WO2016128919A1

WO2016128919A1 - High energy-efficiency space simulator

Info

Publication number: WO2016128919A1
Application number: PCT/IB2016/050719
Authority: WO
Inventors: Maurizio Ascani
Original assignee: Angelantoni Test Technologies S.R.L. - In Breve Att S.R.L.
Priority date: 2015-02-12
Filing date: 2016-02-11
Publication date: 2016-08-18

Abstract

Space simulator (1) comprising at least one simulation room (2) and adjusting means (3) to adjust one or more thermodynamic parameters present in said room (2), said adjusting means (3) comprising a circuit (4) for circulating a pressurized gas (G), wherein said circuit is provided with at least one heat exchanger (5) for the heat exchange between said gas and said simulation room (2), with at least one compressor (6) for circulating gas (G) in said circuit and with a device (7) for reaching, at least during transient state conditions, or maintaining constant, at least in the steady-state condition, a predetermined temperature (T) of the gas (G) circulating in said circuit, said predetermined temperature being selected from a plurality of temperatures, characterized in that the density (d) of the gas (G) circulating in said circuit (4), at least in the steady-state condition, is kept constant and is comprised between 8 and 15 Kg/m3.

Description

"HIGH ENERGY-EFFICIENCY SPACE SIMULATOR" Field of the Invention

The present invention relates to a space simulator.

In particular, such a space simulator is adapted to be used for studying the response of space components and/or complete satellites when subjected to the extreme thermodynamic conditions typical of their operating environment.

According to known art, space simulators comprise a simulation room and means for adjusting the thermodynamic parameters present in said room, such as for example temperature and pressure. In particular, the means for adjusting the temperature in the room comprise a circuit for circulating a pressurized gas, such as nitrogen. Such a circuit is provided with a heat exchanger, for the heat exchange between the fluid and the simulation room, with a compressor for circulating the fluid in the circuit and with a device for adjusting the temperature of the fluid circulating in the same circuit. In general, once selected the temperature at which the gas circulating in the circuit has to operate, and thus fixed the temperature present in the simulation room, the working fluid is introduced in the circuit. During the transient state condition period, of course, both the density and the temperature will vary until reaching the final equilibrium conditions. In particular, the gas is led to a given density usually comprised between 7 and 8 kg/m , already fixed in the simulator designing stage.

Then, in order to modify the gas temperature and lead it to a predetermined value, the device for adjusting the temperature present along the circuit will feed nitrogen in the liquid state in order to cool the gas circulating in the circuit, or will heat it through an electric coil, until reaching the temperature condition required by the user. At this point, the simulator control system will modify the gas pressure so that the density can be kept always constant, until thereby reaching a new equilibrium condition. Nevertheless, such simulators of the known art suffer from the fact that both electric power and liquid nitrogen consumptions of the compressor show to be remarkable, rendering the managing costs of such equipment very high.

Therefore, object of the present invention is to significantly reduce electrical consumptions of the compressor used for the operation of the space simulator and, at the same time, also the consumption of the liquid nitrogen used.

Further object is to implement that simply and without having to excessively modify installations nowadays used for the operation of the space simulator.

These and other objects are achieved by a space simulator according to the first independent product claim. In particular, according to the invention, the space simulator comprises at least one simulation room and means for adjusting one or more thermodynamic parameters present in said room, said adjusting means comprising a circuit for circulating a pressurized gas, wherein said circuit is provided with at least one heat exchanger, for the heat exchange between said gas and said simulation room, with at least one compressor for circulating gas in said circuit and with a device for reaching, at least during transient state conditions of the space simulator, or maintaining constant, at least in the steady-state condition operation of the space simulator, a predetermined temperature of the gas circulating in said circuit, said predetermined temperature being selected from a plurality of temperatures, characterized in that the density of the gas circulating in said circuit, at least in the steady-state condition, is kept constant and is comprised between 8 and 15 Kg/m³.

