WO2009059364A1

WO2009059364A1 - Energy output

Info

Publication number: WO2009059364A1
Application number: PCT/AU2008/001644
Authority: WO
Inventors: Roger Philip Davies; Brett David Lloyd Turner
Original assignee: Intex Holdings Pty Ltd
Priority date: 2007-11-07
Filing date: 2008-11-07
Publication date: 2009-05-14

Abstract

A method of extracting more energy from a stream of gas possibly from an exhaust of an internal combustion engine with constrained back pressure resulting at its inlet where the gas stream will be directed Into a turbine there being a passageway through which the gas stream is directed having an expanded portion in the vicinity of which an additional fluid such as water is injected into the stream to be expanded therein.

Description

ENERGY OUTPUT

This invention relates to a method and apparatus for assisting in deriving energy from a source.

BACKGROUND ART

It is known to locate a turbine within or connected to an exhaust gases passageway of an internal combustion engine to achieve a drive of the turbine from the passage of exhaust and then use such derived energy as an additional energy source.

With current proposals the amount of energy that can be additionally gained using such a technique is relatively small as a proportion of energy that may exist in the form of heat, pressure and/or kinetic energy of the gas stream. There can be several possibilities for this limitation of energy extraction including a limit to an extent of back pressure that can be tolerated by a source supplying the gases and also the matching of gas density or perhaps more specifically the kinetic energy are not most appropriately matched for an energy extraction device.

DISCLOSURE OF THE INVENTION

This invention is directed to both a method and apparatus where in one instance there can be achieved an improvement in energy recoverable from such a positioned turbine.

In one form then the invention can be said to reside in a method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway which includes the steps of introducing an additional fluid upstream of a turbine where the fluid and the arrangement of introducing this is such as to increase density so as to increase the kinetic energy of gases upstream from an inlet into the turbine while constraining back pressure. The turbine itself can be used to drive or supply energy to other devices for instance effecting a compression of an inlet gas to the engine, effecting a direct drive to a drive train of a vehicle, or storing energy for instance using a generator or for any other energy useful purpose.

My proposal, and on the results of my experiments thus far, these show that it can be successful, is to introduce an additional fluid such as water upstream of such a turbine where the fluid and the arrangement of introducing this is such as to increase its specific heat capacity which if temperature and pressures are standardized would result in a higher density measurement and provide that there is increase if the stream is reconverged providing a higher kinetic energy in a useful form for a turbine than might be available upstream from an inlet into the turbine while constraining back pressure.

This is achieved by introducing such additional fluid, whether in liquid or vapour form or a mixture of both, in the vicinity of a portion of passageway through which the gases pass which is shaped so that it will have an increase or expansion of cross sectional area as it progresses downstream. In preference, said additional fluid such as water is introduced as a liquid into an upstream portion of the exhaust passageway where there is a transition from a portion of the exhaust passageway of a first cross sectional area to a portion of larger cross sectional area and where there is sufficient heat to vaporise liquid in the fluid.

In preference there is also a subsequent reduction in cross sectional area to assist in increasing effective velocity of the gas for introduction into a turbine.

If the fluid is liquid water, this is introduced in an appropriate quantity over time which can be judged by advantageous performance output of the turbine in the circumstances, and in preference, subsequent to the turbine, there can be a means to recover the fluid by for instance condensation. The introduction of a material such as water will implicitly increase the specific heat capacity of the combined fluid which can result in an increase of density if considered at standard temperature and pressures but if the gas is being expanded the increase in density is then to be interpreted with respect to standard temperature and pressures because if the fluid is being introduced into an expanding chamber area then there is a natural reduction in density for this reason. The addition of a higher molecular weight material then which mixes with the gas will then result in this density increase o more specifically this specific heat capacity.

The results in experiments thus far have indicated that at least in the examples I have tried, the performance available from a turbine in these circumstances is improved by such introduction of fluid upstream of the turbine.

