A propulsion system and method utilizing energy from ship desulfurization wastewater

Abstract

The present invention discloses a propulsion system and method for utilizing the energy of ship desulfurization wastewater, the system comprising a desulfurization system, a wastewater propulsion system, and a wastewater propulsion pipeline regulating system. Since the height of the desulfurization tower from the sea level is relatively high, the flow rate of seawater used for desulfurization in the open desulfurization system is large, so in order to utilize the mechanical energy contained in the wastewater used to wash the exhaust gas in the desulfurization tower, the present invention designs a wastewater propulsion system to utilize this mechanical energy, provide partial propulsion for the navigation of the ship, and reduce the fuel consumption of the ship. The wastewater propulsion pipeline regulating system described in the present invention ensures that the wastewater can be sprayed out horizontally from the wastewater nozzle during the navigation of the ship, maximizes the utilization of the mechanical energy contained in the wastewater, and improves the energy conversion rate. In order to avoid the discontinuity of the wastewater sprayed from the wastewater nozzle, the present invention provides a method for calculating the inner diameter of the wastewater nozzle.

Description

Technical Field

[0001] The present invention belongs to the technical field of ships, and in particular relates to a propulsion system and method utilizing the energy of ship desulfurization wastewater. Background Art

[0002] As the international community pays more and more attention to the environment, people are accelerating the pace of energy conservation and emission reduction, and countries around the world have taken measures to advocate "green" development. In the shipping industry, the International Maritime Organization (IMO) has put forward higher requirements for ship emissions in order to achieve "green" ships, stipulating that from January 1, 2020, the sulfur content in exhaust gas emitted by ships shall not exceed 0.5%. But nowadays, more than 90% of ships use diesel engines as the main power device, and use cheap and high-sulfur heavy oil as the main fuel oil. Although burning heavy oil has achieved the purpose of reducing costs, it will produce a large amount of sulfur-containing exhaust gas, which has a great impact on the environment. Therefore, in the face of such a strict sulfur limit order, shipowners have taken measures to reduce sulfur oxides in exhaust gas.

[0003] Among them, the most widely used desulfurization method on ships is to install a desulfurization tower exhaust gas cleaning system (EGCS) on the ship. EGCS includes open desulfurization system, closed desulfurization system and hybrid desulfurization system. The open desulfurization system directly pumps seawater from the ocean into the desulfurization tower and sprays it in the desulfurization tower to react with the flue gas flowing through the desulfurization tower. The desulfurized flue gas is directly discharged into the atmosphere, and the seawater solution that neutralizes the sulfide becomes wastewater and is discharged downward to the sea. Due to the fact that there is no need to add chemical agents, the system is simple and easy to manage, the open desulfurization system has become the most popular desulfurization method at this stage. Currently, 80% of ships use open desulfurization systems for desulfurization.

[0004] At the same time, the installation position of the ship's desulfurization tower on the ship is relatively high. The height of the desulfurization tower on a large bulk carrier is generally up to 20m from the sea level. In addition, the ship's main engine has a large power and produces a lot of exhaust gas due to fuel oil, so the flow rate of seawater supplied to the desulfurization tower for washing the exhaust gas is large, usually about 1000m 3 / h. For container ships with higher freeboard height, the height of the desulfurization tower above the sea level is as high as 30m. The main engine power of large container ships is larger, and the flow rate of seawater supplied to the desulfurization tower for washing exhaust gas can exceed 2000m 3 / h. When the ship is sailing in the ocean, the open desulfurization system is always in operation, so the seawater used to wash the exhaust gas in the desulfurization tower contains a large amount of mechanical energy. Usually, the wastewater after washing the exhaust gas in the open desulfurization system is often discharged directly into the sea from the side, and the mechanical energy contained in it has not been reasonably and effectively utilized, resulting in energy waste. Therefore, if the large amount of mechanical energy contained in the desulfurization wastewater with a high height and a large flow in the desulfurization tower can be utilized for the water jet propulsion of the ship, it can provide partial propulsion for the navigation of the ship and realize the navigation aid of the ship, which will reduce the fuel consumption of the ship and improve the economy of the ship. In addition, since the open desulfurization system has become the mainstream desulfurization system, the above method has a very broad application prospect and greater practical significance. Summary of the invention

[0005] In response to the above-mentioned problems, the present invention proposes a propulsion system and method for utilizing the energy of ship desulfurization wastewater, which utilizes the large amount of mechanical energy contained in the ship desulfurization wastewater to assist the navigation of the ship, thereby reducing the energy consumption of the ship and improving the economy of the ship.

