METHOD FOR CALCULATING REACTION HEAT IN AN EXHAUST SYSTEM

Abstract

A method for calculating reaction heat in an exhaust system of an internal combustion engine by means of a model, comprising a first model component and a second model component, wherein the first model component refers to a calculation of exhaust components flowing from valves of the internal combustion engine, the second model component relates to the entire exhaust system, and total masses from the first model component are divided along the exhaust system onto the individual components of the exhaust system.

Claims

1. A method for calculating reaction heat in an exhaust system (300) of an internal combustion engine by means of a computer configured with a model (312) having a first model component (10, 314) and a second model component (150, 316), wherein the computer, via the first model component (10, 314), calculates exhaust components flowing from valves of the internal combustion engine, and the computer, via the second model component (150, 316) divides total masses from the first model component (10, 314) along the exhaust system between individual components (302) of the exhaust system (300).

2. The method according to claim 1, wherein the incompletely combusted (rich) exhaust components and air flowing directly into the exhaust system (300) are calculated in a cylinder-specific manner in the first model component (10, 314).

3. The method according to claim 2, wherein the cylinder-specific calculation from the current engine operational variables covers at least one special mode of operation.

4. The method according to claim 3, wherein the at least one special mode of operation is selected from a group consisting of: overrun shut-off, cylinder suppression, half-engine operation, purging, and cylinder balance.

5. The method according to claim 1, wherein the dividing is carried out in the second model component (150, 316) depending on the mass flow rate and the volume of the components (302).

6. The method according to claim 1 wherein, in the second model component (150, 316), a storage of a portion of the residual gases into the catalyst surface is modeled depending on an applied adsorption efficiency.

7. An assembly for calculating reaction heat in an exhaust system (300) configured to perform a method according to claim 1.

8. A non-transitory, computer-readable medium containing instructions that when executed by the computer cause the computer to calculate reaction heat in an exhaust system (300) of an internal combustion engine by means of a model (312) having a first model component (10, 314) and a second model component (150, 316), by calculating, via the first model component (10, 314), exhaust components flowing from valves of the internal combustion engine, and divide, via the second model component (150, 316), total masses from the first model component (10, 314) along the exhaust system between individual components (302) of the exhaust system (300).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 shows input and output variables of a first model component in a block diagram.

[0023] FIG. 2 shows the first model component in a block diagram.

[0024] FIG. 3 shows input and output variables of a second model component in a block diagram.

[0025] FIG. 4 shows the second model component in a block diagram.

[0026] FIG. 5 purely schematically shows an exhaust system having an arrangement for performing the method.

DETAILED DESCRIPTION

[0027] The invention is illustrated schematically in the drawings on the basis of embodiments and is described in detail below with reference to the drawings.

[0028] FIG. 1 shows input and output variables of a first model component, altogether designated with the reference numeral 10. Input variables are: [0029] cylinder assignment to exhaust bank (reference numeral 12), [0030] relative air charge in the cylinder (reference numeral 14), [0031] request cold engine catalyst heating (reference numeral (16), [0032] request catalyst heating to keep catalyst warm (reference numeral 18), [0033] request catalyst heating for desulfurization of the main catalyst (reference numeral 20), [0034] status of operating mode HSP (homogenous-split) is set (reference numeral 22), [0035] EPM (Engine Position Management) software cylinder counter (reference numeral 24), [0036] engine speed (reference numeral 26), [0037] selecting the engine speed (reference 28), [0038] average efficiency depending on the ignition angle bank 1 (reference numeral 30), [0039] stoichiometric air-fuel ratio (reference numeral 32), [0040] cylinder-specific mixture factor (reference numeral 34) [0041] cylinder-specific array of relative fuel mass (reference numeral 36), [0042] cylinder-specific Atkinson fuel mass (reference numeral 38), [0043] total injection masking pattern (reference numeral 40), [0044] oxygen target value in combustion chamber (reference numeral 42), [0045] mass flow from intake pipe in manifold during valve overlap (reference numeral 44), [0046] total relative filling without internal residual gas (reference numeral 46), [0047] relative fuel fraction of outgassing fuel from engine oil (reference numeral 48), [0048] relative mixture fraction for tank venting (reference numeral 50), [0049] charge conversion factor in mass flow (reference numeral 52).

