JP3314428B2 - Fan stall prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan stall prevention device suitable for use in, for example, an aircraft turbofan engine.

[0002]

2. Description of the Related Art Conventionally, a turbofan engine has been used as a jet engine for an aircraft. FIG.
FIG. 1 is a sectional view showing a schematic structure of a turbo fan engine of this type. In the figure, inflow air a taken in from outside is first compressed by a fan b. A part of the compressed air sent from the fan b passes through the fan air discharge duct c and is jetted directly to the outside of the engine as a bypass thrust. On the other hand, the compressed air is also taken into the casing from the fan outlet d, is further compressed to a high pressure by the compressor e, is sent into the combustion chamber f, and is mixed with the supplied fuel and burned. Exhaust gas discharged from the combustion chamber f rotates the compressor turbine g and the fan turbine h, and is ejected from the exhaust duct i as a core thrust.

Further, the fan b and the fan turbine h are formed on a common low-pressure system rotor j, and the compressor e and the compressor turbine g are formed on a common high-pressure system rotor k. Is controlled by adjusting the supplied fuel by a fuel flow control device (not shown). Normally, in a turbofan engine, the relationship between the pressure at the fan outlet d and the air flow rate needs to be maintained in an appropriate state, so that the relationship between the rotational speeds of the low-pressure rotor j and the high-pressure rotor k is within a certain allowable range. It is controlled to fit within.

[0004]

However, when the aircraft suddenly decelerates and enters a transient state from a steady state, the high-pressure rotor k has a smaller moment of inertia than the low-pressure rotor j, and therefore has a higher inertia than the low-pressure rotor j. The rotation speed decreases rapidly.
For this reason, at the time of sudden deceleration, the relationship between the two rotational speeds, which has been maintained in the steady state, deviates from the allowable range. In such a case, the air flow rate decreases, the pressure at the fan outlet d increases, and an aerodynamic instability phenomenon called surging occurs. When this surging occurs, a vibration is generated at the fan outlet d (hereinafter, this state is referred to as a fan stall), which makes the movement of the fan b unstable and causes the fan b to be damaged.

[0005] The present invention has been made under such a background, and an object of the present invention is to provide a fan stall prevention device capable of preventing a fan stall occurring in a casing of a turbofan engine.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel flow control for controlling a rotation speed of a low-pressure system rotor of a turbofan engine and a rotation speed of a high-pressure system rotor of the engine. In a fan stall prevention device connected to a device and controlling the rotation speed of the high-pressure system rotor during rapid deceleration of the engine, a rotation speed change rate of the low-pressure system rotor is measured, and a first speed corresponding to the change rate is measured. A first detection unit that outputs a detection signal, and an appropriate value of a rotation speed change rate of the high-pressure system rotor during rapid deceleration of the engine is stored as a function of the rotation speed change rate of the low-pressure system rotor. Target value calculating means for outputting an appropriate value of the rate of change of the rotational speed of the high-pressure system rotor corresponding to the first detection signal as a target value signal; and measuring the rate of change of the rotational speed of the high-pressure system rotor. A second detection unit that outputs a second detection signal corresponding to the rate of change, a subtraction unit that subtracts the second detection signal from the target value signal, and outputs a result of the subtraction as an error signal; Based on the error signal, a compensating means for outputting a first fuel flow rate command value for compensating the rotation speed of the high-pressure system rotor and a fuel flow rate for determining the rotation speed of the high-pressure system rotor are calculated according to a predetermined logic, A fuel flow rate calculating means for outputting the result as a second fuel flow rate command value; comparing the first fuel flow rate command value with the second fuel flow rate command value; High value selecting means for supplying to the apparatus.

