CN111894781B - Test method for judging maximum lift of needle valve - Google Patents
Test method for judging maximum lift of needle valve Download PDFInfo
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- CN111894781B CN111894781B CN202010613461.1A CN202010613461A CN111894781B CN 111894781 B CN111894781 B CN 111894781B CN 202010613461 A CN202010613461 A CN 202010613461A CN 111894781 B CN111894781 B CN 111894781B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
- F02M65/005—Measuring or detecting injection-valve lift, e.g. to determine injection timing
Abstract
The invention provides a test method for judging the maximum lift of a needle valve, which comprises the following steps: A. for common rail injector at different pressures p and different pulse widths tcLower cycle fuel injection quantity v, fuel injection duration t and fuel injection opening delay toAnd multi-cycle injection quantityStandard deviation sigmavCarrying out a first round of test; B. shortening the pulse width tcInterval, cyclic fuel injection quantity v and pulse width tcThe relationship curve has an inflection point, and the multi-cycle fuel injection standard deviation sigma is combinedvThe maximum needle valve lift L is judged according to the variation trend ofmaxCorresponding pulse width tcThe interval range of (a); C. the common rail oil injector is disassembled and inspected, the maximum needle valve lift L is adjusted, the common rail oil injector is reassembled, and a second round of test is carried out; D. calculating the pressure p and the pulse width t of the same pressure chamber in the two-wheel testcLower cycle fuel injection quantity change rate etavDetermining the maximum needle lift L for the first runmaxCorresponding pulse width tc. The invention has the beneficial effects that: and conventional test data are fully utilized, the influence of the maximum needle valve lift is analyzed, and the test cost is reduced.
Description
Technical Field
The invention belongs to the field of performance analysis of common rail injectors of diesel engines, and particularly relates to a test method for judging the maximum lift of a needle valve.
Background
The maximum needle valve lift is a key parameter in the design process of the common rail fuel injector, and has influence on the magnitude of the circulating fuel injection quantity and the fuel injection stability. The maximum needle valve lift is designed to be too small, the throttling effect on the seat surface of the fuel injection nozzle matching part is increased, the fuel injection pressure loss is increased, and the improvement of the circulating fuel injection quantity is not facilitated. On the contrary, the maximum needle valve lift is designed to be too large, the needle valve cannot reach the maximum value in the actual oil injection process, and meanwhile due to the influence of pressure, the closing strokes of the needle valves are inconsistent, the closing delay of the needle valves is inconsistent, and the standard deviation of the oil injection quantity of multiple cycles is increased. Therefore, an optimal design of the maximum needle lift design value is required.
The maximum needle valve lift can be optimally designed by using a simulation means, but a simulation model needs to acquire a relevant curve of the needle valve lift in the oil injection process to calibrate the simulation precision. The needle valve lift test is difficult and poor in precision due to the limitation of the common rail fuel injector structure and test means. In order to improve the precision of the simulation model, the simulation model is generally calibrated by test curves such as pressure fluctuation, oil injection law and the like. And performing maximum needle valve lift optimization analysis by using the calibrated model. However, the fuel injection law curve needs a special instrument for testing, and the error of the test result relative to the cycle fuel injection quantity and the fuel injection opening delay is large, so that the maximum needle valve lift optimization analysis is influenced.
Disclosure of Invention
In view of this, the present invention provides a test method for determining a maximum lift of a needle valve, so as to analyze the maximum lift of the needle valve, reduce test cost, and improve analysis accuracy.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a test method for judging the maximum lift of a needle valve comprises the following steps:
A. carrying out a first round of test on the cyclic oil injection quantity v, the oil injection duration t, the oil injection opening delay to and the standard deviation sigma v of the multi-cyclic oil injection quantity of the common rail oil injector under different pressures p and different pulse widths tc;
B. shortening the interval of the pulse width tc, enabling an inflection point to appear on a relation curve of the cyclic fuel injection quantity v and the pulse width tc in the first round of test, and judging the interval range of the pulse width tc corresponding to the maximum needle valve lift Lmax by combining the variation trend of the standard deviation sigma v of the multi-cyclic fuel injection quantity;
C. after the first round of test is finished, the common rail oil atomizer is disassembled and inspected, the maximum needle valve lift L of the common rail oil atomizer is adjusted, the common rail oil atomizer is reassembled, and a second round of test is carried out according to the control parameters of the first round;
D. calculating the cyclic fuel injection quantity change rate eta v under the same pressure chamber pressure p and pulse width tc of the two-wheel test, generating a curve by the pulse width tc and the cyclic fuel injection quantity change rate eta v, determining the pulse width tc corresponding to the maximum needle valve lift Lmax of the first round by judging the change curve of the cyclic fuel injection quantity change rate eta v, and judging the time of the needle valve reaching the maximum lift under different pressures.
