Three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method

Abstract

The invention discloses an electrolytic preheating-electrolytic ignition method for a three-electrode hydroxylamine nitrate liquid propellant, and belongs to the field of liquid rocket engines and electrochemistry. Three electrolysis electrodes are arranged in the electrolysis chamber and comprise two positive electrodes and one negative electrode, so that two groups of electrolysis electrode pairs are formed. The method comprises the following steps: injecting a nitric acid hydroxylamine-based liquid propellant into an electrolysis chamber, and electrifying a group of electrolysis electrodes to start electrolysis preheating; after the preset switching time is up, closing the current working electrolysis electrode pair, and switching to another group of non-working electrolysis electrodes to continue electrolysis; and low-voltage and rapid electrolytic ignition is realized. According to the three-electrode electrolysis structure, the time for ignition and reaction to reach the highest temperature can be shortened, and the system response speed is increased; the preheating and ignition voltage can be changed, and the large voltage adjusting and optimizing space is achieved; meanwhile, the electrolytic ignition current is relatively stable, and the instantaneous power consumption is small; and electrolysis power consumption can be saved, electrolysis electrode loss is reduced, and reuse of the electrode is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of liquid rocket engine and electrochemistry, and particularly relates to a three-electrode hydroxylammonium nitrate-based liquid propellant electrolytic preheating-electrolytic ignition method. BACKGROUND

[0002] Hydroxylammonium nitrate (HAN) is a new generation of environmentally friendly low-freezing-point high-density green propellant, which is suitable as a substitute for traditional hydrazine-based propellant with high toxicity, and its specific impulse is equivalent to that of anhydrous hydrazine. The current mainstream ignition method of hydroxylammonium nitrate-based liquid propellant is catalytic ignition, but catalytic ignition has the following disadvantages: ① cannot cold start, and the catalytic bed needs to be preheated; ② the catalyst is deactivated, which leads to long ignition delay, high ignition difficulty, and poor reusability of catalytic ignition.

[0003] Based on the ionic liquid characteristics of hydroxylammonium nitrate-based propellant, electrolytic ignition can be performed, and an electric current is applied to generate an electrochemical reaction. Electrolytic ignition does not require a catalytic bed, has low ignition difficulty, short ignition delay, and strong reusability, but the traditional two-electrode electrolytic ignition still has the following disadvantages: ① when working at certain specific electrolytic electrode areas, it may cause a significant increase in electrolysis time; ② the power required for electrolysis, especially the instantaneous power, is high. SUMMARY

[0004] In order to overcome the above problems, the present application provides a three-electrode hydroxylammonium nitrate-based liquid propellant electrolytic preheating-electrolytic ignition method, which uses three electrodes for preheating and rapid ignition, and can effectively shorten the electrolytic ignition time.

[0005] The technical scheme of the present application is as follows: A three-electrode hydroxylammonium nitrate-based liquid propellant electrolytic preheating-electrolytic ignition method, comprising the following steps: Three electrolytic electrodes are arranged in the electrolysis chamber, including two positive electrodes and one negative electrode, and the electrolytic electrodes form two groups of electrolytic electrode pairs (sharing one negative electrode); After the hydroxylammonium nitrate-based liquid propellant is injected into the electrolysis chamber, electrolytic preheating is started by one group of electrolytic electrode pairs; When the preset switching time is reached, the currently working electrolytic electrode pair is turned off, and the electrolysis continues in the other group of non-working electrolytic electrodes (sharing the negative electrode with the first group of electrodes), and the fast-reading electrolytic ignition mode is started until the electrolytic ignition and combustion are completed, and the thrust is generated; Preferably, the effective area ratio of the positive electrode to the negative electrode of the electrolytic electrode is 0.5-2.0, and the length, width and thickness of the positive electrode and the negative electrode are freely adjusted as needed.

[0006] Preferably, the working voltage in the electrolysis step is adjustable in the range of 30V-150V.

[0007] Preferably, the electrolysis solution is a hydroxylammonium nitrate-based liquid propellant, comprising an aqueous solution of hydroxylammonium nitrate and a mixed liquid propellant composed of the same and a fuel.