[0007]

According to the present invention, the first detecting means measures the rate of change of the rotational speed of the low-pressure system rotor and outputs a first detection signal corresponding to the rate of change, and the target value calculating means sets First
An appropriate value of the rate of change of the rotation speed of the high-pressure system rotor at the time of rapid deceleration corresponding to the detection signal is output as a target value signal. The second detecting means measures the rate of change of the rotational speed of the high-pressure system rotor and outputs a second detection signal corresponding to the rate of change, and the subtracting means calculates the second detection signal from the target value signal. The detection signal is subtracted, and the result of the subtraction is output as an error signal. Then, the compensating means outputs a first fuel flow command value for compensating the rotation speed of the high-pressure system rotor based on the error signal. On the other hand, the fuel flow rate calculating means calculates a fuel flow rate for determining the rotation speed of the high-pressure system rotor according to a predetermined logic, and outputs the result as a second fuel flow rate command value. Then, the high value selecting means compares the first fuel flow rate command value and the second fuel flow rate command value and supplies a larger value to the fuel flow rate control device. Thereby, at the time of rapid deceleration, the rotation speed of the high-pressure system rotor decreases as the rotation speed of the low-pressure system rotor decreases, and it is possible to prevent the rotation speed of the high-pressure system rotor from suddenly decreasing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a fan stall prevention device according to one embodiment of the present invention.
The fan stall prevention device is connected to a fuel flow control device (not shown) of the turbofan engine illustrated in FIG. 3 and controls the rotation speed of the high-pressure system rotor k. In FIG. 1, reference numeral 1 denotes a controller that controls each part of the fan stall prevention device. The operation of the controller 1 will be described later.

Reference numeral 2 denotes a target value calculation unit. The target value calculation unit 2 calculates a measured value dNf of the rotation speed change rate of the low pressure system rotor j output from the low pressure system rotor rotation speed change rate detection unit 6.
/ Dt (where t is time, Nf is the rotational speed of the low-pressure rotor j, and d / dt is the derivative with respect to time), and the target value (dNg / d) of the rotational speed change rate of the high-pressure rotor k
t) ref (where Ng represents the rotation speed of the high-pressure system rotor k and ref represents a target value).
That is, the target value calculation unit 2 calculates the rotation speed change rate of the high-pressure system rotor k that is adapted to the rotation speed change rate of the low-pressure system rotor j by a predetermined function so that there is no danger of fan stall occurring when the aircraft suddenly decelerates. It is calculated by the formula, and this is output as the target value (dNg / dt) ref.

Reference numeral 3 denotes a subtraction unit. The subtraction unit 3 converts the target value (dNg / dt) ref of the rotation speed change rate of the high-pressure system rotor k supplied from the target value calculation unit 2 into a high-pressure output from the high-pressure system rotor rotation speed change rate detection unit 7. The measured value dNg / dt of the rotation speed change rate of the system rotor k is subtracted, and the subtraction result is output as an error Δe.

Reference numeral 4 denotes a well-known fuel control logic unit. The fuel control logic unit 4 calculates a fuel flow to be supplied to the turbofan engine that determines the rotation speed of the high-pressure system rotor k according to a predetermined fuel control logic that is determined in advance, and sets this as a fuel flow command value c1. Output.

Reference numeral 5 denotes a high value selection unit. This high price selection part 5
Compares the fuel flow rate command value c1 output from the fuel control logic unit 4 with the fuel flow rate command value c2 output from the controller 1 based on the error Δe, and selects the larger value. It outputs to the fuel flow control device as the flow command value c0.

Next, the operation of the fan stall prevention device having the above configuration will be described. FIG. 2 is a flowchart showing a control program executed by the controller 1 during operation of the turbofan engine. When this control program is executed, the process of the controller 1 first proceeds to step ST1. In step ST1, the low-pressure system rotor rotation speed change rate detection unit 6 measures the rotation speed change rate of the low-pressure system rotor j, and supplies the measured value dNf / dt to the target value calculation unit 2.

When the process proceeds to step ST2, the target value calculation unit 2 determines the change in the rotation speed of the high-pressure system rotor k corresponding to the measured value dNf / dt of the rotation speed change rate of the low-pressure system rotor j obtained in step ST1. Rate target value (dNg / d
t) Ref is calculated and supplied to the subtraction unit 3.

Next, at step ST3, the high-speed rotor speed change rate detecting unit 7 measures the high-speed system rotor k change rate, and subtracts the measured value dNg / dt from the subtraction unit 3.
Supply to Then, when the process proceeds to step ST4, the subtracting unit 3 sets the target value (dNg / dNg /
dt) The measured value dNg / dt obtained in step ST3 is subtracted from ref, and the subtraction result is supplied to the controller 1 as an error Δe.

