Spray Behavior Research Articles

Thermal-mechanical driven oxidation of NiCr-Cr3C2-BaF2/CaF2 composite coating at high temperature

Long-term oxidation behavior of thermal spray NiCr-Cr3C2-BaF2/CaF2 composite coating at 800 °C was studied. The existence of fluorides reduces the oxidation resistance of the composite coating. The originally stable BaF2/CaF2 segregated and oxidized under thermal-mechanical coupling action at high temperature. An oxide layer containing CaCrO4 and liquid BaCrO4 was formed on the surface of the coating through a series of reactions among BaF2/CaF2, NiCr and oxygen. Meanwhile, Voids and gaps were generated in the near surface of the composite coating.

A combined experimental–numerical study towards the elucidation of spray–wall interaction on step geometries

ABSTRACT In this research, a coupled numerical–experimental approach is employed to investigate the spray–wall interaction on step geometries with slope angles from 0° to 90° as well as impinging on and off the step geometry. Spray contours are used to compare the numerical and experimental results and, in general, good agreement between them is found. The results from the model are used to provide deeper knowledge about the macroscopic and microscopic behavior of the impinging spray influenced by step geometries. The numerical results provide a three-dimensional perspective that reveals the deflection of the flow by the geometry along the slope and to the sides. Additionally, the quantitative results show the mass distribution over time on droplet behavior (such as moving droplet mass, wall film mass and evaporation mass) for the whole domain, but forward and backward directions separately. A strong dependency on the impinging position, but a smaller effect of the slope angle, on spray propagation is found. Consequently, these impinging positions have a strong influence on spray behavior in the forward and backward directions regarding moving droplet mass and the wall film mass. In general, this study reveals the severe consequences of step geometry on impinging spray behavior.

Experimental Investigation on the Spray Behaviour of Bluff Body Air-Assisted Atomizer Designs

This study investigates the gas dynamic effects and atomization behavior of a novel sonic bluff body-assisted two-fluid atomizer with three different geometric configurations based on airflow orifice diameters (d) of 2.0 mm, 3.0 mm, and 4.0 mm. Along with a 280 µm annular liquid sheet, atomizers that employed a central bluff body (cone) with 6.0 mm cone distance (Lc) are compared based on the range of different air and liquid (water) flow rates. The spray-bluff body-impacted secondary atomization was characterized through volume-normalized droplet size distribution (DSD) and cumulative droplet distribution, excentricity plots, Sauter mean diameter (SMD), and relative span factor (Δ). Droplet number density decreases with the increase in radial location, with lesser droplet density for the 3.0 mm atomizer. DSD and cumulative droplet distribution become less uniform with the increase in the radial locations with wider distribution for larger diameter atomizers (4.0 mm). Droplet excentricity follows an inverse relationship with the droplet diameter such that high diameter droplets have low excentricity (%) and vice versa. SMD and relative span factor (RSF) showed opposite trends when plotted (line plots) against the air-to-liquid ratio (ALR) with larger fluctuation in the SMD than the RSF (Δ) value. The spray pattern spread increases gradually with increasing liquid loading and with decreases in the ALR value for all atomizers.

A comparison between fossil and synthetic kerosene flames from the perspective of soot emissions in a swirl spray RQL burner