[0006] The first object of the present invention is to provide a propulsion system that utilizes the energy of ship desulfurization wastewater, the system comprising: a desulfurization system, a wastewater propulsion system, and a wastewater propulsion pipeline regulation system.

[0007] The desulfurization system comprises: a valve box, a seawater pump, a desulfurization tower inlet, a desulfurization tower, a wastewater collection port, and a wastewater pipeline.

[0008] The wastewater propulsion system comprises: a hose inlet, a hose, a wastewater spray pipe, a wastewater spray pipe inlet, and a wastewater spray port.

[0009] The wastewater propulsion pipeline regulating system comprises: a sphere, a fixing ring, a rotating screw, a screw fixing seat, a fixing pin, a rotating wheel, and a sphere end cover.

[0010] In the desulfurization system, the wastewater collection port is located at the bottom of the ship's desulfurization tower.

[0011] The hose is connected to the wastewater pipe and the wastewater spray pipe respectively, and both the wastewater pipe and the wastewater spray pipe are rigid pipes.

[0012] The wastewater nozzle is a sphere near the wastewater nozzle, the fixing ring is sleeved on the wastewater nozzle, and the hull is provided with a spherical groove, which can just match the sphere, but the sphere and the hull are not rigidly connected. The sphere end cover is used to fix the sphere on the hull.

[0013] A through hole having the same inner diameter as the wastewater nozzle is provided in the middle of the sphere, and wastewater sprayed from the wastewater nozzle can be discharged outside the ship through the sphere and the wastewater nozzle.

[0014] The screw fixing seat is rigidly fixed on the ship, and the rotating screw rod and the screw fixing seat are in spiral fit.

[0015] The second object of the present invention is to propose a propulsion method utilizing the energy of ship desulfurization wastewater based on the above-mentioned system.

[0016] In this method, the rotating wheel is rigidly connected to the upper end of the rotating screw, and the rotation of the rotating wheel can control the rotating screw to move upward or downward relative to the screw fixing seat. The lower end of the rotating screw cooperates with the fixing ring through a fixing pin. When the rotating wheel rotates clockwise or counterclockwise, the wastewater spray pipe can be pushed or pulled to move downward or upward around the hose, thereby adjusting the direction of the wastewater spray outlet.

[0017] Furthermore, the wastewater nozzle is the outlet end of the wastewater nozzle, which is located above the propeller tail shaft. The axis of the wastewater nozzle is a straight line, and the straight line passes through the centerline of the ship. Regardless of whether the ship is fully loaded or unloaded, the wastewater nozzle is always below the water surface.

[0018] Furthermore, in order to maximize the use of mechanical energy in the ship's desulfurization wastewater, the position of the wastewater nozzle needs to be adjusted before sailing to ensure that the direction of the wastewater sprayed from the wastewater nozzle is horizontal when the ship is sailing.

[0019] When the ship is sailing, the seawater is pumped by the seawater pump and sent to the desulfurization tower through the valve box and the seawater pump. The seawater is sprayed at the entrance of the desulfurization tower, and under the action of gravity, the seawater moves from top to bottom. At this time, the exhaust gas discharged by the ship's diesel engine enters the desulfurization tower from bottom to top, reacts with the seawater from top to bottom, and the washed exhaust gas continues to be discharged upward into the atmosphere. The seawater after washing the exhaust gas becomes wastewater and first flows into the wastewater collection port of the desulfurization tower, and then enters the hose from the hose inlet along the wastewater pipeline, and then enters the wastewater nozzle through the wastewater nozzle inlet. Finally, the wastewater is discharged into the sea through the sphere and the wastewater nozzle. Since the desulfurization tower is at a high height from the horizontal plane, part of the potential energy in the wastewater is converted into kinetic energy under the action of gravity, and the wastewater has a higher speed at the wastewater nozzle. The wastewater sprayed behind the ship can generate forward thrust for the ship, which can provide part of the propulsion for the ship's navigation and reduce the ship's fuel consumption.

