CN107490319B

CN107490319B - Method for determining annual variable angle optimized operation scheme of half-regulation fan of cooling tower

Info

Publication number: CN107490319B
Application number: CN201710546587.XA
Authority: CN
Inventors: 仇宝云; 陆霞; 罗翌; 冯晓莉; 有力
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2017-07-06
Filing date: 2017-07-06
Publication date: 2020-01-07
Anticipated expiration: 2037-07-06
Also published as: CN107490319A

Abstract

A method for determining a year-round variable-angle optimized operation scheme of a half-regulation fan of a cooling tower belongs to the field of industrial system energy conservation, and calculates total ventilation resistance and total impedance of the cooling tower; calculating and determining actual working parameters of different blade mounting angles of a fan in the cooling tower; taking a week as a time unit, calculating the minimum required ventilation volume of each week of the cooling tower all the year around, and determining a blade installation angle corresponding to a fan and the input power of a matched motor; calculating and determining a variable angle optimized operation scheme of different blade installation angle numbers adopted by a cooling tower fan all the year by taking the lowest energy cost as a target; comparing the total cost of the fan operation and angle modulation of the variable angle optimization operation scheme adopting different blade installation angle numbers all the year around, and determining the optimal variable angle optimization operation scheme by taking the lowest total cost as a target, wherein the optimal variable angle optimization operation scheme comprises the blade installation angle numbers, the installation angle values of all the blades and the operation time period of the fan operation all the year around; the result shows that the cooling tower half-adjusting fan variable-angle optimized operation scheme determined by the invention has obvious energy-saving effect.

Description

Method for determining annual variable angle optimized operation scheme of half-regulation fan of cooling tower

Technical Field

The invention belongs to the field of industrial system energy conservation, and relates to an annual variable-angle operation optimization scheme of a half-regulation fan of a cooling tower.

Background

With the continuous development of the economy of China, the demand of energy is more and more large, the shortage of energy seriously affects the development of the economy of China, and energy conservation and consumption reduction are a long-term basic national policy for developing the economy of China.

Nowadays, circulating cooling water systems are spread in the industrial departments of metallurgy, electric power, steel, petrochemical industry and the like, and cooling towers are used as important equipment in the circulating cooling water systems and are used for cooling circulating water passing through cooled equipment. The cooling tower is designed and selected according to the ventilation quantity required by the worst environment working condition all the year around, and the fan operates under the working condition of the designed maximum ventilation quantity for a long time. In fact, the ventilation volume of the fan required by the cooling tower to meet the requirement of cold quantity heat exchange in winter and spring and autumn is far lower than the designed maximum ventilation volume, and the over-cooling ventilation operation mode of the fan of the cooling tower with a fixed installation angle all the year round causes serious energy waste.

Disclosure of Invention

The invention aims to overcome the defect that the annual maximum required ventilation quantity of a cooling tower half-adjusting fan is designed to determine blade installation angle operation to generate excessive cooling and cause serious energy waste, and provides a method for determining an annual angle-changing optimization operation scheme of the cooling tower half-adjusting fan. In order to achieve the above purpose, the invention provides an accurate determination method of a cooling tower fan variable-angle optimized operation scheme, which comprises the following steps:

A. calculating total ventilation resistance P of cooling tower_ZAnd the total impedance S.

Taking a counter-flow cooling tower as an example, the resistance coefficients of all parts in the tower are solved as follows:

a) air inlet resistance coefficient: xi₁＝0.55

b) Resistance coefficient of air guide device:

ξ₂＝(0.1+0.025q)·L (2)

wherein Q is the total water flow, m³H; f is the area of the water spraying filler zone, m²(ii) a q is the density of the water spray, m³/(m²H); l is the length of the air guide device, m.

c) The turning resistance coefficient of the air flow before entering the water spraying device is as follows: xi₃＝0.5

d) Resistance coefficient of the support beam of the water spraying device:

ξ₄＝0.5·(1-F₄/F)+(1-F₄/F)² (3)

in the formula, F₄The net ventilation area m for the air flow at the supporting beam of the water spraying device to pass through²。

e) Resistance coefficient of water distribution device:

ξ₅＝[0.5+1.3·(1-F₅/F)²](F/F₅)² (4)

in the formula, F₅For the net draught area, m, of the cooling tower at the level of the water distributor trough²。

f) Resistance coefficient of water collector:

ξ₆＝[0.5+2·(1-F₆/F)²](F/F₆)² (5)

in the formula, F₆The net ventilation area m for the airflow passing through the supporting beam of the water collector²。

g) The calculation of the resistance coefficient of the inlet of the wind tube ring beam is divided into the following types according to the form of the air inlet:

1. conical tapered flare: the schematic view is referred to as 'technical design code of mechanical draft cooling tower' diagram B.0.9-1.

Looking up the mechanical draft cooling tower process design specification table B.0.9-1 according to the H/D value of the ratio of the height of the contraction section to the diameter of the small opening of the contraction section and the contraction angle alpha to obtain xi₇。

2. Circular arc convergent horn mouth: the schematic view is referred to as 'technical design code of mechanical draft cooling tower' diagram B.0.9-2.

Looking up the mechanical draft cooling tower process design Specification table B.0.9-3 according to the value of the ratio r/D of the radius of the tapered arc to the diameter of the small opening of the tapered section to obtain xi₇。

A "hemispherical dome" reducer: the schematic diagram is referred to as 'technical design code of mechanical draft cooling tower' diagram B.0.9-3.

According to the taper angle alpha and the area ratio F/F of two ends₇Looking up the technical design Specification of mechanical draft Cooling Tower in Table B.0.9-4 gets xi₇. Wherein, F₇Is the area of the inlet of the air duct, m²

F₇＝0.785·D² (6)

h) Resistance coefficient of a reducing section at the inlet of the air duct:

wherein

In the formula, lambda is the frictional resistance coefficient of the on-way loss, and is generally 0.03; n ═ F_Into/F_Larynx，F_IntoIs the area of the inlet of the air duct, F_LarynxThe area of the throat part of the air duct; k is a reducing buffer coefficient, and a chart B.0.10 of technical design specifications of a mechanical draft cooling tower is looked up;

i) resistance coefficient of the diffusion section at the outlet of the air duct:

the schematic view of the diffusion at the outlet of the air duct is referred to as a 'mechanical draft cooling tower process design specification' diagram B.0.11-1.

δ＝-0.05·(H'/D₀)+0.5 (11)

ξ₉＝(ξ_{Expanding device}+ξ_{Go out})·(1+δ) (12)

ξ_{Go out}＝1×(F_Larynx/F_{Go out})² (14)

Wherein α' is a divergent angle, °; d₀Is the diameter of the throat part of the air duct, m; k' is a gradual expansion buffer coefficient, and is obtained by searching in a table B.0.11 of technical design specifications of mechanical draft cooling towers; n ═ F_{Go out}/F_Larynx，F_{Go out}Is the area of the outlet of the air duct, m²(ii) a Delta is caused by a built-in fan of an air ductAnd (4) correction coefficients of uneven wind speed distribution.

j) Resistance of water spraying filler:

in the formula, P_tlThe resistance of the water spraying filler is Pa; v is the average air velocity of the section of the filler, m/s; A. m is the resistance coefficient of different fillers, and is obtained by table 3 in the analysis of thermal and resistance properties of plastic water-spraying fillers of cooling towers; a. the₁、A₂、A₃、m₁、m₂、m₃The coefficient, which is related to the type and height of the plastic water-pouring filler, can be found from the related data.

In the formula, P_zM gas column for total resistance of cooling tower; s is the total impedance, h²/(10⁸·m⁵) (ii) a G is the ventilation of the cooling tower, ten thousand meters³H; i is the serial number of each component in the tower body of the cooling tower; n is the total number of all components in the cooling tower; xi_i、v_i、F_iRespectively the local resistance coefficient, the air speed of the section m/s and the area of the section m of each component of the cooling tower²。

B. Calculating and determining that the fan is in the cooling towerActual working point parameters during different blade mounting angles during working: flow rate G_jWind pressure P_jPower N_jAnd efficiency η_fj。

The performance curve of the cooling tower fan is provided by equipment manufacturers, and the available equation of the fan wind pressure performance curve is fit as follows:

in the formula, j is the number of the fan blade installation angle; m is the number of the fan blade mounting angles; p_jThe wind pressure and the m air column when the jth blade of the fan is installed at an angle are set; g_jThe air quantity is ten thousand meters when the jth blade of the fan is arranged at an angle³/h；A_j、B_j、C_j、D_jIs a constant. Equation (21) has m equations in total.

The cooling tower fan power performance curve can be fit with the equation as:

in the formula, N_jThe power is kW when the jth blade of the fan is installed at an angle; a. the_j’、B_j’、C_j’、D_j' is a constant, and there are m equations.

According to the structure of the cooling tower and the type of the filler, the pressure performance curve equation for determining the requirement of the cooling tower can be expressed as follows:

P＝SG² (23)

solving the jth blade mounting angle of the fan and the jth equation (23) of the simultaneous equation (21) to obtain the running air volume G of the fan at the jth blade mounting angle of the fan in the cooling tower_jAnd wind pressure P_j(j ═ 1, 2, 3, …, m), amounting to 2 m.

