CN108561232B

CN108561232B - Ignition fuel flow control method for sub-circle oil supply of auxiliary power device

Info

Publication number: CN108561232B
Application number: CN201711293773.3A
Authority: CN
Inventors: 杨帆; 冯健朋; 周宇辰; 吕伟
Original assignee: Xian Aeronautics Computing Technique Research Institute of AVIC
Current assignee: Xian Aeronautics Computing Technique Research Institute of AVIC
Priority date: 2017-12-07
Filing date: 2017-12-07
Publication date: 2020-06-09
Anticipated expiration: 2037-12-07
Also published as: CN108561232A

Abstract

The invention belongs to the technical field of digital control of aero-engines, and particularly relates to an ignition fuel flow control method for sub-circle oil supply of an auxiliary power device. The duty ratio control mode of switching on and off fast is adopted to adjust the fuel flow of an Auxiliary Power Unit (APU) in the starting ignition stage, and the problems that the fuel flow is overlarge, the fuel pressure is too low and the fuel atomization is insufficient due to the fact that the area of a fuel flow passage is suddenly increased when a main oil passage of a fuel distributor is connected in the ignition stage of the APU are solved, so that a fire source formed in the starting oil passage before the main oil passage is connected is extinguished by the excessive low-pressure fuel, and the starting process is flameout are solved. The method can reduce the fuel flow, and solve the problems that the original constant flow of an APU starting oil path is overlarge and cannot ignite under the high altitude condition.

Description

Ignition fuel flow control method for sub-circle oil supply of auxiliary power device

Technical Field

The invention belongs to the technical field of digital control of aero-engines, and particularly relates to an ignition fuel flow control method for sub-circle oil supply of an auxiliary power device.

Background

The structure principle of the fuel control system of the general APU is shown in figure 1, and the fuel control system is composed of a fuel adjusting device, a starting valve SFV and a main valve MFV, wherein the SFV and the MFV respectively control the on-off of a starting oil path and a main oil path, and the flow area of a starting nozzle connected with the starting oil path is small, so that the fuel flow resistance of the starting oil path is large, the flow is small, the atomization effect is good, and an ignition fire source is easy to form; the main nozzle connected with the main oil way has a large flow area, and the adjustable range of the fuel flow is large so as to adapt to the fuel control in a large state.

The timing control of starting the APU is shown in FIG. 2, when the rotation speed of the APU reaches NG1, only the starting oil path is communicated to supply oil, and because the starting oil path has small circulation area, small flow, high oil pressure and good atomization effect, fuel oil and air are fully mixed and ignited by electric spark generated by an ignition accessory to form a stable fire source; because the oil supply amount of the starting oil path is limited, when the rotation speed of the APU reaches NG2, the main oil path is connected, the pressure of fuel oil conveyed to a combustion chamber is suddenly reduced due to the large circulation area of the main oil path, the atomization of the fuel oil is deteriorated, and low-pressure fuel oil sprayed from the main oil path can extinguish a fire source formed by the starting oil path, so that the starting failure is caused.

When a main oil way is connected, due to the fact that the fuel oil flow area is increased suddenly, fuel oil pressure is reduced suddenly and the fuel oil atomization effect is poor, the APU is prone to flameout, the traditional control method is to increase the starting fuel oil flow to offset the influence of oil pressure reduction, and the fuel oil flow formula is as follows:

in the formula, WF is the fuel flow, μ is the flow coefficient, a is the flow area, ρ is the fuel density, and Δ P is the oil pressure difference before and after the nozzle.

Because the oil supply pressure difference and the flow area form a square relation, the oil supply amount must be greatly increased to offset the reduction of the oil pressure, the over-temperature of the APU in the starting process is easily caused, on one hand, the use safety of the APU is endangered, and on the other hand, the service life of the APU is also unfavorable.

