阅读说明：本技术 一种航空发动机点火电路的升压电容的耐压值确定方法 (Method for determining withstand voltage value of boost capacitor of aircraft engine ignition circuit ) 是由 郝继红 谭俊 焦文娟 陈凤 梁杰 于 2020-12-18 设计创作，主要内容包括：本申请属于航空发动机起动点火技术领域,涉及一种航空发动机点火电路的升压电容的耐压值确定方法,包括步骤S1、获取所述第一放电回路中的初级绕组N1的电感量L、所述限流电阻R1的阻值R、以及所述电容器C2的电容值C；步骤S2、将所述第一放电回路等效为一个零输入RLC阻尼振荡回路,确定其微分方程,并确定放电管V击穿导通前电容器C2的电压U-(C0)；步骤S3、求解微分方程,确定电容器C上的电压Uc；步骤S4、根据降额系数,确定电容器C2的耐压值。按本申请提供的耐压值确定方法所确定的升压电容参数,相应的电路能够可靠工作,功能和性能满足要求,工作状态安全稳定。(The application belongs to the technical field of starting and igniting of aero-engines, and relates to a method for determining a withstand voltage value of a boost capacitor of an aero-engine ignition circuit, which comprises the steps of S1, obtaining an inductance L of a primary winding N1 in a first discharging loop, a resistance value R of a current limiting resistor R1 and a capacitance value C of a capacitor C2; step S2, the first discharging loop is equivalent to a zero input RLC damping oscillation loop, the differential equation is determined, and the voltage U of the capacitor C2 before the discharge tube V breaks down and is conducted is determined C0 (ii) a Step S3, solving a differential equation, and determining the voltage Uc on the capacitor C; and step S4, determining the withstand voltage value of the capacitor C2 according to the derating coefficient. According to the boost capacitor parameter determined by the withstand voltage value determining method provided by the application, the corresponding circuit can reliably work, the function and the performance meet the requirements, and the working state is safe and stable.)

1. A method for determining the withstand voltage value of a boost capacitor of an aeroengine ignition circuit comprises a first discharge circuit and a second discharge circuit, the first discharge circuit comprises a capacitor C2, a discharge tube V, a primary winding N1 of a transformer T and a current limiting resistor R1, the second discharge circuit comprises a capacitor C1, a discharge tube V, a secondary winding N2 of a transformer T and an ignition nozzle DZ, wherein, the DC power supply provided by the ignition power supply firstly charges the energy storage capacitor C1, and simultaneously charges the energy storage capacitor C2 by taking the capacitor C1 as the power supply through the current limiting resistors R1 and R2, when the voltage across the capacitors C1, C2 reaches the breakover voltage Unp of the discharge tube V, the discharge tube V breaks down and conducts, the ignition nozzle DZ forms the breakdown voltage, the method is characterized in that the capacitor C2 is used as a boosting capacitor, and the withstand voltage value determining step comprises the following steps:

step S1, obtaining the inductance L of the primary winding N1, the resistance R of the current limiting resistor R1 and the capacitance C of the capacitor C2 in the first discharging loop;

step S2, the first discharging loop is equivalent to a zero input RLC damping oscillation loop, the differential equation is determined, and the voltage U of the capacitor C2 before the discharge tube V breaks down and is conducted is determined_C0；

Step S3, solving a differential equation, and determining the voltage Uc on the capacitor C;

and step S4, determining the withstand voltage value of the capacitor C2 according to the derating coefficient.

2. The method for determining the withstand voltage value of the boost capacitor of the aircraft engine ignition circuit according to claim 1, wherein:

in step S2, the differential equation is:

3. the method for determining the withstand voltage value of the boost capacitor of the aircraft engine ignition circuit according to claim 2, wherein:

the differential equation is solved as:

wherein the content of the first and second substances,α＝R/(2L)；U_C0is the voltage at which the discharge tube V breaks down the pre-capacitor C2.

4. The method for determining the withstand voltage value of the boost capacitor of the aircraft engine ignition circuit according to claim 1, wherein:

in step S4, the derating coefficient is determined according to the lowest derating level of the aviation mica fixed capacitor.

5. The method for determining the withstand voltage value of the boost capacitor of the aircraft engine ignition circuit according to claim 1, wherein:

in step S4, the derating factor is 0.7, and the withstand voltage value of the capacitor C2 is determined as follows:

U_ce＝u_c/0.7＝1.43u_c(V)。

Technical Field

The application belongs to the technical field of starting and igniting of aero-engines, and particularly relates to a method for determining a withstand voltage value of a boost capacitor of an aero-engine ignition circuit.

Background

The starting ignition system of the aircraft engine consists of an ignition device, an ignition cable and an ignition electric nozzle, and is shown in figure 1. The working principle of the starting ignition system of the aircraft engine is as follows: the ignition device converts low-voltage electric energy provided by an engine power supply into high-voltage pulse electric energy, transmits the high-voltage pulse electric energy to the ignition electric nozzle through the ignition cable, instantly releases the high-voltage pulse electric energy at the discharge end of the ignition electric nozzle to generate high-power discharge sparks which are used for igniting fuel oil and air mixed gas in a combustion chamber of the engine so as to start the engine.

