SBIR-STTR Award

A particle sizing technique that operates in conjunction with laser velocimetry is proposed. The technique uses a non-intrusive single particle counter based on a pulse height analyzer. Particle size is measured from the pulse height and velocity from doppler frequency. The technique has been used successfully to measure spray droplets between 5 and 300 um. The proposed work will develop the technique for particle measurements in rocket plumes where the particle velocities are high and the environment noisy. The method has key advantages for this application compared to other methods, including the laser doppler velocimetry (LDV) visibility approach.

The objectives of phase II will be to design, test, produce, and demonstrate a prototype particle measurement system with advanced optics and electronics to perform measurements in an actual rocket plume. This prototype must meet the requirements of bmo as well as fulfill other dod and commercial needs. The results of phase I show that the plane laser velocimeter is a powerful approach to measure the small and fast moving particles found in a rocket plume. They also point the areas that require improvement to obtain this ultimate goal. These areas are: (1) increase signal to noise ratio; (2) develop fast electronic processor. To achieve these, several steps are required and will be implemented during this next phase. They are: (a) increase the laser power; (b) test the velocimeter without fringes to increase the velocity dynamic range while reducing the frequency requirement; (c) test the incorporation of a dc (rather than ac) threshold to further discrimination ac noise; (d) explore the use of a dynamic threshold to increase the size dynamic range. The results of phase I have been obtained under simulated and controlled laboratory conditions. The objective under phase II is to demonstrate a prototype in rocket tests conducted at afrpl, as well as to illustrate the capabilities of the technique in meeting many dod and commercial needs.