Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis of start energy of Stirling engine type alpha

100%

Kropiwnicki J.

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2019

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tom Vol. 40, no 3

243--259

EN

The Stirling engine type alpha is composed of two cylinders (expansion space E and compression space C), regenerator that forms the space between the cylinders and the buffer space (under the pistons). Before the start-up and as a result of long-term operation, the average pressure in the working space (above the pistons) and in the buffer space is the same. However, in the initial phase of operation, the average pressure in the working space is different then the average pressure in the buffer space depending on the crankshaft starting position (starting angle). This, in turn, causes a large variation in the starting torque. An additional unfavorable factor caused by a large variation in the course of the indicated torque is the rotational speed variation and the formation of torsional vibrations in the drive system. After some time, depending on the quality of the engine piston sealing, the average pressure in the working and buffer space will equalize. The occurrence of the above-described phenomenon affects the selection of the starting electric motor, which can be significantly reduced, when the crankshaft starting position is optimized (the starting torque is several times greater than the average torque occurring in the generator operation mode). This paper presents the analysis of the impact of the crankshaft starting position on the course of the indicated torque and the resulting start-up energy. Starting the engine at an unfavorable position of the crankshaft may, in extreme cases, increase the starting torque even three times.

2

Analysis of the regenerative braking process for the urban traffic conditions

63%

Kropiwnicki J. , Furmanek M.

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tom R. 58, nr 3

203--207

EN

In a regular drive system, with an internal combustion engine, vehicle braking is connected with the unproductive dissipation of kinetic and potential energy accumulated in the mass of the vehicle into the environment. This energy can constitute up to 70% of the energy used to drive a vehicle under urban conditions. Its recovery and reuse is one of the basic advantages of hybrid and electric vehicles. Modern traffic management systems as well as navigation systems should take into account the possibility of the energy recovery in the process of regenerative braking. For this purpose, a model of a regenerative braking process may be helpful, which on the one hand will enable to provide information on how traffic conditions will affect the amount of energy dissipated (wasted) into the atmosphere, on the other hand will help to optimize the route of vehicles with regenerative braking systems. This work contains an analysis of the process of the regenerative braking for the urban traffic conditions registered in Gdańsk. A model was also presented that allows calculating the amount of energy available from the braking process depending on the proposed variables characterizing the vehicle traffic conditions.

3

Hydraulic resistance analyses of selected elements of the prototype Stirling engine

63%

Furmanek M. , Kropiwnicki J.

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2019

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tom Vol. 40, no 3

123--136

EN

The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.

4

Evaluation of the energy efficiency of electric vehicle drivetrains under urban operating conditions

63%

Kropiwnicki J. , Gawłas T.

Combustion Engines

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2023

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tom R. 62, nr 4

28--34

EN

In electric vehicles, as in hybrids vehicles, a very important factor affecting the energy efficiency of the power-train is the ability to use the regenerative braking energy. Depending on the settings available in electric vehicles, the driver can choose different modes of operation: switch off the regenerative braking mode altogether, select the intensity of regenerative braking, or leave the control system in automatic mode. The last mode is often the only one available on eclectic vehicles, so the driver cannot decide whether to switch off or increase intensity of the regenerative braking. This paper presents a new method for evaluating the energy efficiency of electric vehicle powertrains under urban operating conditions. The presented method uses a procedure for mapping the operating conditions allowing to determine the reference level of energy consumption in relation to those recorded during the identification tests. Identification tests were carried out in the Tri-City area using electric vehicles of different purposes and operating parameters. Performed tests allowed to evaluate the regenerative braking efficiency of tested vehicle, which varies over a relatively wide range, for vehicle A from 33 to 77%, for vehicle B from 27 to 55% and for vehicle C from 36 to 58%. It can be concluded that one of the main factors determining the regenerative braking efficiency is the level of state of charge of the accumulator and the management algorithm used by the vehicle for controlling this parameter.

5

Experiments on compression ignition engine powered by nano-fuels

51%

Cieśliński J. T. , Krzyżak J. , Kropiwnicki J. , Kneba Z.

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tom R. 61, nr 1

55--59

EN

The use of nanoparticles in fuels provides new opportunities for modification of fuel properties, which may affect the operational parameters of engines, in particular the efficiency and fuel consumption. The paper presents comparison of compression ignition engine performance fuelled with neat diesel and nano-diesel. Alumina (Al2O3) was used as nanoparticles. Surface-active substances, including Span 80 surfactant, as well as water admixture were used to improve the stability of the produced fuel. Measurements of the thermal conductivity and dynamic viscosity of the produced mixtures were conducted. In this study was used naturally aspirated, water cooled, four-stroke diesel engine. Addition of Al2O3 nanoparticles result in 4% reduced fuel consumption, addition of TiO2 nanoparticles result in 10% reduced fuel consumption with respect to neat diesel fuel.

6

Forecasting biogas formation in landfills

51%

Kneba Z. , Kropiwnicki J. , Hadrzyński J. , Ziółkowski M.

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2023

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tom Vol. 17, no. 2

281--287

EN

The aim of the present research was to develop a mathematical model for estimating the amount of viscous gas generated as a function of weather conditions. Due to the lack of models for predicting gas formation caused by sudden changes in weather conditions in the literature, such a model was developed in this study using the parameters of landfills recorded for over a year. The effect of temperature on landfill gas production has proved to be of particular interest. We constructed an algorithm for calculating the amount of the produced gas. The model developed in this study could improve the power control of the landfill power plant.