The high-voltage discharge circuit with secondary boosting shown in fig. 2 is one of the current circuit forms of the ignition device of the starting ignition system of the domestic aircraft engine, and the circuit structure adopts secondary boosting according to the ignition circuit of a certain foreign aircraft engine to drive a high-voltage surface electric nozzle to generate spark discharge.

The working principle of the circuit is as follows: dc power supplied from an ignition power source is charged into the energy storage capacitor C1 through the diode VD, and at the same time, the capacitor C1 is used as a power source to charge the energy storage capacitor C2 through the current limiting resistors R1 and R2. The capacitor C1 is used for storing the energy required by the operation of the ignition nozzle DZ, the capacitor C2 is used for storing the energy required by the boosting of the secondary booster transformer T, and the discharge tube V functions as a discharge switch. As the charging process proceeds, the discharge tube V breaks down into conduction when the voltage across the capacitors C1, C2 reaches the conduction voltage upnp of the discharge tube V1.

At this time, in the discharge circuit i composed of the capacitor C2, the discharge tube V, the primary winding N1 of the transformer T, and the current limiting resistor R1, the capacitor C2 discharges the primary winding N1 of the transformer T through the discharge tube V and the current limiting resistor R1, and the high voltage Un2 required for the ignition nozzle is induced in the secondary winding N2 of the transformer T due to electromagnetic induction.

In the main discharge circuit ii consisting of the capacitor C1, the discharge tube V, the secondary winding N2 of the transformer T and the ignition nozzle DZ, the voltage of the capacitor C1 and the voltage induced by the secondary winding N2 of the transformer T are superimposed to provide a high voltage to the ignition nozzle DZ, which high voltage causes the ignition nozzle to discharge by breakdown, releasing the electric energy stored in the energy storage capacitor C1 at the discharge end of the ignition nozzle to form a discharge spark.

The breakdown voltage of the ignition torch DZ is usually higher than the conduction voltage of the discharge tube, the breakdown voltage at the later stage of the service life reaches 2-3 times of the initial value, and the breakdown voltage is multiplied under the high-pressure condition, so that the voltage is usually increased to 10-25 kV.

From the above working principle, the design of the secondary booster circuit is an important link for determining whether the whole ignition circuit can realize the expected function and reliably work in the life cycle. The existing ignition device products using the circuit are developed by referring to the parameters of foreign circuits to determine the parameters by a test method, namely the parameters of the part of the device are tested, and the special parts in the foreign models are usually only numbered and have no parameters. As shown in fig. 2, the rated working voltage (hereinafter referred to as withstand voltage) of the capacitor C2 is not labeled, and is selected by tests or comparison methods instead of theoretical calculation, and is often selected to be higher, usually 8kV, and the requirement of aviation products on weight and volume is continuously increased, which is not favorable for accurate design of products.

At present, a method for calculating the withstand voltage of the capacitor of the secondary booster circuit is not available.

Disclosure of Invention

In order to solve the above problem, the present application provides a method for determining a withstand voltage value of a boost capacitor of an aircraft engine ignition circuit, the aircraft engine ignition circuit comprising a first discharge circuit and a second discharge circuit, the first discharge circuit comprising a capacitor C2, a discharge tube V, a primary winding N1 of a transformer T, and a current limiting resistor R1, the second discharge circuit comprising a capacitor C1, a discharge tube V, a secondary winding N2 of a transformer T, and an ignition tip DZ, wherein a dc power supply provided by the ignition power supply first charges an energy storage capacitor C1, and at the same time charges an energy storage capacitor C2 with a capacitor C1 as a power supply via current limiting resistors R1, R2, and when a voltage across the capacitors C1, C2 reaches a conduction voltage upnp of the discharge tube V, the discharge tube V breaks down and conducts, the ignition tip DZ forms a breakdown voltage, the capacitor C2 acts as a boost capacitor, the step of determining the withstand voltage value comprises the following steps:

step S1, obtaining the inductance L of the primary winding N1, the resistance R of the current limiting resistor R1 and the capacitance C of the capacitor C2 in the first discharging loop;

step S2, the first discharging loop is equivalent to a zero input RLC damping oscillation loop, the differential equation is determined, and the voltage U of the capacitor C2 before the discharge tube V breaks down and is conducted is determined_C0；

Step S3, solving a differential equation, and determining the voltage Uc on the capacitor C;

and step S4, determining the withstand voltage value of the capacitor C2 according to the derating coefficient.

Preferably, in step S2, the differential equation is:

preferably, the differential equation is solved as:

wherein the content of the first and second substances,α＝R/(2L)；U_C0is the voltage at which the discharge tube V breaks down the pre-capacitor C2.

Preferably, in step S4, the derating coefficient is determined according to the lowest derating level of the aviation mica fixed capacitor.

Preferably, in step S4, the derating factor is 0.7, and the withstand voltage value of the capacitor C2 is determined as follows according to the derating factor:

U_ce＝u_c/0.7＝1.43u_c (V)。

according to the boost capacitor parameter determined by the withstand voltage value determining method provided by the application, the corresponding circuit can reliably work, the function and the performance meet the requirements, and the working state is safe and stable.

