"ENGINE HOUSING COMPRISING AN ADSORPTION ELEMENT"

FIELD OF THE INVENTION

The invention relates generally to a machine including a sorption element and an atmosphere dosing fluid, both within a sealed interior of the machine.

BACKGROUND TO THE INVENTION

Hermetically sealed machines, such as those found in micro combined heat and power (microCHP) units, often experience outgassing of unwanted hydrocarbons, other chemical species, and/or moisture, from components within die unit into the interior of the unit or machine casing at die high temperatures of operation. This can cause carburisation (carbon deposit and build up on) and/or oxidisation (corrosion) of the internal components, such as metal heat exchangers, of die machine. This can lead to power loss in die machine or complete failure of the machine.

It is an ob)ect of the present invention to provide an improved engine or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

In a first aspect the invention broadly consists in a machine including a sorption element widiin a sealed interior of die machine. The sorption element acts to remove unwanted hydrocarbons or other unwanted chemical species from gas circulating within the interior of die machine.

Typically die machine is a closed cycle machine such as a Stirling or Brayton machine for example. The machine may be an external combustion engine such as a Stirling cycle engine, for example. The machine may be a Stirling cycle refrigeration compressor, for example.

In one particular form of dns first aspect, the invention comprises a Stirling machine including: an engine block having at least one cylinder and piston; a mechanism for converting reciprocating movement of the piston to a rotary output or vice versa, and a sorption element within die interior of the machine.

In one form the sorption element is contained within a hermetically sealed interior of the machine In another form the sorption element is external to the machine but is connected to the hermetically sealed interior of the machine via a hermetically sealed gas flow path.

The sorption element acts to remove unwanted hydrocarbons or other unwanted chemical species from gas circulating within the interior of the machine. These species may evolve from greases, lubricants, retaining compounds, sealants, contaminants, residual cutting fluids or other compounds, within the hermetically sealed interior of the machine. Water can also be attached to or adsorbed into materials which can later be liberated into the gas.

In a preferred form the sorption material is a zeolite or other molecular sieve, or activated carbon, or a combination.

In a second aspect the invention broadly consists in a machine including a sealed interior comprising: a sorption element provided within the sealed interior and arranged to remove unwanted hydrocarbons or other unwanted chemical species in gas circulating within the interior of the machine; and an atmosphere dosing fluid introduced into the sealed interior to react with unwanted hydrocarbons or other unwanted chemical species from gas circulating within the interior of the machine

Typically the machine is a closed cycle machine such as a Stirling or Brayton machine for example The machine may be an external combustion engine such as a Stirling cycle engine, for example The machine may be a Stirling cycle compressor, for example

In one particular form of this second aspect, the invention comprises a Stirling machine including an engine block having at least one cylinder and piston; a transmission for converting reciprocating movement of the piston to a rotary output or vice versa; a sorption element within the interior of the machine; and an atmosphere dosing fluid introduced into the sealed interior of the machine.

In one form the sorption element and atmosphere dosing fluid are contained within a hermetically sealed interior of the machine. In a second form, the sorption element is external to the machine

- J — but is connected to the hermetically sealed interior of the machine via a hermetically sealed gas flow path. In this second form, the atmosphere dosing fluid can flow between the hermetically sealed interior and the hermetically sealed sorption container via the gas flow path.

The sorption element acts to remove unwanted hydrocarbons or other unwanted chemical species from gas circulating within the interior of the machine, such as from greases, lubricants, retaining compounds, sealants, cutting fluids, cleaning fluids, adhesives, resins, elastomers or other plastics materials or contaminants or other compounds, within the hermetically sealed interior of the machine.

Where the unwanted gas cannot be adsorbed (e.g methane or hydrogen) it may be reacted widi the dosing fluid e g. oxygen to create a compound that can be adsorbed (e.g. water).

The atmosphere dosing fluid reacts with unwanted hydrocarbons or odier unwanted chemical species from gas circulating within the interior of the machines Such hydrocarbons or chemical species may emerge from greases, lubricants, retaining compounds, sealants, contaminants, or other compounds, widnn the hermetically sealed interior of the machine Typically, this reaction or combustion will have carbon dioxide and water as by-products Typicall) , the sorption element acts to remove diese by-products.

