FIELD OF THE INVENTION

[0001 ] The invention relates to aspirators. In particular, the invention relates, but is not limited, to aspirators to enhance propulsion systems, for example, for aviation, rockets, and marine vessels.

BACKGROUND TO THE INVENTION

[0002] Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge.

[0003] There are numerous propulsion systems for providing thrust in a fluid. For example, jet or rocket engines in gaseous fluids such as air and vessel propellers in a liquid fluid such as water. In all cases, efficiency, usually measured as fuel efficiency (but could also be electrical efficiency, for example) is an important consideration. In general, the cost of the energy (e.g. fuel or electricity) is a major commercial consideration.

[0004] For example, in the highly competitive aviation industry the cost of fuel is a significant portion of the cost of transportation. Any improvement in fuel efficiency can provide a distinct competitive advantage, not only commercially, but also from an environmental perspective in the form of reduced emissions.

[0005] There is therefore an ever present desire to improve the energy efficiency of various propulsion systems.

OBJECT OF THE INVENTION

[0006] It is an aim of this invention to provide an aspirator which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative. [0007] Other preferred objects of the present invention will become apparent from the following description.

SUMMARY OF INVENTION

[0008] In one form, although it need not be the only or indeed the broadest form, there is provided an aspirator for a propulsion system providing a thrust output, the aspirator comprising: a shroud configured to at least substantially enclose a thrust output end of the propulsion system, the shroud comprising: an inlet configured to allow fluid to be drawn inside the shroud adjacent the thrust output end of the propulsion system; and an outlet configured to allow both the thrust output of the propulsion system and the fluid drawn inside the shroud to be expelled from the shroud; wherein in use, the thrust output from the propulsion system draws fluid from adjacent the inlet into the shroud and the outlet provides thrust from both the thrust output of the propulsion system and the fluid drawn into the shroud.

[0009] The shroud is preferably movable with respect to the propulsion system. The shroud is preferably movable along a thrust axis of the thrust output of the propulsion system. Preferably the shroud is configured to slide with respect to the propulsion system. A surface of the shroud may comprise a plurality of transverse ducts.

[0010] The shroud may be mounted to the propulsion system. The shroud is preferably slidably mounted to the propulsion system.

[001 1 ] The shroud may be configured to create low pressure at its inlet by virtue of a venturi effect created by the thrust output passing through the shroud.

[0012] The aspirator may further comprise a nozzle adjacent the outlet. The nozzle is preferably adjustable. The nozzle may be adjustable to vary the size of the outlet of the shroud. The nozzle may be adjustable between a first position wherein fluid flow out of the outlet is unconstricted and a second position wherein fluid flow out of the outlet is constricted.

[0013] A plurality of aspirators may be provided for a single propulsion system. In a twin aspirator embodiment, a further aspirator may be applied to a first aspirator. The further aspirator may be larger than the first aspirator. The further aspirator may contain the outlet from the first aspirator within its (further) shroud.

[0014] The aspirator may be perforated. A perforated aspirator may comprise a plurality of ducts. The perforated aspirator may have a surface shaped like a grater (e.g. a cheese grater).

[0015] In one form, the fluid may be gaseous. The propulsion system may comprise a jet engine and the fluid comprises air adjacent an intake of the jet engine. The shroud may encapsulate the jet engine. The propulsion system may comprise a rocket and the fluid comprises air adjacent a rocket nozzle. The shroud may encapsulate the rocket nozzle.

[0016] In another form, the fluid may be a liquid. The propulsion system may comprise a propeller and the fluid comprises liquid adjacent an intake of the propeller. The shroud may encapsulate the propeller. The liquid in such embodiments is preferably water.

[0017] Further features and advantages of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:

[0019] Figure 1 illustrates a side cross-sectional view of a jet engine for an aircraft, as known in the prior art; [0020] Figure 2 illustrates a side cross-sectional view of the jet engine of figure 1 with an aspirator with nozzles in a first position, according to an embodiment of the present invention;

[0021 ] Figure 3 illustrates a side cross-sectional view of the jet engine and aspirator of figure 2, with the nozzles in a second position;

[0022] Figure 4 illustrates a side cross-sectional view of the jet engine of figure 1 with multiple aspirators, according to an embodiment of the present invention;

[0023] Figure 5a illustrates a side cross-sectional view of a rocket, as known in the prior art;

[0024] Figure 5b illustrates a bottom end view of the rocket of figure 5a;

[0025] Figure 6a illustrates a side cross-sectional view of a rocket with an aspirator, according to an embodiment of the present invention;

[0026] Figure 6b illustrates a bottom end view of the rocket of figure 6a, according to an embodiment of the present invention;

[0027] Figure 7a illustrates a side cross-sectional view of a rocket with multiple aspirators, according to an embodiment of the present invention;

[0028] Figure 7b illustrates a bottom end view of the rocket of figure 7a;

[0029] Figure 8a illustrates a side cross-sectional view of a rocket with a perforated aspirator, according to an embodiment of the present invention;

[0030] Figure 8b illustrates a bottom end view of the rocket of figure 8a;

[0031] Figure 9 illustrates a rear view of a propeller having an aspirator, according to an embodiment of the present invention; and

[0032] Figure 10 illustrates a side cross-sectional view of the propeller of figure 9. DETAILED DESCRIPTION OF THE DRAWINGS

[0033] Figurel illustrates a propulsion system, as known in the prior art, in the form of a jet engine 210 for an aircraft having an air intake end 212 and a thrust output end 214. Such jet engines have an upstream compressor coupled to a downstream turbine with a combustion chamber in-between. In the case of the turbofan engine 210 illustrated in figure 1 , there is an additional fan at the front of the engine that accelerates air in a duct bypassing the combustion chamber and turbine.

