattern, fuel injection pressure (FIP), rate shape, and thermodynamic conditions of the combustion chamber play a vital role in the mixture preparation. The present study uses Mie-Scattering techniques to examine spray structures of fuels like methanol and ethanol and compare them to gasoline, which is of great interest to DISI engines. Three different temperatures of 50, 100, and 200°C and two chamber pressures, 4 and 8 bar, are considered to simulate typical engine-cylinder conditions. It is observed that the initial chamber conditions greatly influence the spray structure. Spray collapse is lesser for alcohol than gasoline. Three semi-empirical models for predicting spray penetration are analyzed: Dent, Hiroyasu and Arai, and Arrègle. These models could not differentiate between the test fuels, particularly methanol and ethanol, for predicting spray penetration length. The degree of deviation in predictions is the lowest in the Hiroyasu and Arai model and the highest in the Dent model. Spray penetration length increased with an increasing FIP regardless of ambient conditions; however, the spray penetration length decreased with increasing chamber pressure.

SIMULATION OF AMMONIA SPRAY UNDER BOTH NORMAL EVAPORATING AND SUPERHEATED CONDITIONS

A predictive three-dimensional Eulerian-Lagrangian framework for ammonia spray is suggested, and its evolution characteristics under both normal evaporating and superheated conditions are unraveled. First, a simplified boundary model considering the effects of superheated fluid behaviors within the nozzle on the injection velocity and angle was proposed. The real vapor-liquid equilibrium theory is applied in the evaporation model to improve the prediction accuracy of the phase change. An explosion model with the homogenous nucleation theory was used to simulate the burst process. Then, the spray experiment for the liquid ammonia under varied conditions was conducted, and the high-speed diffused back illumination and schlieren approaches were adopted to measure the spray evolutions. Following that, the simulation results were verified against the experimental data under both normal evaporating and superheated conditions, and good agreements indicated that the suggested framework was feasible to accurately and efficiently simulate the evolutions and morphology of ammonia spray. Finally, the transient evolution characteristics of ammonia spray under various conditions were discussed. The heavy cooling effect of ammonia evaporation makes the initial fuel temperature have a notable effect on its spray penetration and expansion.

NUMERICAL STUDY OF DIRECT INJECTION SPRAY BEHAVIOR OF GASOLINE AND METHANOL-GASOLINE BLENDS UNDER SPLIT-INJECTION STRATEGY IN ENGINE-LIKE CONDITIONS

Several studies have shown that the split-injection strategy has improved the shortcomings of the high particulate matter emissions and cycle-to-cycle variations in homogeneous and stratified combustion modes of gasoline direct injection (GDI) engines. However, the spray behavior under the split injection strategy is poorly understood. This study uses computational fluid dynamics (CFD) simulations in Converge software to investigate the spray characteristics of gasoline and methanol-gasoline blends under a split-injection strategy. The simulation studies were performed for a multihole GDI injector in a constant volume spray chamber, replicating the ambient conditions similar to a GDI engine's homogeneous and stratified combustion modes. Appropriate models for simulating different spray phenomena, such as spray breakup, collision, and coalescence, were used. The CFD model was validated using the experimental spray penetration length provided in the engine combustion network database. The results showed that the split-injection reduced the Sauter mean diameter (SMD) of fuel spray droplets and liquid fuel mass content than a single injection case. The dwell time of 2 ms was found suitable for homogeneous mode conditions, while its effect was insignificant in stratified mode conditions. Further, a split ratio of 80:20 resulted in smaller SMD during the injection period and a higher fuel evaporation rate. The effect of methanol addition was also explored under the split-injection mode. M85 showed higher deviations in the liquid spray penetration, SMD, and liquid spray mass content than G100.

POST PROCESSING METHOD FOR SIMULATED LAGRANGIAN SPRAY FIELD BASED ON MIE SCATTERING THEORY

Numerical simulation and experiment are the two main methods in the investigation of spray and atomization. Some crucial parameters of simulation models are supposed to be calibrated using corresponding experimental data. However, direct comparisons between simulation data and experimental results might be confusing when focusing on spray boundaries or penetration, as the light scattering physics during imaging is always likely to be ignored in computational fluid dynamics (CFD) post-processing. In many cases, CFD provides invisible droplets, resulting in variance in the boundary confirming process. Previous studies discussed backlit conditions in Euler-based simulations to identify spray boundaries, but for most commonly used Lagrangian-based simulations, which are often coupled with Mie scattering experiments, this topic remains undiscussed. In Lagrangian-based methods, droplets are treated as discrete particles, where scattering plays a more crucial role. In this study, light intensity analysis based on Mie scattering theory and intensity integration focusing on Lagrangian field has been presented, aiming to adjust simulation data of spray coincides with Mie scattering image as much as possible on the theoretical base. It is found that particle size and in-parcel numbers are related to the scattering intensity of droplet particles. the correlated CFD data using Mie scattering theory are tested to be theoretically similar with Mie scattering imaging results compared with raw simulation data, making the comparison between datasets reasonable, which makes adequate preparations for the calibration of spray models.

