A marine steam turbine drainage system

Abstract

The present application relates to a kind of marine steam turbine drainage system, including main steam pipeline, warm-up branch, the main steam pipeline, containing temperature sensor, pressure sensor, drainage distribution valve, cut-off valve, main valve;Main steam is divided into two ways by drainage distribution valve: one way is connected steam turbine through cut-off valve, pressure reducing orifice, warm-up valve;The other way is connected with main valve;Drainage distribution valve is three-way valve, can switch connection main steam pipeline to cut-off valve or main valve;The warm-up branch contains dehumidification device, pressure reducing orifice, warm-up valve, drain trap;Dehumidification device is connected in series in the pipeline between cut-off valve and pressure reducing orifice, and is connected steam turbine by drain trap;Pressure reducing orifice is connected steam turbine by warm-up valve.The present application can effectively utilize the low-parameter steam of high humidity and low pressure in starting stage.Shorten steam turbine warm-up time, increase steam turbine service life, improve steam turbine maneuverability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of marine power equipment, in particular to a new drainage system for shortening the warm-up time of a steam turbine by optimizing the use of low-parameter steam. BACKGROUND

[0002] Marine steam turbines are key equipment of marine power and electric power systems, and are one of the important prime movers on a ship.

[0003] When a marine steam turbine is started in a cold state, a long warm-up time is needed. That is, dry steam with a small flow rate and a high temperature is introduced into the flow structure of the steam turbine through a main steam valve and a regulating valve, so that the temperature of the cylinder and rotor of the steam turbine gradually rises. The warm-up can effectively release the thermal stress of the steam turbine when it is started in a cold state, and increase the service life of the steam turbine.

[0004] A steam system on a ship supplies steam to the steam turbine. During the process of starting the system from a cold state to outputting rated steam parameters, there is a long period of time during which the output steam has a low pressure and a small dryness. Although this steam has a certain temperature, it cannot be used for warm-up of the steam turbine. If the steam turbine is started (the main steam valve is opened) when the steam parameters have not reached the rated values, wet steam will enter the steam turbine, which can easily cause a water hammer accident and damage the bearings and blades of the steam turbine.

[0005] Therefore, the low-parameter steam is generally returned to the boiler after the residual water vapor in the purge pipeline is removed, and is reused. Only when the steam parameters reach the rated parameters and the steam is dry steam, can the steam turbine be started, so that a small amount of steam enters the steam turbine for warm-up. As shown in the schematic diagram of a conventional steam pipeline and drainage management. Figure 1 Figure 1 The pressure sensor 21, the temperature sensor 22, the drainage valve 23, the main steam valve 24, and the steam turbine 25 are shown in the figure. The pressure sensor and the temperature sensor are used to determine whether the steam parameters have reached the rated parameters. If the rated parameters have not been reached, the drainage valve is opened, so that the low-parameter steam is returned to the system. After the steam parameters are reached, the main steam valve is opened, the drainage valve is closed, and the steam turbine starts to warm up.

[0006] ​Traditional marine steam turbine needs to wait for steam parameters to reach the standard before warming up, resulting in too long start-up time. For example, the prior art relates to a marine steam turbine start-up warming control system, which monitors steam parameters in real time through pressure sensors and temperature sensors, and controls the opening time of the main steam valve to avoid wet steam entering the steam turbine. The disadvantage is that the warming relies on high-parameter dry steam, which cannot utilize low-parameter steam, resulting in long warming time. The existing drainage system can separate water, but does not solve the problem of recycling low-parameter steam. For example, the prior art discloses a steam turbine drainage device, which separates water in wet steam through multi-stage dehumidification grids, and discharges condensed water through a drainage valve. It does not involve the technology of pre-warming by low-parameter steam, and does not integrate a pressure-reducing orifice to optimize steam dryness. For example, the prior art discloses a self-adaptive pressure-reducing valve structure, which adjusts the opening degree of the orifice to realize steam pressure regulation, but does not design valve switching logic in combination with the warming process, so it cannot realize the recycling of low-parameter steam. Moreover, the pressure-reducing control precision is insufficient.

[0007] Therefore, it is necessary to design a new marine steam turbine drainage system, which realizes efficient warming by integrating multi-stage valves and parameter feedback control. SUMMARY

[0008] The present application is to propose a new marine steam turbine drainage system, which can effectively utilize low-parameter steam with high humidity and low pressure during the start-up stage, shorten the warming time of the steam turbine, increase the service life of the steam turbine, and improve the maneuverability of the steam turbine.

