推进理论课的一次热力计算作业,还是挺有趣的,可以作为简单的案例参考。主要难点在于利用平衡常数法计算平衡组分,使用的方程、设计的计算链顺序对结果有重要的影响。物性参数主要参考北航的教材《固体火箭发动机原理》,如果需要找其他组分的参数也可以上NASA的网站查询。

工作条件和计算参数

p1_工作条件和计算参数.png
p1_工作条件和计算参数.png

燃烧室的热力计算

计算固体推进剂的假定化学式

每千克中各元素物质的量为

\[ \begin{aligned} n_C &=\frac{1000\times20.5\%\times35.89\%}{12}+\frac{1000\times4.0\%}{104}\times8+\frac{1000\times1.5\%\times72.94\%}{12} &=10.12\ mol/kg \\ n_H &=\frac{1000\times74.0\%}{117.5}\times4+\frac{1000\times20.5\%\times6.10\%}{1}+\frac{1000\times4.0\%}{104}\times8+\frac{1000\times1.5\%\times7.03\%}{1} &=41.83\ mol/kg \\ n_O &=\frac{1000\times74.0\%}{117.5}\times4+\frac{1000\times20.5\%\times20.28\%}{16}+\frac{1000\times1.5\%\times20.04\%}{16} &=27.98\ mol/kg \\ n_N &=\frac{1000\times74.0\%}{117.5}\times1 &=6.30\ mol/kg \\ n_S &=\frac{1000\times20.5\%\times37.74\%}{32} &=2.42\ mol/kg \\ n_{Cl} &=\frac{1000\times74.0\%}{117.5}\times1 &=6.30\ mol/kg \\ \end{aligned} \]

假定化学式为\(C_{10.12}H_{41.83}O_{27.98}N_{6.30}S_{2.42}Cl_{6.30}\)

计算推进剂总焓

推进剂初温为\(298K\),以该温度为参考温度的生成焓即该温度下的总焓。

\[ \begin{aligned} & H_{f,1}^{298}=-290.37,\quad H_{f,2}^{298}=1060.23,\quad H_{f,3}^{298}=103.34,\quad H_{f,4}^{298}=-1435.11 &(kJ/mol) \\ & n_1=6.298,\quad n_2=0.205,\quad, n_3=0.3846,\quad n_4=0.015 &(mol/kg推进剂) \\ & I_p=\sum{n_iI_i}=\sum{n_iH_{f,i}^{298}}=-1593.19 &(kJ/kg推进剂) \\ \end{aligned} \]

燃烧室热力计算分析

推进剂含有的元素共6种:\(C,H,O,N,S,Cl\)

假设燃烧产物共有12种,其中主要组分:\(CO,CO_2,H_2,H_2O,N_2\),次要组分:\(H,O_2,OH,NO,Cl,HCl,SO_2\)

推进剂所含元素与燃烧产物、中间产物之间的关系为

\[ \begin{aligned} C &\rightarrow CO_2,CO \\ H &\rightarrow H_2O,H_2,HCl,OH,H \\ O &\rightarrow CO_2,CO,H_2O,OH,SO_2,O_2,O,NO \\ N &\rightarrow N_2,NO,N \\ Cl &\rightarrow HCl,Cl \\ S &\rightarrow SO_2 \\ \end{aligned} \]

对于每种元素列出共6个质量守恒方程

\[ \begin{aligned} 10.12\ mol/kg=N_C &=n_{CO_2}+n_{CO} \\ 41.83\ mol/kg=N_H &=2n_{H_2O}+2n_{H_2}+n_{HCl}+n_{OH}+n_H \\ 27.98\ mol/kg=N_O &=2n_{CO_2}+n_{CO}+n_{H_2O}+n_{OH}+2n_{SO_2}+2n_{O_2}+n_{NO} \\ 6.30\ mol/kg=N_N &=2n_{N_2}+n_{NO} \\ 6.30\ mol/kg=N_{Cl} &=n_{HCl}+n_{Cl} \\ 2.42\ mol/kg=N_S &=n_{SO_2} \\ \end{aligned} \]

