GB2323973A

GB2323973A - Electrical generator

Info

Publication number: GB2323973A
Application number: GB9706510A
Authority: GB
Inventors: Mervyn Wilson; Nigel Graham Wadforth
Original assignee: BELLE ENGINEERING
Current assignee: BELLE ENGINEERING
Priority date: 1997-04-01
Filing date: 1997-04-01
Publication date: 1998-10-07
Also published as: GB9706510D0

Abstract

An electrical generator 10 comprises an alternator 14 and an engine 16 for driving it, located on a base portion 12. The engine and alternator have separate cooling air flows: the alternator airflow enters the base portion through inlets 22,66 and flows through ducts 24, 68, exiting at outlet 28 (figure 7), while the engine air path comprises inlet 18, and duct 20. The engine exhaust gases flow through exit duct 60 to outlets 26,29 via a silencer 50. A fuel tank (86, figure 8) is also contained within the generator, which is cooled by fan (42, figure 5).

Description

ELECTRICAL GENERATOR This invention relates to electrical generators, in particular to generators that utilise an engine to drive an alternator.

Conventional engine driven electrical generators are generally quite noisy.

However, it is desirable that the noise levels produced during operation of the generator are minimised.

Furthermore, problems are often encountered with respect to the operating temperatures of such generators. By improving the efficiency of heat dissipation, the temperature at which the given engine output is achieved is reduced. Engines are rated to operate at temperatures below a defined maximum temperature (with respect to ambient temperature). Therefore, increasing the efficiency of heat dissipation may lead to an increase in the maximum output that the engine can produce whilst remaining within its specified temperature range. Another consequence of generators running at elevated temperatures is that such temperatures can preclude the provision of a fuel tank within the device.

The present invention alleviates the above mentioned problems.

According to the invention there is provided an electrical generator comprising a base portion on which are located an alternator and an engine for driving said alternator, the generator having an engine air flow for cooling said engine and an alternator air flow for cooling said alternator, in which the base portion comprises: an engine air inlet and an engine air duct extending therefrom for conducting the engine air flow to the engine; and an alternator air inlet and an alternator air duct extending therefrom for conducting the alternator air flow to the alternator; and in which the alternator air flow and engine air flow exit from the generator from outlets which are substantially spaced apart from said engine air inlet and alternator air inlet.

The base portion may comprise an aperture in the upper face thereof in which the engine is located.

The air engine air duct and alternator air duct may both extend over at least 60% of the length of the base portion.

The engine air duct may comprise a first section extending from the engine air duct and passing beneath a first portion of the engine, and a second section, in communication with the first section and passing beneath a second portion of the engine.

The first section of the engine air duct may comprise an air splitter adapted to deflect a portion of the engine air flow upwards towards the first portion of the engine.

A cowling may cooperate with the engine to enhance the engine air flow from the engine air duct to the engine.

The engine block may be provided with a heatsink.

The base portion may further comprise a combustion air inlet and a baffled combustion air duct extending therefrom for conducting, at least in part, a combustion air flow to the engine to aspirate same.

The engine may be further cooled by a top end air flow produced by a fan disposed above the engine which draws air through at least one top end air duct.

Exhaust gases from the engine may be passed through a silencer. The silencer may comprise a main chamber containing: at least one sub-chamber partitioned into two compartments by a separator having a plurality of apertures disposed therein; inlet means for conducting exhaust gases from the engine to a sub-chamber; and outlet means for venting exhaust gases from a sub-chamber to the atmosphere; in which the sub-chamber or sub-chambers are connected so that exhaust gases enter each sub-chamber via one compartment thereof, and exit each sub-chamber via the other compartment thereof.

Additionally, the silencer may comprise: a first sub-chamber and a second sub-chamber spaced therefrom, the inlet means conducting exhaust gases from the engine to a first compartment of the first sub-chamber; communicating means for conducting exhaust gases from the second compartment of the first sub-chamber to a first compartment of the second sub-chamber; in which the outlet means vents exhaust gases from the second compartment of the second sub-chamber to the atmosphere.

