GB2564906A

GB2564906A - Enhanced combustion engine

Info

Publication number: GB2564906A
Application number: GB1712111.2A
Authority: GB
Inventors: Mcmahon Gary
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-07-27
Filing date: 2017-07-27
Publication date: 2019-01-30
Also published as: WO2019021022A1; GB201712111D0

Abstract

A dual-fuel combustion engine comprises an air intake system 14, a combustion chamber 12, an exhaust system 16, a primary fuel source 18 and a secondary fuel source 30. The primary fuel may be diesel; the secondary fuel may be LPG, LNG, compressed natural gas, methane, hydrogen or oxyhydrogen. A controller 32 uses feedback control of the delivery of the secondary fuel in order to minimise emissions measured by a sensor 34 provided eg in the exhaust system 16. The secondary fuel may be introduced at the compressor 24 of a turbocharger 20. The sensor 34 may sense oxygen, opacity, CO2, NOx or particulates. The controller (ECU) 32 may be separate from the main engine ECU. The maximum proportion of secondary fuel 12 may be less than 25%, preferably less than 15%, so as to cause cracking of the primary fuel, thereby causing more complete combustion of the primary fuel.

Description

Enhanced Combustion Engine

The present invention relates to combustion engines. In particular, but not exclusively, the present invention relates to combustion engines which utilise two fuel sources.

It is known to provide combustion engines for vehicles which operate using more than one fuel source. In dual fuel vehicles, typically a primary fuel source of petrol or diesel is used, along with a secondary fuel such as natural gas, liquid petroleum gas (LPG), or hydrogen. The secondary fuel is used as a replacement fuel and it is common for the engine to run on one fuel at a time. However, in some known vehicles, both fuels are used simultaneously. A typical primary/secondary fuel ratio used in such vehicles is 40/60 % for high-speed engines. For low speed engines, it is possible to reach a primary/secondary fuel ratio of 10/90 %. In all known vehicles of this type, the minimum proportion of secondary fuel is substantially greater than 25%.

Combustion in engines involves a complicated sequence of elementary radical reactions. When there is complete combustion, a hydrocarbon burns in oxygen and the reaction produces carbon dioxide and water. Each fuel molecule is provided with the exact amount of oxygen molecules (the stochiometric ratio). However, complete combustion is very difficult to achieve, since this chemical equilibrium is not necessarily present (at all or in all regions of the combustion chamber). Incomplete combustion due to insufficient oxygen results in unburnt products such as carbon monoxide, hydrogen and carbon (soot). On the other hand, too much oxygen is also undesirable. Combustion at high temperatures in atmospheric air will produce nitrogen oxides, commonly referred to as NOx gases.

Hydrocarbon cracking is the process of breaking a long-chain of hydrocarbons into short ones. This is typically done to produce useful products. For example, hydrocracking is a major source of jet fuel and diesel fuel, and further cracking yields LPG. Short chain hydrocarbons are easier to ignite and provide more energy per mass than long chain ones.

WO 2013/061094 by the present Applicant first disclosed the principle of using hydrocarbon cracking within engines to improve combustion and performance. In contrast to existing dual fuel vehicles, only a small amount of secondary fuel is used. The secondary fuel is used as a reagent to crack the primary fuel, splitting the long chains of hydrocarbons into shorter ones which are more easily combusted. The actual amount of secondary fuel which is injected is determined according to a fuel mapping profile. This profile specifies the amount of secondary fuel to be injected for a number of engine states, the main states being: 'idle', 'cruise', 'normal' and 'other'. The system of WO 2013/061094 has been shown to provide substantial improvements in fuel efficiency and performance. However, it is recognised by the Applicant that further improvements could be achieved if the secondary fuel injection was more dynamically responsive to real time engine behaviour, rather than a few general engine states.

It is known to use automotive oxygen sensors, or Lambda sensors, for electronic fuel injection and emission control. The sensors, located in the exhaust stream, can determine in real time if the air-fuel ratio (AFR) of a combustion engine is rich or lean based on emissions from the engine. Closed loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data. Modern spark-ignited combustion engines use oxygen sensors and catalytic converters in order to reduce exhaust emissions. Oxygen concentration data is sent to the engine control unit (ECU) which adjusts the amount of fuel injected into the engine to compensate for excess air or excess fuel. The ECU attempts to maintain, on average, a stoichiometric AFR based on the oxygen sensor data.

According to a first aspect of the present invention there is provided a combustion engine comprising:

a combustion chamber;

an exhaust system;

a primary fuel source;

a secondary fuel source;

a controller configured to deliver a quantity of secondary fuel to the combustion chamber; and a first sensor provided at the exhaust system for measuring emissions of the combustion engine and communicatively connected to the controller, wherein the controller is configured to vary the quantity of secondary fuel delivered to the combustion chamber based on the emissions measured by the first sensor.

Optionally, the controller is configured to vary the quantity of secondary fuel delivered to the combustion chamber to reduce pollutants in the emissions.

Optionally, the controller is configured to vary the quantity of secondary fuel between zero and a maximum proportion of the total fuel delivered to the combustion chamber.