[0020] Furthermore, when the ship is sailing without load, the height difference △h between the wastewater collection port of the desulfurization tower and the sea level is larger than when it is fully loaded. In this case, according to the flow continuity equation of the fluid, the wastewater is more likely to be interrupted in the wastewater nozzle, resulting in discontinuity of wastewater sprayed from the wastewater nozzle, causing the wastewater propulsion efficiency to decrease. In order to avoid this phenomenon, it is necessary to ensure that the inner diameter D of the wastewater nozzle is less than the critical value D c .

[0021] According to the law of conservation of energy:

[0022]

[0023] get:

[0024]

[0025] Where:

[0026] m——fluid mass, kg;

[0027] g——acceleration due to gravity, m / s 2 ;

[0028] △h——the height difference between the wastewater collection port and the sea level when the ship is unloaded, m;

[0029] η——hydraulic efficiency of fluid;

[0030] v——water flow velocity at the wastewater outlet, m / s;

[0031] According to the flow calculation formula:

[0032]

[0033] Where:

[0034] Q——wastewater flow at wastewater outlet, m 3 / s;

[0035] A——Cross-sectional area at wastewater outlet, m 2 ;

[0036] D c ——critical inner diameter of wastewater nozzle, m;

[0037] Substituting formula (10) into formula (11), we get:

[0038]

[0039] At this time, the inner diameter D of the wastewater nozzle:

[0040]

[0041] Where:

[0042] D is the inner diameter of the wastewater nozzle, m.

[0043] Beneficial effects of the present invention:

[0044] 1. The present invention can utilize the mechanical energy contained in the wastewater of ship desulfurization during the navigation process of the ship, convert a large amount of potential energy in the wastewater into part of the propulsion force of the ship, reduce the fuel consumption of the ship, achieve energy conservation and emission reduction of the ship, and improve the economy of the ship.

[0045] 2. The wastewater propulsion pipeline regulation system described in the present invention ensures that wastewater can be sprayed out horizontally at the wastewater nozzle during the navigation of the ship, thereby maximizing the use of the potential energy contained in the wastewater and improving the energy conversion rate.

[0046] 3. In the present invention, wastewater is discharged near the stern. Due to the presence of the stern propeller, the wastewater can be mixed with the surrounding seawater more quickly and fully, reducing the pollution of the seawater near the wastewater discharge caused by the slow diffusion rate.

[0047] 4. The method of the present invention is simple, easy to implement, and the device is easy to maintain. In addition, since the open desulfurization system has a high market share, the present invention has broad application prospects and great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the principle diagram of the desulfurization system in the present invention;

[0049] Figure 2 is a simplified side view of the system of the present invention;

[0050] Figure 3 It is an axonometric view of the wastewater propulsion pipeline regulation system;

[0051] Figure 4 It is an axonometric view of the wastewater propulsion pipeline regulation system from another perspective;

[0052] Figure 5 This is a schematic diagram of the connection near the hose;

[0053] Figure 6 This is an exploded view of the connection between the wastewater nozzle and the hull;

[0054] Figure 7 It is an axonometric view of the wastewater propulsion pipeline regulation system after the adjustment position;

[0055] Figure 8 It is an axonometric diagram of the wastewater propulsion pipeline regulation system from another perspective after the position is adjusted;

[0056] Fig. 9 This is a schematic diagram of the connection near the hose after adjusting the position;

[0057] In the attached figure: 1. valve box; 2. seawater pump; 3. desulfurization tower inlet; 4. desulfurization tower; 5. wastewater collection port; 6. wastewater pipe; 6a. hose inlet; 7. hose; 8. wastewater nozzle; 8a. wastewater nozzle inlet; 8b. sphere; 8c. fixing ring; 8d. rotating screw; 8e. screw fixing seat; 8f. fixing pin; 8g. rotor; 8h. wastewater nozzle; 8i. sphere end cover. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0059] A propulsion system utilizing the energy of ship desulfurization wastewater comprises: a valve box (1), a seawater pump (2), a desulfurization tower inlet (3), a desulfurization tower (4), a wastewater collection port (5), a wastewater pipeline (6), a hose inlet (6a), a hose (7), a wastewater nozzle (8), a wastewater nozzle inlet (8a), a sphere (8b), a fixing ring (8c), a rotating screw (8d), a screw fixing seat (8e), a fixing pin (8f), a rotating wheel (8g), a wastewater nozzle (8h), and a sphere end cover (8i). The system can be divided into a desulfurization system, a wastewater propulsion system, and a wastewater propulsion pipeline regulation system.