The silencer may be positioned in the engine air flow, thereby cooling said silencer.

The silencer may be spaced from the combustion air duct by an insulated region.

The base portion may further comprise an auxiliary alternator air inlet and an auxiliary alternator air duct extending from said auxiliary alternator air inlet and communicating with the alternator air duct.

A fuel tank may be contained within the generator housing. The fuel tank may be located upon a tray adapted to collect spilt fuel, the tray having a drain for removing said spilt fuel from the generator.

The region around the fuel tank may comprise an air duct for transmitting a cooling air flow from internal generator airways to said fuel tank. The cooling air flow may be the top end air flow.

The generator may comprise a heatsink attached to the oil sump of the engine. The heatsink may comprise : an engagement part adapted for liquid tight engagement with the oil sump; heat dissipation means and heat conducting means, said heat conducting means being in contact with the oil and in thermal communication with the heat dissipation means. The heatsink may function as a dipstick.

An electrical generator in accordance with the invention will now be described with reference to the following drawings, in which:- Figure 1 shows a partial, exploded perspective view of an electrical generator; Figure 2 shows a plan view of the base portion; Figure 3 is a cross sectional view along the line A-A at Figure 2; Figure 4 shows the engine cowling; Figure 5 shows the fan duct a) in plan view, b) viewed from the side and c) viewed from the front; Figure 6 shows a cross sectional view of the silencer; Figure 7 shows (a) the path of the alternator air flow in the region of the alternator; (b) a cross sectional view along the line B-B' of Figure 7 (a) and (c) a cross section view along the line C C' of Figure 7 (a); Figure 8 shows the fuel tank, cooling duct and collection tray with drain; and Figure 9 is a side view of an oil sump heatsink.

Figure 1 is a partial exploded view of an electrical generator 10 comprising a base portion 12 on which are located an alternator 14 and an engine 16 for driving said alternator 14, the generator 10 having an engine air flow for cooling said engine 16 and an alternator air flow for cooling said alternator 14, in which the base portion 12 comprises: an engine air inlet 18 and an engine air duct 20 extending therefrom for conducting the engine air flow to the engine 16; and an alternator air inlet 22 and an alternator air duct 24 extending therefrom for conducting the alternator air flow to the alternator 14; and in which the alternator air flow and engine flow exit from the generator 10 from outlets 26, 28, 29, which are substantially spaced apart from said engine air inlet and alternator air inlet (note that outlet 28 is not shown in Figure 1, but is shown in Figure 7). The outlet 29 is a grille covering an aperture in the bottom face of the base portion 12.

The base portion 12 comprises an aperture 12a in the upper face 12b thereof in which the engine is located.

Figure 2 shows a plan view of the base portion 12, and depicts the engine air flow (solid arrows) and alternator air flow (dashed arrow) through the base portion 12. The engine air duct 20 and alternator air duct 24 both extend over at least 60% ofthe length of the base portion (in the embodiment depicted in Figures 1 and 2 their longitudinal extensions are ca 85% and 100% respectively). The drawing of air over such long path lengths results in a reduction in noise levels. Furthermore, by drawing air into the generator on one side lOa of the generator and expelling hot air from outlets substantially spaced therefrom, there is no possibility of recycling hot, exhaust air back into the air cooling system. Further still, the passage of air through the ducts gives rise to a wind chill effect, providing further temperature reduction.

As shown in Figures 1 and 2, the engine air duct 20 comprises a first section 20a extending from the engine air inlet 18 and passing beneath a first portion of the engine 16 and a second section 20b, in communication with the first section 20a and passing beneath a second portion engine 16. As shown in Figures 2 and 3, the first section 20a ofthe engine air duct 20 can comprise an air splitter 30 adapted to deflect a portion ofthe engine air flow from the engine air duct 20 to the first portion ofthe engine 16, which in fact is the oil sump of the engine 16. This feature provides further cooling of the generator 10. The engine 16 employed may be an internal combustion engine of spark ignition or compression ignition type. The undersides of many engines are ribbed, which makes the provision of a heatsink in this region rather difficult. However, if the provision of a heatsink on the underside ofthe engine is possible, then this would provide a suitable alternative means of cooling.

