INTERNAL COMBUSTION ENGINE

Abstract

A Dual-fuel combustion engine, possessing: a control device at least one combustion chamber at least one gas supply device for supplying a gaseous fuel to at least one combustion chamber, and at least one injector for injecting liquid fuel into the at least one combustion chamber, and which injector is controllable through a control device by the use of an actuator triggering signal, for which at least one injector possesses an output opening for the liquid fuel, which is closable by means of a needle (6), and for which the control device regulates through the use of the actuator triggering signal, the opening of the needle (6) in the ballistic region of the needle in a pilot operating mode of the combustion engine
to which end, an algorithm is stored in the control device, which receives, as input values, at least the actuator triggering signal (t) and, using an injector model, calculates the mass of liquid fuel introduced via the output opening of the injector, and which compares the mass calculated by means of the injector model with a required target value (m.sub.d.sup.ref) of the mass of liquid fuel, and on the basis of the result of such comparison, either leaves the actuator triggering signal (t) unchanged or corrects it, and a process for the operation of a combustion engine and of an injector.

Claims

1. A Dual-fuel combustion engine, comprising: a control device; at least one combustion chamber; at least one gas delivery device for delivering a gaseous fuel to at least one combustion chamber; and at least one injector that can be regulated via the control device using an actuator triggering signal, for an injection of liquid fuel into the at least one combustion chamber; wherein the at least one injector comprises an outputopening for a liquid fuel closable by a needle; wherein the control device, via the actuator triggering signal, controls opening of the needle in a ballistic region of the needle in a pilot operating mode of the combustion engine; and wherein an algorithm is stored in the control device, which receives as an input value at least the actuator triggering signal, and calculates a mass of liquid fuel transferred through the output opening of the at least one injector via an injector model, compares the mass calculated using the injector model with a required target value of the mass of liquid fuel, and either leaves it unchanged or corrects the actuator triggering signal, depending on a result of the comparison.

2. The combustion engine of claim 1, wherein the algorithm comprises a preliminary control, which calculates a preliminary control signal for the actuator triggering signal for an injection duration, based on the required target value of the mass of liquid fuel.

3. The combustion engine of claim 1, wherein at least one sensor is operable to measure at least one measurement value of the at least one injector, for which purpose the sensor is or can be brought into signal connection with the control device.

4. The combustion engine of claim 1, wherein the algorithm possesses a feedback loop which, after the actuator triggering signal is calculated by a preliminary control for injection duration and an at least one measurement value, calculates the mass of liquid fuel introduced through the outputopening of the at least one injector by means of the injector model and, if required, corrects by a correction factor the target value calculated by the preliminary control.

5. The combustion engine of claim 1, wherein the algorithm possesses an observer system, which estimates the mass of liquid fuel injected by using the injector model, the actuator triggering signal, and the at least one measurement value.

6. The combustion engine of claim 1, wherein the injector model comprises: pressure progressions in volumes of the at least one injector filled with liquid fuel; mass flow rates between the volumes of the at least one injector filled with liquid fuel; a position of the needle in relation to a needle seat; and dynamics of an actuator of the needle.

7. The combustion engine of claim 1, wherein the at least one injector comprises: an intake accumulator chamber connected with a Common-Rail of the combustion engine; the intake accumulator chamber for liquid fuel connected with the-accumulator chamber; a volume above a needle seat connected with the accumulator chamber; a junction-volume connected on one side with the accumulator chamber and on another side with an outflow duct; the output opening for liquid fuel capable of being closed by means of the needle and connected with the volume above the needle seat; the actuator triggered by an actuator triggering signal for opening the needle; and a control chamber connected on one side with the accumulator chamber and on another side with a connection volume.

8. The combustion engine of claim 1, wherein the at least one measurement value is selected from the following values or a combination thereof: pressure of one Common-Rail of the combustion engine; pressure (PIA) in one input accumulator chamber of the injector; pressure in one control chamber of the injector; and commencement of lift-off of the needle from a needle seat.

9. The combustion engine of claim 1, wherein the control device carries out the algorithm during each combustion cycle, or during selected combustion cycles of the combustion engine and corrects the actuator triggering signal during such combustion cycle, if differences.

10. The combustion engine of claim 1, wherein the control device carries out the algorithm during each combustion cycle or during selected combustion cycles of the combustion engine, and if differences, carries out a correction of the actuator triggering signal for a subsequent combustion cycle.

11. The combustion engine of claim 1, wherein the control device carries out the algorithm during each combustion cycle or during selected combustion cycles of the combustion engine and statically evaluates any differences occurring, and carries out a correction of the actuator triggering signal for a current or for a subsequent combustion cycles based on the static evaluation.

