阅读说明：本技术 一种船舶冷却系统的泵流模式和自流模式的双模式切换方法 (Dual-mode switching method for pump flow mode and gravity flow mode of ship cooling system ) 是由 李献领 柯志武 陶模 陈朝旭 冯毅 郑伟 周宏宽 刘伟 姚涌涛 代路 吴君 李 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种船舶冷却系统的泵流模式和自流模式的双模式切换方法,包括以下步骤：1)确定冷却系统的冷凝器的要求真空,以压力表示；2)设定真空值p-(ref)作为泵流模式、自流模式的标识；3)设计泵流模式的启动和退出规则；当检测的冷凝器内的真空值大于设定值且保持N个采样周期以上,则冷却系统保持泵流模式,或从自流模式切换为泵流模式；当检测的冷凝器内的真空值小于设定值且保持N个采样周期以上,则冷却系统保持自流模式,或从泵流模式切换为自流模式。本发明提供了两种切换模式,满足自流航速区间最大化或真空环境最佳,可分别满足节能、降噪效果最佳和运行真空环境最佳的性能需求,有助于冷却系统多目标运行的实现。(The invention discloses a dual-mode switching method of a pump flow mode and a self-flow mode of a ship cooling system, which comprises the following steps: 1) determining a required vacuum, expressed as a pressure, of a condenser of a cooling system; 2) setting a vacuum value p ref As an indicator of pump flow mode, self flow mode; 3) designing a starting and exiting rule of a pump flow mode; when the detected vacuum value in the condenser is larger than the set value and keeps more than N sampling periods, the cooling system keeps the pump flow mode or is switched to the pump flow mode from the self-flow mode; and when the detected vacuum value in the condenser is smaller than the set value and is kept for more than N sampling periods, the cooling system is kept in the self-flowing mode, or the pump flow mode is switched to the self-flowing mode. The invention provides two switching modes, meets the maximization of the self-flow navigational speed range or the optimal vacuum environment, can respectively meet the performance requirements of energy conservation, optimal noise reduction effect and optimal operation vacuum environment, and is beneficial to the realization of multi-target operation of a cooling system.)

1. A dual-mode switching method for a pump flow mode and a gravity flow mode of a ship cooling system is characterized by comprising the following steps: the method comprises the following steps:

1) determining a required vacuum for a condenser of a cooling system, the required vacuum being expressed in terms of pressure, and p₀- Δ p. ltoreq. vacuum. ltoreq.p₀+ Δ p; wherein p is₀Is the nominal true of the condenserNull, Δ p is the allowable vacuum offset value, p₀+ Δ p is the upper vacuum limit of the condenser, p₀- Δ p is the lower vacuum limit of the condenser;

2) setting a vacuum value p_refAs an indicator of a transition of the pump flow mode, gravity flow mode cooling system, wherein:

if the widest range of the navigational speed in the gravity flow mode is taken as the target, the methodα is a limited overshoot, and

if the vacuum environment of the condenser is optimized as the target, p_ref＝p₀；

3) Determining a switching rule of a pump flow mode;

when the detected vacuum value in the condenser is larger thanIf the sampling period is more than N, the cooling system keeps the pump flow mode, or the self-flow mode is switched to the pump flow mode;

when the detected vacuum value in the condenser is less thanIf the sampling period is kept to be more than N, the cooling system keeps the self-flowing mode, or the pump flow mode is switched to the self-flowing mode;

the water pump is at zero rotation speed in the self-flow mode of the cooling system, the rotation speed of the water pump is greater than zero in the pump flow mode, and N is a positive integer.

2. The dual-mode switching method between the pump flow mode and the gravity flow mode of the ship cooling system according to claim 1, wherein the output of the controller of the cooling system is the rotation speed n of the water pump, the lower limit of n is zero, and the upper limit is the full rotation speed of the water pump.

3. The dual-mode switching method for the pump flow mode and the gravity flow mode of the ship cooling system as claimed in claim 1, wherein the controller of the cooling system is designed to realize that the vacuum overshoot does not exceed a so as to ensure that the vacuum value of the condenser does not exceed p when the pump flow mode and the gravity flow mode of the cooling system are switched₀+ Δ p such that the rise time is no greater than Ψ to ensure a sufficiently fast dynamic response of the vacuum control of the cooling system.

4. The dual-mode switching method for the pump flow mode and the gravity flow mode of the ship cooling system according to claim 1, wherein α is 0.15.

