Constant Volume Spray Chamber Research Articles

Macroscopic jet characteristics of hydrogen and natural gas in direct injection spark ignition engine-like conditions

Hydrogen has enormous potential for sustainable future mobility. However, current challenges include high production costs and storage issues, necessitating further engineering advancements. Compressed Natural Gas is also a viable alternative, as it is easily produced and stored but suffers from slow flame speed-related issues. Improving its combustion characteristics by enrichment using a small fraction of hydrogen holds significant promise. Inducting hydrogen directly into the combustion chamber improves the engine's volumetric efficiency, eliminating the backfire issues. However, it is crucial to understand the test fuel's jet and mixing characteristics before engine investigations. This study aims to analyse the macroscopic jet characteristics of hydrogen, compressed natural gas and hydrogen-enriched compressed natural gas in realistic engine-like conditions in a constant volume spray chamber at various fuel injection pressures and varying ambient pressures and temperatures. Fuel injection pressures for hydrogen and CNG were varied at 16, 32, and 48 bar, and ambient pressures in the constant volume spray chamber were set at 4- and 8-bar and ambient temperatures at 25 and 100 °C. The results showed hydrogen exhibited ∼2% shorter jet penetration length than compressed natural gas. Depending on the test conditions, hydrogen showed a ∼1–3% higher jet area than CNG due to its higher diffusivity and faster mixing. This higher jet area improved fuel-air mixing of hydrogen with air compared to CNG. The effect of hydrogen enrichment with CNG on their jet characteristics was also analysed for 8 bar FIP. 10% (v/v), 20%, and 40% hydrogen-enriched compressed natural gas did not significantly alter the macroscopic jet characteristics from baseline compressed natural gas.

Shape/penetration analysis and comparisons of isolated spray plumes in a multi-hole Diesel spray

Fuel injection systems significantly impact the combustion process and play a key role in reducing harmful exhaust emissions in internal combustion engines. For dual-fuel (DF) engines operating in gas mode, ignition of the main fuel is typically controlled by directly injected liquid pilot fuel. Liquid pilot fuel’s initial penetration and total mass considerably impact exhaust emissions and combustion stability. We investigated the spray morphology of a multi-hole diesel fuel injector within a constant-volume spray chamber using high-speed shadowgraphy and Mie-scattering measurements. Two methodologies were employed. The first one utilized a nozzle equipped with a thimble structure to isolate a single plume. The second methodology known as plume-blocking, involved sealing the orifices of the multi-hole nozzle to generate a single-spray plume. Our findings revealed that the plume-blocking approach demonstrated greater penetration than the thimble-equipped nozzle. The rapid penetration of this method may restrict its applicability to single-spray studies. Sprays generated from this partially sealed nozzle exhibited noticeable disparities compared to an unblocked nozzle, whereas a nozzle equipped with a thimble produced similar outcomes to the standard nozzle. The orifices when sealed, modify the flow distribution within the sac volume, which consequently affects the spray characteristics. In summary, this research provides insights into the impacts of various plume isolation methods on spray morphology, thereby enhancing the understanding of spray behaviour in transient conditions by comparing plume variations and disturbances under various fuel pressure and ambient conditions.

Effects of fuel injection pressure and quantity on low octane gasoline sprays in a simulated high-pressure ambient environment of a gasoline compression ignition engine

