Flow Characteristics of the Nozzle Blade Cascade in the Mode of the Joint Operation with the Radial Diffuser

The obtained research data are given for the nozzle cascade used by a small-size gas turbine of an average fanning in combination with the radial diffuser. Aerodynamic characteristics of the nozzle blade cascade were determined in a wide range of a change in the Reynolds number varying from 4∙105 to 106 and the reduced velocity varying in the range of 0.4 to 1.13. The flow rate coefficient of the nozzle cascade was derived for all modes using the integral methods and the drainages behind the cascade. The kinetic energy loss coefficient and the flow angles were calculated using the measurement data of flow parameters in three control modes that were obtained due to the use of orientable pneumometric probes. When the expansion degree of the convergent –divergent annular duct behind the cascade is equal to 1.43 the flow in the narrow section of this duct is “enlocked” in the mode when the reduced velocity behind the cascade is equal to 1.127. At such velocity the Reynolds number 106 is self-similar for the flow rate coefficient. At lower values of Reynolds number, the decrease of it is accompanied by an intensive decrease in the flow rate coefficient for all the values of the reduced velocity. For the Reynolds number lower than 7∙105 an increase in the velocity results in a decreased flow rate coefficient. When this number exceeds 8∙105 an increase in the velocity results in an increase of the flow coefficient up to the moment when the flow is “enlocked” in the nozzle cascade.

Hydraulic Performance Analysis of Drip Irrigation System Using Pressure Compensated Dripper at Low Operating Pressure

Irrigation is the most important component in ensuring that crops can produce optimal yields. The use of drip irrigation can help farmers in providing water to crops in the amount required by the crop. Drip irrigation usually uses an uncompensated dripper and also a pressure compensated dripper. The use of an uncompensated dripper requires precise pressure to ensure a uniform flow for each dripper while the use of a pressure compensated dripper will also provide a uniform flow when operating pressure was used within the range specified by the dripper manufacturer. The purpose of this study is to evaluate the hydraulic performance of the drip irrigation system using low pressure compared to the minimum pressure recommended by dripper manufacturers. The pressure operation recommended by the manufacturer is 1.5-4 bars. This study uses pressures as low as 1 bar (low pressure), 2 bars, and 2.5 bars (recommended by manufacture) to operate this irrigation system. The volumetric approach was used to calculate each emitter's flow rate. Coefficient uniformity (CU), emission uniformity (EU), coefficient of variation (CV), and emitter flow variation (EFV) were the hydraulic parameters evaluated. The results show that CU, CV, and EU are in excellent classification, and the value for CU and the EU is more than 95 percent efficiency. The CV value is below 0.03 which is a very good classification. Meanwhile, emitter flow variation is 10% when operating at 2.5 bars and 2.0 bars and is considered the desirable classification. On the other hand, the emitter flow variation was reported at 6% for the 1 bar operating pressure and the classification was also recorded in the desirable classification. The results conclude that the use of low operating pressure compared to the minimum operating pressure proposed by the manufacturer can also operate in excellent condition according to the hydraulic parameters evaluated.

Flow rate changes of drippers with dilutions of treated water produced by oil exploration in the Brazilian semiarid region

The liquid residue called “produced water” from the exploitation of oil in the ground and sea is generated in large volumes and has significant polluting potential. In the Brazilian semiarid region, this liquid can be applied to the agricultural lands, if properly treated and applied to the soil by dripping. It is an alternative that can mitigate water scarcity and impacts on the environment. However, the vulnerability of drippers to clogging is a problem and can be mitigated with the dilution technique. The flow rate changes of drippers for the application of dilutions of produced water treated (PW) with underground water (UW) was analyzed. The experiment was conducted in a completely randomized split-split-plot design with three replications. Plots consisted of treatments (D1: 100% of UW, D2: 90% of UW and 10% PW, D3: 80% of UW and 20% of PW, D4: 70% of UW and 30% of PW and D5: 60% of UW and 40% of PW). The split-plots consisted of types of drippers (G1: 1.6 L h-1, G2: - 1.6 L h-1, G3: 1.7 L h-1) and split-split-plots consisted of evaluation times (0, 40, 80, 120 and 160 h). Flow rate (D) and flow rate coefficient of variation (FCV) were taken every 40 hours untill 160 h. The results showed that the G3 emitter was the most resistant to clogging. The dilutions D2 and D3 provided the lowest losses in hydraulic performance in the drip units. The highest rates of clogging occurred in the G2 emitter operating in the D5 dilution

