Keywords

1 Introduction

The valve plays an important role as the throat of the ship lock’s water delivery system. Moreover, the operating condition of the valve is directly related with the safety and the efficiency of the ship lock. At present, The development of the ship lock projects in China leads to the construction of several high head locks, such as the Shuikou three-step ship lock, the Wuqiangxi three-step ship lock, the three-gorge five-step ship lock, Wan’an second-line lock, Changzhou lock and Banghai lock (Hu 2009; Bian 2000; Xue 2021).

The valve lintel gap is inevitable between the valve panel and the corridor in the navigation lock filling and the discharging valve’s valve lintel. This gap is narrow, and the hydraulic head acting upon it is the actual working head of the lock valve (Luo et al. 2016). When a high-speed water flow pass through the lintel gap, the pressure in the gap reduces considerably according to the Bernoulli’s law, and a strong cavitation will then occur subsequently not only to erode the flow passage but also to increase the pulsation of the valve opening and closing forces. The valve cavitation was widely studied (Ceccio 2010), which has several types, including the top gap cavitation, the bottom edge cavitation, the step-down floor cavitation, and the valve slot cavitation.

A new cavitation resistance technology for high head valves is developed to address the urgent need problem of the high head valve cavitation (Wu et al. 2013; Simpson et al. 2019). This technology involves a combined measure, including a new valve culvert shape model, a reasonable initial submergence depth, and the natural aeration (Li et al. 2019). The cavitation problem of the high head valves is properly resolved. The natural aeration measure can suppress the top gap cavitation with a good inhibitory effect on the bottom edge cavitation (Lindau et al. 2005). Moreover, this measure enables the aerated flow to reach the bottom edge of the valve (Paik et al. 2008; Rhee et al 2010). Consequently, the natural aeration has become a necessary measure for the protection against cavitation of high head valves. (Aydin and Ozturk 2009; Bhosekar et al. 2012; Zhang et al. 2011). Compared with forced aeration, self-aeration does not require an additional air compressor or control system and is more suitable for engineering applications. As a kind of self-aerated equipment, the self-aerated technology of valve lintel (SATVL) has the advantage of no moving parts, self-aeration, reliable operation, high efficiency of aeration, and corrosion reduction. Yan and Thorpe (Yan et al. 1990) pioneered the investigation of the cavitation flows, particularly, those of the choked cavitation flows and the choked cavitation conditions, and the choked cavitation number was proposed to describe the choked cavitation flows. He pointed out that the CVs could provide a constant mass flow rate of liquid while operating under the choked cavitation conditions, and the choked flow regime could be used to control the mass flow rate.

The key point of SATVL should focus on whether the valve lintel can be aerated or not. 1:1 full-scale slice physical model and CFD numerical simulations were established to investigate the sensitivity of structural parameters of the valve lintel to the critical self-aerated conditions, to optimize the valve lintel structural parameters to achieve the optimal self-aerated performance (Wang et al. 2017; Wang et al. 2020; Wu et al. 2020; Wu et al. 2021).

The dimension of Qianwei lock is 200 m × 34 m × 4.5 m (effective length & effective width & threshold depth), and the valve is classified as medium and high head lock with maximum working head 19.0 m. In order to reduce the amount of work and facilitate the construction, the hydraulic model of the valve in the design period recommended that the simple type of “flat bottom & expansion at the top gradually” would be adopted in the corridor of the valve. Natural aeration of the lintel is a necessary measure to suppress the cavitation of the gap and bottom edge of the lintel. The model test showed that lintel aeration can restrained cavitation of valve segment, but its effect needs to be verified by prototype results.

2 Physical Model

2.1 Model Arrangement

Figure 1 shows the shape of the corridor behind the door and the arrangement of aeration pipes used in the hydraulic physical model test of Qianwei ship lock. Two aeration pipes(φ = 100 mm) are set in the distance of 10.0 m and 16.0 m behind the door, and the control valve is set at the top of the reversed radical valve, the purpose is to eliminate the air in the corridor when water is filled for the first time and remove the air bag formed on the top of the corridor during the process of filling and discharging in the lock easily. Forced aeration is necessary depending on the prototype debugging as a backup measure to suppress cavitation of the corridor in the end.

