DE102018217759A1 - Procedure for the determination of water in fuel - Google Patents

Abstract

The invention relates to a method for determining water in fuel, at least one fuel injector (2, 3) being set up to inject the fuel into a combustion chamber (4) of an internal combustion engine (1), and wherein water contained in the fuel is based on a Switching behavior of the fuel injector (2, 3) is determined.

Description

State of the art

The present invention relates to a method for determining water in a fuel and a method for injecting a fuel-water mixture into an internal combustion engine. Furthermore, the invention relates to a control device and / or a control device for carrying out the method and an internal combustion engine, in particular an Otto engine, which comprises the control device and / or control device.

Due to increasing requirements for reduced carbon dioxide emissions, internal combustion engines are increasingly being optimized with regard to fuel consumption. However, known internal combustion engines cannot be operated optimally in terms of consumption at operating points with a high load, since the operation is limited by knocking tendency and high exhaust gas temperatures. A possible measure to reduce the tendency to knock and to lower the exhaust gas temperatures is the injection of water. Separate water injection systems are usually provided to enable water injection. For example, Water injection systems for internal combustion engines are known, in which water is injected into the intake manifold for cooling the mixture. Alternatively, direct water injection is also possible, water being added to the fuel upstream of the high-pressure pump. The fuel-water emulsion is injected directly into the combustion chamber.

Disclosure of the invention

The method according to the invention for determining water in fuel with the features of claim 1 is characterized in that the presence of water in the fuel is determined in a simple manner directly at an injection point of the fuel. This is achieved according to the invention in that at least one fuel injector is provided, which is set up to inject the fuel into a combustion chamber or a suction area of an internal combustion engine. Water contained in the fuel is determined based on a switching behavior of the fuel injector. In the following, both pure, water-free fuel and a fuel-water mixture, which contains pure fuel and water in liquid form, are regarded as fuel. Since the composition of the fuel significantly influences the switching behavior of the fuel injector, the composition can be determined particularly favorably by determining the switching behavior of the fuel injector. To determine the switching behavior of the fuel injector, electrical quantities of the fuel injector are preferably analyzed. For example, the switching behavior of the fuel injector can be determined by means of a voltage and / or a current. It is particularly advantageous if water contained in the fuel is determined based on a change in the switching behavior of the fuel injector. Such a change is particularly easy to determine, for example by analyzing changes in the electrical quantities of the fuel injector during opening and / or closing. The determination can be carried out with the already existing components of the internal combustion engine and no further components, such as sensors, are necessary.

With the method according to the invention, water contained in the fuel can be determined in a particularly simple manner. The composition of the fuel, which significantly influences optimal and low-emission combustion in the combustion chamber, can be determined very precisely at the injection point.

The dependent claims contain preferred developments of the invention.

To determine the switching behavior, an opening duration and / or a closing duration of the fuel injector is preferably determined at a certain stroke. It is particularly expedient if the opening duration and / or the closing duration is determined during a full stroke of the fuel injector. It would also be possible to determine the opening time and / or the closing time for a partial stroke, for example a 50% stroke, of the fuel injector. Since the water increases in the amount of water in the fuel, there are increased sticking effects on the fuel injector, for example on a needle or on the lower and upper stop surfaces of the fuel injector, this results in an increase in the opening time and / or the closing time. When the duration of the opening and / or the duration of the opening is determined, water which is contained in the fuel can thus be determined in a particularly simple manner in reverse.

An opening delay time and / or a closing delay time of the fuel injector is particularly preferably determined to determine the switching behavior. The opening delay time and the closing delay time are considered to be the time which elapses from the receipt of the signal for opening or closing on the fuel injector until the actual start of the mechanical opening or closing process, for example the commencement of the movement of a needle of the fuel injector. Similar to the description in the previous section, water contained in the fuel influences the fuel mainly due to adhesive effects on the fuel injector Opening delay time and the closing delay time of the fuel injector. It is therefore also very easy to infer water contained in the fuel from a determination of the opening delay time and / or closing delay time.

It is particularly advantageous if a viscosity of the fuel is determined based on the switching behavior of the fuel injector. Based on the determined viscosity of the fuel, it can then be determined whether the fuel contains water. Since the presence of water in the fuel has a particularly significant influence on the viscosity of the fuel, and the viscosity of the fuel also significantly influences the switching behavior of the fuel injector, determining the viscosity offers a particularly simple and advantageous way of determining the water in the fuel .

A value of a water content in the fuel is particularly preferably determined based on the viscosity of the fuel. This means that after determining the viscosity of the fuel, the percentage of water in the fuel is determined. As a result, the fuel composition on the fuel injector can be determined particularly precisely.

