斯特林发动机原理

11/11/2007 UNIVERSITY OF GÄVLE STIRLING ENGINE MAIER Christoph GIL Arnaud AGUILERA Rafael SHUANG Li YU Xue 2 Stirling Engine IndexIndexIndexIndex Summary ........................................................................................................................ 3 Introduction .................................................................................................................... 4 History............................................................................................................................ 5 Presentation of Stirling Engines..................................................................................... 7 I. Stirling thermodynamic cycle ............................................................................. 7 II. Engine configurations ......................................................................................... 8 1. Alpha Stirling: ................................................................................................. 9 2. Beta Stirling................................................................................................... 11 3. Gamma Stirling ............................................................................................. 13 4. Other types .................................................................................................... 14 Reasons to use a Stirling Engine .................................................................................. 15 Analyze from Economic point ..................................................................................... 18 Applications of the Stirling power ............................................................................... 20 I. Cars ................................................................................................................... 20 II. Submarine ......................................................................................................... 21 III. Aircrafts ......................................................................................................... 22 IV. Heat and power System ................................................................................. 23 V. Cryocooler......................................................................................................... 24 VI. Nuclear power ............................................................................................... 24 VII. Solar Energy .................................................................................................. 25 Conclusion ................................................................................................................... 29 References .................................................................................................................... 31 Stirling Engine 3 SummarySummarySummarySummary This essay mainly makes an exposition of the Stirling Engine. Firstly, the history of Stirling Engine is showed to make a guide of first comprehension. Then the Stirling Engine’s thermodynamic cycle is explained and the configuration is analyzed, which we do to make sure a further insight into the Stirling Engine. After that, the reasons to use a Stirling Engine are discussed, especially from an economic point of view. This is to describe why the Stirling Engine is widely used in nowadays’ world. And the last part is to show out how the Stirling Engine is applied in each field. But with a special focus on sterling engines in applications with renewable energies. This whole essay displayed a broad overall presentation to the Stirling Engine, and analyzed its intrinsic value for the future. 4 Stirling Engine IntroductionIntroductionIntroductionIntroduction "…These imperfections have been in a great measure removed by time and especially by the genius of the distinguished Bessemer. If Bessemer Iron or steel had been known thirty five or forty years ago there is a scarce doubt that the air engine would have been a great success … It remains for some skilled and ambitious mechanist in a future age to repeat it under more favorable circumstances and with complete success…" (Written in the year 1876 by Dr. Robert Stirling [1790-1878]) The Stirling Engine was invented by Robert Stirling. This device was born as a competence to the vapor machine, since a Stirling Engine works with smaller pressures than the device created by Watt and it did not require a qualified train engineer. At the end of s.XIX with the development of the internal combustion engine and the appearance of electric engines, the machine of this study was forgotten. Nowadays the technology that involves the invention of Robert Stirling is in completely development because of the fact that now very useful applications are available. This document travels in the history of this curious device looking for reasons of this incredible development in this called high technology with its different applications and doing an analysis from the point of view of the economy. This project explains the principle function of the engine with a deep investigation. And we show how the Sterling Engine in combination with renewable energy sources can be part of a sustainable energy supply. Figure 1 : Sketch of Robert Stirling of his invent Stirling Engine 5 HHHHistoryistoryistoryistory The Stirling Engine is one of the hot air engines. It was invented by Robert Stirling (1790-1878) and his brother James. His father was interesting in engine and he inherited it. He became a minister of the church at Scotland in 1816. At this period, he found the steam engines are dangerous for the workers. He decided to improve the design of an existing air engine. He hope it wound be safer alternative. After one year, he invented a regenerator. He called the “Economiser” and the engine improves the efficiency. This is the earliest Stirling Engine. It is put out 100 W to 4 kW. But the internal combustion engine substituted for it quickly. The Ericsson invented the solar energy in 1864 and did some improvements for after several years. Robert’s brother, James Stirling, also played an important role in the development of Stirling engines. Figure 2 : Earliest Stirling engine Robert Stirling gets a patent for the economizer with an air engine incorporating it in 1817. Since the Stirling engine worked at a