Fig. 1.
figure 1

Shape of corridor and layout of aeration pipe

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2.2 Measuring Points Arrangement

The hydrophone layout in the physical model is shown in Fig. 2. The 1# hydrophone mainly receives the signal of lintel cavitation and strong cavitation noise at the bottom edge, The bottom edge cavitation noise signal is mainly received by the 2# and 3# hydrophone, The 4 # hydrophone receives cavitation noise signals transmitted to the lower access door slot and downstream access door slot itself when strong cavitation occurs at the bottom edge. The cavitation characteristics of the corridor of the valve section were studied by closing the natural aeration pipe of the lintel in a pressure reducing compartment.

Fig. 2.
figure 2

Hydrophone arrangement among the valve

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2.3 Model Test Results

Bottom edge cavitation and lintel cavitation is existed in the corridor shape of valve section in the absence of natural aeration measures for lintel, Cavitation morphology in typical opening of the value is shown in Fig. 3. The bottom edge cavitation occurs in the vortex at the tip of the bottom edge. Due to the strong turbulent shear action on the interface between the main flow behind the door and the rolling zone, the bottom edge cavitation is strengthened and developed in the shear layer, and its type is vortex cavitation.

The cavitation collapse zone is generally limited to 20.0 m behind the valve well., and the bottom edge cavitation collapse zone does not reach the lower access well even if the cavitation is particularly intense. The opening range of bottom edge cavitation is n = 0.2–0.8. The opening range of n = 0.4–0.7 is relatively strong, and the noise intensity is also large. The opening of n = 0.9 has no cavitation at the bottom edge.

Figure 4 shows the lintel shape and aeration pipe layout of Qianwei lock. The test shows that the noise intensity pulse is large and intensive when the door lintel is aerated, the noise intensity decreased significantly after aeration, and the measured noise intensity process line has a small amount of pulse. The pulse signal of 2# hydrophone is basically disappeared when the lintel single width aeration volume is only 0.018 m3/s/m and the lintel total aeration volume is 0.072 m3/s. The pulse signal of the 2# hydrophone is completely disappeared when the single width air flow rate of the lintel is only 0.044 m3/s/m and the total air flow rate of the lintel was 0.176 m3/s, The results showed that strong bottom margin cavitation (including lintel cavitation) is suppressed to a large extent after lintel ventilation, and lintel ventilation effect is remarkable.

Fig. 3.
figure 3

Bottom edge cavitation morphology when opening of valve is 0.6 (n = 0.6)

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Fig. 4.
figure 4

Lintel shape of Qianwei Lock (unit: mm)

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3 Prototype Observation

3.1 Effect of Natural Aeration of Lintel Inhibits Cavitation in the Section of Bilateral Filler and Drainage Valve

3.1.1 Section of Filler Valve

Water level during debugging is when the upstream water level is 334.4 m, and the initial water level of lock chamber is 318.2 m, working head of lock reach 16.2 m. Operation mode: the filler valve is fully opened at the rate of TV = 4 min, the valve is dynamic closed to 0.3° when the remaining water head is 0.6 m, When the water level inside and outside of the gate chamber is equal, Miter gate of the head bay is opened immediately.

If the aeration pipes of the valve lintel on both sides are blocked and the lintel is not aerated, the cavitation noise intensity in the upper left valve well and the upper right valve well is shown in Fig. 5, Early observation results show that hydrophone arranged in the position of valve well detected a relatively large pulse signal at the time when valve opening is in the early stages.