The obtained wind quantity G of the m blade installation angles of the fan in the cooling tower_jRespectively substituting into the power performance curve equation of the corresponding blade installation angle of the fan, and calculating to obtain m power N_jCalculating the mounting angles of m blades of the fan according to the formula (24)Efficiency eta_fj

M efficiencies η calculated by the equation (24)_fjAnd (3) fitting a fan air volume-efficiency curve and an air volume-blade installation angle curve:

η_fj＝η_fj(G) (24’)

β_j＝β_j(G) (24”)

in the formula eta_fjMounting angle beta for jth blade of fan_jI.e. air quantity G_jEfficiency of the time.

C. And calculating and determining the minimum ventilation quantity required by the cooling tower under different environmental conditions.

Under the condition that the heat quantity and the cooling water flow quantity of the cooled equipment need to be removed are fixed, the lower the environmental temperature is, the smaller the humidity is, the smaller the minimum ventilation quantity needed by the cooling tower of the circulating cooling water system is, and the reduction of the ventilation quantity means that the fan of the cooling tower is operated to save energy. The minimum ventilation required for the cooling tower is determined in the following manner. Saturated water vapor pressure:

wherein, P' is saturated steam pressure, kPa; t is the air temperature, DEG C.

Air relative humidity when measured with an aspen thermometer:

in the formula (I), the compound is shown in the specification,

air relative humidity,%; theta is the air dry bulb temperature, DEG C; tau is the air wet bulb temperature, DEG C; p is atmospheric pressure, kPa; p_θ"is saturated air water vapor when the air temperature is equal to theta DEG CPartial pressure, kPa; p_τ"is the saturated air water vapour partial pressure, kPa, at an air temperature equal to τ ℃. Apparent density of wet air:

where ρ is the apparent density of the wet air in kg/m³；ρ_dIs the apparent density of the dry air part in the wet air, kg/m³；ρ_sIs the apparent density of the water vapor portion in the humid air, kg/m³. Moisture content of air:

wherein x is the air moisture content, kg/kg (DA). Specific enthalpy of humid air:

h＝1.005θ+x(2500.8+1.846θ) (29)

wherein h is the specific enthalpy of moist air, kJ/kg (DA). Specific saturated air enthalpy (saturated air enthalpy for short):

in the formula, h' is saturated air specific enthalpy, namely specific enthalpy of heat release when the air temperature is that the water vapor partial pressure reaches saturated state temperature t, kJ/kg (DA); p_t"is the saturated air water vapor partial pressure, kPa, at an air temperature equal to t ℃.

Thermodynamic calculation of the working characteristic cooling number of the counter-flow cooling tower, and the packing characteristic number:

Ω_n'＝Bλ^k (31)

in the formula, omega_n' is the characteristic number (dimensionless) of the working filler of the counter-flow cooling tower; B. and k is an experimental constant of the water spraying filler, and is obtained by table 2 in cooling tower plastic water spraying filler thermal and resistance performance analysis.

By adopting an enthalpy difference method, the cooling number of the cooling tower is as follows:

in the formula, omega_nThe cooling number (dimensionless) for the operating characteristics of the counter-flow cooling tower; k is the coefficient of heat removal of the evaporated water volume (K)<1.0, dimensionless); c_wTaking 4.1868kJ/(kg DEG C), which is the specific heat of water, and kJ/(kg DEG C); dt is the water temperature difference between the inlet water and the outlet water of the infinitesimal filler, and is DEG C; t is t₁The water temperature (DEG C) entering the tower; t is t₂The temperature of water leaving the tower (DEG C); r is_t2kJ/kg is the heat of vaporization of water at the water temperature of the filler.

The number of cooling cycles is preferably calculated by the multistage Simpson's base decomposition method, as follows:

Δt＝t₁-t₂ (37)

δt＝Δt/n＝(t₁-t₂)/n (38)

δh＝Δh/n＝(h₁-h₂)/n (39)

wherein n is the number of segments;

respectively corresponding to water temperature t₁-δt、t₁-2δt、t₁Saturated air enthalpy at (n-1) δ t, kJ/kg (DA); h'₁、h"₂Respectively is saturated air enthalpy when water temperature enters and exits the tower, kJ/kg (DA); h is₁、h₂Specific enthalpy, kJ/kg (DA), of the moist air entering and leaving the column, respectively; h is_mIs the average specific enthalpy of the humid air in the column, kJ/kg (DA). Delta t is the temperature difference of water entering and leaving the tower; δ t is the water temperature difference of equal segments, DEG C; delta h is the enthalpy difference of air entering and leaving the tower, kJ/kg (DA); δ h is the enthalpy difference of the iso-segments, kJ/kg (DA).

When the requirement on the calculation precision is not high and the delta t is less than 15 ℃, the following simplified calculation can be used:

in the formula, h "_mCorresponding to a water temperature of t_mSaturated air enthalpy, kJ/kg (DA).

As shown in FIG. 1, the cooling duty curve represents the number of cooling cycles that the cooling tower needs to have to meet the design conditions of the cooling tower given different gas-water ratios λ; the performance curve of the packing represents the cooling capacity of the cooling tower. When the same gas-water ratio is adopted, the cooling task of the cooling tower is equal to the cooling capacity, namely omega_n’＝Ω_nAnd is the working point of the cooling tower.

According to different environmental conditions, on the premise of meeting the cold quantity, the temperature of inlet and outlet water is controlled, and the corresponding air-water ratio lambda required by the working point of the cooling tower can be obtained through trial calculation. The patent adopts a continuous approximation method for trial calculation, as shown in fig. 2.

Setting a gas-water ratio lambda of the cooling tower₁Taking a plurality of different water temperatures t out of the tower₂A plurality of corresponding cooling numbers omega are calculated according to the above equations (25) to (40)_nFitting a quadratic curve as shown in FIG. 2; according to this lambda₁Calculating the cooling characteristic number (omega) of the trickle filler in the actual operation of the cooling tower_n’)₁Satisfy the cooling number (omega) of the cooling tower_n)₁Equal to the cooling characteristic number (omega) of the water spraying filler_n’)₁Under the premise of (a), the outlet water temperature (t) of the cooling tower corresponding to the equilibrium point is obtained from the curve₂)₁The temperature (t) of the inlet water is determined from the difference between the inlet water and the outlet water₁)₁And then (t) is₁)₁Is generally notThe required water temperature entering the tower is needed, and the problems now become: knowing the temperature t of the water entering the tower₁And the temperature difference between water entering and leaving the tower requires the corresponding gas-water ratio lambda, and the method is used for solving.

Referring to FIG. 3, for a given cooling tower fill system, with a gas-to-water ratio λ, a corresponding tower inlet water temperature t can be calculated using the above-mentioned series of equations₁，t₁Is a function of λ, and the function relationship is shown as curve ATB in FIG. 3, and point T on curve ATB is the coordinate (λ, T) to be solved₁λ) cannot directly pass t₁Solving by adopting an iterative computation point-by-point approximation method: knowing that the curve ATB decreases monotonically, two points A, B of lower gas-water ratio and higher gas-water ratio are taken on the curve ATB, and the values of the gas-water ratios are lambda respectively_A、λ_BSetting the required water temperature t_1A>t₁*>t_1BAir-water ratio lambda_A、λ_BRespectively calculating the water temperature t of the inlet tower_1A、t_1BTwo points a and B on the curve ATB are determined, and the equation AB of the straight line passing through A, B is determined as:

will t₁＝t₁Substituting formula (41), linear interpolation is carried out to obtain gas-water ratio lambda of corresponding C' point_C

By λ_CCalculating the actual tower inlet water temperature t of the balance point C on the curve ATB through the formulas (25) to (40)_1CComparing the calculated value t of the water temperature entering the tower_1CIf the requirement of given precision 0.01 is met, the equation of a straight line passing through two points AC is solved by the same method, and t is calculated₁＝t₁Substituting the linear equation of the AC two points, and linearly interpolating to obtain the gas-water ratio lambda of the corresponding D' point_DReuse λ_DCalculating and solving the actual tower inlet water temperature t of the balance point D on the curve ATB_1DCheck t_1DWhether the accuracy requirements, … …,until the nth iteration calculation, the point N on the curve infinitely approaches the point T and the formula (43) is satisfied

|t_1N-t₁*|≤0.01 (43)

The method can quickly iterate to approximate the solution t on the curve ATB₁The corresponding gas-water ratio lambda.

In the circulating water system of the fixed water volume operation, the corresponding minimum required ventilation volume under different environmental conditions can be obtained:

G_k＝λ_k·Q·ρ_w/(ρ_k·10000) (k＝1，2，3，…，z) (44)

in the formula, G_kIs the ventilation volume under the k environmental condition of ten thousand meters³/h；ρ_kIs the air density in kg/m under the k environmental condition³；ρ_wIs the density of the circulating water, kg/m³；λ_kThe mass ratio of air (calculated by dry air) entering the filler to water entering the filler under the k environmental working condition is kg (DA)/kg; z is the number of different environment working conditions.

D. And (4) calculating and determining the variable angle optimization operation scheme of the number of the mounting angles of different blades of the cooling tower half-adjusting fan all the year round.

Efficiency of the motor under any load:

in the formula eta_emTo the motor efficiency; eta_NRated efficiency for the motor; epsilon is the motor load factor; k is the ratio of the motor fixed loss factor to the variable loss factor. The size of k: the 2-pole asynchronous motor is 2; the number of the 4-pole and 6-pole asynchronous motors is 1; the number of 8 poles and above is 0.5. The b value is found according to table 1 of calculation of efficiency and power factor of asynchronous motor under any load.

