Technical field
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The invention relates to an emergency power unit for generating
electrical, mechanical or thermal power for a transportation vehicle and more
specifically for a train.
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The invention also concerns a transportation vehicle and more
particularly a train equipped with an emergency generating unit.
Background of the invention
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Modern trains are equipped with technical systems which require
continuous power for operation. Power is supplied by the electrical line along
the railway track. Of all the technical systems installed aboard trains, air
conditioning systems draw most power. These systems are used on all
modern trains, specifically high speed trains. The windows of such trains are
generally sealed and cannot be opened by travelers for safety reasons. On
the other hand, specifically high speed trains (especially those intended to
travel alternatively on dedicated tracks and on normal railway tracks
employed for traditional - i.e. not high speed - railway traffic) are frequently
subject to breakage of the pantograph connecting the locomotive to the
electrical power line with consequent power outage, that causes the train to
stop and the on-board systems to stop working. The power outage concerning
air conditioning systems and the impossibility of opening the windows to
ventilate the trains causes extreme discomfort and may even be dangerous
for passengers.
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The power drawn by each air conditioning system aboard modern
trains is considerable. Typically, the power required is in the order of 40 kW
for each carriage. Since the train may stop for a long time (in the order of 1-2
hours), ensuring sufficient autonomy for air conditioning systems for such a
long time is not possible using electrical batteries considering that they draw
so much power. This solution (and others) would be excessively heavy.
Objects and summary of the invention
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Object of the invention is to provide an emergency generating unit
which is suitable - in terms of weight, size and output power, as well as
autonomy and costs - for use on trains. Additional object of the invention is
also the realization of a train equipped with a suitable emergency generating
unit.
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Essentially, according to the invention, an emergency generating unit
for a train is characterized in that it comprises a gas turbine. The gas turbine
forms a mechanical power generator suitable to output sufficient power to
supply train utilities, specifically to supply the energy needed to run the air
conditioning system of a single carriage. Preferably, the turbine is fed with
liquid fuel, e.g. diesel engine fuel, because a sufficient amount of fuel can be
stored to obtain the required autonomy need for the use in limited space
without the weight of, for example, gaseous fuel tanks.
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In principle, the turbine can be used to directly control (via a specific
speed regulator) an air conditioning system compressor. Alternatively, the air
conditioning system can be of the absorption type and be powered by the
thermal energy of the turbine exhaust gas while the turbine provides
mechanical energy to power the other utilities of the carriage after being
transformed into electrical energy. However, since air conditioning systems on
train carriages are powered - in normal conditions of use of the train - by
electrical energy supplied by the railroad line, they are designed to use this
source of power. In order to limit the interventions needed to adapt existing
trains to fit the generating unit according to the invention, in the preferred
embodiment of the invention, the emergency generating unit comprises an
electrical generator operated by a turbine through a suitable speed reducer.
An inverter receives the electrical energy from the generator and outputs
electrical current with the characteristics needed to power the air conditioning
system and the other utilities aboard the train. The characteristics of the
inverter vary according to the type of electrical power normally found in
railway track systems. This means that the emergency generating unit can be
adapted to various railway systems which have different types of electrical
power, e.g. direct current power or alternating current power, at various
voltages.
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Although it is possible to use one emergency generating unit for the
entire train (if this is suitably short), considering the power involved according
to size and weight of the turbine, it is however advantageous to equip each
carriage in the train with a generating unit.
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According to an advantageous embodiment of the invention, the
generating unit comprises a supporting frame in which the turbine, the
electrical generator and the inverter are arranged; the frame is provided with
specific connection means to a carrying structure of the train carriage. The
frame can be advantageously shaped and dimensioned to be housed in a
compartment under the floor of the train. The turbine, the inverter, the
electrical generator and the possible mechanical reducer between turbine and
electrical generator are also dimensioned to be contained inside the frame.
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Sliding guides, integral with the carrying structure of the train and
cooperating with the frame supporting means, may be provided to facilitate
insertion and extraction of the emergency generating unit in the compartment
to make the unit easily inserted and removed.
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The generating unit may present a circuit for regulating the rotation
speed of the turbine and consequently - essentially - of the output power to
ensure the output of a various power level according to the needs and to
solve a number of problems (which will be illustrated below) related to the risk
of fumes circulating inside the train.
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Closing members are advantageously provided to close the turbine
suction and exhaust manifolds while the train is running normally to prevent
access of debris inside the turbine suction or exhaust manifolds.
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The train may be equipped with a heating system in addition to an air
conditioning system. Heating and air conditioning can possibly be obtained
using a dual-acting or reversible machine, which is capable of cooling or
heating according to requirements; the machine is powered by the emergency
generator unit in the case of an emergency. Conversely, if heating and cooling
is obtained by means of two separate systems (a cooling machine for air
conditioning, for example, and electrical resistors for heating), the generating
unit according to the invention may power alternatively either the cooling
machine or the heating resistors in the case of electrical power outage.
Otherwise, heating may be obtained by a heat exchanger which directly
employs the turbine exhaust gas and simultaneously generates mechanical
energy which is transformed into electrical energy to power the other train
utilities in the event of an emergency.
