Experimental investigation of liquid nitrogen cavitating flows in converging-diverging nozzle with special emphasis on thermal transition

Cavitation in thin liquid layer: A review.

Experimental study of the cavitation noise and vibration induced by the choked flow in a Venturi reactor

Experimental investigation on the cavitation performance in a venturi reactor with special emphasis on the choking flow

The cavitation intensity of a novel hydrodynamic cavitation reactor (HCR) was experimentally evaluated in terms of the amount of bubble generation and bubble collapse energy. The amount of bubble generation was analyzed by flow visualization using a high-speed camera. The bubble collapse energy was evaluated by calculating the generated thermal energy. Pressure and velocity were selected as parameters affecting cavitation intensity. Further, to evaluate the effect of pressure, cavitation intensity was evaluated according to the pressure upstream of the HCR. Because HCR is a rotating fluid machine, the velocity was divided into radial and tangential components. First, cavitation intensity was analyzed using the flow rate to evaluate the effect of the radial velocity. Then, cavitation intensity according to the rotational speed was analyzed to evaluate the effect of the tangential velocity. As a result, the cavitation intensity was inversely proportional to the pressure and directly proportional to the rotational speed. However, when the density of bubbles in the cavitation region exceeded a certain level, the bubble collapse energy did not increase owing to the decrease in the heat transfer rate required for bubble growth. Conversely, the flow rate has a slight effect on the amount of bubble generation; however, the cavitation region is expanded, and the heat transfer rate and the thermal energy are increased. Fundamental analysis of the factors affecting cavitation intensity in an HCR was conducted.

Experimental study of cavitation intensity using a novel hydrodynamic cavitation reactor

A comprehensive investigation on cavitating flow and cavitation-induced erosion was performed experimentally in an orifice plate system. Three image post-processed approaches were applied to analyze the test data, in order to obtain the cavitation characteristics. The cavitating flow pattern was studied by high speed images. In one cavitation developing period, there could be three distinct cavitation clouds, whereas the second one is not fully developed. The first image post-processing approach was applied to obtain the mean value and standard deviation distribution, which indicate the erosion area may cover almost all the cavitation developing route and the most vulnerable erosion area locates near the cavitation collapse site. It is coincides with the erosion tests analyzed through the pit-count algorithm approach. The cavitation circulation frequency was invested via PSD analysis approach. It shows that the frequency linearly decreasing with decreasing cavitation number. Additionally, the cavitation intensity effect on cavitation erosion was quantitatively studied based. It is found that the damages are strongly enhanced when increasing the flow velocity. Moreover, the growth rate of eroded pits number is actually stepwise instead of linear (similar to our previous work in a venturi tube), which supports the idea that the cloud cavitation collapse is the primary reason for erosion. The present approaches applied here shows good potential ability of investigating cavitating flows and can be utilized for other apparatus.

Image post-processed approaches for cavitating flow in orifice plate

Inducer designing method based on centrifugal pump

The invention discloses an optimal design method for an inducer with a varying pitch of a centrifugal pump, belonging to the technical field of pumps. The optimal design method is characterized by comprising the following steps: when designing the inducer with the varying pitch, firstly, determining data such as flow of a peak efficiency point of the central pump, a necessary net positive suction head, a device net positive suction head and the like through experiments, and then determining geometric sizes of diameters of an inlet and an outlet of a rim of the inducer and a rim folding lead according to the experimental data and a flow condition of the inlet of a main impeller of the pump. According to the optimal design method for the inducer with the varying pitch of the centrifugal pump provided by the invention, the inducer and the main impeller of the pump have good energy matching relationship, the performance of the inducer is improved, the operation stability of the system is enhanced, difficulty in selection of a lift coefficient of the inducer according to experience is avoided, and the efficiency for designing the inducer is improved. The optimal design method has a certain popularization value.

Optimal design method for inducer with varying pitch of centrifugal pump

In order to explore the influence of rotating speed on the internal flow and sealing characteristics of the liquid-sealing impeller for a liquid oxygen turbopump of a rocket engine, unsteady numerical simulations of the flow characteristics and sealing performance of the first-stage liquid-sealing impeller for a liquid oxygen turbopump under liquid phase conditions were performed. The results show that the pressurization value increases with the increase in the rotating speed. The first-stage liquid-sealing impeller, whose structure is symmetrically distributed along the center of the rotation axis, tends to be an isobaric seal at a rotating speed of 12,000 rpm, and when the rotating speed is decreased or increased, it enters the leakage state or negative pressure sealing state, respectively. The matching relationship between the rotating speed and inlet pressure has a significant effect on the pressurization value, pressurization coefficient and leakage flow rate. Under the working condition with a good match between the rotating speed and inlet pressure, the pressurization value increases significantly and the leakage flow rate decreases significantly, and the pressurization coefficient is stable between 0.88 and 0.89. The empirical formulas proposed by Wood and the Shanghai Research Institute of Chemical Industry (1979) have high reference values for the design of the liquid-sealing impeller with a flow channel (groove) and retainer.

https://www.mdpi.com/2227-9717/10/7/1366/pdf?version=1657705581

The Influence of Rotating Speed on the Sealing Characteristics of a Liquid-Sealing Impeller for a Liquid Oxygen Turbopump

This study investigated the sealing performance of the multistage liquid-sealing impellers of a turbopump. To achieve this purpose, the influence of each structural parameter in the impeller on the pressurization coefficient φ2 and the leakage flow rate Q was analyzed based on response surface methodology, taking the maximum pressurization coefficient φ2 and the minimum leakage flow rate Q as the optimization objectives. We obtained satisfactory ranges for parameters φ2 and Q. A set of parameter combinations was selected as the optimization scheme using the Box–Behnken method for the optimal solution design. The numerical simulation results show that to keep φ2 and Q in the better range, the value ranges of groove width b, groove depth h and groove number z should be (12.8–14 mm), (4.5–5.6 mm) and (23.5–28), respectively. Compared with the original model, the optimized version has an average increase of about 2.5% in pressurization coefficient φ2 at each rotation speed, an average of about 8.2% reduction in the leakage flow rate Q in the leakage state and an average increase in the reverse flow rate Q by about 6.7% in the negative pressure sealing state, indicating better sealing. By comparing pressure data at the experimental monitoring points, the proposed method was verified to have a high degree of confidence.

/pdf/the-optimization-of-a-first-stage-liquid-sealing-impeller-1us0qpar.pdf

Suguo Zhuang

Papers

Image post-processed approaches for cavitating flow in orifice plate

Inducer designing method based on centrifugal pump

Optimal design method for inducer with varying pitch of centrifugal pump

The Influence of Rotating Speed on the Sealing Characteristics of a Liquid-Sealing Impeller for a Liquid Oxygen Turbopump

The Optimization of a First-Stage Liquid-Sealing Impeller Structure for a Turbopump Based on Response Surface Methodology