The input power of a matched motor when the jth blade installation angle of a fan in the cooling tower runs is as follows:

in the formula, N_ejInputting power for the motor, kW; rho is air density, kg/m³(ii) a g is the acceleration of gravity, m/s²；η_cThe transmission efficiency of the fan and the matched motor is improved; eta_emjAnd calculating the input power of the matched motors at the setting angles of all the blades when the fan works in the cooling tower and fitting the input power into a curve, wherein the efficiency of the motor when the jth blade setting angle of the fan of the cooling tower runs.

The traditional method is that the fan model and the blade installation angle are selected according to the worst environment working condition of the cooling tower all the year-the maximum ventilation quantity required all the year round in summer, in the all year running process, the fan runs at the blade installation angle, but the ventilation quantity is too large in other three seasons all the year round, particularly in winter, the overcooling is generated, and the energy waste is caused. Therefore, in one year all the year, the fan blade installation angle should be changed in due time according to the minimum ventilation quantity required by the cooling tower under different environmental conditions under the condition of keeping the rotating speed of the fan unchanged, so that on the premise of meeting the cooling requirement of the cooling tower, the ventilation quantity is reduced, the fan energy consumption is reduced, and the angle-variable optimized operation of the fan of the cooling tower is realized.

Taking week as a time unit all the year round, substituting the maximum value of the minimum ventilation quantity required by the cooling tower at all moments in the week of the tth week into the fan operation air quantity of the week, substituting the maximum value into a pressure curve equation required by the ventilation of the cooling tower, solving the corresponding fan pressure, determining the required fan blade installation angle, and determining the input power of a motor matched with the fan at the tth week:

in the formula, N_tInputting power, kW, for the operation of the motor in the t week; rho_tVentilation air density of t week in kg/m³；G_tVentilation volume of t week³/h；P_tIs t weekThe operating wind pressure of (1) and (m) air columns; eta_ftThe operating efficiency of the fan in the t week; eta_emtMatching motor efficiency for the t week fan operation.

Annual operating energy consumption and cost of cooling tower fans:

in the formula, A_zThe power consumption for the annual operation of the cooling tower fan is kW.h; t is the number of times of year-round operation; t is the number of operating weeks in the whole year, and the continuous operation is counted by 52 weeks for one year; y is_zThe annual total energy cost is significant; and y is the unit price of the electric charge, yuan/(kW & h).

Because the blade of large-scale fan is half regulation formula usually, need shut down and carry out manual adjustment to the blade angle of erection, the cooling tower normal work receives the short time influence to need to spend certain expense. On the one hand, the fan blade installation angle is adjusted once, and the fan blade installation angle needs 0.5-1 h, and the water that originally gets into the cooling tower and carry out the cooling can directly be discharged into the cooling pond under the cooling tower in this period of time, and the cold volume of cold water in the make full use of cold water pond is recycled after mixing with the cold water in the cold water pond, and the short time can not cause adverse effect to being cooled off equipment. On the other hand, the adjustment of the blade mounting angle requires cost, so that the blade angle change of the fan is not suitable to be frequent all the year around, and the cost of the blade mounting angle adjustment should be considered when determining the optimal operation scheme of the fan angle change.

And determining the installation angle of the fan blade according to the minimum ventilation quantity required by the cooling tower at different time intervals (in cycles) all the year around, calculating to obtain the corresponding input power of the motor, and performing curve fitting on the annual data.

In one year, the installation angle of the fan blade is changed, and the input power N of the matched motor in a corresponding time period_tAnd (6) changing. Under the condition that the number of the installation angles of the blades of the fan is fixed all the year round, the time points of angle change are different, the power consumption of the fan in all the year round operation is different, and the fan is to be usedThe time point of the annual fan angle change is used as a variable, a calculation formula of the annual fan operation power consumption is listed, and the fan operation power consumption A of the annual fan blade installation angle number is found out through a method of seeking a derivative to obtain an extreme value or an iterative calculation method_zAnd obtaining the optimal variable angle optimal operation scheme of the fan with the annual blade mounting angle number according to the minimum value and the optimal blade mounting angle and variable angle time point of the fan with the variable angle for several times corresponding to the minimum value. And changing the annual fan blade installation angle number to obtain the annual fan variable angle optimized operation scheme with various different blade installation angle numbers.

Calculating the change rule of the minimum matching input power of the motor required by the fan blade angle corresponding to the minimum required ventilation quantity of the cooling tower per week along with the time (week) under the working condition of practical environment all year round, and setting the change rule as an equation

N_r＝N_r(t) (51)

In the formula, N_rThe required fan is matched with a motor to input power, kW; t is time variable, weekly.

Scheme I blade installation angle optimization operation all year around

Referring to FIG. 4, the time-varying curve of the minimum input power of the motor required for ventilation of the cooling tower fan in the year, tth in summer₁The week is the worst environment working condition time all the year around, and the minimum ventilation quantity of the fan required at the moment is the maximum all the year around. The scheme is as follows₁The ventilation volume and the wind pressure of the week are selected from the fan types and the blade installation angles meeting the ventilation volume, and the corresponding annual operation power of the fan is N₁Can satisfy N₁≥N_rTotal energy consumption is N ═ N₁The rectangular area enclosed by the horizontal and the abscissa axis, i.e.

A_z＝168×N₁T (52)

Scheme two-year and all-year two-blade installation angle optimized operation

As shown in FIG. 5, the scheme is firstly performed in the tth summer₁The type of the fan and the installation angle of the blade meeting the ventilation volume are selected according to the circumferential ventilation volume and the wind pressure, and the input power of the matched motor is N₁But if, howeverWhen the cooling tower operates according to the working condition in all other three seasons, the ventilation volume of the cooling tower is much larger than the minimum required ventilation volume, an overcooling state is generated, and energy waste is caused, as shown in fig. 5, the fan operates by adopting two blade installation angles all the year around 1 to t_{2 small}Week and t_{2 is large}The blade angle of the fan is reduced from the week to the Tth week, and the fan is matched with a motor to input power N₂Operate to satisfy N₂≥N_r，N₂Power N of minimum blade installation angle of blower_min(ii) a At the t th_{2 small}Week to t_{2 is large}The installing angle of the fan blade is increased, and the fan is matched with a motor to input power N₁Operate to satisfy N₂<N_r≤N₁If the total annual energy consumption of the fan unit is the area between the three horizontal lines and the abscissa axis, the value is multiplied by the unit price of the electric charge, that is, the total annual fan operation cost is obtained, that is, the total annual fan operation cost is

Y_z＝A_z·y＝168×{[T-(t_{2 is large}_-t_{2 small})]·N₂+(t_{2 is large}_-t_{2 small})·N₁}·y (53)

Let formula (51) N (t) N₂Can be solved to obtain t_{2 small}And t_{2 is large}Are respectively expressed as

By substituting formula (54) for formula (53)

The meaning of formula (55) is: the annual energy cost Y of the fan adopting the operation scheme_zThe input power of a motor matched with the fan corresponding to the changed working condition of the installation angle of the fan blade is a single variable N₂As a function of (c).

Calculating the derivative extremum or programming sequence of equation (55) to determine the power N₂And further determining the corresponding fan blade mounting angle, and substituting formula (54) to solve the time point t for changing the blade mounting angle_{2 small}、t_{2 is large}To makeThe annual energy cost of the fan is the minimum.

Optimized operation of three blade mounting angles in three years and all the year

As shown in FIG. 6, in the scheme, the minimum input power of the matched motor required by the variable-angle operation of the fan in different seasons of the cooling tower all the year is greatly changed, and three blade mounting angles are adopted for operation, which correspond to the input power N of the matched motor of the fan respectively₁、N₂And N₃Is provided with N₁>N₂>N₃And N is₃≥N_minThe input power of the motor matched with the fan is a function of time, namely N (t). In week 1 to t_{3 small}Week and t_{3 is large}The minimum input power N of a motor matched with a fan required by ventilation of a cooling tower under actual environment working conditions from week to Tth week_r≤N₃All motors are supplied with input power N₃Running if the fan is matched with the input power N of the motor₃<N_minThen take N₃＝N_min(ii) a At the t th_{3 small}Week to t_{2 small}Week and t_{2 is large}Week to t_{3 is large}Week, N₃<N_r≤N₂All motors are supplied with input power N₂Running; at the t th_{2 small}Week to t_{2 is large}Week, N₂<N_r≤N₁All motors are supplied with input power N₁And (5) operating. The total annual energy consumption is the area enclosed by the broken line and the axis of abscissa, and the total annual fan operation cost is obtained by multiplying the unit price of the electric charge, namely

In the formula (56), the maximum value N of the input power of the motor matched with the minimum fan required all the year around₁And the corresponding blade installation angle and the corresponding time are known quantities as in the second scheme. Input power N of motor matched with other two fans₂、N₃And the corresponding installation angle and variable angle time point of the fan blade are unknown, in order to further reduce the operation energy consumption, a method such as a solution scheme II is needed, the lowest annual energy cost of the fan unit is taken as a target, and derivation is adopted to solve an extreme valueOr performing optimization solution by using an iterative calculation method.

