Features of hydraulic calculation of marine vacuum fish pumping units

Цель статьи – модифицировать ранее разработанный метод гидравлического расчета вакуумной перекачивающей системы для течения в рыбонасосной установке, работающей на промысловом судне. Динамика откачивания и закачивания воздуха в буферную емкость не изменилась. Анализ экспериментальных данных показал, что гидравлические потери по длине трубопровода прямо пропорциональны величине массовой доли рыбы. В судовых условиях потери напора в местных гидравлических сопротивлениях могут иметь тот же порядок, что и потери по длине. В отличие от традиционных судовых систем течение жидкости в вакуумных рыбонасосных установках (ВРУ) является нестационарным из-за увеличения давления в буферной емкости, как на этапе всасывания, так и на этапе вытеснения. Что приводит к необходимости совместного решения уравнения Бернулли для нестационарных течений совместно с дифференциальными уравнениями для давления и объема жидкости в буферной емкости. Увеличение длины трубопровода или перепада высот приводит к снижению скорости движения водорыбной смеси и увеличению давления в буферной емкости. Как следствие, возрастает продолжительность цикла работы ВРУ и падает производительность. The purpose of the article is to modify a previously developed method of hydraulic calculation of a vacuum pumping system for a flow in a fish pump unit operating on a fishing vessel. The dynamics of pumping out and pumping air into the buffer tank did not change. Analysis of experimental data showed that hydraulic losses along the length of the pipeline are directly proportional to the value of the mass fraction of fish. In shipboard conditions, head losses in local hydraulic resistances can be of the same order as length losses. In contrast to traditional ship systems, the fluid flow in vacuum fish pumping units (VFP) is unsteady due to an increase in pressure in the buffer tank, both at the stage of suction and at the stage of displacement. This leads to the need of jointly solve the Bernoulli equation for unsteady flows together with differential equations for the pressure and volume of fluid in the buffer tank. An increase in the length of the pipeline or the height difference leads to a decrease in the speed of movement of the water-fish mixture and an increase in pressure in the buffer tank. As a result, the duration of the VFP operation cycle increases and the productivity decreases.

Control of Runoff Peak Flow for Urban Flooding Mitigation

Urban flooding has become a serious but not well-resolved problem during the last decades. Traditional mainstream facilities, such as vegetated roofs, permeable pavements, and others, are effective to eliminate urban flooding only in case of small rains because the water-retaining and detaining capacities of these traditional facilities are limited. Here, we propose a new buffer tank buried in soil to deal with rainwater onsite as peak-flow control for urban flooding mitigation. Experiments showed that the buffer tank intercepts the surface runoff and discharges the intercepted water through a designed outlet orifice. By properly setting the cross-sectional area of the orifice, the tank extends the drainage duration several times longer than that of the rainfall duration. It is found that the buffer tank attenuates the peak flow greater at heavier rain. At small rain (<2.5 mm), the tank is always unfilled, preserving storage spaces for detaining rainwater in case of heavy rain. The buffer tank is thus greatly helpful to mitigate the flooding problem, avoiding being saturated by small long-lasting rain.

Active system for reduction of noise parameters of car muffler with the use of pressure sensors based on silicon microcrystals

Purpose: The article contains the results of research and development of a system for active noise damping of an automobile engine. The proposed system of active noise suppression can significantly reduce the sound pressure level in the frequency band up to 500 Hz. The robotic principle of the developed system is based on the addition of an additional buffer tank with a variable volume in the silencer system. The use of high-temperature sensors with strain gauges based on silicon microcrystals to obtain information on the parameters of sound vibrations arising during the exhaust gas outflow made it possible to create a control system for changing the volume of the buffer tank. The results of testing the proposed system of active noise suppression of an internal combustion engine are presented. Design/methodology/approach: The active noise suppression system based on the Helmholtz resonator used tools to control general noise levels, experimental tests, complex mathematical modelling of acoustic processes in Solidworks, taking into account the conditions of propagation and attenuation of sound energy by intermediate closed volumes. Findings: The use of an additional resonator chamber with variable volume in the exhaust muffler of the internal combustion engine allowed to reduce the resonant phenomena in the zone of low-frequency pulsations of exhaust gas pressure from 57 Hz to 43 Hz at frequency drift in the range of 310… 350 Hz, which significantly improved its noise characteristics. Research limitations/implications: For further research, to improve the characteristics of the active noise suppression system, it is advisable to consider the use of several inadditional cameras of the Helmholtz resonator and to clarify the algorithm of the controller in transient modes of engine operation. Practical implications: The developed design of active noise reduction is simpler in comparison with analogs and allows reducing the noise of exhaust gases in a low-frequency range. Originality/value: To reduce the noise, a variable-volume Helmholtz resonator was used, the efficiency of which is provided by high-temperature sensors of the original design.

Improving the lifetime of an electro-compressor for autoclave with optimized buffer tank

In order to increase the research capabilities in the field of lowweight intelligent materials and high structural performance, and also to increase energy efficiency, a study was conducted on improving the operating time of a hot air autoclave compressor with a buffer tank. The booster screw electro-compressor of 200 kW is designed to compress technological air to the installation’s necessary parameters at 1 ppm air purity, and the pressurized buffer tank is designed to reduce the number of start-ups of the compressor unit and its motor, in order to increase its lifespan. The pressure can vary in the designed buffer tank from 7 to 26 bar (abs). The autoclave parameters record thermodynamic modifications as it heats up to 400 °C at the working pressure. Cool air is required during the cooling process. The air mass exchanged during operation for cooling down to atmospheric temperature was calculated. The data obtained was used for validating an optimally designed buffer tank within the required operational parameters limits, set and acquired by the custom-made automation system.

Design and Experiment of Low-Pressure Gas Supply System for Dual Fuel Engine

A low-pressure gas supply system for dual fuel engines was designed to transport liquid natural gas from a storage tank to a dual fuel engine and gasify it during transportation. The heat exchange area and pressure drop in the spiral- wound heat exchanger, the volume of the buffer tank and the pressure drop in the pipeline of the gas supply system were calculated by programming using Python. Experiments were carried out during the process of starting and running the dual fuel engine using this gas supply system. Experimental data show that the gas supply system can supply gas stably during the process and ensure the stable operation of the dual fuel engine. The effects of the parameters of natural gas and ethylene glycol solution on the heat exchange area of the spiral-wound heat exchanger and the volume of the buffer tank in the gas supply system were studied. The results show that the heat exchange area calculated according to pure methane can adapt to the case of non-pure methane. The temperature difference between natural gas and ethylene glycol solution should be increased in order to reduce the heat exchange area. The heat exchange area selected according to the high pressure of natural gas can adapt to the low pressure of natural gas. The volume of the buffer tank should be selected according to the situation of the minimum methane content to adapt to the situation of high methane content. The main influencing factor in selecting the volume of the buffer tank is the natural gas flow. The results can provide guidance for the design of the gas supply system for dual fuel engines.