Tag Archives: efficiency

1380–1387 V. Osadčuks, A. Kostromins, A. Pecka, V. Koteļeņecs and J. Jaško
Experimental efficiency evaluation of 445 nm semiconductor laser for robotized weed control applications
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Experimental efficiency evaluation of 445 nm semiconductor laser for robotized weed control applications

V. Osadčuks¹*, A. Kostromins², A. Pecka², V. Koteļeņecs³ and J. Jaško³

¹Latvia University of Life Sciences and Technologies, Faculty of Engineering, Čakstes blvd. 5, LV-3001 Jelgava, Latvia
²Latvia University of Life Sciences and Technologies, Faculty of Information Technologies, Liela street 2, LV-3001, Jelgava, Latvia
³Latvia University of Life Sciences and Technologies, Institute for Plant Protection Research “Agrihorts”, Paula Lejina iela 2, LV-3004 Jelgava, Latvia
*Correspondence: vtl@tvnet.lv

Abstract:

Robotized weed control is one of perspective approaches for decreasing ecological impact of farming. Although current level of technology development allows robotized weed control to be economically reasonable only in specific applications, it is only a matter of time to introduce them in full-scale industrial farming. In general terms weed control using agricultural robots consist of two parts: recognition and spatial localization of weeds (distinguishing them from crops) and precision application of some kind of growth limiting activity. Recognition and localization is usually carried out using computer vision solutions (image filtering and transformations, artificial neural networks etc.). Growth limiting in its turn is performed by mechanical, precise chemical, thermal, cryogenic or other means. This article covers application of laser radiation for thermal destruction of unwanted plant canopies. In most cases CO2 type lasers with 10.6 μm wavelength is used as they are affordable and they are applicable to use with plant biomass due to their spectral characteristics. Drawbacks of CO2 lasers are low efficiency, size, weight and complex maintenance. In recent years relatively powerful short-wavelength semiconductor lasers have became broadly available on market. Light absorption of healthy green leaves is much better in blue-UV spectrum than in green, far infrared and near infrared, which is almost completely reflected by leaves. Thus an experimental study of using 12 W output 445 nm blue semiconductor laser for weed canopy cutting was carried out. The experiments were performed with direct laser radiation, the laser module was positioned using robotic manipulator with different speeds and cutting patterns.

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862-887 H. Kaletnik, V. Mazur, I. Gunko, V. Ryaboshapka, V. Bulgakov, V. Raide, R. Ilves and J. Olt
Study on performance of compression engine operated by biodiesel fuel
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Study on performance of compression engine operated by biodiesel fuel

H. Kaletnik¹, V. Mazur¹, I. Gunko¹, V. Ryaboshapka¹, V. Bulgakov², V. Raide³, R. Ilves³ and J. Olt³*

¹Vinnytsia National Agrarian University of Ukraine, 3 Soniachna Str., UA21008 Vinnytsia, Ukraine
²National University of Life and Environmental Sciences of Ukraine, Ukraine, 15 Heroyiv Oborony Str., UA 03041 Kyiv, Ukraine;
³Estonian University of Life Sciences, Institute of Technology, 56 Kreutzwaldi Str., EE 51006 Tartu, Estonia
*Correspondence: jyri.olt@emu.ee

Abstract:

The analysis of the performance of biofuel is aimed at evaluating the energy efficiency of operating the engine with the use of biodiesel fuel as function of the fuel’s composition and other physical-and-chemical parameters. The mathematical models and analysis techniques known to the authors do not take into account the effect that the use of different bio-diesel fuels has on the operation of the engine and, therefore, need refinement in terms of the mathematical expressions and empirical formulae that describe the physical processes taking place in the engine’s cylinders. The aim of the study is to improve the mathematical relations taking into consideration the physical-and-chemical parameters of different types of fuel. The research methods proposed in the article are based on step-by-step consideration of the mathematical models of processes that follow each other, with due account for their possible overlapping, which jointly have an effect on the engine’s output indices. The boundary conditions and parameter increments are pre-set in electronic work sheets. Thus, it becomes possible, using the refined mathematical model, to calculate the main performance indices of the diesel engine with due account for the changes in the physical-and-chemical parameters of the fuel. The novelty of the described approach is in the possibility, through the use of the refined model and taking into account the data on the composition of the fuel and the design and operation parameters of the engine, to calculate the indices that allow evaluating the efficiency of use of specific fuels in the internal combustion engine under consideration. In results, formulas for the calculation of the effective power of the engine, fresh air charge density, excess air factor, effective specific fuel consumption and combustion pressure have been developed. Combustion pressure modelling and experimental data is presented.