5. The dual-mode switching method for the pump flow mode and the gravity flow mode of the ship cooling system according to claim 1, wherein N-5.

6. The dual-mode switching method between the pump flow mode and the gravity flow mode of the ship cooling system according to claim 1, wherein in step 3), it is first checked whether the rotation speed of the water pump is zero, if so, the cooling system is in the gravity flow mode, otherwise, the cooling system is in the pump flow mode;

if the cooling system is in the self-flowing mode, whether the entering condition of the pump flow mode is met or not is judged by detecting the vacuum of the condenser, if so, the cooling system is switched to the pump flow mode, and if not, the self-flowing mode is kept;

if the cooling system is in the pump flow mode, whether exit conditions of the pump flow mode are met or not is judged by detecting the vacuum of the condenser, if yes, the cooling system enters the self-flow mode, and if not, the pump flow mode is kept.

Technical Field

The invention belongs to the technical field of ship power plant control, and particularly relates to a dual-mode switching method for a pump flow mode and a self-flow mode of a ship cooling system.

Background

The condensing steam turbine is used as a power system of a ship, and a cooling water system of the condensing steam turbine is one of the most important subsystems and is used for condensing exhaust steam generated by the work of the steam turbine and maintaining the vacuum condition required by the work of the steam turbine. The gravity flow mode cooling system is a novel cooling water system, is different from a traditional pump flow mode cooling water system, does not depend on the operation of a water pump during working, is relatively energy-saving, can greatly reduce the noise of the cooling water system, and is an important development direction of the cooling water system of the ship power device. As shown in fig. 1, the self-flow cooling system generally comprises an inlet connection pipe and a flow guide cover, an outlet connection pipe and a flow guide cover, a condenser, a connecting pipeline, an accessory and the like, wherein dynamic pressure of head-on water flow during ship navigation is converted into internal flow static pressure of a cooling water system through the inlet and outlet connection pipe and the flow guide cover on a ship board side, cooling seawater is driven to flow through the condenser, and dead steam generated by a steam turbine doing work is condensed to meet the cooling requirement of a power device. When the water pump is started, the cooling system enters a pump flow mode, and when the water pump stops or follows up, the cooling system enters a self-flow mode.

During the sailing process of the ship, the flow rate of the cooling seawater passing through the self-flowing mode cooling system depends on the sailing speed of the ship, and the flow rate of the cooling seawater of the self-flowing mode cooling system is increased along with the increase of the sailing speed of the ship, namely the cooling capacity is gradually increased. The operation condition of the power device directly influences the flow of the dead steam entering the condenser, and the flow of the cooling seawater needed by the condenser is determined, namely the cooling requirement of the power device is determined. The free-flowing mode cooling system is only applicable when the cooling capacity of the free-flowing mode cooling system is not less than the cooling demand of the power plant. The running working condition of the power device also determines the rotating speed of a propeller of the ship, and the rotating speed of the propeller directly influences the ship speed and the cooling capacity of the gravity flow mode cooling system, so the ship speed is usually used as an identification parameter in the design stage, and the cooling seawater temperature t is used as an external condition, so that the ship speed area v is in the ship speed area₁-v₂The in-range free-flow mode cooling system has applicability. Out of range v of speed₁-v₂In time, the gravity flow mode cooling system cannot provide enough cooling seawater flow, and a water pump needs to be started to be switched into the pump flow mode cooling system. However, since the cooled seawater temperature t varies in different sea areas, the free-flow cruise zone v₁-v₂The timing of switching the gravity flow mode cooling system to the pump flow mode cooling system is dynamically controlled, and the switching process is required to ensure that the vacuum always meets the requirement and the reciprocating switching near the switching point cannot occur, otherwise, the system cannot stably run。

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a dual-mode switching method of a pump flow mode cooling system and a gravity flow mode cooling system, which can realize two switching modes of the gravity flow navigational speed range maximum switching, the vacuum environment optimal switching and the like, and can meet the diversified operation requirements of the cooling systems adapting to different environments.

