Method and control unit for operating a vehicle

Abstract

A method for operating a vehicle having a gasoline engine includes determining a density of a gasoline to be combusted in the gasoline engine, determining a stoichiometric air demand, determining a critical temperature from the density of the gasoline to be combusted and the stoichiometric air demand, and adapting countermeasures to prevent vapor bubbles based on the determined critical temperature.

Claims

1. A method for operating a vehicle having a gasoline engine, comprising the steps of: determining a density of a gasoline to be combusted in the gasoline engine; determining a stoichiometric air demand; determining a critical temperature from the density of the gasoline to be combusted and the stoichiometric air demand; and adapting countermeasures to prevent vapor bubbles based on the determined critical temperature.

2. The method according to claim 1, wherein the critical temperature is determined based on a product of the density of the gasoline to be combusted and the stoichiometric air demand to the power of a factor P.

3. The method according to claim 2, wherein the critical temperature is determined based on a continuous function of the product.

4. The method according to claim 2, wherein the critical temperature is determined based on a linear function of the product.

5. The method according to any one of claim 2, wherein the critical temperature is determined based on a polynomial function of the product.

6. The method according to any one of claim 2, wherein the critical temperature is determined based on a sectionally defined function of the product.

7. The method according to any one of claim 1, wherein the critical temperature is determined based on a current date or a date of a last refueling of the vehicle.

8. The method according to any one of claim 1, wherein the critical temperature is determined based on the location of the vehicle.

9. A non-transitory computer-readable medium on which is stored a computer program comprising instructions which, when executed by a computer, perform the method according to claim 1.

10. A control unit of a vehicle configured to perform he method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows limiting temperatures for a plurality of gasoline samples as a function of the researched octane number (RON);

(2) FIG. 2 shows limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand:

(3) FIG. 3 shows, for the USA region, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature:

(4) FIG. 4 shows, for the USA region, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature:

(5) FIG. 5 shows, for the China region, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature:

(6) FIG. 6 shows, for the China region, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature;

(7) FIG. 7 shows, for the Europe region, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature; and

(8) FIG. 8 shows, for regions having restricted fuel quality, limiting temperatures for a plurality of gasoline samples as a function of the product of the density σ of the gasoline to be combusted, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, and also functions for determining the critical temperature.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) In FIG. 1, the measured limiting temperature in degrees Celsius (° C.) is plotted over the researched octane number (RON), for a plurality of different gasoline samples from various world regions (USA, China, Russia, EU, remainder of the world). The samples depicted with solid circles were taken in winter here and the samples depicted with empty circles were taken in summer.

(10) A dependence of the limiting temperature on the RON is not recognizable. Further previously selected constant critical temperatures T.sub.S, T.sub.W1, T.sub.W2 are shown in the diagram. The critical temperature for the summer T.sub.S is selected identically for the various world regions here and is, for example, 110° C. For the winter, a critical temperature T.sub.W1 is selected for the regions China and USA of, for example, 100° C. and a critical temperature T.sub.W2 is selected for the regions Russia, EU, and the remainder of the world of, for example, 103° C.

(11) In FIG. 2, the measured limiting temperatures for the plurality of samples are respectively plotted for samples taken in winter, which are depicted with crosses “+”, and for samples taken in summer, which are depicted with circles “o”, over the product of the density σ of the samples, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand.

(12) A correlation of the limiting temperature with this product is clearly recognizable.

(13) In FIG. 3, the measured limiting temperatures for a plurality of samples taken in the USA are respectively plotted for samples taken in winter, which are depicted with crosses “+”, and for samples taken in summer, which are depicted with circles “o”, over the product of the density σ of the gasoline samples, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand. Furthermore, the previously selected, constant critical temperatures for the summer T.sub.S and the winter T.sub.W1 are shown for this region.

(14) The consideration of the density σ of the gasoline and the stoichiometric air demand L.sub.St of the gasoline can enable the critical temperature for a plurality of gasoline samples to be selected to be higher than the previously selected constant critical temperature.

(15) A first straight line G.sub.S for determining the critical temperature for the summer is shown in FIG. 3. The straight line is preferably selected here in such a way that at least essentially all determined limiting temperatures for the summer are above the straight line.

(16) The use of the underlying linear function for this straight line for determining the critical temperature (bounded at the bottom by T.sub.S) results, for example, in the selection of a higher critical temperature than previously in 93.1% of the samples taken in summer. On average, the critical temperature is increased over the previous constant critical temperature T.sub.S by 3.2° C.

(17) A second straight line G.sub.W for determining the critical temperature for the winter is also shown in FIG. 3. If the linear function underlying this straight line is used for determining the critical temperature (bounded at the bottom by T.sub.W1), a higher critical temperature is obtained, for example, in 94.1% of the samples taken in winter. On average, the critical temperature is increased over the previous constant critical temperature T.sub.W1 by 3.6° C. The straight line is preferably selected here in such a way that at least essentially all determined limiting temperatures for the winter are above this straight line.

(18) The higher critical temperature enables countermeasures for preventing vapor bubble formation to be initiated later. Consumption disadvantages accompanying the countermeasures (for example, due to higher power consumption by running electric fans) and comfort losses (for example, due to electric fans continuing to run after the gasoline engine is turned off) can therefore be reduced.

