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1、第一章 发动机性能及其参数1 三种理想循环1)otto cycle : 2)diedel cycle : 3)dual cycle;(the efficiency lies between )isentropic compression ;addition of heat ;isentropic expansion ;rejection of heat;2评价理论循环的参数Cycle fuel conversion efficiency ht 和Mean effective pressure Ptht : The cycle fuel conversion efficiency ht is u
2、sed to evaluate the cycle economy, which is defined as:(t increases with the increasing of compression ratio , pressure ratio , isentropic exponent K and decreases with the increasing of expansion ratio .)Pt: Pt is cycle work done by unit cylinder volume.It is used to evaluate the power capability o
3、f a cylinder :(Pt increases with increasing of pa、e 、l、r、 k and ht.)3real cycle 实际循环1、intake(induct) stroke 2、compression stroke3、power(combustion) stroke 4、exhaust stroke4 Which losses existed in real cycle compared with ideal cycle? explain every loss and the forming reason. (实际循环与理想循环相比，存在的损失及其形成
4、原因。)1) Heat transfer. Heat transfer from unburned mixture to the cylinder walls. The pressure at the end of combustion in the real cycle will be lower. 2) Finite combustion time. Finite time required to burn the charge. The peak pressure in the engine is below the ideal cycle peak pressure value.3)
5、Incomplete bustion of the cylinder charge is incomplete;the exhaust gases contain combustible species .4) Exhaust blowdown loss. The gas pressure at the end of expansion stroke is reduced.5) Crevice effects and leakage. These effects reduce the cylinder pressure .6)Pumping loss. The work is used to
6、overcome the resistance in inlet and exhaust passages. 5 engines indicated parameters a (发动机指示指标及作用？和类容)1概念及作用：.Indicated parameters: The parameters are calculated on basis of the work done by working fluid to pistons .it is widely used to evaluate the conversion efficiency of heat into power per cy
7、cle and is widely used in engine research field .2内容1、Indicated work per cycle Wi（循环指示功）2、Indicated mean effective pressure(imep) Pmi （平均指示压力）3、Indicated power Pi (指示功率)Pi(kw)=Pmi(Mpa)*Vs(L)*n(r/min)*i/30*tao （i为汽缸数，tao为冲程数）4、Indicated efficiency i （指示热效率）5、Indicated specific fuel consumption bi （指示
8、油耗率）指示热效率与指示油耗率的关系6 engine brake parameters (何谓发动机有效指标及作用)1概念：Engine brake parameters are based on engine crankshaft output work. It is used to evaluate economic and dynamic performance of an engine。2内容：1.Brake torque Ttq and power Pe （有效转矩和有效功率） 2. Brake work We and brake mean effective pressure Pm
9、e (有效功和平均压力)We=Wi-Wm Wi-指示功 ； Wm-机械损失功 3.Brake(thermal) efficiency e （有效热效率）4.Brake specific fuel consumption (bsfc) be （有效油耗率）热效率有油耗率的关系5.Engine specific power PL （升功率）7engine mechanical efficiency (机械效率)定义：The ratio of the brake (or useful) power delivered by the engine to the indicated power is c
10、alled the mechanical efficiency m: . 影响因素：The facts that influence it are: the peak combustion pressures in cylinder, engine speed or piston mean speed, engine loads, the characteristic of lubrication and temperature of cooling water, and the conditions of engine runs. 第二章 发动机的换气1 gas exchange proce
11、sses of four-stroke engine. （四冲程发动机换气过程）The gas exchange process of an engine consists of the duration from opening the exhaust valve to closing the inlet valve .it can ba divided into four phases 1.blowdown 自由排气 2.displacement 强制排气3.induction process 进气行程 4.valve overlap and scavenging 气门重叠与扫气2 vol
12、ume coefficient hv 充量系数（容积效率） 重点定义：Volume efficiency is a measure of the effectiveness of the induction and exhaust process which is defined as the mass of fresh mixture which passes into the cylinder in one suction stroke, divided by the mass of this mixture which would fill the piston displacement
13、 at inlet density. .提高充量系数In a qualitative analysis, volumetric efficiency v increases with:1) increasing mixture pressure at the end of intake stroke pa；（影响最大）2) suitable valve parameters and; 3) increasing compression ratio ; 4) decreasing mixture temperature at the end of intake stroke Ta；5) redu
14、cing residual coefficient . 必考内容（可能是大题）3effect of operating conditions and design on volumetric efficiency1.Inlet Match index 进气马赫数定义：The ratio of the typical velocity to the inlet sonic velocity, u /, is called the inlet Mach index. When it exceeds 0.55, volumetric efficiency drops greatly.2.Effect
15、 of intake system friction 进气摩擦力3.Effect of inhaled charge heating 受热程度4.Effect of speed and valve timing 速度与气门正时5.Effect of intake runner length 进气管的长度第四章 燃烧与化学 1 physical and chemical properties of petrol and diesel fuels?汽油及柴油的重要理化指标Characteristic of petrol or gasline . 汽油1)Antiknock performance 抗爆性定义：It is used to resists the tendency to produce detonation and this property .表示：The