Disclosure of Invention

Objects of the invention

In order to solve the problems that in the starting process of the APU, when a main oil way is communicated, the fuel pressure is suddenly reduced and the fuel atomization is poor due to the sudden increase of the fuel flow area, so that a combustion chamber is flamed out, and the starting failure is caused, the ignition fuel flow control method for the auxiliary power device for supplying fuel in circles is provided.

Technical scheme of the invention

The invention discloses an ignition fuel flow control method for sub-circle oil supply of an auxiliary power device, which adopts the following technical scheme according to an APU starting control time sequence:

the method comprises the following steps that 1, the APU is in a static state, after a starting command is received, a starter motor is switched on to drive the APU to be switched on, and an ignition accessory is switched on to form an electric spark for ignition.

2. When the motor rotates with the APU to reach NG1 rotation speed, the starting valve is powered on to connect the starting oil path, the liquid fuel oil is formed into oil mist with good atomizing quality by the swirl nozzle on the starting oil path, the oil mist is ignited by the electric spark of the ignition accessory to form a torch, and the fuel oil flow of the starting oil path is controlled according to WF (WF is F (NG, P1)).

3. When the rotation speed of the APU reaches NG2, the starting valve is kept in a connection state, and the main valve is subjected to duty ratio mode fast on-off control to ensure that the fuel flow provided by the duty ratio control mode is matched with the starting fuel flow of the engine in unit time;

4. when the rotation speed reaches NGX, the main valve is switched to a long-pass fuel supply mode, fuel is supplied simultaneously by the main valve and the starting valve, and the fuel flow is controlled according to WF (WF-F (NG, P1)).

5. When the rotation speed of the APU reaches NG3, the starting motor is disconnected, the fuel is accelerated by the power generated by the gas of the APU, the main valve and the starting valve supply the fuel at the same time, and the fuel flow is controlled according to WF (WF is equal to F (NG, P1).

6. When the APU speed reaches NG4, the starting valve and the ignition accessories are disconnected, oil is supplied by the main valve, and the fuel flow is controlled according to WF (F) (NG, P1).

7. And when the rotation speed of the APU reaches NGSTD, ending the starting control process of the APU and switching to the control of the stable running state.

The invention has the advantages and effects

The core idea of the invention is to rapidly change the fuel oil circulation area A, and supply oil according to the normal starting oil demand, thereby avoiding the overtemperature caused by excessive oil supply in the traditional method; meanwhile, as the main valve is quickly switched on and off and the starting valve is in long-distance connection, in the switching-off process of the main valve, the starting oil path can form stable oil mist with good atomization effect through the swirl nozzle, and under the action of electric sparks of the ignition accessory, a stable ignition torch is provided to ignite the injected fuel oil when the main oil path is switched on, so that reliable ignition is ensured.

Drawings

FIG. 1 is a timing diagram for oil supply;

FIG. 2APU fuel control system;

FIG. 3APU start timing logic;

FIG. 4 APU start timing logic under duty cycle control;

fig. 5 duty cycle control.

Detailed Description

The ignition fuel supply control method of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

Example (b):

in the APU fuel control system, as shown in fig. 1, the fuel regulator outputs fuel according to a control schedule WF-F (NG, P1), and the main valve and the starting valve control the opening and closing of the main oil passage and the starting oil passage, respectively. Wherein NG is the APU speed, P1 is the APU inlet pressure, and WF is the fuel flow. In this case, the main oil passage has a large flow area, and the fuel pressure drops rapidly after the main valve is connected, so that the engine is easily extinguished.

The specific implementation steps and related parameters are as follows:

1, when the APU is in a forbidden state, after receiving a starting instruction, a starting motor and an ignition accessory are switched on, and the starting motor drives the APU;

when the rotation speed of the APU reaches 3%, recording the exhaust temperature at the moment as T40, switching on a starting valve, and supplying oil according to WF-F (NG, P1);

when the rotation speed of the APU reaches more than 18 percent and the difference between the current exhaust temperatures T4 and T40 is more than 50 ℃, the starting valve is opened, the on-off of the main valve is controlled according to a duty ratio mode, the duty ratio cycle is 100ms, the duty ratio is controlled according to the precision of 5 percent, the duty ratio control mode is shown in FIG. 4, X is the duty ratio of control output, X is one of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100, the fuel regulating device outputs fuel flow according to 55 percent, namely F (55 percent and P1), and the fuel flow output by the main oil passage and the starting oil passage is F (NG, P1) by gradually increasing the duty ratio X;

