Method and device for operating a gas internal combustion engine

Abstract

A gas internal combustion engine, having a gas mixer, an intake section and an engine to which a fuel mixture having a charging mixture is fed. The engine is operated in the gas mode with gas as the fuel in the charging mixture. By an input mixture portion, from an earlier mixture state, of a gas/air mixture, an output mixture portion, from a later mixture state, of the gas/air mixture is determined by an intake section model. The output mixture portion is determined at an engine feed, the input mixture portion is determined over a number of intermediate states of the mixture portion in a number of assigned volumes of the intake section. The intake mixture portion of a gas/air mixture is determined at the gas mixer, and an air stream and/or gas stream is set at the gas mixer in accordance with the input mixture portion.

Claims

1. A method for operating a gas internal combustion engine having a gas mixer, an intake path and an engine having a number of cylinders, the method comprising the steps of: supplying the engine with a gaseous fuel mixture comprising a charge mixture and operating the engine in gas operation with gas as fuel in the charge mixture; determining an output mixture fraction, assigned to a later mixture state, of the fuel gas-air mixture by an input mixture fraction, assigned to at least one earlier mixture state, of a fuel gas-air mixture, wherein the determining takes place by an intake path model serving as a basis for a computational model for the intake path, wherein the output mixture fraction of the fuel gas-air mixture is determined at an engine supply; determining the input mixture fraction from the output mixture fraction via a number of intermediate states of the mixture fraction in a number of assigned volumes of the intake path in real-time simultaneous with operation of the engine, wherein the input mixture fraction of a fuel gas-air mixture is determined at the gas mixer and an air flow and/or a fuel gas flow at the gas mixer is set as a function of the input mixture fraction.

2. The method as claimed in claim 1, wherein the input mixture fraction of a gas-air mixture is determined at an outlet of the gas mixer and/or the output mixture fraction of a gas-air mixture is determined at a cylinder or a cylinder inlet of the engine or a receiver.

3. The method as claimed in claim 1, wherein determining a mixture fraction comprises: determining a mixture mass flow by a throughflow equation for a volume of the intake path, wherein a mixture mass flow is assigned to the input mixture fraction at the gas mixer and/or a mixture mass flow at an engine supply is assigned to the output mixture fraction; and/or determining a mixture state includes at least determining a temperature and/or a state pressure of the mixture fraction for an assigned volume of the intake path by a thermodynamic state equation for real or ideal gases in the assigned volume.

4. The method as claimed in claim 3, wherein the mixture fraction is determined in the assigned volume of the intake path for a number of theoretical computational volumes of the intake path and/or for a number of real housing volumes of the intake path, wherein the number of intermediate states of the mixture fraction in the intake path is assigned to at least one large volume of the intake path.

5. The method as claimed in claim 4, wherein a number of large volumes of the intake path comprises at least one component volume of the intake path chosen from the group consisting of: at least one receiver volume, at least one cylinder volume in an engine block, at least one intercooler volume, and at least one compressor volume.

6. The method as claimed in claim 1, wherein a combustion air ratio is assigned to the input mixture fraction, wherein a gas metering unit of the gas mixer is controlled by a stoichiometric air requirement and/or by the combustion air ratio.

7. The method as claimed in claim 1, wherein a state pressure is defined as a receiver pressure in a receiver volume upstream of a cylinder of the engine, which is arranged upstream of the cylinder and is arranged downstream of a forced-induction unit and/or of a bypass path.

8. The method as claimed in claim 1, wherein a state pressure is determined virtually based on a computational model of the intake path comprising at least one computational volume of a receiver volume and/or of an intercooler.

9. The method as claimed in claim 1, wherein the number of at least one large volume(s) of the intake path comprises at least one component volume of the intake path chosen from the group consisting of: at least one compressor bypass volume; and at least one intake path volume.

10. The method as claimed in claim 9, wherein the compressor bypass volume is at a bypass pipe section and/or a compressor bypass flap, and the intake path volume is at an intake pipe section and/or at an engine throttle flap and/or inlet throttle flap.