Drawings

Fig. 1 is a block diagram of an ignition system.

Fig. 2 is a working principle diagram of a secondary boosting high-voltage discharge circuit.

Fig. 3 is a flowchart of a method for determining a withstand voltage value of a boost capacitor of an aircraft engine ignition circuit according to the present application.

Fig. 4 is a schematic diagram of the connection of the discharge circuit i of the present application.

For the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; further, the drawings are for illustrative purposes, and terms describing positional relationships are limited to illustrative illustrations only and are not to be construed as limiting the patent.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all embodiments of the present application. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application, and should not be construed as limiting the present application.

Further, it is noted that, unless expressly stated or limited otherwise, the terms "mounted," "connected," and the like are used in the description of the invention in a generic sense, e.g., connected as either a fixed connection or a removable connection or integrally connected; can be mechanically or electrically connected; they may be directly connected or indirectly connected through an intermediate medium, or they may be connected through the inside of two elements, and those skilled in the art can understand their specific meaning in this application according to the specific situation.

Referring to fig. 2, the aeroengine ignition circuit comprises a first discharge loop and a second discharge loop, wherein the first discharge loop comprises a capacitor C2, a discharge tube V, a primary winding N1 of a transformer T and a current-limiting resistor R1, the second discharge loop comprises a capacitor C1, a discharge tube V, a secondary winding N2 of the transformer T and an ignition nozzle DZ, wherein a direct-current power supply provided by the ignition power supply firstly charges an energy storage capacitor C1, and meanwhile, the capacitor C1 is used as a power supply to charge an energy storage capacitor C2 through the current-limiting resistors R1 and R2, and when the voltage at two ends of the capacitors C1 and C2 reaches the conducting voltage Unp of the discharge tube V, the discharge tube V is broken down and conducted, and the ignition nozzle DZ forms a breakdown voltage.

The method for determining the withstand voltage value of the boosting capacitor of the aircraft engine ignition circuit aims to determine the withstand voltage value of the capacitor in the secondary boosting circuit. As shown in fig. 3, the method mainly includes:

step S1, obtaining the inductance L of the primary winding N1, the resistance R of the current limiting resistor R1 and the capacitance C of the capacitor C2 in the first discharging loop;

step S2, the first discharging loop is equivalent to a zero input RLC damping oscillation loop, the differential equation is determined, and the voltage U of the capacitor C2 before the discharge tube V breaks down and is conducted is determined_C0；

Step S3, solving a differential equation, and determining the voltage Uc on the capacitor C;

and step S4, determining the withstand voltage value of the capacitor C2 according to the derating coefficient.

In order to achieve the object of the invention, the circuit parameter relationship of the discharge loop I must be cleared. As can be seen from the circuit principle of fig. 2, after the discharge tube V is broken down and turned on, the discharge loop i is first put into a conducting operating state, and only the discharge loop i is discussed here to determine the withstand voltage of the capacitor C2.

For ease of calculation, a schematic diagram of the conditioning discharge circuit I is shown in FIG. 4. The discharge loop is composed of a capacitor C, a current-limiting resistor R, a discharge tube V and a primary winding N1 of a transformer T, the inductance of the primary winding N1 is L, and the conduction voltage drop of the discharge tube V is small relative to the voltage on the capacitor C and can be ignored, so that the discharge loop is a zero-input RLC damping oscillation loop.

The voltage Uc across the capacitor C2 can be determined from the differential equation of the zero-input RLC damped tank:

the current-limiting resistor R1 in the loop has small value, so that the current-limiting resistor R1 can meet the requirementThus:

wherein the content of the first and second substances,α＝R/(2L)；U_C0is the voltage at which the discharge tube V breaks down the pre-capacitor C2.

According to the lowest derating grade III of the mica fixed capacitor of the aviation product, the derating coefficient is given to be 0.7, so that the withstand voltage Uce of the capacitor C is selected according to the following formula:

U_ce＝u_c/0.7＝1.43u_c (V)

in order to verify the effect of the invention, an ignition circuit with a secondary boosting high-voltage discharge circuit is designed by utilizing the method of the invention, wherein U_C0And (5) selecting 2500V to obtain a Uce of 3575V, and selecting a 4kV capacitor according to standard specifications, wherein the volume of the capacitor is smaller than that of an 8kV capacitor. The circuit diagram is shown in fig. 2, and a principle prototype is made according to the diagram for function verification. The principle prototype is matched with an ignition cable and an ignition electric nozzle to form ignitionThe system has normal power-on test function, the maximum working voltage peak value of the actually measured capacitor C2 is 2800V, the working state is safe and stable, and the verification result proves that the invention achieves the purpose.

Having thus described the present application in connection with the preferred embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the scope of the present application is not limited to those specific embodiments, and that equivalent modifications or substitutions of related technical features may be made by those skilled in the art without departing from the principle of the present application, and those modifications or substitutions will fall within the scope of the present application.