A. when the main valve is connected, fuel oil flows out of the main oil way, the flow is large, the pressure is low, the atomization is poor, a torch can be extinguished, and part of unburned fuel oil remains in the combustion chamber;

B. when the main valve is disconnected, only the valve is started to supply oil, fuel oil is well atomized, a torch is formed, and the whole combustion chamber is ignited again (at the moment, the fuel oil in the combustion chamber is more).

The oil supply mode makes the oil mist formed by the starting valve and the continuous oil supply formed by the main valve in the combustion chamber alternate in a short control period, and ensures the reliable ignition of small fuel flow. The starting fuel flow at this stage is controlled by WF ═ F (NG, P1).

When the rotation speed of the APU reaches more than 45 percent and the difference between the current exhaust temperature T4 and the current exhaust temperature T40 is more than 450 ℃, the main valve and the starting valve are in long-pass communication, and oil is supplied according to WF (WF-F (NG, P1);

when the rotation speed of the APU reaches 50%, the starting motor is turned off, the main valve and the starting valve are in long-distance communication, and oil is supplied according to WF (WF) to F (NG, P1);

when the rotation speed of the APU reaches 70%, the ignition accessories and the starting valve are closed, the main valve is in long pass, and oil is supplied according to WF (WF) to F (NG, P1);

7, when the rotation speed of the APU reaches 95%, the starting process is finished, the main valve is in long-pass state, and the fuel flow of the APU is controlled according to the steady-state operation process.

Claims

1. The ignition fuel flow control method for the sub-circle oil supply of the auxiliary power device is characterized by comprising the following steps of: the method comprises the following steps:

the method comprises the following steps that firstly, an APU is in a static state, after a starting instruction is received, a starting motor is switched on to drive the APU to be switched on, and an ignition accessory is switched on to form an electric spark for ignition;

step two, when the motor rotates with the APU to reach the NG1 rotating speed, the starting valve is electrified, the starting oil way is switched on, the liquid fuel oil is formed into oil mist with good atomizing quality by the swirl nozzle on the starting oil way, the oil mist is ignited by electric sparks of an ignition accessory to form a torch, the fuel oil flow of the starting oil way is controlled according to WF (WF is F (NG, P1), wherein P1 is the inlet pressure of the APU;

when the rotation speed of the APU reaches NG2, keeping the starting valve on, and carrying out rapid on-off control on the main valve in a duty ratio mode to ensure that the fuel flow provided by the duty ratio control mode is matched with the starting fuel flow of the engine in unit time;

step four, along with the increase of the rotation speed state of the APU, the pressure and the temperature of the combustion chamber are increased, the combustion condition of the fuel oil is gradually improved, the stability of the combustion is enhanced, when the rotation speed reaches NGX, the main valve is switched into a long-distance oil supply mode, the main valve and the starting valve supply oil simultaneously, and the flow rate of the fuel oil is controlled according to WF (WF is F (NG, P1);

step five, when the rotation speed of the APU reaches NG3, the starting motor is disconnected, the gas is accelerated by the power generated by the gas of the APU, the main valve and the starting valve supply oil simultaneously, and the fuel oil flow is controlled according to WF (F) (NG, P1);

step six, when the rotation speed of the APU reaches NG4, disconnecting the starting valve and the ignition accessories, supplying oil by a main valve, and controlling the fuel flow according to WF (F) (NG, P1);

step seven: and when the rotation speed of the APU reaches NGSTD, ending the starting control process of the APU and switching to the control of the stable running state.

2. The ignition fuel flow control method of an auxiliary power unit split-ring fueling as claimed in claim 1, wherein: the duty cycle control mode is a continuous duty cycle control mode.