The reason for this advantage would appear to result from the fluid once introduced into an exhaust chamber in which there is a transition from smaller to larger area being subject to rapid expansion by reason of the additional heating including evaporation by reason of the residual heat of the exhaust gases and additional heat of the surrounding casing such that this then vaporises the fluid and incidentally appears to increase the density and thus the kinetic inertia potential of the gas stream significantly but also by having the transition shape assist in directing the rapidly expanding gases predominantly downstream.

In one form of this invention it can be said to reside in a method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway where the passageway has an outlet for the gas, the method comprising or including directing the stream of gas into the passageway at an inlet end, the passageway having a portion along its length having a cross sectional area which is of larger magnitude from an upstream to downstream location and including a step of introducing fluid into the stream of gas in the vicinity of this said portion. In a further form of the invention then this can be said to reside in a method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway where the passageway has an outlet for the gas to be directed to effect a drive of a turbine, the method comprising or including directing the stream of gas into the passageway at an inlet end, the passageway having a portion along its length having a progressively increasing cross sectional area and including a step of introducing fluid into the stream of gas in the vicinity of this said portion.

If the shape of the portion of increasing cross section is of frusto-conical shape, then this effect even better supports downstream movement of the gases without unduly increasing back pressure to further incoming gases coming into the transition area.

In preference the divergence angle of part or all of the internal surfaces of such a frusto-conical shape is found to be approximately 7 degrees in relation to the direction of flow of the adjacent gas stream thus far but this can be widely changed and still obtain advantage. As an example but again only in preference a divergence angle of between degrees up to 15 degrees may be a preferred range. As an example but again only in preference the divergence angle of the containing surfaces may increase by approximately 7 degrees over each unit length of the diverging portion of the passageway where such unit length can be within the range of from 2 to 3 cms and in preference approximately 2.5 cms.

Nonetheless, there is therefore additional energy to be achieved by conversion of some of the heat energy within the exhaust gases to increase specific heat capacity which provides potentially more capacity for kinetic energy and therefore the dynamic pressure by reason of the expanding fluid for instance vaporising water and expanding any introduced or resultant gas and this is found to effect a more efficient action and provides the improved extraction potential. It does not appear at this stage that there is any limitation to the nature of the combustion engine provided there are hot gases emitted from the engine however, each engine may have specific characteristics which may mean that each passageway dimensions and inlet or inlets locations would be preferably selected to best fit the engine.

Accordingly, the advantage would appear to be available to a large variety of different engine types and even to alternate suppliers and sources of hot gases.

One characteristic of some engine types is that they have exhaust valves and if back pressure is above a normal level this can cause a reduced flow of gases past the exhaust valves and possible undue heating and possible burnout of these.

I have found that there is advantage not only in introducing the additional fluid simply between the ignition chamber and a turbine in a transition area within the exhaust passageway, but that additional fluid can be introduced at an inlet side of an engine where the result is to modify a flame front of an ignition process but also to, maintain generally a cooler ignition result and cooler conditions regarding exhaust valves. There are numerous previous examples and known art regarding the preliminary spraying or supplying water mist which can be used in conjunction with the current concept.

In trials conducted so far, such introductory input of fluid as an additional fluid, e.g. water can be also be of value to a modest extent for the reasons explained but which also in turn increases the density or specific heat capacity of the exhaust gases and again assists the efficiency of production of power from a turbine.

In preference, there is recovery of fluid subsequent to the turbine and in a preferred case, this is by condensation of the expelled steam. This has the advantage that the liquid can then be reused. It will conventionally be filtered and in so far that it has been closely mixed with, in a preferred case, exhaust gases, materials that would be otherwise discharged into the atmosphere can be expected to be captured by the fluid and then be available to be separated.

In relation to the additional fluid, it is expected that this would be introduced as a liquid or vapour or mixture of both and in preference in a manner that contributes to rapid evaporation as a fine spray of droplets.

