A rotating detonation engine ignition process online detection method based on rolling frequency measurement

Abstract

The application provides an online detection method for the ignition process of a rotary detonation engine based on rolling frequency measurement. The ignition of the rotary detonation engine has uncertainty, irregularity and transition, and the accurate and rapid judgment of the ignition state seriously affects the efficiency and reliability of the control system. The method regulates the irregular high-frequency pressure signal generated by the circumferential movement of the detonation wave head into a regular square wave signal through an analog circuit, combines a software program to rollingly collect the pulse number in a fixed time window, calculates the rotation frequency of the detonation wave head in the current time window through the frequency measurement method, and compares the measured frequency in the continuous time window with the set threshold to determine whether the ignition process is completed. The method uses an analog circuit to process the pressure signal, does not need to sample the pressure signal at high speed, calculates the signal frequency in the continuous time window through rolling frequency measurement, avoids false detection, has real-time and accuracy, and solves the problem of online detection of the ignition process of the rotary detonation engine.

Description

Technical Field

[0001] This invention relates to an online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement, belonging to the field of aero-engine control. Based on this method, the initiation process of a rotating detonation engine can be accurately and timely captured and judged. Background Technology

[0002] Currently, most aerospace propulsion systems, including turbine engines and ramjet engines, still primarily employ conventional isobaric combustion. While the development of these engines has matured, significant improvements in their propulsion efficiency are extremely difficult due to limitations imposed by the Brayton cycle efficiency and material structure inherent in isobaric combustion. Therefore, detonation engines with near-isochoric combustion have become a research hotspot in hypersonic propulsion systems.

[0003] As one of the most important types of detonation engines, the rotating detonation engine offers advantages over pulse detonation engines, including higher detonation wave rotation frequency, stable thrust, smaller axial combustion chamber size, the ability to achieve continuous detonation combustion with only a single ignition, and lower dependence on the ignition system. Compared to oblique detonation engines, it has lower requirements for incoming air velocity, can operate over a wider Mach range, and is more feasible under current technological conditions. Therefore, the rotating detonation engine has become a widely discussed type of detonation engine in recent years.

[0004] In traditional aerospace propulsion system control logic, detecting pressure fluctuations within the combustion chamber is typically unnecessary because successful ignition is readily apparent. However, due to the unique characteristics of rotating detonation combustion, simple ignition checks are insufficient to determine successful detonation. Based on the circumferential motion of the detonation wavefront, pressure sensors / ion probe-type pressure sensors positioned at appropriate locations periodically detect pressure pulsations. This high-frequency, periodic pressure fluctuation within the combustion chamber is a crucial indicator of whether rotating detonation combustion is underway. For aerospace engines, their flight envelope spans speed and space. To ensure safe and stable operation across the entire envelope, the control system employs various control algorithms to achieve full-process engine control, including the detection and feedback control of key characteristics of rotating detonation combustion. Therefore, it is necessary to develop corresponding functions tailored to the characteristics of rotating detonation to calculate the circumferential motion frequency of the detonation wavefront, thereby aiding in the determination of successful rotating detonation combustion.

[0005] With existing technology, the success of rotating detonation engine bench tests often requires on-site judgment by test personnel based on phenomena and experience. To more accurately determine the detonation status, test personnel typically save the pressure sensor signals inside the combustion chamber and determine the success of the detonation by processing the pressure offline. While this approach can help determine the success of tests in the early stages of development, aerospace engine control systems are highly real-time systems, and offline judgment and processing can affect the efficiency and reliability of the control system. Therefore, there is an urgent need for an online detection method that can promptly and accurately determine the rotating detonation detonation status to support the development and verification of the control system. Summary of the Invention

[0006] The technical problem this invention aims to solve is to fill the existing technological gap by providing an online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement. This method processes high-frequency pressure signals within the combustion chamber without requiring high-frequency sampling and calculates the frequency of the circumferential rotation of the detonation wavefront, thereby determining whether the initiation process of rotating detonation has been completed. Specifically, this invention employs the following technical solutions to solve the above-mentioned technical problem:

[0007] An online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement specifically includes the following steps:

[0008] Step 1: The irregular high-frequency pressure signal generated by the pressure sensor at the corresponding measuring point in the combustion chamber by the circumferential motion of the knock wave head is modulated into a regular square wave signal through the analog circuit.

