Modified airflow algorithm with compensation for variations in main reservoir air pressure and ambient airflow

#The present invention relates, in general, to airflow measurements and, more particularly, the instant invention relates to measurement of airflow from a main reservoir of a locomotive to the brakeline of the locomotive.

#As is generally well known in the art of controlling machinery, fluid filled conduits for control of machinery have been in widespread use for more than a century. Railroad braking systems based on a compressed air line as developed from the classical Westinghouse airbrake system are an example. Other examples may be found in the control of highway vehicles, submarines, aircraft, etc. The Westinghouse airbrake is a particularly interesting example, since it has a fail-safe feature in that failure of the brake air line resulting in a loss of brake line pressure causes application of brakes throughout the entire train.

#Generally these systems have some amount of time delay between the initiation of a control signal and the actuation of the device being controlled. These delays can be quite significant for large systems. In particular, in a railway braking system, the time needed for a pressure decrement to travel along the length of a brake air line from a locomotive to a remote part of the train consist may be as long as a minute or longer.

#FIG. 1 is a schematic of the basic elements of the invention.

#FIG. 2 is a flowchart of the process of the invention.

#Reference is herein made to the figure, which shows the basic elements of the system. The system 10 has a main reservoir 2 which receives air from supply line 4, and supplies air to outlet line 6. Reservoir 2 has a pressure connection 22 connected to pressure transducer 20 which supplies an analog signal indicating the pressure of reservoir 2 through electrical connection 24. Outlet line 6 has an orifice 8 in flowblock 9 which impedes airflow to generate a differential pressure between upstream pressure connection 42 and downstream pressure connection 43. Pressure connections 42 and 43 supply air to differential pressure transducer 40, which supplies an analog signal on electrical connection 44 to an analog to digital converter 46. Analog to digital converter 46 supplies digital signal 48 to 50 for obtaining a first calculation of flow based on the pressure drop across orifice 8 in flowblock 9.

#Electrical connection 24 carries an analog signal indicating the pressure in main reservoir 2 to an analog to digital converter 26. Analog to digital converter 26 provides digital signal 28, which represents the pressure of air in main reservoir 2.

#Air from main reservoir 2, after passing through flowblock 9, passes through downstream pipe portion 11, brake control valve 12 and brakeline 14. Brake control valve 12 provides for maintaining pressure in brakeline 14 at a constant predetermined value. The engineer of the locomotive may set this value, a brake control computer may set this value, or it may be established in another locomotive and transmitted by radio or electrical wire means.