Further, in the step B, the maximum needle lift L of the common rail fuel injector is adjusted to be increased by 30-50%.
And further, before the second round of test, selecting three points of 20%, 30% and 40% of the circulation fuel injection amount of the calibration working condition to perform performance test under the same control parameter, recording the circulation fuel injection amount vt and the fuel injection opening delay to of the three points, calculating the circulation fuel injection amount change rate eta v and the opening delay change rate eta od before and after the lift adjustment of the needle valve, and performing the second round of test under the condition that the change rates of the circulation fuel injection amount change rate eta v and the opening delay change rate eta od are within a range of +/-5%, otherwise, reassembling the common rail fuel injector after the lift adjustment of the needle valve.
Further, the change rate of the circulating fuel injection quantity is,
ηv=（vt-v1）/v1×100，
v1 refers to the cyclic oil injection quantity measured by calibrating 20%, 30% and 40% of the cyclic oil injection quantity of the working condition in the first round of test;
vtafter a first round of test, adjusting the needle valve lift and reassembling the oil injector, and preparing to perform a second round of test with different pressures p and different pulse widths t c Before the next cyclic fuel injection amount test, the cyclic fuel injection amount measured by 20%, 30% and 40% of the cyclic fuel injection amount under the calibration working condition is selected;
the rate of change of the fuel injection opening delay is,
ηod=（tot-to1）/to1×100；
to1in the first test, the oil injection opening delay measured by 20%, 30% and 40% of the circulating oil injection quantity under the working condition is calibrated;
totafter a first round of test, adjusting the needle valve lift and reassembling the oil injector, and preparing to perform a second round of test with different pressures p and different pulse widths tcCirculation ofBefore the fuel injection quantity test, the fuel injection opening delay measured by 20%, 30% and 40% of the circulating fuel injection quantity under the calibration working condition is selected.
Compared with the prior art, the test method for judging the maximum lift of the needle valve has the following advantages:
the test method for judging the maximum lift of the needle valve overcomes the problem that the lift of the needle valve cannot be directly measured, and improves the simulation precision by using test data with relatively small errors in the test; and conventional test data are fully utilized, the influence of the maximum needle valve lift is analyzed, and the test cost is reduced.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows the cyclic oil injection amount under different pressures and different pulse widths in a first round of the present invention;
FIG. 2 is a graph comparing the variation rate of the fuel injection amount and the fuel injection opening delay of the present invention;
FIG. 3 is a standard deviation of fuel injection quantity for the first cycle of the present invention;
FIG. 4 is a diagram showing the variation rate of the fuel injection amount in two cycles;
FIG. 5 is a comparison of fuel injection for two cycles of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. A test method for judging the maximum lift of a needle valve comprises the following steps:
A. for the circulating oil injection quantity v and the oil injection duration of the common rail oil injector under different pressures p and different pulse widths tc
Carrying out a first round of test on the duration t, the fuel injection opening delay to and the standard deviation sigma v of the multi-cycle fuel injection quantity;
B. shortening the interval of the pulse width tc, wherein an inflection point appears on a relation curve of the cyclic fuel injection quantity v and the pulse width tc in a first round of test, the interval range of the pulse width tc corresponding to the maximum needle valve lift Lmax is judged by combining the variation trend of the standard deviation sigma v of the multi-cyclic fuel injection quantity, the interval of the pulse width tc is reduced, the sample quantity of performance test data is increased, and the inflection point of the relation curve of the cyclic fuel injection quantity v and the pulse width tc is more definite;
C. after the first round of test is finished, the common rail oil atomizer is disassembled and inspected, the maximum needle valve lift L of the common rail oil atomizer is adjusted, the common rail oil atomizer is reassembled, and a second round of test is carried out according to the control parameters of the first round;
D. calculating the cyclic fuel injection quantity change rate eta v under the same pressure chamber pressure p and pulse width tc of the two-wheel test, generating a curve by the pulse width tc and the cyclic fuel injection quantity change rate eta v, determining the pulse width tc corresponding to the maximum needle valve lift Lmax of the first round by judging the change curve of the cyclic fuel injection quantity change rate eta v, and judging the time of the needle valve reaching the maximum lift under different pressures.
And B, adjusting the maximum needle valve lift L of the common rail oil sprayer to increase by 30-50%.
