CN113027546B - A low-pressure cylinder zero-output cooling effect evaluation method suitable for wet-cooled 300MW units - Google Patents

Abstract

A method for evaluating the cooling effect of a low-pressure cylinder with zero output suitable for a wet-cooled 300MW unit of the present invention includes: 1) for the wet-cooled 300MW unit, through the test method, respectively obtain: cooling steam flow rate, cooling steam temperature, unit back pressure, low-pressure cylinder The correction curve of the desuperheating water flow to the temperature of the secondary and final stages of the low-pressure cylinder. 2) Combined with each correction curve, respectively obtain: the correction value of cooling steam flow, cooling steam temperature, unit back pressure, and low-pressure cylinder desuperheating water flow to the temperature of the second and final stages of the low-pressure cylinder. 3) Combining the correction values, obtain: comprehensive correction value. 4) According to the comprehensive correction value in step 3), obtain: the corrected low-pressure cylinder sub-final stage and final stage temperature. During the actual zero-output operation, when the temperature, pressure, flow rate of the cooling steam and the back pressure of the unit deviate from the design values, it is possible to directly qualitatively and quantitatively evaluate the cooling effect of the cooling steam on the sub-final and final-stage blades. design value.

Description

A low-pressure cylinder zero-output cooling effect evaluation method suitable for wet-cooled 300MW units

technical field

The invention belongs to the technical field of steam turbine operation, and in particular relates to a low-pressure cylinder zero-output cooling effect evaluation method suitable for a wet-cooled 300MW unit.

Background technique

In recent years, the low-pressure cylinder zero-output technology has greatly improved the unit’s heating capacity and electrical peak-shaving capacity, enabling flexible switching between the extraction and condensing steam extraction and the low-pressure cylinder zero-output operation mode of the heating unit. has been widely used. During the zero-output operation of the low-pressure cylinder, the steam entering the low-pressure cylinder from the medium and low-pressure connecting pipes is completely blocked, and only a small amount of steam enters the low-pressure cylinder through the cooling steam pipeline in the form of cooling steam, and maintains the secondary and final stage together with the desuperheating water of the low-pressure cylinder. , The final temperature is in the safe range.

However, in the actual operation process, the unit load and ambient temperature cannot always be at the design values, and the temperature, pressure, flow rate and unit back pressure of the cooling steam are also deviated from the design values. Therefore, it is necessary to propose a new method to correct the temperature of the secondary and final stages of the low-pressure cylinder, so as to evaluate whether the cooling effect of the cooling steam reaches the design value.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above problems, and to provide a low-pressure cylinder zero-output cooling effect evaluation method suitable for wet cooling 300MW units according to the method of the low-pressure cylinder zero-output operation adaptability test.

In order to achieve the above object, the present invention adopts the following technical methods, through

A low-pressure cylinder zero-output cooling effect evaluation method suitable for a wet-cooled 300MW unit, comprising the following steps:

1) For the wet-cooled 300MW unit, through the low-pressure cylinder zero-output operation adaptability test method, it is obtained respectively: correction curve;

2) Based on the correction curve of step 1), according to the actual operating parameters of the zero output of the low-pressure cylinder, respectively obtain: cooling steam flow, cooling steam temperature, unit back pressure, low-pressure Correction value of stage temperature;

3) Using the correction value of step 2), obtain: the comprehensive correction value of cooling steam flow rate, cooling steam temperature, unit back pressure, and low-pressure cylinder desuperheating water flow rate to the temperature of the secondary and final stages of the low-pressure cylinder: C{θ ₁ }, C{θ ₂ };

4) According to the comprehensive correction value of the temperature of the second and last stage of the low-pressure cylinder in step 3), obtain: the corrected temperature of the second and last stage of the low-pressure cylinder: θ′ ₁ , θ′ ₂ ;

5) Using the temperature of the secondary and final stages of the low-pressure cylinder corrected in step 4), obtain: the evaluation parameters of the cooling effect of the cooling steam on the secondary and final blades: the deviation rate of the cooling effect of the secondary and final blades Δ ₁ , the end The deviation rate Δ ₂ of the cooling effect of the first stage blade is used to quantitatively evaluate the cooling effect of the cooling steam on the second and last stage blades when the low-pressure cylinder of the wet-cooled 300MW unit is running at zero output.