Furthermore, the invention leads to a method for injecting a fuel-water mixture into at least one combustion chamber or at least one suction area of an internal combustion engine. Water is mixed into the fuel, in particular before the fuel-water mixture is injected into the combustion chamber or the suction area in order to form the fuel-water mixture. As a result, water can also be injected immediately through the fuel injector at a desired water injection time. Water present in the fuel-water mixture is determined using the method according to the invention.

The water present in the fuel-water mixture is preferably determined specifically for the injector and in particular for the combustion chamber, that is to say separately for each fuel injector or combustion chamber of the internal combustion engine. This means that the method is carried out several times and for each fuel injector or combustion chamber individually. This is particularly advantageous if the fuel is supplied at least partially asymmetrically to a plurality of fuel injectors, for example via a central rail, and if the water is added centrally at one point. In this case, there are routes of different lengths from the mixing point to the fuel injectors. As a result, the fuel-water mixture arrives at different fuel injectors at different times after the water admixture has been switched on. Because the water in the fuel-water mixture is determined separately for each fuel injector or combustion chamber, a particularly precise determination of the fuel composition for each individual combustion chamber is possible.

It is particularly advantageous if a mixing time and a switch-on time are determined. The time of admixing is the time from which water is added to the fuel. The switch-on time period is the time which elapses from the mixing point in time to a water availability point in time at which the fuel-water mixture is present at the fuel injector. Additionally or alternatively, a switch-off time and a switch-off time period are determined analogously. At the time of switching off, the admixture of water and fuel is switched off. The switch-off time here corresponds to the time between the switch-off time and a water absence time, at which water-free fuel is present on the fuel injector after the switch-off. In addition or as an alternative to this, an admixing period during which water is contained in the fuel at the fuel injector is also determined. This means that both the start and end of the water addition and the effective duration of the water addition can be determined. In addition, the actual time at which the admixed water arrives at the fuel injector or at which no more water arrives at the fuel injector can be determined. This enables a particularly detailed determination of the fuel composition at each individual fuel injector and accordingly enables exact water injection.

Furthermore, it is advantageous if an engine control of the internal combustion engine is adapted based on the presence of water in the fuel. When the water in the fuel is determined specifically for the combustion chamber, the engine control is also adapted to suit the combustion chamber. It is particularly favorable if an ignition angle and / or a control of an intake valve and / or an exhaust valve of the internal combustion engine is adapted. A particularly high efficiency of the internal combustion engine can be made possible by a corresponding adaptation of the engine control.

The invention further relates to a control device and / or a regulating device which is set up to carry out the method according to the invention.

The control device and / or regulating device is preferably set up, based on the presence of water in the fuel-water system. Mixture to adapt an engine control, in particular an ignition angle, and / or a control of an intake valve and / or an exhaust valve, the internal combustion engine, and / or an amount of water mixed with the fuel. The engine control of the internal combustion engine can thus be optimally adapted as required and depending on the fuel composition in order to ensure the most efficient possible operation of the internal combustion engine.

Furthermore, the invention relates to an internal combustion engine, comprising the control device and / or regulating device. The internal combustion engine is preferably an Otto engine.

Figure list

• 1 eine vereinfachte schematische Ansicht einer Brennkraftmaschine mit einer Regelvorrichtung zur Durchführung eines Verfahrens gemäß einem bevorzugten Ausführungsbeispiel der Erfindung,
• 2 einen Zusammenhang einer Schließzeit eines Kraftstoff-Injektors mit einer Viskosität des Kraftstoffs,
• 3 eine Zusammenhang einer Öffnungsverzugszeit eines Kraftstoff-Injektors mit der Viskosität des Kraftstoffs,
• 4 einen Zusammenhang eines Wasseranteils des Kraftstoffs mit der Viskosität des Kraftstoffs, und
• 5 einen Vergleich von Schließzeiten zweier Kraftstoff-Injektoren der Brennkraftmaschine der 1.

The invention is described below on the basis of exemplary embodiments in conjunction with the figures. In the figures, functionally identical components are identified with the same reference numerals. It shows:

• 1 2 shows a simplified schematic view of an internal combustion engine with a control device for carrying out a method according to a preferred exemplary embodiment of the invention,
• 2nd a relationship between a closing time of a fuel injector and a viscosity of the fuel,
• 3rd a relationship between an opening delay time of a fuel injector and the viscosity of the fuel,
• 4th a relationship between the water content of the fuel and the viscosity of the fuel, and
• 5 a comparison of the closing times of two fuel injectors of the internal combustion engine 1 .