[0009] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows: a marine steam turbine drainage system, comprising: a main steam pipeline, a warming branch,

[0010] The main steam pipeline comprises a temperature sensor, a pressure sensor, a drainage distribution valve, a cutoff valve, and a main steam valve. The main steam is divided into two paths through the drainage distribution valve: one path connects the cutoff valve, a pressure-reducing orifice, and a warming valve to the steam turbine; the other path connects the main steam valve. The drainage distribution valve is a three-way valve that can switch the connection of the main steam pipeline to the cutoff valve or the main steam valve;

[0011] The warming branch comprises a dehumidification device, a pressure-reducing orifice, a warming valve, and a steam trap. The dehumidification device is connected in series in the pipeline between the cutoff valve and the pressure-reducing orifice, and connects the steam turbine through the steam trap. The pressure-reducing orifice connects the steam turbine through the warming valve.

[0012] Further, the warming valve is a three-state valve that connects the downstream of the pressure-reducing orifice to a cylinder exhaust, a flow-through structure, or a closed pipeline.

[0013] Further, the dehumidification device has multiple layers of corrugated dehumidification grids, the inlet is connected to the cutoff valve, and the outlet is divided into two paths: one path connects to the cylinder exhaust through the steam trap, and the other path connects to the warming valve through the pressure-reducing orifice.

[0014] Further, the hole diameter of the pressure reducing orifice plate is designed according to the rated parameters of the steam turbine, so that the dryness of the steam is increased to the supercritical state after the steam pressure is reduced.

[0015] Further, the valve rod position of the warming valve is controlled by the feedback signals of the downstream temperature sensor and the pressure sensor.

[0016] Further, the grinding sealing surface is used between the valve rod and the shell of the drain distribution valve, so that no steam leakage is ensured.

[0017] Further, during the cold start stage of the steam turbine, the drain distribution valve guides the steam to the warming branch, and the warming valve switches the reduced pressure steam to the cylinder exhaust or flow-through structure, so that the staged preheating is realized.

[0018] A control method based on a marine steam turbine drain system, comprising the following steps:

[0019] (1) detecting the temperature and pressure of the main steam pipeline;

[0020] (2) when the steam is wet steam, opening the drain distribution valve to the warming branch, and adjusting the steam parameters through the dehumidifying device and the pressure reducing orifice plate;

[0021] (3) when the reduced pressure steam reaches the dry steam condition, switching the warming valve to the flow-through structure for pre-warming.

[0022] Further, after the steam turbine reaches the preheating threshold, the warming branch is closed and the drain distribution valve is switched to the main valve, so that the rapid start is realized.

[0023] Further, after the system is normally operated, the two cutoff valves are closed to block the drain branch leakage.

[0024] The beneficial effects of the present application are:

[0025] The present application provides a new marine steam turbine drain system, which can effectively utilize the low-parameter steam with high humidity and low pressure during the start-up stage by using the drain distribution valve, the dehumidifying device, the drain trap, the pressure reducing orifice plate and the warming valve. The warming time of the steam turbine is shortened, the service life of the steam turbine is increased, and the maneuverability of the steam turbine is improved. The dryness of the low-parameter steam is increased to the usable level by the combination of the three-way valve and the pressure reducing orifice plate. The valve control strategy based on the sensor feedback is adopted to realize the leakage-free switching. The staged preheating reduces the thermal stress of the steam turbine by 50%, and prolongs the service life. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of a traditional steam pipeline and a drain pipeline;

[0027] Figure 2 is a whole structure diagram of the marine steam turbine drain system of the present application;

[0028] Figure 3 is a schematic diagram of a hydrophobic distribution valve structure;

[0029] Figure 4 is two working states of a hydrophobic distribution valve;

[0030] Figure 5 is a schematic diagram of a warm-up valve structure;

[0031] Figure 6 is a switching principle of three working states of a warm-up valve;

[0032] Figure 7 is an internal grid layout of a dehumidifying device.

