Method and Device for Controlling the Injecting of a Non-Combustible Fluid

Abstract

The present subject matter provides a device and a method for injecting non-combustible fluid into an internal combustion. In order to reduce the non-combustible fluid consumption, the fluid to be injected is heated to a predefined temperature which improves the spray characteristics, reduces wall wetting and leads to a better vaporization of the fluid in the combustion chamber.

Claims

1. Control device (200) for controlling injection of a non-combustible fluid into an internal combustion engine, the internal combustion engine having at least one cylinder (100), and at least one noncombustible fluid injector (9) configured to inject a non-combustible fluid into the internal combustion engine, wherein the control device (200) is configured to control the temperature of the non-combustible fluid to arrive at a predefined temperature value, to determine an amount of non-combustible fluid to be injected based on the temperature of the non-combustible fluid, and to control the non-combustible fluid injector (9) to inject the determined amount of non-combustible fluid into the internal combustion engine.

2. Control device (200) according to claim 1, wherein the control device (200) is configured to heat the non-combustible fluid and to decrease the amount of non-combustible fluid to be injected with an increase of the temperature of the non-combustible fluid.

3. Control device (200) according to claim 1, wherein the control device (200) is configured to detect and/or to predict a start and a duration of the transient operating mode, and to control the non-combustible fluid injector (9) to inject the non-combustible fluid into the internal combustion engine when the internal combustion engine operates in a transient operating mode.

4. Control device (200) according to claim 1, wherein, at the same temperature of the non-combustible fluid, the control device (200) is configured to determine a higher amount of non-combustible fluid to be injected during a transient operation than during a steady state mode.

5. Control device (200) according to claim 1, wherein the control device (200) is configured to control the pressure at which the noncombustible fluid is injected to maintain a predefined pressure value.

6. Control device (200) according to claim 1, wherein the noncombustible fluid is water and the predefined temperature value of the water is at least 15° C.

7. Control device (200) according to claim 1, wherein the noncombustible fluid is water and the predefined pressure value is at least 1 bar higher than the pressure of the atmosphere into which the water is injected.

8. A system comprising: the control device (200) according to claim 1, an internal combustion engine, the internal combustion engine having at least one cylinder (100), and at least one non-combustible fluid injector (9) configured to inject a non-combustible fluid into the internal combustion engine, and at least one heating device configured to provide heat for heating the non-combustible fluid to a predefined temperature value.

9. The system according to claim 8, wherein at least one of the heating devices is an electrical heater.

10. The system according to claim 8, further comprising at least one conversion unit, configured to convert thermal energy into electrical energy for providing electrical power to at least one of the electrical heaters.

11. The system according to claim 8, wherein at least one of the heating devices is a heat exchanger (15, 15a) comprising at least one flow path for the non-combustible fluid, and at least one flow path for the exhaust gas of the internal combustion engine.

12. The system according to claim 8, wherein at least one of the heating devices is a heat exchanger (15, 15a) comprising at least one flow path for the non-combustible fluid, and at least one flow path for coolant of the internal combustion engine.

13. The system according to claim 8, wherein at least one of the heating devices is disposed at the non-combustible fluid injector (9).

14. The system according to claim 8, further comprising at least one tank (10, 10a) for storing the non-combustible fluid, wherein at least one of the heating devices is disposed at at least one tank (10, 10a).

15. Method for controlling injection of a non-combustible fluid into an internal combustion engine, the internal combustion engine having at least one cylinder (100), and at least one non-combustible fluid injector (9) configured to inject a non-combustible fluid into the internal combustion engine, wherein controlling the temperature of the non-combustible fluid to arrive at a predefined temperature value, determining an amount of non-combustible fluid to be injected based on the temperature of the non-combustible fluid, and controlling the non-combustible fluid injector (9) to inject the determined amount of non-combustible fluid into the internal combustion engine.

16. A computer program product storable in a memory comprising instructions which, when carried out by a computer, cause the computer to perform the method according to claim 15.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0048] FIG. 1 depicts a schematic view of a cylinder of an internal combustion engine with water injection into the intake port;

[0049] FIG. 2 (FIGS. 2a-2c) illustrates the different fluid properties of water and gasoline or heptane;

[0050] FIG. 3 depicts a flow chart of the claimed control method;

[0051] FIG. 4 (FIGS. 4a-4b) depicts two signal-time-diagrams with a schematic trend of engine load, water amount and injected water temperature;

[0052] FIG. 5 (FIGS. 5a-5b) illustrates two examples for arranging the components of a water injection system;

[0053] FIG. 6 (FIGS. 6a-6b) shows two schematic examples of a heat exchanger;

[0054] FIG. 7 (FIGS. 7a-7c) illustrates three examples for arranging the water pump and the heating devices.

