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1、The Application of Turbomachinery to Reciprocating Engines 涡轮机械在往复式发动机上的应用Chapter 6 第6章 Matching 4-Stroke Diesels与四冲程柴油机匹配Volumetric Efficiency 容积效率The volumetric efficiency is defined as; 充气效率的定义如下where: D= Displacement per cycle length3/cycle 一个工作循环的排量长度3/循环次数 N= Engine speed rev/time 发动机转速转/分 NRP
2、C = Number of revolutions per cycle 2 for a four-stroke engine每循环活塞往复运动次数二或四冲程where:vol= Volumetric Efficiency dimensionless容积效率无量纲 min= Net mass flow rate into engine cylinders mass/time进入气缸的净质量流量质量/时间 ref= Reference density mass/length3参考密度质量/长度3 VDR= Volumetric displacement rate length3/time单位时间体
3、积排量长度3/时间The volumetric displacement rate is calculated by;单位时间体积排量按下面的公式计算.volinref= actual air mass flow ideal air mass flow= m *VDR VDR = D*N NRPC Volumetric Efficiency (continued) 容积效率The reference density is calculated from the ideal gas law (P*v = m*R*T); 参考密度按照理想气体状态方程计算where: R= Gas constant
4、 for air (length*force)/(mass*temperature)空气气体常数 Pref= Reference pressure mass/length2 (Ref conditions in the inlet manifold)参考压力（在进气管状态下） Tref= Reference temperature temperature 参考温度 Substituting these relationships into the definition of volumetric efficiency gives; 把这些参数带入上述充气效率公式中则有:or, solving
5、for min gives:或者，求解min. =refrefin volPNDTmNRPCR =refrefvol inTNRPCRPNDm =refref refTRPBreathing Lines (Four-Stroke Diesel Engine Only)Given the equation derived from the definition of Volumetric Efficiency;由容积效率定义得出方程式:Make the following assumptions/approximations;做下面的假设/近似值 vol= a constant (somewhe
6、re between .88 and .95) 常量(0.88到0.95之间) Pref= Pamb * (Compressor Pressure Ratio) = Pamb*PRc压气机压缩比 Tref= a constant (for an aftercooled engine)常量(对中冷发动机) D= a constant (for a given engine)常量(对指定的发动机)Substituting these relationships into the equation above gives;把这些参数代如上方程式有:Converting this to the Mas
7、s Flow Parameter used in the compressor map gives: =refrefvol inTNRPCRPNDm.cinPRTNConstantMFP=()ambinincambininin PPTPRPNConstant PTmMFP=.cambinPRPNConstantm=吸气线(四冲程发动机才有)转换成压气机特性曲线上的质量流量参数MFPBreathing lines in compressor map coordinates0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21
8、.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpm1300 rpm压气机特性曲线坐标中的吸气线流量参数压 缩 比Breathing Lines on a Compressor Map0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpm1300 rpm压气机特性曲线图上的吸气线压 缩 比流量参数Compressor map too sm
9、all 压气机特性曲线图太小0255075100125150175200Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpm1300 rpm流量参数压 缩 比Compressor map too large 压气机特性曲线图太大0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ra
10、tio1900 rpm1300 rpm压 缩 比流量参数Compressor map too narrow 压气机性能曲线图太窄0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio2100 rpm1100 rpm流量参数压 缩 比压 缩 比压气机性能曲线上的工作点工作点的估算功率燃油消耗率 空燃比燃油流量(速) 空气流量(速)质量流量参数知道了MFP， 和已有的吸气 线，就可得出 压缩比PRc流量参数Operating
11、 Point on a Compressor Map0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpmEstimation of Operating PointPower = x kW BSFC = y g/kWhAir/Fuel ratio = zFuel flow rate = x * yAir flow rate = Fuel * zMFP = Fuel*z *Hence PRc from MF
12、P and breathing linesqrt(Tin)/PinEffect of Turbine Selection on Compressor Operation0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpm“Larger“ Casing “Smaller“ Casing涡壳的选择对压气机特性曲线上工作点的影响流量参数压 缩 比大的涡壳小的涡壳02550751001.01.41.82.22.
13、63.03.43.8Flow Parameter kg/s * sqrt(K)/MPa494136Speed Parameter As the turbo speed increases the flow size of the turbine decreases slightly Turbine swallowing capacity curvesWith a smaller turbine housing the expansion ratio and hence turbine power rises涡壳通流能力曲线流量参数速度参数 小的涡壳，小的 涡壳，可提高膨 胀比和涡轮功率增压器转
14、 速增大的 同时，涡 轮流量减 小Flow Parameter kg/s - sqrt(K)/MPa01020304050 Speed Parameter rev/s * 1/sqrt(K)0.010.020.030.040.050.060.070.080.01.301.501.802.202.803.5074% 72%70%64% 56%74%72%70%64%56%Operation within the turbine map速度参数流量参数在涡轮性能曲线图内运行0255075100125150175200 Flow Parameter kg/s * sqrt(K)/MPa1.01.21
15、.41.61.82.02.22.42.62.83.03.23.43.63.8Pressure Ratio1900 rpm1300 rpmABConsider the engine moving from 1300 to 1900 rpm at constant boost pressureComp mass flow and turbo speed increaseAt the turbine, expansion ratio will increaseTorque curve characteristics 扭矩曲线特性压比流量参数发动机在 压比不变 时，转速 从1300上 升到1900压气机质 量流量和 增压器转 速升高涡端膨胀 比增大 00.40.81.21.62.02.400.010.020.030.040.050.06 Fuel-air ratio 燃空比Engine Temp. rise(Tem-Tim) over inlet temp(Tim) - (absolute)Lines are Diamond Engine: AJEPATL Points 4692-4906 Motoring data from NT engine in brake test cell Symbols are N14 A95NE3_P5 at 1800,120
