WO2000053918A1

WO2000053918A1 - Compound power plant

Info

Publication number: WO2000053918A1
Application number: PCT/AU2000/000170
Authority: WO
Inventors: Spiro Ross Spiros
Original assignee: Hydrogen Technology Limited
Priority date: 1999-03-11
Filing date: 2000-03-10
Publication date: 2000-09-14
Also published as: AUPP912299A0

Abstract

The exhaust gases from an internal combustion engine (12) are provided to a turbo fan/alternator unit (20) and the electrical output therefrom passes a rectifier (22) to a battery storage unit (24). The stored electrical energy is controlled by a power controller (26) as it is provided to an electrolysis gas generator (16). The liberated admixed hydrogen and oxygen gases are provided to the engine (12) as a substitute for, or an additive to hydrocarbon fuel. The otherwise waste energy of exhaust gases is recovered, in part. Such a compound power plant can be utilised in a motor vehicle or a marine vessel.

Description

COMPOUND POWER PLANT

Field of the Invention

This invention relates to a compound power plant that utilises an internal combustion engine for the production of motive power. The power plant can be used in all forms of land vehicles, marine engines and stationary motor-driven generator sets.

Background of the Invention

Internal combustion engines utilise hydrocarbon fuels as a power source, the chemical energy of which is converted to motive power by the engine (as is well known) with varying degrees of efficiency. Common forms of hydrocarbon fuel are gasoline, liquid petroleum gas. dieseline, marine diesel oil and natural gas. All forms of internal combustion engine have the problem of the undesirable waste combustion products such as non-combusted hydrocarbon, carbon, oxides of sulphur and nitrogen, and (in some circumstances) heavy metals.

Considerable effort is being expended, particularly in the motor vehicle industry, in the reduction of pollutants and greenhouse gas emissions in response to environmental laws. Another area of research associated with internal combustion engines is the imperfect nature of energy conversion from the latent chemical energy of the fuel to energy that can be mechanically harnessed.

It is an object of the present invention to ameliorate one or more such disadvantages in the prior art.

Disclosure of the Invention

The invention discloses a compound power plant comprising: an internal combustion engine receiving a supply of hydrocarbon fuel; a gas generation electrolysis unit supplying admixed hydrogen and oxygen gases to be combusted with said hydrocarbon fuel by said internal combustion engine; and a turbo fan/alternator unit receiving the exhaust gases from said internal combustion engine and providing a DC power output therefrom coupled to the electrolysis unit.

Advantageously, a battery unit receives and stores the DC power and provides a source of stored DC power to a power controller that controls, by way of chopping, the supply of power to the electrolysis unit. Additionally, there is a battery charge detector sensing the charged state of the battery unit and providing a signal representative thereof to the power controller.

Preferably there is further a water reservoir providing a supply of water to the gas generator. There further can be a fuel tank for supply of fuel to the internal combustion engine.

The compound power plant can further include a wind generator providing a further supply of DC power to said battery unit.

Yet further, for a motor vehicle embodiment, rotational (kinetic) energy of the drive chain, including a tail shaft and axles, can be recovered by an electrical generator to provide a yet further supply of DC energy to the battery unit.

The invention further provides a motor vehicle or marine vessel having a compound power plant as described above, in which said internal combustion engine provides a source of motive power.

The invention further discloses a method for recovering waste energy from an internal combustion engine, the method comprising: converting volumetric flow of exhaust gases to electrical energy; utilising said stored electrical energy to electrolyse water to produce admixed hydrogen and oxygen gases; and utilising said admixed gases in the combustion process.

Preferably, the method comprises the further steps of storing the electrical energy and controlling the amount of stored electrical energy used for electrolysis in accordance with internal combustion engine demand. Brief Description of the Drawings

A number of preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of a compound power plant;

Figs. 2a and b show characteristics of the power controller of Fig. 1 ;

Fig. 3 is a schematic block diagram of a compound power plant of a second embodiment;

Fig. 4 shows a schematic block diagram of a compound power plant of a third embodiment; and

Fig. 5 shows the relative physical location of elements of the compound power plant in a motor vehicle.

Detailed Description and Best Mode

The compound power plant 10 shown at Fig. 1 has an internal combustion engine 12 that receives a supply of hydrocarbon fuel from a fuel tank 14. The engine provides motive force for a motor vehicle or marine vessel in which it is installed by a drive chain (not shown). The drive chain, in the embodiment of a motor vehicle, includes the tail shaft from the gear box or automatic transmission and the front and rear wheel axles, either or both of which axles may be driven by the tail shaft.

