Abstract: A particle separator stage in a particle separator includes an inflow passage of generally annular, axially facing form. In other embodiments, an asymmetric geometry is disclosed in which the major flow is taken from one side only. These features combine to allow compact, multi-stage separators to be produced. Also disclosed an arrangement in which the flow rate at a location within the separator stage is measured and used to control the flow rate there or elsewhere.

Abstract: A flow control actuator 10 for a body exposed to fluid flow comprises first and second flow surfaces 14, 16 spaced to define an elongate gap 20 therebetween. An elongate control element is disposed in or adjacent the gap and has an externally facing arcuate surface and defines a first slot 24 between the control element and said first flow surface and a second slot between said control element and said second flow surface 26. The control element 22 is moveable to allow the width of said slots to be adjusted generally proportionally. The flow of pressurized flow control fluid passes from a plenum chamber 30 out through one or both slots 24, 26 to be deflected around the arcuate surface under the influence of the Coanda effect. The flow control actuator 10 may be provided in the trailing or leading edge of an aerofoil; alternatively it may be provided between two surfaces spaced to provide said gap but otherwise providing a generally continuous surface.

Abstract: The thrust vectoring apparatus comprises: a housing defining a primary outlet for emitting the primary jet; Coanda surfaces extending from opposing regions of said housing, and radially spaced from the primary outlet such that a step is defined between each Coanda surface and the primary outlet; ducts leading from a fluid source to secondary outlets; and flow control means operable to control the mass flow through the secondary outlets. When the jet engine operates to exhaust a primary jet through the primary outlet, low pressure regions are formed in the vicinity of the steps. Each secondary outlet is located adjacent one of the Coanda surfaces so as to emit a secondary flow into a low pressure region. On activation of the secondary flow by the flow control means, the primary jet is entrained by the Coanda surface opposing the Coanda surface adjacent said the secondary outlet from which the secondary flow has been emitted.

Abstract: A bonding tool and method A bonding tool and method for bonding together layers of a MEMS transducer device, including at least one layer of a piezoelectric material, and an intermediate reinforcing layer of titanium, or other metal, comprising: positioning the layers above one another and spaced apart by means of spacing members, heating said layers to a bonding temperature, and retracting the spacing members so as to bring the layers together under pressure to effect a bond between adjacent surfaces of the layers, wherein a press head is employed with a compliant caul for evenly distributing the press force; and permitting said layers to cool to an operating temperature in which said piezoelectric layer is under compressive strain and the titanium layer is under tensile strain.

Abstract: To provide an indication of whether airflow is separated, as opposed to other states of flow, over a surface, two or more adjacent sensors at a location on the surface each produce an analogue signal representative of airflow. The analogue signals are correlated with each other, and the degree of correlation indicates whether the airflow is in a separated state. The correlation may be carried out by comparing processed values of the analogue signals, and thresholding the comparison result.

Abstract: In order to discriminate between laminar flow and turbulent flow states, and to provide an indication, e.g. to a pilot of an aircraft of air flow over an aircraft wing, a sensor mounted on the wing provides an analogue signal of airflow, and an intermittency value of the analogue signal is derived in analogue circuitry including an AC coupling of the signal to an integrator for integrating the signal for a preset time. The integrated value is compared with a threshold value to indicate whether the intermittency represents quiet laminar flow or noisy turbulent flow.

Abstract: A bonding tool and method A bonding tool and method for bonding together layers of a MEMS transducer device, including at least one layer of a piezoelectric material, and an intermediate reinforcing layer of titanium, or other metal, comprising: positioning the layers above one another and spaced apart by means of spacing members, heating said layers to a bonding temperature, and retracting the spacing members so as to bring the layers together under pressure to effect a bond between adjacent surfaces of the layers, wherein a press head is employed with a compliant caul for evenly distributing the press force; and permitting said layers to cool to an operating temperature in which said piezoelectric layer is under compressive strain and the titanium layer is under tensile strain.

Abstract: A millimetre-scale pulse jet engine comprises an engine body that defines a combustion chamber, a fuel, an air intake, and an exhaust. The fuel inlet is arranged to inject fuel directly into the combustion chamber. The air intake and the exhaust are in fluid communication with the combustion chamber, and the combustion chamber is configured such that air from the air intake and fuel from the fuel inlet cyclically combust in the combustion chamber to produce exhaust gases.

Abstract: A sensor device for sensing air flow speed at the exterior of an aircraft, comprising a substrate having an upper side on which is mounted a diaphragm over an aperture or recess in the substrate, the diaphragm being thermally and electrically insulative, and mounting on its upper surface a heating element comprising a layer of resistive material, and wherein electrical connections to the heating element are buried in the diaphragm and/or the substrate, and provide electrical terminals at the lower side of the substrate. The heating element is exposed to the environment, but the remaining electrical parts of the device are not exposed.