Swirl-stabilized turbulent spray flames operating at atmospheric pressure, with both a conventional Jet-A kerosene (‘A2’) and a synthetic fuel blend (‘C5’) and radially-injected dilution air were investigated from the perspective of soot emissions in a model Rich-Quench-Lean (RQL) combustor. The primary and downstream dilution air flow split was varied while keeping the global equivalence ratio constant (ϕg=0.4). 2.5 kHz PIV, 5 kHz OH-PLIF, and simultaneous 10 Hz Mie scattering and LII were used. Results revealed a correlation between OH and soot distributions. With no dilution air, soot volume fractions (fv) peaked in a v-shaped cone between the OH-containing regions along the spray cone and those anchored to the bluff body. With dilution air at 20% of total air flow, fv shifted to the central axis as OH distributions widened. At 40% dilution, soot initiation began farther downstream along the spray cone, OH regions merged into one, and fv peaked farther downstream at the edge of the Central Recirculation Zone (CRZ). With no air dilution, peak time-averaged fv was 20% lower in the C5 flame compared to A2, despite C5 having a higher aromatics content. However, at 20% dilution fv in C5 increased by 75% compared to the no dilution case. fv in the C5 flame dropped by 12.5% in the high dilution case compared to 40% reductions in A2. Mie scattering showed that the C5 spray was shorter and more resistant to change from dilution air compared to A2. The different spray behaviours were due to C5’s flat boiling range, lower viscosity and density, leading to higher evaporation rates. Detailed chemistry laminar flamelet simulations of A2 and C5 showed that peak soot precursor species mass fraction values and temperatures decreased as the scalar dissipation increased and a significantly stronger presence of toluene in the C5 flame compared to A2. Toluene’s soot yielding behaviour may cause C5’s increased fv with moderate dilution compared to A2. C5 demonstrates the importance of the fuel’s chemical and physical properties when developing future sustainable aviation fuels for practical applications to maximize their soot mitigation potential.

Experimental diesel spray characterization of the medium-duty injector with single- and multi-hole nozzle configurations under non-reacting, non-vaporizing conditions

Characteristics of diesel sprays injected through Cummins medium-duty ISB injectors were studied experimentally in an optically accessible constant-volume combustion vessel. The experiments were performed with ultra-low-sulfur diesel (ULSD) under non-reacting and non-vaporizing conditions, including different ambient gas densities (23–65 kg/m3), injection pressures (500–1,500 bar), and injection duration times (0.5–1.5 ms). The ambient temperature of the vessel was maintained at a room temperature of 313 K for all the tests. A systematic comparison was made between single-hole (SH) and multi-hole (MH) injector configurations. A plume-to-plume variation in spray penetration length was observed for various operating conditions. A substantial deviation was observed for a specific hole against the averaged plume, indicating that arbitrary selection of the plume index may result in inaccurate spray characterization of the MH injector. The penetration length of the MH injector was shorter than that of the SH injector under the same operating conditions, indicating that a spray model calibrated on SH injector data may not accurately predict the transient spray behavior of the MH injector in practical engine simulations. A square-root correlation of the spray penetration length was applied for both the SH and MH injectors. The spray penetration length and dispersion angles of the ISB SH injector were also compared with those of the heavy-duty Cummins ISX SH injector. While the ISX SH injector showed a faster penetration than the ISB SH injector, the dispersion angle was similar. The differences in spray penetration between ISB and ISX injectors followed the expected trend based on their nozzle hole diameters.

In-lab simulation of CAD/CAM grinding and intaglio surface treatments of 4YSZ monolithic restorations: Effect on its load-bearing capacity under fatigue

ObjectivesTo evaluate the effect of in-lab simulation of CAD/CAM grinding and intaglio surface treatments on the surface characteristics (topography and roughness) and fatigue behavior of adhesively luted 4YSZ simplified restorations. MethodsCeramic discs (Ø = 10 mm, thickness = 1 mm) were randomly allocated into 6 groups considering: “In-lab simulation of CAD/CAM grinding” (ground or polished) and “intaglio surface treatments”: Ctrl (without surface treatment), AlOx (aluminum oxide air abrasion) or GLZ (glaze spray application). The surface roughness of all samples was measured, the treated discs received a ceramic primer, were luted with resin cement onto a dentin analogue material (woven glass-reinforced epoxy resin) and tested under a cyclic fatigue test (step-stress approach, n = 15; 1.4 Hz, 10,000 cycles/step, step-size of 100N starting at 200N until failure). A complementary analysis was performed to corroborate the findings in the fatigue test that the glaze fill defects increase the mechanical properties of the ceramic. To do so, bars (n= 10; 1.0 × 1.0 × 12 mm; considering the groups: N-ID: non-indented; ID: indented; ID-GLZ: indented plus glaze spray application) were indented in a vickers hardness tester to produce a crack pattern, treated with glaze or not, and then submitted to flexural strength tests (FS). Fractographic and topographic analysis were performed. ResultsIn-lab simulation of CAD/CAM grinding decreased the fatigue failure load of the 4YSZ ceramic when comparing polished and ground groups, regardless of surface treatment. GLZ induced better fatigue performance compared to the air abrasion, regardless of the grinding condition (ground or polished surface). The results of the flexural strength test corroborated the findings in the fatigue test, as the ID-GLZ group presented superior FS than the ID group, however both had inferior FS than N-ID. There is an inverse association between roughness and fatigue failure load, as the higher the surface roughness, the lower the fatigue failure load. Failures in the fatigue and flexural strength tests started from the face subjected to tensile stresses. ConclusionIn-lab simulation of CAD/CAM grinding had a detrimental effect on the fatigue behavior of 4YSZ and glaze spray induced better 4YSZ performance compared to the air abrasion. The intaglio surface treatments differently influenced the 4YSZ fatigue performance, however, only glaze spray can reverse the damage caused by the grinding.

