GB2437064A

GB2437064A - Degas apparatus for the cooling system of an engine

Info

Publication number: GB2437064A
Application number: GB0607447A
Authority: GB
Inventors: Roy Clissold; John Moffat; Antonis Dris; Jon Edward Caine
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-04-13
Filing date: 2006-04-13
Publication date: 2007-10-17
Anticipated expiration: 2026-04-13
Also published as: GB2437064B; GB0607447D0

Abstract

A degas apparatus for the cooling system of an engine is disclosed comprising of a degas tank 14 having a housing 12 defining a degas chamber 13 having a tangentially arranged inlet 11, 15 towards an upper end of the degas chamber 13 and a tangentially arranged outlet 17 located towards a lower end of the degas chamber 13. The degas chamber 13 is a least partially conical in shape so that the diameter of the degas chamber adjacent the inlet 11 is greater than the diameter of the degas chamber adjacent to the outlet 17. In a preferred embodiment several smaller degas chambers D1, D2, D3, Dn are connected together to form the degas apparatus. The chambers may be connected in gradually decreasing size in series or may be arranged in parallel. Each degas chamber may include conical portions of differing angle.

Description

A Degas Apparatus for the Cooling System of an Engine This invention

relates to liquid cooling systems for internal combustion systems used in motor vehicles and in particular to the removal of entrained gas from the coolant used in such a cooling system.

It is well known to use a degas bottle or tank in a cooling system for an engine. As is well known the degas tank fulfils several important roles. Firstly, it serves to compensate for volume changes resulting from the temperature change of the coolant as it is heated from ambient temperature to its normal operating temperature. Secondly, it removes and stores the air or gas entrained in the coolant and thirdly, it reduces the risk of cavitation in the coolant pump used to pump coolant around the cooling system.

In order to fulfil these roles the degas bottle is positioned above the highest position of the main cooling circuit of the cooling system and is connected in parallel to the main cooling circuit so that the highest point of the cooling system is connected to the inlet to the degas bottle while the outlet from the degas bottle is connected to a position in the main cooling circuit upstream from the coolant pump.

In practice, to ensure effective gas extraction, the coolant volume in the degas bottle needs to be between 15 and 20 % of the total coolant volume for the cooling system which is about 1 litre for an average passenger vehicle.

The volume of coolant stored in the degas bottle has an adverse effect on coolant and engine warm-up from a cold start and is desirable to minimise the volume of coolant stored in the degas bottle. This is because engine friction losses are greatest during warm-up when the engine and hence its lubricant are cold and, therefore, a large coolant volume in the degas bottle will have an adverse effect on friction losses and engine fuel consumption. In addition, the volume of the coolant stored in the degas bottle reduces cabin heating performance during warm-up. For these reasons, some cooling systems use a degas valve to isolate the coolant volume in the degas bottle from the main cooling system until a threshold coolant temperature is reached.

There are however some issues with regard to the use of a degas valve. Firstly, when the degas valve is closed and the degas bottle is isolated, the cooling system loses its ability to degas. Secondly, the inclusion of a degas valve increases the cost of the system and finally, for a degas circuit layout with a degas valve on the return hose, closing the valve at high pump speeds can cause cavitations at the pump.

It is therefore desirable to reduce the volume of coolant stored in the degas bottle and to this end it has been proposed in, for example, French Patent Publication Number 2,317,489 to use a cyclone type device to remove entrained gas from the coolant as such a device is more efficient at removing the gas and so a smaller coolant volume can be stored in the degas bottle without affecting degas performance. However, such a cyclone degas device has the disadvantage that the vertical height of the unit is relatively large and this can make packaging within the restraints of a motor vehicle difficult.

It is an object of this invention to provide a degas apparatus for removing entrained gas from the coolant of an engine cooling system that is of compact dimensions and requires the storage of a small volume of coolant.

According to a first aspect of the invention there is provided a degas apparatus for removing entrained gas from coolant used in a cooling system of an engine comprising a housing defining at least one degas chamber, the or each degas chamber having an inlet arranged tangentially to the degas chamber at an upper end of the degas chamber and an outlet arranged tangentially to the degas chamber near to a lower end of the degas chamber so as to produce in use a cyclone in the degas chamber wherein at least a portion of the or each degas chamber is of a conical form such that the diameter of each degas chamber near its respective inlet is larger than the diameter of the degas chamber near its respective outlet.

