GB2384525A

GB2384525A - Adding water, eg steam, to the charge of a reciprocating piston i.c. engine to reduce emissions of particulate matter (PM) and NOx

Info

Publication number: GB2384525A
Application number: GB0200895A
Authority: GB
Inventors: William May Stott
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-01-15
Filing date: 2002-01-15
Publication date: 2003-07-30
Also published as: GB0200895D0

Abstract

The addition of water, eg steam, to the engine charge is a relatively simple, single process for reducing both PM and NOx emission levels in turbo diesel internal combustion engines. The reaction between air, steam and high temperature carbon (PM) absorbs heat, lowering the maximum combustion temperature and hence NOx. The water may be demineralised and added into the intake air as steam or water spray, injected directly into the cylinder or included in the fuel. A secondary fuel may also be added, eg methanol/alcohol, to improve combustion of the primary diesel fuel. The methanol/alcohol may act as an anti-freeze additive. The components and consumables are readily obtainable and may be incorporated and retrofitted easily into existing designs of engines.

Description

PATENT APPLICATION SPECIFICATION 1 Subject Reciprocating piston engine 2 Scope A single method whereby both the Particulate Matter (PM) and Nitrous Oxides (NOx) emissions may be reduced at source in diesel internal combustion engines 3 Introduction 3. 1 Background a) PM is the result of the incomplete combustion of the carbon in the fuel oil injection droplets allowing unburned carbon particles to be discharged via the exhaust to the atmosphere as harmful emissions b) NOxis the result of the formation of nitrogen with excess oxygen at high combustion temperatures to be discharged via the exhaust to the atmosphere as harmful emissions 3.2 Present day emission reduction treatment technology 3.2. 1 PM either by :- a) filtration to trap the PM which is retained until the filter service interval b) thermal or catalytic oxidation c) plasma reaction conversion d) combination of extremely high pressure and electronic injection systems 3.2. 2 NOx either by :- a) recirculation to the air intake of cooled exhaust gas (EGR) which has a higher specific heat content than the intake air, absorbing combustion heat, which lowers the maximum combustion temperature b) membrane selective permeation of the air c) storage type catalytic converter, which stores the oxides at normal exhaust temperatures and then boosts the exhaust temperature for a short period to release the stored oxides by converting to nitrogen 4 Proposal 4.1 To design out the problems at source 4. 1. 1 PM-by ensuring that the carbon is more completely burnt 4. 1. 2 NOx-by reducing the combustion maximum temperature 4.2 Possible Methods 4.2. 1 PM This is the result of either :- a) incomplete combustion of the rich fuel droplets b) carbon formations dislodged from combustion surfaces i. e. built up deposits c) carbon deposited in the exhaust system and released later.

In cases b) and c) they may be discounted, as proposed treatment will prevent reduce future deposits Method 1-In case a) the combustion process may be improved by the addition of a secondary fuel (SF) prior to the diesel Primary Fuel (PF) injection to assist in the burning rate of the PF droplets.

Method 2 - All PM generated can generally be assumed to be at the combustion high temperature and may be reduced by employing the Producer Gas Process (PGP) i. e. water gas 4.2. 2 NOx This is the result of the formation of nitrogen with the excess oxygen at the high combustion temperatures and may also be reduced by the producer gas process (PGP).

Method-In this process the reaction between the air, steam and high temperature carbon (PM) and forms the gases, carbon monoxide, hydrogen and carbon dioxide and in doing so absorbs considerable quantities of heat, lowering the maximum combustion temperature i. e. NOx. Thus also reducing the quantity of PM generated.

Note :-Whilst exhaust gas recirculation (EGR) also lowers the combustion temperature it must be cooled before being recycling the additional nitrogen and pollutants (unless treated) back through the engine. It also reduces the amount of oxygen available for combustion.

5 Basic Design Principle Proposed 5. 1 PM By supplying the PF with an additional amount of a more rapidly combustible type of fuel (SF) the PF oil droplets combustion burning rate and temperature will be increased, decreasing the quantity and temperature of the PM produced-see 5.2 5. 2 NO.

PGP application requires high temperature carbon (PM), air and H2O the resulting reaction absorbs large quantities of heat, lowering the combustion temperature and NOx generation. Only the addition of H20* is required and may be introduced either into the air intake system or injected direct into the cylinder see 5.3. 1 5.3. 1 PM By supplying an additional amount of another fuel secondary fuel (SF) with the turbo boost inlet air, as this pressure is sensitive/proportional to engine-load, the- combustion rate of the diesel main injection fuel oil droplets may be improved. This may be achieved by a variable flow system controlled by a signal from the turbo boost pressure. This can be achieved without imposing any additional air intake pressure drop loss, as no venturi demand valve is required.

Methanol/alcohol may be employed as a SF as it may also be required as an anti- freeze additive for the PGP-see 5. 3.2 The maximum quantity of SF supplied throughout the engine RPM range being maintained to be i) below the lower ignitable mixture limit and ii) limited such when combined with the PF not to exceed maximum engine power design limits.