11. The method as claimed in claim 1, wherein a mixture mass flow is determined at a throttle, wherein a throughflow of a return flow and/or of a forced-induction flow is determined by a throughflow equation for compressible media at an ideal or real nozzle assuming a flow of ideal or real gases which is frictionless or is subject to friction.

12. The method as claimed in claim 1, wherein the gas operation is a spark-ignition gas operation.

13. An internal combustion engine designed as a gas internal combustion engine, comprising: a gas mixer; a gaseous fuel intake path; an engine having a number of cylinders and a receiver volume arranged upstream of the cylinders; a forced-induction unit for the fuel intake path; a bypass path for the fuel intake path for bypassing the forced-induction unit, wherein the engine is operable in gas operation with gas as fuel with a supplied fuel mixture comprising a charge mixture; and a control system configured: to determine an output mixture fraction, assigned to a later mixture state, of the fuel gas-air mixture by an input mixture fraction, assigned to at least one earlier mixture state, of a fuel gas-air mixture, to determine the input mixture fraction in the earlier mixture state via the output mixture fraction in the later mixture state by an intake path model serving as a basis for a computational model for the intake path, to determine the output mixture fraction of the fuel gas-air mixture at an engine supply, and to determine the input mixture fraction from the mixture state of the output mixture fraction via a number of intermediate states of the mixture fraction, in a number of assigned volumes of the intake path in real-time simultaneous with operation of the engine, wherein the input mixture fraction of a fuel gas-air mixture is determined at the gas mixer and an air flow and/or a fuel gas flow is set at the gas mixer as a function of the input mixture fraction.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 a map of a gas internal combustion engine having a gas mixer and an intake path with forced-induction by means of a turbocharger and an intercooler, and having an engine with a number of cylinders downstream of a receiver volume, wherein the forced-induction unit can be bypassed by means of a bypass paththe gas internal combustion engine is configured for spark-ignition gas operation; in an alternative, shown in dotted lines, the gas internal combustion engine can also be configured as a gas-diesel internal combustion engine and can be operated, both in pure diesel operation and in mixed operation or in pure gas operation (e.g. as ignition-jet operation, with injection of an ignition mixture in the form of diesel), wherein the injection system is designed in the form of a common rail system (shown in dotted lines);

(2) FIG. 2 a flow chart of a preferred embodiment of a method for determining, in the context of a simultaneous real-time determining of an input mixture fraction assigned to an earlier mixing state of a gas-air mixture by means of an output mixture fraction assigned to a later mixture state of a gas-air mixture, wherein the input mixture fraction of the gas-air mixture is determined at the gas mixer and an air flow and/or a gas flow is set at the gas mixer as a function of the input mixture fraction;

(3) FIG. 3 a schematized representation of a preferred embodiment of a controller structure for dual-fuel operation, wherein the input mixture fraction of a gas-air mixture of the gas mixer is determined from the output mixture fraction of a gas-air mixture supplied to the engine via a number of intermediate states of the mixture fraction in the intake path by means of the intake path model.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a gas internal combustion engine 100, having an engine 10 and an intake system with a branched intake path 30. In the intake path there are arranged, inter alia, a gas mixer 40 and, to form a forced-induction unit, a turbocharger 50 and an intercooler 60, in this case in the form of a charge air cooler, and a bypass 70.

(5) In the present case, the engine is embodied with sixteen cylinders, as a V-engine with eight cylinders Ai, i=1 . . . 8 on an A side and eight cylinders Bi, i=1 . . . 8 on a B side; this type of cylinder arrangement and number of cylinders is represented in the present case merely by way of example. In particular for large-engine applications, other suitable engine configurations comprise ten, twelve, twenty, twenty-four or twenty-eight cylinders, or a different number of cylinders.