In practice, by operating the compressor at densities comprised between 8 and 15

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Kg/m rather than 7-8 kg/m , as for simulators of known art, a remarkable reduction of energy costs needed for the compressor operation is obtained. In fact, the electrical power absorbed by the compressor varies with the inverse of the squared density of the gas crossing the compressor, therefore for example at an operating density of 15 kg/ m³, i.e. more than twice with respect to that one usually used in normal simulators, i.e. 7 or 8 kg/ m³, a reduction of the power absorbed by the compressor is obtained, also 75% lower than that one nowadays used. This involves the use of compressors that, despite generating rather small head effects, on the order of fractions of bar, just needed to overcome the load losses along the circuit, however operate in an working range comprised between 1 and 18 bars rather than between 1 and 8 bars, as usually occurs, in order to be able to use a gas at a density comprised

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between 8 and 15 kg/ m for a plurality of working temperatures predetermined by the user. Furthermore, said device for adjusting the temperature is arranged downstream of the compressor. In addition, the device for adjusting the temperature comprises an injector for introducing in a controlled way a fluid in the liquid state, to cool the gas circulating in said circuit, an element for heating in a controlled way the gas circulating in said circuit, and a first unit for feedback driving said injector and said heating element so that said predetermined temperature of the gas circulating in said circuit can be reached and or maintained constant.

Note that, in the case of nitrogen use in the circuit, the fluid in the liquid state is liquid nitrogen.

Again, said circuit is further provided with a device for venting the excess gas circulating in said circuit, said venting device comprising at least one density meter, at least one venting element arranged upstream of said compressor, and at least one second unit for driving the opening, or closing, of said venting element depending on the density measured by said density meter, in order to reach and/or keep constant the density of said gas circulating in said circuit.

Such a venting element for the excess gas circulating in said circuit comprises a motorized valve arranged upstream of the compressor.

Still said circuit further comprises a device to recover, at least in part, the energy of the excess gas vented by said venting element. Such a recovery device comprises at least one turbine operatively coupled with the drive shaft outputting from said compressor.

Specifically, the circuit comprises an electric motor for driving said compressor, said turbine being mechanically coupled with the drive shaft of said electric motor at least when said excess gas is vented through said venting element.

For illustration purposes only and without limitation, several particular embodiments of the present invention will be now described referring to the accompanying figures, in which:

figure 1 is a schematic view of the space simulator according to the invention;

figure 2 is a schematic view of the device for recovering the pressure of the gas vented from the venting element.

Referring in particular to such figures the space simulator according to the invention has been denoted with numeral 1.

The space simulator 1 comprises a simulation room 2 visible in the dashed line of figure 1, and means 3 for adjusting the thermodynamic parameters present in the room 2. In particular, such adjusting means 3 comprise a circuit 4 for circulating a pressurized gas G, such as nitrogen. Of course, such a circuit 4 is outside of the simulation room as well as the gas circulating in the circuit that never contacts the environment present in the simulation room 2.

Note that, despite hereinafter nitrogen will be referred to as the gas for the operation of the space simulator 1, however other gases could be used without thereby departing from the protection scope of the present invention.

Also, the circuit 4 is provided with three heat exchangers 5 for the heat exchange between the working gas circulating in the circuit 4 and the simulation room 2. Such exchangers are made and combined with the simulation room in a known way and, therefore, will not be further described herein.

In this way, the heat passing between the inside of the simulation room 2 and the heat exchangers 5 produces a temperature variation in the simulation room 2 itself. This allows varying the temperatures in the simulation room 2 and also reaching extremely low values, dramatically lower than 0°C. Furthermore, downstream of the simulation room 2, along the circuit 4, there are three chocking valves 30, each for the respective heat exchanger 5, adapted to vary the gas flow rate among the various heat exchangers 5.

Furthermore, the circuit 4 comprises a compressor 6 for the circulation of the fluid circulating in the circuit 2 and a device 7 for reaching, or maintaining constant, a predetermined temperature T of the gas G circulating in the circuit. In practice the user, depending on the temperature required in the simulation room 2, sets the aforementioned temperature T of the gas G circulating in the circuit 4. Advantageously, the density d of the gas circulating in the circuit 4, per each predetermined temperature T, is kept constant and comprised between 8 and 15 Kg/m . Such a density is fixed at the time the space simulator 1 is designed.