Gasoline Compression Ignition technology using low-octane gasoline-like fuel can lead to very low NOx and Soot emissions and enhanced thermal efficiency than conventional diesel engines. The difference in test fuel properties is a significant reason for the difference in the fuel–air mixture formation in Gasoline Compression Ignition engines offering these advantages. In this study, microscopic and macroscopic spray characterisation of baseline diesel, 50 % v/v diesel blended with 50 % v/v gasoline (G50), and 20 % v/v diesel blended with 80 % v/v gasoline (G80) are conducted in a high-pressure ambient environment relevant to Gasoline Compression Ignition engines. The study was performed in a constant volume spray chamber in non-reacting conditions using Phase Doppler Interferometry and Diffused Backlit Illumination techniques. The test fuels were injected into a 30 bar ambient pressure environment at 400, 500, and 700-bar fuel injection pressures. The liquid spray penetration length of gasoline-diesel blends was slightly shorter than baseline diesel, but their spray cone angles and entrained air mass were significantly higher. The average axial droplet velocity was higher, and the Sauter Mean Diameter was lower for gasoline-diesel blends than baseline diesel 40 mm away from the injector nozzle exit, indicating superior mixture formation for the gasoline-diesel blends. The effect of droplet collision and injected fuel quantity on droplet size distribution was assessed in all test fuels. Droplet collisions increased the Sauter mean diameter of the spray at farther distances. Smaller fuel injection quantities decreased the Sauter mean diameter of the spray, increasing the probability of unburnt hydrocarbon emission producing ultra-lean regions in the engine combustion chamber.

Droplet Combustion Behavior and Spray Characteristics of Diesel–Ethanol–Jatropha Oil Ternary Fuel Blends Under High-Pressure Evaporating Conditions

Abstract This study investigates the behavior of a single droplet exposed to high-temperature ambient air and macroscopic spray characteristics of various ternary blends of diesel–ethanol–jatropha oil. The experiments on single droplet are performed at ambient pressure and high temperature. The spray experiments are performed under high-pressure and high-temperature conditions, similar to those of a diesel engine in-cylinder air at the time of fuel injection for three blends. The D50E35J15 has exhibited micro-explosion behavior; D50E30J20, which has shown puffing, and D60E20J20, which has demonstrated both micro-explosion and puffing during single droplet experiments, are selected for spray experiments. A constant volume spray chamber with optical access equipped with an electric heater was used to study evaporating spray characteristics of the blends at 5 MPa and 900 K. The spray experiments have shown that the ternary fuel blends have higher liquid penetration as compared to that of diesel due to the higher boiling point of jatropha oil. The variation in the spray cone angle between the different blends was found to be insignificant and within the measurement’s uncertainty limits. Thus, the blends which have exhibited micro-explosion and puffing in droplet experiments have not affected the macroscopic spray characteristics at higher ambient pressures.

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

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

Macroscopic and Microscopic Spray Characteristics of Dimethyl Ether in a Constant Volume Spray Chamber Using a Mechanical Fuel Injection System for Automotive Applications

Abstract Spray investigations are critical for understanding internal combustion engine combustion. Optimised spray atomisation helps improve engine output/performance and reduce tailpipe emissions. The spray from the injector nozzle depends on nozzle hole diameter, fuel injection pressure, ambient density, pressure and temperature in the spray chamber, and test fuel properties. This study evaluated macroscopic and microscopic spray characteristics of dimethyl ether (DME) and baseline diesel under atmospheric conditions (1.013 bar pressure at 298 K temperature). It correlated the spray parameters with distinctive physicochemical properties of diesel and DME using dimensionless numbers, namely Reynolds number, Weber number, and Ohnesorge number. The fuel injection system consisted of a high-pressure mechanical injection pump and mechanical fuel injectors having an original equipment manufacturer fixed nozzle opening pressure in the constant volume spray chamber. The microscopic spray investigations were performed using a phase Doppler interferometer along the spray direction at three axial distances (50, 70, and 90 mm) from the nozzle. The three orthogonal spray droplet velocities of diesel and DME were compared. The droplet number-size distributions for baseline diesel and DME were compared. Macroscopic spray characteristics were evaluated using high-speed imaging. Reynolds number was higher for DME, leading to more turbulence in the spray and accelerating the spray breakup phenomenon. Weber number of DME was also much higher than baseline diesel due to its lower surface tension. The higher Weber and lower Ohnesorge numbers justified the finer droplets of DME sprays. DME showed superior spray atomization characteristics than baseline diesel, leading to superior fuel–air mixing and efficient and sootless combustion.

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.