DESCRIPTION OF EMBODIMENTS

[0055] FIG. 1 depicts an exemplary cylinder 100 of an otherwise unspecified internal combustion engine, which may have more than one cylinder 100. The engine may, for example, have two, three, four, six, eight or less/more cylinders 100. The cylinder 100 comprises a combustion chamber 1 in which a piston 2 with a connecting rod 3 is disposed allowing it to travel. The connecting rod 3 is connected to a crankshaft (not depicted) that can be a crankshaft as known.

[0056] An (air) intake port 4 with an intake valve 6 as well as an exhaust port 5 with an exhaust valve 7 are connected to the combustion chamber 1. Ambient air is drawn into the combustion chamber 1 through the intake port 4. Exhaust gases are discharged from the combustion chamber 1 via the exhaust port 5. A spark ignition unit 12 comprising a spark plug 12a and an ignition coil 12b is attached to the internal combustion engine. The spark ignition unit 12 preferably offers a variable spark duration or multi-spark ignition. The internal combustion engine (or briefly: “combustion engine” or “engine”) may have one or more spark ignition units 12. Preferably, it has at least one spark ignition unit(s) 12 per cylinder 100. The spark plug 12a as well as a fuel injector 8, or at least parts thereof, are connected to the inside of the combustion chamber 1 so that a spark and fuel can be introduced/injected into the combustion chamber 1. The high-pressure fuel supply of the fuel injector 8 is not depicted. The fuel injector 8 may preferably be a direct fuel injector 8. Further, the fuel injector 8 may preferably be an electrohydraulic fuel injector or a piezoelectric fuel injector.

[0057] Further, a non-combustible fuel injector 9 is connected to the intake port 4 of the cylinder 100. Since most preferably the liquid to be injected is water, even though other liquids having a high evaporation enthalpy may be used as well, the term “water injector” is used as one specific example for a non-combustible fuel injector 9. The water injector 9 may be a low-pressure injector with an injection pressure of up to 15 bar or a high-pressure injector with an injection pressure of more than 15 bar. As an alternative to the water injector 9 connected to the intake port 4 (as shown in FIG. 1), or in addition thereto, one or more water injectors 9 may be connected to the cylinder wall 14 of one cylinder 100 to inject water directly into the combustion chamber 1.

[0058] A control unit 200 for controlling the water injection into the internal combustion engine is further shown in FIG. 1. The control unit 200 has a plurality of subunits which are placed at different positions of the vehicle.

[0059] One of these subunits is the water pressure and temperature control unit 201 which is configured to adjust and to control the pressure and the temperature of the water to be injected. For this purpose, the water pressure and temperature control unit 201 receives the target values for the water temperature and pressure from the control unit 200 by signal lines and controls the heating unit (not depicted) to provide the demanded water temperature and the pressure unit (not depicted) to provide the demanded pressure. The control unit 200 receives the actual pressure and temperature of the water to be injected from pressure and temperature sensors (not depicted) disposed in the water pipe close to the injector 9 or disposed inside the injector 9 or disposed at any other place of the water system suitable for detecting the relevant water pressure and temperature. Therefore, a feed-back control of the water pressure and temperature can be realized.

[0060] The control unit 200 may determine the amount of water to be injected by the injector 9 in accordance with predefined internal combustion engine states. E.g., the control unit 200 may use a map, a table or the like to determine the amount of water to be injected depending on the engine state, which may be defined by parameters and which are used to look up the amount of water to be injected. Subsequently, the control unit 200 may adapt the water amount based on the general state of the engine in accordance to the measured or estimated temperature and/or the measured or estimated pressure of the water to be injected. This adaption of the water amount may also be provided in a map, a table or the like or may be calculated based on equations.

[0061] The control unit 200 is electrically connected to the spark ignition unit 12, the direct fuel injector 8 and the water injector 9 and controls the multiple units/injectors/actuators. The control unit 200 may, for example, be the engine control unit (ECU) and the water pressure and temperature control unit 201 may be a part of the ECU or a separate subunit.

[0062] It may also be possible to implement the feed-back control of the water pressure and the water temperature into the water pressure and temperature control unit 201. In that case, the pressure and temperature sensors may be connected thereto. Furthermore, the calculation of the water amount depending on the water pressure and the water temperature may also be implemented in the water pressure and temperature control unit 201.

[0063] The control unit 200 may also be any other control unit, and signal line connections between the control unit 200 and the controlled units may differ from the example of FIG. 1. For example, there may be a plurality of control units 200 which may control subgroups of the controlled units, e.g. one control unit 200-1 may control only fuel injectors 8, another control unit 200-2 may control only water injectors 9 and so on. Even further, if there is a plurality of control units 200, these control units 200 may be interconnected with each other hierarchically or in another way. Alternatively, there may be one single control unit 200 which includes all the control functions of the multiple actuators.

