清华大学2004级期中考试A卷试题(含答案)

清华大学热能工程系2004级“燃烧学”期中考试试卷（A卷）

考试时间： 2007年5月10日 学号：

Instructions(提示):

1 考试为开卷考试，允许带教科书，作业，课件，笔记本和另外的参考书各一样，但

不能互借，答题必须完成。（The examination is OPEN BOOKS. Calculators, textbook, homework and notebook are allowed, but they can not be lent to others. You should answer the questions independently and help is not allowed）

2 试卷共有8题，你要在120分钟内完成这次考试，先检查一下你的卷子，题目是否对，

共有4页。答案必须写在答题卷上，试题卷上回答无效。答题必须明确，清晰，计算题应给出单位。（There are four questions on this exam. You have up to 120 minutes to work this exam. Please be sure that you have a complete exam package. Please work exam problems on the pages provided. Show your work neatly and write your answers. Give units for all answers requiring them.）

3 如果试卷不对，请立即与监考教师说明。（If a page is missing, take the exam to a

proctor immediately.）

4 强烈推荐你先读一下所有的问题，并对回答问题的时间进行按排。答卷完成后请再

仔细检查一下。（Budget your time for each question and be sure to first answer those questions that you know how to work. Check your work after completing the exam.） 5 请你现在就在答卷纸和试卷纸上写上你的名字与学号，并在你的答卷纸上标明你的

试卷的类型（A或B卷）（PRINT your name NOW in the spaces at the top of your pages.）

6 答卷可以用中文或英文，如果是双语的，以中文为准。试卷有英译的，也以中文为

准。(The answers can be in English or Chinese. If two languages are used in one answer, I will take Chinese as the selection. Some of the problems have been translated in English. If there are any difference between Chinese and English, Chinese is for your choice.) 问题（problems）

1 简要回答下列问题，选择或判断（每题2分， 8题，共16分）（Answer the following

questions briefly）

1.1 CO燃烧的高位热值与低位热值相等，是否如此，说明理由(Is it rue that CO is

used as the fuel, its high value equals lower heat value. Please explain your result.) 1.2 CH4低温氧化燃烧反应会出现C2H6，这说明低温下CH4不容易燃尽，你觉得这

种观点是否正确？（In low temperature oxidation of CH4 there is C2H6 produced. It means that the CH4 can not be burn completely at low temperature, do you agree?）

A1

班级：

姓名：

1.3 基元反应的反应级数一定是整数，而总包反应则一定不是整数。这一说法是否

正确？（the reaction orders are always integers in element reactions. The reaction orders are not integers in global reactions. Do you agree?）

1.4 CO氧化反应的主要控制反应是什么？( Which reaction is the key step in CO

oxidation?)

1.5 有人说，对于完全预混火焰，在空间任何一点的混合分数均匀分布。你认为如

何？(The mixture fraction keeps even in space in well premixed flame. Do you agree?)

1.6 为什么在燃烧中很多方程推导过程中要假设Le=1？( Why do we assume that

Le=1 when you derive the equations in combustion?)

1.7 在局部平衡假设中，表示一个反应的正反应和逆反应速率相等，即意味着参与

这一反应的所有反应物和生成物的浓度也不变。这一说法是否正确？（In partial-equilibrium approximation, we assume that the forward and reverse reaction rates in the reaction are equal. It means that all the concentrations of the reactants and products keep unchanged. Do you think so?）

1.8 一种煤的收到基成分为Mar=38%，Aar=20%，Var=35%，试判断这是什么煤种：

(One kind of coal consists of Mar=38%，Aar=20%，Var=35% as received. Please classify the coal type.)

A．无烟煤(Anthracite) B.烟煤(bituminous coal) C.褐煤(lignite) D. 贫煤(Lean coal)

2 （8分）燃料液滴的燃烧可以认为就是其蒸发过程。设直径为100微米的已烷(C6H14)

油滴在空气中蒸发燃烧，无对流，试计算此液滴燃尽率为90%所用的燃烧时间占总的燃烧时间的百分比。(The combustion of droplets can be defined with the evaporation process. A C6H14 droplet of 100 microns is vaporized and burned in air without convection flow. Find the ratio of the combustion time with 90% of burn out and the total burnout time)

3 （12）现有一个刚性燃烧室，初始条件为2000K，1atm, 含有CO为1%，O2为3%，

其余为N2。假定仅存在反应CO+O2→CO2+O，并且kf=2.5*1025*exp(-47800/RT),其中kf的单位为cm3/(mol·s)，E的单位为cal/mol，试计算CO完全燃烧所需要的时间。( A rigid combustor with 2000K and 1 atm. The CO=1%, O2 is 3% and remained is N2. Only one reaction CO+O2→CO2+O is active and kf=2.5*1025*exp(-47800/RT). The unit of kf is cm3/(mol·s)，and the unit of E is cal/mol). Find the burn out time of CO)