Effects of Accelerated Oxidation on Fuel Spray and Engine Characteristics of Karanja Biodiesel

Abstract The unsaturated content of biodiesel makes it prone to oxidation resulting in variations in the fuel properties, hindering its widespread application. Variations in biodiesel properties impact injection, spray, evaporation, mixing and combustion processes. The present study investigates the effect of accelerated oxidized Karanja biodiesel on injector flow, macroscopic spray, and engine characteristics. The accelerated oxidation of Karanja biodiesel is carried out by heating and bubbling the air through the fuel. The variations in fuel properties that profoundly influence spray and engine characteristics are analyzed before and after accelerated oxidation. Even though biodiesel viscosity is increased beyond the ASTM specification limit due to accelerated oxidation, the variations in the density, surface tension, and calorific value are marginal. The injector flow and macroscopic spray characteristics are investigated for fresh and oxidized biodiesel using a constant volume spray chamber at different chamber and injection pressures. The results indicate a similar fuel flowrate and injection velocity for the fresh and oxidized biodiesels at identical test conditions. Under identical test conditions, the macroscopic spray characteristics between the test fuels are negligible. Engine experiments with fresh and oxidized biodiesel are carried out in an automotive truck diesel engine at rated torque speed and variable load conditions. A shorter ignition delay (∼20% lower), less intense premixed combustion, and lower nitrogen oxide (NOx) emissions (∼27% lower) are observed with oxidized biodiesel. The study concludes that despite significant variations in the kinematic viscosity of fresh and oxidized biodiesels (∼28% higher), the variations in macroscopic spray and engine performance characteristics are insignificant.

Spray Analysis of Biodiesels Derived from Various Biomass Resources in a Constant Volume Spray Chamber.

This research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5–18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2–35.1% larger SMD values and approximately 7% lower air entrainment.

Macroscopic spray characteristics of a gasohol fueled GDI injector and impact on engine combustion and particulate morphology

A comprehensive understanding of renewable fuels' spray behavior leads to superior combustion and emission characteristics from internal combustion (IC) engines. This study is aimed at investigating the influence of gasoline and gasohol (E15, M15, and Bu15; 85% v/v gasoline blended with 15% v/v ethanol, methanol, and butanol) on macroscopic spray characteristics, followed by IC engine combustion characterization. Macroscopic spray investigations were performed at four different fuel injection pressures (FIPs) in a constant volume spray chamber (CVSC) for oxygenated renewable fuels vis-à-vis conventional fuels. This study was followed by engine investigations, with a focus on comparative combustion characterization for the test fuels at different load points. The engine was then optimized to find the maximum brake torque (MBT) timing for all test fuels. Towards the end, field emission-scanning electron microscopy (FE-SEM) images of soot particles were also presented along with Energy-dispersive X-ray spectroscopy (EDS) analysis to find trace metals in soot particles. Numerous studies in the open literature are available wherein researchers have shown that the presence of oxygen in fuel helps meet stringent emission legislations; however, most studies didn’t investigate the effect of fuel oxygen on spray characteristics. One of the research questions debated in this manuscript is “how important is macroscopic spray characteristics, when it comes to using renewable fuels in gasoline direct injection (GDI) engines?” The database from these experimental investigations of renewable fuels may be vital in simulations of spray and combustion in the near future for developing efficient and cleaner next-generation IC engines, which is in contrast with previous researches focused on engine emissions and fuel efficiency improvement alone.

Influence of nozzle geometry on spray and combustion characteristics related to large two-stroke engine fuel injection systems

As emission regulations for large two-stroke marine Diesel engines increase as well, the manufacturers face similar problems as small-sized engine builders. The fuel injection, spray formation and subsequent combustion process remain among the main drivers for emissions of direct-injection, compression-ignition internal combustion engines. Since the fuel injection nozzle design of large two-stroke marine Diesel engines differs significantly, not only in size but especially regarding their non-symmetricity and eccentrical orifice arrangement, compared with four-stroke engines, the bulk of research available related to this topic is very limited.To further deepen the understanding of how in-nozzle cavitation flow during the fuel injection process affects the combustion behaviour in large two-stroke marine Diesel engines, transparent nozzle geometries have been used to link the cavitation phenomena with spray and combustion characteristics. A total of six single-orifice nozzles based on the original five-orifice nozzle design of large two-stroke marine Diesel fuel injectors, with and without hydro-erosive grinding, have been experimentally investigated under realistic engine conditions using highspeed optical measurement techniques and a unique constant-volume spray chamber that geometrically represents a combustion chamber of a large two-stroke marine Diesel engine at top dead centre.The spray morphology and combustion results reveal significant differences between the non- and hydro-erosive ground nozzle geometries. While the standard and angled nozzle versions remain similar, the eccentrical nozzle with its distinctive in-nozzle swirl cavitation pattern behaves differently, leading to a very reliable start of ignition behaviour and extreme wide spray angle.