Optionally, the maximum proportion is less than 25%. Optionally, the maximum proportion is less than 15%.

Optionally, the controller comprises an ECU. Optionally, the controller is separate from the main ECU for the engine.

Optionally, the primary fuel comprises diesel. Alternatively, the primary fuel comprises petrol.

Optionally, the secondary fuel comprises LPG. Alternatively, the secondary fuel comprises liquefied natural gas, compressed natural gas, methane, hydrogen or oxyhydrogen (Brown's gas).

Optionally, the secondary fuel is delivered to the intake air of the engine.

Optionally, the first sensor comprises an oxygen sensor. Optionally, the first sensor comprises a wide band Lambda sensor.

Alternatively or in addition, the first sensor comprises a laser or light sensor adapted to measure the opacity of the emissions.

Alternatively or in addition, the first sensor comprises a carbon dioxide sensor.

Alternatively or in addition, the first sensor comprises a particulate sensor.

Alternatively or in addition, the first sensor comprises a Nox sensor.

According to a second aspect of the present invention there is provided a method of enhancing combustion within an engine having a combustion chamber, an exhaust system and a primary fuel source, the method comprising:

providing a secondary fuel source;

providing a controller configured to deliver a quantity of secondary fuel to the combustion chamber; and providing a first sensor at the exhaust system for measuring emissions of the combustion engine and communicatively connecting the first sensor to the controller, wherein the method includes configuring the controller to vary the quantity of secondary fuel delivered to the combustion chamber based on the emissions measured by the first sensor.

Optionally, the method includes configuring the controller to vary the quantity of secondary fuel delivered to the combustion chamber to reduce pollutants in the emissions.

Optionally, the method includes varying the quantity of secondary fuel between zero and a maximum proportion of the total fuel delivered to the combustion chamber. Optionally, the maximum proportion is less than 25%. Optionally, the maximum proportion is less than 15%.

Optionally, the method includes providing a controller which is separate from the main ECU for the engine.

Optionally, the method includes delivering the secondary fuel to the intake air of the engine.

Optionally, the method includes measuring the opacity of the emissions.

According to a third aspect ofthe present invention there is provided a sensor adapted to measure the emissions from a combustion engine, wherein the sensor is adapted to measure the opacity of the emissions.

Optionally, the sensor comprises a laser or light sensor.

Optionally, the sensor is provided at the exhaust system ofthe engine.

The invention will be described below, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of an engine in accordance with the invention;

Figure 1 shows a combustion engine 10 of a vehicle which has a combustion chamber 12, an air intake system 14, and an exhaust system 16. A primary fuel in the form of diesel is delivered from a first fuel tank 18 to the combustion chamber 12. The combustion chamber 12 also receives air 100 from the air intake system 14. The air 100 is compressed in the combustion chamber 12 which causes the temperature within the combustion chamber 12 to rise and this causes ignition of the fuel. The resulting exhaust gas 102 is removed from the combustion chamber 12 by the exhaust system 16. Flow of the exhaust gas 102 powers a turbine 22 of a turbocharger 20. The turbine 22 operates a compressor 24 of the turbocharger 20 which drives air 100 in the air intake system 14 towards the combustion chamber 12.

The engine 10 also has a secondary fuel tank 30 which contains a secondary fuel in the form of LPG. The LPG is introduced to the engine 10 at the compressor 24 where it mixes with the intake air 100 and is then also delivered to the combustion chamber 12. A controller 32 includes a valve which controls the amount of LPG that is passed to the compressor 24.

During combustion, compression of the air/gas mixture splits the short-chained LPG into even shorter-chained molecules known as radicals. The radicals are then present in the combustion chamber 12 and bind with the longer-chained diesel hydrocarbons, causing the diesel to split into shorter molecules that are more easily combusted.

A first sensor in the form of an oxygen sensor 34 is provided at the exhaust system 16 and this measures the emissions of the engine 10. The oxygen sensor 34 outputs a signal corresponding to the amount of measured emissions to the controller 32.

The controller receives the signal from the oxygen sensor 34 and responsively varies the quantity of LPG delivered to the combustion chamber 12. This will cause a change in the emissions of the engine 10, which causes a change in the output of the oxygen sensor 34. In other words, there is a closed feedback loop involving emissions and the amount of LPG delivered to the engine 10. The objective is to continuously vary the quantity of LPG delivered to achieve the lowest amount of pollutants in the emissions.

Only a small amount of LPG fuel is delivered. Typically, the maximum proportion of LPG relative to the amount of diesel fuel delivered to the engine 10 is less than 15%. This is because the primary purpose of the LPG is to cause cracking of the diesel fuel to promote combustion. The cracking process encourages a chemical chain reaction to take place throughout the chamber 12 which results in a more homogeneous fuel/air mix.

Fuels such as diesel are relatively slow to combust which prevents some of the hydrocarbons from fully burning. The long-chain hydrocarbons also have a tendency to coalesce, preventing efficient mixing with air or oxygen during the combustion process. Typically, a conventional heavy duty diesel engine combusts only up to 80% of the fuel present. An engine according to the invention aims to increase this figure closer to 100%, by enhancing the combustion process.

