Development of micro soap bubble generator for PIV tracer using home stereolithography 3D printer

A micro soap bubble generator for tracers for PIV measurement was developed using a home stereolithography 3D printer. The nozzle has a coaxial triple pipe structure, and an orifice cap is attached to the nozzle head. The inner diameter of the central pipe is 0.7 mm, and the wall thickness of the central pipe is 0.7 mm. From the comparison of the smoke wire visualization result of the flow around the cylinder placed under the mainstream flow velocity of 3 m/s and the PIV measurement result, it was confirmed that the generated micro soap bubbles have good followability to the flow. Generated bubbles’ particle size was estimated to be Φ0.2 mm at the minimum and Φ6.3 mm at the maximum. The most common was Φ0.9 mm ± 0.1 mm, accounting for more than 50% of the total.

Parametric study of the effect of mode and geometric factors on the chamber coefficient of a liquid-propellant engine with a slotted nozzle head

The creation of advanced spacecraft requires developing new and improving existing now liquid-propellant rocket engines. In this case, one of the decisive factors determining their perfection is the design of the nozzle head of the combustion chamber, as well as the adopted scheme of mixing and burning rocket fuel. Thus, the optimization of the geometric and operating parameters of the combustion chamber is an urgent problem, which can be solved using both experimental and computational methods. The use of the latter can significantly reduce the volume of expensive bench tests. The article describes the study of a liquid-propellant engine chamber with a slotted nozzle head, in particular, the effect of the reduced length on the efficiency of the working process, assessed by the chamber coefficient. A mathematical model of the working process behaviour in the combustion chamber of a liquid-propellant rocket engine on oxygen-kerosene fuel components has been compiled. An algorithm for solving the equations of the mathematical model for the studied mixture formation scheme has been developed. Parametric calculations were performed and the main factors influencing the characteristics of the working process in the combustion chamber of a liquid-propellant engine with a slotted nozzle head were determined. Comparison of the calculation results according to the proposed method and the available results of bench tests showed their good convergence.

Influence of the nozzle head geometry on the energy flux of an atmospheric pressure plasma jet

The influence of different nozzle head geometries and, therefore, the variation of the excitation and relaxation volume on the energy flux from an atmospheric pressure plasma jet to a surface have been investigated. Measurements have been performed by passive calorimetric probes under variation of the gas flow through the nozzle. The results show that the geometry of the nozzle head has a significant impact on the resulting energy flux. The relaxation volume affects the dependence of the energy flux on the gas flow. While there is no significant influence of the working gas flow on the energy flux without a relaxation volume, utilizing a relaxation volume leads to a decrease of the energy flux with increasing working gas flow. Within the analyzed parameter range, the energy flux reveals for both nozzle heads a linear dependency on the applied primary voltage.

Experimental Research on the Efficiency of Impulse Turbine Based on Ultrasonic Flow Measurement Method

In this paper, we studied the impulse turbine of a power station based on the ultrasonic flow measurement method. Efficiency tests were carried out on the nozzle head, nozzle needle and deflector disc spring of the unit before and after the transformation. The results showed that the absolute efficiency of the unit before and after the transformation was basically the same. The efficiency value and economic performance have been improved to a certain extent, and the results obtained by using the ultrasonic method to carry out the unit efficiency test are correct and credible.

Research and Design of Pipe Cleaning Device with Self-Rotation

Background: With more and more blockages in the drainage pipe, recent patents on the design of pipe cleaning device are also addressed increasingly. But the current pipe cleaning device has only a single dredging function, and the inefficiency of the nozzle head, which cannot be used for cleaning of the seriously blocked pipelines. Objective: In order to solve these problems, a novel pipe cleaning device with self-rotation is proposed and the fluid simulation analysis is adopted for the low efficiency problem of the nozzle head in this paper. Methods: Firstly, the overall structure of the drainage pipeline cleaning device was designed. Secondly, the size of the nozzle and the nozzle head was determined. Thirdly, the fluid simulation analysis of the nozzle head was carried out to realize the optimal design of the nozzle head. Finally, according to the above design, a prototype was manufactured. Results: This paper presents a novel pipe cleaning device with self-rotation, which is different from current patents. It is divided into the nozzle head system, walking system, cleaning system, three-dimensional modeling and assembly of the above three mechanical systems. The simulation results demonstrated that if a deflector is not fixed inside the nozzle head, the pressure of the nozzle head is about 8542751.89Pa, and the flow rate at the outlet of the nozzle head is 354.897m/s. If a deflector is fixed, the corresponding data is 1.32e+008Pa and 446.336m/s. The result shows that the proposed new nozzle head optimization is effective. Conclusion: The new design solves the problems of the current patents about pipe cleaning device, and solves the key technical problems of inconvenient cleaning of pipe blockage and low efficiency nozzle head under complex working conditions. As a whole, this paper provides new ideas and new methods for the efficient work of pipe cleaning device and the removal of hard dirt on the inner wall of the pipeline.