The engine air flow proceeds into the second section 20a of the engine air duct 20 and thence through the aperture 31 to the engine 16. A cowling 32 (Figure 4) cooperates with the engine 16 to enhance the engine air flow from the engine 16 which has drawn air from air duct 20. The cowling 32 is in addition to the standard engine covers, and is fitted above the cylinder block attached by means of a recoil housing fixing screw. The engine air flow is then inducted into the internal air cooling system of the engine 16.

The engine block is provided with an additional heatsink(s), providing further temperature reduction. Such heatsinks may be located in any area running at high temperature during use.

The base portion 12 further comprises a combustion air inlet 34 and a baffled combustion air duct 36 extending therefrom for conducting, at least in part, a combustion air flow to the engine 16 to aspirate same. The provision of baffles 36a, 36b results in a longer path length for the air flow which reduces noise levels. As explained in more detail below, the combustion air flow passes from the combustion air duct 36 to an air conveying tube 38 and thence to an air filter housing 40 (see Figure 5) before entering the engine carburettor.

The engine 16 is further cooled by a top end air flow produced by a fan 42 disposed above the engine 16 (see Figure 5) which draws air through three top end air ducts 44a, 44b 44c. The provision of the third, shorter, top end air duct 44c improves the air flow characteristics in the present embodiment. However, the use of fewer, or indeed more, top end air ducts, including vertical or angled down draught ducting, is feasible.

It is possible to use two air ducts, and it may well be possible to usefully employ a single air duct if the use of a different engine were contemplated : advantageous duct configurations are readily apparent to the skilled person. The manifold 46 which comprises the three top end air ducts 44a, 44b, 44c also comprises a conduit 40 which cooperates with the carburettor (not shown) of the engine 16. The combustion air flow enters the conduit 40 from the air conveying tube 38.

Exhaust gases from the engine are passed through a silencer 50 shown in Figure 6. The silencer comprises a main chamber 50a containing: a first sub-chamber 52 and a second sub-chamber 54 spaced therefrom, the first sub-chamber 52 being partitioned into two compartments 52a and 52b by a first separator 52c having a plurality of apertures 52d disposed therein, the second sub-chamber 54 being partitioned into two compartments 54a and 54b by a second separator 54c having a plurality of apertures 54d disposed therein; inlet means 56 for conducting exhaust gases from the engine 16 to a first compartment 52a of the first sub-chamber 52; communicating means 58 for conducting exhaust gases from the second compartment 52b of the first sub-chamber 52 to a first compartment 54a of the second sub-chamber 54; and outlet means 60 for venting exhaust gases from the second compartment 54b of the second sub-chamber 54 to the atmosphere.

The inlet means 56 is a pipe having a capped exit and a plurality of longitudinally spaced apertures 56a. Concerning the first chamber 52, the volume of the first compartment 52a is approximately twice that of the second compartment 52b. The plurality of apertures 52d comprises sixteen holes of 5mm diameter. Concerning the second chamber 54, the volume of the second compartment 54b is approximately twice that ofthe first compartment 54a. The plurality of apertures 54d comprises twenty holes of 3.5mm diameter. The communicating means 58 and the outlet means 60 are appropriately shaped hollow tubular members. Modifications to the design described above would readily suggest themselves to the skilled person. For example, the number and diameter of the apertures may be varied. Furthermore, the silencer is not restricted to two sub-chambers - one or more sub-chambers may be employed. The silencer 50 is optionally packed with a fibrous heat resistant insulating medium such as "rock wool", and has been demonstrated to run very quietly.

The silencer 50 is positioned in the engine air flow, thereby cooling said silencer 50. The engine air flow passing the silencer is the air flow exiting the cooling system of the engine 16 together with the overhead air supply (described below). The engine air flow post-engine is conducted partially in an exit duct 60 formed in the base portion 12. The silencer 50 is disposed within the exit duct 60. The exit duct 60 exhausts the engine flow to atmosphere via engine air flow outlets 26, 29.