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Additional characteristics and advantageous embodiments of the
emergency generating unit and of the train using said emergency generating
unit according to the invention are recited in the annexed claims.
Brief description of the drawings
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The invention will be better understood following the description and
the annexed drawings illustrating a possible advantageous embodiment of the
invention wherein:
- Fig.1 is a schematic cross-sectional view of a train;
- Fig.2 is a block chart of the train;
- Fig.3 is a transversal cross-sectional view according to III-III in Fig.1;
- Fig.4 is a perspective view of the fuel tank;
- Fig.5 is a lateral view according to V-V in Fig.3;
- Fig.6 is an axonometric view of the emergency generating unit;
- Fig.7 is a view according to VII-VII in Fig.6;
- Fig.8 is a view according to VIII-VIII in Fig.7;
- Fig.9 is a view according IX-IX in Fig.8; and
- Fig.10 is a block chart of an emergency generator, an air conditioning
system associated thereto and a control circuit.
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Detailed description of the preferred embodiment of the invention
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Figure 1 schematically shows the front section of a train, generically
indicated by reference numeral 1. Reference numeral 3 indicates the
locomotive and references 7A and 7B indicate the first two carriages or cars
forming the train. Both traction and the various systems aboard the carriages -
specifically the air conditioning systems - are powered by the line 9 through
the pantograph 11 of the locomotive. In the event of breakdown concerning
the pantograph, the power to the utilities and to the systems in carriages 7A,
7B, ... must be provided by emergency power units which equip each carriage
5, 7, .... Figure 2 schematically shows seven train carriages numbered from
7A to 7F. Each carriage is equipped with an emergency generating unit,
schematically indicated by references 13A-13F. As indicated in detail below,
each emergency generating unit 13 is housed in a compartment underneath
the floor of the respective carriage. The compartment is equipped with a flap
for lateral access, schematically indicated by reference numeral 15 in Figure
1.
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Figure 3 shows a local transversal cross-sectional view according to
line III-III in Figure 1. In Figure 3, reference numeral 17 indicates the floor of
the carriage while reference numerals 19 and 20 indicate two adjacent
compartments, underneath the floor 17 in the transversal direction of the
carriage. Compartment 19 contains a frame 21 (see Figures from 6 to 9 in
particular) which houses a turbine unit 23 (of which reference numeral 25
indicates the exhaust), a speed reducer 27, an electrical generator 29 and an
inverter 31. The reducer 27 is arranged between the output shaft of the
turbine 23 and the input of the electrical generator 29. It reduces the turbine
revolutions to the values needed to operate the electrical generator 29. The
electrical output of the generator 29 is transformed by the inverter so that it
can power the equipment aboard the railway carriage 7. As shown in detail in
Figures 3, 6 and 7, the exhaust manifold 25 of the turbine 23 presents an end
or output mouth 25A which is in line with the bottom 19A of the compartment
19. This on one hand prevents projections of the exhaust manifold under the
lower surface of the carriage which could cause hindrance or obstruction
during normal train operation, and on the other prevents the hot fumes from
the exhaust from burning material of the rail underneath. This is thanks to
expansion and consequently cooling of the fumes in the diverging mouth of
the exhaust manifold 25.
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The conformation of the frame, the size and the arrangement of the
units exploits the space in the compartment 19 optimally.
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Within the compartment 19 two guides 33, which develop orthogonally
with respect to the longitudinal direction of the carriage 7, are fastened to the
structure forming the carriage. The frame 21 is inserted in the compartment by
means of the guides 33 and sections 35 integral with the frame by means of
which the latter rests on the guides 33. A pivoting flap 37 hinged at 39 to
carriage 7 is used to access the compartment 19.
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A fuel tank 41 is housed in compartment 20, next to compartment 19;
the tank is provided with a filler 43 facing a pivoting flap to access
compartment 21 indicated by reference numeral 45 and similar to flap 37. The
tank 41 is fastened by means of integral brackets 47 to a beam forming part of
the carriage structure. A compartment over the tank 41 houses the pump and
the fuel filters. The contour of the tank 41 and the compartment 49 for the
pump and the filters is such to exploit the available space inside compartment
20 in an optimal fashion. The tank 41 can have a capacity, for example, of
approximately 200 liters, which is sufficient to ensure an autonomy of
approximately two hours to a turbine 23 which outputs 30-60 kW. Unlike the
frame 21, which is extractable to permit maintenance operations and
interventions on the devices fitted on the frame, the tank 41 can be fixedly
fitted inside the compartment 20, since it does not require interventions in
normal conditions. The fuel filters in compartment 49 may be arranged in a
position which is sufficiently accessible from the exterior by opening the flap
45; the entire unit 41, 49 will not need to be extracted from the compartment
20 in this way.
