In order to visualize fuel spray patterns, a high speed flow visualization system is used.  The high-speed flow visualization system consists of a 55watt copper vapor laser (CVL), high-speed 35mm drum camera, synchronization system and optics.  The CVL is a gas discharge device of 55watt average output power.  The laser emits short pulses with a pulse duration of approximately 30ns and a pulse jitter of 3ns.  The laser beam (5.08cm in diameter and of Gaussian power) is directed toward the area of interest by a set of circular mirrors 10.16cm in diameter.  A cylindrical lens and mirror are used to focus the beam onto a light sheet approximately 1mm thick.  The laser light sheet provides enough scattered light off the fuel droplets to expose the films required for the high-speed flow visualization.

 

The 35mm Cordin Drum Camera (Model 370) projects a continuous non-shuttered image onto a one-meter length of 35mm film.  The 1m length of film allows 50 full size 35mm images to be exposed.  More images are possible by reducing the width of the image. Some examples of studies which have been previously done using this technique are:

• Mass Air Flow Sensors

• Intake Manifolds

• Exhaust Manifolds

• In-Cylinder Flows

• Catalytic Converters

• Rotary Engine Flows

• Fuel Injection Events

• Air Filter/Cleaner Assemblies

Measurement and Visualization of Fuel Spray Characteristics

Worldwide variation in fuel quality can present many different challenges to the automotive industry.  Engine performance in automobiles depends on many different factors, one of which includes fuel spray quality.  Fuel spray quality can be defined as the degree of atomization and uniformity of the droplet size distribution.  Smaller droplets evaporate and move with the airflow easier.  Fuel spray quality has a decisive effect on mixture formation and combustion in the gasoline engine, which can affect engine starting, performance and emissions.  In order to thoroughly evaluate the quality of a fuel spray, two different types of laser diagnostic techniques are used to evaluate the spray characteristics.  These include a 1-D PDA system and a high-speed flow visualization system

 FUEL INJECTION VIDEO

1-D PDA SYSTEM

The system used to measure the fuel droplet size is a 1-component Dantec Dynamics particle analysis system.  The PDA system can perform non-intrusive measurements simultaneously of the size and the velocity of individual spherical particles in liquids and gaseous flows.  Phase Doppler anemometry is based on light-scattering interferometry and therefore requires no calibration. The measurements are performed at the intersection of two focused laser beams, which define the measurement volume.  The two laser beams create an interference fringe pattern of alternating light and dark planes.  As particles pass through the intersection, light is scattered onto multiple detectors, which convert the optical signal into an electrical signal representing a Doppler burst.  The signal processor measures the phase difference between the Doppler signals from the multiple detectors and calculates the particle diameter.   A radial profile for a 13 RVP fuel at 24 °C for the three fuel system pressures is presented in the figure below.  

         

Radial scan for Sauter mean diameter (SMD) spray parameter profile, 

13 RVP fuel at 24 °C and all fuel system pressures.