Projekt i modelowanie rozprężarki tłokowej typu przelotowego, studium przypadku

A design of a reciprocating piston expander based on the uni-directional flow principle is proposed. The conversion of low value heat into mechanical work and electrical energy is a basic problem of small co-generation power plants. It is postulated that the proposed expander is appropriat for such applications. A methodology for engine design and modeling is brought forward and outlined. The design principle is based on the outlines proposed for steam engines by Stumpf [1]. The proposed design is of a horizontal, low speed unit designed with ease of manufacture in mind. Calculations based on the model show isentropic efficiencies around 70%, with the nominal power of 1,2 kW, for a machine working on 7 bar, mildly superheated steam, with the outlet pressure of 0,3 bar and condenser coolant used for residential heating. Furthermore, the most crucial mechanical and stress calculations are outlined.Przedmiotem pracy jest projekt tłokowego silnika parowego, jako rozprężarki dla siłowni parowych o małej mocy. Uznano, że dla założonych parametrów pary (7 bar na wlocie, 0,3 bar w skraplaczu) i przyjętej mocy w granicach 1,4 kW, konstrukcją optymalną ze względu na sprawność wewnętrzną i prostotę konstrukcji będzie maszyna o przepływie jednokierunkowym [1, 4]. W celu określenia jej wymiarów, stworzono uproszczony model obliczeniowy bazujący na założeniu, że sprężanie i rozprężanie pary to proces politropowy, w którym nadto wzięto pod uwagę straty ciśnienia pary na wlocie do maszyny, korzystając ze wzorów empirycznych [11]. Następnie, uzyskane w ten sposób wymiary wykorzystano jako dane dla kolejnego modelu, bazującego już na założeniu, że czynnik roboczy stanowi gaz rzeczywisty. Model ten utworzono w programie EES. Opiera się on na rozwiązywaniu równań bilansów w celu określenia parametrów pary w punktach charakterystycznych wykresu p-V. Następnie wykres jest kreślony przez program, zakładając przebieg krzywych wlotu i wylotu jako odpowiednio paraboli i funkcji wykładniczej (co stanowi dopuszczalne uproszczenie funkcji wylotu podanej przez Schulego [13] w tym szczególnym przypadku), oraz krzywych sprężania i rozprężania jako zbioru punktów dla procesu izentropowego (w ten sposób bierze się pod uwagę zmienność wykładnika izentropy). Zmieniając w modelu parametry prędkości obrotowej n i napełnienia ε rysuje się następnie charakterystyki mocy, momentu obrotowego i sprawności izentropowej maszyny. Osiągalne są sprawności izentropowe rzędu 0,8 przy małych mocach, oraz rzędu 0,7 przy mocach około nominalnych (1,4 kW). W dalszej części pracy pokazane są szczegóły obliczeń konstrukcyjnych proponowanej maszyny, w tym obliczenia zaworów wlotowych i obliczenia wytrzymałościowe wału i innych elementów. Na bazie ich wyników stworzono projekt silnika (w oprogramowaniu Solidworks)

Theoretical analysis of LNG regasifier supplementing gas turbine cycle

Liquefied natural gas (LNG) is transported by the sea-ships with relatively low pressure (0.13–0.14 MPa) and very low temperature (about 100 K) in cryo-containers. Liquid phase, and the low temperature of the medium is connected with its high exergy. LNG receives this exergy during the liquefaction and is related with energy consumption in this process. When the LNG is evaporated in atmospheric regasifiers (what takes place in many on-shore terminals as well as in local regasifier stations) the cryogenic exergy is totally lost. fortunately, there are a lot of installations dedicated for exergy recovery during LNG regasification. These are mainly used for the production of electricity, but there are also rare examples of utilization of the LNG cryogenic exergy for other tasks, for example it is utilized in the fruit lyophilization process. In the paper installations based on the Brayton cycle gas turbine are investigated, in the form of systems with inlet air cooling, liquid phase injection, exhaust gas based LNG evaporation and mirror gas turbine systems. The mirror gas turbine system are found most exegetically effective, while the exhaust gas heated systems the most practical in terms of own LNG consumption

Economical analysis of electric vehicles in Poland

The paper presents results obtained from calculations conducted to receive information on the capability of photovoltaic systems to power electric vehicles in regular use. The annual distance travelled was divided in nine categories. Every aspect of this analysis was suitable for Polish market and parameters given by the climate that is connected with geographical location of Poland. It is worth mentioning that one of the key elements is the law for renewable energy, that is the key aspect to economical benefits that come from so called green investments. Energy law was also taken into account during this simulation. All those aspects together summarized to a conclusions that Polish market is not as competitive as other European markets when electric propulsion is present in the system

Performance of micro CHP unit based on SI engine with quantitative-qualitative load control

The paper presents data resulting by the preliminary experimental tests performed on a micro CHP (combined heat and power) 7 kWel unit. The engine load has been controlled by throttle position (quantitatively) or/and the value of air excess ratio (qualitatively) QQLC. By this way the engine efficiency can be improved in the range of partial loads by reducing the exergy losses during the inlet stroke. During the tests engine has been powered with LPG fuel. The engine performance together with environmental impact has been studied in this paper. Used method shows that despite the reduction of the load from 5.6 kW to 4.7 kW while burning the lean mixture, the efficiency of electricity generation increased slightly. The efficiency grew by approx. 1.41 percentage point comparing with the results obtained for almost constant load but obtained by burning the lean mixture (λ = 1.3), followed by increased throttling and combustion of the stoichiometric mixture

Economical analysis of electric vehicles in Poland

The topic of this research was an answer to questions about economical advantages and disadvantages of an Electric Vehicle usage in Poland. Analysis done in this paper was based on current economical situation of automotive market. All the data collected for the purpose of comparison was obtained from manufacturers, government institutions or professional literature to ensure the quality of every calculation. Main concerns were covered by the comparison such as: usage of photovoltaic system to power electric vehicle, time of journey to the most popular destinations chosen by Polish citizens, cost of driving for internal combustion engines and electric vehicles. Research brought an answer that the cost of using an electric vehicle is highly dependent of electricity source. It can be also said, that not every region of Poland can guarantee a reasonable payback time when it comes to photovoltaic system and usage of electric vehicle in short distance regime