Method for Determining a Parameter Characterizing the Anti-Knock Property of a Fuel and Corresponding Test System

Abstract

The disclosure relates to a method for determining a parameter characterizing the anti-knock property of a fuel using a test engine having at least one cylinder, wherein the fuel undergoes combustion inside the cylinder during the course of the method and the cylinder pressure generated by the combustion is detected using a pressure sensor. The pressure sensor has a linear pressure output signal curve. A parameter characterizing the anti-knock property of the fuel is calculated based on the output signal of the pressure sensor. The calculation is done using a mathematical model that considers the deviation of the pressure output signal curve of the pressure sensor being used from the pressure output signal curve of a pick-up sensor prescribed in the ASTM D2699 standard. Moreover, a test system to determine the anti-knock property of a fuel is disclosed.

Claims

1. A method for determining a parameter characterizing an anti-knock property of a fuel using a test engine having at least one cylinder, the method comprising the steps of: combusting the fuel inside the cylinder; detecting a cylinder pressure generated by the combustion using a pressure sensor with a pressure output signal curve that is linear; calculating the parameter based on an output signal of the pressure sensor based on a mathematical model that takes into account a deviation of the pressure output signal curve of the pressure sensor from a pressure output signal curve of a pickup sensor prescribed in the ASTM D2699 standard; wherein the mathematical model comprises a transfer function with which the parameter characterizing the anti-knock property is calculated from the output signal of the pressure sensor, the transfer function includes use of a differential equation, the differential equation includes one of time derivatives of different orders of the output signal of the pressure sensor or the cylinder pressure determined from the time derivatives, and the time derivatives are weighted differently within the differential equation; and simulating the pickup sensor prescribed in the ASTM D2699 standard using the mathematical model by correcting the output signal of the pressure sensor in such a way that a corrected signal corresponds fundamentally to the output signal of the pickup sensor prescribed in the ASTM D2699 standard under an identical cylinder pressure.

2. A test system to determine a parameter characterizing the anti-knock property of a fuel, the test system comprising: a test engine having at least one cylinder and a pressure sensor with a pressure output signal curve that is linear, wherein the cylinder pressure that prevails during the combustion of the fuel in the cylinder is detected using the pressure sensor; an evaluation unit with which the anti-knock property of the parameter characterizing the anti-knock property of the fuel can be calculated, based on an output signal of the pressure sensor, and based on a mathematical model that takes into account the deviation of the pressure output signal curve of the pressure sensor from a pressure output signal curve of a pickup sensor prescribed in ASTM D2699 standard; wherein the mathematical model comprises a transfer function with which the parameter characterizing the anti-knock property is calculated from the output signal of the pressure sensor, the transfer function includes use of a differential equation, the differential equation includes one of time derivatives of different orders of the output signal of the pressure sensor or the cylinder pressure determined from the time derivatives, and the time derivatives are weighted differently within the differential equation; and simulating the pickup sensor prescribed in the ASTM D2699 standard using the mathematical model by correcting the output signal of the pressure sensor in such a way that a corrected signal corresponds fundamentally to the output signal of the pickup sensor prescribed in the ASTM D2699 standard under an identical cylinder pressure.

3. The method according to claim 1, further comprising simulating a measuring chain consisting of the pickup sensor, a detonation meter and a knock meter described in the ASTM D2699 standard is simulated using the mathematical model.

4. The method according to claim 1, further comprising filtering the output signal of the pressure sensor using a low-pass filter to create a filtered output signal, and that the parameter characterizing the anti-knock property of the fuel is calculated based on the filtered output signal.

5. The method according to claim 1, wherein the pressure sensor is a piezoelectric pressure sensor.

6. The method according to claim 4, wherein the pressure sensor is a piezoelectric pressure sensor.

7. The method according to claim 1, wherein an evaluation of the output signal of the pressure sensor is done using an artificial neuronal network, wherein the artificial neuronal network uses a relationship between the output signal of the pressure sensor and respective octane number of the fuel to be analyzed to analyze a plurality of different types of fuels, wherein the octane number of the fuel to be analyzed is obtained by considering the ASTM D2699 standard or the D2700 standard.

8. The method according to claim 4, wherein an evaluation of the output signal of the pressure sensor is done using an artificial neuronal network, wherein the artificial neuronal network uses a relationship between the output signal of the pressure sensor and respective octane number of the fuel to be analyzed to analyze a plurality of different types of fuels, wherein the octane number of the fuel to be analyzed is obtained by considering the ASTM D2699 standard or the D2700 standard.