Study of the vortex chamber and its application for the development of novel measurement and control devices

Based on studies of the flow structure in a short cylindrical vortex chamber, the dependence of the flow rate coefficient on its geometric parameters is proposed. It is shown that the liquid flow form in the chamber’s axial vortex the pressure on which surface is corresponds to the pressure of the outflow cavity. These results are used to measure pressure in high-temperature cavities, using a sleeve with a diameter equal to or slightly larger than the diameter of the axial vortex. The sleeve is installed in the vortex chamber, and connects the pressure on its surface to the pressure sensor. The possibility of using a vortex chamber as a damper of pressure fluctuations has been substantiated. The design of the vortex damper and its tests results are presented; these show the possibility of increasing the stabilization time of the outlet pressure more than three-fold. Variants of regulating devices with a vortex chamber, functioning without changing the flow cross-sections, are proposed and the results of their tests are presented. This is achieved either by introducing an obstacle into the chamber cavity or by displacing the axis of the outlet nozzle position.

Merging and splitting flows in a tee: the Pavlovsky method

Introduction. The Pavlovsky method is employed to consider the flows that merge and split inside a tee. Materials and methods. The problem of flows, merging and splitting inside a simple straight tee, is reduced to the problem of limits in a theory of functions applied to the characteristic function of a flow. The influence of the geometric parameter of a tee (a module), head losses and an external power source, produced on the flow rate coefficient in a tee, is identified in the work. Results. The co-authors identified a relation between the geometric parameters of a tee and its capacity in case of an isoenergetic flow and an external mechanical power supply. Conclusions. As for practical tasks, it is sufficient to reproduce a pentagon, stylizing a simple straight tee, on a strip having a ledge, while preserving the correspondence of points of polygons. The following conclusions are made: dissipation does not reduce the flow rate coefficient when flows merge, neither does it reduce the flow rate coefficient when flows split; minimum values of flow rate coefficient q = Q0/Q1 in case of merging flows are attained in the absence of dissipation, and they do not exceed the maximum value of the flow rate coefficient in case of splitting flows is attained in the absence of dissipation and it is not less than dissipation in a tee is explained by the flow separation from the vertex of angle B when flows merge and by the flow separation from the vertex of angle C when flows merge. Hydraulic losses do not reduce flow rate coefficient q = q+ when flows merge and do not increase flow rate coefficient q = q– when flows split. flow rate coefficient q+ goes down if a source of external mechanical power (a pump) is connected to a tee when flows merge; if flows split, the flow rate coefficient goes up and varies within the 1 < q– < 2 interval, and it doesn’t go up if q– > 2.

Thrust Force Measurements in an Axial Steam Turbine Test Rig

Large mechanical drive steam turbines used in the oil & gas industry are operating at increasingly higher inlet pressure, generating higher shaft power. Those higher power requirements result in larger disk diameters and surface areas. High thrust forces can be a result, due to both the high inlet pressure and large disk surface area. Industry standards require oversizing of thrust bearings to handle uncertainty in thrust predictions. These factors make improvement in thrust prediction accuracy and mitigation strategies important. A full-size, axial flow steam turbine test rig capable of measuring turbine thrust, and static pressure in the upstream rotor-stator cavity was built and commissioned. The test rig was operated in single stage configuration for the tests reported here. The rotor disk had balance holes and stationary axial face seals near the disk rim. The face seals divide the upstream rotor-stator cavity into inner and outer circumferential cavities. The rotor-stator cavity upstream of the rotor disk was instrumented, on the stationary wall, to measure the radial and circumferential pressure distribution. Bearing thrust was measured with load cells. Tests varied nominal pressure ratios (1.2, 1.5, 2.0 and 3.0), velocity ratios (0.35–0.6), admission fractions (0.25–1.0) and shaft leakage flow rates. Circumferential pressure asymmetry, due to partial admission operation, was confined to the outer cavity. The inner cavity pressure coefficient was circumferentially uniform at all operating points. The average pressure coefficient in the upstream rotor-stator cavity generally decreased as the shaft leakage flow rate coefficient increased. Increased leakage flow rate coefficient also increased the magnitude of the upstream directed or negative thrust.