The effects of nozzle taper angle on in-nozzle flow and nozzle tip-wetting under flash boiling conditions

As an important structural design, the taper angle of an injector has been proved to have a significant influence on spray behavior under both subcooled and flash boiling conditions. However, present studies on taper angle mostly focus on the morphology of the far-field spray, the detailed in-nozzle process as well as the influencing mechanism have not been discussed. To illustrate how the taper angles influence the spray characteristics, backlit imaging method has been adopted on two-dimensional optical nozzles with different taper angle designs. Analyses have been made from in-nozzle bubble development to the unique tip-wetting phenomenon at the counterbore of the injector has been discussed in detail. A novel bubble index is proposed in this paper to describe the in-nozzle flow development. It is found that the design of the taper angle would have a significant impact on the in-nozzle pressure distribution, which would then result in different bubbling characteristics even under the same superheat index, and the contact mechanism between phase boundary and counterbore surface would change with different taper angle designs and tend to result in reverse tip-wetting tendencies under flash boiling conditions compared with subcooled conditions.

Residual stress evolution of 8YSZ:Eu coating during thermal cycling studied by Eu3+ photoluminescence piezo-spectroscopy

Thermal barrier coatings (TBCs) are widely used to protect high temperature structure parts against oxidation and corrosion. The failure mechanism study of TBCs is very important and the stress evolution is core content of failure mechanism research. In this work, a 8YSZ:Eu coating was produced via atmospheric plasma spraying (APS) method. Thermal cycling tests was carried out at 1300 ℃. The residual stress evolution of the coating was detected by a Eu 3+ photoluminescence piezo-spectroscopy based on the relationship between stress and the peak position of 5 D 0 → 7 F 2 transition of Eu 3+ ions. The failure mechanism of the 8YSZ:Eu coating was also studied. The as-sprayed 8YSZ:Eu coating contains metastable t ´ -ZrO 2 and amorphous structure. The stress distribution is inhomogeneous with both compressive stress and tensile stress. After 1000 thermal cycles, the initial compressive stress changed to tensile stress due to the thermal expansion coefficients (TEC) mismatch and irreversible plastic deformation during thermal cycling. With thermal cycling going on, the compressive stress appeared again and the averaged tensile stress decreased due to the volume expansion caused by phase transformation of the t ´ -ZrO 2 to m-ZrO 2 and the formation of cracks. Formation of the thermally grown oxide (TGO), phase transformation, thermal expansion mismatch are factors for the coating failure. • A Eu 3+ photoluminescence piezo-spectroscopy was used to measure the residual stress. • The residual stress distribution and evolution of the 8YSZ:Eu layer during thermal cycling was studied. • A 8YSZ:Eu coating was prepared by atmospheric plasma spraying and thermal cycling behavior was studied.