In addition to the hydrocarbon fuel from the fuel tank 14, the engine 12 also receives a supply of admixed hydrogen and oxygen gases (H₂ and O₂) provided by a gas generator 16, in the form of an electrolysis unit. A suitable form of electrolysis unit, having the characteristics of being lightweight, compact and efficient, is disclosed in commonly owned International Publication No. WO 95/07373 and US Patent No. 5,843.292. the contents of which are incorporated herein by way of cross-reference. The gas generator 16 receives a supply of water from a water reservoir 18. Of course, the supply of water could be from a town main supply, and in that sense, be relatively unlimited with respect to a single engine. The admixed hydrogen and oxygen gases supplied to the engine 12 are combusted in the engine as an alternative, or as a supplement to the hydrocarbon fuel. In the latter case, the admixed gases act as a catalyst for the hydrocarbon fuel, providing for more efficient combustion. The use of both admixed hydrogen and oxygen gases and hydrocarbon fuel results in a significant decrease in undesirable combustion products, including carbon.

For example, a 5% additive of hydrogen gas to a gasoline/air mix can reduce nitrous oxide emissions by 30-40%. Tests conducted by the inventor on a 3.3 litre internal combustion engine, where 28 litre/min of admixed gas is mixed with 4,000 litre/min of an air/fuel mix, reduced hydrocarbon emissions by 40%. Also, tests conducted on diesel emissions recorded a reduction of 25% carbon black at flow rates of 6.6 litres per minute of admixed gas with air/fuel mix 2,200 litres per minute.

Further tests carried out proved that the high pressure and temperature produced in the combustion chamber of a diesel engine, in particular, did not cause the admixed gas to pre-ignite before the top dead centre of the combustion stroke and overall cycle, which would have caused pre-ignition. The reason for this is due to the admixed gases' unique gaseous properties, where the calorific value is low. therefore the detonation temperature is high. In this test it proved to be higher than the diesel fuel^'s ignition temperature.

Internal combustion engines are known to be inefficient, in that up to 2/3 of the energy liberated during combustion is wasted: typically 40% as heat and 25% as exhaust pressure (also known as "blow down energy'). It would be useful to harness some of this otherwise wasted energy.

In this regard, the exhaust gases from the engine 12 are provided to a turbo fan/alternator unit 20. The function of the turbo fan/alternator unit 16 is to induce rotation of a shaft-mounted fan which, in turn, causes rotation of an alternator mounted on the shaft from which electrical energy is generated. A suitable form of turbo fan/alternator unit 20 is the " urboGenerators'^" model manufactured by the company AlliedSignal Inc. of 101 Columbia Road, Morristown, NJ 07862, USA. An AlliedSignal™ TurboGenerator of 25 kW rating (up to 120,000 rpm) would be suitable for matching with a 100 kW internal combustion engine, such as found in trucks and small marine vessels. The AC output from the unit 20 is passed to a rectifier unit 22, and a regulated DC output then provided to a battery unit 24. The battery unit 24 has a function of storing electrical charge, to be supplied on demand. Battery unit 24 supplies DC power to an electronic power controller 26 that includes a conventional controlled chopper circuit. The power controller has an output characteristic shown in Fig. 2a: chopped waveform having controlled t _n and t₍,n- periods. This is sometimes known also as the mark-to-space ratio. The output voltage level during t₀„ must be arranged to be sufficiently high to promote electrolysis of the water, including the necessary overvoltage, as is well known. By supplying the waveform of the nature shown in Fig. 2a to the gas generator 16, an average gas flow will be achieved. That is, strictly electrolysis ceases during the period t n', however because of inertia, there is an averaging of gas flow with time.

The volume of gas supplied must be regulated to match engine demand. There is an emperical relationship between a volume of admixed hydrogen and oxygen gases generated by the gas generator 16 and the volume of hydrocarbon fuel supplied to the engine 12. This relationship has been determined to be approximately linear with respect to engine revolutions, in the manner shown generally in Fig. 2b. The period t₀tτ reduces as the gas demand increases.

Of course, a limiting factor on the average volume of gas that can be provided by the gas generator 16 is the power available to be sourced from the battery unit 24. To account for this, a battery charge detector 28 senses the energy storage level of the battery unit 24, and provides a signal representative of this state to the power controller 26. If the power controller also receives a signal representative of the engine revolutions it can sense demanded gas load and control the DC power provided to the gas generator 16 accordingl)', subject to the electrical energy being available from the battery unit 24. If the gas flow requirement exceeds that which can be achieved by the electrical energy available from the battery unit 24. then the power controller 26 will clamp the 'volumetric flow^" in a manner shown by the dashed line in Fig. 2b.

It is also possible for the energy recovered by the turbo fan/alternator unit 20 simply to be stored in the battery unit 24, rather than being instantly consumed by the gas generator 16. In another broader form, the DC output from the rectifier 22 can be provided directly to the gas generator 16 in an unregulated manner.

Considering then the energy balance aspect of the embodiment of Fig. 1. A 30 kW internal combustion engine 12 produces approximately 7.5 kW of exhaust gas or blow down energy. The turbo fan/alternator 20 recovers typically 70% of the available energy, being 5.25 kW. 5.25 kW of electrical energy produces 1470 1/h of admixed hydrogen and oxygen gases. This volumetric flow rate, when combusted by the engine 12, produces an additional 3.8 kW of energy, which is a 12% recovery of the total energy available from the engine.