9. The method according to claim 5, wherein an evaluation of the output signal of the pressure sensor is done using an artificial neuronal network, wherein the artificial neuronal network uses a relationship between the output signal of the pressure sensor and respective octane number of the fuel to be analyzed to analyze a plurality of different types of fuels, wherein the octane number of the fuel to be analyzed is obtained by considering the ASTM D2699 standard or the D2700 standard.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Additional specific aspects of the invention are described and shown below:

[0038] FIG. 1 is a schematic view of a test engine used to determine the anti-knock property of a fuel as used, for example, according to the ASTM D2699 (EN ISO 5163) or D2700 (EN ISO 5164) standard;

[0039] FIG. 2 is a schematic view of the measuring chain described in the ASTM D2699 (EN ISO 5163) or D2700 (EN ISO 5164) standard; and

[0040] FIG. 3 is a schematic view of a test system according to the disclosure used to execute the method according to the disclosure.

DETAILED DESCRIPTION

[0041] Typically, the determination of octane numbers is carried out empirically throughout the world according to standardized procedures in the laboratories of fuel producers, where special one-cylinder test engines with a variable compression ratio are used to set the corresponding fuel quality.

[0042] The objective is to compare the knock intensity of the fuel to be tested with that of fuels with known octane numbers and determine the octane numbers through interpolation, if applicable. In the standard, isooctane was arbitrarily allocated the octane number of 100 and n-heptane the octane number of 0. By mixing these components, it is possible to manufacture a fuel having the same knock intensity as the fuel to be tested. Then, the octane number being sought corresponds to the volumetric proportion of the isooctane in the fuel mixture. Testing conditions differentiate between MON and RON, although all other procedural steps coincide and even the same measuring technology and the same test engine 2 are used.

[0043] FIG. 1 shows a test engine 2 to determine the anti-knock property of a fuel used according to the ASTM D2699 or D2700 standard (determination of the RON or MON), for example.

[0044] The extent of knock intensity is generated through an electric sensor (pickup sensor 5) screwed firmly into the engine's combustion chamber (FIG. 1) and displayed via an analog circuit, the so-called detonation meter 7, on an indicator instrument (knock meter 8) (FIG. 2).

[0045] Applicant's own research has revealed that the signal provided by the pickup sensor 5 is not proportional to the cylinder pressure, so that an accuracy of no more than +/−0.2 octane numbers can be achieved with the above-mentioned procedure.

[0046] Furthermore, WO 2009/130254 A1 describes a method in which the cylinder pressure is measured with a pressure sensor 4 whose output signal behaves proportionately to the cylinder pressure (hence, the pressure sensor 4 has a linear pressure output signal characteristic curve). The pressure signals determined are statistically evaluated to finally generate a parameter that allows a reliable evaluation of the actual anti-knock property of the respective fuel.

[0047] However, the disadvantage of the method described there is that the parameters that are determined do not coincide with the octane numbers obtained when the above-mentioned standards are observed.

[0048] So an octane number that coincides with the octane number that would have been determined if one of the above-mentioned standards had been observed can also be determined now with the test system described in WO 2009/130254 A1, the suggestion is now made—based on the output signal of the pressure sensor 4 used (which has a linear pressure output signal curve)—to calculate a parameter characterizing the anti-knock property of the fuel, wherein the calculation takes place based on a mathematical model that takes into account the deviation of the pressure output signal curve of the pressure sensor 4 that is used from the pressure output signal curve of a pickup sensor 5 prescribed in the ASTM D2699 or D2700 standard.

[0049] Therefore, according to the disclosure, a test engine 2 is used (as shown schematically in FIG. 3), wherein the test engine 2 has a cylinder 1, a piston 3 within the cylinder 1, and a pressure sensor 4 to detect the cylinder pressure generated during fuel combustion (wherein the pressure sensor 4 is designed so that its output signal behaves proportionally to the cylinder pressure).

[0050] Moreover, the pressure sensor 4 is connected to an evaluation unit 6 (e.g., a personal computer) with installed evaluation software to evaluate the output signal according to the invention's method described above and convert it to an octane number.

[0051] The general essence of the disclosure is therefore to determine an octane number with a test system not using a pickup sensor 5 prescribed in the ASTM D2699 (EN ISO 5163) or D2700 (EN ISO 5164) standard, which number corresponds to the octane number that would have been obtained if the respective fuel sample would have been analyzed according to one of the above-mentioned standards and thus using a pickup sensor 5.

LIST OF REFERENCE CHARACTERS

[0052] 1 Cylinder [0053] 2 Test engine [0054] 3 Piston [0055] 4 Pressure sensor [0056] 5 Pickup sensor [0057] 6 Evaluation unit [0058] 7 Detonation meter [0059] 8 Knock meter