[0008] Preferably, each set of electrolysis electrode pairs is driven by an independent control circuit, achieving time-sharing power-on and electrical isolation switching.

[0009] Preferably, the preset switching time is dynamically adjusted based on real-time feedback of electrolysis current or temperature.

[0010] Working principle analysis: In the traditional two-electrode low-voltage electrolysis ignition process, the chemical reactions occurring on the electrodes and in the solution can be roughly divided into three stages: Stage one: when the voltage is suddenly applied, the ions in the HAN solution (mainly including NO3 - , NH3OH + and H + ) are quickly attracted to the surface of the corresponding electrode, triggering a series of electrochemical reactions. These reactions include redox reactions occurring almost simultaneously on the negative and positive electrodes, causing both the current and the temperature to rise rapidly. On the positive side, oxygen evolution reaction occurs, which is a four-electron transfer process in an acidic environment. On the negative side, hydrogen evolution reaction and nitrate ion reduction reaction occur.

[0011] Stage two: due to the attractive effect of the positive electrode on anions, NO3 - ions gradually move to the positive electrode and cover the electrode surface, occupying active sites and reducing the positive electrode area participating in the reaction, resulting in inhibition of the oxygen evolution reaction on the positive side, causing the electrolysis current to decrease and the chemical reaction rate to decrease.

[0012] Stage three: after a long electrolysis process, the solution temperature rises to about 420K. At the same time, due to the reduction reaction of nitrate ions (NO3 - ) in stage two, more nitrite ions (NO2 - ) are produced, and the thermal decomposition reaction of HAN is finally triggered, forming electrolysis ignition.

[0013] As can be seen from the above reaction process, the adsorption of NO3 - ions on the positive electrode is the key factor leading to the decrease of electrolysis rate and the long electrolysis ignition time. Based on this, we designed an electrolysis preheating-electrolysis ignition device using three electrodes (sharing a negative electrode). Its advantage lies in that, during the electrolysis reaction in stage one and stage two, NO3 -Ions are adsorbed on the initially working positive electrode in large quantities; at this time, switch to another set of previously non-working electrodes (which can share the negative electrode with the first set of electrodes), at this time, the newly accessed positive electrode has not yet had NO3 - The adsorption of ions and the multiple reaction active sites can promote the electrolysis reaction to proceed quickly.

[0014] The present application has the beneficial effects of: The present application provides a low-voltage electrolysis preheating-electrolysis ignition method for hydroxylamine nitrate-based liquid propellant using three electrodes, introduces three electrodes to form reusable grouped electrode pairs, and uses an alternating switching mechanism, which takes advantage of the ionic liquid characteristics of hydroxylamine nitrate-based propellant, and has a larger voltage adjustment space while retaining the advantages of traditional electrolysis ignition, such as no catalytic preheating, short ignition delay, and strong repeatability. The time for the electrolysis reaction to reach the highest temperature is effectively shortened, the system response speed is greatly improved, the overall required instantaneous electrolysis power is reduced, and the electrode sheet reuse capability is improved, making the present application have important application value in scenarios such as aerospace propellers that require high frequency and high efficiency ignition. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of a propelling device according to an embodiment of the present application, wherein the mark A is Figure Two the cutting position of the cross-sectional view; Figure 2 is a cross-sectional view of the combustion chamber of the propelling device, showing the specific circumferential distribution of the three electrode sheets; in the figure: 1-palladium positive electrode A, 2-palladium positive electrode B, 3-stainless steel negative electrode, distributed at an interval of 120° along the circumference.

[0016] Figure 3 is a current-temperature-time change curve during the electrolysis preheating-electrolysis ignition process of the hydroxylamine nitrate liquid propellant using three electrodes according to an embodiment of the present application, wherein the solid black line in the figure is the current-temperature-time change curve of the electrolysis ignition of the hydroxylamine nitrate liquid propellant using the traditional double electrode, and the time required for electrolysis ignition is longer. DETAILED DESCRIPTION

[0017] The present application will be described in detail below in conjunction with the drawings and specific embodiments, but is not limited to the invention.