[0009] Furthermore, the analog circuit described in step 1 modulates the high-frequency pulsating signal of the pressure sensor in the combustion chamber into a regular high-frequency square wave signal through methods such as capacitor DC blocking, signal filtering, signal amplification, and hysteresis comparison.

[0010] Specifically, the analog circuit described in step 1 selects resistors of different sizes through a multiplexer, thereby changing the hysteresis comparison width to adapt to different pressure signals.

[0011] Step 2: Set the time window length t (ms) and collect the number of signal pulses N within the fixed time window. i ;

[0012] Furthermore, the time window mentioned in step 2 is a time length that is manually specified offline based on experience. This time length should not be too long, so as not to affect the real-time performance of the knock detection; nor should it be too short, so as not to affect the accuracy of the knock detection.

[0013] Furthermore, the signal mentioned in step 2 is the square wave signal output by the analog circuit in step 1, and the pulse count is acquired and counted by capturing the rising or falling edge through a program.

[0014] Step 3: Calculate the rotation frequency f of the implosion wavefront within the current time window using the frequency measurement method. i ,

[0015]

[0016] Furthermore, the frequency measurement method described in step 3 refers to measuring the number of counting pulses within a specified detection time. In this invention, the specified detection time is the set time window t, and the number of counting pulses is the number of pulses N in step 2.

[0017] Step 4: Set the frequency threshold F start and F fin The rotation frequency f of the detonation wavefront within the current time window. i Compare with a threshold;

[0018] Furthermore, the threshold F mentioned in step 4 start and F fin It is used to determine whether the detonation is in the transition process or has already been completed. The detonation of a rotating detonation engine has a certain transition process. At the beginning of detonation, the rotational speed of the detonation wavefront is being established, and the number of pulses collected is relatively small. Therefore, the threshold F is... start As the starting threshold, if the detonation wavefront rotation frequency f > F start If the threshold F is reached, it is considered that ignition has begun. fin To determine the initiation completion threshold, if the detonation wavefront rotation frequency is greater than f > F fin If the detonation wavefront rotation frequency F is [value missing], then it is considered that the detonation has been successfully initiated. start <f<F fin If so, it is considered to be in the detonation transition process. Preferably, in order to improve the success rate of online detection, the threshold F start and F fi n can be determined through multiple offline experiments.

[0019] Step 5: Collect the number of signal pulses for n time windows with a time interval of τ (ms), and repeat steps 3 and 4 to obtain the rotation frequencies f1, f2, ..., f of the implosion wavefront over n consecutive time windows. n The comparison with the set threshold;

[0020] Furthermore, the rolling acquisition mentioned in step 5 means that, assuming the current time window acquires the number of pulses within (j~j+t) ms, then the next acquisition will acquire the number of pulses within (j+τ~j+τ+t) ms, and so on.

[0021] Step 6: Based on f1, f2, ..., f nThe comparison with the set threshold is used to determine whether the rotary detonation engine ignition was successful. If the frequency of the signals collected in n time windows during rolling acquisition is greater than the ignition threshold F, the engine will ignite successfully. start If the signal frequency of the n time windows is within the threshold value F, it is considered that the detonation transition process has begun; further analysis is performed to determine the frequency of the signals within the n time windows relative to the detonation completion threshold F. fin The magnitude relationship, if both are greater than the detonation completion threshold F fin If the detonation is not greater than F, then the detonation is considered successful. fin It may be in the transition process or it may have already been successfully detonated. To ensure the accuracy of the detection, repeat steps 5 and 6.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] (1) High applicability: The analog circuit described in this invention uses a multi-channel switch to select the resistor value, thereby adjusting the hysteresis comparison width, allowing the signal conditioning analog circuit to condition different pulsating pressure signals. Subsequent signal acquisition, processing, and comparison only require setting an appropriate threshold based on the actual engine test conditions to complete the detection of detonation.

[0024] (2) High accuracy: The present invention sets two comparison thresholds and repeatedly verifies the frequency within a continuous time window by rolling collection and comparison, thus ensuring the accuracy of detection.