To achieve the above object, according to one aspect of the present invention, there is provided a dual mode switching method of a pump flow mode and a free flow mode of a ship cooling system, characterized in that: the method comprises the following steps:

1) determining a required vacuum for a condenser of a cooling system, the required vacuum being expressed in terms of pressure, and p₀- Δ p. ltoreq. vacuum. ltoreq.p₀+ Δ p; wherein p is₀Is the nominal vacuum of the condenser, Δ p is the allowable vacuum offset, p₀+ Δ p is the upper vacuum limit of the condenser, p₀- Δ p is the lower vacuum limit of the condenser;

2) setting a vacuum value p_refAs an indicator of a transition of the pump flow mode, gravity flow mode cooling system, wherein:

if the widest range of the navigational speed in the gravity flow mode is taken as the target, the methodα is a limited overshoot, and

if the vacuum environment of the condenser is optimized as the target, p_ref＝p₀；

3) Determining a switching rule of a pump flow mode;

when the detected vacuum value in the condenser is larger thanIf the sampling period is more than N, the cooling system keeps the pump flow mode, or the self-flow mode is switched to the pump flow mode;

when the detected vacuum value in the condenser is less thanIf the sampling period is kept to be more than N, the cooling system keeps the self-flowing mode, or the pump flow mode is switched to the self-flowing mode;

the water pump is at zero rotation speed in the self-flow mode of the cooling system, the rotation speed of the water pump is greater than zero in the pump flow mode, and N is a positive integer.

Preferably, the output of the controller of the cooling system is the rotational speed n of the water pump, the lower limit of n being zero and the upper limit being the full rotational speed of the water pump.

Preferably, the controller of the cooling system is designed to realize that the vacuum overshoot does not exceed alpha so as to ensure that the vacuum value of the condenser does not exceed p when the cooling system is switched between the pump flow mode and the gravity flow mode₀+ Δ p such that the rise time is no greater than Ψ to ensure a sufficiently fast dynamic response of the vacuum control of the cooling system. Preferably, α is 0.15.

Preferably, N ═ 5.

Preferably, in step 3), firstly, checking whether the rotating speed of the water pump is zero, if so, the cooling system is in a self-flow mode, otherwise, the cooling system is in a pump flow mode;

if the cooling system is in the self-flowing mode, whether the entering condition of the pump flow mode is met or not is judged by detecting the vacuum of the condenser, if so, the cooling system is switched to the pump flow mode, and if not, the self-flowing mode is kept;

if the cooling system is in the pump flow mode, whether exit conditions of the pump flow mode are met or not is judged by detecting the vacuum of the condenser, if yes, the cooling system enters the self-flow mode, and if not, the pump flow mode is kept.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects: the dual-mode switching method of the pump flow mode and the gravity flow mode cooling system provided by the invention determines the switching identifier and the switching rule aiming at the switching problem of the pump flow mode and the gravity flow mode cooling system of the ship power device, designs the corresponding controller, gives a specific switching flow, can realize the automatic switching of the pump flow mode and the gravity flow mode, and meets the cooling requirements of the cooling system under different working environments. And according to the difference of the vacuum conversion marks, two switching modes are provided, the maximum conversion of the free-flow speed range and the optimal conversion of the vacuum environment can respectively meet the performance requirements of energy conservation, optimal noise reduction effect and optimal operation vacuum environment, and the realization of multi-target operation of the cooling system is facilitated.

Drawings

FIG. 1 is a block diagram of the components of a cooling system according to an embodiment of the present invention;

FIG. 2 is a diagram of a pump flow mode cooling system control loop according to an embodiment of the present invention;

FIG. 3 is a closed loop pole distribution diagram of a control system in a pump flow mode according to an embodiment of the present invention;

FIG. 4 is a flow chart illustrating switching between a pump flow mode and a self-flow mode according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, a structural diagram of a cooling system according to an embodiment of the present invention includes a steam turbine, a condenser, and a water pump, where after the steam passes through the steam turbine, the formed exhaust steam flows into the condenser, and the water pump can transport seawater to the condenser, so that the exhaust steam is condensed to form condensed water.

The invention discloses a dual-mode switching method of a pump flow mode and a self-flow mode of a ship cooling system, which comprises the following steps:

1) determining a required vacuum for a condenser of a cooling system, the required vacuum being expressed in terms of pressure, and p₀- Δ p. ltoreq. vacuum. ltoreq.p₀+ Δ p; wherein p is₀Is the nominal vacuum of the condenser, Δ p is allowedDeviation from vacuum value, p₀+ Δ p is the upper vacuum limit of the condenser, p₀- Δ p is the lower vacuum limit of the condenser; the required vacuum is the vacuum allowed in the condenser, and cannot exceed p₀+ Δ p, nor less than p₀-Δp。

2) Setting a vacuum value p_refAs an indicator of a transition of the pump flow mode, gravity flow mode cooling system, wherein:

if the widest range of the navigational speed in the gravity flow mode is taken as the target, the methodα is a limited overshoot, andthe value of alpha is such that p is ensured_refMaximum value of (1) is p₀+Δp，p_refMinimum value of p₀，p_refAnd should not be outside this range. Preferably, α is 0.15. p is a radical of_refThe value range is determined by the system design and is also the working requirement condition of the steam turbine of the ship cooling system.

