A crescent-shaped papermaking machine has been widely applied in recent years, due to its high efficiency and energy conservation. However, the pulp waste liquid can be sprayed towards the guard plate of the water absorption box at high speed after paper production. Huge mechanical impact and damage to the guard plate can also result in the waste of the kinetic energy carried by the pulp waste liquid. Therefore, this article aims to recover and utilize the residual pressure energy carried by the pulp waste liquid through a crossflow turbine. Numerical studies were also performed on two schemes of crossflow turbines at multiple rotational speeds（Scheme I featured a single deflector guiding flow to impact the left side of the runner (inducing counter-clockwise rotation), with an additional deflector near the forming roller to prevent water splash affecting study quality. Scheme II was utilized as a dual-deflector system to direct flow onto the right side of the runner (clockwise rotation), steering effluent away from the forming roller. A systematic investigation was made to explore the influence of the deflector form and the rotational speed of the runner on the internal flow and energy conversion of the double-impulse turbine. The results indicate that in Scheme I: The deflector exhibited the ‌weak constraint effect on the pulp waste liquid, while both the area between the deflector and forming roller and the first work phase zone of the runner generated the high turbulent kinetic energy‌, leading to the energy dissipation and significant hydraulic losses‌. There was a dispersion ‌ of the water flow along the circumferential direction, particularly with the comparable circulation consumption capacity in the two work phases. Multiple circulation abrupt peaks‌ occurred circumferentially, due to the uneven energy transfer‌. The scheme II with the double deflectors well guided the water flow to the runner, significantly reducing the high turbulent kinetic energy area, and the Hydraulic loss of the runner. The energy of the crossflow turbine was improved to relatively concentrate the working area of the runner, where about 85% of the circulation was transformed in the first impact working area from 330° to 30°. The second working area of the crossflow turbine gradually approached the first working area with the increase of the runner rotational speed. Especially in the case of high rotational speed, the water flow of the two working times was mixed and interfered with each other, leading to large hydraulic losses. The maximum efficiency of the crossflow turbines was reached under the different schemes with the increase of the rotational speed. In Scheme I, there was the highest efficiency of 39.2% at 250 r/min. In scheme II, the highest efficiency of 56.4% was found at 300r/min. As such, Scheme II's dual-deflector guided the flow to impact the runner's right side for the clockwise rotation. An optimal speed of 300 r/min was represented as a highly effective solution to recover the residual energy from the paper machine. Therefore, Scheme II demonstrated the superior hydraulic efficiency. The finding can also provide a strong reference to optimize the energy recovery turbine for papermaking machines.

Hydraulic stations often undertake the tasks of peak and frequency regulation of the power grid, due to the excellent performance and relatively low costs. Thus, operation conditions vary frequently in the turbine. These rapid changes in operating parameters within a short time can seriously affect the stable operation of the power station. In this study, the dynamic characteristics test of a prototype tubular turbine was implemented by the dynamic grid technology, in order to consider the gravity of free surface and water gravity during the transient process of load decrease and load increase under the same output range. The research results showed that: The flow distribution in the unit was different at the same output. The reason was that the different initial flow states were caused by the initial operating conditions in the transient process of load increase and decrease. In the process of load decrease, the center area of the draft tube inlet was affected by the water discharge cone. A low-velocity zone of the same diameter occurred as the water discharge cone. The area of this low-velocity zone was further expanded as the main flow flows downstream into the diffusion section of the draft tube. There were outstanding vortexes and refluxes at the outlet of the draft tube. The starting condition of the load increase process was a partial load condition with a low flow state. The flow state in the unit was more turbulent in the whole load increase process, compared with the load decrease process. The low-velocity areas in the tailpipe in the load increase process were outstandingly larger than those in the load decrease process for the same output. The vortex begins at the inlet area of the tailpipe and spreads into most of the entire tailpipe area. This vortex state in the draft tube posed a great impact on the stability of the turbine. The vortex area and intensity in the draft tube during the load decrease process were significantly smaller than those during the load increase process. Even there was no exception at the vortex scale in the draft tube. After that, the positive and negative back pressure difference between the load-increasing and load-decreasing process was outstandingly larger than that of the load-increasing process under the same output. The pressure of the blade head and suction surface in the load-decreasing process was much smaller than that of the negative pressure state in the load-increasing process, leading easy to cavitation. The water pressure pulsation in the turbine was mainly composed of 0.1f_n low-frequency pressure pulsation caused by the vortex rope of the draft tube, and 3f_n high-frequency pressure pulsation caused by the rotation of the runner. The amplitude of the pressure pulsation during the load increase process was much larger than that during the load reduction process. The main vibration area was concentrated on the runner of the tubular turbine for the combined action of the two pressure pulsations. Water pressure pulsation was transmitted to the runner area and then coupled with the cantilever beam structure of the runner, leading to the vibration of the runner, which in turn exacerbated the vibration of the water body. And the amplitude of pressure pulsation in the load-increasing process was much larger than that in the load-decreasing process, leading to the low stability of turbine operation in the load-increasing process. The findings can provide a strong reference to design and operate the tubular turbine, particularly for the multi-energy complementary system on the operation requirements.