AERATED CIRCULAR AND ELLIPTICAL LIQUID JETS IN A GASEOUS CROSSFLOW

In this study, the atomization of an effervescent atomizer with an elliptical and circular orifice was investigated experimentally in the gaseous crossflow. The shadowgraph technique was used to visualize the near field of the spray atomization. To measure the spray penetration height in crossflow, image processing was performed on the shadowgraph images based on two different approaches: (i) a threshold analysis of average spray images and (ii) standard deviation images of spray. By comparing these two approaches, it is found that the penetration heights obtained from the standard deviation images were much higher since these images were able to capture small droplets more accurately. Moreover, based on the standard deviation images of spray, an empirical correlation for the spray penetration height was developed as a function of gas-liquid mass flowrate ratio, liquid-air momentum flux ratio, orifice aspect ratio, and downstream location. The laser diffraction technique was used to analyze the particle size of the aerated elliptical and aerated circular jets in a gaseous crossflow. For each orifice shape, the effect of gas-liquid ratio and downstream location on the Sauter mean diameter (SMD) was studied. The results show that the aerated circular jet penetrates higher into the gaseous crossflow than the aerated elliptical jet. Besides, the aerated circular jet in crossflow mainly generates smaller drop sizes compared to the aerated elliptical jet.

VALIDATION OF A STOCHASTIC BREAKUP MODEL FOR TURBULENT JETS IN HIGH-SPEED CROSSFLOW: ASSESSMENT OF TURBULENT INTERACTIONS AND SENSITIVITY TO BOUNDARY CONDITIONS

Improving the mixing of fuel and air by injecting a turbulent liquid fuel jet into a high-speed cross-flowing gas can reduce the emissions of gas turbine applications. To facilitate and hasten the development of such low-emissions technologies, accurate predictions of the spray characteristics are needed. The objective of the present study is to validate the predictive capabilities of a stochastic breakup model for turbulent transverse jets over a wide range of representative pressures and atomization characteristics. The effect of turbulence modeling is also assessed to provide accurate and computationally less expensive Eulerian-Lagrangian transient approaches. To do so, the predictions made with the large eddy simulation (LES) approach for different subgrid-scale (SGS) models and with the synthetic eddy method (SEM) are compared to the ones made using the unsteady Reynolds-averaged Navier-Stokes (RANS) approach with and without a turbulent dispersion model. The sensitivity of the numerical methodology to the upstream velocity profile, pressure, and momentum flux ratio were also assessed. Properly accounting for the upstream gas velocity profile was found to be critical to ensure accurate predictions of the spray characteristics. The unsteady RANS (URANS) turbulent approach coupled with the turbulent dispersion model showed good agreement with experimental data, but the LES approach tends to overpredict the spray penetration and underpredict the Sauter mean diameter (SMD). This could be due to the lower turbulent interactions it predicts, which may lead to lower momentum transfer between the phases.

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF DUCTED SPRAY WITH DUAL INJECTION STRATEGIES

Ducted fuel injection (DFI) is a newly established technology showing great potential in breaking the soot/NOx trade-off. Multiple-injection strategy is also seen as a possible way to reduce soot and NOx emissions simultaneously. However, the applicability of these approaches is not fully understood. The present study investigated the spray characteristics of DFI technology coupled with a dual-injection strategy. Results showed that during the injection interval (the interval between two injections), ambient gas continues to flow into the duct due to the pressure difference between the duct inside and outside, which increases the velocity of the second injection. The spray penetration length development of ducted spray is faster than that of free spray in both the first and the second injection events. During the first injection, the distribution of the equivalence ratio of ducted spray is more uniform than free spray, and the peak value of the equivalence ratio of ducted spray is lower than that of free spray. Compared to the first injection, in the second injection, when the radial equivalence ratio distribution of ducted spray is equivalent to the that of free injection, the path of spray traversed is shorter. These indicate that DFI technology and dual injection strategy couples well in case of spray and mixing process.

