Effect of Non-Isothermal Conditions on Liquid Breakup Mechanisms

2010 ◽  
Author(s):  
Ilai Sher
Keyword(s):  
Physical Properties ◽  
Fuel Injection ◽  
Thermal Exposure ◽  
Ambient Air ◽  
Combustible Mixture ◽  
Liquid Droplets ◽  
Gas Temperature ◽  
Fuel Droplets ◽  
Breakup Mechanism ◽  
Secondary Breakup

Liquid breakup mechanism utilization is prevalent in numerous applications. One of the most common uses of this phenomenon is in fuel injection systems. Liquid fuel is injected into an ambient air, to prepare a combustible mixture. Generally, evenly spread tiny fuel droplets are desirable. This is usually achieved through multiple liquid breaking mechanisms: Primary breakup of liquid jet, Secondary breakup of travelling liquid droplets, and Secondary breakup of wall-impinging liquid droplets. Indeed, many studies are devoted to the modelling of those phenomena. However, the absolute majority of those studies are limitedly focused on the isothermal case, where liquid is assumed to be of ambient gas’ temperature. Conversely, practical conditions, under which rather cold fuel is normally injected into hot ambient air, suggest the real case to be non-isothermal. Moreover, the non-isothermal nature of that process seems to have its effect at the most relevant to breakup regions, i.e. the breaking interfacial surfaces. It is shown that as these surfaces can be in instant contact with a hot ambient, breakup can be greatly altered by the extent of this sudden thermal exposure, through its mostly transient and even spatial effect on physical properties of breaking interfaces. This is shown to be of significant effect on all breakup mechanisms: primary and secondary. New models are suggested for these non-isothermal phenomena, which combine transient heat-transfer with inter-phase hydrodynamic breakup, through physical properties’ dependency on temperature. Results are discussed in terms of effect on spray breakup products, and a careful comparison with the trend of a limited number of so-far available experimental results is presented.

A Phenomenological Model for Predicting Entropy Generation during Vaporization of Droplets in Engine Fuel Sprays

2014 ◽  
Vol 592-594 ◽  
pp. 1403-1407
Author(s):  
Ismail Saleel ◽  
Pramod S. Mehta
Keyword(s):  
Entropy Generation ◽  
Phenomenological Model ◽  
Fuel Injection ◽  
Engine Performance ◽  
Hydrocarbon Fuel ◽  
Combustible Mixture ◽  
Engine Fuel ◽  
Fuel Droplets ◽  
Performance And Emissions ◽  
Injection Techniques

Modern internal combustion (IC) engines employ a variety of injection techniques for preparing a combustible mixture of fuel and air. In a fuel injection-based system, the vaporization of the atomized hydrocarbon fuel droplets has significant influence on engine performance and emissions. The entropy generation associated with droplet vaporization is particularly important as it is directly related to the destruction of exergy i.e. the potential to produce useful work. Since a fuel spray could involve millions of droplets, solving the entire set of governing equations for individual droplets in a spatiotemporally discretized domain is impractical. The present work explores the utility of a simple phenomenological model in predicting the entropy generation history. The results indicate that this model ensures computational efficiency without much sacrifice in accuracy.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Effect of Fuel Injection Strategy on DPF Regeneration in Single Cylinder Diesel Engine

2015 ◽  
Author(s):  
Sungjun Yoon ◽  
Hongsuk Kim ◽  
Daesik Kim ◽  
Sungwook Park
Keyword(s):  
Diesel Engine ◽  
Fuel Injection ◽  
Operating Conditions ◽  
Experimental Results ◽  
Exhaust Gas ◽  
Post Injection ◽  
Gas Temperature ◽  
Injection Strategy ◽  
Dpf Regeneration ◽  
Exhaust Gas Temperature

Stringent emission regulations (e.g., Euro-6) force automotive manufacturers to equip DPF (diesel particulate filter) on diesel cars. Generally, post injection is used as a method to regenerate DPF. However, it is known that post injection deteriorates specific fuel consumption and causes oil dilution for some operating conditions. Thus, an injection strategy for regeneration becomes one of key technologies for diesel powertrain equipped with a DPF. This paper presents correlations between fuel injection strategy and exhaust gas temperature for DPF regeneration. Experimental apparatus consists of a single cylinder diesel engine, a DC dynamometer, an emission test bench, and an engine control system. In the present study, post injection timing covers from 40 deg aTDC to 110 deg aTDC and double post injection was considered. In addition, effects of injection pressures were investigated. The engine load was varied from low-load to mid-load and fuel amount of post injection was increased up to 10mg/stk. Oil dilution during fuel injection and combustion processes were estimated by diesel loss measured by comparing two global equivalences ratios; one is measured from Lambda sensor installed at exhaust port, the other one is estimated from intake air mass and injected fuel mass. In the present study, the differences in global equivalence ratios were mainly caused from oil dilution during post injection. The experimental results of the present study suggest an optimal engine operating conditions including fuel injection strategy to get appropriate exhaust gas temperature for DPF regeneration. Experimental results of exhaust gas temperature distributions for various engine operating conditions were summarized. In addition, it was revealed that amounts of oil dilution were reduced by splitting post injection (i.e., double post injection). Effects of injection pressure on exhaust gas temperature were dependent on combustion phasing and injection strategies.

