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	Using SwRI's high-pressure, high-temperature apparatus, engineers study burning diesel sprays to evaluate spray characteristics such as jet cone angle and penetration rate.

Sprays are used in many industrial processes, and understanding spray trajectories and evaporation rates is crucial for proper implementation. Southwest Research Institute (SwRI) offers a broad spectrum of services associated with characterizing and modeling sprays in industries, such as:

• Manufacturing

• Refinery

• Agricultural

• Medical

• Automotive

Experienced engineers, chemists, and scientists, use by state-of-the-art instrumentation and unique test facilities, to provide a responsive resource for any spray-related problem. SwRI offers a wide variety of spray services, including:

• Spray characterization

• Spray modeling and simulation

	Fuel sprays are studied at realistic pressures and temperatures in this high-pressure, high-temperature apparatus.

Spray Characterization

Spray characteristics greatly affect the evaporation or congealing rate of spray droplets. To determine optimum spray characteristics under varying conditions and atomizer configurations, SwRI engineers evaluate and measure factors such as:

• Droplet size and size distributions such as Sauter mean diameter (SMD)

• Spray shape

• Droplet breakup and coalescence

• Wall film

• Penetration

• Spray velocities

• Spray jet cone angle

• Spray and droplet penetration rate

To measure these characteristics, engineers use state-of-the-art laser-based systems, high-speed video cameras and laser-strobe photography as part of a wide spectrum of spray instrumentation capability. For example:

• A Malvern^® model 2600 laser-diffraction particle-sizing instrument determines droplet size and liquid volume fraction along the laser's line-of-sight through the spray and resolves sizes from 1 to 1,200 micrometers with a dynamic range of 100 at any setting.

• A Phantom^® V7 high-speed movie camera provides full-frame framing rates up to 120,000 frames per second.

• The Schlieren imaging technique allows the visualization of index of refraction gradients in a medium.

Air pressure and temperature play key roles in determining spray angles, droplet sizes and velocities. Sophisticated test facilities enable staff members to study spray phenomena such as penetration, evaporation, and breakup over a broad range of pressures and temperatures. SwRI spray facilities include:

Low-Turbulence Ambient Spray Chamber

This spray facility passes a low-turbulence airflow, adjustable from 0.1 to 1.0 meter per second, through a 0.3-meter-square test chamber. The chamber uses a bellmouth and two honeycomb flow straighteners to smooth the airflow. A chilled metal screen condenses the spray from the airstream.

High-Pressure, High-Temperature Flowing Gas Facility

This facility permits spray tests at air pressures from 0.1 to 1.5 MPa (1 to 15 atm (atmospheric pressure)), air temperatures from 35° to 800°C, and air mass flows up to 1.1 kg per second. Flowing gas allows use of optical spray diagnostics without the spray contaminating the viewing window.

High-Pressure, High-Temperature Static Gas Apparatus

Capable of reaching air pressures of 8.3 MPa and temperatures of 550°C, SwRI's high-pressure static gas apparatus is particularly suited for diesel spray evaluation. SwRI engineers have studied diesel injection systems, including unit injectors and pump-line-nozzle systems, at injection pressures up to 300 MPa.

	Simulation of reacting high pressure diesel spray into a quiescent spray bomb allows detailed studying of spray characteristics. Visible are the equivalence ratio, the flame front, and regions of emission formation.

Spray Modeling

SwRI engineers use state-of-the-art software programs to predict the development and reaction of sprays at different pressures and temperatures. These algorithms include:

• TESS™ predicts trajectories and evaporation rates of dilute sprays. This commercially available model, which includes liquid properties for water, alcohols, and hydrocarbon fuels, is used to predict polydisperse droplet-size distributions and changes in distribution caused by droplet evaporation and the loss of droplets due to wall collisions.

• JETMIX is an SwRI-developed model that simulates fuel jet performance in diesel engines, predicting fuel-air mixing and jet penetration rates.

• JETEVAP is an SwRI-developed model that simulates fuel jet performance in diesel engines, predicting fuel-air mixing focusing on evaporation rates.

• GT-FUEL is a commercially available tool from Gamma Technologies for analysis of fuel injection and hydraulic systems. Its solver is based on the solution of compressible 1D Navier-Stokes equations, including effects of entrained gas within the liquid and cavitation; thus it allows studying and optimization of pressure wave dynamics (such as in injection systems). GT-FUEL is applicable to diesel and gasoline fuel injection systems and both common rail and unit pump systems. Sophisticated assemblies are built into its object library to model complex hydraulic components such as injectors, dampers, snubber valves and cam-driven pumps. When coupled with another SwRI model, GT-POWER, it can be used to assess the interactions between the fuel injection system parameters and combustion chamber geometry, and their effects on combustion. GT-FUEL is also applicable to other hydraulic systems such as braking, power steering, and wet clutches, as well as general hydraulics simulation.

• ANSYS CFD (FLUENT) is a commercially available 2D-3D computational fluid dynamics (CFD) code.

• CONVERGE CFD is a commercially available 3D CFD code.

	Detailed chemistry reactions in combination with fuel spray interacting with moving boundaries allows the optimization and prediction of, for example, heat release, heat transfer, and emissions in combustion engines.

The CFD packages are being used by SwRI engineers to:

• Perform detailed investigation, prediction, and optimization of spray-related phenomena ranging from injector flow over spray wall interaction to sprays being influenced by moving geometries and chemical reactions.

• Simulate the injector and injector holes using multiphase and/or volume of fluid (VOF) approaches to investigate the flow within the injector and cavitation effects.

• Simulate the spray development in spray bombs (combusting and non-combusting equal with or without reactive chemistry) to evaluate spray characteristics such as liquid penetration, droplet breakup, and SMD at any kind of initial gas composition and condition.

• Simulate sprays within moving geometries, for example, internal combustion engines including multi-species, wall interaction, and chemical reactions.

Further, SwRI engineers perform spray deflection and impact studies on deflector geometries including, for example, wall-jet or wall film models, allowing to investigate the effects on wall film thickness, species evaporation, and reactions.

Lagrangian simulation of the spray wall interaction allows studying the trajectories and distribution of droplets after impingement on obstacles. Here is shown a spray impinging a plate with the particle traces colored by velocity magnitude and mass fraction of the evaporated species.

For more information about our spray characterization, modeling, and simulation capabilities for the automotive industry, or how you can contract with SwRI, please contact Darius Mehta at dmehta@swri.org or (210) 522-2617.

autospraytechnology.swri.org

| Engine and Vehicle R&D Department | Engine, Emissions & Vehicle Research Division | SwRI Home |

Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

December 28, 2012