[0050] Output variables are control unit signals: [0051] fuel equivalent oxygen mass flow at exhaust valve bank 1 (reference numeral 60), [0052] oxygen mass flow at exhaust valve bank 1 (reference numeral 62),

[0053] FIG. 2 shows a flow chart of the first model component 10 in a block diagram. The plot shows a first calculation block 100 for a relative fuel charge flowing into engine bank 1, a second calculation block 102 for a combustion effectiveness factor for engine bank 1, a third calculation block 104 for calculating the incompletely reacted air and fuel contents in the engine, and a functional block 106 for calculating the reactive residual gases flowing from the engine into the exhaust system, for example, conversion of mass fuel flow and correction of overflowing fresh air before combustion.

[0054] Input variables are: [0055] calculate function command (reference numeral 110), [0056] engine speed selection (reference numeral 112), [0057] engine speed status=0 (reference numeral 114), [0058] total relative charge without internal residual gas (reference numeral 116), [0059] relative air charge flowing into engine (without inert gas) bank 1 (reference numeral 118).

[0060] Further variables are: [0061] relative fuel charge flowing into engine bank 1 (reference numeral 120), [0062] combustion effectiveness factor engine bank 1 (reference numeral 122), the effectiveness refers here to the chemical conversion efficiency of air and fuel, [0063] relative air charge after combustion (accumulated since the last calculation of the function) bank 1 (reference numeral 124), air or air lean gas components not fully reacted here after combustion, [0064] relative fuel charge after combustion (accumulated since the last calculation of the function) bank 1 (reference numeral 126), fuel or oil gas components not fully reacted here after combustion.

[0065] Output variables are: [0066] fuel equivalent oxygen mass flow at exhaust valve bank 1 (reference numeral 130), [0067] oxygen mass flow at exhaust valve bank 1 (reference numeral 132).

[0068] FIG. 3 shows input and output variables of a second model component, altogether designated with the reference numeral 150. Input variables are: [0069] exhaust temperature array (reference numeral 152), [0070] exhaust mass flow array (reference numeral 154), [0071] index of the first brick catalyst (reference numeral (156), [0072] index of the last brick catalyst (reference numeral (158), [0073] turbo index position (reference numeral 160), [0074] y-split index position (reference numeral 162), [0075] calculated oxygen storage capacity, catalyst 1 (reference numeral 164), [0076] calculated oxygen storage capacity, catalyst 2 (reference numeral 166), [0077] calculated oxygen storage capacity, catalyst 3 (reference numeral 168), [0078] oxygen storage capacity of a new catalyst 1 (reference numeral 170), [0079] oxygen storage capacity of a new catalyst 2 (reference numeral 172), [0080] oxygen storage capacity of a new catalyst 3 (reference numeral 174), [0081] fuel equivalent oxygen mass flow at exhaust valve bank 1 (reference numeral 176), [0082] oxygen mass flow at exhaust valve bank 1 (reference numeral 178), [0083] number of brick catalysts (reference numeral 180), [0084] exhaust pressure array (reference numeral 182), [0085] exhaust lambda upstream of the catalysts (reference numeral 184), [0086] aging factor catalyst array, bank 1 (reference numeral 186), [0087] stoichiometric air-fuel ratio (reference numeral 188),

[0088] Output variable is a control unit signal: [0089] reaction heat in the elements of the exhaust system, bank 1 (reference numeral 190).