[0018] The present application provides a low-voltage electrolysis preheating-electrolysis ignition method for hydroxylamine nitrate-based liquid propellant using three electrodes, which sets three electrodes in the electrolysis chamber to form reusable electrode pairs, uses a time-sharing switching working mechanism, combines parameter optimization and control strategies, and realizes an efficient, low-power, and repeatable ignition process. The core of the present application lies in the synergistic effect of the multi-electrode structure and intelligent switching control, which significantly improves the electrolysis ignition performance.

[0019] (1) Electrode structure and layout Three electrolytic electrodes are installed in the electrolysis chamber, including a positive electrode (such as a platinum electrode) and a negative electrode (such as a stainless steel electrode). Different materials can be selected for the positive and negative electrodes to optimize electrolysis efficiency, depending on the requirements.

[0020] like Figure 1 and 2 As shown, the electrodes are distributed uniformly or non-uniformly along the circumference of the electrolysis chamber to ensure the uniformity of the electrolysis reaction and thermal management. For example, a 120° interval distribution can be used in a three-electrode system.

[0021] In this embodiment, the effective area ratio of the positive electrode to the negative electrode is controlled between 0.5 and 2.0. The length, width and thickness of the electrodes can be freely adjusted according to the electrolysis requirements to match the characteristics of different propellants.

[0022] (2) Electrolysis chamber and propellant injection The electrolysis chamber is designed as a sealed container with an electrode fixing structure and a liquid inlet for injecting hydroxylamine nitrate-based liquid propellant, such as a 70% hydroxylamine nitrate solution.

[0023] After the hydroxylamine nitrate liquid propellant is injected into the electrolysis chamber, the electrolysis process is started through the control system.

[0024] (3) Electrode grouping and reuse mechanism, switching control The electrodes are divided into two groups of electrode pairs (e.g., one group consists of platinum electrode A and a stainless steel electrode, and the other group consists of platinum electrode B and a stainless steel electrode). Different groups of electrode pairs can reuse the same electrode, such as using the stainless steel electrode as a common negative electrode. Each group of electrode pairs is controlled by an independent circuit to achieve electrical isolation and time-sharing energization.

[0025] After electrolysis is started, one set of electrode pairs works first, such as platinum electrode A and stainless steel electrode. After the preset switching time is reached (e.g., t1=10s), the current electrode pair is turned off and switched to another set of non-working electrode pairs, such as platinum electrode B and stainless steel electrode, to continue electrolysis.

[0026] In one specific embodiment of the present invention, the switching time can be dynamically adjusted based on real-time feedback, such as current feedback, temperature feedback, or a fixed time mode; the current feedback refers to monitoring changes in the electrolytic current and triggering switching when the current fluctuation exceeds a threshold; the temperature feedback refers to detecting the electrolyte temperature through a temperature sensor and adjusting the switching time according to the temperature rise rate; the fixed time mode refers to preset an optimized time interval based on experimental data, such as 10-30s.

[0027] In one specific embodiment of the present invention, the voltage is adjustable in the range of 30V-150V, and different electrode pairs before and after switching can use the same or different voltages.

[0028] In this embodiment, the steps of a three-electrode method for electrolytic preheating and electrolytic ignition of hydroxylamine nitrate liquid propellant are as follows: S1, Initialization: Inject hydroxylamine nitrate propellant, set the electrode pair switching sequence and initial voltage.

[0029] S2, Start electrolysis: The first set of electrode pairs is energized. After the switching time is reached, the current electrode pair is automatically turned off and the next set of electrode pairs is activated to continue electrolysis.

[0030] S3, Termination: Power is supplied until the electrolyte temperature reaches its peak value, ignition is complete, and the power is cut off.

[0031] Verification experiments were conducted to compare the effects of traditional dual-electrode electrolytic ignition and the three-electrode electrolytic ignition proposed in this invention. The experiments used two platinum metal sheets as positive electrodes, designated as platinum electrode A and platinum electrode B, and one stainless steel metal sheet as the negative electrode, also a stainless steel electrode. The three electrodes were evenly distributed at 120° circumferential angles. Figure 1 As shown, its parameters are as follows: As shown in the table, the effective area ratio of platinum electrode A and stainless steel electrode is different from that of platinum electrode A and stainless steel electrode; the former is smaller than the latter.