The whole of the or each degas chamber may be of a conical form.

The or each degas chamber may have an upper conical portion and a lower conical portion and the include angle of the upper conical portion may be larger than the included angle of the lower conical portion.

The or each degas chamber may have an upper conical portion and a lower cylindrical portion.

The apparatus may comprise of a number of degas chambers connected together between a common inlet and a common outlet.

The degas chambers may be connected together in parallel between the common inlet and the common outlet.

The degas chambers may be connected together in series between the common inlet and the common outlet.

The size of the degas chambers may reduce from the common inlet to the common outlet such that the largest degas chamber is the one having an inlet connected directly to the common inlet and the smallest degas chamber is the one having an outlet connected to the common outlet.

There may be a number of groups of degas chambers connected in parallel, each group of degas chambers comprising of two or more degas chambers connected in series.

All of the degas chambers may be formed as an integral part of a single housing.

lO The inlets and outlets for the degas chambers may be formed as an integral part of the single housing.

According to a second aspect of the invention there is provided a cooling system for an engine comprising a pump to circulate coolant through the system, a radiator to cool the coolant flowing through the system and a degas apparatus to remove entrained gas from the coolant, the degas apparatus comprising of a number of degas chambers connected together between a common inlet and a common outlet wherein, during use, the coolant enters each of the degas chambers tangentially so as to generate a cyclone in the chamber used to promote the release of the entrained gas from the coolant.

The coolant may leave each of the degas chambers tangentially.

The degas chambers may be connected together in series between the common inlet and the common outlet and the size of the degas chambers reduces from the common inlet to the common outlet such that the largest degas chamber is the one having an inlet connected directly to the common inlet and the smallest degas chamber is the one having an outlet connected to the common outlet.

Preferably, all of the degas chambers may be formed as an integral part of a single housing.

The inlets and outlets for the degas chambers may be formed as an integral part of the single housing.

Each degas chamber may be of a conical form.

Each degas chamber may have an upper conical portion and a lower conical portion and the include angle of the upper conical portion may be smaller than the included angle of the lower conical portion.

Each degas chamber may have an upper conical portion and a lower cylindrical portion.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.l is a schematic diagram of an engine and cooling system having a degas apparatus according to the invention; Fig.2 is a cross-section through a first embodiment of the degas apparatus shown in Fig.l; Fig.2a is a cross-section through the degas apparatus shown in Fig.2 showing the formation of a curved upper coolant surface "S" in the degas apparatus during use; Fig.3 is a plan view of the degas apparatus shown in Fig.2; Fig.4 is a side view of a degas apparatus according to a second embodiment of the invention; Fig.5 is a side view of a degas apparatus according to a third embodiment of the invention; Fig.6 is a schematic diagram of a degas apparatus a5 according to a fourth embodiment of the invention; Fig.7 is a schematic diagram of a degas apparatus according to a fifth embodiment of the invention; Fig.8 is a schematic diagram showing the connection of a number of degas chambers in parallel; Fig.9 is a schematic diagram showing the connection of a number of degas chambers in series; and Fig.lO is an exploded view of a degas apparatus according to a sixth embodiment of the invention.

With reference to Fig.l there is shown an internal combustion engine 1 having a liquid cooling system 10 comprising a cooling circuit and a degas circuit.

The cooling circuit comprises a radiator 2 to exchange heat with air flowing therethrough so as to reduce the temperature of the coolant, a coolant pump 3 to circulate the coolant through the radiator 2 and engine 1, a supply pipe 5 connecting the engine 1 to the radiator 2 and a return pipe 6 to return cooled coolant to the engine 1.

In practice the cooling system also includes a thermostat (not shown), a radiator bypass line (not shown) and a compartment heater circuit (not shown) these have been omitted as they are not directly relevant to this invention.

