Method and device for operating an internal combustion engine
A method for operating an internal combustion engine, which has: an intake section and an engine with an number of cylinders and a receiver which is arranged upstream of the cylinders wherein the intake section has: a supercharging system with a compressor and a bypass for bypassing the supercharging system, and wherein the receiver is assigned an engine throttle, and the bypass is assigned a compressor bypass throttle; and a setting of the engine throttle and/or of the compressor bypass throttle is set as a function of the operation in order to influence a charge fluid. The intake section is assigned an intake section model by which at least a mass flow and/or state of the charge fluid upstream of the engine are/is determined and on the basis of a determination result the compressor bypass throttle is set as a function of the engine throttle.
1. A method for operating an internal combustion engine which has an intake section and an engine with a number of cylinders and a receiver which is arranged upstream of the cylinders, wherein the intake section has a supercharging system having a compressor and a bypass for bypassing the supercharging system, and wherein the receiver is assigned an engine throttle, and the bypass is assigned a compressor bypass throttle, the method including setting the engine throttle and/or the compressor bypass throttle as a function of operation in order to influence a charge fluid, wherein the intake section is assigned an intake section model by which at least one mass flow and/or state of the charge fluid upstream of the engine is determined on a first timescale and on a second timescale faster than the first timescale and based on the determination result the compressor bypass throttle is set as a function of the engine throttle.
2. The method as claimed in claim 1 , wherein the compressor bypass throttle is set as a function of the engine throttle on the first timescale,
by determining a quasi-steady-state mixture mass flow for at least the receiver volume and/or by determining a quasi-steady-state mixture mass flow for a heat exchanger by a filling and emptying method for the receiver volume and/or the heat exchanger.
3. The method as claimed in claim 1 , wherein the compressor bypass throttle is set as a function of the engine throttle on the second timescale by determining a transient mixture mass flow for the engine throttle by at least one time-dependent flow equation for the engine throttle, taking into account a time-dependent flow equation for the compressor bypass throttle.
4. The method as claimed in claim 1 , wherein an open cross section setting of the compressor bypass throttle is determined as function of a setting of the engine throttle in real time and/or simultaneously, for a first case of the first timescale and/or a second case of the second timescale.
5. The method as claimed in claim 4 , wherein for setting the engine throttle the following are taken into account on the first and/or the second timescale:
a mixture mass flow across the engine throttle, and/or
a mixture state in the receiver.
6. The method as claimed in claim 1 , wherein the compressor bypass throttle is set as a function of the engine throttle for transient operation of the engine, wherein an operating mode of transient operation is selected by forming at least one differential value across the engine throttle relating to the mixture mass flow and/or the mixture state of the mixture portion.
7. The method as claimed in claim 1 , wherein within a simultaneous real-time determination, by the intake section model, serving as a basis of a computational model for the intake section, in a closed-loop control system at least one input mixture portion, assigned to an earlier mixture state, of the gas-air mixture is formed, by an output mixture portion, assigned to at least one later mixture state, of the gas-air mixture.
8. The method as claimed in claim 1 , including determining by way of the intake section model at least one mixture mass flow across at least one engine throttle and across at least one compressor bypass throttle and/or
a mixture state of the mixture portion in at least one receiver volume and at least one further large volume of the intake section.
9. The method as claimed in claim 8 , wherein the further large volume is that of at least one of a charge-type heat exchanger, a bypass section and a compressor.
10. The method as claimed in claim 1 , wherein in one of the operating modes a steady-state or transient operation is detected by a differential value of a mass-flow difference and/or a pressure difference or some other mixture state across the engine throttle, including,
in an operating mode of transient operation detecting if the differential value is above a first limiting value and/or has a change of sign, and,
in an operating mode of steady-state operation detecting if the differential value is below a second limiting value or does not have a change of sign.
11. The method as claimed in claim 1 , wherein in case of steady-state operation of the internal combustion engine coefficients of a time-dependent flow equation are scaled by comparison of computational results relating to the first timescale based on a filling and emptying method, and computational results relating to the second timescale based on a flow equation.
12. The method as claimed in claim 1 , wherein the engine throttle is assigned a first throttle characteristic diagram and/or the compressor bypass throttle is assigned a second throttle characteristic diagram, wherein
the first and/or second throttle characteristic diagram each specify a quasi-steady-state mass flow,
in a first dependence on a pressure upstream and/or downstream of the throttle, and/or
in a second dependence on a throttle setting.
13. The method as claimed in claim 1 , wherein the mass flow is a mixture mass flow and the state is a mixture state.
14. A closed-loop control system for an internal combustion engine having an engine with a number of cylinders, the closed-loop control system comprising:
an intake section and a receiver which is arranged upstream of the cylinders, wherein the intake section has a supercharging system having a compressor and a bypass for bypassing the supercharging system, wherein the receiver is assigned an engine throttle, and the bypass is assigned a compressor bypass throttle, and wherein a setting of the engine throttle and/or of the compressor bypass throttle for influencing a mixture portion of the gas-air mixture is settable as a function of operation by the closed-loop control system, wherein
in the closed-loop control system of the intake section, an intake section model is assigned, by which at least one mixture mass flow and/or mixture state of the mixture portion upstream of the engine is determined on a first timescale and on a second timescale faster than the first timescale and based on a determination result,
the compressor bypass throttle being set as a function of the engine throttle by the closed-loop control system.
15. The closed-loop control system according to claim 14 , wherein the closed-loop control system is configured:
to determine a mixture mass flow and/or a mixture state of the mixture portion in real time and/or simultaneously, and
to force the compressor bypass throttle to be set as a function of the engine throttle on one of the timescales.
16. An internal combustion engine, comprising:
an engine having a number of cylinders; and
a closed-loop control system as claimed in claim 14 .
17. The internal combustion engine as claimed in claim 16 , wherein the internal combustion engine is a gas internal combustion engine.
18. The internal combustion engine as claimed in claim 16 , wherein the internal combustion engine is a dual-fuel internal combustion engine.