And B, before the second round of test, selecting 20 percent of the rated working condition circulating fuel injection quantity,
Performing performance test on 30% and 40% of three points under the same control parameters, and recording the circulating fuel injection quantity of the three points
vt and fuel injection opening delay to, calculating the cyclic fuel injection quantity change rate eta v and the opening delay change rate eta od before and after the lift adjustment of the needle valve, and carrying out a second round of test under the condition that the change rates of the cyclic fuel injection quantity change rate eta v and the opening delay change rate eta od are within the range of +/-5%, otherwise, reassembling the common rail fuel injector after the lift adjustment of the needle valve.
The change rate of the circulating fuel injection quantity is,
eta v = (vt-v 1)/v 1 x 100, the change rate of the fuel injection opening delay is,
ηod=（tot-to1）/to1×100。
in the step C, after the needle valve lift L reaches the maximum needle valve lift Lmax, the pressure pv of the pressure chamber tends to be stable, and meanwhile, the closing strokes of the needle valves are consistent, so that the consistency of the closing delay tcd of the needle valves is improved, the consistency of the oil injection duration is improved, the consistency of multi-cycle oil injection quantity is improved, and the standard deviation sigma v of the multi-cycle oil injection quantity is reduced; after the needle valve lift L reaches the maximum needle valve lift Lmax, the pressure pv of the pressure chamber tends to be stable, the increase factor of the cyclic oil injection quantity v only remains one factor of the oil injection duration t, the turning point of a relation curve of the cyclic oil injection quantity v and the pulse width tc appears by shortening the interval of the pulse width tc in the test control parameter, and the interval range of the pulse width tc corresponding to the maximum needle valve lift Lmax can be judged by combining the variation trend of the standard deviation σ v.
One specific example is given below:
as shown in figure 1, the performance test system of the common rail injector is used for completing the test of 60MPa of the common rail injector,
The average cycle fuel injection quantity performance test of 100 times of tests is carried out on each point under 21 pulse widths of 300us, 325us and 350us … … 800us under four pressures of 100MPa, 140MPa and 180MPa, and the test results show that: when the pressure is 60MPa, the increment of the circulating fuel injection quantity is not reduced, which shows that the maximum lift of the fuel injector is not reached under the pressure of 60MPa and the pulse width of 800 us; when the pressure is 100MPa, the increment of the circulating fuel injection quantity is reduced at about 700us, and the control pulse width corresponding to the range of the inflection point interval of the increment of the circulating fuel injection quantity is advanced along with the increase of the pressure.
As shown in fig. 2, the cycle fuel injection amount and the fuel injection opening delay change rate are compared before the second round of test. Adjusting the maximum needle valve lift parameter of the oil injector, increasing the maximum needle valve lift parameter from 0.5mm to 0.7mm, then selecting three points of 20%, 30% and 40% of the circulating oil injection amount under the calibration working condition to perform performance tests under the same control parameters, recording the circulating oil injection amount vt of the three points as 49.97mm3, 74.06mm3 and 101.55mm3 respectively, recording the circulating oil injection amount v1 of the three points corresponding to the first round as 49.47mm3, 72.24mm3 and 101.74mm3 respectively, and calculating the circulating oil injection amount conversion rate eta v of the three points as follows through a formula eta v = (vt-v 1)/v 1 multiplied by 100
1%, 2.46%, -0.19%. Recording the fuel injection opening delays tot of three points as 402.31us,
407.62us and 409.04us, the fuel injection opening delays to1 of three points corresponding to the first round are respectively
403.87us, 417.32us, 418.14 us. Delay to rate of change η od = (tot-to 1) by fuel injection opening
The opening delay change rates η od of the three points are calculated to be-0.39%, -2.32%, -2.18%, respectively, by/to 1 × 100. And (5) counting the change rates of the cyclic fuel injection quantity conversion rate eta v and the opening delay change rate eta od within the range of +/-5%, and starting a second round of test.
As shown in FIG. 3, data arrangement is carried out by taking the pulse width tc as the X coordinate and the standard deviation sigma v of the circulating fuel injection quantity for 100 times as the Y coordinate, and the arrangement result shows that when the pressure p is 60MPa, the standard deviation sigma of the circulating fuel injection quantity is
Vmax corresponds to between 700us and 725 us. And when the pressure is 100MPa, the maximum value of the standard deviation sigma v of the circulating fuel injection quantity is between 700us and 725 us. And when the pressure is 140MPa, the maximum value of the standard deviation sigma v of the circulating fuel injection quantity is between 575us and 600 us. Corresponding to maximum value of standard deviation sigma v of circulating fuel injection quantity at 180MPa
550us and 575 us.