Abstract: A flow control actuator 10 for a body exposed to fluid flow comprises first and second flow surfaces 14, 16 spaced to define an elongate gap 20 therebetween. An elongate control element is disposed in or adjacent the gap and has an externally facing arcuate surface and defines a first slot 24 between the control element and said first flow surface and a second slot between said control element and said second flow surface 26. The control element 22 is moveable to allow the width of said slots to be adjusted generally proportionally. The flow of pressurised flow control fluid passes from a plenum chamber 30 out through one or both slots 24, 26 to be deflected around the arcuate surface under the influence of the Coanda effect. The flow control actuator 10 may be provided in the trailing or leading edge of an aerofoil; alternatively it may be provided between two surfaces spaced to provide said gap but otherwise providing a generally continuous surface.

Abstract: A particle sampling device is disclosed for separating and collecting particles of at least first and second mass/size ranges from an ambient fluid (e.g. gaseous) medium in which they are present, particles of the first range being of generally larger size/mass than particles of the second range. The separator is especially designed for use in an air sampling device which is designed for rapid detection of micro-organisms such as bacteria, viruses, pathogens and the like, and is designed to be portable so that it can be readily and rapidly deployed in both civilian and military environments and can be used indoors and outdoors; it can also be designed for personal use.

Abstract: A method of forming a surface of micrometer dimensions conforming to a desired contour for a MEMS device, the method comprising providing a crystalline silicon substrate with a recess in an upper surface, providing a thinner layer of crystalline silicon over the upper surface of the substrate, fusion bonding the layer to the substrate under vacuum conditions, and applying heat to the layer and applying atmospheric pressure on the layer, such as to plastically deform the diaphragm within the recess to the desired contour. The substrate may form the fixed electrode of an electrostatic MEMS actuator, operating on the zip principle.

Abstract: A particle sampling device is disclosed for separating and collecting particles of at least first and second mass/size ranges from an ambient fluid (e.g. gaseous) medium in which they are present, particles of the first range being of generally larger size/mass than particles of the second range. The separator is especially designed for use in an air sampling device which is designed for rapid detection of micro-organisms such as bacteria, viruses, pathogens and the like, and is designed to be portable so that it can be readily and rapidly deployed in both civilian and military environments and can be used indoors and outdoors; it can also be designed for personal use.

Abstract: A separator is disclosed for separating particles of at least first and second mass/size ranges from an ambient fluid (e.g. gaseous) medium in which they are present, particles of the first range being of generally larger size/mass than particles of the second range. The separator is especially designed for use in an air monitoring device which is designed for rapid detection of micro-organisms such as bacteria, viruses, pathogens and the like, and is designed to be portable so that it can be readily and rapidly deployed in both civilian and military environments and can be used indoors and outdoors; it can also be designed for personal use.

Abstract: This invention relates to a method of controlling vortex bursting on an aerodynamic surface (20) associated with separated flows and, in particular, relates to control of separated flows over aerodynamic or hydrodynamic surfaces (20) that may have highly swept leading edges (26). A method of controlling vortex bursting on an aerodynamic surface or a hydrodynamic surface (20) is provided, the surface (20) comprising a gas source (22) located on or in the surface (20) and the method comprising the step of repeatedly operating the gas source (22) thereby to eject a flow of gas into an airflow passing over the surface (20). Effective control of the frequency at which the gas source (22) is operated has been found to reduce pressures on the surface (20) caused by vortex bursting. The present invention also provides a synthetic jet actuator (22) and an aerodynamic or hydrodynamic surface (20) comprising a plurality of such discrete synthetic jet actuators (22).

Abstract: A ring-wing aircraft suited particularly, although not exclusively, to use in micro-unmanned air vehicles (UAV's) with ring-wings. An aircraft (10) according to the invention comprises a ring-wing (11) defining a duct (16) with a longitudinally-extending central axis (31), propulsion element (15) located within the duct and moveable aerofoils (13, 18) for controlling the aircraft in flight, the ring-wing being truncated obliquely at one end, that end being the rear (11b) when in horizontal flight, to form a ring-wing with opposed sides of unequal length. This arrangement produces center of mass offset from the central axis of the ring-wing, the pendulum effect will ensure that the aircraft will roll so that its center of mass will always be at the lowest height possible when the aircraft is airborne. Therefore the aircraft has a preferred orientation, and the control surfaces can be oriented with respect to this preferred orientation.

Abstract: This invention relates to ring-wing aircraft and is suited particularly, although not exclusively, to use in micro-unmanned air vehicles (UAV's) with ring-wings.