Experimental Investigation on Auto-Ignition Characteristics of Kerosene Spray Flames

To facilitate the better use of RP-3 kerosene in compression ignition engines, the auto-ignition behaviors of RP-3 kerosene spray were experimentally investigated in an optical rapid compression machine. Results show that most of the tests have good ignitability and combustion performance. For all the successful ignited cases, the flame kernel was found to be formed before the steep rise of pressure, which explained that image-based ignition delay time is always shorter than the pressure-based ignition delay time. The effects of ambient environment, injection pressure, and injection delay time on the pressure history, ignition intensity, combustion duration, heat release rate, and other parameters were investigated individually. The ambient environment has a strong influence on ignition delay time by accelerating the chemical reactions, whereas the high injection pressure helps the better vaporization of fuel spray. The effect of injection delay time is non-monotonic as the trade-off relation between heat loss and blending of fuel and oxygen. The heat release rate histories under different conditions were compared and analyzed, and the two-stage heat release phenomenon was observed in the negative temperature coefficient region. The ignition intensity region was determined based on the measured ignition delay times of RP-3 kerosene spray, and multiple linear regression correlation was used to study the ignition delay time sensitivity to multi-factors.

Experimental investigation on carbon deposition characteristics of aeroengine swirl nozzle and its effect on spray behaviors

The rapid development of aeroengines has resulted in higher thermal stress on the fuel supply system, which spans from the fuel tank to the combustion chamber. In particular, the thermal environment around the fuel nozzle is severe, which increases the possibility of carbon deposits formation. In this study, a series of fouling experimental tests is conducted on swirl nozzles which were commonly used in small-sized aeroengines to further understand the effect of deposits. Three stages of thermal loading are applied to the nozzle to simulate its actual operating condition. Nozzles with different foul levels are obtained at 1, 3, 5, and 10 h of uninterrupted operations, respectively. The spray characteristics of swirl nozzles with different fouling times and clean nozzles are compared. Furthermore, the components are analyzed via scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) to determine the morphology and composition of the deposits. As the fouling time increases, the maximum flow rate loss of the nozzle reaches 14.98%. Because the fouled nozzle cannot form a stable air core easily, the instability of spray angle and liquid film increase significantly. Amorphous deposits containing carbon and oxygen are discovered on the wetted internal wall of the nozzle. The deposits change the flow channel structure of the swirler, which is the most important factor affecting the spray performance. Based on the experimental results, methods for delaying the carbon deposition of swirl nozzles are presented.

Impact of Spray Cone Angle on the Performances of Methane/Diesel RCCI Engine Combustion under Low Load Operating Conditions.

The behaviors of spray, in Reactivity Controlled Combustion Ignition (RCCI) dual fuel engine and subsequent emissions formation, are numerically addressed. Five spray cone angles ranging between 5° and 25° with an advanced injection timing of 22° Before Top Dead Center (BTDC) are considered. The objective of this paper is twofold: (a) to enhance engine behaviors in terms of performances and consequent emissions by adjusting spray cone angle and (b) to outcome the exergy efficiency for each case. The simulations are conducted using the Ansys-forte tool. The turbulence model is the Renormalization Group (RNG) K-epsilon, which is selected for its effectiveness in strongly sheared flows. The spray breakup is governed by the hybrid model Kelvin–Helmholtz and Rayleigh–Taylor spray models. A surrogate of n-heptane, which contains 425 species and 3128 reactions, is used for diesel combustion modeling. The obtained results for methane/diesel engine combustion, under low load operating conditions, include the distribution of heat transfer flux, pressure, temperature, Heat Release Rate (HRR), and Sauter Mean Diameter (SMD). An exergy balance analysis is conducted to quantify the engine performances. Output emissions at the outlet of the combustion chamber are also monitored in this work. Investigations show a pressure decrease for a cone angle θ = 5° of roughly 8%, compared to experimental measurement (θ = 10°). A broader cone angle produces a higher mass of NOx. The optimum spray cone angle, in terms of exergy efficiency, performance, and consequent emissions is found to lie at 15° ≤ θ ≤ 20°.