(6) In the case of an alternative or additional configuration as a dual-fuel internal combustion engine, the internal combustion engine also has an injection system 20 (shown in dotted lines) which in the present case is formed as a common rail system with a common rail 21 from which there branch off a number of injection lines 22each having an injector 23 and an individual reservoir 24 arranged upstream of the injectoreach for one cylinder Ai, Bi, i=1 . . . 8 of the engine 10. The injection system 20 is designed to meter liquid fuel such as diesel or a different liquefied or liquid fuel, in order to inject the latter in diesel operation as liquid fuel or in gas operation or ignition-jet operation as ignition jet, in each case at the beginning of a working cycle of a cylinder Ai, Bi; this at very high injection pressures. Accordingly, the engine 10 also has in this variant a common rail injection system 20 for a liquid fuel, here in particular diesel fuel, and a forced-induction unit 50 with an intercooler 60 and with a bypass 70 for bypassing the forced-induction unit 50 and the intercooler 60.

(7) With further reference to the essential part of the embodiment, shown in solid lines, the gas mixer 40, connected to the intake path 30 at the inlet-side end of the intake system, draws in charge air LL from the environment and mixes it with combustion gas BG. The charge mixture, in gas operation also termed combustion gas mixturein the following also mixture G for shortwith mass throughflow m()_G (for the sake of clarity, () is represented in the drawing as a dot above the mass m or other variable) and at intake pressure p1 and at intake temperature T1, which essentially corresponds to the ambient temperature, is fed via a compressor path 32 to a compressor 51 of the turbocharger 50 where it is compressed to a compression pressure p2 at a compression temperature T2. The compressor 51 is driven by a turbine 52 and is mounted with the latter on a common charger axis 53; the turbine 52 of the exhaust-gas tract 90 is in turn driven by the exhaust gas AG, leaving the engine 10, in the exhaust-gas tract 90. The mass flow m()_G of the mixture G, heated to the compression temperature T2 as a consequence of the compression, is fed to a cooling path 31 of the intake path 30 where it is introduced into an intercooler 60 via a cooler structure 61; in the heat exchanger volume 62, represented symbolically here, there takes place an exchange of heat with a coolant in the cooler structure 61, such that the mixture G is cooled. The combustion gas mixture leaves the heat exchanger volume of variable V3 in cooled form, at a charge temperature T3 and a charge pressure p3, in the direction of a charge path 33 for feeding the mixture G to the engine 10.

(8) In an intake path model, the state of the mixture G upstream of the compressor 51 by comparison is indicated generally by means of the state variables for pressure and temperature, in this case intake temperature T1 and intake pressure p1 upstream of the compressor 51, or as the case may be downstream of the compressor 51 at increased compression pressure p2 and increased compression temperature T2 with the state variables p2, T2 downstream of the compressor 51, and is described by means of a suitable compressor model; this may be according to a gas state equation such as for an ideal or real gas. As large volumes of the intake path 30 according to the concept of the invention, particular importance is attached to the following components of the heat exchanger 60 and of the receiver 80, such as for example assigned to a manifold and/or a collection path, such that there is assigned to these and to the wider space of the intake path, for modeling the further gas states, a heat exchanger volume V3 or a receiver volume V5 in the intake path model. Accordingly, the combustion gas mixture G in the heat exchanger volume V3 adopts the state variables p3, T3, this as a consequence of the cooling and of an increase in volume with decreasing charge pressure and charge temperature p3, T3.

(9) The state of the mixture G in the bypass 70 is in principle also determined as a function of the state variables p1, T1 at the inlet to, or p3, T3 at the outlet of the bypass 70, or vice versa in the case of recirculation flow through the bypass 70; i.e. a bypass gas mixture G_BP in the bypass path 71 of the bypass 70 establishes itself depending on the prevailing pressure ratios and on the setting of the compressor bypass throttle 72in this case according to the setting angle VBP of the compressor bypass flap. A bypass path 71 can in particular serve for re-circulating excess mixture G upstream of the compressor 51, in order to again supply this, re-compressed, for combustion in the cylinders Ai, Bi of the engine 10.

