Cooling of internal combustion engines

Abstract

An engine assembly (10) for a propeller-driven aircraft is disclosed, the assembly including an engine (11), a drive shaft (13) driven by the engine (11), and a radiator (20) comprising an aperture (24) for receiving the drive shaft (13), the aperture (24) being located such that the radiator (20) substantially circumferentially surrounds the drive shaft (13). The aperture (24) may take various forms, such as a hole within the interior of the radiator (20) or a blind slit formed within the radiator (20).

Claims

1. An engine assembly for an aircraft, the assembly comprising: an engine; a drive shaft configured to be driven by the engine, the drive shaft having a distal end; a bladed propeller located at the distal end of the drive shaft with respect to the engine; a radiator comprising an inlet that is substantially parallel to the drive shaft and an aperture through which the drive shaft is received, the aperture being located such that the radiator substantially circumferentially surrounds the drive shaft, the radiator further comprising a longitudinally extending shroud, the longitudinally extending shroud comprising a tubular side wall arranged to circumferentially surround the drive shaft; characterized in that the tubular side wall of the longitudinally extending shroud extends forwardly of the inlet and towards the bladed propeller from an outer peripheral edge of the radiator, and an end of the tubular side wall of the longitudinally extending shroud distal from the radiator is adjacent to the rear side of the propeller blades, whereby the cooling of the engine is improved.

2. An engine assembly according to claim 1, wherein the aperture comprises a hole located within an interior of the radiator such that the radiator circumferentially surrounds the drive shaft.

3. An engine assembly according to claim 1 where the radiator is arranged to circumferentially surround at least 90% of the drive shaft.

4. An engine assembly according to claim 1, wherein the drive shaft is arranged for rotating a propeller.

5. An engine assembly according to claim 1, wherein the radiator comprises additional apertures for allowing air to pass therethrough.

6. An engine assembly according to claim 1, further comprising a planar backing member arranged to abut a surface of the radiator proximal to the engine, the planar backing member comprising a hole within an interior thereof through which the drive shaft is received.

7. A radiator for an aircraft, the radiator including an inlet and comprising: an aperture for receiving a drive shaft, a propeller positioned on the drive shaft, the aperture being located such that the radiator substantially circumferentially surrounds the drive shaft when the drive shaft is received in the aperture; a shroud comprising a tubular side wall having a longitudinal axis substantially parallel to the longitudinal axis of the drive shaft and the inlet, the shroud arranged to circumferentially surround the drive shaft when the drive shaft is received in the aperture, characterized in that the tubular side wall of the shroud extends from an outer peripheral edge of the radiator and forwardly of the inlet, the tubular side wall being closer to the propeller than the inlet, whereby the shroud improves the cooling of the engine.

8. A method of cooling an engine arranged for driving a bladed propeller, the method comprising: installing a radiator comprising an inlet and an aperture for receiving a drive shaft, with a propeller upon the drive shaft, wherein the inlet of the radiator is substantially parallel to the drive shaft and the radiator being installed such that the radiator substantially circumferentially surrounds the drive shaft; fluidly connecting the radiator such that the radiator receives fluid that has been heated by the engine, mounting a longitudinally extending shroud comprising a tubular side wall arranged to circumferentially surround the drive shaft on the radiator, characterized in that the shroud is mounted to extend forwardly of the inlet and towards the bladed propeller from an outer peripheral edge of the radiator, and an end of the tubular side wall of the shroud distal from the radiator is adjacent to the rear side of the propeller blades, such that the shroud enhances air flow through the radiator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

(2) FIG. 1(a) is a side view of an engine assembly in accordance with an embodiment of the present invention;

(3) FIG. 1(b) is a perspective view of the engine assembly of FIG. 1(a);

(4) FIG. 2 is an exploded perspective view of the radiator of the engine assembly illustrated in FIGS. 1(a) and 1(b);

(5) FIG. 3 is a perspective view of an alternative embodiment of a radiator suitable for use within the engine assembly illustrated in FIGS. 1(a) and 1(b); and,

(6) FIG. 4 is a flow diagram of a method of cooling an engine arranged for driving a propeller in accordance with an embodiment of the present invention.

(7) Referring to FIGS. 1(a), 1(b) and 2 of the drawings, there is illustrated an engine assembly 10. The engine assembly 10 forms part of a propeller aircraft (not shown). It is envisaged that the engine assembly 10 will be housed within a cowling (not shown) and located towards the front of the aircraft.

(8) The assembly 10 includes an internal combustion engine 11. The engine 11 is supplied with air and fuel for combustion by means of an air intake duct 12 and a fuel injector respectively. The air intake duct 12 is arranged to receive air from the front of the aircraft via an air inlet aperture formed in the engine cowling.