Stator elements optimization of centrifugal compressor intermediate type stage by CFD methods

Optimal gas-dynamic design is a complex and time-consuming process. Modern CFD methods help in solving optimization problems and reliably calculating characteristics of stator elements of centrifugal compressor stages. To carry out such calculations, it is necessary to create a parametrized model, which facilitates automation of the process of changing the flow path geometry, rebuilding its dimensions and the computational grid. Using the Direct Optimization program of the ANSYS software package, we have optimized the flow path of the stator elements of a centrifugal compressor intermediate type stage consisting of a vaneless diffuser and a return channel. In this paper, the MOGA (Multi-Objective Genetic Algorithm) optimization method was used. The object of the study was stator elements of one of the model stages designed by the Problem Laboratory of Compressor Engineering, SPbPU. The goal was to achieve the minimum value of the loss coefficient of stator elements when changing 5 geometric parameters: the number of vanes, the inlet vane angle, the height of the vane at the inlet to the return channel vane cascade, the radius of curvature of the leading edge and the thickness of the vane profile. For the best variants based on the results of optimization, the characteristics of the loss coefficient depending on the flow rate coefficient were calculated, their characteristics were compared with the initial variant of the stator elements. The best variant in the design mode has a loss coefficient 4.4% lower than the reference model. With a flow rate coefficient of 1.63 times greater than the calculated one, the optimized variant’s loss coefficient is 33% less.

A New Practical Approach to the Design of Industrial Axial Fans: Tube-Axial Fans With Very Low Hub-to-Tip Ratio

This paper presents a simple but complete design method to obtain arbitrary vortex design tube-axial fans starting from fixed size and rotational speed. The method couples the preliminary design method previously suggested by the authors with an original revised version of well-known blade design methods taken from the literature. The aim of this work is to verify the effectiveness of the method in obtaining high-efficiency industrial fans. To this end, the method has been applied to a 315 mm rotor-only tube-axial fan having the same size and rotational speed, and a slightly higher flow rate coefficient, as another prototype previously designed by the authors, which was demonstrated experimentally to noticeably increase the pressure coefficient of an actual 560 mm industrial fan. In contrast, no constraints are imposed on the hub-to-tip ratio and pressure coefficient. The new design features a hub-to-tip ratio equal to 0.28 and radially stacked blades with aerodynamic load distribution corresponding to a roughly constant swirl at rotor exit. The ISO-5801 experimental tests showed fan efficiency equal to 0.68, which is 6% higher than that of the previous prototype. The pressure coefficient is lower, but still 12% higher than that of the benchmark 560 mm industrial fan.

A New Practical Approach to the Design of Industrial Axial Fans: Part I — Tube-Axial Fans With Very Low Hub-to-Tip Ratio

This paper presents a simple but complete design method to obtain arbitrary vortex design tube-axial fans starting from fixed size and rotational speed. The method couples the preliminary design method previously suggested by the authors ago with an original revised version of well-known blade design methods taken from the literature. The aim of this work is to verify the effectiveness of the method in obtaining high efficiency industrial fans. To this end, the method has been applied to a 315mm rotor-only tube-axial fan having the same size and rotational speed, and a slightly higher flow rate coefficient, as another prototype previously designed by the authors, which was demonstrated experimentally to noticeably increase the pressure coefficient of an actual 560mm industrial fan. In contrast, no constraints are imposed on the hub-to-tip ratio and pressure coefficient. The new design features a hub-to-tip ratio equal to 0.28 and radially stacked blades with aerodynamic load distribution corresponding to a roughly constant swirl at rotor exit. The ISO-5801 experimental tests showed a fan efficiency equal to 0.68, which is 6% higher than that of the previous prototype. The pressure coefficient is lower, but still 12% higher than that of the benchmark 560mm industrial fan.