However the introduction of a SF will reduce the quantity of the air intake and increase the combustion temperature 5.3. 2 NOx The application of the PGP to reduce NOx only requires the supply ofHzO. The most practical system being through the air intake manifold upstream of intercooler. a) if supplied as steam this would increase the intercooler air outlet temperature to the engine i. e. steam pressure ! temperature controlled by turbo air pressure

b) if as water spray/mist this could be used advantageously to lower the intercooler air outlet temperature to the engine.

6 Operation 6.1 Additional auxiliary equipment a) Water (demineralised) /doped (anti-freeze/corrosion) b) Contoured non-pressure storage tank (s) for-space availability c) Water pump (variable flow or spillback) and manifold nozzle d) Control/regulating system* o Note :-system suggested in 5.3. 1- As the turbo boost air pressure is proportional to the engine load. This can be used to provide signal (s) to control a contmuous variable water/solution spray supply via a pulsed or stepper motor controlled solenoid valve and nozzle. The spray nozzle being located in the intercooler outlet to engine manifold.

62 Engine The engine will continue to be operated in the normal conventional manner, with a warning system/interlocklo ensure that the emissions are being controlled as designed and that a sufficient quantity off 20/solution is available for treatment of the on-board quantity of PF 7 Summary From the above the most acceptable practical, economic and simple design/method is the Producer Gas Process as :- a) both PM and Nos treatments are performed by the single process b) the use of methanol/alcohol is satisfactory for both SF and anti-freeze purposes when required c) H2O/solution introduction after the intercooler provides a simple controlled single continuous point which enables the intake air temperature to the engine to

be reduced further 7.1 Advantages- a) Simple basic dual purpose-system b) PM reduction at source i. e. combustion chamber c) NOx reduction at source i. e. combustion chamber d) H2O is available in satisfactory form as demineralised water with a higher latent heat value than EGR - e) Methanol/alcohol is a readily available/acceptable SF fuel with a higher latent heat value than EGR f) Methanol/alcohol may also be required as an anti-freeze agent d) H2O/solution can be stored in non-pressure contoured tank (s) e) H 20/anti-freeze solution may also provide a SF source f) Failure of system does not affect primary power source, only emissions levels g) PGP as employed to reduce PM will also lower the maximum combustion temperature reducing NOx production h) PGP can be employed advantageously replacing present EGR method i, e. cooled EGR restricts combustion oxygen availability and recirculates pollutants unless treated and additional nitrogen back through engine i) System can be readily incorporated/retrofitted to existing vehicles and engines

7.2 Disadvantages a) additional space/weight required for equipment b) additional control/pumping/equipment c) corrosion of materials-solutions used may cause new problems d) the need to provide and service separate tanks with dedicated filling points

Claims

8 Claims 1. A simple single system to reduce both Particulate Matter and Nitrous Oxides 2. PM reduction at source 3. NOx reduction at source 4. Water in demineralised form is readily obtainable 5. Water/solution can be stored in non-pressure contoured tanks for space considerations 6. Methanol/alcohol is an acceptable ecological fuel source and readily obtainable 7. Methanol/alcohol when required for anti-freeze agent is also acceptable as SF source 8. Water/Methanol have high latent heat properties 9. System failure does not affect primary power source only emissions i. e. fail-safe 10. No major engine modifications i. e. limited to intake manifold spray nozzle and turbo pressure point fitting 11. Simple control system utilising turbo boost pressure signal 12. Can be readily retrofitted to existing vehicles and engines 13. PGP does not recycle pollutants and additional quantities of nitrogen back through engine unlike EGR equipment 14. The method of PGP HO/solution application can be by either :- a) integrating the H20/solution in the fuel (commercial problems) b) providing a separate direct cylinder H20/solution injection system (applicable to new engine designs only)

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Amendments to the claims have been filed as follows CLAIMS 1. A single simple method whereby both the Particulate Matter (PM) and Nitrous Oxides (NOx) emissions may be reduced at source in diesel internal combustion engines, the additional equipment does not affect nor interferes with the normal engine diesel fuel equipment, design limits, operational or servicing modes.

2. A method as claimed in claim 1 wherein the equipment can be readily fitted to existing turbo diesel engine installations 3. A method as claimed in claim I wherein the water in demineralised form is readily obtainable 4. A method as claimed in claim I wherein Methanol/alcohol when required for anti- freeze agent is also acceptable as SF source 5. PM reduction at source 6. NOx reduction at source 7. Water 8. Water/solution can be stored in non-pressure contoured tanks for space considerations 9. Methanol/alcohol is an acceptable ecological fuel source and readily obtainable 10.

11. Water/Methanol have high latent heat properties 12. System failure does not affect primary power source only emissions i. e. fail-safe 13. No major engine modifications i. e. limited to intake manifold spray nozzle and turbo pressure point fitting 14. Simple control system utilising turbo boost pressure signal 15. Can be readily retrofitted to existing vehicles and engines 16. PGP does not recycle pollutants and additional quantities of nitrogen back through engine unlike EGR equipment 17. The method of PGP H20/solution application can be by either :- a) integrating the I-O/solution in the fuel (commercial problems) b) providing a separate direct cylinder H2O/solution injection system (applicable to new engine designs only)