Effect of pulsed electromagnetic field treatment on dislocation evolution and subsequent artificial aging behavior of 2195 Al-Li alloy

In this paper, the pulsed electromagnetic field treatment (PEFT) is designed between the pre-stretching and artificial aging of the thermomechanical treatment. Using electron microscopy and hardness test, the effect of the PEFT on dislocation evolution and subsequent artificial aging behavior of spray deposited 2195 Al-Li alloy is studied. The results show that although the PEFT reduces the Vickers microhardness of the specimen, it improves the hardening kinetics and precipitation strengthening of the specimen during the subsequent artificial aging process. Besides, it is found that the PEFT reduces the dislocation density of the pre-stretching specimen and improves the dislocation uniformity. The PEFT makes the T 1 precipitate obtained by the subsequent artificial aging process more finely dispersed, a decrease of the average thickness by 57.6%. From simulation combined with theoretical analysis, it is found that the static recovery induced by temperature rise is an important reason for the decrease of dislocation density on the specimen during the PEFT. The magnetically induced stress is an important driving force for a more uniform dislocation distribution. The mechanism of the microstructure evolution of the material is systematically discussed and summarized. • The effect of pulsed electromagnetic field treatment (PEFT) on microstructure evolution of 2195 Al-Li alloy was studied. • PEFT reduced the dislocation density of the pre-stretching specimen and improves the dislocation uniformity. • PEFT made the T 1 precipitate obtained by the subsequent artificial aging process more finely dispersed. • The static recovery induced by temperature rise and magnetically induced stress was discussed.

Analysis of spray/wall impingement using an ECN single-hole injector and a controlled-temperature wall under realistic engine conditions

Spray–wall interactions (SWI) directly affect fuel–air mixture and emissions formation. Therefore, they are considered among the most critical physical processes in engine research nowadays. However, the physics of the wall film formation, propagation, and breakup is not fully understood yet. This work aims to use a thermoregulated steel wall to study the spray–wall interaction phenomenon and its influence on the macroscopic spray behavior. A single-hole injector known as “Spray D” in the Engine Combustion Network was used. n-Dodecane was employed as fuel and the wall has been positioned in four different configurations, varying angle and distance respect to the injector tip. For this work, not only diesel combustion is reproduced in the test rig due to ambient gas engine-like thermodynamic conditions, but wall temperature has been controlled to emulate characteristic values that could be found in the piston of an internal combustion engine. This implies that the spray–wall heat transfer is simulated and its effects on ignition and spray development can be analyzed. Heat flux was measured by employing high-speed thermocouples fitted in the wall and by the use of an one-dimensional transient wall heat model. Three high speed cameras were simultaneously used to observe the SWI, one for the Schlieren optical technique which allows to study the vapor phase of the spray and to determine the ignition delay, another one to observe the natural luminosity of the flame, and finally, an intensified camera was used to determine the lift-off length by observing the chemiluminescence of the OH*. An interesting finding obtained in this work was a boundary layer formation due to the thermal diffusion that contributes to cool down the spray and to delay the high-temperature chemical reactions. Results show a substantial increment of the heat flux and the wall temperature variation with both ambient temperature and density by increasing the flame temperature and gas entrainment. The exposure to the cold wall affects the ignition delay variation with the injection pressure and the wall distance. It was found that the wall temperature (in the range of tested conditions) did not affect the lift-off length location. • The exposure to the cold wall delayed the ignition. • Flame thickness around the wall undergoes a narrowing at lower wall temperatures. • The injection pressure increments the convective coefficient. • A boundary layer due to thermal diffusion was formed on the wall.

Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions

Diesel engine combustion becomes very rough and can lead even lead to deflagration under high altitude conditions, which is harmful to component durability. In this study, the effects of altitude on the main combustion characteristics—in-cylinder fluid flow, spray behavior, and pressure and temperature distribution—were analyzed with CFD. A numerical model was built on the CONVERGE platform and validated with the optical spray behavior and pressure trace measured by the test bench. The simulation results indicated that the decreases in compression pressure and temperature at 4.5 km led to an over 4 °CA longer ignition delay than those of 1 and 3 km. The combustion efficiency decreased from 90% to 47% when the combustion changed from normal combustion to knocking combustion due to severe spray impingement. The processes of end-gas ignition, sequential combustion, and pressure oscillation in knocking combustion were revealed by the numerical modeling results. These results indicate that super-knocking combustion exists in both spark-ignition (SI) engines and compression-ignition (CI) engines.