MODIFICATION OF AMULTIHOLE INJECTOR TO A SINGLE-HOLE INJECTOR AND SPRAY CHARACTERISTICS OF THE MODIFIED INJECTOR BY TWO DIFFERENT IMAGING TECHNIQUES

In the present days, almost all the diesel engines are fitted with multihole injectors. Spray characterization of the injectors by different optical measurement techniques is very important to under-stand the air-fuel mixing and combustion procedure inside the cylinder. Instead of characterization of the dense sprays from a real multihole diesel injector, often a single plume is used to study the spray parameters. In the present work, spray characteristics are studied for a multihole injector with all nozzle holes open and with a single hole open conditions. Experiments have been conducted in a constant-volume, high-pressure, and high-temperature chamber with various injection pressures and at various ambient conditions. A high-pressure common rail injector with six holes is considered for the study. The penetration and cone angle of the spray from each hole are measured, and the hole-to-hole variation is studied. It has been observed that hole-to-hole variations with respect to spray penetration are prominent in low chamber pressures and injection pressures at the initial stage of injection, though they are minimal at later stages of injection. After that, five holes of the injector are blocked by microwelding, and the remaining single plume was studied and the results compared with the original multiplume spray. The study shows that the penetration length and cone angle of the single plume match well with that of the multiplumes at all chamber pressures and injection pressures. Later, the spray from the modified single-hole injector was characterized by two different imaging techniques, Mie scattering and diffused backlit imaging (DBI), to compare the penetration length and cone angle measured by the two imaging techniques. It is seen that the differences in penetration lengths by two imaging techniques are negligible, whereas the cone angles are greater in the case of backlit shadow imaging, particularly at higher temperatures.

COMPUTATIONAL SIMULATION OF THERMAL AND CHEMICAL BEHAVIOR DURING THE COMBUSTION PROCESS IN DIESEL ENGINE

The purpose of this paper is the modeling and simulation of one of the most challenging processes in internal combustion engines, combustion. The first objective was to analyze and study the thermodynamic and fluid dynamic behavior within the combustion chamber. Since detailed chemistry requires a great deal of time and computer resources, our aim is to implement a simple and accurate model to simulate and predict the combustion process. To this end, numerical methods have been developed through the techniques of Computational Fluid Dynamics (CFD). In addition to the basic equations of mass, momentum and energy, the mathematical model developed included equations of state, a turbulence model and a model of the spraying mechanism. For chemical behavior and pollutant formation, we developed a new chemical model based on the Intrinsic Low-dimensional Manifold (ILDM) and homogeneous reaction methods that automatically reduces detailed chemistry. Kiva CFD software is used as the solver for all models developed. The analysis of the results shows the importance of swirling and turbulent motions for spray penetration, ignition, and flame propagation. The results for NO x and soot formation, as the main pollutant emissions from the diesel engine, showed different behavior for their formation conditions. These results also show that there is good agreement within the mechanism used to make their predictions. The credibility of the built model is increased by comparing the pressure results with the experimental ones. Keywords: Combustion, Diesel Engine, Modeling, Computational Fluid Dynamics, Pollutant Formation DOI： https://doi.org/10.35741/issn.0258-2724.58.2.20

提高航空喷雾雾滴穿透性的方法和自动系统研究

When UAVs apply a pesticide at different speeds, droplet deposition area and canopy vortex area are not at the same location, which prevents droplets from depositing on the backside of leaves and lower part of plants in canopy vortex, and affects spray quality and pests and diseases control effect. To shorten the distance between the two areas and improve droplet penetration, a method for adjusting nozzle inclination angle based on droplet force analysis and tests was proposed in this paper. According to the obtained model, an automatic nozzle angle adjustment system was developed from hardware and software. The experimental results showed that the number of droplets deposited on the entire leaf increased by 21.58% when UAV spraying with the system mounted. The average number of droplets on the front side of the leaf increased by 14.44% while 66.05% was on the backside of the leaf with the system mounted. This indicates that the method and system proposed have a significant impact on improving the UAV spray penetration.

Experimental and feasibility study on nano blended waste plastic oil based diesel engine at various injection pressure: A value addition for disposed plastic food containers

Fuel obtained from waste plastic has been used in this study due to the lavish consumption, and non-stop price hiking made the researchers focus on finding a suitable substitute for conventional fuel. The plastics were non-biodegradable, and also its continuous usage in our daily life together created awareness about waste plastic management among us. With this, plastic oil could be a promising alternative fuel and also solves the issue of seating waste plastics in landfills. Even though plastic oil has a closer calorific value and viscosity to diesel, its volatility is less than diesel. In order to improve its volatility, a titanium dioxide oxide nanoparticle of 50 ppm, 100 ppm, and 150 ppm was doped. A single-cylinder diesel engine's performance, emission, and combustion phenomena were tested with nano blended waste plastic oil at three different fuel injection pressure of 210, 230 and 250 bar, respectively and the results were analyzed. An improvement in engine characteristics was recorded for nanoparticle blended fuels. High nozzle opening pressure improves the spray penetration inside the engine cylinder, promoting the combustion quality. The study concluded that blending 150 ppm Titanium-dioxide with waste plastic oil would be a suitable alternative for diesel engines operating at 230 bar of injection pressure.