12. A process for operating the Dual-fuel combustion engine of claim 1, wherein the liquid fuel, as a pilot fuel, and gaseous fuel are introduced into the combustion chamber of the combustion engine, with the mass of liquid fuel introduced into the combustion chamber calculated based on the actuator triggering signal of an actuator for the at least one injector of the liquid fuel using an injector model, and the actuator triggering signal corrected upon differences between a target value of the mass of the liquid fuel and the calculated mass.

13. A process for the operation of an injector, comprising: injecting a liquid fuel into a combustion chamber of a combustion engine; introducing a mass of liquid fuel into a combustion chamber by an injector; calculating the mass of liquid fuel introduced into the combustion chamber using an injector model for an actuator triggering signal of an actuator of the injector for the liquid fuel; and correcting the actuator triggering signal if differences between a target value for the mass of liquid fuel and the mass calculated.

Description

[0048] Examples of embodiments of the invention are explained using the figures; these show

[0049] FIG. 1 a first embodiment of the control circuit in accordance with the invention

[0050] FIG. 2 a second embodiment of the control circuit in accordance with the invention

[0051] FIG. 3 a first example of schematic representation of an injector

[0052] FIG. 4 a second example of a schematic representation of an injector

[0053] It should be noted that none of the figures shows the gas feed device for feeding the gaseous fuel into the at least one combustion chamber, except for the schematically represented valves or the corresponding management or control system. These correspond to the state of the art.

[0054] FIG. 1:

[0055] The purpose of the injector control in this embodiment is the control of the actually injected mass of liquid fuel at a target value m.sub.d.sup.ref, by controlling the injection duration t. The regulation strategy is carried out by: [0056] a preliminary control value (FF), which uses a required target value m.sub.d.sup.ref for the mass of liquid fuel to calculate a preliminary control signal .sub.t ff (also referred to below as control command) for the injection duration .sub.t and [0057] a feedback loop (FB), which by using an observer system 7 (State Estimator) takes into account the control command for the injection duration .sub.t and at least one measurement value y (e.g. one of the pressure progressions Pia, Pcc, Pjc, Pac, Psa, occurring in the injector or the commencement of the lift-off of the needle from the needle seat (via the injector model) estimates by means of the injector model the mass flow md of liquid fuel introduced through the output opening of the injector and, where required, corrects the target value .sub.tff calculated by the preliminary control for the injection duration by using a correction value .sub.tfb (which may be negative) so that it becomes the actual duration of the actuator triggering signal t.

[0058] The preliminary control ensures a fast system response, since it triggers the injector with an injection duration t, as if no injector variability existed. The preliminary control uses a calibrated field of injector characteristics (which indicates the current supply duration via the injection mass or volume) or to convert the inverted injector model into the preliminary control command .sub.tff for the injection duration using the target value m.sub.d.sup.ref for the mass of liquid fuel.

[0059] The feedback loop (FB) is used in order to correct any inaccuracies in the preliminary control process (due to manufacturing variability, wear, etc.) which cause injector drift. The feedback loop compares the target value m.sub.d.sup.ref with the estimated injected mass md of liquid fuel and gives as a feedback a correcting control command tfb for the injection duration, if there is any discrepancy between m.sub.d.sup.ref and md. The addition of tff and tfb gives the definitive injection duration t.

[0060] The observer system estimates the injected mass md of liquid fuel depending on the at least one measurement value y and the final injection duration t. The at least one measurement value y can, for example, refer to: common rail pressure Pcr, pressure in the input accumulation chamber Pia, pressure in the control chamber Pcc or the commencement of the lift-off of the needle from the needle seat. The observer system uses a reduced injector model in order to estimate the injected mass md of liquid fuel.

[0061] FIG. 2:

[0062] This figure shows a control system constructed as a single unit (without preliminary control command .sub.dff) in which the actuator triggering signal .sub.t is calculated on the basis of the target value m.sub.d.sup.ref for the injected mass of liquid fuel and on the basis of the parameter .sup.par.sub.mod used in the preliminary control model and estimated by the observer system. Hence an adaptive preliminary control signal is produced, which is modified by the observer system. Therefore in this case, the means of control is not constructed in two components with a preliminary control and a feedback loop that corrects the preliminary control signal.

[0063] FIG. 3 shows a block diagram for a reduced injector model. The injector model consists of a structural model for the injector and a system of equations for describing the dynamic behaviour of the

[0064] structural model. The structural model consists of five modelled volumes: Intake accumulator, accumulator chamber, control chamber, volume above the needle seat (Small Accumulator Chamber),and connection volume (Junction).

