CN110500202B - Method for automatically searching combustion termination time of solid rocket engine - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 35
- 239000007787 solid Substances 0.000 title claims abstract description 18
- 238000009795 derivation Methods 0.000 claims abstract description 24
- 238000004364 calculation method Methods 0.000 claims abstract description 9
- 238000010606 normalization Methods 0.000 claims abstract description 3
- 238000004422 calculation algorithm Methods 0.000 claims description 11
- 238000012545 processing Methods 0.000 abstract description 17
- 238000012360 testing method Methods 0.000 abstract description 10
- 239000003380 propellant Substances 0.000 abstract description 4
- 238000013461 design Methods 0.000 abstract description 3
- 238000002474 experimental method Methods 0.000 abstract 1
- 238000011282 treatment Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02K—JET-PROPULSION PLANTS
- F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
- F02K9/08—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using solid propellants
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02K—JET-PROPULSION PLANTS
- F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
- F02K9/96—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof characterised by specially adapted arrangements for testing or measuring
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Abstract
The invention provides a method for automatically searching combustion termination time of a solid rocket engine, which comprises the steps of firstly obtaining an actual pressure-time curve of a propellant combustion speed test of the solid rocket engine, secondly carrying out normalization processing on a pressure value P according to time, then determining the interval step length of differential derivation, carrying out derivation calculation on transformed pressure point by point backwards to obtain a first derivative and a second derivative, further obtaining the curvature of each point in the transformed pressure curve, and calculating the combustion time by using the time point corresponding to the maximum curvature. The method provided by the invention can be used as a substitute method of a manual double tangent method to be applied to a solid rocket engine propellant burning rate test experiment, realizes automatic data processing, improves the data processing efficiency, ensures the repeatability of processing results, avoids processing errors caused by human factors, obtains the burning time closer to the design parameters in value, and has more accurate processing results.
Description
Technical Field
The invention belongs to the technical field of solid rocket engine testing, and particularly relates to a method for automatically searching combustion termination time of a solid rocket engine.
Background
In the test process of the solid rocket engine, the combustion time is the calculation basis of ballistic parameters such as the combustion speed, the average pressure, the average thrust, the characteristic speed and the like of the solid rocket engine, and at present, a double tangent method is mainly used to determine the termination time point of the combustion of the engine in practice, and the method specifically comprises the following steps: and respectively making two tangent lines of the stable section and the descending section of the pressure curve, and taking the intersection point of the angular bisector of the two tangent lines and the pressure curve as the termination time point of the combustion of the engine. However, the currently used double tangent method does not clearly define the stable section and the descending section of the curve, manual judgment and tangent drawing are needed, the influence of human factors is large, the repeatability of processing results is poor, and the accuracy is low. Even the same person, multiple treatments at different times will yield different results.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for automatically searching the combustion termination time of a solid rocket engine.
The technical scheme of the invention is as follows:
the method for automatically searching the combustion termination time of the solid rocket engine is characterized by comprising the following steps: the method comprises the following steps:
step 1: scanning and collecting a pressure signal P of an engine combustion chamber at the rate of n points/second to obtain a moment point T0 of an ignition signal, a maximum pressure value Pmax, a corresponding moment point tPMax and a working end moment ta;
step 2: normalizing the pressure value P in the time range [ tPMax, ta ] according to the time, wherein the normalization formula is as follows:
PBH＝P*((ta-tPmax)/Pmax)+tPmax
obtaining a transformed pressure PBH；
And step 3: determining an interval step length delta T ═ (ta-T0) × k of differential derivation;
and 4, step 4: starting from tPmax, the interval step length of delta t is used for the transformed pressure PBHAt [ tPMax, ta- Δ t]Carrying out derivation calculation backward point by point to obtain a first derivative P', wherein data obtained by backward derivation at the time t is used as a first derivative value at the time t + delta t/2 of the middle point of the corresponding interval step; the time range corresponding to the first derivative P' is [ tPMax + delta t/2, ta-delta t/2]The derivation algorithm is:
P’＝(PBH(t+Δt)-PBH(t))/Δt
and 5: calculating the first derivative P ' obtained in the step 4 point by taking the delta t as an interval step length to obtain a second derivative P ', wherein the time range corresponding to the P ' is [ tPMax + delta t, ta-delta t ];
step 6: according to the first derivative P 'calculated in step 4 and the second derivative P' calculated in step 5, according to the formula K ═ P '/(1 + P'2)3/2Calculation of [ tPmax, ta]In time range PBH-curvature K of each point in the t-curve and obtaining a time point tKmax corresponding to the maximum value of curvature;
and 7: the combustion time tb-tKmax-T0 is obtained.
In a further preferred aspect, the method for automatically finding the combustion termination time of a solid rocket engine is characterized in that: the value range of k in step 3 [ 2%, 3% ].
In a further preferred aspect, the method for automatically finding the combustion termination time of a solid rocket engine is characterized in that: the method for determining the engine operation end time ta is as follows: the time point corresponding to the last pressure value of more than 300kPa in the pressure signal P is taken as ta.