There will be a time delay from introduction of a liquid or vaporised liquid as additional fluid to when it is encountering the turbine, and in practice, there will be provided an appropriate length of passageway compatible with the quantity of additional fluid that is expected to be introduced and the manner in which this is broken up into finer particles, e.g. as a spray to assist in the rapidity of the vaporization.

The exhaust passageway subsequent to the transition location in a first instance can be reduced in cross sectional area prior to introduction into a turbine. This in practise does not appear to then unduly further increase backpressure.

The invention applies to both an apparatus and to method and an output the result of the method.

BRIEF DESCRIPTION OF THE INVENTION

For a better understanding of this invention it will now be described in relation to embodiments which shall be described with the assistance of drawings wherein

FIG 1 illustrates in a schematic way an embodiment which includes an internal combustion engine, an exhaust with a transition location, a turbine within the exhaust passageway, means to inject additional fluid both subsequent to exhaust valves and prior to a turbine, an arrangement for condensing fluid subsequent to the turbine, and in addition an arrangement for introducing additional fluid into an inlet of the internal combustion engine, and

FIG 2 is a schematic drawing illustrating a connection arrangement from the turbine to the crankshaft of an internal combustion engine.

BEST MODE FOR CARRYING OUT THE INVENTION

The experiments thus far have been conducted on a set of equipment which shall be described in relation to specific commercial items that are available.

There has been discovered a principle which provides very significant additional accessible energy from a given fuel quantity being used by an internal combustion engine.

There can be a number of different types of internal combustion engine, as indeed there can be a number of different turbines to be positioned within an exhaust passageway and there can be various ways in which the energy derivable from the turbine can be used or directed to either direct advantage to say the drive train of a driven vehicle.

As such then our improvement relates to a modification to an exhaust passageway where the passageway has downstream a turbine arranged to be driven by the passage of exhaust gases therepast.

We propose the addition of a liquid which will be vaporised in the exhaust passageway upstream from the turbine in a location in the vicinity of a transition location. It is envisaged that water will be the fluid but it is envisaged that other liquids may be used in some circumstances. The use of this liquid has advantages in that it increases the density of the gases but there is also advantage from the transition shape which appears to provide increased kinetic β energy which then effects a better impulse against which is to say increased force applied to a turbine blade.

However, if the liquid or additional vapour or liquid vapour mix is simply injected into a cylindrical passageway then the increase in density or specific heat capacity may be expected to automatically increase significantly back pressure presented to an exhaust gas from an upstream source.

This can implicitly then limit the amount of liquid or gas that can be injected into the exhaust gas stream and may in practical situations raise the back pressure too much which may cause in a conventional four stroke internal combustion engine exhaust valves to overheat or otherwise malfunction. In experiments conducted so far it appears that the value therefore of adding a vaponsable liquid into an exhaust gas stream in this configuration is of minor advantage considering the complexities of the mechanical parts and any additional energy being gained.

However by having an enlarged area portion of the exhaust passageway with a progressive transition area from a smaller cross sectional area to a larger cross sectional area downstream and injecting a fluid such as vaporisable liquid into the gas stream in this area has the result that much more liquid can be injected than with a straight passageway before an unacceptable level of back pressure is reached at least for an internal combustion engine sensitive to back pressure. What this means then is that the quantity over time of liquid that can be injected can be in fact significantly increased and again from experiments so far this has provided a significant improvement in available energy achievable from a given arrangement.

The advantage of a transitional shape is that this is found to assist in minimising back pressure presented to any incoming exhaust gases which otherwise may be excessive if the liquid is introduced in an area without an enlarging transition. The reason for this effect is surmised at this stage as being a result of the rapidly expanding gas vaporised from the liquid physically being directed preferentially into a downstream direction by the shape of the internal transition area surface and the directed gas stream flows.