Scheme four-blade mounting angle optimized operation in four whole years

As shown in FIG. 7, it is assumed that the fan operates at four blade mounting angles throughout the year, except for N, which is the most unfavorable operating condition throughout the year₁In addition, three operation powers N are set₂、N₃、N₄And the corresponding fan blade installation angle, listing the annual energy cost expression of the fourth scheme according to the methods of the second scheme and the third scheme, optimally solving by adopting a method of deriving and obtaining an extreme value or trial calculation by taking the annual energy cost minimum of the fan unit as a target, and determining N₂、N₃、N₄The three fans are matched with the motors to input power and corresponding fan blade installation angles and variable angle time points, so that the operation energy consumption can be further reduced. The optimal operation scheme of the fan which operates according to five or six … … blade installation angles all the year can be obtained by the same method. If the time-of-use electricity price is implemented, the electricity fee is calculated according to time periods.

Five-half scheme adjustment fan annual blade installation angle once-per-week angle change optimized operation

As shown in figure 8, the scheme adopts the annual weekly angle-changing optimized operation, so that the air quantity of the fan per week is exactly equal to the minimum ventilation quantity required by the cooling tower in the week, if the period from 1 st week to t th week_{m is small}Week and t_{m is large}The minimum input power of a fan matched motor required by the cooling tower from the week to the Tth week is smaller than the input power N of a fan matched motor with the minimum blade installation angle of the fan of the model_minAll with power N_minAnd (5) operating. The total energy consumption is the area enclosed by the minimum power line and the abscissa axis in the graph 8, and the total annual fan operation cost is obtained by multiplying the total energy consumption by the unit price of the electric charge, namely

The fan of the scheme adjusts the angle for 1 time per week, and the angle adjusting cost is high all the year around.

Scheme six-full adjustment fan annual blade installation angle once-per-week angle-changing optimized operation

The energy cost calculation of the fan is the same as that of the fifth scheme, and the fan adopts a blade mounting angle full-adjusting device, so that the equipment cost is increased.

E. And comparing the cost of the numerical variable angle optimization operation scheme of the mounting angles of different blades of the cooling tower half-adjusting fan all the year round with the optimal variable angle optimization operation scheme.

The total annual cost of the fans of the cooling tower not only considers the energy cost, but also needs to add the cost of fan angle modulation.

In the scheme, the blades are installed at an angle for optimal operation all the year around, as shown in fig. 4, the fan operates all the year around without changing the angle, so that the angle adjusting cost is not considered, and the total annual cost of the cooling tower fan is the fan energy cost.

Scheme two, two blade mounting angles are optimized all the year round, as shown in figure 5, N is used firstly in the all-year running of the fan₂Run when running to the t-th_{2 small}Time-of-week variation by a primary angle of N₁Run to tth_{2 is large}The installation angle of the blade is changed back to the original installation angle of the blade again in week, and the power is returned to N₂And the total annual cost of the fan of the cooling tower is equal to the sum of the energy cost of the fan and the 2-time angle modulation cost.

In the scheme, three blade mounting angles are optimized and operated all the year round, as shown in fig. 6, the fan needs to be subjected to angle adjustment for 4 times all the year round, so that the total annual cost of the fan of the cooling tower is equal to the sum of the energy cost of the fan and the 4-time angle adjustment cost.

Four blade mounting angles of the scheme all year around operate optimally, as shown in fig. 7, the fan needs to be subjected to angle modulation for 6 times all year around, so that the total annual cost of the cooling tower fan is equal to the sum of the energy cost of the fan and the 6-time angle modulation cost.

Five solutions are optimized to operate by changing the blade installation angle once a week all the year around, as shown in fig. 8, the fan needs to be adjusted 26 times all the year around, so the total annual cost of the cooling tower fan is equal to the sum of the fan energy cost and the 26 times angle adjustment cost.

Finally, comparing the annual originally designed blade mounting angle operation scheme of the fan, the annual one blade mounting angle optimized operation scheme I, the annual two blade mounting angle optimized operation scheme II, the annual three blade mounting angle optimized operation scheme III, the annual four blade mounting angle optimized operation scheme IV and the annual half-adjustment fan annual blade mounting angle once-per-week angle-changing optimized operation scheme V which is the total of 6 schemes of equipment energy and angle-adjusting cost, and finally determining the scheme with the least total cost as the optimal angle-changing optimized operation scheme.

The cost required for one-time angle adjustment of the fans with different sizes is also different. In the whole year, the more the angle modulation times of the variable-angle optimized operation of the fan are, the better the energy-saving effect is, but the increased energy-saving effect is reduced along with the increase of the number of the blade installation angles, and the angle modulation cost is linearly increased, so that the variable-angle optimized operation scheme with the optimal number of the blade installation angles exists, and the total cost of the energy and the angle modulation of the annual fan operation is the lowest.

Drawings

FIG. 1 is a graph of cooling duty curve and filler performance.

FIG. 2 is a graph showing the relationship between the cooling number of the cooling tower and the temperature of the water discharged from the tower.

FIG. 3 is a diagram of a cooling tower equilibrium point calculation iterative approximation method.

FIG. 4 is a graph of fan complete motor input power for a year round blade setting angle optimization run.

FIG. 5 is a graph of fan associated motor input power for a two blade setting angle optimization operating scheme throughout the year.

FIG. 6 is a graph of input power to a fan companion motor for a three blade setting angle optimization run scenario throughout the year.

FIG. 7 is a graph of fan associated motor input power for a four blade setting angle optimization operating scheme throughout the year.

FIG. 8 is a graph of fan associated motor input power for a once-a-week variable blade setting angle optimization operating scheme throughout the year.

Fig. 9 is a graph showing performance curves of the LF-42 type fan according to the present invention.

FIG. 10 is a graph showing the mounting angle of the variable angle blades of the cooling tower fan and the performance of the air volume according to the embodiment of the present invention.

FIG. 11 is a performance curve of wind pressure and wind volume in variable angle operation of a cooling tower fan according to an embodiment of the present invention.

FIG. 12 is a graph showing the performance of the cooling tower according to the present invention.

FIG. 13 is a graph showing the performance of the input power and the air volume of the motor for the variable angle operation of the cooling tower blower in accordance with the present invention.

Detailed Description

The following uses the technical solutions of the present invention to further describe the present invention with reference to the accompanying drawings and embodiments, but the present invention should not be construed as being limited thereto.

One workshop of a chemical plant has 1 LDCM-800SC type cooling tower, local atmospheric pressure 754mmHg, density 1.13kg/m³Cooling water flow rate of 800m^3/h. The fan model LF-42 is half-regulated, and is matched with a three-phase asynchronous motor Y180L-4, the rated power is 22kW, the rated current is 43A, the motor efficiency is 90%, and the rotating speed is 1470 r/min. The cooling tower was equipped with a model LJ3 reducer, which was 92% efficient. The unit price of the local electric charge is 0.6 yuan/(kW h).

The original operation scheme is as follows: the fan operates at 13-degree blade installation angle all the year round, and the operation air quantity is 45.3769 ten thousand meters³The operating power is 18.4877kW, the input power of the motor is 21.88kW, the annual operating power consumption is 191144 kW.h, and the energy cost is 114686 yuan.

The tower structure of the known LDCM-800SC cooling tower is as follows: packing area 46m²Air inlet area 46m²The length of the air guide device is 3 m; net ventilation area 41m for water drenching device²Water distribution device net ventilation area 43m²And the net ventilation area of the water collector is 43m²26m of air duct inlet area²Throat area of wind tube is 14.12m²Area of outlet of air duct 25.53m²The water spraying filler is in an inclined trapezoidal wave shape, the taper angle of the inlet of the air duct is 120 degrees, and the taper angle of the outlet of the air duct is 60 degrees.

Solving the resistance coefficients of all parts in the tower body of the cooling tower as follows:

a) air inlet resistance coefficient: xi₁＝0.55

b) The water spraying density q obtained by the formula (1) is 17 kg/(m)²H); substituting formula (2) to obtain the resistance coefficient of the air guide device:

ξ₂＝(0.1+0.025q)·L＝(0.1+0.025×17)×3＝1.575

d) Net ventilation area 41m by water drenching device²Area of packed region 46m²Substituting an input type (3) to obtain the resistance coefficient of the supporting beam of the water spraying device:

ξ₄＝0.5·(1-F₄/F)+(1-F₄/F)²＝0.5×(1-41/46)+(1-41/46)²＝0.066

e) clean ventilation area 43m by water distribution device²And (3) obtaining the resistance coefficient of the water distribution device by substituting formula (4):

ξ₅＝[0.5+1.3·(1-F₅/F)²](F/F₅)²＝[0.5+1.3×(1-43/46)²](46/43)²＝0.5785

f) the net ventilation area of the water collector is 43m²And (5) obtaining the resistance coefficient of the water collector:

ξ₆＝[0.5+2·(1-F₆/F)²](F/F₆)²＝[0.5+2×(1-43/46)²](46/43)²＝0.5819

g) the air inlet of the embodiment is in the form of a 'hemispherical dome' reducer, and xi is found by the formula (6), the formula (7) and the table B.0.9-4 of technical design Specification of mechanical draft cooling tower₇＝0.18；

h) The area of the inlet of the wind tube is 26m²Throat area 14.12m²Obtaining the ratio n of 1.84; taking the frictional resistance coefficient lambda of the on-way loss as 0.03, searching a graph B.0.10 of mechanical draft cooling tower process design specifications according to the fact that the tapered angle alpha is 120 degrees to obtain a gradually-reduced buffer coefficient K as 0.45, and substituting the resistance coefficient of the tapered section at the air duct inlet into the formula (8) and the formula (9):

i) from the outlet face of the wind tunnelProduct 25.53m²Throat area 14.12m²Obtaining the ratio n' of 1.81; the divergent angle alpha 'of the outlet is 60 degrees, K' is 0.95 found by a table B.0.11 of mechanical draft cooling tower process design specifications, and the resistance coefficients of the divergent section of the outlet of the air duct are obtained by substituting equations (10) to (14):