[0032] In the following experiments, the propellant used was 6g of 70% hydroxylamine nitrate solution, and the electrolysis voltage was 60V.

[0033] Traditional two-electrode mode experiment: Slow-mode experiment: Only platinum electrode A and stainless steel electrode were connected to form a circuit to electrolyze the electrolyte. The obtained current and temperature data are as follows: Figure 3 As shown by the solid black line, the current response is gradual during electrolysis, the temperature rise rate is low, and the time required for the reaction to reach the maximum temperature is relatively long.

[0034] Multi-electrode switching mode experiment: A dynamic switching experiment was conducted with a three-electrode configuration. The procedure was as follows: First, platinum electrode A and the stainless steel electrode were connected to form a circuit for electrolysis of the electrolyte. After a specific time t1 (10 s in the example), platinum electrode A was disconnected, and the circuit was switched to platinum electrode B, which then formed a circuit with the stainless steel electrode to continue electrolysis. After a specific time t2 (20 s in the example), platinum electrode B was disconnected again, and the circuit was switched back to platinum electrode A, which then formed a circuit with the stainless steel electrode to continue electrolysis. This alternating operation was repeated until electrolysis was completed. Data were recorded for five sets of different switching time parameters, such as... Figure 3 The solid lines in purple, red, blue, green, and orange are used to indicate this.

[0035] For ease of description, the ignition time in the traditional two-electrode electrolysis ignition experiment is defined as the time from the start of energization to the time when the solution reaches its maximum temperature, while the ignition time in the three-electrode electrolysis ignition experiment is defined as the time from the start of electrode switching to the time when the solution reaches its maximum temperature.

[0036] analyze Figure 3 Data shows that the multi-electrode switching mode does not affect the final maximum temperature, but it can affect the current electrolysis mode, significantly shortening the reaction time. Furthermore, with optimization of the switching time parameters, the ignition time gradually decreases. After switching, the system immediately inherits the electrolysis characteristics of the current electrode pair, proving that the reaction rate can be controlled in real time through dynamic electrode switching. The asymmetric electrode structure combined with the time-sharing switching strategy reduces overall power consumption while minimizing electrode polarization losses, providing a technical basis for repeated ignition.

[0037] Therefore, the electrolytic ignition method for hydroxylamine nitrate-based liquid propellant based on multiple electrodes provided by this invention can significantly shorten the time for the electrolytic reaction to reach the maximum temperature, improve the system response speed, achieve low-voltage ignition more quickly, and reduce the overall required electrolytic power.

[0038] The above description is merely a glimpse into the specific content and operation of this invention, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A three-electrode method for electrolytic preheating-electrolytic ignition of hydroxylamine nitrate-based liquid propellant, characterized in that, Includes the following steps: Three electrolytic electrodes are set in the electrolysis chamber, including two positive electrodes and one negative electrode, which constitute two sets of electrolytic electrode pairs; After the hydroxylamine nitrate liquid propellant is injected into the electrolysis chamber, a set of electrolysis electrodes is energized to start electrolysis preheating; After the preset switching time is reached, the currently working electrolytic electrode pair is turned off, and the electrolysis is switched to another set of non-working electrolytic electrodes to continue electrolysis until electrolysis is completed and the propellant is ignited.

2. The three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method according to claim 1, characterized in that, The effective area ratio of the positive to negative electrode of the electrolytic electrode is 0.5-2.

0.

3. The three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method according to claim 1, characterized in that, During the electrolysis process, the working voltage is adjustable within the range of 30V-150V.

4. The three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method according to claim 1, characterized in that, The electrolyte solution is a hydroxylamine nitrate-based liquid propellant, comprising an aqueous solution of hydroxylamine nitrate and a mixed liquid propellant composed of hydroxylamine nitrate and fuel.

5. The three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method according to claim 1, characterized in that, Each pair of electrolytic electrodes is driven by an independent control circuit, enabling time-sharing energization and electrical isolation switching.

6. The three-electrode hydroxylamine nitrate liquid propellant electrolytic preheating-electrolytic ignition method according to claim 1, characterized in that, The preset switching time is dynamically adjusted based on real-time feedback of electrolysis current or temperature.

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