Effect of the Fuel Injection Strategy on Diesel Particulate Filter Regeneration in a Single-Cylinder Diesel Engine

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Sungjun Yoon ◽  
Hongsuk Kim ◽  
Daesik Kim ◽  
Sungwook Park
Keyword(s):  
Fuel Injection ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Diesel Particulate ◽  
Injection Strategy ◽  
Dpf Regeneration ◽  
Exhaust Gas Temperature

Stringent emission regulations (e.g., Euro-6) have forced automotive manufacturers to equip a diesel particulate filter (DPF) on diesel cars. Generally, postinjection is used as a method to regenerate the DPF. However, it is known that postinjection deteriorates the specific fuel consumption and causes oil dilution for some operating conditions. Thus, an injection strategy for regeneration is one of the key technologies for diesel powertrains equipped with a DPF. This paper presents correlations between the fuel injection strategy and exhaust gas temperature for DPF regeneration. The experimental apparatus consists of a single-cylinder diesel engine, a DC dynamometer, an emission test bench, and an engine control system. In the present study, the postinjection timing was in the range of 40 deg aTDC to 110 deg aTDC and double postinjection was considered. In addition, the effects of the injection pressure were investigated. The engine load was varied among low load to midload conditions, and the amount of fuel of postinjection was increased up to 10 mg/stk. The oil dilution during the fuel injection and combustion processes was estimated by the diesel loss measured by comparing two global equivalences ratios: one measured from a lambda sensor installed at the exhaust port and one estimated from the intake air mass and injected fuel mass. In the present study, the differences of the global equivalence ratios were mainly caused by the oil dilution during postinjection. The experimental results of the present study suggest optimal engine operating conditions including the fuel injection strategy to obtain an appropriate exhaust gas temperature for DPF regeneration. The experimental results of the exhaust gas temperature distributions for various engine operating conditions are discussed. In addition, it was revealed that the amount of oil dilution was reduced by splitting the postinjection (i.e., double postinjection). The effects of the injection pressure on the exhaust gas temperature were dependent on the combustion phasing and injection strategies.

Investigation of a Novel Fuel Injection Technology Aimed to Reduce Cold-Start Emissions in SI Engines

2002 ◽  
Author(s):  
Brian T. Reese ◽  
Yann G. Guezennec ◽  
Miodrag Oljaca
Keyword(s):  
Fuel Injection ◽  
Cold Start ◽  
Operating Conditions ◽  
The Novel ◽  
Fuel Injector ◽  
Si Engine ◽  
Fuel Droplets ◽  
Si Engines ◽  
Atomization Characteristics ◽  
Injection Technology

A novel fuel atomization device (Nanomiser™) was evaluated under laboratory conditions with respect to its ability to reduce SI engine cold-start hydrocarbon emissions. First, comparisons between the level of atomization using the conventional, pintle-type fuel injector and the novel atomizer were carried out using flow visualization in a spray chamber and particle size distribution. The novel atomizer is capable of producing sub-micron fuel droplets, which form an ultra-fine mist with outstanding non-wetting characteristics. To capitalize on these atomization characteristics, this device was compared to a conventional fuel injector in a small, two-cylinder, SI engine under a number of operating conditions. Results show a slightly enhanced combustion quality and lean limit under warm operating conditions and a dramatic reduction in unburned HC emission under cold operating conditions, with cold emissions with the Nanomiser™ matching those with a conventional injector under fully warm conditions.

scholarly journals Experimental Methodology and Facility for the J69-Engine Performance and Emissions Evaluation Using Jet A1 and Biodiesel Blends

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4530 ◽  
Author(s):  
Gabriel Talero ◽  
Camilo Bayona-Roa ◽  
Giovanny Muñoz ◽  
Miguel Galindo ◽  
Vladimir Silva ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Fuel Injection ◽  
Engine Performance ◽  
Injection Pressure ◽  
Experimental Tests ◽  
Experimental Methodology ◽  
Injection System ◽  
Small Scale ◽  
Gas Temperature ◽  
Maximum Increase

Aeronautic transport is a leading energy consumer that strongly contributes to greenhouse gas emissions due to a significant dependency on fossil fuels. Biodiesel, a substitution of conventional fuels, is considered as an alternative fuel for aircrafts and power generation turbine engines. Unfortunately, experimentation has been mostly limited to small scale turbines, and technical challenges remain open regarding operational safety. The current study presents the facility, the instrumentation, and the measured results of experimental tests in a 640 kW full-scale J69-T-25A turbojet engine, operating with blends of Jet A1 and oil palm biodiesel with volume contents from 0% to 10% at different load regimes. Findings are related to the fuel injection system, the engine thrust, and the emissions. The thrust force and the exhaust gas temperature do not expose a significant variation in all the operation regimes with the utilization of up to 10% volume content of biodiesel. A maximum increase of 36% in fuel consumption and 11% in injection pressure are observed at idle operation between B0 and B10. A reduction of the CO and HC emissions is also registered with a maximum variation at the cruise regime (80% Revolutions Per Minute—RPM).