For a compound power plant mounted on a motor vehicle, it is possible also to take advantage of other available recoverable forms of energy. In a further embodiment, shown in Fig. 3. the power plant 10' further includes a wind generator 30 that supplies a further source of DC electrical energy to the battery unit 24. Any suitable wind generator can be chosen.

A yet further embodiment of the compound power plant, again suitable for use with a motor vehicle, is shown in Fig. 4. The compound power plant 10" shows a representative drive chain 32 extending from the engine 12, (e.g. tail shaft or wheel axles) by which motive power is transmitted. Mounted concentrically around the drive chain 32 is an alternator 34. The drive shaft acts as the rotor of the alternator, having permanent magnets mounted to it. The interaction of the magnetic field generated by the shaft with the stator windings produces an alternating electrical output which acts to load the shaft and cause it to slow. Thus, the rotational kinetic energy can be recovered. The electrical output is from the stator rectified and provided to the batten- unit 24.

It is desirable for the alternator 34 to be controlled in a switched manner to load the shaft vvhen the vehicle^'s braking system is activated by the driver. An example of such a regenerative braking system is that implemented in the Toyota™ Prius™ motor vehicle.

The increased electrical energy recovered from the exhaust gas means that other electrical loads 36 in a motor vehicle can be accommodated. For example, an electrical airconditioning unit can be implemented, removing the conventional belt-driven compressor and unburdening the engine to provide greater available power (when the airconditioner is being operated). Of course, the use of electrical energy for other loads (such as airconditioning) may reduce the energy available for the generation of admixed hydrogen and oxygen gases. There is an engineering compromise to be made. Other examples of electrical loads are lights and instrumentation.

Fig. 5 shows a side view of a vehicle, and the relative physical location of the elements of the compound power unit 10' of Fig. 3. It will be readily understood that the consumable fuels, water and hydrocarbon are required to be replenished.

The foregoing describes only some embodiments of the present invention, and modifications and/or changes can be made thereto without departing from the scope and spirit of the invention, the embodiment being illustrative and not restrictive.

Claims

Claims:

1. A compound power plant comprising: an internal combustion engine receiving a supply of hydrocarbon fuel; a gas generation electrolysis unit supplying admixed hydrogen and oxygen gases to be combusted with said hydrocarbon fuel by said internal combustion engine; and a turbo fan/alternator unit receiving the exhaust gases from said internal combustion engine and providing a DC power output therefrom coupled to the electrolysis unit.

2. A compound power plant as claimed in claim 1, further comprising: a battery unit receiving and storing DC power from said turbo fan/alternator unit; and a power controller receiving stored energy from said battery unit and controlling the amount of power supplied to the electrolysis unit.

3. A compound power supply as claimed in claim 2, wherein said power controller is operable to chop the DC power supply.

4. The compound power supply as claimed in claim 3, wherein the degree of chopping is such as to result in a volumetric flow of admixed gases from the electrolysis unit that is directly proportionally to revolutions of the internal combustion engine.

5. A compound power plant as claimed in claim 4, further comprising a battery charge sensor, sensing the available power from the battery unit and providing a signal thereof to said power controller, said signal being used by the power controller to control the degree of chop.

0 6. A compound power system as claimed in any one of the preceding claims, wherein the turbo fan/alternator unit produces AC power that is rectified to provide said DC power output.

7. A compound power plant as claimed in any one of the preceding claims, ^ further comprising a water reservoir providing a supply of water to the gas generator.

8. A compound power plant as claimed in claim 7, further comprising a fuel tank for supply of fuel to the internal combustion engine.

9. A compound combustion engine as claimed in claim 8, further comprising a wind generator, operable to convert wind energy to DC electrical energy to be provided to the battery unit.

10. A motor vehicle having a compound power plant as claimed in any one of the preceding claims.

1 1. A motor vehicle as claimed in claim 10, further comprising generator means coupled to the vehicle's drive train, the generator means coming into operation on activation of the vehicle's braking system to recover electrical energy from the kinetic energy of the drive train, said recovered electrical energy being in, or converted to DC form and provided to said battery unit.

12. A motor vehicle as claimed in claim 1 1, wherein said generator means is located on a tail shaft and/or wheel axles, said tail shaft and/or wheel axles carrying permanent magnets that act as the rotor of said generator means.

13. A marine vessel having a compound power plant as claimed in any one of claims 1 to 9.

14. A method for recovering waste energy from an internal combustion engine, the method comprising: converting volumetric flow of exhaust gases to electrical energy: utilising said stored electrical energy to electrolyse water to produce admixed hydrogen and oxygen gases; and utilising said admixed gases in the combustion process.

15. A method as claimed in claim 14, comprising the further steps of: storing said electrical energy: and controlling the amount of stored electrical energy used for electrolysis in accordance with internal combustion demand.