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Figure 10 shows a block chart of the emergency generator unit, the
cooling machine for air conditioning and the control circuit. The generator unit
is generically indicated by reference numeral 13 and comprises: the turbine
unit 23, with the compressor 24, the turbine itself 26 and the combustion
chamber 28; the reducer 27; the electrical generator 29; the inverter 31. A
perforated plate 51 for measuring the rotation speed of the turbine is fitted on
the shaft of the turbine 26. Sensing means 53 (e.g. of the magnetic, optical or
other type) are associated to the plate 51 to detect the rotation speed of the
plate 51 and consequently of the turbine 26. The signal is sent by the sensing
means 53 to a signal conditioning block 55. The signal output from the block
55 is frequency-modulated and frequency is proportional to the angular
velocity of the turbine. A block 57, which receives the input signal from the
conditioning block 55, converts the frequency signal into a voltage signal. A
reference voltage signal against which the signal from block 57 is compared is
provided by a control unit 59, e.g. a microprocessor. The reference voltage
from the control unit 59 is proportional to the required rotation velocity of the
turbine and consequently to the power to be developed. The output signal
from the adder 61 is sent to a compensation network 63 whose purpose is to
avoid control loop oscillations. Suitably amplified by an amplifier 65, the output
signal from the compensation network 63 controls a motor 67 for opening and
closing a proportional valve 69 which feeds the fuel (from the tank 41) to the
combustion chamber 28.
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The output of inverter 31 has the same characteristics of the voltage
needed to power the on-board systems. For example, in the case of ETR500
trains used by the Italian railways, direct voltage at 600 V. The electrical
energy output by the inverter 31 can be used to power systems or utilities
generically indicated by reference numeral 71 aboard the carriage where the
specific emergency generating unit 13 is located. For example, it can be used
for the lighting system, opening and closing the automatic doors between
carriages, heating hot water for the on-board lavatories, etc. In winter the
output can also be used for the heating system of the carriage. A
considerable amount of the power output by the inverter 31 is used by a motor
73 which operates a compressor 75 of a cooling machine, generically
indicated by reference numeral 77 of the on-board conditioning system. The
following parts of this system are schematically indicated: a serpentine 79 for
cooling the coolant compressed by the compressor 75, an expansion valve
81, a heat exchanger 83 for cooling the air from inside the carriage through a
conduit 85. The flow of air cooled by the heat exchanger 83 is dehumidified
and partially heated by the exchanger 79 to let suitably dehumidified air into
the carriage through the conduit 87 at the required temperature. The air
conditioning system 77 interfaces with the central control unit 59.
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Other parts of the air conditioning system are not shown and are
known per se. A line 60 carries a control signal to actuators from the control
unit 59 to open and close air exchange apertures in the carriage. These
opening and closing systems are known per se and used when the train is
running to close the apertures before entering tunnels to avoid abrupt
changes of pressure. On the train according to the invention, these systems
for opening and closing the air exchange flaps have a different and additional
function which will be described below.
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When the train stops due to failure of the overhead line 9 or to the
pantograph 11, the emergency generating unit 13 is started by starting the
turbine unit 23 (e.g. by means of an electrical motor powered by a small
battery). All the emergency generating units 13 in all the carriages forming the
train can be started in normal conditions, e.g. if the train stops outside a
tunnel. To avoid the accidental access of combustion gas into the carriages 7,
the apertures or flaps provided for exchanging the air can be closed by means
of a signal by the control unit 59 on the line 60. Oxygen tanks may be
provided and release a controlled amount of oxygen via valves operated by
the control unit 59 into the carriages to ensure a sufficient amount of oxygen.
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Alternatively, the unit 59 can lower the power output by the turbine unit
23 to reduce the rpm even until the first generator 13 is stopped. In such
minimum power conditions or when the unit 13 is stopped, the vents for
exchanging air inside the carriage can be opened. The ventilation system for
exchanging air is kept running by the low power still output by the generator
13 (if this has not be switched off all together) or via a battery fitted on-board.
Air is exchanged for a sufficiently long time after which the ventilation vents
are closed and the first generating unit 13 is operated at full power again. In
this way, air is exchanged when exhaust fumes of the generating unit 13 are
minimal or entirely absent. This avoids that exhaust fumes from the turbine
accidentally entering the carriage.
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If the train stops in a tunnel and tunnel ventilation is not sufficient to
eliminate all the fumes generated by the various turbines of the emergency
generating units 13 of all the carriages, fume emissions can be reduced by
operating for pre-determined time intervals a limited number of emergency
generating units 13 in sequence, considering that particularly efficient cooling
of the ambient inside the carriages is not required in tunnels. For example,
with reference to the numbering in Figure 2, a first group 13A, 13F can be
operated for a first period of time; these units can be stopped once sufficient
cooling is obtained in carriages 7A and 7F and units 13B and 13E can be
switched on, and so forth in sequence. The sequence is then repeated for the
time needed during which the train remains stationary. Conversely, a single
generating unit 13 can be operated at a time, e.g. starting from the head of
the train with generating unit 13A to the end of the train with generating unit
13F.
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It is noted that the drawing shows only an embodiment of the invention
which can change in form and arrangement without departing from the scope
of the present invention. The presence of reference numerals in the annexed
claims has the purpose of facilitating comprehension of the claims with
reference to the description and does not limit the scope of protection
represented by the claims.