Experimental investigations on combustion of jatropha methyl ester in a turbocharged direct-injection diesel engine

2008 ◽  
Vol 222 (10) ◽  
pp. 1865-1877 ◽  
Author(s):  
K Anand ◽  
R P Sharma ◽  
P S Mehta
Keyword(s):  
Diesel Engine ◽  
Methyl Ester ◽  
Diesel Fuel ◽  
Fuel Injection ◽  
Peak Pressure ◽  
Direct Injection ◽  
Pressure Rise ◽  
Experimental Investigations ◽  
Injection Timing ◽  
Gas Temperature

Suitability of vegetable oil as an alternative to diesel fuel in compression ignition engines has become attractive, and research in this area has gained momentum because of concerns on energy security, high oil prices, and increased emphasis on clean environment. The experimental work reported here has been carried out on a turbocharged direct-injection multicylinder truck diesel engine using diesel fuel and jatropha methyl ester (JME)-diesel blends. The results of the experimental investigation indicate that an increase in JME quantity in the blend slightly advances the dynamic fuel injection timing and lowers the ignition delay compared with the diesel fuel. A maximum rise in peak pressure limited to 6.5 per cent is observed for fuel blends up to 40 per cent JME for part-load (up to about 50 per cent load) operations. However, for a higher-JME blend, the peak pressures decrease at higher loads remained within 4.5 per cent. With increasing proportion of JME in the blend, the peak pressure occurrence slightly advances and the maximum rate of pressure rise, combustion duration, and exhaust gas temperature decrease by 9 per cent, 15 per cent and 17 per cent respectively. Although the changes in brake thermal efficiencies for 20 per cent and 40 per cent JME blends compared with diesel fuel remain insignificant, the 60 per cent JME blend showed about 2.7 per cent improvement in the brake thermal efficiency. In general, it is observed that the overall performance and combustion characteristics of the engine do not alter significantly for 20 per cent and 40 per cent JME blends but show an improvement over diesel performance when fuelled with 60 per cent JME blend.

Visualization and Characterization of the Flashing Spray of Cryogen R404a

2011 ◽  
Author(s):  
Z.-F. Zhou ◽  
W.-T. Wu ◽  
B. Chen ◽  
L.-J. Guo ◽  
Y.-S. Wang ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Droplet Diameter ◽  
Industrial Applications ◽  
Superheated Liquid ◽  
Liquid Droplets ◽  
Spray Distance ◽  
Spray Formation ◽  
Fine Droplet ◽  
Volatile Liquids ◽  
Laser Dermatology

Flashing spray of volatile liquids is a common phenomenon observed in many industrial applications such as fuel injection of engines, accidental release of flammable and toxic pressure-liquefied gases, failure of a vessel or pipe in the form of a small hole in chemical industry, and cryogenic spray cooling in laser dermatology. In flashing spray, the volatile liquid is depressurized rapidly at the exit of a nozzle (or a hole in a vessel) and becomes superheated. Such superheated liquid (in the form of either a jet or droplets) leads to explosive atomization, leading to fine droplet sizes and a short spray distance. This paper presents an experimental investigation of flashing spray of cryogen R404a. A photographic study of the spray is first conducted, providing visualization of spray formation and showing the dynamic characteristics of the spray. Then the R404a short spray is characterized by the phase Doppler particle analyzer (PDPA). The PDPA measurements provide the distributions of the diameter and velocities of liquid droplets in the spray., showing the dramatic dynamic variation of the liquid droplets due to explosive atomization of large droplets in the region near the exit of nozzle. The data finds that the average droplet axial velocity increases first to a maximum, followed by a gradual decrease, a typical variation expected for flashing spray. During the same time period, the average droplet diameter shows a quick decrease, from early large droplets of about 30 microns in diameter to fine droplet with about 10 microns within about 40 mm spray distance. This study provides quantitative data on droplet velocity and diameter in flashing spray, useful for model validation. The qualitative results help to have a better understanding of the flashing spray atomization mechanisms for volatile cryogens.

Modeling of Droplet Dynamic and Thermal Behavior during Gas Atomization Process

2011 ◽  
Vol 672 ◽  
pp. 80-83
Author(s):  
Marius Bodea ◽  
Radu Mureşan ◽  
Virgiliu Călin Prică
Keyword(s):  
Heat Balance ◽  
Temperature History ◽  
Gas Atomization ◽  
Fragmentation Mechanism ◽  
Balance Equations ◽  
Atomization Process ◽  
Breakup Mechanism ◽  
Secondary Breakup ◽  
Physical Phenomena ◽  
The Heat Balance

The paper is focused on the physical phenomena that occurs during gas atomization process, like fragmentation mechanism of the molten stream, the secondary breakup mechanism, droplets velocities and particles temperature history. The modeling of droplet dynamic and thermal history was achieved by using a software program realized by authors, called MetLAB, using the heat balance equations between the cooling gas and the molten metal droplets.

Sign in / Sign up

Export Citation Format

Share Document