The silencer 50 is spaced from the combustion air duct 36 by an insulated region 64 comprising, for example, rock wool fibre. The provision of a free passage between the silencer 50 and the combustion air duct 36 is possible.

Turning now to the alternator air flow, shown in Figure 2 in the region of the base portion 12 in dashed arrows. In addition to the alternator air inlet 22 and alternator air duct 24, the base portion 14 further comprises an auxiliary alternator air inlet 66 disposed in the first side 10a of the generator 10 and an auxiliary alternator air duct 68 extending from said auxiliary alternator air inlet 66 and communicating with the alternator air duct 24. It has been found that the auxiliary alternator air duct 68 is useful in providing cooling of the alternator, particularly the side 1 4a of the alternator positioned nearest the auxiliary alternator air duct 24 and the backing plate 74 adjacent thereto. The auxiliary alternator air duct 68 also keeps adjacent duct walls cool, thereby reducing the effect of close proximity heat sources.

Figure 7 shows the path ofthe alternator air flow from the alternator air duct 24 and the auxiliary alternator air duct 68 through an aperture 70 into a region 72 in which is located the alternator 14. The region 72 is bounded by a backing plate 74, a panel 75, which may be covered or coated with a noise absorbent medium 200, and a wall 80.

The air flow enters the alternator 14 and cools all rotating and static component parts thereof before being expelled through air outlet ducts 201 into the region 72. The air flow (depicted in Figure 7 as solid arrows) exits through the wall 80 via air flow outlet 28.

A fuel tank 86 is contained within the generator 10 (Figure 8). The fuel tank 86 is located upon a tray 88 adapted to collect any spilt fuel, the tray 88 having a drain 90 for removing spilt fuel from the generator 10. The tray 86 is positioned adjacent an electrical control panel 92 and a central divider 74. The central divider 94 has an aperture 96 - also shown in Figure 5 - which permits air from the fan 42 to cool the fuel tank 86. It is possible to utilise an arrangement in which this air flow is reversed - in other words, the aperture 96 serves as a top end air duct. Cooling of the fuel tank 86 is important, because the maximum temperature that the fuel tank should attain is 600C which respect to ambient temperature. It is extremely advantageous that a fuel tank is provided within the generator 10, since the generator 10 does not require frequent external refuelling.

The generator 10 may also comprise a heatsink 96, shown in Figure 9, which is attached to the oil sump ofthe engine. The heatsink comprises: an engagement part 98 adapted for liquid tight engagement with the oil sump; heat dissipation means 104 and heat conducting means 100, said heat conducting means 100 being in contact with the oil and in thermal communication with the heat dissipation means 104.

In Figure 9, the heatsink also functions as a dipstick, the heat conducting means 100 comprising a dipstick in contact with the oil and forming part of a unitary body 102. Serration and/or annular grooves on the dipstick 100 form calibration marks to depict the required engine lubricating oil levels. The heat dissipation means 104 are in threaded engagement with the unitary body 102. It will be appreciated that a variety of heat dissipations configurations well known in the art, such as a rose structure, or fins, may be employed. The heatsink of Figure 9 provides a significant reduction in engine oil temperature.

The oil sump heatsink of the present invention is not limited to the dipstick configuration of Figure 9. The heatsink might be incorporated into the filler, or even located into a chosen portion of the sump body below the oil line.

It will be appreciated that use of the oil sump heatsink is not restricted to electrical generators of the type described herein : rather. the oil sump heats ink is applicable to temperature reduction of a wide range of motors and engines. Furthermore it should be noted that the device can be used in a heating application, rather than a heat removing application, for example with a heavy oil installation in which oil fluidity must be maintained.

The generator 10 is provided with a cover (not shown) having suitable louvres and/or lattice form face piercings positioned adjacent the inlets and outlets. The generator is rated at 2.2kW maximum output, and produced noise levels of 63dB[A] at three quarters output. Furthermore, the cooling system described above results in excellent generator temperature characteristics. Typically, the engine employed has a maximum working temperature differential of 100"C above ambient temperature, up to a maximum absolute temperature of 140"C. The generator ofthe present invention runs at 10 to 12"C within this specification, which complies with engine manufacturers warranty specifications.