[0065] The intake accumulator chamber 1 represents the accumulation of all the volumes between the input choke and the non-return valve. The accumulator chamber 3 represents the combination of all volumes from the non-return valve to the volume above the needle seat. The volume above the needle seat represents a combination of all volumes between the needle seat up to the output opening of the injector. The connection volume 5 represents the combination of all the volumes which connect the volumes of the accumulator chamber 3 and the control chamber 2 with the solenoid valve.

[0066] FIG. 4 shows an injector with an alternative construction, capable of operating without a control chamber, for example, an injector in which the needle is triggered by means of a Piezo element.

[0067] The following system of equations does not refer to the version shown in FIG. 4. The formulation of a suitable system of equations may be produced analogously to the equation system shown below.

[0068] The dynamic behaviour of the structural model is described through the following equation system:

[0069] Pressure Dynamics

[0070] The development through time of the pressure within each of the volumes is calculated on the basis of a combination between the mass conservation equation and the pressure-density characteristic of the liquid fuel. The progression through time of the pressure is determined by:

[00001]$\begin{array}{cc}{\stackrel{.}{p}}_{\mathrm{IA}}=\frac{K_f}{p_{\mathrm{IA}}.Math.V_{\mathrm{IA}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{in}}-{\stackrel{.}{m}}_{\mathrm{aci}}\right)& \mathrm{EQ}..Math.1.1\\ {\stackrel{.}{p}}_{\mathrm{CC}}=\frac{K_f}{{}_{\mathrm{CC}}.Math.V_{\mathrm{CC}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{zd}}-{\stackrel{.}{m}}_{\mathrm{ad}}-{}_{\mathrm{CC}}.Math.{\stackrel{.}{V}}_{\mathrm{CC}}\right)& \mathrm{EQ}..Math.1.2\\ {\stackrel{.}{p}}_{\mathrm{JC}}=\frac{K_f}{{}_{\mathrm{JC}}.Math.V_{\mathrm{JC}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{bd}}-{\stackrel{.}{m}}_{\mathrm{ad}}-{\stackrel{.}{m}}_{\mathrm{sol}}\right)& \mathrm{EQ}..Math.1.3\\ {\stackrel{.}{p}}_{A.Math..Math.C}=\frac{K_f}{{}_{A.Math..Math.C}.Math.V_{A.Math..Math.C}}.Math.\left({\stackrel{.}{m}}_{\mathrm{aci}}-{\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{bd}}-{\stackrel{.}{m}}_{\mathrm{zd}}-{}_{A.Math..Math.C}.Math.{\stackrel{.}{V}}_{\mathrm{AC}}\right)& \mathrm{EQ}..Math.1.4\\ {\stackrel{.}{p}}_{\mathrm{SA}}=\frac{K_f}{{}_{\mathrm{SA}}.Math.V_{\mathrm{SA}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{inj}}-{}_{\mathrm{SA}}.Math.{\stackrel{.}{V}}_{\mathrm{SA}}\right)& \mathrm{EQ}..Math.1.5\end{array}$

[0071] Symbols Used in the Formulae [0072] P.sub.IA: Pressure in the intake accumulator chamber 1 in bar [0073] P.sub.CC: Pressure in the control chamber 2 in bar [0074] P.sub.JC: Pressure in the junction volume 5 in bar [0075] P.sub.AC: Pressure in the accumulator chamber 3 in bar [0076] P.sub.SA: Pressure in the small accumulator chamber 4 in bar [0077] P.sub.IA: Diesel mass density within the intake accumulator chamber 1 in kg/m.sup.3 [0078] P.sub.CC: Diesel mass density within the control chamber 2 in kg/m/.sup.3 [0079] P.sub.JC: Diesel mass density within the junction volume 5 in kg/m.sup.3 [0080] P.sub.AC: Diesel mass density within the accumulation chamber 1 in kg/m.sup.3 [0081] P.sub.SA: Diesel mass density within the small accumulator chamber 4 in kg/.sup.3 [0082] K.sub.f: Compression modulus of the Diesel fuel in bar

[0083] Needle Dynamics

[0084] The needle position is calculated by means of the following movement equation:

[00002]$\begin{array}{cc}\stackrel{\mathrm{.Math.}}{Z}=\{\begin{array}{c}0.Math..Math.\mathrm{if}.Math..Math.F_{\mathrm{hyd}}{F}_{\mathrm{pre}}\\ \frac{1}{m}.Math.\left(F_{\mathrm{hyd}}-\mathrm{Kz}-B.Math.\hat{z}-F_{\mathrm{pre}}\right).Math..Math.\mathrm{if}.Math..Math.F_{\mathrm{hyd}}>F_{\mathrm{pre}}\end{array}& \mathrm{EQ}..Math.2.1\\ F_{\mathrm{hyd}}=p_{A.Math..Math.C}.Math.A_{A.Math..Math.C}+p_{\mathrm{SA}}.Math.A_{\mathrm{SA}}-p_{\mathrm{CC}}.Math.A_{\mathrm{CC}}& \mathrm{EQ}..Math.2.2\\ 0z{z}_{\max }& \mathrm{EQ}..Math.2.3\end{array}$