There are two reasons: seal head cavitation and the valve opening and closing system overcome the impact of the Static load changes to dynamic load at the beginning of the top valve seal separated from lintel, this kind of phenomenon is common in other high head lock, also is inevitable. The background elevation of cavitation noise signal of the left valve (n = 0.05–0.2) increases gradually, but the pulse is less, indicating that the bottom edge cavitation is not obvious before the opening is 0.2, when n = 0.2–0.8, the cavitation noise pulse is obvious and the intensity is high. After n = 0.8, the intensity decreases, only individual pulses when n = 0.9. The range of opening and the characteristics of the bottom edge cavitation in the prototype are similar to those in the model. The cavitation noise trend of the right valve is basically the same as that of the left valve, but the numerical value is slightly different. There is a significant cavitation pulse signal throughout the valve operation, the maximum is about 200 Pa. The “crackling sound” of cavitation collapse with two or three imperceptible low “muffled thunder sound” can be obviously felt at the top of the valve, which indicates strong cavitation is occurred in the water-filled valve section.

Fig. 5.
figure 5

Cavitation noise intensity in valve wells on both sides of bilateral water filler lock

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The natural aeration of the lintel is realized by removing the plug of the pipe, The aeration flow is shown in Fig. 6. The lintel is well aerated with the maximum wind speed of the aeration pipe about 27.9 m/s and the maximum aeration flow of 0.169 m3/s approximately, which is slightly larger than the aeration flow calculated by the physical model of the valve. The intensity of cavitation noise in the upper left valve well and the upper right valve well is shown in Fig. 7. There is a relatively obvious cavitation pulse signal when the valve is just opened, the maximum is about 93.1 Pa., It is caused by the seal head cavitation and the valve opening and closing system overcome the impact of the Static load changes to dynamic load at the beginning of the top valve seal separated from lintel as mentioned above. Subsequently, no cavitation pulse signal was detected in the valve wells on both sides during the valve operation process, and the process line was “stable”. The average noise signal during valve opening was 7 Pa, and the maximum noise signal was no more than 15 Pa, Cavitation of the water-filled valve section was fully inhibited after the lintel is aerated, and no sound of cavitation collapse was appeared on the top of the valve section during the whole valve opening process.

Fig. 6.
figure 6

Aeration flow of lintel of bilateral water filling valve of ship lock (natural aeration)

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Fig. 7.
figure 7

Cavitation noise intensity with bilateral water filling process (natural aeration)

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3.1.2 Drain Valve

Cavitation noise intensity contrast in the location of drain valve well is shown in Fig. 8 when lintel aeration or not, hydrophone arranged in the position of valve well detected a relatively large pulse signal at the time when valve opening is in the early stages (The reason is the same as above).

Fig. 8.
figure 8

Cavitation noise intensity on the left side

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Fig. 9.
figure 9

Cavitation noise intensity (natural aeration)

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During the entire valve operation process, the cavitation pulse signal is evident and obvious, cavitation noise signal background raised gradually increases on the left side of the valve when n = 0.05–0.2, n = 0.2–0.3 remain stable, n = 0.3–0.75 have an increasing trend and signal density, n = 0.7–0.8 signal gradually decreased, n = 0.9 only received individual signal pulse, the maximum noise intensity is about 142.0 Pa. The “crackling sound” of cavitation collapse can be obviously felt at the top of the valve, and 2–3 low “muffled sound” can be detected occasionally, and there is strong cavitation in the drainage valve section. The right side is basically similar to the left.

By removing the plug of the natural aeration pipe of the door lintel, the valve door lintel is aerated naturally with a maximum flow of 0.150 m3/s. The cavitation noise intensity of the lower left valve well is shown in Fig. 9. When the valve is just opened, there is an obvious cavitation pulse signal, about 64.1 Pa at most (The reason is the same as above). During the operation of the valve, no cavitation pulse signal was detected in the valve wells on both sides, and the process line was “stable”. No abnormal cavitation sound was detected at the valve top section, and the cavitation of the drainage valve section was fully restrained after the lintel aeration.

3.2 Cavitation Characteristics of One Side Valve

3.2.1 Water Filling Valve Section

When water is filled on one side, the aeration flow of the valve lintel is shown in Fig. 10, and the maximum is 0.199 m3/s. The intensity of cavitation noise in the upper left valve well and the upper right valve well is shown in Fig. 11. The observation results show that when the valve is just opened, there is a relatively obvious cavitation pulse signal, about 125.2 Pa at most. In the process of valve operation, before n = 0.5 opening, there is basically no pulse signal detected in the valve well. Between n = 0.5 and 0.7, there is weak cavitation noise signal, and the whole process line is relatively “stable”. During the valve opening process, no abnormal cavitation sound was detected on the top of the valve section. After natural aeration of the lintel, the original strong cavitation in the unilateral water filled valve section was fully restrained.