(10) Before the gas mixture G in the state p3, T3 is fed to the engine 10, it is fed to the receiver 80, changing pressure and temperature in accordance with a mass flow m()_DK fed into the receiver volume 81 via the engine throttle 82and in accordance with the receiver volume V5 at a receiver pressure p5 and a receiver temperature T5. In the present case, a first and a second receiver volume 81.B, 81.A are respectively assigned to a B side and to an A side of the engine 10, i.e. these are arranged upstream of the cylinders Ai, Bi and downstream of the first and second charge path 33.B, 33.A of the B side and A side and downstream of the heat exchanger volume 62. The engine throttle 82 is formed in the present case by a first and a second engine throttle flap 82.B, 82.A, each of which is assigned to the first and second receiver volume 81.B, 81.A accordingly, wherein the first and second engine throttle flaps 82.B, 82.A can be set independently of one another; in the following, these are referred towhere it is simpler to do sotogether as the engine throttle 82. The receiver volume 81 is to be understood as the sum of the first and second receiver volumes 81.A and 81.B. In the receiver volume 81, the mixture G adopts the gas states labeled p5 and T5 as a consequence of the increase in volume and as a function of the setting DK of the engine throttle flaps 82.A, 82.B in the volume V5 of the receiver volume 81; this in dependence on the B-side or A-side mass throughflow m()_DK, B or m()_DK, A depending on the setting of the engine throttle flaps 82.B and 82.A.

(11) The states of the gas mixture G, labeled pi, Ti, i=1,2 or Vj, pj, Tj, j=3,5, are determined in the case of this embodiment essentially in the regions as defined by the compressor 51, the heat exchanger volume 62 and the receiver volume 81, or against the limits imposed by the engine throttle 82 and the compressor bypass throttle 72 or the compressor 51.

(12) In the following, on account of the intake path model of a gas internal combustion engine 100 represented here, there results for the receiver pressure p5 in the receiver volume V5 or for the control variables based on the receiver pressure p5such as an ACTUAL receiver pressure p5_ACTUAL or a SETPOINT receiver pressure p5_SETPOINT or a simulated receiver pressure p5a role for determining an input mixture fraction of a gas-air mixture at the gas mixer 40 via a number of intermediate states of the mixture fraction in a number of assigned volumes of the intake path 30.

(13) It can be seen that the mass flows m()_G for combustion gas BG and m()_LL for charge air LL at the gas mixer 40 can be set according to a combustion air ratio LAMBDA_SETPOINT or a stoichiometric air ratio Lst not necessarily with the assumption of static conditions along the intake path. The concept of the embodiment therefore takes into account in an intake path modelsuch as described with reference to FIG. 1at least two large volumes in order to summarize the volume of the intake path, namely the receiver volume 80 and the intercooler volume 62. In the context of the intake path model, the intake path 30 is modeled on the basis of the well-known principle of a filling and emptying method. The changes of state in the volumes are in the present case considered quasi-isothermal. This simplifies the system by limiting to conservation of mass in comparison to the adiabatic viewpoint and in particular simplifies simultaneous calculation of the internal combustion engine or of the intake path thereof in real-time. It is however in principle also possible to use an adiabatic or polytropic viewpoint or a targeted transfer of heat in the case of sufficient computation capacity, in order to simulate the changes of state in the intake path.

(14) FIG. 3 further shows that, in addition, it is possible for specific assumptions for devices of the intake path to be converted in the context of additional models, in particular when measurement values for the corresponding device of the intake path 30 are not available. This relates for example to the additional model of a compressor (p2_T2 module) which describes the action of the compressor 51 and the states of the mixture G upstream of the compressor by means of temperature and pressure (G(p1, T1)) and downstream of the compressor (G(p2, T2)). This also relates for example to the additional model for a compressor bypass flap (mass flow_VBP), which describes a mass flow through the compressor bypass flap within the context of a throughflow equation.