Preferred embodiment of the invention

The 1 shows an internal combustion engine 1 with a control device 11 which is set up to carry out a method for determining water contained in a fuel according to a preferred embodiment of the invention.

The internal combustion engine 1 includes a first fuel injector 2nd and a second fuel injector 3rd Both of which are set up to fuel each in a combustion chamber 4th the internal combustion engine 1 to inject.

In the combustion chambers 4th fuel can be injected in the form of anhydrous fuel or a fuel-water mixture. The fuel is the two fuel injectors 2nd , 3rd over a rail 5 fed. A supply of fuel to the rail 5 takes place by means of a high pressure pump 6 . Via a supply line 7 is the high pressure pump 6 with a fuel tank 8th , which contains the anhydrous fuel.

The supply line 7 has a mixing point 15 on which an admixture of water to the anhydrous fuel is possible to form the fuel-water mixture. This can be done using water from a water tank 10th by means of a water pump 9 removed and the water-free fuel at the mixing point 15 be added. At the mixing point 15 both the water and the anhydrous fuel are in liquid form.

The admixture of the water and thus the water content in the fuel is controlled by means of a control device 11 . The control device 11 is a control unit of the internal combustion engine 1 . The control device 11 is set up, the high pressure pump 6 who have favourited Water Pump 9 , the first fuel injector 2nd and the second fuel injector 3rd to regulate. In addition, the motor control is regulated by the control device 11 . The regulation takes place on the basis of a determined value of a water portion of the fuel in the injection area of the internal combustion engine 1 , that is based on a water content of the fuel in the first fuel injector 2nd and on the second fuel injector 3rd .

The control device is used to determine the water content of the fuel 11 set up, each a switching behavior of the first fuel injector 2nd and the second fuel injector 3rd to determine. This is done by analyzing the current and voltage, each on the first fuel injector 2nd and on the second fuel injector 3rd issue. The control device determines from current and voltage 11 one opening period, one closing period T2 , an opening delay T1V and a closing delay time of the two fuel injectors 2nd , 3rd . From these determined variables, i.e. based on the switching behavior of the fuel injectors 2nd , 3rd , determines the control device 11 then a viscosity of the fuel. On the basis of the viscosity determined, a value of the water content of the fuel is also determined.

The more precise relationship between the switching behavior of the fuel injectors 2nd , 3rd and the water content of the fuel to be injected is subsequently based on the 2nd to 4th explained in more detail. For the sake of simplicity, the description is given by way of example only in relation to the first fuel injector 2nd .

The 2nd shows a closing time T2 of the first fuel injector 2nd depending on the viscosity V of fuel. Like in the 2nd recognizing the closing time increases T2 with increasing viscosity V . The closing time T2 is defined as the period of time which is necessary for a complete closing with a full stroke of the first fuel injector 2nd .

The 3rd shows an opening delay time T1V of the first fuel injector 2nd depending on the viscosity V of fuel. Similar to that in the 2nd shown closing time T2 , the opening delay time also increases T1V with increasing viscosity V . The opening delay time is the time from the receipt of the signal for opening the first fuel injector to the actual start of the mechanical opening process of the first fuel injector 2nd passes.

The 4th shows a relationship between the viscosity V of the fuel and a percentage of water W of fuel. Like in the 4th recognizes the viscosity V with increasing water content W to. This means that the more water there is in the fuel, the higher the viscosity of the fuel. With regard to the 2nd and 3rd it follows that an increasing proportion of water W in the fuel an increase in the closing time T2 as well as an increase in the opening delay time T1V causes.

Furthermore, in the 1 realizing that the first fuel injector 2nd and the second fuel injector 3rd with respect to an inflow direction 20th the fuel into the rail 5 are arranged side by side. Thus lie between the admixing point 15 and the two fuel injectors 2nd , 3rd paths of different lengths. A first path L2 from the mixing point 15 up to the first fuel injector 2nd is shorter than a second path length L3 to the second fuel injector 3rd . This means that, for example, after the addition of water to the fuel has been switched on, the water at different times on the two fuel injectors 2nd , 3rd arrives. This fact is described below with the help of 5 explained in more detail.

The 5 shows a comparison of the closing times T22 , T23 of the first fuel injector 2nd and the second fuel injector 3rd the internal combustion engine 1 of the 1 . There is a first closing period at the top T22 of the first fuel injector 2nd and a second closing time below T23 of the second fuel injector 3rd each over time T shown.