As shown in fig. 4, the data processing is performed by using the pulse width tc as the X coordinate, the same pressure p in two tests, and the change rate η v of the cyclic fuel injection amount v under the pulse width tc as the Y coordinate. For example, when the pressure is 180MPa and the pulse width is 575us, the oil injection quantity v of the first round of circulation is 150.65mm3, the oil injection quantity v of the second round of circulation is 150.5mm3, and the eta is 0.1%, when the pressure is 180MPa and the pulse width is 600us, the oil injection quantity v of the first round of circulation is 171.92mm3, the oil injection quantity v of the second round of circulation is 165.35mm3, and the eta is 3.82%. Specific control pulse widths corresponding to "inflection points" of the change rate η v of the fuel injection amount of the two-cycle under three pressures of 100MPa, 140MPa and 180MPa can be obtained through the graph 4, for example, the control pulse widths of the "inflection points" under 100MPa, 140MPa and 180MPa are 725us, 650us and 575us, which means that the needle lift L reaches the maximum needle lift Lmax under the pulse widths.
As shown in fig. 5, the data processing is performed by using the pulse width tc as the X coordinate, the same pressure p in two tests, and the cyclic fuel injection amount v under the pulse width tc as the Y coordinate. After the needle valve lift L is increased in the second round under the same pulse width tc, the cyclic fuel injection quantity v is increased, which indicates that the maximum needle valve lift Lmax designed in the first round is smaller.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. A test method for judging the maximum lift of a needle valve is characterized by comprising the following steps:
A. carrying out a first round of test on the cyclic oil injection quantity v, the oil injection duration t, the oil injection opening delay to and the standard deviation sigma v of the multi-cyclic oil injection quantity of the common rail oil injector under different pressures p and different pulse widths tc;
B. shortening the interval of the pulse width tc, enabling an inflection point to appear on a relation curve of the cyclic fuel injection quantity v and the pulse width tc in the first round of test, and judging the interval range of the pulse width tc corresponding to the maximum needle valve lift Lmax by combining the variation trend of the standard deviation sigma v of the multi-cyclic fuel injection quantity;
C. after the first round of test is finished, the common rail oil atomizer is disassembled and inspected, the maximum needle valve lift L of the common rail oil atomizer is adjusted, the common rail oil atomizer is reassembled, and a second round of test is carried out according to the control parameters of the first round;
D. calculating the cyclic fuel injection quantity change rate eta v under the same pressure chamber pressure p and pulse width tc of the two-wheel test, generating a curve by the pulse width tc and the cyclic fuel injection quantity change rate eta v, determining the pulse width tc corresponding to the maximum needle valve lift Lmax of the first round by judging the change curve of the cyclic fuel injection quantity change rate eta v, and judging the time of the needle valve reaching the maximum lift under different pressures.
2. The test method for judging the maximum lift of the needle valve according to claim 1, wherein: and B, adjusting the maximum needle valve lift L of the common rail oil sprayer to increase by 30-50%.
3. The test method for judging the maximum lift of the needle valve according to claim 1, wherein: and B, before the second round of test, selecting 20 percent of the rated working condition circulating fuel injection quantity,
Performing performance test on 30% and 40% of three points under the same control parameters, and recording the circulating fuel injection quantity of the three points
vt and fuel injection opening delay to, calculating the cyclic fuel injection quantity change rate eta v and the opening delay change rate eta od before and after the lift adjustment of the needle valve, and carrying out a second round of test under the condition that the change rates of the cyclic fuel injection quantity change rate eta v and the opening delay change rate eta od are within the range of +/-5%, otherwise, reassembling the common rail fuel injector after the lift adjustment of the needle valve.
4. The test method for judging the maximum lift of the needle valve according to claim 3, wherein the test method comprises the following steps: the change rate of the circulating fuel injection quantity is,
ηv=（vt-v1）/v1×100，
v1 refers to the cyclic oil injection quantity measured by calibrating 20%, 30% and 40% of the cyclic oil injection quantity of the working condition in the first round of test;
vtafter a first round of test, adjusting the needle valve lift and reassembling the oil injector, and preparing to perform a second round of test with different pressures p and different pulse widths tcBefore the next cyclic fuel injection amount test, the cyclic fuel injection amount measured by 20%, 30% and 40% of the cyclic fuel injection amount under the calibration working condition is selected;
the rate of change of the fuel injection opening delay is,
ηod=（tot-to1）/to1×100；
to1in the first test, the oil injection opening delay measured by 20%, 30% and 40% of the circulating oil injection quantity under the working condition is calibrated;
totafter a first round of test, adjusting the needle valve lift and reassembling the oil injector, and preparing to perform a second round of test with different pressures p and different pulse widths tcBefore the next cyclic fuel injection quantity test, the fuel injection opening delays measured by 20%, 30% and 40% of the cyclic fuel injection quantity under the calibration working condition are selected.
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