(15) In operation, a fuel mixture comprising a charge mixture is fed to the engine 10. The engine is then operated with gas as fuel in the charge mixture. An output mixture fraction (mass flow m()_G,CYL) of the gas-air mixture, assigned to a later mixture state (with state variables p5, T5), is used according to an intake path modelas is described in FIG. 3 with the structure of the controller 200to determine an input mixture fraction (mass flow m()_G,SETPOINT) of a gas-air mixture, assigned at least to an earlier mixture state (with state variables p0, T0). The determining is performed by means of the intake path model as the basis for a computational model for the intake path 30, the gas mixer 40 and the receiver 80, or the inlet to the engine 10.

(16) It is provided, according to the concept of this embodiment, that the output mixture fraction (mass flow m()_G,CYL) of the gas-air mixture is determined at an engine supplyin the present case at a receiver 80. The input mixture fraction (mass flow m()_G,SETPOINT) is determined from the output mixture fraction (mass flow m()_G,CYL) via a number of intermediate states (with state variables pi, Ti, i=5, 3, 2, 1) of the mixture fractionin the present case in the context of a simultaneous real-time calculation. The number of intermediate states (with state variables pi, Ti, i=5, 3, 2, 1) are assigned to a number of volumes (Vi, i=5, 3, 2, 1) or to the components E1, E2, E3, E4 and C3 and C5 in the intake path. The input mixture fraction of a gas-air mixture is determined at the gas mixer 40, and an air flow and/or a gas flow BG is set at the gas mixer 40 as a function of the input mixture fraction.

(17) In the present case, in the intake path model, a number of large volumes are assigned to the intake path; these include: two receiver volumes 81.B, 81.A (with assigned volume V5 and with state variables p5, T5 of a charge mixture therein), at least one cylinder volume in the engine block, at least one intercooler volume 62 (with assigned volume V3 and with state variables p3, T3 of a charge mixture therein), at least one compressor volume at the compressor 51 (with value V2 and with state variables p2, T2 of a charge mixture at the outlet thereof) or the states upstream of the compressor 51 (with state variables p1, T1 of a charge mixture) and with state variables p0, T0 of the surroundings (atmosphere) of intake air, as is indicated in FIG. 1.

(18) The components E1, E2, E3, E4 and C3 and C5 of the intake system, also shown in FIG. 1, are considered in the present intake path model and the states or mass flows of the charge mixture are in this regard simulated or calculated. This has been selected in the present case merely as a preferred example from a range of other possible examples; for example, a modified intake path model can also consider further components in the case of a two-stage forced-induction unit. It is also in principle possible for further volumes to be considered in an intake path model. In extremis, the intake path can be broken down into finitely small or infinitesimal partial volumes and a determination for the states and mass flows of the charge mixture is then performed as a solution, inter alia, to a difference or differential equation system; this consideration of the model refinement can be arrived at taking into account the computational effort and the complexity of the intake path to be simulated; in particular taking into account a real-time capability.

(19) To that end, FIG. 2 shows, in principle and as a flow chart, the sequence of a preferred embodiment of an operating method for a gas internal combustion engine 100 with a gas mixer 40, an intake path 30 and an engine 10, also termed gas engine in the present case, with a number of cylinders Ai, Bi, i=1 . . . 8, as has been described with reference to FIG. 1. It is in principle possible for the operating method to be realized at a gas mixer 40, implementing a determining method, represented in FIG. 2, for setting variables, by means of which it is possible to set an air flow LL and/or a gas flow BG. With reference to FIG. 2, the method provides in the present case, on the basis of the intake path model shown here, in step S0 further steps S1 to S9 which relate to the above-described components E1, E2, E3, E4 and C3 and C5, established by means of the intake path model, of the intake system, which are accordingly shown in FIG. 1.