A2

4 （14分）对于下面一组反应 (There are following system of reactios)

1NO2NO3N2O52N2O5NO2NO33NO3O2NO2O342NO32NO2O2kkkk4.1 (6分)写出N2O5、NO2、NO3、O2、O3浓度变化速率的方程;(Write out the express

of the reaction rates of N2O5、NO2、NO3、O2、O3)

4.2 （8分）假定组分NO2和NO3处于稳定状态, 则求出它们的浓度;(If NO2 and NO3

are in steady state find their concentration)

5 （8分） 防火是燃烧研究的一个重要领域，其中一个方法是采用阻燃剂，阻燃剂中

最常用的是采用含溴(Br)的物质，一旦发生火灾，这种物质就会释放出来阻止燃烧的发生和扩展，试给出合理解释。(Fire safty is very important branch of combustion research. One of the methods is to use technician found that it is difficult to ignite the CO flame when the pure Oxygen (21%) and pure nitrogen(79%) are used. It is very easy to ignite the flame when the room air is used. Please explain the phenomenon.)

6

(16分) CO2作为一种温室气体，其控制受到重视，其中人们提出了一种控制方法，就是将空气

进行分离，将分离出来的O2与烟气循环CO2来替代原来的N2来进行燃烧，这种方法称富氧循环燃烧。设采用CH4作为燃料，其反应式可以写为(CO2 is a greenhouse gas. One of the methods to control is to separate the oxygen form air and then recycle the CO2 from the flue gas to mix with O2 to replace the air for combustion. This kind of combustion is called Oxy-fuel combustion. Use CH4 as fuel. The reation can be expressed as )：

CH4+2（O2+3.76CO2）=9.52CO2+2H2O

试分析（Find）：

6.1 (10分)燃料与CO2循环温度为常温定压（25℃，1atm）时的定压理论燃烧温度（产物中

H2O已被分离,只有CO2循环），并与空气燃烧时的结果(2318K)进行比较,并分析产生变化的原因(Estimate the constant-pressure adiabatic flame temperature(H2O in flue gas is separated and CO2 is recycled only. Compare the results with the air combustion conditions and analyze the difference).

6.2 （6分）如果为了维持理论燃烧温度与空气燃烧时一致，你建议如何实现，定作出定量分

析。（If we need to sustain the same combustion temperature as air combustion, what is your suggestion to do? Please give the evaluation of your method） (16分) 下图是一维燃烧波，参考坐标系定在燃烧波上，则该问题可简化为稳态问题。下标1表示燃烧波前的未燃区域，而下标2则表示波后的已燃区域。假设未燃和已燃气体是均匀分布的、过程绝热、反应前后混合物Cp为常数，则质量、动量和能量的守恒方程符合柱塞流反应器，方程积分形式表示为：(The following is a one dimensional wave. We refer the problem with the

A3

7

wave and it is in steady state. Subscript 1 means unburned zone and subscript 2 means burned zone. We assume that the gas are even distributed in unburned gas and burned gas. The process is adiabatic and Cp is constant through out the whole zone and the reaction is plug flow reactor. The integrated equation are)

1u12u2

2 p11u12p22u22CpT11/2u12hcCpT21/2u2(1) (2) (3a)

00或(or) h11/2u1h21/2u2且(and)hch1h27.1

22(3b)

7.2

7.3

方程1-3完全符合柱塞流反应器(Plug-flow reactor)的假设，请写出式1、2、3b对应的柱塞流反应器的微分形式，并说出柱塞流反应器的特点；(6分)(The assumptions of the plug-flow reactor are followed in Equation 1-3. and write the differential equation of 1、2 and 3b. Please refer the features of the plug-flow reactor)

假设所有组分比热相同且不随温度变化，请写出基于Shvab-Zeldovich原理的守恒标量能量方程(Conserved Scalar Energy Equation)，比较该方程和式（3b）对应能量方程微分形式的异同点；(5分)(All the Cps of species are equal and keep same with temperature. Write the Conserved Scalar Energy Equation of Shvab-Zeldovich principle. Compare the result.) 根据方程1、2、3a，试证明Rankine-Hugoniot曲线 (5分)(Prove the Rankine-Hugoniot curve with equation1,2 and 3a)

11p2p11(pp)hc211212218

(10分)在一维平面坐标系下，分别列出完全理想柱塞流反应器的组分守恒方程和基于二元扩散

的简化组分守恒方程的表达式，并比较二者的区别。注意：所写表达式的参量只能是

Yi、、vx、i、MWi，也就是质量通量和质量生成率都要化简到最后形式。(Write and

compare the species conservation equations and its simplified expression based on binary diffusion in a complete and ideal plug-flow reactor. Note:the only parameters used are

Yi、、vx、i、MWi)

A4