[0090] FIG. 4 shows a flow chart of the second model component 150 in a block diagram. The illustration shows a first functional block 200 for element properties where various properties of the currently calculated exhaust system element are assigned; a second functional block 202 for determining that there is no dummy behavior; the exhaust system is replicated in the exhaust temperature model in the so-called structure vector, empty spaces therein are filled in with dummy elements; if the element to be calculated is a dummy then the function is not calculated. The illustration further shows a third functional block 204 for calculating lean and oil gas mass in the gas of the current element; a fourth functional block for determining whether the current element is a brick catalyst; a fifth functional block 208 for calculating lean and oil gas mass stored in the catalyst surface, upon storage of lean gas in the catalyst surface, a reaction heat is released, which is also calculated here; a sixth functional block 210 for determining whether oil and lean gases can react in the current element; a seventh functional block 212 for calculating the reaction of the oil and lean gases and the resulting reaction heat; an eighth functional block 214, which is an interface for providing the output variables; and a ninth functional block 216 for incrementing the element counters.

[0091] Variables are: [0092] calculation commands 1 to 7 (reference numeral 220), the sequence of calculation, [0093] software class elemental properties in blocks 202, 206, 210 (reference numeral 222). [0094] lean gas mass in the gas of the current element (reference numeral 224), [0095] oil gas mass (oxygen equivalent) in the gas of the current element (reference numeral 226), [0096] data structure in which information on the catalyst surface is present (reference numeral 228), for example, oil and lean gas mass currently stored in the surface, [0097] reaction heat due to storage of lean gas in the catalyst surface (reference numeral 230), [0098] lean gas mass in the gas of the current element after reaction (reference numeral 232), [0099] lean gas mass in the surface of the current element (if a catalyst) after reaction (reference numeral 234), [0100] oil gas mass in the gas of the current element after reaction (reference numeral 236), [0101] oil gas mass in the surface of the current element (if a catalyst) after reaction (reference numeral 238), [0102] reaction heat due to reaction of oil and lean gases (reference numeral 240)

[0103] The model is thus divided into two model components 10, 150 and areas. The first area relates to the calculation of exhaust components flowing out of the valves of the engine. Here, the incompletely reacted exhaust components, as well as the air flowing directly into the exhaust system, are calculated individually for each cylinder. The amount of air, the mixture, and the ignition timing must be observed. By cylinder-specific calculation from the current engine operating variables, special modes of operation, such as overrun shut-off, cylinder suppression, half-engine operation, scavenging, and purging and cylinder balance, are automatically covered.

[0104] Output from the first model range is the sum of the mass flows of the reactive residual gas components across all cylinders of an exhaust bank.

[0105] The second area refers to the entire exhaust system. Here, the total masses from the first model part are distributed along the exhaust system to the individual components, such as manifold, turbocharger, catalytic converter, particulate filter. In catalysts and catalytically coated particulate filters, storage of a portion of the residual gases into the catalyst surface is also modeled depending on an applied adsorption efficiency.

[0106] Because the catalytic surfaces have limited storage capacity, the storage capability values of the individual catalysts are read from the catalytic converter diagnostic functions; alternatively, a fixed value may be specified. The heat generated by the exothermic reaction of storing oxygen in the catalytic surfaces is calculated.

[0107] Depending on the amount of rich and lean portions present in the gas volume and on the surface, the reaction heat is modeled by the reaction of rich and lean exhaust components to carbon dioxide and water depending on an applied reaction efficiency. Unreacted portions from the surface are considered again in the next calculation step. Components remaining in the gas are passed to the subsequent exhaust element.

[0108] Finally, the proportions of heat generated from the adsorption and reaction per exhaust element are added and used to calculate the modeled exhaust temperature in that exhaust element.

[0109] In FIG. 5, a simplified exhaust system is shown altogether with reference numeral 300. A number of components 302 and a catalyst 304 are provided therein. The catalytic converter 304 also represents a component of the exhaust system 300. The exhaust system 300 is associated with an arrangement 310 for performing the method. In this arrangement 310, a model 312 having a first model component 314 and a second model component 316 is provided.