In a preferred form the sorption material is a zeolite or other molecular sieve, or activated carbon, or a hydrogen getter, or a combination.

In a preferred form, the atmosphere dosing fluid is a gaseous. More preferably, the dosing fluid is the gas Oxygen added to the working fluid of the machine (e g nitrogen, helium or argon or other inert gas).

In one form the machine also comprises an electrical generator The machine may be a co- generaαon machine also comprising means for extracting heat from the engine coolant and/or exhaust gases for supply to a thermal load. The sorption element removes unwanted gaseous species from the encapsulation material of electrical windings of the generator The atmosphere dosing fluid reacts with some of the unwanted gaseous species from the encapsulation material of electrical windings of the generator and produces byproducts which are retained by the sorption elements.

In a further aspect the invention comprises a method of reducing internal corrosion and/or carburisation in an electrical power and heat co-generation unit comprising a Stirling engine, an electrical generator driven by the engine, means for extracting heat from the engine coolant and/or exhaust gases for supply to a thermal load, which method comprises including a sorption element within a sealed interior of the unit or connected to the sealed interior of the unit via a hermetically sealed gas flow path, which is effective to remove from the interior of the machine hydrocarbons or other chemical species evolved into the interior of the machine from components or lubricants within the interior of the machine,and also comprises admitting into die sealed interior of the machine an atmosphere dosing fluid which is effective to react with such hydrocarbons or other chemical species to produce reaction products which can be removed by the sorption element.

The term "comprising" as used in this specification means "consisting at least in part of When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced b) the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

Tills invention ma) also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of die application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which.

Figure 1 is a partially cutaway view of a Stirling generation or co-generation unit of die invention, shown partially demounted, and

Figure 2 is a longitudinal sectional view through the machine of Fig 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates generally to a machine comprising a sorption element. The machine may also comprise an atmosphere dosing fluid in a sealed interior within the machine. The sorption element and atmosphere dosing fluid both assist with removal of unwanted hydrocarbons and other chemical species that can be introduced into the machine.

In the embodiment shown a Stirling engine of an electrical power generation unit or combined power and heat generation unit comprises an engine block and four coaxial cylinders 2 in which a working fluid is contained. Heater heads 3 extend from an upper side die block 1 into combustion chamber 4, each closing an upper end of a cylinder 2. Connecting rods 5, each connected to a piston 6 in a cylinder 2, pass dirough apertures 7 in a part of the engine block to die drive mechanism 8, which converts the reciprocating movement of the pistons to rotation of the output shaft 9, which drives electrical generator 10 The drive mechanism 8 may be a wobble-type crank, or swash plate drive mechanism, for example. The generator 10 is fixed by generator mount 11 to die engine block 1.

A pressure vessel 12 is fixed about its upper periphery to the engine block 1, and encloses and surrounds die drive mechanism 8 and the generator 10. The pressure vessel 12 hermetically seals the interior of the machine from the outside atmosphere.

The engine comprises a sorption element 15 widun the interior of the machine, and in the embodiment shown, in an annular or cylindrical form within the space around the generator 10, between die generator 10 and the interior of die pressure vessel 12. Also mounted at die end of the generator 10 on die output shaft 10 is a fan 16 which circulates the working fluid within the pressure vessel 4, generally along path indicated by bold arrows 17 in Figure 2, for cooling the drive mechanism 2. Flow from the fan 10 is deflected axially upward around the generator 3 by the concave inner surface at die lower end of the pressure vessel 12. The axial flow passes through the sorption element 15, is stopped by the transverse face 10, and the flow then extends radially inward and downward as indicated, through and about die components of the drive mechanism 8, before being drawn back dirough the generator 10 to the fan 16.

The sorption element may be in die form of a removable and replaceable cartridge of suitable dimensions and physical form, optionally contained within a holder fixed widun the interior of the machine. The cartridge may comprise the sorption material in particulate form, within a woven or

- G - non-woven porous envelope winch allows gas flow through the envelope. In a prefeired form the woven material is coated with a polymeric material such as PTFE so that the coated envelope material provides micron level filtration to contain dust from die sorption material

The sorption element may be replaced at intervals, at servicing of the machine, when for example the pressure vessel 12 is removed. The sorption element may in one embodiment also be replaceable through other component mounting apertures in die pressure vessel, without making removal of pressure vessel 12 necessary. Alternatively the sorption element may be provided within the interior of die machine for the operating life of die machine.

