Schematic of the optical setup used with high-speed camera (a), far-field microscope (b), mirror (c), transparent nozzle holder (TNH) (d), diffuser plate (e), focusing lens (f), collimator (g), optical light guide (h), diode laser (i) and injector (j). The dashed line represents the optical axis. Note that the spray chamber surrounding the TNH is not illustrated.

Schematic of the optical setup used with high-speed camera (a), far-field microscope (b), mirror (c), transparent nozzle holder (TNH) (d), diffuser plate (e), focusing lens (f), collimator (g), optical light guide (h), diode laser (i) and injector (j). The dashed line represents the optical axis. Note that the spray chamber surrounding the TNH is not illustrated.

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To further increase the efficienc y and decrease emissions of large two-stroke marine Diesel engines, the understanding of the fuel injection, spray breakup and the resulting combustion plays a vital role. Investigations have shown that the strongly asymmetrically and eccentrically arranged nozzle bores of the fuel injectors can lead to undesirable...

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... TNH is designed to visualize the in-nozzle flow using a line-of-sight optical measurement technique like Shadowgraph imaging, where a light source illuminates one side of the transparent nozzle and an imaging system is installed on the other side. A schematic of the optical setup used is depicted in Fig. 4 where a simplified drawing of the fuel injector (j) together with the mounted TNH (d) is depicted as well, indicating the proportions. The dashed line indicates the optical axis. The setup used consisted of a Cavitar Cavilux Smart diode laser (i) emitting at a center wavelength of 640 nm together with a Questar QM100 far-field ...
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... approximately only 0.1 N. The simulation results fit the experimental data well for nozzle type N101 while predicting a slightly lower value for the eccentric nozzle N104 and a slightly higher value for the angled nozzle N105. The standard nozzle N101 has the smallest discrepancy with less than -2% compared to the experimentally measured value. Fig. 14 , 15 , and 16 show the experimentally acquired in-nozzle flow images compared to the CFD simulation results. To create CFD images that are qualitatively comparable to the experimental images, a time frame has been defined for statistical examination after the simulation has reached a quasi-steady-state. This allows a comparison to the outcome of the ...
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... images in Fig. 14, 15 , and 16 depict the acquired in-nozzle flow of the nozzles N101, N104, and N105, respectively. Similar to the experimental data presented in chapter 4.1, Fig. 9 , the first image shows the background (i), which is the transparent nozzle filled with Diesel fuel but without fuel mass flow. The second image (ii) shows a single acquisition ...
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... standard nozzle design N101 with the centrically, 90 ° arranged nozzle bore ( Fig. 14 ) is supercavitating as the gaseous phase reaches the nozzle bore exit [63] . The fuel flow enters the main bore from the left side and hence the cavitation in the nozzle bore on the left side is more distinctive. ...
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... presence of a coherent film-like vapor layer on the upper and lower walls of the bore reach the nozzle bore exit and indicate a pattern of supercavitation. Again, simulation and experimental results are in good agreement ( Fig. 14 iv)). ...