[0025] (3) Good real-time performance. This invention compares the signal frequency within multiple consecutive short time windows with a pre-set offline threshold to achieve online detection of the rotary detonation engine initiation process. Analog circuits are used to condition the high-frequency pressure signal from the sensor, and the number of pulses is counted by capturing the rising or falling edge, avoiding high-frequency sampling and offline processing of the signal, thus providing support for the development and fabrication of the control system. Attached Figure Description

[0026] Figure 1 Flowchart of the detection method for the initiation process of a rotating detonation engine;

[0027] Figure 2 For conditioning circuit of high-frequency pulsating pressure signal in rotary detonation combustion chamber;

[0028] Figure 3 This refers to the high-frequency pulsating pressure signal in the rotating detonation combustion chamber.

[0029] Figure 4 The square wave signal output by the high-frequency pulsating pressure signal conditioning circuit of the rotating detonation combustion chamber;

[0030] Figure 5 A partial diagram of the square wave signal output by the high-frequency pulsating pressure signal conditioning circuit of the rotating detonation combustion chamber; Detailed Implementation

[0031] To address the limitations of existing technologies in meeting the requirements for online detection of the detonation process of rotating detonation engines, this invention proposes an online detection method for the detonation process of rotating detonation engines based on rolling frequency measurement, utilizing analog circuits and rolling acquisition methods. The method involves modulating the irregular high-frequency pressure signal generated by the circumferential motion of the detonation wavefront into a regular square wave signal using analog circuits. Combined with software program rolling acquisition of the number of pulses within a fixed time window, the rotation frequency of the detonation wavefront within the current time window is calculated using frequency measurement. The completion of the detonation process is determined by comparing the frequencies measured over several consecutive time windows with a set threshold.

[0032] To facilitate public understanding, the technical solution of this invention will be described in detail below using a certain rotary detonation ramjet engine as an example.

[0033] Step 1: Through Figure 2 The analog circuit shown modulates the irregular high-frequency pressure signal generated by the pressure sensor at the corresponding measuring point in the combustion chamber through the circumferential motion of the knock wave head into a regular square wave signal.

[0034] Further, the analog circuit described in step 1 uses capacitor C4 to block the DC signal, uses R4, C6, R5, C7, etc. to perform RC filtering to remove noise signals, then uses an operational amplifier LM358 to amplify the signal, uses an LM393 for hysteresis comparison to condition the signal into a square wave signal, and finally uses a transistor to limit the square wave signal to a 0-3.3V square wave signal that the processor can acquire. Step 1 uses the high-frequency pulsating signal from the pressure sensor in the combustion chamber ( Figure 3 ) conditioned into a regular 0-3V high-frequency square wave signal ( Figure 4 , 5 );

[0035] Specifically, the analog circuit described in step 1 uses a 4-to-1 RS2255 multiplexer to select circuits with different resistance values, thereby adjusting the hysteresis width to adapt to different pressure signals and improve the versatility of the analog circuit.

[0036] Step 2: To balance real-time performance and accuracy, the acquisition time window length is set to t = 10ms, and the number of signal pulses N within the fixed time window is acquired;

[0037] Furthermore, the signal mentioned in step 2 is the square wave signal output by the analog circuit in step 1. Figure 4 The embedded program captures the number of pulses N=17 within the current time window (0-10ms) by capturing the rising edge of the pulse. Figure 5 As shown.

[0038] Step 3: Calculate the rotation frequency of the implosion shock wavefront within the current time window (0-10ms) using the frequency measurement method.

[0039] Step 4: Based on experimental data and experience, set the frequency threshold F. start =800Hz and F fin =1.5kHz. If the detonation wavefront rotation frequency f > 800Hz, ignition is considered to have begun. If the detonation wavefront rotation frequency is greater than f > 1.5kHz, detonation is considered to have been successfully initiated. If the detonation wavefront rotation frequency 800Hz < f < 1.5kHz, it is considered to be in the detonation transition process. Within the current time window, the detonation wavefront rotation frequency f1 = 1.7kHz > 1.5kHz.