(19) FIG. 4 once again shows the values of the gasoline samples shown in FIG. 3.

(20) In contrast to FIG. 3, a sectionally defined function of the product of the density σ of the gasoline, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, is used for determining the critical temperature for the samples taken in summer. In particular, in the exemplary embodiment shown, two linear function sections are used which are visualized by the straight lines G.sub.S1 and G.sub.S2 in the diagram. In samples in which the product of the density σ of the gasoline, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, assumes a very high value, this can enable once again a very clear increase of the critical temperature.

(21) In FIG. 5, the measured limiting temperatures for a plurality of samples taken in China are respectively plotted for samples taken in winter, which are depicted with crosses “+”, and for samples taken in summer, which are depicted with circles “o”, over the product of the density σ of the gasoline samples, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand. Furthermore, previously selected, constant critical temperatures for the summer T.sub.S and the winter T.sub.W1 are shown for this region.

(22) A first straight line G.sub.S for determining the critical temperature for the summer is shown. The use of the underlying linear function for this straight line for determining the critical temperature (bounded on the bottom by T.sub.S) results in the selection of a higher critical temperature than previously, for example, in 99.2% of the samples taken in summer. On average, the critical temperature is increased in relation to the previous constant critical temperature T.sub.S by 13.8° C.

(23) A second straight line G.sub.W for determining the critical temperature for the winter is shown in a comparable manner. If the linear function underlying this straight line is used to determine the critical temperature (bounded on the bottom by T.sub.W1), a higher critical temperature is obtained, for example, in 99.7% of the samples taken in winter. On average, the critical temperature increases over the previous constant critical temperature T.sub.W1 by 22.1° C.

(24) FIG. 6 once again shows the values of the gasoline samples shown in FIG. 5. In contrast to FIG. 5, sectionally defined functions of the product of the density σ of the gasoline, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand, are used to determine the critical temperatures for the samples taken in summer and winter.

(25) In particular, in the exemplary embodiment shown, two linear function sections are used for the summer, which are visualized in the diagram by the straight lines G.sub.S1 (bounded on the bottom by T.sub.S) and G.sub.S2, and two linear function sections are used for the winter, which are visualized in the diagram by the straight lines G.sub.W1 (bounded on the bottom by T.sub.W1) and G.sub.W2. This results in a further elevation of the average increase of the critical temperature in comparison to the previous constant critical temperature. In particular, the average increase of the critical temperature is 17.5° C. for summer fuels and 24.5° C. for winter fuels.

(26) In FIG. 7, the measured limiting temperatures for a plurality of samples taken in Europe are respectively plotted for samples taken in winter, which are depicted with crosses “+”, and for samples taken in summer, which are depicted with circles “o”, over the product of the density σ of the gasoline samples, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand. Furthermore, the previously selected, constant critical temperatures for the summer T.sub.S and the winter T.sub.W2 are shown for this region.

(27) A first straight line G.sub.S for determining the critical temperature for the summer is shown. The use of the underlying linear function for this straight line for determining the critical temperature (bounded on the bottom by T.sub.S) results in the selection of a higher critical temperature than previously, for example, in 99.3% of the samples taken in summer. On average, the critical temperature is increased in relation to the previous constant critical temperature T.sub.S by 3.4° C.

(28) A second straight line G.sub.W for determining the critical temperature for the winter is shown in a comparable manner. If the linear function underlying this straight line is used to determine the critical temperature (bounded on the bottom by T.sub.W2), a higher critical temperature is obtained, for example, in 99.1% of the samples taken in winter. On average, the critical temperature increases over the previous constant critical temperature T.sub.W2 by 3.5° C.

(29) In FIG. 8, the measured limiting temperatures for a plurality of samples taken in regions having restricted fuel quality are respectively plotted for samples taken in winter, which are depicted with crosses “+”, and for samples taken in summer, which are depicted with circles “o”, over the product of the density σ of the gasoline samples, on the one hand, and the stoichiometric air demand L.sub.St to the power of 0.7, on the other hand. Furthermore, the previously selected, constant critical temperatures for the summer T.sub.S and the winter T.sub.W1 are shown for this region.

(30) A sectionally defined linear function is used to determine the critical temperature for the summer, which are visualized by the straight line sections G.sub.S1 (bounded on the bottom by T.sub.S) and G.sub.S2 in the diagram. This results in the selection of a higher critical temperature than previously, for example, in 57.0% of the samples taken in summer. On average, the critical temperature is increased in relation to the previous constant critical temperature T.sub.S by 3.9° C.

(31) A second linear function, also sectionally defined, is used in a comparable manner for the determination of the critical temperature for the winter. Accordingly, two straight line sections G.sub.W1 (bounded on the bottom by T.sub.W2) and G.sub.W2 are shown in FIG. 8. If the linear functions underlying these straight lines are used to determine the critical temperature, a higher critical temperature is obtained, for example, in 93.3% of the samples taken in winter. On average, the critical temperature increases over the previous constant critical temperature T.sub.W2 by 9.2° C.