δ＝-0.05·(H'/D₀)+0.5＝-0.05·(1.26/4.24)+0.5＝0.485

ξ_{go out}＝1×(F_Larynx/F_{Go out})²＝1×(14.12/25.53)²＝0.3059

ξ₉＝(ξ_{Expanding device}+ξ_{Go out})·(1+δ)＝(0.195+0.3059)×(1+0.485)＝0.7438

j) In this example, a 1.0m gradient wave water-spraying filler was selected, and A was found from Table 3 in analysis of thermal and resistance properties of Plastic Water-spraying fillers for Cooling towers₁、A₂、A₃0.00054, 0.02372, 0.38310, m respectively₁、m₂、m₃0.00422, -0.12560 and 2.9710 respectively, substituting formula (16) and formula (17) to obtain A which is 9.2449 and m which is 2.05538, and calculating the resistance of the water spraying filler according to formula (15):

P_tl＝A·ρV^m＝9.2449×1.13×2.86^2.05538＝90.57Pa

the velocity v of each section can be obtained from the formula (18)_iAnd (3) substituting the formula (19) to obtain the total resistance of the cooling tower:

total resistance P of cooling tower_zTotal impedance of formula (20)

B. Calculating and determining actual working point parameters of the fan at different blade mounting angles when the fan works in the cooling tower: flow rate G_jWind pressure P_jPower N_jAnd efficiency η_fj。

FIG. 9 shows the performance curves of the air volume, the air pressure, the air volume and the power of the LF-42 type fan adopted in the cooling tower of the embodiment of the present invention, which are obtained by fitting, and the coefficient A of the performance curve equation with the blade installation angle of 13 degrees in the formula (21)₁₃、B₁₃、C₁₃、D₁₃Respectively-0.000069, 0.0057, -0.4205 and 24.4712, and the formula (21) is substituted to obtain a 13-degree blade installation angle air volume-air pressure performance curve equation of

P₁₃＝-0.000069G³+0.0057G²-0.4205G+24.4712

Obtaining coefficient A of a performance curve equation with the blade installation angle of 13 degrees through fitting₁₃’、B₁₃’、C₁₃’、D₁₃' respectively are 0.0005, -0.0723, 3.1266 and-24.1831, and are substituted into a formula (22), and the equation of the curve of the air volume-power performance of the fan with the installation angle of 13 degrees of blades is obtained as

N₁₃＝0.0005G³-0.0723G²+3.1266G-24.1831

And (3) substituting the total impedance S of the cooling tower into an equation (23) to obtain a pressure performance curve equation required by the cooling tower:

P＝0.00514G²

the intersection point of the required pressure performance curve and the wind pressure performance curve of the fan is the working point of the fan. The flow G of the actual operation working point of the 13-degree blade mounting angle obtained by solving the simultaneous equations is 45.3769 km³The wind pressure P is 10.6742m air columns, and the power N is 18.4877 kW.

The performance curves of the installation angles of the other blades of the fan are fitted by the method, one curve is fitted at intervals of 0.1 degrees from 2 degrees to 22 degrees, 201 performance curve equations are shared, the required pressure performance curve equation (23) is respectively combined, and 201 working point parameters are obtained by solving, as shown in fig. 10 and fig. 11.

The air volume, air pressure and power of the working points of the 201 blade installation angles of the fan are substituted into the formula (24) to calculate the efficiency of the working points of the 201 blade installation angles of the fan, and the curve is fitted as shown in fig. 12.

According to the data provided by the manufacturer, the three-phase asynchronous motor Y180L-4 is matched, the rated power is 22kW, the rated current is 43A, the motor efficiency is 90 percent, and the rotating speed is 1470 r/min. The cooling tower was equipped with a model LJ3 reducer, which was 92% efficient.

Taking a certain environmental condition as an example, the following calculation is performed:

environmental conditions are as follows: atmospheric pressure 100.56kPa, dry-bulb temperature: 27 ℃, wet bulb temperature: at 25 ℃, according to the cooling requirement of the equipment, the maximum temperature of water entering the tower is controlled to be 45 ℃, the temperature difference between water entering the tower and water leaving the tower is 10 ℃, and saturated vapor partial pressures P corresponding to 27 ℃ and 25 ℃ are obtained by substituting formula (25)_d”、P_sRespectively is

P_θ"＝10^0.55183＝3.5631kPa

P_τ"＝10^0.50045＝3.1655kPa

Substitution of formula (26) to obtain an air relative humidity of

Formula (27) is substituted to obtain the apparent density of the wet air under the working condition of

Substitution of formula (28) to obtain an air moisture content of

In order to obtain the balance working point of the cooling tower, trial calculation is carried out, and 3 groups of data are taken: (1) t is t₁＝46℃，t₂＝36℃，t_m＝41℃，λ＝0.39kg(DA)/kg；(2)t₁＝47℃，t₂＝37℃，t_m＝42℃，λ＝0.39kg(DA)/kg；(3)t₁＝48℃，t₂＝38℃，t_m43 ℃ and λ 0.39kg (da)/kg. Taking the first set of data as an example, the following is calculated:

substituting the related data into formula (29) to obtain the enthalpy of the wet air entering the tower as

h₁＝1.005θ+x(2500.8+1.846θ)＝1.005×27+0.0193×(2500.8+1.846×27)

＝76.362kJ/kg(DA)

The related data is substituted into a formula (33) to obtain the coefficient of heat taken away by the evaporated water quantity as

The enthalpy of the wet air discharged from the tower obtained by the formula (35) is

The average enthalpy of the humid air in the column is obtained from formula (36) as

Will t₁、t₂、t_mSubstituting the formula (25) to obtain the corresponding saturated vapor partial pressure P_t1”、P_t2”、P_t2Respectively is

P_t1"＝10^1.0036＝10.0832kPa

P_t2"＝10^0.77371＝5.939kPa

P_tm"＝10^0.89076＝7.776kPa

Substituting formula (30) to obtain respectively corresponding saturated air specific enthalpy of

The cooling number of the cooling tower obtained by substituting formula (40) is

Two additional sets of data were calculated according to the method described above, the calculations being shown in table 1:

TABLE 1 λ 0.39kg (DA)/kg balance point A calculation data Table

Finishing to obtain (1) t₂＝36℃,Ω_n＝1.0503；(2)t₂＝37℃,Ω_n＝0.8606；(3)t₂＝38℃,Ω_n0.7258. By fitting the curves through the 3 sets of data, as shown in FIG. 2：

Selecting 1.0m inclined gradient wave water spraying filler, finding B, k coefficient from table 2 in cooling tower plastic water spraying filler thermal and resistance performance analysis, substituting formula (31) to obtain filler characteristic number

Ω_n'＝Bλ^k＝1.60×0.39^0.64＝0.8758

To satisfy the cooling number omega_nIs equal to characteristic number omega_n', make omega_n＝Ω_n', solution of equilibrium point t₂36.9078 ℃. Therefore, the balance point A is obtained with coordinates of (0.39, 46.9078).

Taking 3 groups of data with lambda being 0.49kg (DA)/kg, (1) t₁＝43℃，t₂＝33℃，t_m＝38℃，λ＝0.49kg(DA)/kg；(2)t₁＝44℃，t₂＝34℃，t_m＝39℃，λ＝0.49kg(DA)/kg；(3)t₁＝45℃，t₂＝35℃，t_mλ 0.49kg (da)/kg at 40 ℃. Recalculating according to the above procedure, the specific calculation is shown in table 2:

TABLE 2 data sheet for the calculation of the lambda 0.49kg (DA)/kg balance point B

Finishing to obtain (1) t₂＝33℃,Ω_n＝1.4689；(2)t₂＝34℃,Ω_n＝1.1625；(3)t₂＝35℃,Ω_n0.9566. From this 3 sets of data, as in fig. 2, a curve was fitted:

the filler characteristic number is omega obtained by substituting formula (31)_n'＝Bλ^k＝1.60×0.49^0.641.0136. Let omega_n＝Ω_n', solution of equilibrium point t₂34.6691 ℃. So as to obtain another flatBalance point B, coordinate (0.49, 44.6691).

FIG. 3 shows a line connecting the equilibrium points A, B, where the equation for the straight line is t_1AB＝-22.387λ+55.63873。

The maximum temperature of the water entering the tower is controlled to be 45 ℃, and the temperature of the water entering the tower at the final approach point is t₁1 ═ 45 ℃, let t₁*＝t_1ABSubstituting the linear equation into the equation (41) at 45 deg.C to obtain the C' point λ of the equation (42)_C’0.4752kg (DA)/kg, point C' was determined as a linear change of A, B points, in turn as λ_C’0.4752kg (DA)/kg of the water temperature t of the tower outlet at the point C of the equilibrium point on the curve is obtained by recalculating the method₂When the temperature is 34.9708 ℃, the water temperature t is the temperature of the water entering the tower₁44.9708 deg.C, so that the coordinates of point C are (0.4752, 44.9708), and the formula (43) and | t are substituted_1C-t₁*|＝0.0292>0.01, the precision does not meet the requirement, and iterative calculation needs to be continued; comparing the positions of the points on the curve, the desired point of equilibrium T is located between the nearest points A, C, the AC line equation is set forth and T is used₁Substituting at 45 deg.C to obtain the abscissa of point D' as lambda_D’0.4739kg (DA)/kg, further expressed as lambda_DThe temperature t of the water taken out of the tower at the point D of the equilibrium point on the curve is obtained by recalculating the temperature t of the water taken out of the tower by the method₂35.0037 deg.C, D point coordinate of (0.4739, 45.0037), substitution formula (43), and | t |_1D-t₁*|＝0.0037<0.01, the precision meets the requirement, and the formula (44) is substituted to obtain

G_k＝λ_kQρ_w/(ρ_k10000) ═ 0.4739 × 800 × 1000/1.1569 ═ 32.7634 km³And/h, calculating the minimum ventilation quantity required by the environmental conditions at different time all the year according to the method.