Citations

... Cavitation CFD analysis has not only been applied to turbomachine problems, but different related areas of fluid mechanics have also studied the negative effects of these phenomena, such as [44][45][46][47][48]. Cavitation analysis in turbomachines, through numerical methods have been mostly applied to Francis, Pelton, and Kaplan turbines [49][50][51][52][53]. Unfortunately, only a few studies have evaluated cavitation in turbopumps. ...
Article
Axial turbines are machines widely used in different engineering applications. Due to their constructive characteristics, they must have a space between the rotor blades and the turbine casing, called tip clearance. Unfortunately, this gap allows a part of the fluid to leak from the pressure side to the suction side of the rotor blades. This leakage is undesirable and represents an energy loss. A way to avoid part of this loss is through the use of desensitization techniques. Although the use of these techniques is widely known, no studies in the open literature have evaluated these techniques in hydraulic turbines. This work presents a numerical analysis of squealer desensitization techniques applied in a hydraulic axial turbine. The turbomachine under study is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME). Numerical simulations were performed using CFX v.19.2 software, and computational meshes were generated in ICEM v.19.2 software. Initially, the computational model was validated, using the experimental results published by the National Aeronautics and Space Administration (NASA). A parametric analysis was performed considering the variation in squealer cavity depth and rim thickness. The study found that the squealer cavity depth has a greater influence on the stage performance than its rim thickness. The tendency is that the greater the cavity depth, the greater the stage efficiency. One of the squealer geometries analyzed allowed an average increased efficiency of 1.43%, over the entire turbine operational range. The results obtained also show that the application of the proposed geometries would enable the reduction in cavitation close to the trailing edge of the rotor blades. This result is extremely valuable, as it can impact the life cycle of the turbine.
... 8 Furthermore, the studies revealed that the change in the convergent angle has significant effects on flow characteristics and the generation of cavitation. 9 Hiroyasu 10 showed that liquid turbulence generated as a result of cavitation inside the injector nozzle plays an important role in atomization. He showed that even under a considerably high injection pressure, when cavitation does not take place inside the nozzle, the liquid jet does not atomize and the breakup length becomes longer. ...
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The impact of the in-flow characteristics inside the injection nozzle on atomization has been experimentally and computationally studied. Measurements are carried out using a transparent glass nozzle. Pulsed laser sheet with a synchronized charge-coupled device (CCD) camera and image processing, together with a particle image velocimetry (PIV) setup have been used as measuring techniques. Images and relevant image processing are used to visualize and quantify the rate of generation of cavitation bubbles inside the nozzle, the spray particle size distribution, and cone angle. Velocities inside and outside the injection nozzle are measured using PIV. The experimental investigation has been extended to include a wider range of the injection nozzle geometrical aspect ratios and working parameters. The computational model is a three-dimensional, two-phase, turbulent model to solve both the in- and out-nozzle flows. A novel coupling mathematical model is proposed for the definition of the probability density function of the issuing droplet size distribution, based on the in-flow developed conditions. A good agreement between both the experimental and computational results has been found under all conditions. According to both the experimental and computational results, it has been found that the onset of cavitation inside the injection nozzle, its location, collapse, and consequently the issuing spray configurations depend on the flow cavitation number, the nozzle geometrical characteristics, the liquid temperature, and the injection and back pressures. According to the quality of the obtained results from the model, it can be used to extend the study to cover a wider range of spray applications.
... In the research of marine injectors, increasing development of numerical simulation tests is observed. Balz et al. (2021) present the numerical and experimental investigation of cavitation in marine diesel injectors. They showed that experimental in-nozzle flow visualization had shown cavitation patterns in the nozzle bore. ...
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Purpose In the cylinders of a marine diesel engine, self-ignition occurs in a very short time after the fuel injection into the combustion chamber. Therefore, this paper aims to develop a model of diesel fuel spray for the early stage of fuel spray in the marine diesel engine. The main technical aspects such as nozzle diameter of the marine engine injector and backpressure in the combustion chamber were taken into consideration. Design/methodology/approach In this paper, laboratory experimental studies were carried out to determine parameters of fuel spray in an early stage of injection in the marine diesel engine. The optical measuring Mie scattering technique was used to record the fuel injection process. The working space was a constant volume chamber. The backpressure parameters in the constant volume chamber were the same as during the operation of the marine diesel engine. Based on the experimental studies and important Hiroyasu and Arai models of fuel spray presented in literature was proposed new model of fuel spray parameters for marine diesel injectors. Findings In this paper, the proposed new model of the two main parameters described fuel spray evolution”: new model of spray tip penetration (STP) and spray cone angle (SCA). New model propagation of fuel STP in time was included the influence of nozzle diameter and backpressure. The proposed model has a lower error, about 15%–34%, than the model of Hiroyasu and Arai. Moreover, a new model of the evolution over time of the SCA is developed. Research limitations/implications In the future research of fuel spray process must be taken influence of the fuel temperature. Diesel fuel has a different density and viscosity in dependence of fuel temperature. Therefore are predicted of the expansion about influence of fuel temperature, new model of fuel spray for a marine diesel engine. The main limitations occurring in the research are not possible to carry out the research while real operation marine diesel engine. Originality/value An experimental test was carried out for a real fuel injector of a marine diesel engine. Design parameters and fuel injection parameters were selected on the basis of the actual one. In the literature, SCA is defined as a constant parameter for the specific preliminary data. A new model for the early stage of fuel spray of SCA propagation in time has been proposed. The early stage of fuel spray is especially important, because in this time comes in there to fuel self-ignition.
... Examples are as followed. Balz et al. [3] in-text citation analysed the cavitation of a marine diesel nozzle. They adopted different methods like the volume of fluid-based numerical simulation, experiment, and homogeneous relaxation model to describe the rate at which the instantaneous quality and the mass fraction of vapor in a twophase mixture will approach its equilibrium value. ...
Full-text available
Article