Microscopic spray characteristics of ethanol and methanol blended gasoline in a direct injection spark ignition engine

Renewable fuels are continuously being refined/ upgraded for automotive applications to reduce dependence on conventional fossil fuels. However, optimized use of these renewable fuels in existing and new engines/ vehicles requires comprehensive characterization and understanding of spray atomization and fuel-air mixture formation processes. Spray atomization and mixture formation depends on fuel injection pressure (FIP), fuel injection quantity and ambient conditions. This study is aimed at exploring microscopic spray characteristics of ethanol and methanol blended gasoline for automotive applications, particularly in direct injection Spark Ignition (DISI) engines. Phase Doppler interferometer (PDI) technique was used for comparative microscopic spray characterization in a constant volume spray chamber (CVSC) at ambient pressure condition, to evaluated spray droplet size-velocity distributions and joint probability density function (JPDF) of different test fuels. In this study, two gasohol mixtures [15% v/v ethanol and methanol blended with 85% v/v gasoline] and baseline gasoline were experimentally evaluated for comparing spray droplet size-velocity distributions at two different FIPs of 80 and 160 bars, at two different fuel injection quantities of 12 and 28 mg/injection, which are typical representative conditions for a DISI engines. The results from this experimental investigation are valuable for automotive and fuel industries, and spray community, which are continuously upgrading renewable and oxygenated fuels and engine technologies for efficiency improvement and emission reduction.

Investigations of split injection properties on the spray characteristics using a solenoid high-pressure injector

An on-going challenge with Gasoline direct injection (GDI) engines is achieving rapid activation of the exhaust catalyst during cold starts, in order to reduce the Nitrogen Oxide (NOx) emissions. Injecting late in the compression stroke, in the efforts to form a stratified mixture, provides the fuel insufficient time to be entrained with the surrounding charge. This results in locally fuel rich diffusion combustion and the formation of high levels of particulate matter. Employing a split injection strategy can help tackle these issues. The current study examines the effects of a split injection strategy on the spray characteristics. Varying pulse width (PW) combinations, split ratios and dwell times are investigated using a Solenoid actuated high pressure injector. The injected quantity and the droplet characteristics of a target plume are investigated. The experiments were performed in a constant volume spray chamber. The droplet velocities and sizes were measured using Phase Doppler Particle Anemometry (PDA). Short and large PWs, in the range of 0.3–0.8 ms, were investigated. The results revealed that the highest injected quantity of fuel was measured with the shortest dwell time of 2 ms, owing to increased interactions between the injection events, which led to larger Sauter mean diameters (SMDs) measured. The SMDs for the shorter PW of 0.4 ms were generally larger than 0.8 ms PW. The droplets in this case were affected by the closely spaced opening and closing events of the Solenoid valve.

Large-Eddy Simulation Study of Ultra-High Fuel Injection Pressure on Gasoline Sprays

The development of gasoline spray at ultra-high injection pressures was analyzed using Large-Eddy simulation (LES). Two different nozzle hole geometries, divergent and convergent shape, were considered to inject the fuel at injection pressures ranging from 200 to 1500 bar inside a constant volume spray chamber maintained at atmospheric conditions. The discrete droplet phase was treated using a Lagrangian formulation together with the standard spray sub-models. The numerical results were calibrated by reproducing experimentally observed liquid penetration length and efforts were made to understand the influence of ultra-high injection pressures on the spray development. The calibrated model was then used to investigate the impact of ultra-high injection pressures on mean droplet size and droplet size distribution. In addition, the spray-induced large-scale eddies and entrainment rate were evaluated at different ultra-high injection pressures. Overall, simulation results showed a good agreement with available measurement data. At ultra-high injection pressures mean droplet sizes were significantly reduced and comprised very high velocities. Integral length scales of spray-induced turbulence and air entrainment rate into the spray were larger at higher injection pressure compared to lower ones.Graphic abstract