[0060] Among them, Figure 1 The desulfurization system comprises: a valve box (1), a seawater pump (2), a desulfurization tower inlet (3), a desulfurization tower (4), a wastewater collection port (5), and a wastewater pipeline (6).

[0061] The wastewater propulsion system comprises: a hose inlet (6a), a hose (7), a wastewater nozzle (8), a wastewater nozzle inlet (8a) and a wastewater nozzle (8h), such as Figure 2 , Figure 3 , Figure 4 and Figure 5 shown.

[0062] The wastewater propulsion pipeline regulating system comprises: a sphere (8b), a fixing ring (8c), a rotating screw (8d), a screw fixing seat (8e), a fixing pin (8f), a rotating wheel (8g), and a sphere end cover (8i). Figure 3 and Figure 4 .

[0063] In the desulfurization system, the wastewater collection port (5) is located at the bottom of the ship desulfurization tower (4).

[0064] The hose (7) is connected to the wastewater pipe (6) and the wastewater spray pipe (8) respectively. Figure 5 As shown, the wastewater pipe (6) and the wastewater nozzle (8) are both rigid pipes.

[0065] like Figure 6 The wastewater nozzle (8) is a sphere near the wastewater nozzle (8h), the fixing ring (8c) is sleeved on the wastewater nozzle (8), a spherical groove is provided on the hull, which can just match the sphere (8b), but the sphere (8b) and the hull are not rigidly connected, the sphere end cover (8i) is used to fix the sphere (8b) on the hull, and the sphere end cover (8i) also has an approximately hemispherical groove inside, which matches the sphere (8b).

[0066] The sphere (8b) has a through hole in the middle with the same inner diameter as the wastewater nozzle (8), and the wastewater sprayed from the wastewater nozzle (8) can be discharged outside the ship through the sphere (8b) and the wastewater nozzle (8h). The function of the sphere (8b) is to ensure the sealing near the wastewater nozzle (8h) to prevent seawater from entering the ship from the connection when the position of the wastewater nozzle (8) is adjusted.

[0067] The screw rod fixing seat (8e) is rigidly fixed on the ship, and the rotating screw rod (8d) and the screw rod fixing seat (8e) are in spiral fit.

[0068] The rotating wheel (8g) is rigidly connected to the upper end of the rotating screw (8d), and the rotation of the rotating wheel (8g) can control the rotating screw (8d) to move upward or downward relative to the screw fixing seat (8e). The lower end of the rotating screw (8d) is matched with the fixing ring (8c) through the fixing pin (8f). When the rotating wheel (8g) rotates clockwise or counterclockwise, it can push or pull the wastewater spray pipe (8) to move downward or upward around the hose (7), thereby adjusting the direction of the wastewater spray port (8h).

[0069] The wastewater nozzle (8h) is the water outlet end of the wastewater nozzle (8), which is located above the propeller tail shaft, and no matter how the direction of the wastewater nozzle (8h) is adjusted, the axis of the wastewater nozzle (8) is a straight line, and the straight line passes through the centerline of the ship.

[0070] In order to maximize the use of mechanical energy in the ship's desulfurization wastewater, the position of the wastewater nozzle (8) is usually adjusted before sailing to ensure that the wastewater sprayed from the wastewater nozzle (8h) is in a horizontal direction when the ship is sailing. Usually, when the ship is sailing without load, there is a slight stern trim. Figure 7 and Figure 8 , the wheel (8g) can be rotated clockwise to push the wastewater nozzle (8) to move downward around the hose (7), thereby controlling the direction of the wastewater nozzle (8h) to maintain a certain angle θ with the base plane of the ship, such as Fig. 9 As shown, the wastewater ejected from the wastewater ejection port (8h) is ensured to remain horizontal. Regardless of whether the ship is fully loaded or unloaded, the wastewater ejection port (8h) is always below the water surface.