A further improvement of the present invention is that the correction value of the cooling steam flow rate to the temperature of the secondary and final stages of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention lies in that the correction value of the temperature of the cooling steam to the temperature of the secondary and final stages of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the correction value of the unit back pressure to the temperature of the secondary and final stages of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the correction value of the desuperheating water flow of the low-pressure cylinder to the temperature of the secondary and final stages of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the correction value of the cooling steam flow rate to the temperature of the last stage of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the correction value of the cooling steam temperature to the temperature of the last stage of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the correction value of the unit back pressure to the temperature of the secondary and final stages of the low-pressure cylinder is calculated from the actual operating value and the design value.

A further improvement of the present invention is that the corrected secondary and final temperature of the low-pressure cylinder is determined by the comprehensive correction value of the cooling steam flow rate, the cooling steam temperature, the unit back pressure, the low-pressure cylinder desuperheating water flow to the secondary and final temperature of the low-pressure cylinder, and the low-pressure cylinder secondary and final temperature. The design value of the stage temperature is calculated;

The corrected final temperature of low pressure cylinder is calculated from the comprehensive correction value of cooling steam flow, cooling steam temperature, unit back pressure, low pressure cylinder desuperheating water flow to low pressure cylinder final temperature and the design value of low pressure cylinder final temperature.

A further improvement of the present invention is that the deviation rate of the cooling effect of the cooling steam on the secondary and final stage blades is calculated from the corrected temperature of the secondary and final stages of the low-pressure cylinder and the design value of the temperature of the secondary and final stages of the low-pressure cylinder;

The deviation rate of the cooling effect of the cooling steam on the last stage blades is calculated from the corrected temperature of the last stage of the low pressure cylinder and the design value of the temperature of the last stage of the low pressure cylinder.

The present invention at least has the following beneficial technical effects:

During the actual zero-output operation, when there is a deviation between the temperature and flow of the cooling steam, the back pressure of the unit, and the flow rate of the desuperheating water in the low-pressure cylinder and the design value, if the actual value of the temperature of the second and last stage and the final stage are directly compared with the design value , the cooling effect of the cooling steam on the second and last stage blades cannot be reasonably evaluated.

That is to say, high cooling steam flow, low cooling steam temperature, low back pressure, and high and low pressure cylinder desuperheating water flow are all beneficial to the reduction of the temperature of the second and final stages, so it is necessary to modify the curve according to the above parameters (through the zero output operation of the low pressure cylinder). Adaptability test) to correct the temperature of the secondary and final stages, eliminate the influence of various influencing factors on the temperatures of the secondary and final stages, and then compare them with the design values, so as to reasonably, scientifically and quantitatively evaluate the effect of cooling steam on the cooling steam. Whether the cooling effect of the secondary and final stage blades reaches the design value.

Description of drawings

FIG. 1 is a logical block diagram of the method steps of the present invention.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

Example

As shown in Figure 1, for the wet-cooled 300MW unit, through the method of adaptability test of low-pressure cylinder zero-output operation, it is obtained:

(1) Correction curve of cooling steam flow to the temperature of the secondary and final stages of the low-pressure cylinder

θ ₁ =f ₁ (Q ₁ )

θ ₂ =f ₂ (Q ₁ )

(2) The correction curve of the cooling steam temperature to the temperature of the secondary and final stages of the low-pressure cylinder

θ ₁ =f ₃ (T ₁ )

θ ₂ =f ₄ (T ₁ )

(3) The correction curve of back pressure to the temperature of the secondary and final stages of the low-pressure cylinder