The effect does appear to be more effective if the change in area is significant eg 1O;1 and if the transition is relatively gradual or streamlined. A slope relative to a central axis parallel to the direction of flow of the gas stream of 7 degrees has been found to provide a good effect which is to say a throat angle of 14 degrees. The effect is also enhanced if the liquid is first heated but still kept as a liquid before spraying into the exhaust passageway although in another case having a gas liquid mix has been successful as in for instance as wet steam.

Advantage of the fluid addition is that this then is more effective and efficient in driving a turbine and this advantage can be enhanced by having the transition arrangement which allows for a greater volume of liquid being directed into the exhaust stream.

While a significant advantage of the arrangement is the fact that this provides for a reduced back pressure it is not intended that the applications for this should be so limited.

Some internal combustion engines which use spring loaded exhaust valves can be especially vulnerable where either the exhaust flow of gases is insufficient to maintain cooling of the valve or there can be an impediment to proper timing of the opening of the valve or failure of the valve to remain sealed as intended during some portion or portions of the combustion cycle-

However we have found that by using the arrangement described namely injecting fluid into or beyond the transition area that this also provides for increased downstream kinetic energy which is being derived from heat in the exhaust area. As such then it has the advantage of converting this additional heat energy to kinetic energy which is accessible for further use. I

Referring to the drawings then, there is an internal combustion engine 1 which has an exhaust manifold 2 directed into a segmented exhaust outlet 3 directed into an expansion chamber 4. Of advantage where there are even numbers of four or more cylinders and the engine is operating in a four stroke cycle the exhaust manifolds are combined so that each pressure peak from a respective cylinder in a pair of cylinders is timed to be 180 degrees out of phase where they enter the transition area. In an alternative embodiment each pair may feed separate expansion chambers.

This expansion chamber 4 commences with a frusto conical shape providing a transition area 5 from a smaller to larger cross sectional area (in this case 10 times the area) with the shape having a 7 degree diverging angle to a central axis of the circular cross sectional shape this angle being substantially constant (an alternative that is found to be also of advantage is to have a progressively increasing divergence which initially has a divergence of less than 7 degrees increasing in a streamlined which is to say a contoured diverging section by having a curved shape as an expanding alignment with respect to a central axis 6 commencing with a diverging curved surface whose tangent increases to 7 degrees over the first 2.54 cm and increases further by 7 degrees for each 2.54cm over the surface in the direction of flow of gas). A commencement area 7 and a finishing area 8 are each slightly rounded off to provide assistance to maintaining streamlined flow.

In this case there are three water spray heads 9,10 (and 1 1 not shown) each projecting slightly into the transition area 5 but toward the downstream end of an expanding or diverging portion of this. In another embodiment (not shown in the drawings) the spray heads are located further downstream at a commencement of the converging part and useful results in accord with the invention were also obtained. In this first embodiment however the exhaust gases are then directed into a narrower passageway with a converging transition shape 12 which is arranged to direct the gases onto turbine blades within the turbine 13. The transition from larger area to smaller area has a converging tapered frusto conical shape with a 20 degree taper for the device to function with exhaust gases being pushed in one direction towards the turbine 13. In this case the turbine is a bladed turbine of a type sold under a Trade Mark Garrett.

An output shaft from the turbine is directed through a reduction gear box which is not specifically shown, which then is connected by resilient toothed belts 15 and 16, which are then coupled to the crankshaft 17 of the motor 1.

The downstream side of the passageway after the turbine 13 includes a condenser 19. This condenser 19 includes an inlet 20 for supply of additional water, and an outlet 21 to atmosphere for residual gases.

The resultant liquid as condensed is then fed through conduit 22 and pumped by high pressure pump and contaminant filter 23 through conduit 24 for supply to both the inlet manifold inlet 25 and the exhaust gases input to the heat exchanger 26 each controlled by appropriate engine management system controllers at 27 and 28.