列出可能的6个化学平衡方程

\[ \begin{aligned} & CO_2\leftrightharpoons CO+\frac{1}{2}O_2,& K_{p,CO_2}(\frac{p}{n_g})^{-\frac{1}{2}} &=\frac{n_{CO}n_{O_2}^{\frac{1}{2}}}{n_{CO_2}} \\ & CO_2+H_2\leftrightharpoons CO+H_2O, & K_{p,act} &=\frac{n_{CO}n_{H_2O}}{n_{CO_2}n_{H_2}}\quad(act) \\ & H_2O\leftrightharpoons OH+\frac{1}{2}H_2, & K_{p,H_2O(b)}(\frac{p}{n_g})^{-\frac{1}{2}} &=\frac{n_{OH}n_{H_2}^{\frac{1}{2}}}{n_{H_2O}} \\ & N_2+O_2\leftrightharpoons2NO, & K_{p,NO} &=\frac{n_{NO}^2}{n_{N_2}n_{O_2}} \\ & H_2\leftrightharpoons2H, & K_{p,H_2}(\frac{p}{n_g})^{-1} &=\frac{n_H^2}{n_{H_2}} \\ & HCl\leftrightharpoons H+Cl, & K_{p,HCl}(\frac{p}{n_g})^{-1} &=\frac{n_Hn_{Cl}}{n_{HCl}} \\ \end{aligned} \]

建立计算时所用的化学平衡常数数据库

参考北京航空航天大学的《固体火箭发动机原理》,导入需要的化学平衡常数数据。

为了方便使用,写作matlab矩阵和函数的形式。

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function kp_out = kp(comp, temp)
% comp in 2~10, temp in 300~5999

K = [%1 T 2 co2 3 h2oa 4 act 5 h2ob 6 no 7 h2 8 o2 9 n2 10 hcl
%注:部分数据没有用到
[300 0.1825e-44 0.1637e-30 0.1115e-4 0.5140e-40 0.6635e-30 0.1813e-70 0.8191e-80 0.216e-118 5.0582e-71],
[400 0.3895e-32 0.5759e-20 0.6764e-8 0.1237e-33 0.4898e-22 0.1811e-51 0.3084e-58 0.3395e-87 3.3305e-51],
[500 0.9886e-25 0.1302e-22 0.7593e-2 0.3518e-25 0.2587e-17 0.4899e-40 0.2944e-45 0.1879e-68 7.0437e-41],

[600 0.8624e-20 0.2333e-18 0.3695e-1 0.3400e-21 0.3648e-14 0.2153e-32 0.1387e-35 0.6218e-55 2.2558e-33],
[700 0.2900e-16 0.2614e-15 0.1109 0.1265e-17 0.6489e-12 0.6425e-27 0.2240e-30 0.5633e-47 7.1318e-28],
[800 0.1277e-13 0.5156e-13 0.2475 0.6119e-15 0.3163e-10 0.8426e-23 0.1084e-25 0.3010e-40 8.6636e-24],
[900 0.1445e-11 0.3185e-11 0.4537 0.7568e-13 0.6495e-9 0.1369e-19 0.4450e-22 0.5230e-35 1.3301e-20],
[1000 0.6331e-10 0.8728e-10 0.7254 0.3604e-11 0.7302e-8 0.5148e-17 0.3651e-19 0.8239e-31 4.7852e-18],

[1100 0.1389e-8 0.1314e-8 1.0560 0.8519e-10 0.5277e-7 0.6676e-15 0.8820e-17 0.2262e-27 5.9776e-16],
[1200 0.1814e-7 0.1267e-7 1.4320 0.1198e-8 0.2752e-6 0.3886e-18 0.8630e-15 0.1673e-24 3.3731e-14],
[1300 0.1591e-6 0.8648e-7 1.8400 0.1116e-7 0.1112e-5 0.1220e-11 0.4191e-13 0.4503e-22 1.0313e-12],
[1400 0.1020e-5 0.4501e-6 2.2660 0.7603e-7 0.3680e-5 0.2358e-10 0.1178e-11 0.5478e-20 1.9467e-11],
[1500 0.5087e-5 0.1885e-5 2.6990 0.4016e-6 0.1039e-4 0.3087e-9 0.2118e-10 0.3527e-18 2.4963e-10],