The nozzle is a widely used device in daily life, such as water fountains to rocket engines. It is important to find out the influence of the position of the nozzle throat for the application or the design of the nozzle. To that end, the finite difference method was employed to solve the 1D Euler equations to obtain the flow inside the nozzle. To implement the method, an in-house python code was developed. The relationship among the velocity, pressure and density in the convergent-divergent nozzle flow was found. It is observed that: the velocity rose quickly along with the nozzle and reached the top before a rapid decrease; pressure remained constant initially, which eventually began to drop; density dropped steadily and had a turning point. Moreover, the influence of the nozzle throat position is investigated thoroughly. It is observed that the position of the nozzle throat influences the velocities at the nozzle exit. The faster the flow reaches the throat, the higher the velocity or Mach number at the exit boundary.
... Further works in the field of fuel injection involve [56], where the authors analyse transient phenomena of needle opening or needle closing with Large Eddy Simulation (LES), as well as the resulting atomisation patterns, in single hole or multi-hole diesel injectors of the Engine Combustion Network (ECN) database. Since then, the HRM model has been used for a variety of applications, including marine injectors for industrial RANS simulations [57] and attempts to devise an erosion metric criterion have also recently performed [58], whereas it has proven to have decent agreement against X-ray densitometry of the spray [59] or the internal flow [60]. ...
Article
Numerical predictions of the fuel heating and cavitation erosion location indicators occurring during the opening and closing periods of the needle valve inside a five-hole common rail Diesel fuel injector are presented. These have been obtained using an explicit density-based solver of the compressible Navier-Stokes (NS) and energy conservation equations; the flow solver is combined with two thermodynamic closure models for the liquid, vapour and vapour-liquid equilibrium (VLE) property variation as function of pressure and temperature. The first is based on tabulated data for a 4-component Diesel fuel surrogate, derived from the Perturbed-Chain, Statistical Associating Fluid Theory (PC-SAFT) Equation of State (EoS), allowing for thermal effects to be quantified. The second thermodynamic closure is based on the widely used barotropic Equation of State (EoS) approximation between density and pressure and neglects viscous heating. The Wall Adapting Local Eddy viscosity (WALE) LES model was used to resolve sub-grid scale turbulence while a cell-based mesh deformation Arbitrary Lagrangian–Eulerian (ALE) formulation is used for modelling the injector's needle valve movement. Model predictions are found in close agreement against 0-D estimates of the temporal variation of the fuel temperature difference between the feed and hole exit during the injection period. Two mechanisms affecting the temperature distribution within the fuel injector have been revealed and quantified. The first is ought to wall friction-induced heating, which may result to local liquid temperature increase up to fuel's boiling point while superheated vapour is formed. At the same time, liquid expansion due to the depressurisation of the injected fuel results to liquid cooling relative to the fuel's feed temperature; this is occurring at the central part of the injection orifice. The spatial and temporal temperature and pressure gradients induce significant variations in the fuel density and viscosity, which in turn, affect the formed coherent vortical flow structures. It is found, in particular, that these affect the locations of cavitation formation and collapse, that may lead to erosion of the surfaces of the needle valve, sac volume and injection holes. Model predictions are compared against corresponding X-ray surface erosion images obtained from injector durability tests, showing good agreement.
Article
The generation and development of cavitation in the flow channel inside the injector ball valve had been characterized using a high-speed visualization system. The flow field information was obtained by numerical calculation of the dynamic boundary conditions. The generation mechanism and distribution law of cavitation in the ball valve were analyzed. The results show that cavitation first occurs at the gap of ball valve and then the diversion hole and the outflowing control-orifice (OA); the low-pressure area created by the throttling effect is the main factor in causing cavitation; and the flow line and vortex have a significant impact on cavitation distribution. The flow state of the fluid in the diversion hole and OA has a direct and obvious effect on the cavitation in the ball valve chamber. In the case of inlet pressure 35 MPa, when cavitation is stable, the vapor volume fraction of 0.7–1.0 accounts for 9% of the ball valve chamber volume, 89% of the diversion hole and 13% of the OA, and in case of 15 MPa they are <1%, 87% and 14%.
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This study is experimentally exploring the feasibility of organic Rankine cycle (ORC) as a waste heat recovery (WHR) technology in internal combustion engines, aiming at improving engine’s power, fuel consumption and CO2 emissions. Exhaust gases of a heavy-duty diesel engine are used as heat source of the ORC system. However, as the engine’s operating conditions vary, powertrain performance changes substantially. Therefore and in order to provide a thorough overview, the system was tested at different engine points. The expansion machine is a custom-designed radial inflow turbine that is operating with NOVEC 649 as the working fluid. In order to assure a steady state testing, a thermal oil loop was installed between the exhaust gas and the ORC loop. For a robust study, the test results were compared with CFD ones. The coupled engine-ORC system presented an expansion power, turbine efficiency and thermal efficiency of 7.6 kW, 48% and 6.2%, respectively, when the turbine is running at maximum speed. The results also revealed that ORC systems have a promising influence in reducing the fuel consumption of diesel engine and providing extra power. Maximum percentages of improvements of BSFC and powertrain power were, respectively, 2.74 and 7.8% compared to engine without ORC.
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Spectral radiative transfer exists widely during application. Particle-containing medium is also called dispersed particulate medium, which may coexist the effects of non-uniform particle size distribution and dependent scattering, due to the reason of preparation, high concentration, aggregation, and so on. Ra-diative property calculation of dispersed particulate medium with neglecting the consideration of non-uniform particle size distribution and dependent scattering effects can induce significant errors. However, few radiative transfer studies on dispersed particulate medium have considered both the effects of dependent scattering and non-uniform particle size distribution. With the aim to calculate the radiative properties of dispersed particulate medium accurately, the idea of combining the dependent scattering effect with non-uniform particle size distribution effect is proposed by the authors. Multiple sphere T-matrix (MSTM) method combined with measured non-uniform particle size distribution is developed to calculate the radiative properties of dispersed particulate medium with the consideration of non-uniform particle size distribution and dependent scattering effects. Compared to conventional method, the method developed by the authors can decrease the maximum relative error between experimental data and calculation data from 49.87 to 8.82%, when calculating the radiative properties of dispersed particulate medium with the consideration of non-uniform particle size distribution and dependent scattering effects.
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