[0064] Further, pressure sensors which are not shown may be disposed in the combustion chamber wall 14 so that the pressure within the combustion chamber 1 can be measured. Measuring the pressure within the combustion chamber 1 can support a feedback control of the amount of water to be injected.

[0065] To further explain the effects leading to an improved atomization of the preheated injected water, the FIGS. 2a to 2c show a comparison of the fluid properties of water and gasoline or heptane which is used as a reference for gasoline. FIG. 2a shows a table which depicts the fluid properties of water and heptane at 25° C. It becomes clear that the density of water at 25° C. is significantly higher than the density of heptane. Therefore, the Reynolds number of water at that temperature is only 64% of the Reynolds number of gasoline. Furthermore, FIG. 2a shows that the surface density of water at 25° C. is higher than the surface density of heptane, which leads to a Weber number which is only 44% of the Weber number of heptane. Hence, the spray characteristics of water at 25° C. are worse compared to heptane, and therefore, using a port water injection, a higher amount of water condenses at the intake port walls compared to a port fuel injection of gasoline. The kinetic viscosity of water is however strongly dependent on its temperature which is not the case for gasoline, as FIG. 2b clearly depicts. Therefore, as the inventors found out, the Reynold number of water can be equalized to the Reynolds number of gasoline by heating up the water to 47° C., as shown in FIG. 2c. In other words, the spray characteristics of water can be adapted to the spray characteristics of gasoline by using water which has a temperature of approximately 47° C.

[0066] The flow chart of FIG. 3 depicts an example for a possible sequence of steps for controlling the amount of water to be injected at steady state and transient conditions. In this example the non-combustible fluid may be water and the predefined temperature of the water to be injected may be 100° C., but the controlling sequence is not limited to these conditions. Other liquids having a high evaporation enthalpy may be used as well and other predefined injection temperature values may also be used.

[0067] After checking whether water injection in general is necessary, which e.g. may be the case when the engine operates at a high load, it is determined whether the engine operates in transient or steady state mode. Depending on the determined engine operating mode, the steps S210 to S213 or S220 to S223 are performed. For transient operation the water amount based on the engine operating conditions is determined in step S220. In step S221 the previously determined water amount is adapted depending on the temperature of the water to be injected. Subsequently, water injection is executed in step S222. In the case that the water temperature is below the boiling point, which is chosen as predefined injection temperature in this example, the water is further heated up (S223). Other predefined temperature values than the boiling point may also be used.

[0068] Next the sequence starts again by checking the engine conditions (need of water injection in general and transient or steady state operating mode). When steady state operating mode is detected the water amount which is necessary for steady state operation is determined based on the engine operating conditions in step S210. Then the previously determined water amount is adapted depending on the temperature of the water to be injected (S211) and water injection is executed (S212). In the case that the water temperature is below the boiling point, the water is further heated up (S213). Then the sequence starts again and is repeated for steady state or transient operating mode until the engine reaches an operating point in which no water injection is required. In the above example, it should be understood that some steps may be left out and/or repeated. For example, several checking steps may be carried out subsequently or in parallel to determine the required water amount.

[0069] The FIGS. 4a and 4b illustrate the dependency of the injected amount of water on the temperature thereof. In this example water was again used as one example for a non-combustible fluid. In FIG. 4a a typical engine load increase/acceleration is depicted as an example starting at a first time T1 and ending at a second time T2. During each load increase water was injected at different temperatures (40° C., 60° C., 80° C. and 99° C.) and the water temperature was maintained constant during the acceleration. It is clearly recognizable that the required amount of water decreases with increasing water temperature and stays constant during the acceleration. In FIG. 4b the same example of an engine load increase/acceleration is depicted extended by a steady state operation at the load the engine reaches at the end of the acceleration. Different to the conditions in FIG. 4a, the water temperature was changed during the load increase from 40° C. to 99° C. in various ways. When the water temperature is maintained constant at 40° C. (solid line) the amount of water to be injected must be increased at the start of the acceleration and kept constant until the end of the acceleration. When the engine reaches a steady state operating point at a higher load compared to the operating point before the acceleration, the water amount can be reduced but stays higher than before the acceleration. When the water is heated up from 40° C. to 99° C. (broken lines) the previously increased water amount to be injected for transient operating mode can be decreased during the acceleration depending on the increasing water temperature. Furthermore, the required amount of water in steady state mode, injecting water having a temperature of 99° C., is lower compared to the required water amount at 40° C. water temperature.