[0085] Symbols used in the formulae: [0086] z: Needle position in metres (m) [0087] z.sub.max: Maximum displacement of the needle 6 in m [0088] k: Stiffness of spring in N/m [0089] B: Spring damping co-efficient in N.Math.s/m [0090] F.sub.pre: Spring pretension in N [0091] A.sub.ac: Hydraulic effective area in the accumulator chamber 3 in m.sup.2 [0092] A.sub.sa: Hydraulic effective area in the small accumulator chamber 4 in m.sup.2 [0093] A.sub.cc: Hydraulic effective area in the control chamber 2 in m.sup.2

[0094] Dynamics of the Solenoid Valve

[0095] The solenoid valve is modelled through a first-order transfer function, which converts the valve opening command into a valve position. This is provided by:

[00003]$\stackrel{u_{\mathrm{sol}}^{\mathrm{cmd}}}{.fwdarw.}.Math.\frac{z_{\mathrm{sol}}^{\max }}{{}_{\mathrm{sol}}.Math.s+1}.Math.\stackrel{z_{\mathrm{sol}}}{.fwdarw.}$

[0096] The transient system behaviour is characterised by the time constant t.sub.sol

[0097] and the position of the needle 6 at maximum valve opening is given by Z.sup.max/.sub.sol1

[0098] A piezo-electric operation is also possible instead of a solenoid valve.

[0099] Mass Flow Rates

[0100] The mass flow rate through each valve is calculated using the standard choked flow equation for liquids, which is:

[00004]$\begin{array}{cc}\text{?}& \mathrm{EQ}..Math.3.1\\ & \mathrm{EQ}..Math.3.2\\ & \mathrm{EQ}..Math.3.3\\ & \mathrm{EQ}..Math.3.4\\ & \mathrm{EQ}..Math.3.5\\ & \mathrm{EQ}..Math.3.6\\ & \mathrm{EQ}..Math.3.7\\ & \mathrm{EQ}..Math.3.8\\ .Math..Math.\text{?}.Math.\text{indicates text missing or illegible when filed}.Math.& \mathrm{EQ}..Math.3.9\end{array}$

[0101] Formula symbols used: [0102] m.sub.n: Mass flow density through the input choke in kg/s [0103] m.sub.bd: Mass flow rate via the bypass valve between accumulator chamber 3 and junction volume 5 in kg/s [0104] m.sub.ad: Mass flow rate via feeder valve at the entry point of the control chamber 2 in kg/s [0105] m.sub.ad: Mass flow rate via the discharge valve from control chamber 2 in kg/s [0106] m.sub.oll: Mass flow rate via the solenoid valve in kg/s [0107] m.sub.all: Mass flow rate via the entry point into the accumulator chamber 3 in kg/s [0108] m.sub.an: Mass flow rate via the needle seat in kg/s [0109] m.sub.in: Mass flow rate via the injector jet in kg/s

[0110] On the basis of the injector model formulated above, the professional will obtain the estimated value m.sub.d by means of the observer system in a manner which is in principle already known (see e.g. B. Iserman, Rolf, Digitale Regelsysteme [Digital control systems], Springer Verlag Heidelberg 1977, Chapter 22.3.2, Page 379 et seq. or F. Castillo et al. Simultaneous Air Fraction and Low-Pressure EGR Mass Flow Rate Estimation for Diesel Engines, IFAC Joint conference SSSC-

[0111] 5th Symposium on System Structure and Control, Grenoble, France 2013).

[0112] By using the above system of equations, it is possible to construct the so-called observer equations, preferably making use of an observer system which is known in principle, of the sliding mode observer type, by adding to the equations in the injector model the so-called observer law. For a sliding mode observer, one obtains the observer law by calculating a hypersurface using the at least one measurement signal and the value that results from the observer equations. By squaring the equation for the hypersurface, one obtains a generalised Lyapunov equation (generalised energy equation). This is a functional equation. The observer law represents that function which is minimised by the functional equation. This can be determined by variation techniques, which are known in principle, or numerically. This process is carried out within a combustion cycle for each step in time (depending on the time resolution of the control system).

[0113] Depending on the application, the result is the estimated injected mass of liquid fuel, the position of needle 6 or one of the pressures in one of the volumes of the injector.