Design & Development of Air-Cooled, Under slung, Reciprocating Air Compressor Package for Air-brakes in Electric Locomotive

Abstract

Looking to the safety of human life, the air braking system in railway must have high reliability. At the speed 100 Kmph of the locomotive if necessary it should be stopped within 30 seconds with 0.93 m/s2 deceleration. The compressor package is used for supply of high-pressurized air to the breaking system. . In Electric Locomotive, there are so many electronic machineries available just behind the driver’s cabin, that an Air conditioning system is used to get best performance from these machineries. As of now, three on-board compressor packages are mounted near these machineries inside the cabin. These packages work as source of heat generation and reduce the efficiency of air conditioning system. They also occupy large space. If the package is mounted in hanging position under the electric locomotive called as underslung compressor package, will provide more space for driver’s cabin and improve the efficiency of air conditioning system. The space available under the electric locomotive is limited. The reliability of the compressor package should be high enough as well as the layout should be such that all the components should be accommodated within the space provided. Development of the compressor package has been carried out using CAE tools. The air-cooled reciprocating air compressor is fitted on skid with some accessories like intercooler, after cooler, electric motor, cooling fan, coupling, and anti-vibration mounts. These all components together make the Package. The skid is made with lifting lugs to hang the package under the electric locomotive. CAD tools are used for 3D modeling of different components and the assembly is done to avoid interference as well as to achieve compactness. The skid with lifting lugs is designed for flexural rigidity against weight of package components and acceleration forces. The FE Analysis for skid is done considering the 3*g acceleration in longitudinal direction, 1*g acceleration in transverse as well as in vertical direction as per Railway norms for high reliability. Intercooler and aftercooler are designed for air to air heat transfer, compactness, easy for tube cleaning and for worst conditions like 70o C temperature and 100 % humidity during rainy season. Manifolds of heat exchangers are designed for less weight and the strength of the same is checked against hydro test pressure via FE Analysis. Cooling fan is designed to supply enough airflow to achieve vi high efficiency of the heat exchangers, to get compactness and to get high reliability. Coupling is selected considering the misalignments between compressor and motor shafts. Anti-vibration mounts are selected for isolation of vibration due to heavy shocks that arise as the brake is applied. For the supply of air from compressor to heat exchanger and vise-versa, tubing is used instead of piping to achieve easy of assembly, easy of maintenance, reduction of number of parts, repeatability, high reliability of connections and elimination of fabrication as well as high weight. Also the location of suction filter and package layout is made for ease of maintenance. The package is designed with the help of CAD/CAE tools for high reliability and ease of maintenance with compactness. Index words - reciprocating air compressor, heat exchanger, coupling, cooling fan, anti-vibration mount, air tubing, and reliability of compressor package.