[1600 0.2074e-4 0.6615e-5 3.1350 0.1726e-5 0.2575e-4 0.2944e-8 0.2657e-9 0.1357e-16 2.3911e-9 ],
[1700 0.7131e-4 0.2005e-4 3.5550 0.6250e-5 0.5738e-4 0.2162e-7 0.2486e-8 0.3393e-15 1.6878e-8 ],
[1800 0.2135e-3 0.5388e-4 3.9670 0.1964e-4 0.1170e-3 0.1277e-6 0.1819e-7 0.5961e-14 9.8107e-8 ],
[1900 0.5687e-3 0.1303e-3 4.3630 0.5475e-4 0.2213e-3 0.6267e-6 0.1080e-6 0.7761e-13 4.7512e-7 ],
[2000 0.1871e-2 0.2892e-3 4.7410 0.1378e-3 0.3926e-3 0.2631e-5 0.5376e-6 0.7829e-12 1.9697e-6 ],

[2100 0.3035e-2 0.5954e-3 5.0970 0.3178e-3 0.6595e-3 0.9658e-5 0.2299e-5 0.6349e-11 7.1433e-6 ],
[2200 0.6240e-2 0.1149e-2 5.4300 0.6797e-3 0.1057e-2 0.3155e-4 0.8624e-5 0.4263e-10 2.3083e-5 ],
[2300 0.1208e-1 0.2094e-2 5.7460 0.1361e-2 0.1625e-2 0.9313e-4 0.2885e-4 0.2429e-9 6.7468e-5 ],
[2400 0.2195e-1 0.3634e-2 6.0390 0.2573e-2 0.2410e-2 0.2516e-3 0.6738e-4 0.1198e-8 1.8055e-4 ],
[2500 0.3810e-1 0.6037e-2 6.3110 0.4625e-2 0.3391e-2 0.6284e-3 0.2423e-3 0.5206e-8 4.4720e-4 ],

[2600 0.6333e-1 0.9649e-2 6.5630 0.7947e-2 0.4840e-2 0.1464e-2 0.6215e-3 0.2023e-7 1.0335e-3 ],
[2700 0.1013 0.1490e-1 6.7940 0.1312e-1 0.6592e-2 0.3207e-2 0.1487e-2 0.7114e-7 2.2470e-3 ],
[2800 0.1565 0.2233e-1 7.0080 0.2081e-1 0.8786e-2 0.6649e-2 0.3345e-2 0.2289e-6 4.5983e-3 ],
[2900 0.2345 0.3256e-1 7.2020 0.3228e-1 0.1146e-1 0.1312e-1 0.7117e-2 0.5797e-6 9.0698e-3 ],
[3000 0.3417 0.4628e-1 7.3820 0.4841e-1 0.1472e-1 0.2475e-1 0.1441e-1 0.1879e-5 1.7070e-2 ],

[3100 0.4854 0.6436e-1 7.5430 0.7074e-1 0.1858e-1 0.4485e-1 0.2786e-1 0.4866e-5 3.0648e-2 ],
[3200 0.6744 0.8770e-1 7.6900 0.1009 0.2310e-1 0.7836e-1 0.5174e-1 0.1189e-4 5.3620e-2 ],
[3300 0.9179 0.1173 7.8210 0.1410 0.2833e-1 0.1324 0.9253e-1 0.2751e-4 8.9557e-2 ],
[3400 1.2260 0.1544 7.9410 0.1933 0.3431e-1 0.2170 0.1600 0.6054e-4 1.4612e-1 ],
[3500 1.6100 0.2000 8.0480 0.2601 0.4115e-1 0.3459 0.2680 0.1278e-3 2.3195e-1 ],

[3600 2.0810 0.2556 8.1430 0.3444 0.4882e-1 0.5374 0.4364 0.2587e-3 0.3585 ],
[3700 2.6520 0.3222 8.2280 0.4492 0.5736e-1 0.8156 0.6926 0.5042e-3 0.5428 ],
[3800 3.3340 0.4017 8.2990 0.5780 0.6677e-1 1.2120 1.0730 0.9491e-3 0.8219 ],
[3900 4.1410 0.4951 8.3640 0.7343 0.7720e-1 1.7630 1.6240 0.1731e-2 1.1655 ],
[4000 5.0870 0.6042 8.4180 0.9217 0.8851e-1 2.5190 2.4080 0.3063e-2 1.6630 ],

[4100 6.1810 0.7303 8.4650 1.1450 0.1008 3.5380 3.5050 0.5276e-2 2.3254 ],
[4200 7.4420 0.8750 8.5060 1.4070 0.1141 4.8890 5.0100 0.8857e-2 3.2063 ],
[4300 8.8740 1.0400 8.5310 1.7130 0.1283 6.6580 7.0460 0.1452e-1 4.3562 ],
[4400 10.5000 1.2280 8.5570 2.0670 0.1436 8.9390 9.7540 0.2330e-1 5.8385 ],
[4500 12.5300 1.4370 8.5760 2.4750 0.1598 11.8500 13.3100 0.3660e-1 7.7233 ],