Flash boiling combustion of isomeric butanol and gasoline surrogate blends using constant volume spray chamber and GDI optical engine

Flash boiling spray has been regarded as a promising fuel injection technology. Many investigations have been focused on spray physics and mechanisms of flash boiling spray, but information on flash boiling of alcohols in GDI engines is very limited. In this paper, the spray characteristics, flame propagation, combustion analysis, and PN emissions of butanol isomers under flash boiling spray have been studied. A constant volume chamber with a high-speed camera used to investigate the flash boiling spray of butanol isomers and gasoline surrogate blends. The flash boiling spray was tested at 180 °C and compared to subcooled spray at 25 °C. The tested gasoline surrogates are primary reference fuel (PRF) and toluene primary reference fuel (TPRF). The flash boiling leads to the collapse of the spray six plumes into a single extended spray plume with longer spray penetration compared to subcooled injection. The spray study then extended to study the effects of flash boiling injection on flame development and PN emissions of the GDI optical engine. The results reveal that flash boiling injection leads to lower apparent flame speed and flame area compared to subcooled injection due to the lean-like burn condition, and yellow flame spots are diminished. The peak in-cylinder pressure and apparent heat release rate are reduced with longer ignition delay when the flash boiling injection is applied. The flame lasted longer under flash boiling conditions with improved late combustion phase, which results in higher heat released. The PN emissions reduced with flash boiling spray compared to subcooled conditions.

Schlieren investigation on impacts of duct size on macroscopic spray characteristics of ducted fuel injection

Ducted fuel injection (DFI) is a cutting-edge technology for boosting the air-fuel mixture quality of heavy-duty diesel engines. The present study employs ducts with different lengths and inner diameters to investigate the diesel macroscopic spray characteristics of DFI spray by Schlieren optical technique and compares them with a free spray. The experiment is carried out in a constant-volume spray chamber with a single-hole injector. Injection pressure ranges from 40 to 160 MPa and ambient pressure is set to 6 MPa. Spray morphology, spray tip penetration, spray cone angle and spray area are analysed. It is found that DFI spray with long and small inner diameter duct shows a considerable improvement in spray characteristics compared to those of free spray, especially under higher injection pressure. Besides, the use of long and small inner diameter duct is more comfortable to form a clear mushroom-shaped head spray at the duct outlet. These advantages can be attributed to the enhanced air-fuel mixing.

Impacts of duct inner diameter and standoff distance on macroscopic spray characteristics of ducted fuel injection under non-vaporizing conditions

Ducted fuel injection spray is a new technology for reducing soot formation in heavy-duty diesel engines. In this work, the ducted fuel injection spray characteristics with different duct inner diameters and different standoff distances were investigated and compared with free spray. Duct inner diameter ranged from 1.5 to 4 mm, and standoff distance varied between 0.9 and 4.9 mm. Mie-scattering optical technique was used to characterize spray characteristics under various injection pressures in a constant-volume spray chamber. Ambient gas pressure of up to 6 MPa when spraying. The results showed that ducted fuel injection spray with smaller duct has better spray diffusion compared to those of ducted fuel injection sprays with larger ducts and free spray from the perspectives of spray tip penetration, spray cone angle and spray area. Increasing standoff distance could increase spray velocity. Ducted fuel injection spray with smaller duct formed a mushroom-shaped head and large-scale vortex flow close to the duct outlet. All the advantages of ducted fuel injection spray with smaller duct are interpreted as evidence of improving fuel–gas mixing quality significantly.