[0033] DETAILED DESCRIPTION

[0034] As shown in Figure 2 , a new marine steam turbine hydrophobic system is provided by the embodiment of the present application, which is composed of temperature sensors one and two 1, 7, pressure sensors one and two 2, 8, a hydrophobic distribution valve 3, cut-off valves one and two 4, 12, a dehumidifying device 5, a pressure reduction orifice plate 6, a hydrophobic trap 9, a main steam valve 10, and a warm-up valve 11.

[0035] Among them, the main steam pipeline includes temperature sensor one 1, pressure sensor one 2, hydrophobic distribution valve 3, cut-off valve one 4, cut-off valve two 12, and main steam valve 10. One steam outlet of the hydrophobic distribution valve 3 is connected to the steam turbine through the cut-off valve one 4, the pressure reduction orifice plate 6, the warm-up valve 11, and the cut-off valve two 12. The other steam outlet of the hydrophobic distribution valve 3 is connected to the main steam valve 10.

[0036] The hydrophobic distribution valve 3 is a three-way valve, which can switch to connect the main steam pipeline to the cut-off valve one 4 or the main steam valve 10.

[0037] The warm-up branch includes the dehumidifying device 5, the pressure reduction orifice plate 6, the warm-up valve 11, and the hydrophobic trap 9. The dehumidifying device 5 is connected in series to the pipeline between the cut-off valve one 4 and the pressure reduction orifice plate 6, and is connected to the steam turbine through the hydrophobic trap 9. The pressure reduction orifice plate 6 is connected to the steam turbine through the warm-up valve 11.

[0038] As shown in Figure 3 , the hydrophobic distribution valve 3 is composed of a bottom plate 3-1, a shell 3-2, a valve stem 3-3, and an actuator 3-4. The valve stem 3-3 placed in the bottom plate 3-1 and the shell 3-3 is connected to the actuator 3-4.

[0039] The steam distribution valve 3 has two operating states. When the valve stem 3-3 is in its uppermost position, the steam inlet connects to the isolation valve 4 port. When the valve stem 3-3 is in its lowermost position, the steam inlet connects to the main steam valve 10. It is essentially a three-way valve. A ground surface 3-5 is located between the valve stem 3-3, the base plate 3-1, and the housing 3-3 to prevent steam leakage. Figure 4 Two working states are given in the figure: (a) the valve stem is at the top and (b) the valve stem is at the bottom.

[0040] like Figure 5 As shown, the warm-up valve 11 consists of a warm-up valve base plate 11-1, a sleeve 11-2, a warm-up valve housing 11-3, a sleeve valve stem 11-4, and a warm-up valve actuator 11-5. The upper end of the warm-up valve housing 11-3 is fixedly connected to the warm-up valve base plate 11-1. Inside, the sleeve 11-2 connects to the sleeve valve stem 11-4, which in turn connects to the warm-up valve actuator 11-5.

[0041] The warm-up valve 11 has three working states. When the valve stem moves to the bottom, the downstream interface of the pressure reducing orifice 6 is connected to the discharge cylinder; when the valve stem moves to the top, the downstream interface of the pressure reducing orifice 6 is connected to the flow. Figure 6 Three working states are given in the figure: (a) valve stem to the bottom, (b) valve stem to the top, and (c) valve stem to the middle.

[0042] like Figure 7 As shown, the dehumidification device 5 is composed of a dehumidification grid 5-1 and a shell 5-2, and has three interfaces, the inlet is from the isolation valve 4, and the outlet leads to the steam trap 9 and the pressure reducing orifice plate 6.

[0043] During operation, the marine steam turbine drain system of the present invention controls the drain distribution valve 3 through the readings of the pressure sensor 2 and the temperature sensor 1. During the startup phase, when the steam pressure and temperature are low and the steam is wet, the drain distribution valve 3 connects the steam inlet with the isolation valve 4, and the steam flows to the isolation valve 4. The low-parameter steam enters the dehumidification device 5 through the isolation valve 4, and the entrained water droplets enter the turbine exhaust cylinder through the drain valve 9, and then enter the condenser through the exhaust cylinder to re-circulate the water vapor, and the low-parameter steam dryness increases. The steam then passes through the pressure reducing orifice 6, the steam enthalpy value remains unchanged, the pressure drops, and the dryness increases accordingly.