Effect of adding a liquid combustible component and wood biomass to slurry fuel on spraying characteristics

The paper presents experimental research findings for the spraying behavior of slurry fuels that are promising in terms of environmental, energy and economic indicators. The effect of adding a liquid combustible component and wood biomass to coal-water fuels on their spraying behavior was investigated. The experiments were conducted using optical measurement techniques like Particle Image Velocimetry and Shadow Photography. The integral characteristics of the fuel jet were recorded: droplet velocity and size, the jet angle and the jet angle deviation from the symmetry axis of the nozzle. Following the experiments, the ranges of jet characteristics and the way they are affected by spraying conditions were established for each fuel composition. We defined the ranges of the mass flow rate of air that improve and, on the contrary, deteriorate the spraying behavior when a liquid combustible component or wood biomass is added to the coal-water composition.

ECN Spray G: Coupled Eulerian internal nozzle flow and Lagrangian spray simulation in flash boiling conditions

Flash-boiling of fuel sprays occurs when a super-heated fuel is discharged into an environment whose pressure is lower than the saturation pressure of the fuel and can dramatically alter spray formation due to complex two-phase flow effects and rapid droplet vaporization. In gasoline direct injection (GDI) engines, typically, it occurs during the injection process when high fuel temperatures make its saturation pressures higher than the in-cylinder one. Flash boiling significantly affects the spray structure and fuel-air mixture formation, with, potentially, if spray collapse is avoided, positive consequences for the engine performance and pollutant emissions. Hence, this paper developed a modelling approach based on the coupling of Eulerian multi-phase and Eulerian-Lagrangian simulations to reproduce flash boiling sprays physics. It allows a comprehensive description of the flash-boiling phenomena that begins within the injector’s ducts and continues outside, where a particular mechanism for primary breakup occurs. Experimental data of the Engine Combustion Network (ECN) Spray G injector, covering various operating conditions, were exploited to assess the reliability of the numerical technique adopted. The validation was performed taking into account various parameters such as axial liquid and vapour penetrations, droplet size and images regarding the near-nozzle zone. The numerical model achieves a pretty good level of agreement with the experimental data and, in particular, it is sensitive to the spray behaviour in the different operating conditions.

Spray Behavior, Combustion, and Emission Characteristics of Jet Propellant-5 and Biodiesel Fuels with Multiple Split Injection Strategies

This study focuses on an analysis of the spray behavior, combustion, and emission characteristics of jet propellant-5 (JP-5) and biodiesel fuels with single-injection timing and multiple split injection strategies in a common rail direct injection (CRDI) single-cylinder diesel engine system. The analysis includes visualization of the spray and combustion. Multiple split injection strategies (e.g., double, triple, quadruple, and quintuple) were considered by equally distributing the fuel injection amount within the single-injection. Injection of biodiesel has a delayed start (0.2 ms) as well as shorter spray tip penetration compared with JP-5. As the fuel injection timing was approached to the top dead center (TDC), the engine performance and combustion efficiency improved. Retarding the injection timing contributed to an increase in carbon dioxide (CO2) (JP-5: max. 2.6% up, BD100: max. 1.5% up) and a decrease in carbon monoxide (CO) (JP-5: max. 93% down, BD100: max. 91% down) and nitrogen oxides (NOx) (JP-5: max. 83% down, BD100: max. 82% down). In comparison with JP-5, biodiesel showed disadvantages from the point of its combustion and emission characteristics for all injection timings. The quadruple-injection strategy, in which fuel injection was performed four times, showed excellent combustion, engine performance, and combustion efficiency. The CO2 emissions were highest with the quadruple-injection strategy (JP-5: 6.6%, BD100: 5.8%). The CO emissions of biodiesel decreased as the pulses of split injection extended, and a significant reduction of 83.8% was observed. NOx increased as the number of split injections increased (JP-5: max. 37% up, BD100: max. 52% up). JP-5 was a longer ignition delay than that of biodiesel from combustion flame visualization results. The final combustion in the multiple-injection strategy showed a typical diffusion combustion pattern.