θ ₁ =f ₅ (P ₂ )

θ ₂ =f ₆ (P ₂ )

(4) The correction curve of the desuperheating water flow of the low-pressure cylinder to the temperature of the secondary and final stages of the low-pressure cylinder

θ ₁ =f ₇ (Q ₂ )

θ ₂ =f ₈ (Q ₂ )

Step 2:

Based on the above correction curve, according to the actual operating parameters of the zero output of the low pressure cylinder, we can get:

(1) The correction value of the cooling steam flow to the temperature of the secondary and final stages of the low-pressure cylinder

C{θ ₁ |Q ₁ }=f ₁ (Q ₁₀ )-f ₁ (Q ₁ )

C{θ ₂ |Q ₁ }=f ₂ (Q ₁₀ )-f ₂ (Q ₁ )

(2) The correction value of the cooling steam temperature to the temperature of the secondary and final stages of the low-pressure cylinder

C{θ ₁ |T ₁ }=f ₃ (T ₁ )-f ₃ (T ₁₀ )

C{θ ₂ |T ₁ }=f ₄ (T ₁ )-f ₄ (T ₁₀ )

(3) Correction value of back pressure to the temperature of the secondary and final stages of the low-pressure cylinder

C{θ ₁ |P ₂ }=f ₅ (P ₂ )-f ₅ (P ₂₀ )

C{θ ₂ |P ₂ }=f ₆ (P ₂ )-f ₆ (P ₂₀ )

(4) The correction value of the desuperheating water flow of the low-pressure cylinder to the temperature of the secondary and final stages of the low-pressure cylinder

C{θ ₁ |Q ₂ }=f ₇ (Q ₂₀ )-f ₈ (Q ₂ )

C{θ ₂ |Q ₂ }=f ₈ (Q ₂₀ )−f ₈ (Q ₂ )

Step 3:

Obtained according to step 2: During the actual operation of the low-pressure cylinder with zero output, the comprehensive correction values of the cooling steam flow, cooling steam temperature, unit back pressure, and low-pressure cylinder desuperheating water flow to the temperature of the secondary and final stages of the low-pressure cylinder are:

C{θ ₁ }=C{θ ₁ |Q ₁ }+C{θ ₁ |T ₁ }+C{θ ₁ |P ₂ }+C{θ ₁ |Q ₂ }

C{θ ₂ }=C{θ ₂ |Q ₁ }+C{θ ₂ |T ₁ }+C{θ ₂ |P ₂ }+C{θ ₂ |Q ₂ }

Step 4:

The corrected temperatures of the secondary and final stages of the low-pressure cylinder can be obtained as follows:

θ′ ₁ =θ ₁ +C{θ ₁ }

θ′ ₂ =θ ₂ +C{θ ₂ }

Step 5:

Then obtain: the evaluation parameters of the cooling effect of the cooling steam on the second and last stage blades: the deviation rate of the cooling effect of the second and last stage blades (Δ ₁ ), the deviation rate of the cooling effect of the last stage blades (Δ ₂ ):

When Δ ₁ is a positive number, the effect of cooling steam on the secondary and final blades is lower than the design value, and the larger the absolute value, the worse the cooling effect; when Δ is 0, the cooling effect of cooling steam on the secondary and final blades is consistent with the design value. ; When Δ is a negative number, the cooling effect of the cooling steam on the second and last stage blades is better than the design value, and the larger the absolute value, the better the cooling effect.

When Δ ₂ is a positive number, the cooling effect of the cooling steam on the last stage blades is lower than the design value, and the larger the absolute value, the worse the cooling effect; when Δ is 0, the cooling effect of the cooling steam on the last stage blades is consistent with the design value; When Δ is a negative number, the cooling effect of the cooling steam on the last stage blades is better than the design value, and the larger the absolute value, the better the cooling effect.