Advantageous effects
The method for automatically searching the combustion termination time of the solid rocket engine can be used as a substitute method of an artificial double tangent method to be applied to a solid rocket engine propellant combustion speed test. Compared with the currently commonly used manual double tangent method, the method has the following advantages:
1. automatic data processing is realized, and the data processing efficiency is improved;
2. the repeatability of the processing result is ensured, and the processing error caused by human factors is avoided;
3. the combustion time obtained by the treatment is closer to the design parameters in value, and the treatment result is more accurate.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1: an original pressure curve within a given interval;
FIG. 2: a pressure curve within the transformed given interval;
FIG. 3: the pressure signal curve of the combustion chamber of the engine collected in the embodiment;
FIG. 4: the pressure curve in the original given interval in the embodiment;
FIG. 5: the pressure curve in the given interval after the transformation in the embodiment;
FIG. 6: a schematic diagram of the curvature K is calculated point by point.
Detailed Description
The invention provides a method for automatically searching the combustion termination time of a solid rocket engine, which has the overall thought that: firstly, determining an interval for calculating the combustion termination time; then, normalizing the pressure intensity and time curve; then, a time step is given, differential derivation is carried out from the initial position (the time point corresponding to the maximum pressure of the stable section) of the determined interval point by point and every other time step backwards, the curvature at the position is calculated, and the position with the maximum curvature is taken as the combustion termination time point.
The invention has two more key technical points:
1) the pressure values in a given interval (vertical axis) are normalized by time (horizontal axis). The interval selected by the invention is from the maximum value of the stable section of the pressure curve to the working end time of the engine at the descending section (generally, the time point corresponding to the pressure descending to 300 kPa). Since the vertical axis of the data processing curve represents pressure values, the magnitude of which is typically 10 with respect to time (horizontal axis)3As shown in fig. 1, if the curvature is calculated by derivation according to the actual physical quantity, the calculation results are all in a large quantity value, and it is not convenient to perform accurate comparison to obtain the maximum value. Therefore, in the present invention, the vertical axis in the interval is converted in equal proportion to the horizontal axis so that the ranges of the vertical axis and the horizontal axis are completely the same, as shown in fig. 2. The specific algorithm is as follows:
PBH＝P*((ta-tPmax)/Pmax)+tPmax (1)
wherein: pBHIs a transformed pressure point value; p is an actual pressure point value; ta is the time point when the engine finishes working; tPmax is a time point corresponding to the maximum pressure of the stationary section; pmax is the maximum plateau pressure.
2) The step size of the differential derivation is determined. The key of the differential derivation of each interval step length after point-by-point is that a proper interval step length is determined, the interval step length has great influence on the determination of the accurate maximum curvature position, and results obtained by the step length being too short or too long are greatly different from results obtained by the conventional experienced operators by adopting a double tangent method. According to a large amount of engine test data verification, the effect of selecting 2% -3% of the engine test working time as the derivation step length is the best.
The specific technical scheme is as follows:
and scanning and acquiring a pressure signal P of the combustion chamber of the engine at the speed of n points/second, wherein the time point of an ignition signal is T0, the maximum value of the acquired pressure is Pmax, the corresponding time point is tPMax, and the time point of the termination of work is ta.
The specific process for automatically calculating the combustion termination time tb by using the algorithm comprises the following steps:
1. according to the obtained maximum pressure value Pmax, corresponding to the time point tPMax and the working end time ta, the calculation range is determined to be [ tPMax, ta ], and the pressure-time curve is shown in figure 1. The method for determining the engine work end time ta comprises the following steps: the time point corresponding to the last pressure signal greater than 300kPa is taken as ta.
2. Will [ tPMax, ta]The pressure value P in the range is normalized according to time, the specific algorithm is shown in formula (1), and the transformed pressure-time curve PBH-t is shown in figure 2.
3. And determining the interval step length delta T of differential derivation as (ta-T0) × k, k as [ 2%, 3% ], and the corresponding pressure point number dot as delta T × n.
4. Starting from tPMax, taking delta t as interval step length, and carrying out P conversionBHT is at [ tPMax, ta- Δ t [ ]]Inner point-by-point backward derivationCalculating to obtain a first derivative P', wherein data obtained by backward derivation at the time t is used as a first derivative value at the time of the midpoint t + delta t/2 of the corresponding step interval; the time range corresponding to the first derivative P' is [ tPMax + delta t/2, ta-delta t/2]The derivation algorithm is:
P’＝(PBH(t+Δt)-PBH(t))/Δt (2)
5. and (4) calculating the first derivative P ' point by point according to the interval step length of delta t to obtain a second derivative P ', wherein the time range corresponding to P ' is [ tPMax + delta t, ta-delta t ], and the method is the same as the step 4.
6. According to the formula (3), [ tPMax, ta ] is calculated]Within range PBH-curvature K of the t-curve and obtaining the point in time tKmax corresponding to the maximum of the curvature.
K＝P”/(1+P’2)3/2 (3)
7. The burning time was obtained as follows:
tb＝tKmax-T0 (4)
the following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.
