The Poznań University of Technology Faculty of Engineering Management. Technique lead-in - Energy, Energy conversion efficiency, Work exercises

Transcription

1 The Poznań University of Technology Faculty of Engineering Management Technique lead-in - Energy, Energy conversion efficiency, Work exercises

2 Energy ability to induce change (action) Energy is a function of a state whose value depends on the states parameters and is being kept as long as the state exists Energy is the physical quantity that determines the body's ability to perform work The unit of Energy, Work and Heat in the SI is 1 joule [1J] = 1 Newton meter [1 M m] = 1 watt seconds [1W s] In practice, multiples are being used: 1 kilojoule [1kJ], 1 megajoule [1 MJ], 1 gigajoule [1 GJ], 1 kilowatt hour [1 kw h] 2

3 Energy sources Renewable S U N (no combustion process) Radiation energy Energy waves Air mass movement Biomass Energy of the wind electricity (photovoltaic cells) Collectors Others: Geothermal energy, 3

4 Energy sources Nonrenewable F U E L S (contains chemical energy, expressed by calorific value). These sources do not renew in a short time. We distinguish fuels: solid liquid gass nuclear 4

5 A device, whose operation in a continuous way would not require bring energy to it, is called: Perpetuum mobile of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy. perpetuum mobile of second kind machine which spontaneously converts thermal energy into mechanical work. It violates the second law of thermodynamics. perpetuum mobile of third kind usually defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever (due to its mass inertia). 5

6 Conservation of Energy law Energy can not come out of nothing or be destroyed. Energy only changes its form Pojawa B., Termodynamika techniczna Część 1, Akademia Marynarki Wojennej, Gdynia 2015

7 Mechanical energy It is a form of energy related to the movement and position of an object (the body of mass m) and with the elastic deformation of the body potential (associated with interaction) potential (associated with elasticity) kinetic energy in progressive motion kinetic energy in rotational motion

8 Energy transformation A technological process in which one form of energy (usually a primary energy carrier) is converted into another, derived energy form 8

9 = Energy conversion efficiency The ratio between the useful output of an energy conversion machine and the input, in energy terms. Wykres Sankeya Indicates % of "energy" lost as a result of the change 9

10 Thermodynamic system Quantitative comparison of all types of energy involved in energy processes taking place in the analyzed engines, equipment and power engineering E f f i c i e n c y 10

11 Thermodynamic system In most engines and power systems, four types of power transmission are most commonly encountered: by electric current (electricity) by performing mechanical work (mechanical energy) by heat flow (heat) by means of a stream of substance (enthalpy) 11

12 Engine Machine type replacing energy into mechanical work thermal engine electric engine water engine pneumatic motor hydraulic engine wind turbine 12

13 Transmission Mechanism or arrangement of machines for transferring motion from active (driving) to passive (driven) with simultaneous change of motion parameters, ie speed and force or torque Transmission can change: Rotational motion to rotational motion - the most common case rotational motion to the linear motion or vice versa linear motion to linear motion Transmission kinds: mechanical hydraulic pneumatic electrical 13

14 Conversion Conversion i" of pair of wheels is the ratio of the number of teeth, the speed of rotation of the driving wheel to the driven. (dimensionless) Dependencies are as follows: if i >1 then deaccelerate conversion: z 1 < z 2; n 1 > n 2; M o1 < M o2 if i = 1 then direct conversion: z 1 = z 2; n 1 = n 2; M o1 = M o2 Two gears (pair) lie on one shaft and always rotate at the same speed if 0 < i < 1 then accelerate conversion (overdrive): z 1 > z 2; n 1 < n 2; M o1 > M o2 14