Spray analysis of Palm-Based biodiesel to correlate performance and combustion analysis of a compression ignition engine

Palm oil diesel (POD) is derived from palm oil using an esterification process. POD has similar physicochemical properties to fossil diesel, and this allows POD to be the primary substitute to diesel. However, existing research has found that the combustion of POD in CI engines produce lower performance standards than pure diesel. This is due to POD having a higher viscosity, density and presence of heavier molecules resulting in poor evaporation and mixing with the air leading to higher brake specific fuel consumption (BSFC) and reduced power. This research aims to observe the fuel spray behaviors inside the combustion chamber and corelate these with the lower performance of POD than diesel. POD is tested at 100% (B100) and, blended with diesel at a ratio of 50/50 (B50) by volume to reduce the viscosity. The study of spray properties in real engines is expensive and difficult, with most studies being performed in constant volume transparent chambers using Mie-scattering and Schlieren imaging techniques. Therefore, the engine simulation is conducted using ANSYS Forte software to observe the in-cylinder spray behaviors. A 26-kW diesel engine used in a generator is modelled using SolidWorks with respective performance parameters noted from simulation data. The CHEMKIN-PRO software is used to create POD by solving thousands of reaction combinations. Spray analysis of fuels shows longer penetration lengths with POD, higher Sauter Mean Diameter (SMD) and heavier mass of fuel molecules than diesel. These along with a lower calorific value of POD resulted in lower power and a higher brake specific fuel consumption than diesel. Furthermore, B50 performs better than B100.

Effects of surface modification on fuel-lubricated tribological behavior of WC-Co thermal spray coating

The objective of this study is to evaluate the effects of ultrasonic nanocrystal surface modification (UNSM) on the tribological behavior of WC-Co thermal spray coatings for fuel-lubricated components. UNSM reduced the average surface roughness from 4.22 µm down to 2.26 µm and increased the hardness from 861 HV1 up to 1091 HV1. UNSM reduced the intensity and broadened the full width at half maximum of X-ray diffraction peaks, which indicated a combination of refinement in grain size and introduction of compressive residual stress. The coefficient of friction under fuel lubrication was reduced significantly by UNSM from 0.083 to 0.011, while the specific wear rate decreased from 6.21 ± 1.41 × 10−13 mm3/N × m to 2.07 ± 0.36 × 10−13 mm3/N × m after UNSM.

Comparison of the hot corrosion behavior of the LZ, CSZ and LZ/CSZ composite thermal barrier coating

In the present study, the hot corrosion behavior of Air Plasma Spray (APS)-deposited Ceria Stabilized Zirconia-Lanthanum Zirconate (CSZ-LZ) composite thermal barrier coatings (TBCs) was investigated and compared with CSZ and LZ coatings. The hot corrosion tests were conducted at 950 °C in a cyclic mode in the presence of V2O5 + Na2SO4 molten salt mixture. The microstructural aspects were evaluated by energy dispersive spectroscopy (EDS) equipped scanning electron microscopy (SEM) and x-ray diffraction (XRD) methods. The results showed that CSZ, 75CSZ-25LZ, 50CSZ-50LZ, 25CSZ-75LZ and LZ coating systems lasted for 28–30 h, 24–26 h, 22–24 h, 20–22 h, and 18–20 h, respectively. The results revealed an improvement in the hot corrosion resistance of composite coating compared with LZ coating which can be attributed to better coefficient of thermal expansion (CTE) compatibility of composite coatings. The formation of hot corrosion products such as CeVO4, LaVO4, and also tetragonal to monoclinic transformation are the main reasons for the failure of these coatings.