The degas circuit comprises of a degas apparatus in the form of a degas unit 4, a degas supply pipe 7 to connect the degas unit 4 to the highest point of the cooling circuit, a degas return pipe 8 connected to a position upstream from the coolant pump 3 to return coolant from the degas unit to the cooling circuit and a pressure cap 9 to prevent the pressure in the degas unit 4 from exceeding a predetermined pressure. It is important to have a head of gas/air above the coolant, which can compress during coolant expansion.

When the pressure setting for the pressure relief cap 9 is exceeded, this head of gas ensures that only gas is expelled from the system.

The degas unit 4 has a partially conical degas chamber (not shown) and the degas supply pipe 7 is connected to an inlet (not shown) to the degas chamber such that any coolant entering the degas chamber does so tangentially. This is in order to promote a cyclone or circulating flow in the degas chamber. The degas return pipe 8 is connected to an outlet (not shown) from the degas chamber which is also arranged tangentially to the degas chamber.

In use coolant from the engine 1 flows through the degas supply pipe 7 to the degas apparatus 4 where it generates a strong cyclone used to separate entrained gas from the coolant. The coolant then flows from the degas apparatus 4 through the degas return pipe 8 to the main cooling circuit at a position upstream from the coolant pump 3.

Because of the strong cyclone produced in the degas apparatus less coolant is required to be stored in the degas apparatus compared to a conventional degas bottle and so the degas unit 4 is smaller than a conventional degas bottle.

Referring now to Figs.2, 2a and 3 a first embodiment of degas apparatus is shown in greater detail. The degas apparatus in the form of a degas unit 14 has a body 12 defining a degas chamber 13 to which is connected an inlet 11 and an outlet 17. A pressure cap 9 is fitted to the top of the degas unit 14 to prevent the pressure in the degas unit 14 from exceeding a predetermined pressure which in this case is approximately 1 bar above atmospheric pressure.

The inlet 11 is connected in use to the degas supply pipe 7 shown on Fig.1 and the outlet 17 is connected in use to the degas return pipe 8 shown on Fig.1.

The inlet 11 has a port 15 in a side wall of the body 12 defining the degas chamber 13 arranged such that any coolant entering the degas chamber 13 does so tangentially.

It will be appreciated that it would be possible to have more than one coolant inlet.

The outlet 17 has a port (not shown) in the side wall of the body 12 defining the degas chamber 13 arranged such that any coolant leaving the degas chamber 13 does so tangentially so as not to reduce the velocity of the coolant leaving the degas chamber 13. This is important as any stalling of the coolant flow as it leaves the degas chamber will tend to weaken the cyclone produced in the degas chamber and thereby reduce the effectiveness of the degas unit 14.

As can be seen with particular reference to Fig.2a the cyclone produced in the degas chamber 13 in use by the introduction of the coolant forms an inverted conical liquid surface "s" above which any extracted gas "G" collects and below which is a rotating mass of coolant "C". It will be appreciated that the port 15 is at all times below the level of the coolant in the degas chamber 13.

Upon tangential entry, a main stream of coolant will travel in a downward spiral path along the wall of the degas chamber thus forming an outer vortex. Due to the centripetal acceleration associated with the vertical motion of the main stream, gas bubbles trapped in the coolant will be acted upon by a strong radial buoyancy force, and thus will move into a low-pressure core of the cyclone. A central core of gas will develop within a portion of the cyclone core as gas from above is drawn into the core merging with gas bubbles in its vicinity and forms an inner vortex with the same rotational direction as the outer vortex but ascending rather than descending. At the outlet from the degas chamber 13 a substantially gas-free coolant is extracted from the outer vortex.

The centripetal acceleration of flow in the degas chamber 13 due to the cyclone produced therein induces a much greater radial buoyancy force on gas bubbles compared to the gravity induced buoyancy force in a conventional degas bottle. As a result it is possible to obtain effective gas extraction using a smaller coolant volume compared to the volume of coolant in a conventional degas bottle.

By using a degas chamber 13 in which the diameter of the degas chamber reduces as the coolant travels from the inlet to the outlet this centripetal acceleration is increased and so the effectiveness of the degas unit 14 is further improved.

-10 -Because a degas valve or flow restrictor is not needed, the degassing capability of the cooling system is not compromised during warm-up and there is no added risk of cavitation at the pump.