Advantageously, the compressor 6 is dimensioned for operating, with the highest yields, at pressures comprised between 1 and 16 bars, rather than between 1 and 8 bars as it occurs in the space simulators of the known art. However the compressor 6 is used in the circuit just for the circulation of the gas in the circuit 4 itself, i.e. to overcome the load losses present along the path of the gas G. Ultimately, the compressor 6 is able to generate a pressure jump quantifiable in fractions of bar, preferably but not limited to a pressure jump of 0.5 bar.

Employing a density comprised between 8 and 15 Kg/m leads to a significant saving of electric power and liquid nitrogen consumed by the space simulator with respect to those of known art. In fact, the power absorbed by the compressor is inversely proportional to the squared density of the gas G crossing the compressor, therefore a so high increase of the density d, even twice with respect to that one present in the circuits of the normal space simulators, results in a reduction of the absorbed power even up to 75%. In these cases, also the working pressure will be twice with respect to that one used in normal simulators in order to keep constant the ratio between temperature and pressure of the gas circulating in the circuit 4. Still according to the invention, the device 7 for adjusting the temperature is arranged downstream of the compressor 6.

Furthermore, such a device 7 for adjusting the temperature comprises an injector 8 for introducing nitrogen G' in the liquid state in a controlled way, to cool the gas G circulating in said circuit 4, an electric element 9 for heating in a controlled way the gas G circulating in said circuit 4, and a first unit (not shown) for feedback driving, thanks also to the presence of a temperature sensor (here not shown) operatively connected to the first driving unit, the operation of the injector 8 and the heating electric element 9, so that the predetermined temperature T of the gas G circulating in the circuit 4 is reached and/or maintained constant.

In this way, the temperature of the gas in the circuit 2 of the space simulator 1 can be varied in order to be able to control both the transient state condition, since the time the simulator 1 is started until the predetermined temperature T is reached, and in the steady-state condition, i.e. when the temperature T and density d values have been reached and have to be kept constant. This is obtained, with regard to the temperature through the introduction of small amounts of liquid nitrogen G' through the injector 8 or by heating the gas G circulating in the circuit 4. The operation of the injector 8 and the electric heating element 9 is driven by the aforementioned first driving unit, also based on information provided by the temperature sensor located in the circuit 4. Since such a circuit 2 operates in the steady-state condition always with gas G at constant density, also the pressure of the gas in the circuit 4 increases or decreases so that the ratio between temperature and pressure is kept constant.

In addition, the circuit 4 is further provided with a venting device 100 to vent excess nitrogen G" circulating in said circuit 2; such a venting device 100 comprises a density meter 11, a venting element 10 such as for example an electrically operated valve, arranged upstream of the compressor 6, and a second unit (herein not shown) for driving the opening or closing of the venting element 10 depending on the density d measured by the density meter 11.

In practice, once the temperature T has been fixed and the density d of the gas G circulating in the circuit 4 has been established a priori, liquid nitrogen will be filled in the circuit 4 until reaching the operating temperature T and density d of the simulator 1. Once the required density d detected by the density meter 11 has been exceeded, the venting element 10 will open the valve thereby venting the excess gas G" until recovering the predetermined density d. At the same time, the gas will reach the equilibrium pressure so that the ratio between temperature T and pressure P is always constant, as stated by the ideal gas law. Meanwhile the compressor 6 will continue to work to make the gas G continuously circulate in the circuit 4.

Again, the circuit 4 also comprises a device 20 to recover, at least in part, the energy of the excess gas G" vented by the venting element 10.

In particular, referring to figure 2, such a recovering device 20 comprises a turbine 21 operatively coupled to the drive shaft 25 of the compressor 6. More specifically and according to the embodiment herein shown, the circuit 4 comprises an alternating current electric motor 26 for activating the compressor 6; the rotating shaft 22 of the turbine 21 is thus mechanically coupled to the drive shaft 27 of the electric motor 26 at least when the excess gas G" is vented by the venting element 10.

In practice, thanks to the presence for example of a convenient electrically-driven clutch 28 synchronized with the opening of the venting element 10 for venting the excess nitrogen gas G", the mechanical coupling between the drive shaft 27 of the electric motor 26 and the rotating shaft 22 of the turbine 21 results. Such a coupling is interrupted at the time the closing of the venting element 10 occurs.