[4600 14.3600 1.6730 8.5860 2.9400 0.1770 15.5200 17.9300 0.5641e-1 10.0970 ],
[4700 16.5200 1.9340 8.5920 3.4660 0.1952 20.0800 23.8300 0.8541e-1 13.0530 ],
[4800 19.1100 2.2240 8.5920 4.0610 0.2143 25.7200 31.3200 0.1271 16.6850 ],
[4900 21.8400 2.5430 8.5880 4.7290 0.2343 32.6200 40.7000 0.1863 21.14450 ],
[5000 24.8300 2.8940 8.5780 5.4730 0.2553 40.9900 52.3400 0.2689 26.5340 ],

[5100 28.0600 3.2760 8.5670 6.2980 0.2771 51.0100 66.6500 0.3828 33.0700 ],
[5200 31.5800 3.6940 8.5490 7.2090 0.2997 62.9800 84.1000 0.5379 40.7200 ],
[5300 35.3700 4.1460 8.5310 8.2130 0.3234 77.1400 105.2000 0.7464 49.8430 ],
[5400 39.4100 4.6340 8.5040 9.3110 0.3478 93.7800 130.5000 1.0230 60.5660 ],
[5500 43.7500 5.1600 8.4780 10.5100 0.3731 113.2000 160.6000 1.3890 73.0810 ],

[5600 48.3700 5.7270 8.4450 11.8100 0.3988 135.7000 196.3000 1.8640 87.6000 ],
[5700 53.2700 6.3330 8.4120 13.2300 0.4258 161.7000 238.1000 2.4750 104.3566 ],
[5800 58.4800 6.9810 8.3770 14.7600 0.4533 191.5000 287.0000 3.2610 123.5633 ],
[5900 63.9600 7.6700 8.3390 16.4000 0.4812 225.5000 343.8000 4.2560 145.5170 ],
[6000 69.7400 8.4050 8.2990 18.1800 0.5100 264.0000 409.4000 5.5080 170.4113 ],
];

cnt = floor(temp/100)-2;
kp_out = K(cnt, comp) + (temp-(cnt+2)*100) * ((K(cnt+1, comp)-K(cnt, comp))/100);

end

计算给定压强和温度下燃烧产物的平衡组分和焓

平衡组分计算

将2.3中的方程转化。用迭代法进行计算。

计算链设计

先将次要组分\(H,O_2,OH,NO,Cl\)视为零,根据线性方程,先计算简单的几个。

\[ \begin{aligned} n_{SO_2} &=N_S &(1)\\ n_{HCl} &=N_{Cl}-n_{Cl} &(2) \\ n_{N_2} &=\frac{1}{2}(N_N-n_{NO}) &(3) \\ \end{aligned} \]

接下来还有主要组分\(CO,CO_2,H_2,H_2O\)需要计算,

相关元素\(C,O,H\)只有三个线性方程(质量守恒),不过再加上水煤气反应方程式\((act)\)就有四个方程,可以求解了。 \[ \begin{aligned} n_{CO} &= N_C-n_{CO_2} &(4) \\ n_{H_2O} &= N_O-n_{CO_2}-N_C-n_{OH}-2n_{SO_2}-2n_{O_2}-n_{NO} &(5) \\ n_{H_2} &= \frac{1}{2}(N_H-n_{HCl}-n_{OH}-n_H)-(N_O-n_{CO_2}-N_C-n_{OH}-2n_{SO_2}-2n_{O_2}-n_{NO}) &(6) \\ K_{p,act}n_{CO_2}n_{H_2} &= n_{CO}n_{H_2O} &(7) \\ \end{aligned} \] 具体来说,先把式(4)(5)(6)代入(7)求出\(n_{CO_2}\),再代回求解\(n_{CO},n_{H_2O},n_{H_2}\)