Although the degas unit 14 is shown as having a linear conical form that is to say one in which the rate of change of diameter per unit length is uniform the invention is not limited to such a linear conical shape and non-linear or curvilinear conical forms can also be used.

With reference to Fig.4 there is shown a second embodiment of degas apparatus in the form of a degas unit 24.

The degas unit 24 has a body 22 defining a degas chamber 23a, 23b to which is connected an inlet 21 and an outlet 27. A pressure cap 9 is fitted to the top of the degas unit 24 to prevent the pressure in the degas unit 24 from exceeding a predetermined pressure.

The inlet 21 is connected in use to the degas supply pipe 7 shown on Fig.1 and the outlet 27 is connected in use to the degas return pipe 8 shown on Fig.1.

The inlet 21 has a port (not shown) in a side wall of the body 22 defining the degas chamber 23a, 23b arranged such that any coolant entering the degas chamber 23a does so tangentially.

The outlet 27 has a port (not shown) in the side wall of the body 22 defining the degas chamber 23b arranged such that any coolant leaving the degas chamber 23b does so tangentially.

In this embodiment the degas chamber is formed by an upper conical degas chamber 23a and a lower cylindrical -11 -degas chamber 23b. By using a conical form for the upper degas chamber 23a a larger volume for the extracted gas is provided than would be the case for a degas unit of the same length using the diameter of the lower degas chamber 23b.

As before the introduction of coolant into the degas chamber 23a forms an inverted conical liquid surface above which any extracted gas collects and below which there is a rotating mass of coolant. A main stream of coolant travels in a downward spiral path along the wall of the degas chamber 23b forming an outer vortex. Due to the centripetal acceleration associated with the vertical motion of the main stream, gas bubbles trapped in the coolant will be acted upon by a strong radial buoyancy force and will move into a low-pressure core of the cyclone. A central core of gas will develop within a portion of the cyclone core as gas from above is drawn into the core merging with gas bubbles in its vicinity this core of gas migrates upwardly to sit above the level of the rotating mass of coolant. A substantially gas-free coolant therefore leaves the degas unit 24 via the outlet 27.

With reference to Fig.5 there is shown a third embodiment of degas apparatus in the form of a degas unit 34.

The degas unit 34 has a body 32 defining a degas chamber 33a, 33b to which is connected an inlet 31 and an outlet 37. A pressure cap 9 is fitted to the top of the degas unit 34 to prevent the pressure in the degas unit 34 from exceeding a predetermined pressure.

The inlet 31 is connected in use to the degas supply pipe 7 shown on Fig.l and the outlet 37 is connected in use to the degas return pipe 8 shown on Fig.1.

-12 -The inlet 31 has a port (not shown) in a side wall of the body 32 defining the degas chamber 33a arranged such that any coolant entering the degas chamber 33a does so tangentially.

The outlet 37 has a port (not shown) in the side wall of the body 22 defining the degas chamber 33b arranged such that any coolant leaving the degas chamber 33b does so tangentially.

In this embodiment the degas chamber is formed by an upper degas chamber 33a and a lower degas chamber 33b both of which are of a conical form. The included angle of the upper degas chamber 33a is larger than the included angle of the lower degas chamber 33b. By using a larger included angle for the upper degas chamber 33a a larger volume for the extracted gas is provided than would be the case for a degas unit of the same length using the included angle of the lower degas chamber 33b. The included angle of the lower degas chamber 33b is chosen to optimise gas extraction and so the use of a larger included angle would reduce the efficiency of the degas unit 34 in removing gas from the coolant.

As before the introduction of coolant into the degas chamber 33a forms an inverted conical liquid surface above which any extracted gas collects and below which there is a rotating mass of coolant. A main stream of coolant travels in a downward spiral path along the wall of the degas chamber 33b forming an outer vortex and, due to the centripetal acceleration associated with the vertical motion of the main stream, gas bubbles trapped in the coolant will be acted upon by a strong radial buoyancy force and move into a low-pressure core of the cyclone. A central core of gas will develop within a portion of the cyclone core as gas from above is drawn into the core merging with gas bubbles in its vicinity which migrate upwardly to sit above the -13 - level of the rotating mass of coolant. A substantially gas-free coolant therefore leaves the degas unit 34 via the outlet 37.