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1824-1829 M. Polák
Application of conversion model for designing hydrodynamic pumps in turbine mode
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Application of conversion model for designing hydrodynamic pumps in turbine mode

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ16521, Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

The use of the smallest water resources has been coming again to the centre of interest in recent years. A water engine – turbine, is the heart of these power plants. This is usually the highest expense for the investor, in terms of cost. The effort is therefore to seek investment less demanding alternatives. One of them is the use of hydrodynamic pumps in reverse turbine operation. This paper provides a methodology for conversion of parameters of the smallest power pumps (micro hydro sites) to turbine operation. The conversion model is based on the results of experimental research at the author’s workplace and is suitable for pumps with low specific speeds and outputs. The pump design process for turbine mode is complemented by a practical example for a specific deployment site. This example also serves to verify the accuracy of the conversion model.

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1189–1197 M. Polák
Experimental evaluation of hydraulic design modifications of radial centrifugal pumps
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Experimental evaluation of hydraulic design modifications of radial centrifugal pumps

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ165 21, Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

In the field of small hydropower, pump units in turbine mode (PAT) are frequently used as alternative to conventional turbines. In order to maximize their operation efficiency, it is possible to optimize the performances of these engines through various simple innovative modifications which relate mainly to the geometry of the flow parts. This paper deals with the results of several successful modifications verified on one such engine. While various simple modifications led to the increase of overall efficiency and power output by few percentages, power output increased by nearly 30% with the innovated runner blades geometry. The modifications also had positive effects on the pump’s operation, with significant increases in flow rate, head and total efficiency.

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1652-1658 R. Neděla and R. Neděla
Support scheme for CHP and its sensitivity on heat wasting
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Support scheme for CHP and its sensitivity on heat wasting

R. Neděla¹* and R. Neděla²

¹Czech University of Life Sciences Prague, Technical Faculty, CZ 16521 Prague 6 – Suchdol, Czech Republic
²University of Economics, Prague, Faculty of International Relations, CZ 13067 Prague 3, W. Churchill 4 SQ, Czech Republic
*Correspondence: nedela@tf.czu.cz

Abstract:

This paper describes basic principles of the CHP, advantages and disadvantages, technologies. In first part of article are described principles of CHP from the viewpoint of the energy customer. Second part describes basic Directives by the European Commission on promotion CHP and third part the most important part focus on the sensitivity of primary energy saving (PES) on outputs especially heat wasting.

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280-286 I. Ziemelis, H. Putans and L. Kancevica
Investigation of Solar Collector Irradiated from Both Sides
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Investigation of Solar Collector Irradiated from Both Sides

I. Ziemelis, H. Putans and L. Kancevica

Research Institute of Agricultural Machinery, Latvia University of Agriculture,
Institute Street 1, LV–2130, Ulbroka, Riga region, Latvia
e-mail: Imants.Ziemelis@llu.lv; Liene.Kancevica@llu.lv

Abstract:

The ordinary flat plate solar collector receives solar radiation only from one side of its surface. Another side is covered with a heat barrier. The solar collector with reflectors has been developed and examined to track the sun. The absorber of this type of a collector was irradiated from both sides. The experimentally obtained energetic parameters of the collector tracking the sun have been compared to those of the ordinary flat plate solar collector. In order to complete the experiment, a special stand has been developed. The experimental investigation has been carried out at the intensity of radiation 2,000, 1,000 and 500 W m -2 in different combinations. The temperature has been measured in certain points of different parts of the collector by several thermocouples. With the aid of a multi-meter, the obtained results were collected to the memory of a computer, and later processed and analyzed. When a collector surface is tracking the sun, the heat energy produced by the collector is 1.4 to 1.5 times higher in comparison with a stationary solar collector of the same size. A solar collector tracking the sun and irradiated from both sides depending on the reflection quality of the reflector’s material is able produce about 2.5 times more heat energy then a stationary flat plate solar collector irradiated only from one side.

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