[0071] When the ship is sailing, the seawater is pumped by the seawater pump (2) and sent to the desulfurization tower (4) through the valve box (1) through the booster of the seawater pump (2). The seawater is sprayed at the desulfurization tower inlet (3). Under the action of gravity, the seawater moves from top to bottom. At this time, the exhaust gas discharged by the ship's diesel engine enters the desulfurization tower (4) from bottom to top, and reacts with the seawater from top to bottom. The seawater after washing the exhaust gas becomes wastewater and first flows into the wastewater collection port (5) of the desulfurization tower (4), then enters the hose (7) from the hose inlet (6a) along the wastewater pipe (6), and then enters the wastewater nozzle (8) through the wastewater nozzle inlet (8a). Finally, the desulfurized seawater is discharged into the sea through the sphere (8b) and the wastewater nozzle (8h). Since the height of the desulfurization tower (4) from the horizontal plane is relatively high, part of the potential energy in the wastewater is converted into kinetic energy under the action of gravity, and the wastewater has a relatively high speed at the wastewater nozzle (8h). The wastewater is sprayed behind the ship, which creates forward thrust for the ship, thereby providing partial propulsion for the ship's navigation and reducing the ship's fuel consumption.

[0072] When the ship is sailing without load, the height difference △h between the wastewater collection port (5) in the desulfurization tower (4) and the sea level is greater than when it is fully loaded. In this case, according to the flow continuity equation of the fluid, the wastewater is more likely to be interrupted in the wastewater nozzle (8), resulting in discontinuity of wastewater sprayed from the wastewater nozzle (8h), causing a decrease in wastewater propulsion efficiency. In order to avoid this phenomenon, it is necessary to ensure that the inner diameter D of the wastewater nozzle (8h) is less than the critical value D c .

[0073] According to the law of conservation of energy:

[0074]

[0075] get:

[0076]

[0077] Where:

[0078] m——fluid mass, kg;

[0079] g——acceleration due to gravity, m / s 2 ;

[0080] △h——the height difference between the wastewater collection port (5) and the sea level when the ship is unloaded, m;

[0081] η——hydraulic efficiency of fluid;

[0082] v——water velocity at the wastewater outlet (8h), m / s;

[0083] According to the flow calculation formula:

[0084]

[0085] Where:

[0086] Q——wastewater flow at the wastewater outlet (8h), m 3 / s;

[0087] A——Cross-sectional area at wastewater outlet (8h), m 2 ;

[0088] D c ——critical inner diameter of wastewater nozzle (8h), m;

[0089] Substituting formula (10) into formula (11), we get:

[0090]

[0091] At this time, the inner diameter D of the wastewater nozzle:

[0092]

[0093] Where:

[0094] D is the inner diameter of the wastewater nozzle (8h), m.

[0095] The above is only a preferred embodiment of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A propulsion system utilizing the energy of ship desulfurization wastewater, characterized in that: The system comprises a valve box (1), a seawater pump (2), a desulfurization tower inlet (3), a desulfurization tower (4), a wastewater collection port (5), a wastewater pipeline (6), a hose inlet (6a), a hose (7), a wastewater nozzle (8), a wastewater nozzle inlet (8a), a sphere (8b), a fixing ring (8c), a rotating screw (8d), a screw fixing seat (8e), a fixing pin (8f), a rotor (8g), a wastewater nozzle (8h), and a sphere end cover (8i), and is divided into a desulfurization system, a wastewater propulsion system, and a wastewater propulsion pipeline regulation system; The desulfurization system comprises: a valve box (1), a seawater pump (2), a desulfurization tower inlet (3), a desulfurization tower (4), a wastewater collection port (5), and a wastewater pipeline (6); The wastewater propulsion system comprises: a hose inlet (6a), a hose (7), a wastewater spray pipe (8), a wastewater spray pipe inlet (8a), and a wastewater spray port (8h); The wastewater propulsion pipeline regulating system comprises: a sphere (8b), a fixing ring (8c), a rotating screw (8d), a screw fixing seat (8e), a fixing pin (8f), a rotating wheel (8g), and a sphere end cover (8i); The wastewater collection port (5) is located at the bottom of the ship's desulfurization tower, and the hose (7) is respectively connected to the wastewater pipe (6) and the wastewater nozzle (8), and the wastewater pipe (6) and the wastewater nozzle (8) are both rigid pipes. The screw fixing seat (8e) is rigidly fixed on the ship, and the rotating screw (8d) and the screw fixing seat (8e) are in a spiral fit; The wastewater nozzle (8) is a sphere near the wastewater nozzle (8h); the fixing ring (8c) is sleeved on the wastewater nozzle (8); a spherical groove is provided on the hull, which can just match the sphere (8b); but the sphere (8b) and the hull are not rigidly connected; the sphere end cover (8i) is used to fix the sphere (8b) on the hull, and the sphere end cover (8i) also has a substantially hemispherical groove inside, which matches the sphere (8b); The sphere (8b) has a through hole in the middle with the same inner diameter as the wastewater nozzle (8). Wastewater sprayed from the wastewater nozzle (8) can be discharged outside the ship through the sphere (8b) and the wastewater nozzle (8h). The wastewater is sprayed toward the rear of the ship, so that the ship generates forward thrust.

