Abstracto

Design, Fabrication and Testing Of High Velocity Measuring Devices Used In Bird/Ice Pellet Canister Launcher Setup

Md Salman Khan, Dr. Mir Safiulla

Velocity of projectiles plays an important role in determining the response and behaviour of a target under impact. In this project metallic canister with a soft projectile, which is one of the critical dynamic components, is used to launch bird/ice pellet, to study its influence on the behaviour of aircraft and aero-engine parts. This is done by using conventional compressed air launcher which launches the projectile velocities up to 200 m/s. The canisters which house the test projectile collapse against canister arrester located at the delivery end of the launcher. The collapse characteristics of the canisters are dependent on the geometry of the tip of the arresters, material of the canisters, the shape of the canisters and the heat treatment process adapted for canisters. The impact load of the canister on the arrester can be up to several tonnes axially. This force is a function of the collapsibility of the canister at impact and in turn it is determined by the operating pressure of the launcher. It is therefore necessary to develop a velocity measuring system, which determines the dynamic axial loads on the launcher as well as the target plate, which in turn helps in studying the collapsibility parameter of the canister itself. In order to measure the high velocity of the projectile three measuring devices, namely, optical laser sensor, based on programmable logic device, copper wire and graphite rod based devices are developed and used. To provide adequate redundancy for the complex, highly dynamic and costly impact tests, two of these three velocity measuring devices are used simultaneously: (1) copper wire based sensing system and (2) graphite rod based sensing system. The measuring device input parameter is fabricated on a gun barrel with acrylic fixture at two positions at a distance of 1 m before the arrester where the canister strikes and collapses. At initial and final position, optical transmitter and receiver give the delay time when the canister passes through it by obstructing the sensing signal path. The copper wire circuit based device gives open circuit delay between the two points when canister breaks it. The time taken to travel 1m distance by the canister in the gun barrel is obtained from the device and the velocity of the canister or projectile is experimentally evaluated.