The fluid to be injected is first passed through heat exchange coil 26 which is wrapped around the first cylindrical and diverging transitional portion of the exhaust passageway downstream from the exhaust valve so that the water being directed there-through will be heated although not to the extent that it is entirely vaporised before being introduced into the exhaust passageway. It may be advantageous to maintain the pressure of this water supply above 1 bar to allow heating of the liquid to greater than the boiling point of 100 Celsius at sea level pressure in the case of water as the liquid.

Not shown but found to be of value, there is provided insulation around the entire exhaust passageway.

A Honda 6.5 Hp single cylinder carburetted engine was set up with a constant load requiring a 1.4 litre/hour fuel burn, corresponding to one cylinder from a 6 cylinder internal combustion engine burning 8.4 l/h. (typical fuel burn rate for a motor vehicle travelling at 100 kph.)

Water injection was initially injected at 60cc/minute without preheating, at 1000 psi via a 2 micron nozzle producing 10 micron droplets. Two prototypes were constructed with different expansion chambers, the first to simulate the effects of a near cylindrical exhaust manifold but with a sufficient variation in chamber diameter to cause some increase in the frictional losses produced by a varying lumen diameter and allow measurable differential pressures to be developed and measured in the various segments.

The second chamber design was intended to maximize conversion of exhaust gas thermal to kinetic energy and had design parameters as follows:- Inlet diameter 20mm Divergent angle 5 degrees Chamber diameter 65 mm Chamber length 135mm Downstream convergent angle 2.5 degrees on either side of the direction of gas flow with a total divergence of 5 degrees. Outlet diameter 22.5mm Overall length 1.02m.

Pre-heating of the injected liquid was incorporated. The actual temperature was monitored so that the temperature did not reach a boiling temperature prior to exit from the respective spray head. A nozzle with a 0.7mm orifice, operating at 145 psi, with a flow rate of up to 187.5cc/min reducing the chamber temperature to 205C was found to be of value in the tests.

All pressures that are static measurements are obtained with a water manometer, with the dynamic pressure pitot tube of the outflow calibrated against a known dynamic pressure anemometer.

The dynamic pressure (proportional to the cube of the velocity of the gas stream multiplied by the molar mass, or in the alternate, the velocity density product) of the gas stream was calibrated in m/s and measured 10mm beyond the tip of the tail pipe at the discharge end of the converging duct segment. (The kinetic energy of the gas stream is noted to increase with the cube of the dynamic pressure and proportional to the area of the outlet.) The dynamic pressure pitot tube at the outflow was calibrated against a known dynamic pressure anemometer.

With the 3.5:1 chamber design; there is a doubling of inlet pressure as liquid is injected up to the thermal capacity of the gas to produce complete vaporization. This results in an increase in back pressure on the exhaust valves of an internal combustion engine when this is used as the heat source. Injection of liquid into a straight cylindrical exhaust system produces an even more marked effect of increased back pressure.

1. It is apparent 2 from the increase in outlet pressure that vaporization is still occurring in the outlet tube indicating the gas velocity is so high that there may be insufficient time for vaporization within the length of the pressure chamber.

2. The inlet temperature 3 fall indicates that significant reversion of water droplets into the inlet of the 3.5:1 expansion chamber design is occurring producing a cooling effect at the inlet.

3. There is only a modest increase 4 in outlet dynamic pressure (115%) with a 3.5:1 expansion chamber.

4. With the 10:1 pressure chamber design, due to increased friction and thermal losses resulting from the longer length, the dynamic pressure 5 of the exhaust gas has fallen compared to the 3.5:1 pressure chamber design.

5. The fall in chamber temperature 6 without insulation indicates significant radiant thermal losses are occurring.

6. With liquid injection and conversion of thermal to kinetic energy, the chamber temperature 7 has fallen while dynamic pressure 7 has increased.

7. With insulation of the Pressure chamber the device temperature 8 increases but without an effect on overall dynamic pressure at the outlet 8. Adding liquid to the insulated device allows a further slight increase in dynamic pressure 9 due to increased thermal energy being available for vaporization of the working liquid.