Claims (1)

1. The low-pressure cylinder zero-output cooling effect evaluation method suitable for the wet-cooling 300MW unit is characterized by comprising the following steps of:

1) aiming at a wet-cooling 300MW unit, respectively obtaining the following results by a low-pressure cylinder zero-output operation adaptability test method: correction curves of cooling steam flow, cooling steam temperature, unit backpressure and low-pressure cylinder desuperheating water flow to the temperature of the penultimate stage and the final stage of the low-pressure cylinder are obtained;

2) based on the correction curve in the step 1), obtaining the following parameters according to the actual operation parameters of the low pressure cylinder with zero output force: the corrected values of the cooling steam flow, the cooling steam temperature, the unit back pressure and the low-pressure cylinder desuperheating water flow on the temperature of the penultimate stage and the final stage of the low-pressure cylinder;

the correction value of the cooling steam flow to the temperature of the penultimate stage of the low-pressure cylinder is obtained by calculating an actual operation value and a design value; the correction value of the cooling steam temperature to the penultimate temperature of the low-pressure cylinder is obtained by calculation from an actual operation value and a design value; the correction value of the backpressure of the unit to the temperature of the penultimate stage of the low-pressure cylinder is obtained by calculating an actual operation value and a design value; the correction value of the low-pressure cylinder desuperheating water flow to the low-pressure cylinder penultimate temperature is obtained by calculating an actual operation value and a design value; the correction value of the cooling steam flow to the final-stage temperature of the low-pressure cylinder is obtained by calculating an actual operation value and a design value; the correction value of the cooling steam temperature to the final-stage temperature of the low-pressure cylinder is obtained by calculation from an actual operation value and a design value; the correction value of the backpressure of the unit to the final-stage temperature of the low-pressure cylinder is obtained by calculating an actual operation value and a design value;

3) obtaining the following correction value in the step 2): the comprehensive correction values of the cooling steam flow, the cooling steam temperature, the unit back pressure and the low-pressure cylinder desuperheating water flow on the temperature of the penultimate stage and the final stage of the low-pressure cylinder are as follows: c { theta [ theta ]) ₁ }、C{θ ₂ }；

4) Obtaining a comprehensive correction value of the temperature of the penultimate stage and the final stage of the low-pressure cylinder in the step 3): the corrected temperatures of the penultimate stage and the final stage of the low-pressure cylinder are as follows: lambda' ₁ 、θ′ ₂ ；

The corrected temperature of the penultimate stage of the low-pressure cylinder is obtained by calculating the comprehensive corrected value of the cooling steam flow, the cooling steam temperature, the unit back pressure, the low-pressure cylinder desuperheating water flow to the temperature of the penultimate stage of the low-pressure cylinder and the design value of the temperature of the penultimate stage of the low-pressure cylinder;

the corrected final-stage temperature of the low-pressure cylinder is obtained by calculating a comprehensive correction value of the cooling steam flow, the cooling steam temperature, the unit back pressure, the low-pressure cylinder desuperheating water flow to the final-stage temperature of the low-pressure cylinder and a design value of the final-stage temperature of the low-pressure cylinder;

5) obtaining the temperatures of the penultimate stage and the final stage of the low-pressure cylinder after the correction in the step 4): evaluation parameters of cooling effect of cooling steam on the penultimate and final stage blades: sub-last stage blade cooling effect deviation ratio delta ₁ And the deviation ratio Delta of the cooling effect of the last-stage blade ₂ The method is used for quantitatively evaluating the cooling effect of the cooling steam on the penultimate and final-stage blades when the low-pressure cylinder of the wet-cooling 300MW unit runs with zero output;

calculating the deviation rate of the cooling effect of the cooling steam on the penultimate blade according to the corrected penultimate temperature of the low-pressure cylinder and the final penultimate temperature design value of the low-pressure cylinder;

and calculating the deviation rate of the cooling effect of the cooling steam on the last-stage blade from the corrected low-pressure cylinder last-stage temperature and the low-pressure cylinder last-stage temperature design value.

Images