The proportion of LPG delivered is dependent on the amount of diesel delivered and is generally less than 15% by volume of the delivered diesel. There is no overt control of the primary fuelling of the engine. The volume of the diesel used in the engine is determined in real time. This volume can be determined by measuring the pressure in the fuel rail and the opening time of the injector used to introduce the diesel into the engine. The pressure in the fuel rail can be determined using data obtained from a data bus connection such as the CAN bus.

The volume of LPG required is calculated based on the determined amount of diesel and the measured emissions. The amount of LPG required is translated into the required opening times for the injectors which control the delivery of the LPG. The injector opening times can be adjusted according to the pressure and temperature of LPG.

The controller 32 includes a processor for performing the calculations and a memory. The algorithms which control the operation of the system are stored in the memory and can be implemented in software, firmware or a combination of both.

The controller is an ECU but it is separate from the main ECU for the engine 10. The main ECU can therefore be the existing and unmodified ECU for the engine. Also, the oxygen sensor 34 could be the existing sensor present in the vehicle and used to maintain the AFR. Indeed, most of the components are standard and unmodified engine components. The invention in the form of the controller 32 and second fuel tank 30 can easily be retrofitted to a conventional engine.

In other embodiments of the invention, other types of sensors can used in addition to or in replace of the oxygen sensor 34 for quantifying emissions. For instance, a laser or light sensor could be used to measure the opacity of the emissions. The greater the amount of pollutants in the emissions, the opaquer they will be. A carbon dioxide sensor or Nox sensor or a particulate sensor could also be used.

The present invention provides a number of advantages. The main advantages are fuel efficiency and improved emissions. Testing has found that the invention provides fuel savings of greater than 25%. Regarding emissions, carbon particulate was reduced by up to 95%, Nox was reduced by 80% and CO2/CO emissions were reduced by 30%.

Various modifications and improvements can be made to the above without departing from the scope of the invention.

Claims

1. A combustion engine comprising:

a combustion chamber;

an exhaust system;

a primary fuel source;

a secondary fuel source;

2. A combustion engine in accordance with Claim 1, wherein the controller is configured to vary the quantity of secondary fuel delivered to the combustion chamber to reduce pollutants in the emissions.

3. A combustion engine in accordance with Claim 1 or 2, wherein the controller is configured to vary the quantity of secondary fuel between zero and a maximum proportion of the total fuel delivered to the combustion chamber.

4. A combustion engine in accordance with any preceding claim, wherein the maximum proportion is less than 25%.

5. A combustion engine in accordance with any preceding claim, wherein the maximum proportion is less than 15%.

6. A combustion engine in accordance with any preceding claim, wherein the controller comprises an ECU which is separate from the main ECU for the engine.

7. A combustion engine in accordance with any preceding claim, wherein the primary fuel comprises diesel.

8. A combustion engine in accordance with any preceding claim, wherein the secondary fuel comprises LPG.

9. A combustion engine in accordance with any preceding claim, wherein the secondary fuel comprises liquefied natural gas, compressed natural gas, methane, hydrogen or oxyhydrogen.

10. A combustion engine in accordance with any preceding claim, wherein the secondary fuel is delivered to the intake air of the engine.

11. A combustion engine in accordance with any preceding claim, wherein the first sensor comprises an oxygen sensor.

12. A combustion engine in accordance with Claim 11, wherein the first sensor comprises a wide band Lambda sensor.

13. A combustion engine in accordance with any of Claims 1 to 10, wherein the first sensor comprises a laser or light sensor adapted to measure the opacity of the emissions.

14. A combustion engine in accordance with any of Claims 1 to 10, wherein the first sensor comprises a carbon dioxide sensor.

15. A combustion engine in accordance with any of Claims 1 to 10, wherein the first sensor comprises a particulate sensor.

16. A combustion engine in accordance with any of Claims 1 to 10, wherein the first sensor comprises a Nox sensor.

17. A method of enhancing combustion within an engine having a combustion chamber, an exhaust system and a primary fuel source, the method comprising:

providing a secondary fuel source;

18. A method in accordance with Claim 17, including configuring the controller to vary the quantity of secondary fuel delivered to the combustion chamber to reduce pollutants in the emissions.

19. A method in accordance with Claim 17 or 18, including varying the quantity of secondary fuel between zero and a maximum proportion of the total fuel delivered to the combustion chamber.

20. A method in accordance with Claim 19, wherein the maximum proportion is less than 25%.

21. A method in accordance with Claim 19, wherein the maximum proportion is less than 15%.

22. A method in accordance with any of Claims 17 to 21, including providing a controller which is separate from the main ECU for the engine.

23. A method in accordance with any of Claims 17 to 22, including delivering the secondary fuel to the intake air of the engine.

24. A method in accordance with any of Claims 17 to 23, including measuring the opacity of the emissions.

5

25. A sensor adapted to measure the emissions from a combustion engine, wherein the sensor is adapted to measure the opacity of the emissions.

26. A sensor in accordance with Claim 25, wherein the sensor comprises a laser or light sensor.

27. A sensor in accordance with Claim 25 or 26, wherein the sensor is provided at the exhaust system of the engine.