9. Pre-heating of the working liquid allows an increase in the amount of liquid that can be injected by approximately three-fold ( from 60cc up to

187cc/min for the prototype). Reduced thermal losses and re-capture of radiated energy in the pipework of the working liquid allows injection of an increased volume of super-heated liquid into the pressure chamber. The fall in chamber temperature 10 reflects the increased conversion of thermal to kinetic energy.

10. Even though the temperature of the gas stream has fallen, the increased mass of the liquid and conversion of thermal to kinetic energy produces the highest dynamic pressure 11 achieved in the prototype. Chamber pressure is at its highest value, with some increase in inlet pressure also evident. An increase in the diameter of the pressure chamber is required to allow injection of this volume of liquid without an increase in upstream pressure.

11. The diameter of the pressure chamber is limited in practice by space available in a mobile application, and thermal losses as the surface area of the pressure chamber and gas acceleration segments increase.

The effect does not of itself remove any need where a multicylinder internal combustion engine is involved from having an allowance for cyclic changes in pressure arising and the passageway acting as a resonant chamber. The results are also reflected in full size prototype testing of a 4 litre passenger car (Ford Motors Australian design Falcon EB 1989) where tests indicated a significant increase of around 30% in horse power at the wheels during acceleration testing and also implicitly better fuel economy. Further tests were conducted using the exhaust gases of a Mazda RX7 2 rotor rotary engine as a heat source. A chamber design was constructed in accordance with the description contained herein above. Values were obtained during testing as follows:-

■ Static pressure as measured at the exhaust outlet of the motor during water injection:- 14mm water pressure,

• Static pressure as measured in the pressure chamber: +32mm water

• Static pressure as measured in the converging section : +12mm water

• Dynamic pressure at inlet to turbine +32mm water reflecting an 86% increase in the energy available as velocity or kinetic energy in the gas stream.

• Temperature in exhaust gas stream was reduced from 700 to 380 Celsius.

While backpressure reduction is especially of value in specific internal combustion engines it is believed that the results indicate value in other applications where there is not such a vulnerability. The recovery of energy from heat contained within exhaust gases is of major advantage if the costs of infrastructure do not over ride. By getting this additional level of recovery this has made the economics of recovery better.

Additional features used in cooperation with the above system includes for a conventional internal combustion engine, injection of water mist in an inlet manifold. This cools the resultant exhaust gases and allows therefore greater transfer of thermal energy to the exhaust gases and less to the radiator system. This then allows in some cases for a higher back pressure to be tolerated in so far that the cooling mist and modified burning characteristics implicitly effect a cooler exhaust gas and therefore cooler exhaust valves for a given output.

Further, the mechanical output of the internal combustion engine is directly enhanced by connecting the output from a turbine onto the output crankshaft of an engine. This in a mechanical sense uses a reduction gear box to reduce the output rotational speed to match this to be similar to the engine. Also there will be variations in momentary speeds and in order to tolerate these variations it has been found to be of value to use a shaft and pulley assembly where the pulleys are connected to each other by a flexible belt or belts and these connecting the gear box output with the engine crankshaft.

Throughout this specification the purpose has been to illustrate the invention and not to limit this.

Claims

1 A method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway which includes the steps of introducing an additional fluid upstream of a turbine where the fluid and the arrangement of introducing this includes an expanded cross sectional area into which the fluid is directed and is such thereby as to increase density of gases upstream from an inlet into the turbine while constraining back pressure.

2 A method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway where the passageway has an outlet for the gas, the method comprising or including directing the stream of gas into the passageway at an inlet end, the passageway having a portion along its length having a cross sectional area which is of increasing magnitude from an upstream to downstream location and including a step of introducing fluid into the stream of gas in the vicinity of this said portion.

3 A method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway where the passageway has an outlet for the gas, the method comprising or including directing the stream of gas into the passageway at an inlet end, the passageway having a portion along its length having a cross sectional area which is of increasing magnitude from an upstream to downstream location and there after of decreasing cross sectional area and includes a step of introducing fluid into the stream of gas in the vicinity of this said portion.