In another embodiment, one or more sorption element cartridges may also be mounted externally to the main housing widi connecting conduits enabling passage of the housing gas flow dirough the sorption element/s Preferably in diis embodiment, sealed interior and connecting conduits are hermetically sealed against the outside atmosphere, while still allowing gas flow between the sealed interior and die sorption elements.

The engine may further comprise or have had an atmosphere dosing fluid introduced into the working fluid in die pressure vessel 12. The atmosphere dosing fluid may be introduced into the pressure vessel 4 through a valve The atmosphere dosing fluid may be an ₎ suitable fluid but is preferably gaseous. More preferably, die atmosphere dosing fluid is or contains oxygen or air added to the machine working fluid (e.g. nitrogen helium or argon).

Common unwanted hydrocarbons and chemical species that can be found in a machine may include methane (CH ₄ ), ethylene (C ₂ H ₄ ), and hydrogen (H ₂ ). The preferred form atmosphere dosing fluid can react or combust with such elements as shown in equation 1 below

xCH, + yC ₂ H _i + ∑H ₂ + (2x + 3y + -)O ₂ + rN ₂ O (x + Iy)CO ₂ + (2x + 2y + ∑)H ₂ 0 + rN ₂ (1)

The resulting carbon dioxide (CO ₂ ) and water (H ₂ O) can then be absorbed or adsorbed by the sorption element.

The atmosphere dosing fluid moves with die working fluid. Fan 16 circulates the working fluid and die atmosphere dosing fluid within the pressure vessel 12, generally along path 17 for cooling the drive mechanism 8. Flow from die fan 16 is deflected axially upward around the generator 3 by

the concave inner surface at the lower end of the pressure vessel 4 The axial flow passes through the sorption element 41, is stopped by the trans\ erse face 10, and the flow then extends radially inward and downward on path 40, through and about the components of the drive mechanism 2, before being drawn back through the generator 3 to the fan 16 If connecting conduits are provided, flow from fan 16 may pass through these also.

The atmosphere dosing fluid may be topped up when required. Alternatively, the atmosphere dosing fluid may be provided within the interior of the machine for the operating life of the machine. If die sorption element is provided externally to the main housing widi connecting conduits, the atmosphere dosing fluid will flow through die conduits so as to come into contact with the sorption element.

As an example of the application of the adsorber the following real machine test data is supplied.

Test l

A new Stirling engine of a microCHP, filled with instrument grade nitrogen during manufacture as the working fluid and sealed, and then operated for approximately 1000 hours was found to internally accumulate gas species listed in Table 1 below in the column under "Without Adsorber".An identical engine containing an adsorber cartridge internally within the unit casing as described above, the adsorber cartridge comprising a combination of activated carbon and zeolite, was also operated for approximately 1000 hours The gas within the interior of the unit was also analysed for prescence of die same compounds and the results are given in Table 1 below in the column under "With Adsorber".

Table 1

It is apparent that accumulation of these compounds was eliminated or substantially reduced.

Test 2

Similar comparative tests were carried out for the presence of hydrogen in similar new engines with a similar adsorber cartridge as described in Test 1 in one and without in another, after operation for about 500 hours The results are given in Table 2 below.

Table 2

It is apparent that hydrogen accumulation was eliminated or substantially reduced.

Test 3

A similar new engine was heated and vacuumed and the sucked off gases passed through a liquid nitrogen cold trap.Approximately 5 grams of water was drawn off the internal components After operation of another similar new engine with an adsorber cartridge as described above in Test 1 fitted the engine was also heated and vacuumed and the sucked off gases passed through a liquid nitrogen cold trap Less dian one gram of water was extracted. This demonstrates the adsorber dries the interior of the machine.

Test 4

On adding oxygen to the machine of Test 3 without an adsorber water condensation and corrosion occurred on the machine interior Introducing an adsorber cartridge as described above in Test 1 to a similar machine and dosing the interior of the machine with oxygen resulted in the engine subsequendy showing no signs of condensation and corrosion.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of die invention as defined in die accompanying claims