Such a solution allows further reducing the energy costs coped with for the operation of the compressor 6 and, correspondingly, costs incurred for the operation of the same space simulator 1.

Finally, it has to be observed that such a device 20 for recovering part of the energy of the excess gas G" vented from said venting element 10 can be used also in a simulator 1 wherein the pressure density of the gas G circulating in the circuit 4 is lower than 8 kg/m³, or else other. In this case, the space simulator 1 still comprises at least one simulation room 2 and means 3 for adjusting one or more thermodynamic parameters in said room 2, wherein said adjusting means 3 comprise a circuit 4 for circulating a pressurized gas G, provided with at least one heat exchanger 5, for the heat exchange between said gas and said simulation room 2, with at least one compressor 6 for varying the pressure of the gas G circulating in said circuit 4 and with a device 7 for reaching, at least during the transient state conditions, or maintaining constant, at least in the steady-state condition, a predetermined temperature T of the gas G circulating in the circuit 4, wherein the predetermined temperature is selected from a plurality of temperatures. The circuit 4, as in the embodiment of the present invention, is further provided with a venting element 10 for the excess gas G" circulating in said circuit 4, wherein said venting element 10 is arranged upstream of the compressor 6. The recovering device, then, is similar to that one described afore referring to figure 2 and comprising, in its more general implementation, at least one turbine 21 whose drive shaft 22 is operatively coupled with the drive shaft 25 of said compressor 6.

Claims

1. Space simulator (1) comprising at least one simulation room (2) and adjusting means (3) to adjust one or more thermodynamic parameters present in said room (2), said adjusting means (3) comprising a circuit (4) for circulating a pressurized gas (G), wherein said circuit is provided with at least one heat exchanger (5) for the heat exchange between said gas and said simulation room (2), with at least one compressor (6) for circulating gas (G) in said circuit and with a device (7) for reaching, at least during transient state conditions, or maintaining constant, at least in the steady-state condition, a predetermined temperature (T) of the gas (G) circulating in said circuit, said predetermined temperature being selected from a plurality of temperatures, characterized in that the density (d) of the gas (G) circulating in said circuit (4), at least in the steady-state condition, is kept constant and is comprised between 8 and 15 Kg/m³.

2. Simulator according to claim 1, characterized in that said at least one compressor operates in a pressure range comprised between 1 and 16 bars.

3. Simulator according to claim 1 or 2, characterized in that said device for adjusting the temperature is arranged downstream of said at least one compressor (6).

4. Simulator according to one or more of claims 1 to 3, characterized in that said device (7) for adjusting the temperature comprises an injector (8) for introducing, in a controlled way, a fluid (G') in the liquid state to cool the gas circulating in said circuit, an element (9) for heating, in a controlled way, the gas circulating in said circuit, and a first unit for feedback driving said injector and said heating element so that said predetermined temperature (T) of the gas (G) circulating in said circuit can be reached and/or maintained constant.

5. Simulator according to one or more of claims 1 to 4, characterized in that said circuit (4) is further provided with at least one venting device (100) to vent the excess gas (G") circulating in said circuit (4), said venting device comprising at least one density meter (11), at least one venting element (10) arranged upstream of said compressor (6), and at least one second unit for driving the opening, or closing, of said venting element depending on the density measured by said density meter, in order to reach and/or keep constant the density (d) of said gas (G) circulating in said circuit (4).

6. Simulator according to claim 5, characterized in that said circuit further comprises a recovering device (20) to recover, at least in part, the energy of the excess gas (G") vented by said venting element.

7. Simulator according to claim 6, characterized in that said recovering device comprises at least one turbine (21) whose drive shaft (22) is operatively coupled with the drive shaft (25) of said at least one compressor (6).

8. Simulator according to claim 7, characterized in that said circuit comprises an electric motor (26) for driving said at least one compressor, said turbine being mechanically coupled with the drive shaft (27) of said electric motor at least when said excess gas is vented through said venting element.

9. Simulator according to one or more of claims 1 to 8, characterized in that said gas circulating in said circuit (6) and said fluid (G¹) in the liquid state injected in the circuit (4) through said injector (8), are nitrogen.