Next, in step ST5, the controller 1 calculates a fuel flow rate that minimizes the error Δe obtained in step ST4, and supplies this to the high value selection unit 5 as a fuel flow rate command value c2. Then, step ST6
In step ST4, the high value selection unit 5 compares the fuel flow command value c1 supplied from the fuel control logic unit 4 with the fuel flow command value c2 supplied from the controller 1 in step ST4, and selects the larger value. I do.

In step ST7, the fuel flow command value c0 selected in step ST6 is supplied to the fuel flow control device of the turbo fan engine. Thus, the fuel flow control device supplies a fuel flow according to the fuel flow command value c0 to the turbofan engine. Thereafter, while the controller 1 executes the control program, the above-described operations of steps ST1 to ST7 are repeated.

Thus, when the aircraft suddenly decelerates,
Since the rotation speed of the high-pressure system rotor k decreases in accordance with the decrease in the rotation speed of the low-pressure system rotor j, and the rotation speed of the high-pressure system rotor k is prevented from sharply decreasing, the same as in the steady state, the fan outlet d is closed. The balance between the pressure and the air flow rate is not lost, and fan stall does not occur.

[0019]

As described above, according to the present invention, during rapid deceleration, the rotation speed of the high-pressure rotor decreases as the rotation speed of the low-pressure rotor decreases, and the rotation speed of the high-pressure rotor decreases. Since a sudden drop can be prevented, the effect that the balance between the pressure at the fan outlet and the air flow rate is not largely broken and the fan stall does not occur is obtained as in the steady state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a control program executed by a controller 1 in the embodiment.

FIG. 3 is a sectional view showing a schematic structure of a turbofan engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Controller (compensation means) 2 Target value calculation part (target value calculation means) 3 Subtraction part (subtraction means) 4 Fuel flow logic part (fuel flow calculation means) 5 High value selection part (high value selection means) 6 Low pressure system rotor speed Change rate detecting section (first detecting means) 7 High-pressure system rotor rotational speed changing rate detecting section (second detecting means) a Inflow air b Fan c Fan air discharge duct d Fan outlet e Compressor f Combustion chamber g Compressor Turbine h Fan turbine i Exhaust duct j Low pressure rotor k High pressure rotor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-145326 (JP, A) JP-A-61-241424 (JP, A) JP-A-49-120010 (JP, A) JP-A-59-1200 99039 (JP, A) JP-A-57-60246 (JP, A) JP-A-1-310131 (JP, A) JP-A-3-3927 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) F02C 1/00-9/58 F02K 1/00-11/00 F23R 3/00-7/00

Claims (1)

(57) [Claims] 1. A low-pressure system rotor for a turbofan engine, which is connected to a fuel flow control device for controlling a rotational speed of a high-pressure system rotor of the engine and a high-speed system rotor of the turbofan engine when the engine is rapidly decelerated. A fan stall prevention device for controlling a rotation speed, wherein a first detection means (6) for measuring a rotation speed change rate of the low-pressure system rotor and outputting a first detection signal corresponding to the change rate; The rapid change in the rotational speed of the high-pressure rotor is stored as a function of the rotational speed of the low-pressure rotor, and the rotational speed of the high-pressure rotor corresponding to the first detection signal is stored. A target value calculating means (2) for outputting an appropriate value of the rate of change as a target value signal; and measuring a rate of change of the rotational speed of the high-pressure rotor and outputting a second detection signal corresponding to the rate of change. A second detection unit (7); a subtraction unit (3) that subtracts the second detection signal from the target value signal and outputs a result of the subtraction as an error signal; Compensation means (1) for outputting a first fuel flow rate command value for compensating the rotation speed of the rotor and a fuel flow rate for determining the rotation speed of the high-pressure rotor are calculated according to a predetermined logic, and the result is calculated as a second value. Comparing the first fuel flow command value and the second fuel flow command value, and outputting the larger one to the fuel flow control device. A fan stall prevention device comprising a high value selecting means (5) for supplying.