lower pressure, and could not cause steam burns, the danger to explode is impossible. In 1818 he built the first practical exponent of his engine, used to pump water from a quarry. The inventors sought to create a safer engine instead of steam engines at that time, whose boilers often exploded as a result of high pressure of the steam and the inadequate materials. The original patent by Reverend Stirling was called the "economizer", for its improvement of fuel-economy. The patent also mentioned the possibility of using the 6 Stirling Engine device in an engine. Several patents were later determined by two brothers for different configurations including pressurized versions of the engine. This component is now commonly known as the "regenerator" and is essential in all high-power Stirling devices. Figure 3 : Stirling Engine’s principle of operation Stirling engine of the second generation began in 1937.The Philips of Holland used new materials and technology to ascend a very high level. The knowledge about the heat transfer and fluid physical, which is a great significance to improving of the structure and raised the stability. Throughout World War II and by the late 1940s, Philips’ subsidiary Johan de Witt does this work continued. And they did the Type 10, incorporated into a generator set as originally planned The set progressed through three prototypes (102A, B, and C), with the production version, rated at 200 watts electrical output from a bore and stroke of 55x27mm, being designated MP1002CA. In 1951, the price of Stirling engine is too high for the market. It made used of radios at that time. Though the MP1002CA may have been a dead end, it represents the blooming of the modern age of Stirling Engine development. In addition to which the advent of transistor radios with their much lower power requirements meant that the market for the set was fast disappearing. Though the MP1002CA may have been a dead end, it represents the start of the modern age of Stirling engine development. Stirling Engine Presentation of Stirling Presentation of Stirling Presentation of Stirling Presentation of Stirling I. Stirling thermodyna The Stirling engine fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle is that of thermal expansion and contraction of this fluid due to a temperature differential. So the ideal Stirling cycle consists of four thermodynamic acting on the working fluid: volume processes. Each one of which can be separately analysed: � 1-2: isothermal compression process fluid, while an equal amount of heat Q cooling source. The working fluid cools and contracts at constant TC. � 2-3: constant volume displacement process with heat addition absorbed by the working fluid and temperature is raised from T work is done. � 3-4: isothermal expansion process while an equal amount of heat Q source. The working fluid heats and expands at constant temperature T � 4-1: constant volume displacement process with heat rejection rejected by the working fluid work is done. Figure Stirling Engine Presentation of Stirling Presentation of Stirling Presentation of Stirling Presentation of Stirling EnginesEnginesEnginesEngines Stirling thermodynamic cycle The Stirling engine cycle is a closed cycle and it contains, most commonly a fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle ansion and contraction of this fluid due to a temperature So the ideal Stirling cycle consists of four thermodynamics distinct processes fluid: two constant-temperature processes and two constant ch one of which can be separately analysed: isothermal compression process. Work W1-2 is done on the working fluid, while an equal amount of heat Q1-2 is rejected by the system to the cooling source. The working fluid cools and contracts at constant onstant volume displacement process with heat addition absorbed by the working fluid and temperature is raised from T isothermal expansion process. Work W3-4 is done by the working fluid while an equal amount of heat Q3-4 is added to the system from the heating source. The working fluid heats and expands at constant temperature T constant volume displacement process with heat rejection rejected by the working fluid and temperature decrease from T Figure 4 : A pressure/volume graph of the ideal Stirling cycle 7 Presentation of Stirling Presentation of Stirling Presentation of Stirling Presentation of Stirling it contains, most commonly a fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle ansion and contraction of this fluid due to a temperature distinct processes temperature processes and two constant- is done on the working is rejected by the system to the cooling source. The working fluid cools and contracts at constant temperature onstant volume displacement process with heat addition. Heat Q2-3 is absorbed by the working fluid and temperature is raised from TC to TH. No is done by the working fluid, is added to the system from the heating source. The working fluid heats and expands at constant temperature TH. constant volume displacement process with heat rejection. Heat Q4-1 is and temperature decrease from TC to TH. No 8 Stirling Engine The process lines in the figure above reflect the properties of an ideal gas. The main processes, like for most heat engines, are cooling, compression, heating and expansion. A Stirling engine operates through the use of an external heat source and an external heat sink having a sufficiently large temperature difference between them. Compared to the ideal cycle, the efficiency of a real engine is reduced by irreversibilities, friction, and the loss of short-circuit conducted heat, so that the overall efficiency is often only about half of the ideal (Carnot) efficiency. The gasses used inside a Stirling engine never leave the engine. There are no exhaust valves that vent high-pressure gasses, as in a gasoline or diesel engine, and there are no explosions taking place. Another useful characteristic of the Stirling engine is that if supplied with mechanical power, it can function as a heat pump (reversibility of the Stirling cycle). Understanding how a Stirling engine works is not a simple matter. It is not overly intuitive. Let’s explain the device through the presentation of the different engines configuration. II. Engine configurations Mechanical configurations of Stirling engines are classified into