Variable regulator for pneumatic airplane starters

Description

[0001] It is applicable to ground equipment designed to pneumatically start airplanes by means of a gas turbine.

[0002] Schematically, a pneumatic airplane starter of those studied here, comprises a gas turbine, with its corresponding electric starter, providing the necessary air current to start a type of airplane.

[0003] In turn the gas turbine comprises a compressor in which the outer air is compressed and accelerated, of a combustion chamber where the fuel is injected in order to obtain the necessary energy and of a turbine that transforms into rotation energy the kinetic energy of the combustion gases, causing in turn the rotation of the compressor, mounted on the same shaft thereof.

[0004] The necessary air current is obtained from the turbine conveniently bleeding the air not required by the combustion and produced by the inlet compressor or else by a special load compressor, moved by a second turbine likewise operated by the combustion gases.

[0005] The flow and air pressure values obtained from one turbine, are within some narrow limits, given by the operating interval of the compressor and the internal features of the airplane. The only operating interval of the compressor is set upon designing the starter, which determines the variety of starters that exist. Thus, if the flow-pressure values are lower than the adequate ones, the airplane cannot start, and if they are higher it should not start because it could cause short term or long term damage.

[0006] In short, no pneumatic starter presently has the possibility of changing the features of the air that is supplied for the start, adapting it to the type of airplane that is to be started.

[0007] The purpose of the variable regulator for pneumatic airplane starters is precisely the possibility to choose, for each type of airplane to start, the adequate flow and air pressure values for correct start without damage.

[0008] In outline and without going into detail, the steps to follow to design a variable regulator for pneumatic airplane starters may be the following:

1st. First of all the needs of the different types of airplane that we wish to start with the same pneumatic starter are analyzed, in other words, the limits between which the pressure and air flow to be supplied to each one of them must be, in such a way that the start is done in minimal time and so that no element of the airplane is damaged due to excess of pneumatic power.

2nd. A turbine capable of its compressor supplying, at its maximum rating, a flow and air pressure normally higher than the needed ones to start the most demanding of the planes selected is chosen. For this purpose it may be convenient to use two compressors arranged in parallel.

3rd. Instead of adjusting a single operating interval for the compressor several are set, in such a way that the airplanes can start with the correct flow and pressure values. These rating intervals of the compressor are called "start steps." Going from one start step to another can be done by opening or closing a valve between the inlet and outlet of the fuel pump, by-pass valve, in terms of the r.p.m. interval that is to be obtained.

4th. On the map of the compressor the operating point is determined by the intersection of the flow-pressure curve, imposed by the ducts and internal turbine of each airplane, with the corresponding start step.

5th. Therefore upon knowing the start step of each airplane, it suffices to choose it and connect the airplane that is to be started. The precise rating is established automatically according to the process that has just been described. Obviously the control of the by-pass valve must be connected to the control of the start step and, in the event two compressors in parallel are needed, the opening valves of the same will also be so.

6th. As an alternative to the manual selection of the adequate start, this may be done by means of a microprocessor:

a. Each plane is determined by the intersection of the flow-pressure curve, with that of a specific testing step. Introducing these values into the memory of a microprocessor, the latter can recognize the airplane and select its step.

b. The values of the intersection of the different flow-pressure curves with their corresponding start step can also be introduced into the memory. Beginning the start process with the first step and comparing the values in a short process, the suitable start step is found.

[0009] In other words, using present-day technology, it is possible to design a variable regulator for pneumatic airplane starters, which permit each plane to start with the precise conditions.

[0010] The economic advantages of using pneumatic starters useful for different types of airplanes, instead of for a single type, are obvious, due to the savings involved: smaller number of starters for the same airplanes, fewer spare parts and simpler maintenance service.

Claims

1. Variable regulator for pneumatic airplane starters, characterized because it is capable of supplying different flow and air pressure values, to adapt to the needs of the airplane that must start. Once the airplane is connected to the pneumatic starter, the suitable start step is chosen by hand, whereby the arrival of fuel to the combustion chamber remains regulated by different mechanisms to obtain the r.p.m. interval that the compressor must have to duly start the airplane.

2. Equipment according to the above claim, characterized because optionally the selection of the start step, can be done automatically by a microprocessor, analyzing the flow-pressure values obtained upon starting up the starter once it has been connected to the airplane that is to be started.