(20) Specifically, an input mixture fraction of the component E0here assigned to the gas mixer 40is determined backwards, i.e. by reverse calculation based on the knowledge of the output mixture fraction at the component E4 of the intake path. In the present case, the component E4 corresponds essentially to the engine 10 or to a cylinder Ai, Bi, i=1 . . . 8 of the engine 10. In a first step S1 of the determining method, a cylinder filling is determined with corresponding characteristic values for engine speed nMOT and receiver pressure p5 and receiver temperature T5 via a calculation module in the control unit R4, for example a measure for the required air consumption LAMBDA_a at the engine 10 is indicated. In a second step S2 of the determining method, a mixture mass flow m()_CYL can be predefined at the component E4 of the intake systemin this case a cylinder inlet for example to a cylinder Ai, Bi, i=1 . . . 8.

(21) Accordingly, FIG. 3 shows a controller structure of a controller 200 which has a first control unit R4 for carrying out steps S1 and S2. The input variables are an engine speed nMOT and a cylinder input pressurein particular in this case a receiver pressure p5 in a receiver 80 or receiver volume 81.B, 81.A with a total volume V5and possibly further assigned gas state variables of a mixture fraction in the receiver 80 (with receiver volume V5).

(22) In a third step S3 of FIG. 2, the receiver volumes 81.A, 81.B with a total volume V5 of the receiver 80for example assigned to a manifold or a mixing path integrated between cylinder inlets and the engine throttle flap DK in the intake pathare then referenced as further component E1 of the intake system.

(23) In the case of the above-mentioned knowledge of the pressure and temperature conditions in the receiver volume 81.A, 81.B, V5 (receiver pressure p5, receiver temperature T5), it is possible in a fourth step S4 to determine a mixture mass flow through the receiver m()_RECEIVER by means of a control unit R5 shown in FIG. 3. The control unit R5 has a calculation unit which determines the mixture mass flow m()_RECEIVER from the mixture state of a gas-air mixture in the receiver 80 (also frequently termed receiver tube)i.e. in the receiver volumes 81.A, 81.B with volume V5 the state parameters p5, T5 of the charge mixturewith a state equation for the charge mixture and a mass flow equation in accordance with the filling and emptying method for the receiver tube 81.A, 81.B.

(24) Furthermore, the preferred embodiment of the determining method in FIG. 2 provides, on the basis of the intake path model, the intercooler 60 for the further component E2. In the assigned volume V3 of the heat exchanger volume 62, the charge mixture adopts a gas state which can be calculated, in a fifth step S5, by means of the charge pressure p3 and the charge temperature T3 for the volume V3. Similarly, a mixture mass flow m()_LLK through the intercooler 62 is determined according to the determining method represented here. Accordingly, FIG. 3 shows to that end a control unit R3 for determining the mass flow m()_LLK through the intercooler 60 in the form of the charge air cooler with the cooler structure 61. In a sixth step S6, the determining is performed by means of the filling and emptying method for the volume V3 with the knowledge of the mixing state or of the thermodynamic characteristic values thereof and of a corresponding mixture mass throughflow equation.

(25) It is then possible, in a seventh step S7, by means of the mixture mass flows m()_CYL, m()_RECEIVER and m()_LLK, to identify a setpoint value for a combustion air ratio LAMBDA_setpoint and a stoichiometric air requirement (Lst), i.e. the essential SETPOINT characteristic values of the fuel at the further component E0 of the gas mixer 40 in the intake path 30. To that end, there are provided in the controller structure represented in FIG. 3 a first addition member R45 and a second addition member R43 in order to determine, from a mixture mass throughflow equation, the mixture mass flow m()_G,SETPOINT; this taking into account a further control unit R0 for carrying out the seventh step S7, namely for calculating the combustion air ratio LAMBDA_SETPOINT and the stoichiometric air requirement Lst.

(26) It is thus possible to predefine, in the eighth step S8, a suitable setting value at the gas mixer 40, in order to set the input mixture fraction at the gas mixer 40 as a function of an actual engine speed nMOT and the pressure and temperature conditions (essentially p5, T5) at the cylinder inlet.