Feasibility Study to Determine if Microfracture Surgery Using Water Jet Drilling Is Potentially Safe for Talar Chondral Defects in a Caprine Model

Objective Surgical microfracture is considered a first-line treatment for talar osteochondral defects. However, current rigid awls and drills limit access to all locations in human joints and increase risk of heat necrosis of bone. Using a flexible water jet instrument to drill holes can improve the reachability of the defect without inducing thermal damage. The aim of this feasibility study is to determine whether water jet drilling is potentially safe compared with conventional microfracture awls by studying side effects and perioperative complications, as well as the quality of cartilage repair tissue. Design Talar chondral defects with 6-mm diameter were created bilaterally in 6 goats (12 samples). One defect in each goat was treated with microfracture created with conventional awls, the contralateral defect was treated with holes created with 5-second water jet bursts at a pressure of 50 MPa. Postoperative complications were recorded and after 24 weeks analyses were performed using the ICRS (International Cartilage Repair Society) macroscopic score and modified O’Driscoll histological score. Results Several practical issues using the water jet in the operating theatre were noted. Water jet drilling resulted in fibrocartilage repair tissue similar to the repair tissue from conventional awls. Conclusions These results suggest that water jet drilling gives adequate fibrocartilage repair tissue. Furthermore, the results highlight essential prerequisites for safe application of surgical water jet drilling: stable water pressure, water jet beam coherence, stable positioning of the nozzle head when jetting, and minimizing excessive fluid extravasation.

Laser cladding of Co-based metallic powder at cryogenic conditions

Purpose: of this paper was demonstration a novel technique of laser cladding by experimentally composed Co-based metallic powder and forced cooling of the substrate by liquid nitrogen under cryogenic conditions, at the temperature -190°C, for producing clad layers with enhanced microstructure characteristic and properties. Design/methodology/approach: Technological tests of laser cladding were conducted by means of a high power fibre laser HPFL with maximum output power 3.0 kW, and six-axis robot. The experimental Co-based powder was composed for providing high abrasive wear resistance, high resistance for impact load, and also for corrosion resistance at elevated temperature. The unique and novel technique of forced cooling of the substrate was provided by immersing the specimens in the liquid nitrogen bath. The three coaxial nozzle head was designed and custom made to provide precise deposition of the powder delivered into the laser beam irradiation region. The scope of the study included tests of conventional laser cladding at free cooling in ambient air in a wide range of processing parameters, and also trials of laser cladding under cryogenic conditions. The test clad layers produced by conventional laser cladding and by the novel technique of laser powder deposition under cryogenic conditions were investigated and compared. Findings: The obtained results indicate that the novel technique of forced cooling the substrate by liquid nitrogen bath provides lower penetration depth, as well as low dilution of the clad, and also provides higher hardness of the clads. Additionally, it is possible shaping the geometry of the individual bead, providing high reinforcement and low width. Research limitations/implications: The presented results are based just on preliminary test of the novel technique of laser cladding under cryogenic conditions. Therefore, further study and detailed analyse of the influence of the cooling rate on the quality, microstructure, and properties of the deposited coatings are required. Practical implications: The study is focused on practical application of the novel technique for manufacturing of wear resistance coatings characterised with enhanced performance compared to conventional range of application of the laser cladding. Originality/value: Novel technique of laser cladding at forced cooling under cryogenic conditions was demonstrated. The powder used for cladding trials was experimentally composed (not commercially available). The experimental stand custom made was used with custom made powder feeding rate, and also with custom made coaxial nozzle head.