[0044] The steam parameters after the pressure reducing orifice plate are monitored by pressure sensor two 8 and temperature sensor two 7. When the steam temperature is low, the steam is saturated steam and wet steam, and the warm-up valve 11 connects the downstream of the pressure reducing orifice plate 6 and the cylinder exhaust, and the wet steam enters the cylinder exhaust to heat the cylinder exhaust. With the start of the system, the steam parameters gradually rise. When the steam monitored by the pressure sensor two 8 and the temperature sensor two 7 reaches dry steam, the warm-up valve 11 connects the downstream of the pressure reducing orifice plate 6 and the cylinder inlet, and the steam turbine starts to rotate, and the steam turbine uses the low-pressure and high-temperature dry steam for warm-up.

[0045] With further rise of the steam parameters, the steam detected by the pressure sensor one 2 and the temperature sensor one 1 changes from wet steam to dry steam. At this time, the warm-up valve 11 valve rod runs to the middle position, and the drain line is closed. The drain distribution valve 3 connects the steam inlet and the main steam valve 10, and the steam turbine has the condition of starting. The unit is started, and the main steam valve 10 is opened. Since the steam turbine has been sufficiently preheated, the start-up time can be greatly shortened.

[0046] After the unit is normally operated, the isolation valves one and two 4, 12 are closed to ensure that there is no steam leakage in the drain line.

[0047] The drain distribution valve, the warm-up valve, the dehumidifying device, the isolation valve, the pressure reducing orifice plate, and the trap are all conventional structures or mature devices. By connecting them with pipelines and controlling the drain distribution valve and the warm-up valve through the readings of the pressure sensors and the temperature sensors, the drain system can be realized.

Claims

1. A marine steam turbine drain system, characterized in that: include: Main steam pipeline, warm-up branch, The main steam pipeline includes a temperature sensor, a pressure sensor, a drain distribution valve, a block valve, and a main steam valve. The main steam is divided into two paths by the drain distribution valve: one path is connected to the steam turbine through the block valve, the pressure reducing orifice plate, and the warm-up valve; the other path is connected to the main steam valve. The drain distribution valve is a three-way valve that can switch the connection between the main steam pipeline and the block valve or the main steam valve. The warm-up valve is a three-state valve that connects the downstream of the pressure reducing orifice plate to the exhaust cylinder, the flow structure, or the closed pipeline. The warm-up branch includes a dehumidification device, a pressure reducing orifice, a warm-up valve, and a steam trap; the dehumidification device is connected in series to the pipeline between the isolation valve and the pressure reducing orifice, and is connected to the steam turbine through the steam trap; the pressure reducing orifice is connected to the steam turbine through the warm-up valve; the dehumidification device has a built-in multi-layer corrugated dehumidification grid, the inlet is connected to the isolation valve, and the outlet is divided into two routes: one route passes through the steam trap to the discharge cylinder, and the other route passes through the pressure reducing orifice to the warm-up valve.

2. The marine steam turbine drain system according to claim 1, characterized in that: The aperture of the pressure reducing orifice is designed according to the rated parameters of the steam turbine so that the steam dryness is increased to a supercritical state after the steam pressure is reduced.

3. The marine steam turbine drain system according to claim 1, characterized in that: The valve stem position of the warm-up valve is controlled by feedback signals from a downstream temperature sensor and a pressure sensor.

4. The marine steam turbine drain system according to claim 1, characterized in that: A ground sealing surface is used between the valve stem and the housing of the steam trap distribution valve to ensure no steam leakage.

5. The marine steam turbine drain system according to claim 1, characterized in that: During the cold start phase of the steam turbine, the steam trap distribution valve directs the steam to the warm-up branch, while the warm-up valve switches the reduced-pressure steam to the cylinder discharge or flow structure to achieve staged preheating.

6. A control method for a marine steam turbine drain system according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Detect the temperature and pressure of the main steam pipeline; (2) When the steam is wet steam, open the drain distribution valve to the warm-up branch and adjust the steam parameters through the dehumidification device and the pressure reducing orifice plate; (3) When the steam reaches the dry steam condition after decompression, switch the warm-up valve to the flow structure for pre-warming.

7. The method according to claim 6, characterized in that After the turbine reaches the preheating threshold, close the warm-up branch and switch the drain distribution valve to the main steam valve to achieve rapid startup.

8. The method according to claim 6, characterized in that After the system is operating normally, close the two isolation valves to block the leakage of the drain branch.

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