Fig. 10.
figure 10

Lintel aeration flow with unilateral water filling valve of ship lock

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Fig. 11.
figure 11

Cavitation noise intensity in valve wells on both sides of unilateral water-filled lock

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3.2.2 Drain Valve Section

In the case of unilateral drainage, the aeration flow of the lintel is shown in Fig. 12, and the maximum is 0.160 m3/s. The intensity of cavitation noise in the lower left valve well is shown in Fig. 13. The observation results show that, except for the head cavitation of seal at the beginning of opening, no cavitation pulse signal is detected in the valve well during the operation of the valve, and its process line is “stable”. During the whole valve opening process, no abnormal cavitation sound was detected at the top of the valve section. After the natural aeration of the lintel, the original strong cavitation in the unilateral drainage valve section was fully restrained.

Fig. 12.
figure 12

Lintel aeration flow with unilateral discharge

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Fig. 13.
figure 13

Cavitation noise intensity on the left side (unilateral discharge)

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3.3 Effect of Natural Aeration of Lintel on Inhibiting Valve Hanger Rod Vibration

Figure 14 shows the longitudinal vibration acceleration of the suspender of the right water-filled valve when the lintel is aerated or not. The longitudinal vibration acceleration of the suspender decreases after the lintel is aerated. After natural aeration of the lintel, the original strong cavitation in the water-filled valve section was fully suppressed and the vibration of the valve hanger rod was improved.

Fig. 14.
figure 14

Vertical vibration of the hanger rod of the right water-filled valve on lintel aeration or not

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4 Conclusions

  1. (1)

    Based on the hydro-dynamic model test of the valve, it is recommended that Qianwei lock with the water head of 19.0 m adopt the simple corridor shape of “flat bottom + gradual expansion at the top” with “small amount of work and simple construction”, and give the natural aeration facilities and aeration pipe arrangement of lintel adapted to its cavitation characteristics.

  2. (2)

    The model test showed that strong bottom margin cavitation (including lintel cavitation) was suppressed to a large extent after lintel aeration. Lintel aeration effect is remarkable. In ventilation, the noise intensity pulse is large and dense, After aeration, the noise intensity decreased significantly, and the measured noise intensity process line had a small amount of pulse. When the lintel single width aeration flow was only 0.018 m3/s/m and the lintel total aeration flow was 0.072 m3/s, the pulse signal of 2# hydrophone basically disappeared. When the single width air flow rate of the lintel was only 0.044 m3/s/m and the total aeration flow rate of the lintel was 0.176 m3/s, the pulse signal of the 2# hydrophone completely disappeared.

  3. (3)

    Prototype observation shows that the effect of natural ventilation of lintel is significant, and cavitation of valve segment is fully inhibited after natural aeration of lintel. The natural aeration pipe of the door lintels was intentionally blocked when the two sides were filled with water. During the whole operation of the valve, there was a relatively obvious cavitation pulse signal, the maximum was about 182.3Pa. The “crackling sound” of cavitation collapse can be obviously felt at the top of the valve, and there is 2–3 imperceptible low “muffled thunder sound” occasionally, and the valve section has strong cavitation. After the natural aeration of the valve lintel, no cavitation pulse signal was detected in the valve wells on both sides during the operation of the valve, and its process line was “stable”. During the whole valve opening process, no sound of cavitation collapse was detected on the top of the valve section. The effect of natural aeration of lintel on inhibiting cavitation of valve segment is also significant.

  4. (4)

    The comparison of suspender vibration of lintel ventilation or not shows that the vibration of valve suspender is improved after the natural aeration of lintel, because the original strong cavitation in the water-filled valve section is fully suppressed.