Chapter 9 o Vapor Power Cycle 9 1

Chapter 9 o Vapor Power Cycle 蒸汽动力循环 9. 1 Basic Power Cycle using Water Vapor--Rankine Cycle (基本蒸汽动力循环---朗肯循环) o 9. 2 The Diesel Cycle (狄塞尔循环) o 9. 3 燃气轮机装置循环

RANKINE CYCLE

RANKINE CYCLE o o 1 2 Saturated or superheated steam enters the turbine at state 1, where it expands isentropically to the exit pressure at state 2. 2 3 The steam is then condensed at constant pressure and temperature to a saturated liquid, state 3. The heat removed from the steam in the condenser is typically transferred to the cooling water. 3 4 The saturated liquid then flows through the pump which increases the pressure to the boiler pressure (state 4). 4 1 the water is first heated to the saturation temperature, boiled and typically superheated to state 1. Then the whole cycle is repeated.

3. 如何提高朗肯循环的热效率 How can we increase the efficiency of the Rankine cycle T 1 5 6 影响热效率的参数 ？ 4 3 p 1 2 s t 1 p 2

§ 10 -2 蒸汽回热循环与再热循环 (regenerative cycle and reheat cycle) 1. 蒸汽回热循环(regenerative) 抽汽式回热 Feedwater heater 抽汽 冷凝水 Closed Feed water heater 去凝汽器 表面式回热器 抽汽 给水 冷凝水 Open Feedwater heater 混合式回热器

2. 蒸汽再热循环 (reheat cycle) 1 T 5 6 b 4 3 s When steam leaves the turbine, it is typically wet. The presense of water causes erosion of the turbine blades. To prevent this, steam extracted from high pressure turbine (state 2), and then it is reheated in the boiler (state 2') and sent back to the low pressure turbine

§ 10 -4 Internal combustion engines (内燃机) 1. The Otto Cycle (奥托循环） (1) Actual cycle (实际循环) The Otto cycle is an idealization of a set of processes used by spark ignition internal combustion engines (2 -stroke or 4 -stroke cycles).

Otto循环 a) ingest a mixture of fuel and air, b) compress it, c) cause it to react, thus effectively adding heat through converting chemical energy into thermal energy, d) expand the combustion products, and then e) eject the combustion products and replace them with a new charge of fuel and air.

_ (2) Otto循环的简化 We model all of these happenings by a thermodynamic cycle consisting of a set of processes all acting on a fixed mass of air contained in a piston-cylinder arrangement. The exhaust and intake processes are replaced by constant-volume cooling. ）

Representation of thermodynamic cycle. 1’ - 2 Compress mixture quasi-statically and adiabatically 2 - 3 Ignite and burn mixture at constant volume (heat is added) 3 (4)- 5 Expand mixture quasi-statically and adiabatically 5 - 1’’ Cool mixture at constant volume

2. The Diesel Cycle (狄塞尔循环) The diesel internal combustion engine differs from the gasoline powered Otto cycle by using a higher compression of the fuel to ignite the fuel rather than using a spark plug ("compression ignition" rather than "spark ignition")

3. The Dual Cycle (混合加热循环 )