2. A propulsion method using the energy of ship desulfurization wastewater, using the system described in claim 1, characterized in that: The screw fixing seat (8e) is rigidly fixed on the ship, the rotating screw (8d) is screwed onto the screw fixing seat (8e), the rotating wheel (8g) is rigidly connected to the upper end of the rotating screw (8d), the rotation of the rotating wheel (8g) can control the rotating screw (8d) to move upward or downward relative to the screw fixing seat (8e), the lower end of the rotating screw (8d) cooperates with the fixing ring (8c) via the fixing pin (8f), when the rotating wheel (8g) rotates clockwise or counterclockwise, it can push or pull the wastewater nozzle (8) to move downward or upward around the hose (7), thereby adjusting the direction of the wastewater nozzle (8h) to keep it horizontal before the ship sails, when the ship is sailing, the seawater is pumped by the seawater pump (2) through the valve box (1) and is pressurized by the seawater pump (2), and is sent into the desulfurization tower (4), and the seawater is discharged from the desulfurization tower (4) by the seawater pump (2). The desulfurization tower inlet (3) is sprayed, and under the action of gravity, seawater moves from top to bottom. At this time, the exhaust gas discharged from the ship's diesel engine enters the desulfurization tower (4) from bottom to top, and reacts with the seawater from top to bottom. The seawater after washing the exhaust gas becomes wastewater and first flows into the wastewater collection port (5) of the desulfurization tower (4), then enters the hose (7) from the hose inlet (6a) along the wastewater pipe (6), and then enters the wastewater nozzle (8) through the wastewater nozzle inlet (8a). Finally, the desulfurized seawater is discharged into the sea through the sphere (8b) and the wastewater nozzle (8h). Since the desulfurization tower (4) is at a high height from the horizontal plane, part of the potential energy in the wastewater is converted into kinetic energy under the action of gravity. The wastewater has a high speed at the wastewater nozzle (8h), and the wastewater is sprayed behind the ship, which can cause the ship to generate forward thrust.

3. A propulsion method using the energy of ship desulfurization wastewater according to claim 2, characterized in that: The wastewater nozzle (8h) is the water outlet end of the wastewater nozzle pipe (8) and is located above the propeller tail shaft. The axis of the wastewater nozzle pipe (8) is a straight line, and the straight line passes through the centerline plane of the ship. Regardless of whether the ship is fully loaded or unloaded, the wastewater nozzle (8h) is always below the water surface.

4. A propulsion method using the energy of ship desulfurization wastewater according to claim 2, characterized in that: Inner diameter of wastewater nozzle (8h) D It can be obtained from formula (13) （13） Determine, where: D is the inner diameter of the wastewater nozzle (8h), m; Q is the flow rate of wastewater in the wastewater nozzle (8) when the ship is sailing at a constant speed, unit: m³ / s; g is the acceleration due to gravity, m / s 2 ; △h is the height difference between the wastewater collection port (5) and the sea level when the ship is unloaded, m; η is the hydraulic efficiency of the fluid.

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