4 A method of assisting extraction of energy from a stream of gas directed to be flowing through a passageway where the passageway has an outlet for the gas to be directed to effect a drive of a turbine, the method comprising or including directing the stream of gas into the passageway at an inlet end, the passageway having a portion along its length having a progressively increasing cross sectional area and as well a portion of decreasing cross sectional area thereafter the method including a step of introducing fluid into the stream of gas in this said portion.

5 A method as in any one of preceding claims 1 through 4 where the outlet is connected to a turbine.

6 A method as in any one of the preceding claims 1 through 5 where the said portion of passageway is of at least approximately circular cross sectional shape along its length.

7 A method as in any one of claims 1 through 6 where the said portion has a progressively increasing cross sectional area with a degree of divergence which is within a range of from 1 degree to 15 degrees to a longitudinal directional of the passageway.

8 A method as in any one of claims 1 through 6 where a or the progressively increasing cross sectional area has a degree of divergence of approximately 7 degrees to an axis in a longitudinal directional of the passageway.

9 A method as in any one of claims 1 through 6 where the progressively increasing cross sectional area has a degree of divergence which increases along for a selected extent along the length of the said portion.

10 A method as in any one of the preceding claims where an incoming stream of gas being directed into the passageway is an exhaust gas being exhausted from an internal combustion engine.

1 1 A method as in any one of the preceding claims where the fluid is water. 12 A method as in any one of the preceding claims further comprising the step of preheating the liquid prior to its introduction into the said portion of the passageway.

13 A method as in any one of the preceding claims comprising a further step of effecting a condensing vapour within the gas stream.

14 A method as in preceding claim 13 comprising a further step of effecting - a filtering of condensate.

15 A method as in any one of the preceding claims including a step of effecting a condensing to liquid, vapour within the gas stream subsequent to its passage through a or the turbine, and then redirecting said liquid to be reinserted into the said portion of the passageway.

16 An arrangement for assisting in effecting extracting of energy from a stream of gas comprising a body defining a passageway for such stream of gas with an inlet and an outlet, the passageway having a portion along its length having a progressively increasing cross sectional area, a source of fluid and means to introduce at pressure said liquid into the said portion of the passageway.

17 An arrangement as in claim 16 where the said portion also includes a converging part downstream from the diverging part.

18 An arrangement as in claim 16 where the progressively increasing cross sectional area is of at least approximately circular cross sectional shape along its length.

19 An arrangement as in claim 16 where the progressively increasing cross sectional area has a degree of divergence which is within a range of from 4 degrees to 15 degrees to a longitudinal directional of the passageway. 20 An arrangement as in claim 15 where the progressively increasing cross sectional area has a degree of divergence which is approximately 7 degrees to an axis in a longitudinal directional of the passageway.

21 An arrangement as in claim 15 where the progressively increasing cross sectional area has a degree of divergence which is at first less than or equal to

7 degrees to a longitudinal directional of the passageway increasing to more than 7 degrees at some further location within the divergence.

22 An arrangement as in any one of the preceding claims 16 through 21 where the inlet to the passageway is connected to an exhaust outlet of an internal combustion engine.

23 An arrangement as in any one of the preceding claims 16 through 22 where the inlet to the passageway is connected to an exhaust outlet of an internal combustion engine and the outlet is connected to a turbine.

24 An arrangement as in claim 16 where the shape of the said portion of passageway, the source of fluid, the arrangement and location of the inlet for the fluid are such as to increase pressure of gases downstream as they exit from the outlet without an undue increase in back pressure being caused at the inlet of the passageway by reason of such additional fluid.

25 An arrangement as in claim 16 where there are means to preheat the fluid prior to its introduction into the said portion of the passageway.

26 An arrangement as in claim 16 where the supply of gas is from an internal combustion engine and there are means to direct some of the fluid into an inlet manifold of the engine.