Biodiesel Spray Characteristics and Their Effect on Engine Combustion and Particulate Emissions

Abstract Spray analysis is used to characterize the fuel spray evolution and spray shape, which affects in-cylinder combustion and particulate emission characteristics of compression ignition (CI) engines. In this study, spray evolution of biodiesel blends and mineral diesel was captured using a high-speed charge coupled device (CCD) camera at different fuel injection pressures (FIPs) and ambient pressures (APs) in a constant volume spray chamber (CVSC). Results showed that spray parameters were significantly affected by FIP and AP. Higher FIPs resulted in longer fuel spray penetration length (Ls) and reduced spray cone angle (As). However, AP variation showed an exactly opposite trend of Ls and As. Increasing AP resulted in shorter Ls and increased As. Fuel properties also affected the spray characteristics, which slightly improved for lower biodiesel blends (B20: 20% v/v blend of biodiesel with mineral diesel) and then degraded for higher biodiesel blends (B40: 40% v/v blend of biodiesel with mineral diesel) with respect to baseline mineral diesel. The effects of these findings of fuel spray analysis were validated using engine experiments, which were performed in a single-cylinder research engine using identical test fuels and fuel injection parameters. Relatively superior combustion of B20-fueled engine and lower particulate emissions at higher FIPs showed good agreement with spray results.

Spray droplet size distribution and droplet velocity measurements in a firing optical engine

Macroscopic spray characteristics of a fuel injection system in an internal combustion (IC) engine have a direct impact on engine performance, emissions, and combustion characteristics. Nonintrusive in-cylinder measurements provide insights into the spray formation process for greater understanding of fuel-air mixing and combustion processes in an IC engine. In this paper, there are two parts: (a) procedure and methodology to configure the Artium phase Doppler interferometer (PDI) for in situ measurements through a cylindrical window and (b) comparative macroscopic spray characteristics in a firing Gasoline Direct Injection (GDI) optical engine to a constant volume spray chamber (CVSC) for spray droplet size-velocity distributions. Binned average velocity and average Sauter mean diameter of spray droplets in a firing engine were compared with that of a CVSC. Probability density function of droplet diameters in the CVSC under ambient conditions and in the engine combustion chamber provides an insight into the comparative droplet size distributions and droplet dynamics. Discussion on challenges encountered during PDI measurements in the firing engine environment, safety protocols, and tools required is also included. In addition, shadowgraphy images have been used to discuss the details on spray boundaries and spray evolution. The droplet size distribution inside the engine combustion chamber was found to be significantly different from the one observed in the CVSC. An engine simulation model can be developed/validated by using the data reported in this manuscript for attaining superior accuracy in the model. This paper describes the comparisons of the spray droplet size and velocity distributions in a CVSC and in situ for a working GDI engine. Maximum spray droplet velocity components (Vx, Vy) under engine combustion chamber conditions were 29.8 m/s, 14.2 m/s whereas the corresponding velocities in the CVSC under ambient conditions they were 78.41 m/s, 23.92 m/s, respectively, showing a large difference between the traditional measurements in the CVSC simulating engine conditions, and actual firing engine conditions. This study also reports the very first attempt in the open literature to measure spray droplet size and velocity distribution measurements in a firing IC engine.

An optical investigation on spray macroscopic characteristics of ducted fuel injection

Ducted fuel injection (DFI) spray is a new spray method that mimics Bunsen burner and has shown a great potential to reduce soot emissions and improve thermal efficiency for heavy-duty diesel engines. But the mechanism has not been revealed clearly. The present study focuses on how the duct impacts the spray characteristics compared to free spray considering the importance of air-fuel mixing. Experiments were performed in a constant-volume spray chamber with a single-hole injector. Schlieren visualization technique was used to capture vapor-phase of sprays under different injection pressures. It was found that DFI spray is more dispersed compared to free spray. DFI spray could increase spray penetration significantly compared to free spray, especially under higher injection pressures. DFI spray could also increase spray cone angle by about 4° compared to free spray. Since diesel spray was trapped in the duct, when the spray penetrated through the duct, DFI spray area was smaller than that of free spray during initial period, but quickly exceeded that of free spray and became larger and larger. These advantages indicate DFI is able to improve the air-fuel mixing process.