With reference to Fig.6 there is shown a fourth embodiment of the invention in which three degas chambers Dl to D3 are joined together to remove entrained gas from the coolant. As indicated by the dotted outline there may be "n" degas chambers and not just three.

Each of the degas chambers Dl, D2, D3 and Dn can be of a single conical form, two conical forms, a conical and a cylindrical form or a cylindrical form and each has a tangential inlet Ii, 12, 13 and In and a tangential outlet 01, 02, 03 and In.

The degas chambers Dl to Dn are formed in a common housing 44 which also defines a gas storage volume 41 located above the degas cylinders. A pressure cap 9 is provided to relieve pressure in the gas storage volume 41 when it exceeds a predetermined pressure level. As before there is always a head of gas above the coolant to ensure that only gas is expelled via the pressure cap 9 if the pressure exceeds the pressure setting of the pressure cap 9.

Each of the degas cylinders is smaller than the single degas cylinder used in the first, second and third embodiments. This enables the height of the degas apparatus to be made smaller without affecting the efficiency of gas removal.

The use of a multi-chamber apparatus to induce multiple vortexes in the coolant for the extraction of gas bubbles from the engine cooling system permits the overall package size of the degas apparatus to be reduced for the same volume of coolant. Multiple degas chambers also allow the vessel to be of a more irregular shape and the degas -14 -chambers could be arranged on different levels within the degas apparatus which would overcome issues relating to the effects on the operation of the apparatus when the vehicle to which the apparatus is fitted is on an incline.

As shown in Fig.8 the separate degas chambers Dl to Dn can be connected in parallel between a common inlet and a common outlet or, as shown in F'ig.9, the separate degas chambers Dl to Dn can be connected in series between a common inlet and a common outlet.

With reference to Fig.7 there is shown a fifth embodiment of the invention which is similar to that shown in Fig.6 in that three degas chambers Dl to D3 are joined together to remove entrained gas from the coolant. As before, and as indicated by the dotted outline, there may be "n" degas chambers and not just three.

Each of the degas chambers Dl to Dn can be of a single conical form, two conical forms, a conical and a cylindrical form or a cylindrical form and each has a tangential inlet Ii, 12, 13 and In and a tangential outlet 01, 02, 03 and In.

The degas cylinders Dl to On are formed in a common housing 54 which also defines a gas storage volume 51 located above the degas chamber Dl to Dn. A pressure cap 9 is provided to relieve pressure in the gas storage volume 51 when it exceeds a predetermined level. As before there is always a head of gas above the coolant to ensure that only gas is expelled via the pressure cap 9 if the pressure exceeds the pressure setting of the pressure cap 9.

Each of the degas cylinders Dl to Dn is, as before, smaller than the single degas cylinder used in the first, second and third embodiments. This enables the height of the degas apparatus to be made smaller without affecting the efficiency of gas removal.

-15 -The primary difference between the multi chamber degas apparatus shown in Fig.7 and that shown in Fig.6 is that in the embodiment shown in Fig.7 the degas chambers Dl to Dn are not the same size whereas in the embodiment shown in Fig.6 all of the degas chambers Dl to Dn are the same size.

As before and as shown in Fig.8, the separate degas chambers Dl to On could be connected in parallel between a common inlet and a common outlet or, as shown in Fig.9, the separate degas chambers Dl to Dn can be connected in series between a common inlet and a common outlet.

However, in the embodiment shown in Fig.7 the arrangement of the degas chambers Dl to On is optimised to permit the degas chambers Dl to On to be connected in series. With this arrangement the size of each degas chamber decreases from a common inlet to a common outlet such that the largest degas chamber Dl is the one having an inlet Ii connected directly to the common inlet and the smallest degas chamber On is the one having an outlet On connected to the common outlet.

The reason for this arrangement is that there is a pressure drop across each degas chamber and so by using increasingly smaller degas chambers a strong degassing performance can be maintained even though the inlet pressure is reducing at the inlet to each subsequent degas chamber.