three important distinct types: Alpha, Beta and Gamma arrangements. These engines also feature a regenerator (invented by Robert Stirling). The regenerator is constructed by a material that conducts readily heat and has a high surface area (a mesh of closely spaced thin metal plates for example). When hot gas is transferred to the cool cylinder, it is first driven through the regenerator, where a portion of the heat is deposited. When the cool gas is transferred back, this heat is reclaimed. Thus the regenerator “pre heats” and “pre cools” the working gas, and so improve the efficiency. But many engines have no apparent regenerator like beta and gamma engines configurations with a “loose fitting” displacer, the surfaces of the displacer and its cylinder will cyclically exchange heat with the working fluid providing some regenerative effect. Stirling Engine 9 1. Alpha Stirling: Alpha engines have two separate power pistons in separate cylinders which are connected in series by a heater, a regenerator and a cooler. One is a “hot” piston and the other one a “cold piston”. The hot piston cylinder is situated inside the high temperature heat exchanger and the cold piston cylinder is situated inside the low temperature heat exchanger. The generator is illustrated by the chamber containing the hatch lines. Figure 5 : Alpha engine’s configuration Expansion: At this point, the most of the gas in the system is at the hot piston cylinder. The gas heats and expands, pushing the hot piston down, and flowing through the pipe into the cold cylinder, pushing it down as well. Transfer: At this point, the gas has expanded. Most of the gas is still in the hot cylinder. As the crankshaft continues to turn the next 90°, transferring the bulk of the gas to the cold piston cylinder. As it does so, it pushes most of the fluid through the heat exchanger and into the cold piston cylinder. 10 The Alpha engine is c however suffers from the disadvantage that both pistons need to have seals to contain the working gas. Contraction: Now the majority of the expanded gas is shifted to the cool cylinder. It cools and contracts, drawing both pistons up Figure 6 : Example of a real cycle of an Stirling Engine This diagram is feature of an alpha engine. The most important is to have the biggest grey area which represents recuperated work during a cycle. The Alpha engine is conceptually the simplest Stirling engine configuration, however suffers from the disadvantage that both pistons need to have seals to contain Now the majority of the shifted to the cool piston It cools and contracts, drawing Transfer: The fluid is cooled and n crankshaft turns another 90°. therefore pumped back, through the heat exchanger, into the hot piston Once in this, it is heated and we go back to the first step. alpha engine This diagram is feature of an alpha engine. The most important is to have the biggest area which represents the recuperated work during a cycle. onceptually the simplest Stirling engine configuration, however suffers from the disadvantage that both pistons need to have seals to contain The fluid is cooled and now the shaft turns another 90°. The gas is therefore pumped back, through the heat the hot piston cylinder. it is heated and we go back Stirling Engine This type of engine has a very high power problems due to the usually high temperature of the "hot" piston and its seals 2. Beta Stirling The Beta configuration is the classic Stirling engine configuration and has enjoyed popularity from its inception until today. Stirling's original engine from his patent drawing of 1816 shows a Beta arrangement. Both Beta and Gamma engines use displacer engine has both the displacer and the piston in an in engine uses separate cylinders. The purpose of th working gas at constant volume, and shuttle it between the expansion and the compression spaces through the series arrangement cooler, regenerator, and heater. A beta Stirling has a single power p the same shaft as a displacer piston. The displacer piston is a loose fit and does not extract any power from the expanding gas but only serves to shuttle the working gas from the hot heat exchanger to the cold heat exchanger. When the working gas is pushed to the hot end of the cylinder it expands and pushes the power piston. When it is pushed to the cold end of the cylinder it contracts and the momentum of the machine, usually enhanced by a flywheel, pushes the compress the gas. Unlike the alpha type, the beta type avoids the technical problems of hot moving seals. Stirling Engine This type of engine has a very high power-to-volume ratio but has technical usually high temperature of the "hot" piston and its seals The Beta configuration is the classic Stirling engine configuration and has enjoyed popularity from its inception until today. Stirling's original engine from his 1816 shows a Beta arrangement. Both Beta and Gamma engines use displacer-piston arrangements. The Beta engine has both the displacer and the piston in an in-line cylinder system. The Gamma engine uses separate cylinders. The purpose of the single power piston and displacer is to “displace” the working gas at constant volume, and shuttle it between the expansion and the compression spaces through the series arrangement cooler, regenerator, and heater. A beta Stirling has a single power piston arranged within the same cylinder on the same shaft as a displacer piston. The displacer piston is a loose fit and does not extract any power from the expanding gas but only serves to shuttle the working gas from the hot heat at exchanger. When the working gas is pushed to the hot end of the cylinder it expands and pushes the power piston. When it is pushed to the cold end of the cylinder it contracts and the momentum of the machine, usually enhanced by a flywheel, pushes the power piston the other way to compress the gas. Unlike the alpha type, the beta type avoids the technical problems of hot moving seals. Figure 7 : Beta engine’s configuration Figure 11 volume ratio but has technical usually high temperature of the "hot" piston and its seals The Beta configuration is the classic Stirling engine configuration and has enjoyed popularity from its inception until today. Stirling's original engine from his piston arrangements. The Beta line cylinder system. The Gamma e single power piston and displac