(9) The engine 11 is arranged for rotating a drive shaft 13. It is envisaged that the engine 11 will be a Wankel engine, in which case a proximal end of the drive shaft 13 will be located within the rotor of the engine 11. A distal end of the drive shaft 13 is coupled to a propeller (not shown) located at the nose of the aircraft.

(10) The assembly 10 further includes an engine cooling circuit for circulating cooling fluid around the engine 11. The cooling circuit comprises a pump (not shown) and a series of conduits (not shown) defined within or around the engine 11. The cooling circuit further comprises a radiator 20 mounted directly on the main engine body 11. The position of the radiator 20 proximal to the engine 11 minimises the total distance that must be spanned by the cooling circuit and hence provides a reduced cost, reduced weight, a simplified installation and a reduced risk of leaks. The radiator 20 is provided with an inlet 21 for receiving cooling fluid from the conduits defined within or around the engine cylinder block. The radiator is also provided with an outlet 22 for passing cooling fluid that has been cooled by the radiator to a downstream component in the engine cooling circuit. In certain embodiments, the cooling fluid that exits the radiator outlet 22 is immediately returned to the conduits defined within or around the engine 11 for absorption of heat generated by the engine 11.

(11) The radiator 20 is formed of a plurality of spaced apart elongate tubular elements 23 arranged for conveying cooling fluid. Together, the plurality of tubular elements 23 provide the radiator 20 with a substantially cylindrical shape, the radius of the radiator 20 being substantially greater than the longitudinal length of the radiator 20. First and second manifolds (not shown) are provided at the respective ends of the elongate tubular elements 23. In use, the cooling fluid that enters the radiator 20 at the fluid inlet 22 is divided at the first manifold between each of the tubular elements 23. The cooling fluid then passes through the tubular elements 23 and is re-combined at the second manifold for subsequent passage out of the radiator 20. The above-described structure of spaced apart tubular elements 23 provides the radiator 20 with a large surface area and therefore facilitates efficient cooling thereof. Furthermore, the elongate spaces between the tubular elements 23 define air passages through the radiator 20, thereby permitting air to flow through the radiator 20 and hence enhancing the efficiency of cooling thereof.

(12) An aperture 24 is formed in the radiator 20, though which the drive shaft 13 of the engine assembly extends. The location of the aperture 24 in the centre of the radiator 20 permits the radiator 20 to circumferentially surround the drive shaft 13. The dimensions of the aperture 24 are such that the drive shaft 13 fits within the aperture 24 without making physical contact therewith but leaving minimal free space therebetween. In the illustrated embodiment, the aperture 24 is a square having a side length marginally greater than the diameter of the drive shaft 13. In an alternative embodiment (not shown), the aperture may be circular and comprise a diameter marginally greater than the diameter of the drive shaft 13. The radiator may comprise a substantially planar backing member 30, which preferably abuts the second surface of the radiator proximal to the engine 11. Backing member 30 may include a hole through which the drive shaft 13 is received.

(13) In certain embodiments, the radiator may be provided with a longitudinally extending shroud 25, as illustrated in FIG. 3. The shroud 25 consists of a tubular side wall that extends from peripheral edge of the radiator 20. The tubular side wall of the shroud 25 thus constitutes an extension to the side wall of the radiator 20. The longitudinal axis of the tubular side wall of the shroud 25 is co-axial with the longitudinal axis of the drive shaft (not shown in FIG. 3) such that the shroud 25 circumferentially surrounds the drive shaft. When the propeller (not shown) is connected to the drive shaft, the end of the tubular side wall of the shroud distal from the radiator 20 is adjacent to the rear side of the propeller blades and marginally spaced apart therefrom. It has been found by the applicants that a shroud such as this enhances the air flow through the radiator 20 and hence improves the efficiency of engine cooling.

(14) It will be appreciated that it is possible to retro-fit a radiator 20 as described above to an existing engine assembly. With reference to FIG. 4, retro-fitting the radiator 20 comprises installing the radiator 20 around the drive shaft 13 at step 101. It is envisaged that the radiator 20 will be installed in the position illustrated in FIGS. 1(a) and 1(b). The engine cooling circuit is then fully connected at step 102. In particular, fluid conduits formed within the engine 11 are connected to the radiator 20.

(15) Once the radiator 20 is installed and is operational, the pump of the engine cooling circuit pumps cooling fluid into the conduits defined in and around the engine 11, whereupon the cooling fluid absorbs heat from the engine 11 and thus cools the engine 11. The coolant fluid from the conduits is then passed to the inlet 21 of the radiator 20 and channelled through the elongate tubular elements 23 of the radiator 20. The large surface area to volume ratio of each of the tubular elements 23 provides effective cooling of the coolant fluid, which is then passed out of the radiator 20 via the fluid outlet 22.

(16) The efficiency of cooling provided by the radiator 20 may be greatly enhanced by energising the propeller. In particular, the location of the radiator 20 downstream of the propeller enables exploitation of the high velocity air flow generated by the propeller.