From an admixing point A water is added to the fuel at the mixing point 15 (see. 1 ). After a first switch-on period TE2 is the water at a first water availability time B2 on the first fuel injector 2nd arrived. As described above, this is based on the switching behavior of the first fuel injector 2nd determined. Through the related to the 2nd and 4th described dependency of the closing time T2 from the fuel composition, the closing times increase T22 , T23 once the water is at the fuel injectors 2nd , 3rd has arrived. Because of the compared to the first path length L2 larger second path length L3 is a second switch-on period TE3 , after which the water at a second water availability time B3 on the second fuel injector 3rd arrives longer than the first switch-on time TE2 .

As also in the 5 shown, the admixture of water to the fuel at the admixing point is shown at a switch-off time C. 15 switched off. Analogous to the switch-on times TE2 , TE3 when switching on the water admixture, switch-off times are TA2 , TA3 defines which each from the switch-off time C to a water absence time D2 , D3 on what anhydrous fuel on the fuel injectors 2nd , 3rd exists, are defined. The second switch-off period is also included TA3 due to the larger second path length L3 greater than the first shutdown period TA2 .

From the difference in water absence times D2 , D3 and the water availability times B2 , B3 there is an admixing time in each case TZ2 , TZ3 during which the water on the fuel injectors 2nd , 3rd is present.

By knowing the water content W of the fuel and the precise times at which water is contained in the fuel, an optimal adaptation of the engine control can be carried out in an injector-specific or combustion chamber-specific manner in order to achieve the most efficient possible operation of the internal combustion engine. In addition, based on the determined points in time, a corresponding regulation by means of the regulating device could 11 be made to increase opening delays caused by water T1 V and / or to compensate for delayed closing times. The switch-on times could also be the result of the regulation TE2 , TE3 and / or the shutdown periods TA2 , TA3 be compensated. In particular, the admixing times can also be used TZ2 and TZ3 be adjusted as possible so that they are as possible for each fuel injector 2nd , 3rd the internal combustion engine 1 are the same length.

Claims (12)

Method for determining water in fuel, at least one fuel injector (2, 3) being set up to inject the fuel into a combustion chamber (4) and / or a suction area of an internal combustion engine (1), and wherein water contained in the fuel is based on a switching behavior of the fuel injector (2, 3) is determined. Procedure according to Claim 1 , In order to determine the switching behavior, an opening duration and / or a closing duration (T2) of the fuel injector (2, 3) is determined as a function of a stroke, in particular during a full stroke, of the fuel injector (2, 3). Method according to one of the preceding claims, wherein an opening delay time (T1V) and / or a closing delay time of the fuel injector is determined to determine the switching behavior. Method according to one of the preceding claims, wherein a viscosity (V) of the fuel to be injected is determined based on the switching behavior of the fuel injector (2, 3), and wherein based on the viscosity (V) of the fuel it is determined whether water in the fuel is included. Procedure according to Claim 4 , wherein a value for a water content (W) in the fuel is determined based on the viscosity (V) of the fuel. Method for injecting a fuel-water mixture into at least one combustion chamber (4) and / or at least one suction area of an internal combustion engine (1), water being added to the fuel to form the fuel-water mixture and in the fuel -Water mixture existing water is determined with the method according to any one of the preceding claims. Procedure according to Claim 6 The water in the fuel-water mixture is determined separately for each fuel injector (2, 3) of the internal combustion engine (1). Procedure according to one of the Claims 6 or 7 , - a mixing time (A), from which the water is added to the fuel, and a switch-on time (TE) from the mixing time (A) to a water availability time (B), at which the fuel-water Mixture present on the fuel injector (2, 3) is determined, and / or - wherein a switch-off time (C) at which an admixture of water to the fuel is switched off and a switch-off time period (TA) from the switch-off time (C ) up to an absence of water (D), at which anhydrous fuel is present on the fuel injector (2, 3), and / or - with an admixing time (TZ) during which on the fuel injector (2, 3 ) Water is contained in the fuel is determined. Method according to one of the preceding claims, an engine control, in particular an ignition angle, and / or a control of an intake valve and / or an exhaust valve being adapted to the internal combustion engine (1) based on the presence of water in the fuel. Control device and / or regulating device (11) which is set up to carry out the method according to one of the preceding claims. Control device and / or regulating device (11) according to Claim 10 , which is set up, based on the presence of water in the fuel-water mixture, an engine control, in particular an ignition angle, and / or a control of an intake valve and / or an exhaust valve, the internal combustion engine (1), and / or a fuel adjust the admixed amount of water. Internal combustion engine (1), comprising a control device and / or regulating device (11) according to one of the Claims 10 or 11 .

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