The engine combustion chamber pressure signal P was sampled at a sampling rate of 2000 points/second with the ignition signal timing point T0 being 9.1810s, as shown in fig. 3 below. The flow for automatically acquiring the combustion time tb by applying the algorithm is as follows:
1. the maximum pressure Pmax is 7240.11kPa, the corresponding time point tPmax is 10.6440s, the end time point ta is 13.0770s, the calculation time range is determined to be [10.6440, 13.0770], and the pressure curve in the interval is shown in fig. 4.
2. Time range [10.6440, 13.0770]]The internal pressure value P is normalized to be PBHThe transformed curve is shown in fig. 5;
PBH＝P*((13.0770-10.6440)/7240.11)+10.6440 (5)
3. the interval step Δ t of differential derivation is selected to be (13.0770-9.1810) × 0.024 ═ 0.094s, and the corresponding pressure point number dot is selected to be 0.0935 × 2000 ═ 188.
4. From10.6440s, starting with 0.094s as a step size, for P after transformationBHCalculating the derivation of the curve point by point backwards to obtain a first derivative P', wherein the derivation time intervals are [10.6440, 10.7380 ] in sequence]、[10.6445，10.7385]、[10.6450，10.7390]…[12.983，13.0770]The time points corresponding to P' are 10.6910s, 10.6915s and 10.6920s … 13.0300s in sequence.
Taking P' corresponding to 10.6910s as an example, the specific algorithm is shown in formula (6):
P’[10.6910]＝(PBH[10.7380]-PBH[10.6440])/(10.7380-10.6440) (6)
5. and (3) carrying out derivation calculation on the first-order derivative P ' point by point in a time range [10.6910,13.0300], wherein derivation time intervals are [10.6910, 10.7850], [10.6915, 10.0785], [10.6920, 10.0790] … [12.9360 and 13.0300] in sequence, so as to obtain a second-order derivative P ', and the corresponding time points of P ' are 10.7380s, 10.7385s and 10.7390s … 12.9830s in sequence.
6. The curvature K is calculated point by point, and as shown in fig. 6, the maximum curvature value is 51.949, and the acquisition time value corresponding to this point is 4070/2000+10.7380 ═ 12.7730 s.
7. The burning time tb is 12.7730-9.1810 ═ 3.5920 s.
The combustion time of the engine test can be automatically obtained by adopting the algorithm, and after a large amount of verification, when the step length of the derivation interval is 2% -3% of the working time of the engine test, the difference value between the processing result of the combustion time algorithm which is automatically obtained and the result of an experienced operator adopting a manual double tangent method is basically within 30ms, so that the algorithm can be used as a substitute method of the manual double tangent method to be applied to the propellant combustion speed test. Compared with the currently commonly used manual double-tangent method, the method has the following advantages:
1. automatic data processing is realized, and the data processing efficiency is improved;
2. the repeatability of the processing result is ensured, and the processing error caused by human factors is avoided;
3. the combustion time obtained by the treatment is closer to the design parameters in value, and the treatment result is more accurate.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (2)
1. A method for automatically searching the combustion termination time of a solid rocket engine is characterized by comprising the following steps: the method comprises the following steps:
step 1: scanning and collecting pressure signals P of the combustion chamber of the engine at the speed of n points/second to obtain ignition signal time points T0Maximum value of pressure PmaxCorresponding to the time point tPmaxAnd the end time t of the worka；
Step 2: will time range tPmax，ta]The pressure value P in the pressure sensor is normalized according to time, and the normalization formula is as follows:
PBH＝P*((ta-tPmax)/Pmax)+tPmax
obtaining a transformed pressure PBH；
And step 3: determining the interval step Δ t of the differential derivation as (t)a-T0) K; the value range of k is [ 2%, 3%]；
And 4, step 4: from tPmaxAt first, the transformed pressure P is measured by taking delta t as interval step lengthBHAt [ t ]Pmax，ta]Carrying out derivation calculation backward point by point to obtain a first derivative P', wherein data obtained by backward derivation at the time t is used as a first derivative value at the time t + delta t/2 of the middle point of the corresponding interval step; the first derivative P' corresponds to a time range tPmax+Δt/2，ta-Δt/2]The derivation algorithm is:
P’＝(PBH(t+Δt)-PBH(t))/Δt
and 5: and (4) calculating the first derivative P ' obtained in the step (4) point by taking delta t as interval step length to obtain a second derivative P ', wherein the time range corresponding to P ' is [ tPmax+Δt，ta-Δt]；
Step 6: according to the first derivative P 'calculated in step 4 and the second derivative P' calculated in step 5, according to the formula K ═ P '/(1 + P'2)3/2Calculate [ t ]Pmax，ta]In time range PBH-curvature K of each point in the t-curve, and obtaining the time point t corresponding to the maximum value of curvatureKmax；
And 7: obtaining a combustion time tb＝tKmax-T0。
2. The method of automatically finding the combustion termination time of a solid rocket engine according to claim 1, wherein: determining the end of engine operation time taThe method comprises the following steps: taking the time point corresponding to the last pressure value greater than 300kPa in the pressure signal P as ta。
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