With reference to Fig.1O there is shown a degas apparatus 100 according to a sixth embodiment of the invention. The degas apparatus 100 has a moulded plastic housing 102 defining in this case six degas chambers 104a, 104b, 104c; 105a, 105b, and 105c. A cover 101 is fastened to the top of the housing 102 and defines therein a volume in which extracted gas is stored above the level of the coolant in the degas chambers 104a, 104b, 104c; 105a, 105b, -16 -and lO5c. A pressure cap 9 is provide to relieve the pressure of the gas stored in the cover 101 when it exceeds a predetermined level.

The degas chambers 104a, 104b, 104c; 105a, 105b, and 105c are arranged in two groups of three, there being a first group of degas chambers 104a, 104b and 104c connected together in series between a common inlet 111 and a common outlet 112 and a second group of degas chambers 105a, 105b and 105c connected together in series between the common inlet 111 and the common outlet 112. The first group of degas chambers 104a, 104b and 104c is connected in parallel to the second group of degas chambers 105a, 105b and 105c between the common inlet 111 and the common outlet 112.

Separate inlet passages (not shown) and outlet passages (not shown) between the various degas chambers 104a, 104b, 104c, 105a, 105b and 105c are formed as an integral part of the housing 102 50 that no external connections are required apart from the connections required to connect the common inlet 111 and the common outlet 112 to the cooling circuit of the engine 1. That is to say, the only external connections are the degas supply pipe 7 shown on Fig.1 and the degas return pipe 8 shown on Fig.1.

The height of the degas apparatus 100 is considerably less than would be the case for a conventional gravity degas bottle or single cyclone degas apparatus but provides the same or better gas extraction performance.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention.

Claims

-17 -Claims 1. A degas apparatus for removing entrained gas from

coolant used in a cooling system of an engine comprising a housing defining at least one degas chamber, the or each degas chamber having an inlet arranged tangentially to the degas chamber at an upper end of the degas chamber and an outlet arranged tangentially to the degas chamber near to a lower end of the degas chamber so as to produce in use a io cyclone in the degas chamber wherein at least a portion of the or each degas chamber is of a conical form such that the diameter of each degas chamber near its respective inlet is larger than the diameter of the degas chamber near its respective outlet.

2. An apparatus as claimed in claim 1 wherein the whole of the or each degas chamber is of a conical form.

3. An apparatus as claimed in claim 2 wherein the or each degas chamber has an upper conical portion and a lower conical portion and the include angle of the upper conical portion is larger than the included angle of the lower conical portion.

4. An apparatus as claimed in claim 1 wherein the or each degas chamber has an upper conical portion and a lower cylindrical portion.

5. An apparatus as claimed in any of claims 1 to 4 wherein the apparatus comprises of a number of degas chambers connected together between a common inlet and a common outlet.

6. An apparatus as claimed in claim 5 wherein the degas chambers are connected together in parallel between the common inlet and the common outlet.

-18 - 7. An apparatus as claimed in claim 5 wherein the degas chambers are connected together in series between the common inlet and the common outlet.

8. An apparatus as claimed in claim 7 wherein the size of the degas chambers reduces from the common inlet to the common outlet such that the largest degas chamber is the one having an inlet connected directly to the common inlet and the smallest degas chamber is the one having an outlet io connected to the common outlet.

9. An apparatus as claimed in claim 5 wherein there is a number of groups of degas chambers connected in parallel, each group of degas chambers comprising of two or more degas chambers connected in series.

10. An apparatus as claimed in any of claims 5 to 9 wherein all of the degas chambers are formed as an integral part of a single housing.

11. An apparatus as claimed in claim 10 wherein the inlets and outlets for the degas chambers are formed as an integral part of the single housing.

12. A cooling system for an engine comprising a pump to circulate coolant through the system, a radiator to cool the coolant flowing through the system and a degas apparatus to remove entrained gas from the coolant, the degas apparatus comprising of a number of degas chambers connected together between a common inlet and a common outlet wherein, during use, the coolant enters each of the degas chambers tangentially so as to generate a cyclone in the chamber used to promote the release of the entrained gas from the coolant.

13. A degas apparatus substantially as described herein with reference to the accompanying drawing.

-19 - 14. A cooling system for an engine substantially as described herein with reference to the accompanying drawing.