(27) In the present case, the intake path model is configured with two large volumesnamely the receiver volume 81.B, 81.A (V5) and the intercooler volume 62 (V3)and is introduced into a simulation or calculation of the intake path 30 taking into account the filling/emptying method for both volumes in combination with corresponding throughflow equations for at least the throttles 82, 72 and a compressor model at the compressor 51 (with state variables p1, T1.fwdarw.p2, T2). In the present case, this is sufficient to solve the problems stated in the introduction; the large volumes, which are not sufficiently accounted for in computational methods known hitherto and thus cause an uncoupling of gas mass flow at the gas mixer and the gas mass flow actually present at the motor, are sufficiently accounted for in the intake path model of the determining method represented in FIG. 2. It can simultaneously be seen that the determining method in the form represented here can be carried out relatively simply and thus effectively in terms of calculation time in order to be available in the context of a simultaneous real-time determining. It is thus possible for the gas mixer 40 to be adjusted to the short-term needs of the engine 10 practically in real-time.

(28) In a refinement of the determining method shown in FIG. 2, FIG. 3 shows in detail the control unit R3 and also a feedback for the mass flows m()_DK, m()_RECEIVER and m()_LLK. This makes sense for the case in which a bypass 70 is provided. As shown in FIG. 3, the state variables of the charge mixture G are taken into account as further input variables to the control unit R3 for a mixture state downstream of the compressor 51, namely as compression pressure p2 and compression temperature T2 in addition to the mixture state in or downstream of the intercooler 60, as charge pressure p3 and charge temperature T3. The mixture state downstream of the compressor 51 (state parameters p2, T2) is identified within the context of a further control unit R2 for describing the compressor 51 in a compressor model.

(29) The compressor 51 is accounted for in the intake path model as a further intake path device E3 with a control unit R2 arranged upstream thereof. A mixture mass flow m()_LLK of the charge air cooler 60 serves as input to the control unit. This is in turn dependent on a mixture mass flow m()_VBP at the compressor bypass flap 72 and also on the mixture mass flow at an engine throttle flap 82.A, 82.B. In the present case, these mixture mass flows are added in the addition unit R42 in order to give the mixture mass flow m()_LLK supplied at the inlet of the heat exchanger 60. The mixture mass flow m()_DK at the engine throttle flap 82.B, 82.A is in turn obtained as the output from the addition member R45, i.e. reverse-calculated from the mixture mass flow m()_CYL at the cylinder inlet and receiver volume.

(30) The further input of a mixture mass flow m()_DK returned from the throttle flap DK in feedback to the control unit R2i.e. the influence of the intake path device C5 for setting the return flow of a charge mixture through the compressor bypass 70is obtained through the feedback, shown in dashed lines in FIG. 3, of the output of the addition unit R45 to the input of the addition unit R42.

(31) The mixture mass flow through the compressor bypass 70 is in turn obtained in the context of a throughflow equation at the further intake path device C3, namely in this case the compressor bypass flap 72. While the mixture mass flow m()_DK at the engine throttle flap DK essentially results from the setting DK of the throttle flap as intake path device C5, the mixture mass flow of the compressor bypass m()_VBP essentially results from the setting VBP of the compressor bypass throttle 72 and taking into account the pressure ratios at the beginning and at the end of the compressor bypass 70, namely taking into account p1, T1 (i.e. the charge mixture state upstream of the compressor 51) and p3, T3 (i.e. the charge mixture state upstream of the throttle flap DK).

(32) Thus, the further control unit R1 obtains, as input variables, not only the setting VBP of the compressor bypass throttle 72 but also the gas state variables p3, T3 in the intercooler 60 and at least the intake pressure p1, T1 upstream of the compressor, wherein the temperature T1 can essentially correspond to the ambient temperature T0.

(33) As a result, it is possible, using the controller structure 200 shown in more detail in FIG. 3, to realize an improved method for operating the gas internal combustion engine 100.