Claims

1. An electrical generator comprising a base portion, on which are located an alternator and an engine for driving said alternator, and having an engine air flow for cooling said engine and an alternator air flow for cooling said alternator, in which the base portion comprises: an engine air inlet and an engine air duct extending therefrom for conducting the engine air flow to the engine; and an alternator air inlet and an alternator air duct extending therefrom for conducting the alternator air flow to the alternator; and in which the alternator air flow and engine air flow exit from the generator from outlets which are substantially spaced apart from said engine air inlet and alternator air inlet.

2. A generator according to claim 1 in which the base portion comprises an aperture in the upper face thereof in which the engine is located.

3. A generator according to claim 1 or claim 2 in which the engine air duct and alternator air duct both extend over at least 60% of the length of the base portion.

4. A generator according to any of claims 1 to 3 in which the engine air duct comprises a first section extending from the engine air inlet and passing beneath a first portion of the engine, and a second section, in communication with the first section and passing beneath a second portion of the engine.

5. A generator according to claim 4 in which the first section ofthe engine air duct comprises an air splitter adapted to deflect a portion of the engine air flow upwards towards the first position of the engine.

6. A generator according to any of the previous claims in which cowling cooperates with the engine to enhance the engine air flow from the engine air duct to the engine.

7. A generator according to any of the previous claims in which the engine block is provided with a heatsink.

8. A generator according to any of the previous claims in which the base portion further comprises a combustion air inlet and a baffled combustion air duct extending therefrom for conducting, at least in part, a combustion air flow to the engine to aspirate same.

9. A generator according to any of the previous claims in which the engine is further cooled by a top end air flow produced by a fan which draws air through at least one top end air duct.

10. A generator according to any of the previous claims in which exhaust gases from the engine are passed through a silencer.

11. A generator according to claim 9 in which the silencer comprises a main chamber containing: at least one sub-chamber partitioned into two compartments by a separator having a plurality of apertures disposed therein; inlet means for conducting exhaust gases from the engine to a sub-chamber; and outlet means for venting exhaust gases from a sub-chamber to the atmosphere; in which the sub-chamber or sub-chambers are connected so that exhaust gases enter each sub-chamber via one compartment thereof, and exit each sub-chamber via the other compartment thereof.

12. A generator according to claim 11 in which the silencer comprise: a sub-chamber and a second sub-chamber spaced therefrom, the inlet means conducting exhaust gases from the engine to a first compartment of the first sub-chamber; communicating means for conducting exhaust gases from the second compartment of the first sub-chamber to a first compartment of the second sub-chamber; in which the outlet means vents exhaust gases from the second compartment of the second sub-chamber to the atmosphere.

13. A generator according to any of claims 10 to 12 in which the silencer is positioned in the engine air flow, thereby cooling said silencer.

14. A generator according to any of claims 10 to 13 when dependent on claim 8 in which the silencer is spaced from the combustion air duct by an insulated region.

15. A generator according to any of claims 1 to 14 in which the base portion further comprises an auxiliary alternator air inlet and an auxiliary alternator air duct extending from said auxiliary air inlet and communicating with the alternator air duct.

16. A generator according to any of the previous claims in which a fuel tank is contained within the generator housing.

17. A generator according to claim 16 in which the fuel tank is located upon a tray adapted to collect spilt fuel, the tray having a drain for removing said spilt fuel from the generator.

18. A generator according to claim 16 or claim 17 in which the region around the fuel tank comprises an air duct for transmitting a cooling air flow from internal generator airway, to said fuel tank.

19. A generator according to claim 18 when dependent on claim 9 in which the cooling air flow is the top end air flow.

20. A generator according to any of the previous claims comprising a heatsink attached to the oil sump of the engine.

21. A generator according to claim 20 in which the heatsink comprises: an engagement part adapted for liquid tight engagement with the oil sump; heat dissipation means and heat conducting means, said heat conducting means being in contact with the oil and in thermal communication with the heat dissipation means.

22. A generator according to claim 21 in which the heatsink functions as a dipstick.