The power of a fan shaft at a working point is 18.4877kW, the speed reducer is used for transmission, the output power of the motor is 20.0953kW, the load rate of the motor is 91.3%, the power is substituted into a formula (45) and a formula (46), and a table 1 in 'calculation of efficiency and power factor of the asynchronous motor under any load' is searched, so that the efficiency eta of the motor is obtained_emIs composed of

Substituting the values of the parameters of the working point into formula (47) to obtain the input power of the matched motor

The input power of the matching motor at different blade mounting angles of the fan in the cooling tower is calculated and fitted to form a curve as shown in fig. 13.

The operation time of the embodiment is week unit, statistics is carried out from the beginning of the year, and the corresponding motor input power of the fan meeting each air volume through the variable angle is calculated according to the air volume parameters required by different weeks all the year around. Since the power actually required in winter is much less than that of the LF-42 type fan at the minimum blade setting angle, for the accuracy of the fitting curve, the data source of the actual motor input power is divided into 3 segments: 1-19.5 weeks, 19.5-39.5 weeks and 39.5-52 weeks, the minimum required air volume of two sections of the two sides is less than the air volume when the minimum blade angle is 2 degrees, the input power of the matched motor is calculated according to the minimum blade angle of 2 degrees, and the fitting quadratic equation of the middle section is as follows:

N_esj＝-0.10887t²+6.5322t-80.0371

scheme I blade installation angle optimization operation all year around

Referring to the counted annual data, the blade mounting angle meeting the air volume is selected to operate according to the worst annual environmental working condition, and the blade mounting angle of 9.6 degrees is selected to operate all year round through calculation, wherein the input power of the motor is N₁18.0814kW, the formula (52) is replaced by the total annual operating energy consumption:

A_z＝168×N₁T＝168×18.0814×52＝157959kW·h

formula (50) was substituted for total annual energy costs:

Y_z＝A_zy 157959 × 0.6 94775 membered

Scheme two-year and all-year two-blade installation angle optimized operation

As shown in fig. 5, as can be seen from analyzing the data of this embodiment, the required air volume is relatively low and relatively long in part of the winter and the transitional season, and the input power of the motor matching the fan with the required air volume is less than the input power of the motor matching the fan at the minimum blade installation angle of 2 °, so that the angle of the fan is changed once, and the data source of the actual power is divided into 3 segments: the number of the fan blades is 1-19.5 weeks, 19.5-39.5 weeks or 39.5-52 weeks, the blade installation angle of the fan in the middle section is 9.6 degrees, and the two sections of fans on the two sides operate at the minimum blade installation angle of 2.0 degrees. When the blade with the installation angle of 2.0 degrees operates, the input power of the motor is N₂7.0589kW, the formula (49) is replaced by the total annual operating energy consumption:

formula (50) was substituted for total annual energy costs:

Y_z＝A_zy 98702 × 0.6 59221 membered

As shown in fig. 6, on the basis of the second scheme, the angle of the middle segment is changed again, at this time, N₁＝18.0814kW，N₃The input power of the motor corresponding to the intermediate section with the changed angle is N again as 7.0589kW₂By the equation of power required

Obtaining by solution:

the above formula is to N₂Derivation extremum

Find N₂13.1980kW, the corresponding fan blade installation angle is 7.0246 degrees, but the fan angle adjustment precision is 0.1 degree, so that 7.0 degree variable-angle operation is selected, namely, the operation time of the annual fan adopting three blade installation angles of 9.6 degrees, 7.0 degrees and 2.0 degrees is 23.4-36.6 weeks, 19.5-23.4 weeks, 36.6-39.5 weeks, 1-19.5 weeks and 39.5-52 weeks respectively, the minimum value of annual operation total energy consumption is 93130 kW.h, and the annual total energy cost is obtained by substituting formula (50):

Y_z＝A_zy 93130 × 0.6 55878 membered

Scheme four-blade mounting angle optimized operation in four whole years

As shown in fig. 7, in addition to the second embodiment, the second angle change is performed on the middle section of the required power curve, and the motor input powers corresponding to the two-blade installation angles are respectively N₂And N₃，N₁＝18.0814kW，N₄7.0589kW, power required by equation N₂＝-0.10887t²+6.5322t-80.0371N₃＝-0.10887t²+6.5322t-80.0371 to obtain:

let N₃<N₂Then 19.5<t_{3 small}<t_{2 small}<t_{2 is large}<t_{3 is large}<39.5 middle section power consumption

Total annual power consumption

And (3) solving a deviation and derivative extreme point of the formula:

find N₂＝15.1052kW，N₃The method is characterized in that the method is 11.3493kW, corresponding blade mounting angles are 7.9995 degrees and 6.0640 degrees, the angle adjusting precision of a fan is 0.1 degree, so that 8.0 degrees and 6.1 degrees are selected to operate at variable angles, the operating time of the fan in the whole year is 24.9-35.1 weeks, 22.2-24.9 weeks, 35.1-37.8 weeks, 19.5-22.2 weeks, 37.8-39.5 weeks, 1-19.5 weeks and 39.5-52 weeks respectively when the fan adopts four blade mounting angles of 9.6 degrees, 8.0 degrees, 6.1 degrees and 2.0 degrees, the minimum value of the electricity consumption in the whole year is 91014 kW.h, and the total energy cost in the whole year is obtained by substituting formula (50):

Y_z＝A_z91014 × 0.6 54608 yuan

Five-year blade mounting angle per week variable angle once optimized operation of scheme

As shown in fig. 8, the area between the power-required middle curve segment (19.5-39.5 th week) and the abscissa axis is solved by applying integration, which is the energy consumption of the continuous variable angle optimized operation of the middle segment fan:

the formula (49) is replaced by the following formula, namely the total energy consumption of the annual fan operation:

formula (50) was substituted for total annual energy costs:

Y_z＝A_zy 85962 × 0.6 51577 yuan

The annual cost results of the original operation scheme, the first scheme to the fifth scheme variable angle optimized operation scheme of the fan are compared as shown in the table 5. In table 5, the fan blade half-adjusting device requires 1000 yuan for one time of angle adjustment.

TABLE 5 annual cost comparison of different operating schemes for cooling tower fans

As shown in Table 5, the fan blade of the original scheme of the factory of the embodiment operates at 13 degrees, which causes a great deal of energy waste; in the first scheme, the fan blade installation angle is changed into 9.6 degrees for operation, and compared with the original scheme, 17.36 percent of energy is saved all the year round; the second scheme to the fourth scheme are respectively the 2, 3 and 4 blade installation angle variable-angle operation of the fan all the year around, and because the actual required air volume is less than the air volume of the selected fan at the minimum blade installation angle of 2 degrees in part of the winter and the transition season, compared with the first scheme, the energy cost can be greatly saved by adjusting the blade installation angle to be the minimum 2 degrees during the period; because the actually required power change in summer is relatively gentle in the embodiment, compared with the second scheme, the third scheme and the fourth scheme have better energy-saving effect, but the energy-saving effect is not obviously increased, and the angle modulation cost is increased along with the increase of the angle modulation times; and in the fifth scheme, the installation angle of the fan blade is adjusted for 1 time every week according to the environmental change, compared with the original scheme, the annual energy saving is 55.03 percent, but the annual angle adjustment cost is too large and complicated, the normal work of the cooling tower is influenced, and finally the third scheme is determined to be the optimal angle-changing optimized operation scheme according to the aim of minimizing the total cost of operation and angle adjustment, compared with the original scheme, the energy consumption of the third scheme is saved by 51.28 percent, and the total cost is saved by 47.79 percent.

For the embodiment, if the influence of the limitation of the minimum blade installation angle of the fan being 2 degrees is removed, only the conditions of 19.5-39.5 weeks in the middle section of the whole year are considered, and the cost of different angle-variable optimization operation schemes of the cooling tower fan is compared as shown in table 6.

TABLE 6 comparison of cost of different angle-variable optimized operation schemes of cooling tower fans in 19.5-39.5 weeks

As shown in table 6, in 19.5-39.5 weeks in the year, the energy cost of the cooling tower fan in the original scheme is 44110 yuan, and compared with the energy cost of the original scheme, the energy can be saved by 17.36% in the first scheme, 24.94% in the third scheme and 27.82% in the fourth scheme, and along with the increase of the number of the installation angles of the fan blades, the increase of the energy cost saving rate is obvious, so that if the installation angles of the fan blades of the fan can be continuously reduced or the variable-angle optimized operation is implemented for the case of other fans with variable angles generally in a normal range, the influence of the number of the installation angles of the fan blades of the whole year on the energy cost is very obvious.

In the fifth scheme, the fan is subjected to angle modulation for 1 time every week, the energy cost saving rate is improved by 6.87% -17.33% compared with the first scheme, the third scheme and the fourth scheme, but the half-regulation frequency of the fan is too high, the angle modulation cost is increased sharply, and as a result, the total cost is increased by 24.25%.