If the vacuum environment of the condenser is optimized as the target, p_ref＝p₀；

P of the invention_refThe value of (a) is mainly based on two considerations: firstly, when the vacuum degree is the lowest, the required cooling water quantity is the smallest, so that the cooling requirement can be met through a self-flowing mode in the widest navigational speed range; second is p_refAnd the value of the alpha is matched, so that the influence of vacuum fluctuation is fully considered, and the requirement of the steam turbine on the vacuum degree is met.

3) Determining a switching rule of a pump flow mode;

when the detected vacuum value in the condenser is larger than(alpha is 1.075p when 0.15_ref) And keeping N equal to more than 5 sampling periods, the cooling system keeps the pump flow mode (if not more than 5 sampling periods)The pump flow mode is maintained when the flow rate is in the pump flow mode), or the self-flow mode is switched to the pump flow mode (for example, the flow rate is not more than the pump flow rate)When the flow is in the self-flow mode, the flow is switched to the pump flow mode);

when the detected vacuum value in the condenser is less than(0.925 p when α is 0.15)_ref) And N is kept more than 5 sampling periods, the cooling system is kept in the free-flow mode (e.g., no less thanWhen the pump is in the free-flow mode, the free-flow mode is maintained), or the pump flow mode is switched to the free-flow mode (for example, the pump flow mode is not less than the free-flow mode)When the flow is in the pump flow mode, the flow is switched to the self-flow mode);

by interval(0.15 when alpha is 0.925p_ref,1.075p_ref]) The delay interval for switching the judgment is that the cooling system can be in a pump flow mode or a self-flow mode in the interval.

The water pump is at zero rotation speed in the self-flow mode of the cooling system, the rotation speed of the water pump is greater than zero in the pump flow mode, and N is a positive integer.

The design method of the controller of the cooling system in the pump flow mode comprises the following steps: the closed loop poles are ensured to be distributed in a reasonable range; the controller of the cooling system in the pump flow mode is shown in fig. 2, the output n of the controller is the water pump rotating speed, the lower limit of n is zero, and the upper limit is the full rotating speed, wherein when n is the zero rotating speed, the cooling water system is in the gravity flow mode. The closed loop poles of the controller of fig. 2 are distributed in the s-plane as shown in fig. 3Cross-hatched area of the left half-plane where xi takes the value 0.51, ω_nTaking the value of 0.03, and ensuring that the vacuum overshoot of the gravity flow mode cooling system is not more than 15%; meanwhile, the rise time is also guaranteed to be not more than 60 seconds.

Further, the output of the controller of the cooling system is the rotating speed n of the water pump, the lower limit of the n is zero rotating speed, and the upper limit is full rotating speed of the water pump;

the vacuum overshoot of the cooling system does not exceed alpha so as to ensure that the vacuum value of the cooling system does not exceed p when the pump flow mode and the gravity flow mode are switched₀+ Δ p such that the rise time is no greater than Ψ to ensure a sufficiently fast dynamic response of the vacuum control of the cooling system. Psi and alpha are chosen to ensure that the engineering requirements are met.

Referring to fig. 4, it is a specific flowchart of dual mode switching of the pump flow mode and the gravity flow mode cooling system according to the embodiment of the present invention: firstly, whether the rotating speed of the water pump keeps zero or not is checked, if the rotating speed keeps zero, the cooling system is in a self-flow mode, and otherwise, the cooling system is in a pump flow mode. And if the cooling system is in the pump flow mode, judging whether the exit condition of the pump flow mode is met or not by detecting the vacuum of the condenser, if so, entering the self-flow mode by the cooling system, and otherwise, keeping the pump flow mode. And if the cooling system is in the self-flow mode, judging whether the entering condition of the pump flow mode is met or not by detecting the vacuum of the condenser, if so, converting the cooling system into the pump flow mode, and otherwise, keeping the self-flow mode.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.