[0040] Step 5: Collect the number of signal pulses for n time windows at time intervals of τ (ms), and repeat steps 3 and 4. In this example, the time interval τ = 5ms is set. The comparison between the rotation frequencies f1, f2, ..., f5 of the implosion wavefront over five consecutive time windows and the set threshold is shown in the table below.

[0041]

[0042]

[0043] Step 6: Based on f1, f2, ..., f n The comparison with the set threshold is used to determine whether the rotary detonation engine ignition was successful. In this example, the frequencies of the signals acquired over the five time windows are all greater than the ignition threshold F. start And all are greater than the detonation completion threshold F. fin They believed the detonation had been successful.

[0044] As described above, this invention effectively overcomes the shortcomings of existing control technologies by using analog circuits to process high-frequency pressure signals and measuring the frequency of the signal over a continuous time period through a rolling acquisition method, thereby determining the detonation state. The above are merely examples of specific embodiments of this invention, but the scope of protection of this invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this invention, based on the technical solution and inventive concept of this invention, should be covered within the scope of protection of this invention.

Claims

1. An online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement, characterized in that... Its detection method includes the following steps: (1) The irregular high-frequency pressure signal generated by the pressure sensor at the corresponding measuring point in the combustion chamber by the circumferential motion of the knock wave head is modulated into a regular square wave signal by the analog circuit. (2) Set the time window length t (ms) and collect the number of signal pulses N within the fixed time window. i ; (3) The rotation frequency f of the detonation wavefront within the current time window is calculated by frequency measurement method. i ; (4) Set the frequency threshold F start and F fin The rotation frequency f of the detonation wavefront within the current time window. i Compare with a threshold; (5) Collect the number of signal pulses in n time windows with a time interval of τ (ms), and repeat steps 3 and 4 to obtain the rotation frequencies f1, f2, ..., f of the implosion wavefront in n consecutive time windows. n The comparison with the set threshold; (6) Based on f1, f2, ..., f n The comparison with the set threshold is used to determine whether the rotary detonation engine was successfully ignited; if the frequency of the signals in the n time windows of the rolling acquisition is greater than the starting threshold F, the engine will be considered ignited successfully. start If the signal frequency of the n time windows is within the threshold value F, it is considered that the detonation transition process has begun; further analysis is performed to determine the frequency of the signals within the n time windows relative to the detonation completion threshold F. fin The magnitude relationship, if both are greater than the detonation completion threshold F fin If the detonation is not greater than F, then the detonation is considered successful. fin It may be in the transition process or it may have already been successfully detonated. To ensure the accuracy of the detection, repeat steps 5 and 6.

2. The online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement according to claim 1, characterized in that... The analog circuit described in step (1) modulates the high-frequency pulsating signal of the pressure sensor in the combustion chamber into a regular high-frequency square wave signal by means of capacitor DC blocking, signal filtering, signal amplification, and hysteresis comparison. The analog circuit described in step (1) selects resistors of different sizes through a multiplexer, thereby changing the hysteresis comparison width to adapt to different pressure signals.

3. The online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement according to claim 1, characterized in that... The time window mentioned in step (2) is a time length that is manually specified offline based on experience, taking into account real-time performance and accuracy.

4. The online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement according to claim 1, characterized in that... The threshold F mentioned in step (4) start and F fin The threshold F is used to determine whether the detonation is in the transition process or has been completed; start As the starting threshold, if the detonation wavefront rotation frequency f > F start If the threshold F is reached, it is considered that ignition has begun; fin The threshold for detonation completion is defined as follows: if the rotation frequency of the detonation wavefront is greater than f > F. fin If the detonation wavefront rotation frequency F is..., then it is considered that the detonation has been successfully initiated; start <f<F fin If it is, then it is considered to be in the detonation transition process; in order to improve the success rate of online detection, the threshold F start and F fin This was determined through multiple offline experiments.

5. The online detection method for the initiation process of a rotating detonation engine based on rolling frequency measurement according to claim 1, characterized in that... The rolling acquisition mentioned in step 5 means that, assuming the current time window acquires the number of pulses within (j to j+t) ms, the next acquisition will acquire the number of pulses within (j+τ to j+τ+t) ms, and so on.

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