[0034] Figures 2 and 3 illustrate the jet engine 210 with an aspirator 215 attached. The aspirator 215 comprises a shroud 216 that substantially encloses the thrust output end 214 of the engine 210. The shroud 216 has an inlet 218 and an outlet 219. The inlet 218 is configured such that air can be drawn into the shroud 216 adjacent the thrust output end 214 of the engine 210. The outlet 219 is configured such that both the thrust output from the thrust output end 214 of the jet engine 210 and air drawn into the shroud through the inlet 218 is expelled from the shroud 216 simultaneously. In use, the thrust output from the jet engine 210, effectively comprising high velocity exhaust gases, draws air from adjacent the inlet 218 into the shroud 216. Thrust can then be provided to aircraft from both the thrust output of the jet engine 210 itself and also the air drawn into the shroud 216.

[0035] The aspirator 215 illustrated in figures 2 and 3 include a nozzle 225 adjacent the outlet 219. As shown by changes in configuration between figures 2 and 3, the nozzle 225 may be adjustable to provide different output characteristics. In this regard, the nozzle 225 in figure 2 is directed straight along the thrust axis of the jet engine 210 and the nozzle 225 in figure 3 has been adjusted to provide a convergent output configuration. In use, such a nozzle 225 can be adjusted, as needed, to selectively increase thrust and/or efficiency. Furthermore, as the jet engine outlet 219 is located inside the aspirator 215, the nozzle 225 may also be used to assist with decreasing, or at least directing, noise pollution. [0036] The aspirator 215 may also include a movement mechanism to allow the shroud 216 to be moved with respect to the jet engine 210. In a particularly preferred form the movement mechanism comprises a slide mechanism 220 that allows the shroud 216 to slide back and forward along the thrust axis of the jet engine 210 to attain optimal positioning during different stages of flight.

[0037] Figure 4 illustrates a jet engine 210 with multiple aspirators. In the illustrated form there is a two-stage aspirator comprising a first aspirator 215a and a second aspirator 215b. It should be appreciated that further aspirators could be added.

[0038] Whilst the use of the aspirator 215 is seen as particularly beneficial to jet engine propulsion systems such as illustrated in figures 1 to 4, it is envisaged that the technology can be applied to other propulsion systems such as, for example, rocket engines 510 as illustrated in figures 5 to 8 with an aspirator 515, or boat propellers 410 as illustrated in figures 9 and 10 with an aspirator 415.

[0039] With respect to rocket engine applications, figures 5a and 5b illustrate a rocket engine 510 without an aspirator, figures 6a and 6b illustrate a rocket engine 510 with a single aspirator 515, figures 7a and 7b illustrate a rocket engine 510 with a two stage aspirator comprising a first aspirator 515a and a second aspirator 515b, and figures 8a and 8b illustrate a rocket engine 510 with a perforated aspirated 515. With respect to the latter embodiment illustrated in figures 8a and 8b, perforations form an inlet to allow air into the aspirator 515. In one embodiment the perforations may be in the form of a plurality of transverse ducts 805 on a surface of the shroud 215 to increase fluid flow into the shroud 215. The ducts 805 may together have the appearance of a ‘cheese grater’.

[0040] With respect to water applications, figures 9 and 10 illustrate a propeller 410 providing a thrust output. The water-based aspirator 415 operates in the same manner as the previously described air based aspirators, but instead of air the fluid passing through the aspirator 415 is water. [0041 ] In use, the propulsion system (e.g. jet engine 210, boat propeller 410, or rocket engine 510) provides a thrust output in its usual operation. With the aspirator 215, 415, 515 enclosing the thrust output end of the propulsion system fluid (e.g. gas in the form of air in the case of a jet engine) a low pressure is formed at the inlet 218 of the aspirator by virtue of a venturi effect created by the thrust output of the propulsion system passing through the shroud 216. This low pressure at the inlet end assists the fluid to be drawn into the shroud 216 adjacent the thrust output end of the propulsion system. The outlet then provides thrust to the aircraft from both the thrust output of the propulsion system and the fluid drawn into the shroud inlet.

[0042] Advantageously, aspirators of the present invention can improve the efficiency of a propulsion system, reducing fuel usage which in turn can reduce operating costs and environmental impacts. Furthermore, noise pollution can reduced. The aspirator is configurable to suit different conditions and operational needs by, for example, adjusting its position relative to the propulsion system and/or adjusting its nozzles.

[0043] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The invention is intended to embrace all alternatives, modifications, and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

[0044] As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0045] In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.