In conclusion, the annual variable-angle optimized operation scheme of the cooling tower fan determined by the method of the invention is scheme three: three blade mounting angles are adopted all the year round, so that the energy consumption is saved by 51.28%, the total cost is saved by 47.79%, a good energy-saving effect is achieved, and the blade mounting angle has good popularization and application values.

Claims

1. The method for determining the annual variable angle optimized operation scheme of the half-regulating fan of the cooling tower is characterized by comprising the following steps of:

step A: calculating total ventilation resistance P of cooling tower_zAnd the total impedance S;

and B: calculating and determining actual working point parameters of different blade mounting angles when the fan works in the cooling tower: flow rate G_jWind pressure P_jPower N_jAnd efficiency η_j；

And C: calculating and determining the minimum ventilation quantity required by the cooling tower under different environmental working conditions;

step D: calculating and determining a variable angle optimization operation scheme of the number of different blade installation angles of the cooling tower half-adjusting fan all the year round;

step E: comparing the cost of the numerical variable angle optimized operation scheme of the mounting angles of different blades of the cooling tower half-adjusting fan all the year round with the optimal variable angle optimized operation scheme;

step A total ventilation resistance P of the cooling tower_zThe solution to the total impedance S is as follows:

taking a counter-flow cooling tower as an example, the internal stress coefficient of the tower consists of an air inlet, an air guide device, an air flow turning part before entering a water spraying device, a water spraying device supporting beam, a water distribution device, a water collector, an air cylinder ring beam inlet, an air cylinder inlet reducing section and an air cylinder outlet diffusion section; the resistance of the water spraying filler is P_tl＝A·ρV^mPa, calculating the total ventilation resistance P of the cooling tower by accumulating the resistances of the parts_z，P_zSolution formula (2)

m gas column; solving formula of total impedance S

h²/(10⁸·m⁵) Wherein rho is the air density at normal temperature, kg/m³(ii) a V is the average flow velocity of air across the packing, m/s, A, m isDifferent packing resistance coefficients, i is the local resistance number of each part in the cooling tower, xi_iIs the local resistance coefficient of each part of the cooling tower, v_iThe average flow velocity of air in each section of the tower, wherein m/s and g are gravity acceleration and m/s²G is the ventilation flow of the cooling tower, ten thousand meters³/h；

And B, determining the flow G of the ith blade mounting angle actual working point when the fan works in the cooling tower_jAnd wind pressure P_jThe solution process of (2) is as follows: wind pressure performance curve equation of fan of simultaneous cooling tower

And equation of the curve P_z＝SG²When the fan runs, the wind pressure P of the fan_jEqual to the total resistance P of the cooling tower_zAnd solving to obtain the operation air volume G of the fan when the mounting angle of the jth blade of the fan in the cooling tower is obtained_jAnd wind pressure P_j(j ═ 1, 2, 3, …, m), where j is the fan blade setting angle number, m is the number of fan blade setting angles, P_jIs the wind pressure G at the setting angle of the jth blade of the fan_jThe air quantity of the blower at the setting angle of the jth blade, A_j、B_j、C_j、D_jIs a constant;

and B, determining the power N of actual working points of different blade mounting angles when the fan works in the cooling tower_jThe solution process of (2) is as follows: from the m air volumes G obtained_jRespectively substituting into the power performance curve equation of the corresponding blade installation angle of the cooling tower fanThere are m equations in total, where N_jPower, kW, A, for the setting angle of the jth blade of the fan_j’、B_j’、C_j’、D_j' is a constant;

and B, determining the efficiency eta of the actual working points of different blade installation angles when the fan works in the cooling tower_fjThe solving process is as follows: the obtained wind quantity G of the m blade installation angles of the fan in the cooling tower_jWind pressure P_jAnd power N_jAre respectively substituted into

Calculating the efficiency eta of the installation angle of m blades of the fan_fjM fan efficiencies η obtained by calculation_fjThe method comprises the steps of fitting a curve of air quantity-efficiency of a fan and a curve eta of air quantity-blade installation angle_fj＝η_fj(G) And beta_j＝β_j(G) In the formula, beta_jIs the j-th blade mounting angle, eta of the fan_fjThe mounting angle of the jth blade of the fan, namely the air volume is G_jEfficiency of the time;

c, calculating and determining the minimum ventilation quantity required by the cooling tower under different environment working conditions according to the following solving process:

(1) pressure of saturated water vapor

Wherein P' is saturated water vapor pressure, kPa, t is air temperature, DEG C;

(2) relative humidity of airWherein

Air relative humidity,%, theta is air dry bulb temperature, DEG C, tau is air wet bulb temperature, DEG C, P is atmospheric pressure, kPa, P_θ"is the partial pressure of water vapor in saturated air, kPa, P, when the air temperature is equal to theta DEG C_τ"is the saturated air water vapor partial pressure, kPa, at an air temperature equal to τ ℃;

(3) apparent density of humid air

Where ρ' is the apparent density of the humid air, kg/m³，ρ_dIs the apparent density of the dry air part in the wet air, kg/m³，ρ_sIs the apparent density of the water vapor portion in the humid air, kg/m³；

(4) Moisture content of air

kg/kg(DA)；

(5) Specific enthalpy of humidity h ═ 1.005 θ + x (2500.8+1.846 θ), kJ/kg (da);

(6) specific enthalpy of saturated air

kJ/kg (DA), wherein P_t"is the saturated air water vapor partial pressure, kPa, when the air temperature is equal to t ℃;

(7) calculating the thermodynamic calculation of the cooling tower by an enthalpy difference method, and establishing a packing characteristic number equation omega of the cooling tower_n'＝Bλ^kAnd cooling number equation of cooling tower

When omega is higher than_n’＝Ω_nThen, the air-water ratio lambda of the cooling tower under the actual environment working condition is obtained through calculation, wherein omega_n' is the characteristic number (dimensionless) of the working filler of the counter-flow cooling tower, omega_nThe working characteristic cooling number (dimensionless) of the counter-flow cooling tower is shown, and B, k is an experimental constant of the water spraying filler; k is the coefficient of heat removal of the evaporated water volume (K)<1.0, dimensionless), C_wThe specific heat of water is represented by kJ/(kg DEG C), 4.1868kJ/(kg DEG C) is taken, dt is the water temperature difference between inlet water and outlet water of the infinitesimal filler, DEG C, t₁For the temperature of the water entering the tower, t₂The water temperature at the outlet of the tower is DEG C; adopting a linear iterative approximation method in the calculation process until the error is within an allowable range, and finally solving the tower inlet water temperature t of the minimum required ventilation balance working point of the fan of the cooling tower₁The corresponding gas-water ratio, the method can quickly approach to obtain the final solution;

(8) minimum fan air volume G required by cooling tower under actual environment working condition_k＝λ_k·Q·ρ_w/(ρ_k·10000)，k is 1, 2, 3, …, z, wherein G_kIs the ventilation volume under the k environmental condition of ten thousand meters³/h，ρ_kIs the air density in kg/m under the k environmental condition³，ρ_WIs the density of the circulating water, kg/m³，λ_kThe mass ratio of air and water entering the packing under the k-th environmental working condition, kg (DA)/kg, Q is the total water flow, m³Z is the number of different environment working conditions;

and (7) determining the minimum required ventilation balance working point of the fan of the cooling tower under different environment working conditions in the following solving process:

setting a gas-water ratio lambda of the cooling tower₁Taking a plurality of different water temperatures t out of the tower₂Calculating a plurality of corresponding cooling numbers omega_nFitting into a curve; according to this lambda₁Calculating the cooling characteristic number (omega) of the trickle filler in the actual operation of the cooling tower_n’)₁In satisfying (omega)_n)₁＝(Ω_n’)₁Under the condition (f), the temperature (t) of the water discharged from the tower corresponding to the equilibrium point is obtained from the curve₂)₁The temperature (t) of the water entering the tower is obtained from the temperature difference between the water entering the tower and the water exiting the tower₁)₁And then (t) is₁)₁The desired water temperature in the column is not generally needed, and the problems now become: knowing the temperature t of the water entering the tower₁The temperature difference between water entering and leaving the tower requires the corresponding gas-water ratio lambda;

for a determined cooling tower filling system, an air-water ratio lambda is provided, and a corresponding tower inlet water temperature t is calculated₁，t₁Is a function of lambda, and the functional relation is set as a curve ATB, and a point T on the curve ATB is the coordinate (lambda, T) to be solved₁λ) cannot directly pass t₁Solving by adopting an iterative computation point-by-point approximation method: knowing that the curve ATB decreases monotonically, two points A, B of lower gas-water ratio and higher gas-water ratio are taken on the curve ATB, and the values of the gas-water ratios are lambda respectively_A、λ_BSetting the required water temperature t_1A>t₁*>t_1BAir-water ratio lambda_A、λ_BRespectively calculating the water temperature t of the inlet tower_1A、t_1BTwo points A and B on the curve ATB are determined, and an AB straight line passing through A, B is obtainedEquation t₁＝t₁(λ) is:

will t₁＝t₁Substituting, linear interpolation to obtain gas-water ratio lambda of corresponding C' point_CComprises the following steps:

by λ_CCalculating the actual tower inlet water temperature t of the equilibrium point C on the curve ATB by the methods (1) to (7)_1CComparing the calculated value t of the water temperature entering the tower_1CTo a predetermined value t₁Whether the difference meets the requirement of given precision of 0.01 or not, if not, checking that the point T on the curve ATB is positioned between two adjacent points A, C, calculating the linear equation passing through the two points AC by the same method, and calculating T₁＝t₁Substituting the linear equation of the AC two points, and linearly interpolating to obtain the gas-water ratio lambda of the corresponding D' point_DReuse λ_DCalculating and solving the actual tower inlet water temperature t of the balance point D on the curve ATB_1DCheck t_1DIf the accuracy requirement is met, … …, until the nth iteration calculation, the point N on the curve infinitely approaches the point T and meets the | T |_1N-t₁Until | ≦ 0.01, the method can quickly and iteratively approximate the solution t on the curve ATB₁Gas-water ratio lambda corresponding to lambda;

d, calculating and determining the variable angle optimization operation scheme of the annual different blade installation angle numbers of the half-adjusting fan of the cooling tower as follows:

(1) efficiency of motor under any loadWherein

η_emTo the motor efficiency; eta_NRated efficiency for the motor; epsilon is the motor load factor; k is the ratio of the fixed loss coefficient to the variable loss coefficient of the motor, and the size of k is as follows: the 2-pole asynchronous motor is 2; asynchronous motor with 4 poles and 6 polesIs 1; the number of 8 poles is 0.5; taking a week as a time unit all the year round, taking the maximum value of the minimum ventilation quantity of the fans required by the cooling tower at all the moments in the week as the operating working point of the fan set of the week, and the input power of the motor matched with the fan in the t week isSubstituting the fan working performance parameters determined in the step B into a formula, and calculating to obtain the input electric power N of the motor which runs for T weeks all the year_t(T ═ 1, 2, 3, …, T), where G_tVentilation at t week, ρ_tAir density at t week, g is acceleration of gravity, P_tThe operating wind pressure in the t-th week, eta_ftOperating Fan efficiency, η, for the t week_cFor the transmission efficiency, eta, of fans and associated motors_emtOperating the matched motor efficiency for the blower in the t week;

(2) annual operation energy consumption of cooling tower fan

Total annual operating cost Y_z＝A_zY, wherein A_zFor the annual operation power consumption of a fan of the cooling tower, kW.h, T is the annual operation frequency, T is the annual operation frequency, Y_zThe total annual energy cost is expressed as yuan, y represents the unit price of the electric charge, and yuan/(kWh & h);

determining the fan blade installation angle according to the minimum ventilation volume required by the cooling tower at different time intervals (in terms of weeks) all the year around, calculating to obtain the corresponding motor input power, performing curve fitting on the data all the year around to obtain the minimum input power N of the matched motor required by the variable-angle operation of the cooling tower fan under the actual environment working condition all the year around_rLaw of change with time t (weeks) using equation N_r＝N_r(t) represents, N_rThe power of the blade installation angle at the rated rotating speed of the fan corresponding to the minimum required ventilation quantity of the circumferential cooling tower;

in one year, the installation angle of the fan blade is changed, and the input power N of the matched motor in a corresponding time period_t(ii) a change; under the condition that the number of the blade installation angles adopted by the annual fan is certainThe method comprises the steps of setting out a calculation formula of the annual fan operation power consumption by taking the annual fan angle changing time points as variables, and finding out the annual fan operation power consumption A of the blade installation angle number through a derivation extremum solving method or an iterative calculation method_zObtaining the optimal variable angle optimal operation scheme of the fan with the annual blade mounting angle number by the minimum value and the optimal blade mounting angle and variable angle time point of the fan with the corresponding multiple variable angles; the number of the annual fan blade installation angles is changed, and the fan variable-angle optimized operation scheme of the annual different number of the fan blade installation angles is obtained as follows:

the first scheme is as follows: annual 1-type blade mounting angle optimized operation

Let the t-th summer₁The week is the worst environment working condition time all year round, the minimum ventilation quantity of the fan required at the moment is the maximum all year round, and the corresponding input power of the motor is N₁(ii) a The scheme is as follows₁The ventilation volume and the wind pressure of the week are selected from the fan types and the blade installation angles meeting the ventilation volume, and the corresponding annual operation power of the fan is N₁Can satisfy N₁≥N_rThe total annual fan running cost is Y_z＝A_z·y＝168×TN₁y；

Scheme II: annual 2-blade installation angle optimized operation

The scheme considers that the fan operates by adopting two blade mounting angles all the year round, and the input power of the matched motor is N respectively₁、N₂Is provided with N₁>N₂(ii) a Week 1 to t of the year_{2 small}Week and t_{2 is large}The ventilation quantity required by the cooling tower is smaller from the week to the Tth week, and the fan is adjusted to a smaller blade installation angle, so that the fan inputs power N by a matched motor₂Operate to satisfy N₂≥N_r，N₂Input power N of motor matched with minimum blade mounting angle of blower_min(ii) a At the t th_{2 small}Week to t_{2 is large}The ventilation quantity required by the cooling tower is large, and the fan is matched with the input power N of the motor₁The corresponding operation of a larger blade mounting angle meets N₂<N_r≤N₁The total annual fan operation cost is Y_Z＝A_Z·y＝168×{[T-(t_{2 is large}(N₂)-t_{2 small}(N₂))]·N₂+(t_{2 is large}(N₂)-t_{2 small}(N₂))·N₁Y, calculating the derivative extremum or iterative calculation of programming sequence to determine power N₂And further determining the corresponding fan blade setting angle and the time point t for changing the blade setting angle_{2 small}、t_{2 is large}The annual energy cost of the fan is minimized;

the third scheme is as follows: annual optimized operation of 3 blade mounting angles

In the scheme, the minimum input power of the matched motor required by the variable-angle operation of the fan in different seasons of the cooling tower all the year is greatly changed, three blade mounting angles are adopted for operation, and the minimum input power N corresponds to the input power N of the matched motor of the fan₁、N₂And N₃Is provided with N₁>N₂>N₃And N is₃≥N_min，N_minThe input power of a matched motor is the input power of the fan at the minimum blade installation angle, and the input power of the matched motor of the fan is a function of time, namely N (t); when the fan runs at the first blade mounting angle, the running time is from 1 st week to t th week_{3 small}Week and t_{3 is large}The minimum input power N of a motor matched with a fan required by ventilation of a cooling tower under actual environment working conditions from week to Tth week_r≤N₃All motors are supplied with input power N₃Running if the fan is matched with the input power N of the motor₃<N_minThen take N₃＝N_min(ii) a When the fan runs at the installation angle of the second blade, the running time is tth_{3 small}Week to t_{2 small}Week and t_{2 is large}Week to t_{3 is large}Week, satisfies N₃<N_r≤N₂All motors are supplied with input power N₂Running; when the fan operates at the installation angle of the third blade, the operation time is tth_{2 small}Week to t_{2 is large}Week, satisfies N₂<N_r≤N₁All motors are supplied with input power N₁The total operating cost of the fan all the year around is

The above formulas are respectively aligned with N₂、N₃Deriving extrema or solving for N by iterative calculation₂、N₃The corresponding installation angle and the angle change time point of the fan blade are further determined, so that the operation scheme is more energy-saving;

and the scheme is as follows: annual 4-blade installation angle optimized operation

Setting the fan to operate optimally according to four blade mounting angles all the year round except N of the worst working condition all the year round₁In addition, three operation powers N are set₂、N₃、N₄And the corresponding fan blade installation angle, listing the annual energy cost expression of the fourth scheme according to the method of the second scheme and the third scheme, optimally solving by adopting a derivative extreme value or iterative calculation method by taking the annual energy cost minimum of the fan unit as a target, and determining N₂、N₃、N₄The input power of the motors matched with the three fans and the corresponding fan blade mounting angles and variable angle time points can further reduce the operation energy consumption, and the optimal operation scheme that the fans operate according to five or six … … blade mounting angles all the year around can be solved by the same method;

and a fifth scheme: annual blade mounting angle once-per-week variable-angle optimized operation of semi-adjustable fan

The scheme aims at optimizing and operating the half-and-half adjusting fan by changing the angle once a year and a week, so that the air volume of the fan per week is exactly equal to the maximum value of the minimum ventilation required by the cooling tower in the week, and if the ventilation required by the cooling tower in the year is very small, the minimum input power of a fan matched motor required by the corresponding cooling tower is smaller than the input power N of a motor matched with the minimum blade installation angle of the fan of the model_minIn the meantime, the cooling tower fan should be in the 1 st week to the t th week_{m is small}Week and t_{m is large}At the minimum blade mounting angle and at the power N within the period from the week to the Tth week_minRunning; the total annual running cost of the fan is

E, comparing the cost of the annual different blade installation angle number variable angle optimization operation scheme of the cooling tower half-adjusting fan with the optimal variable angle optimization operation scheme, wherein the process comprises the following steps:

the annual cost of different angle-variable optimization operation schemes of the cooling tower fan comprises energy cost and angle modulation cost, and the angle modulation cost is calculated in an accumulated mode according to the number of the blade installation angles of the operation schemes; in the fifth scheme, the blade installation angle is optimally operated once a week, the fan with half-regulated blades is greatly wasted in angle regulation once a week, the normal work of a cooling tower is influenced, and the cooling tower is not practical; and finally, comparing annual energy and angle modulation total cost of 6 operation schemes including the original operation scheme and the first, second, third, fourth and fifth operation schemes, and finally determining the optimal angle modulation optimization operation scheme of the cooling tower fan on the basis of the minimum total cost.