[0070] The FIGS. 5a and 5b depict two different examples of arranging heat exchangers 15, 15a and pumps 16, 16a to deliver the water, or another non-combustible fluid, from the tanks 10, 10a to the injector 9 at the demanded temperature and pressure. In this example water was again used as one example for a non-combustible fluid. In FIG. 5a the heat exchanger 15 is disposed at the water tank 10 and the water pump 16 is disposed between the tank 10 and the water injector 9. In that case, the water pump 16 has to compress preheated water. FIG. 5b shows an arrangement which includes two water pumps 16, 16a and two water tanks 10, 10a. The heat exchanger 15 is disposed at the smaller second water tank 10a, which is positioned between the two water pumps 16, 16a. The water from the water tank 10 is pre-compressed by the water pump 10 before it reaches the second tank 10a in which it is heated up by the heat exchanger 15. The second water pump 16a compresses the water to the predefined pressure value at which it is injected into by the water injector 9. The present application is not limited to the water system arrangements depicted in the FIGS. 5a and 5b. Further arrangements with more than two water tanks, more than one heat exchanger and more than two water pumps may be feasible. Furthermore, the positions of the heat exchangers, the water tanks and the water pumps may be changed. An especially preferred application scenario for the heat up as shown by FIGS. 5a and 5b may relate to hybrid electric vehicles in which the coolant water temperature may frequently decrease due to frequent engine stops. The above explained heat up of the water of FIGS. 5a and 5b can realize that the water to be injected at the water injector reliably has the correct, predefined temperature value achieved with an efficient heating control strategy.

[0071] The FIGS. 6a and 6b show two different ways to transfer heat by a heat exchanger 15 which may be used for heating or cooling the non-combustible fluid, which preferably is water. FIG. 6a shows the heat exchanger 15 thermally connected to the coolant of the engine and FIG. 6b shows the heat exchanger 15 thermally connected to the exhaust gas of the engine. The heat exchanger 15 may be designed as plate heat exchanger, plate-fin heat exchanger or shell and tube heat exchanger or any further design suitable for the use in vehicles. The heat exchanger 15 may be disposed at a tank 10, 10a for storing the non-combustible fluid or along the non-combustible fluid pipe, preferably close to the fluid injector.

[0072] The FIGS. 7a to 7c illustrate three examples for disposing heating units in relation to the pump 16. The heating units may be used for heating (or cooling) the noncombustible fluid, which preferably is water. In FIG. 7a one water pump 16 is arranged behind a single heat exchanger 15. FIG. 7b depicts the arrangement of FIG. 7a extended by a second heat exchanger 15a, which preferably should exchange heat without pressure losses since it is arranged behind the water pump 16. FIG. 7c shows a single water heater 17 disposed behind the water pump which provides heat without producing pressure losses. The claimed subject matter is not limited to the examples depicted in the FIGS. 7a to 7c. The number and the layout of the heating units may vary and different positions of the water pumps and the heat exchangers may be possible as well.

[0073] It is summarized that the present subject-matter enables saving non-combustible fluid, such as water, by avoiding wall wetting when using an internal combustion engine having water injection to suppress knocking at high engine loads and during transient driving situations.

[0074] While the above describes a particular order of operations performed by certain aspects and examples, it should be understood that such order is exemplary, as alternatives may perform the operations in a different order, combine certain operations, overlap certain operations, or the like. References in the specification to a given aspect indicate that the aspect described may include a particular feature, structure, or characteristic, but every aspect may not necessarily include the particular feature, structure, or characteristic. The features which are described herein and which are shown by the Figures may be combined. The herein described and claimed subject-matter shall also entail these combinations as long as they fall under scope of the independent claims.

[0075] It should again be noted that the description and drawings merely illustrate the principles of the proposed methods, devices and systems. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the claimed subjectmatter and are included within its spirit and scope.

[0076] Furthermore, it should be noted that steps of various above-described methods and components of described systems can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.

[0077] In addition, it should be noted that the functions of the various elements described herein may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor”, “control unit” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included.

[0078] Finally, it should be noted that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the claimed subject-matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0079] Again summarizing, the present subject-matter offers an effective concept to save water consumption (water as a preferred example of non-combustible fluid to be injected) in a water-injection internal combustion engine in transient as well as in steady state driving situations. The reduced water amount is achieved by heating the water to a predefined temperature which improves the spray characteristics and therefore avoids wall wetting. Heating the water directly in the water injector allows for an efficient use of energy since only a small amount of water has to be heated up.

REFERENCE SIGNS LIST

[0080] 1 combustion chamber [0081] 2 piston [0082] 3 connecting rod [0083] 4 intake port [0084] 5 exhaust port [0085] 6 intake valve [0086] 7 exhaust valve [0087] 8 fuel injector [0088] 9 non-combustible fluid/water injector [0089] 10, 10a (water) tank [0090] 11 spark ignition [0091] 12a spark plug [0092] 12b ignition coil [0093] 13 cylinder wall [0094] 14 (water) heater [0095] 15, 15a heat exchanger [0096] 16, 16a (water) pump [0097] 100 cylinder [0098] 200 control unit, control device [0099] 201 (water) pressure and temperature control unit