那么现在,已经获得了主要组分\(n_{CO},n_{CO_2},n_{H_2},n_{H_2O},n_{N_2}\)和次要组分中的\(n_{HCl},n_{SO2}\),可以反过来计算之前被视为零的量。 \[ \begin{aligned} n_g &= \sum{n_i} \\ n_H &=\left[K_{p,H_2}\left(\frac{p}{n_g}\right)^{-1}n_{H_2}\right]^{\frac{1}{2}} &(8) \\ n_{O_2} &=\left[K_{p,CO_2}\left(\frac{p}{n_g}\right)^{-\frac{1}{2}}n_{CO_2}n_{CO}^{-1}\right]^2 &(9) \\ n_{OH} &=K_{p,H_2O(b)}\left(\frac{p}{n_g}\right)^{-\frac{1}{2}}n_{H_2O}n_{H_2}^{-\frac{1}{2}} &(10) \\ n_{NO} &=\left[K_{p,NO}n_{N_2}n_{O_2}\right]^{\frac{1}{2}} &(11) \\ n_{Cl} &=K_{p,HCl}(\frac{p}{n_g})^{-1}n_{HCl}n_H^{-1} &(12) \\ \end{aligned} \] 迭代计算,直到收敛。

平衡组分计算程序

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function N = cal_n(t, p)

NC=10.12;NH=41.83;NO=27.98;NN=6.30;NS=2.42;NCL=6.30;
h=0;o2=0;oh=0;no=0;cl=0;

steps = 0;
while steps < 50
steps = steps+1;

so2 = NS;
hcl = NCL-cl;
n2 = 1/2*(NN-no);

syms co2;
co2 = solve(kp(4,t)*co2*(1/2*(NH-hcl-oh-h)-(NO-co2-NC-oh-2*so2-2*o2-no))==(NC-co2)*(NO-co2-NC-oh-2*so2-2*o2-no), co2);
co2 = vpa(co2(co2>0),7);
co = NC-co2;
h2o = NO-co2-NC-oh-2*so2-2*o2-no;
h2 = 1/2*(NH-hcl-oh-h)-h2o;

h_old=h;o2_old=o2;oh_old=oh;no_old=no;cl_old=cl;
ng = co+co2+h2+h2o+n2+h+o2+oh+no+cl+hcl+so2;
w = p/ng;
h = (kp(7,t)*w^(-1)*h2)^(1/2);
o2 = (kp(2,t)*w^(-1/2)*co2*co^(-1))^2;
oh = kp(5,t)*w^(-1/2)*h2o*h2^(-1/2);
no = (kp(6,t)*n2*o2)^(1/2);
cl = kp(10,t)*w^(-1)*hcl*h^(-1);

delta = sqrt(abs((h_old-h)/h_old)^2+abs((o2_old-o2)/o2_old)^2+abs((oh_old-oh)/oh_old)^2+abs((no_old-no)/no_old)^2+abs((cl_old-cl)/cl_old)^2);
if delta < 0.001
break;
end
end

% fprintf("end, steps=%d, delta=%f\n", steps, delta);
% 1 2 3 4 5 6 7 8 9 10 11 12 13
N=[ co co2 h2 h2o n2 h o2 oh no cl hcl so2 ng];

end

燃烧产物焓的计算

同样,预先准备可能用到的物质在一定范围内的总焓。

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function ic_out = ic(comp, temp)
%temp in 2600~3000
%cal/mol
I = [%co co2 h2 h2o n2 h o2 oh no cl hcl so2 T
[-7573.2 -63292.4 17743.5 -33030.3 18675.1 63542.0 19698.4 28044.5 40776.8 41042.1 -3718.4 -40741.8 2600],
[-6689.5 -61803.2 18609.5 -31762.6 19554.5 64038.3 20636.4 28913.1 41669.1 41547.1 -2840.5 -39328.2 2700],
[-5803.9 -60309.3 19481.3 -30487.6 20436.0 64535.6 21579.4 29786.4 42563.2 42051.6 -1959.3 -37932.0 2800],
[-4916.6 -58811.1 20358.9 -29285.7 21319.5 65032.4 22527.3 30664.0 43458.9 12555.6 -1074.9 -36493.3 2900],
[-4027.6 -57308.8 21242.1 -27917.4 22204.7 65529.2 23480.0 31545.8 44356.3 43059.2 -187.8 -35072.1 3000],

[-3136.0 -55802.6 22130.6 -26623.4 23091.6 66026.0 24437.3 32431.6 45255.1 43562.4 702.1 -33648.6 3100],
[-2244.0 -54292.7 23024.4 -25324.1 23980.2 66522.8 25399.1 33321.1 46155.4 44065.2 1594.5 -32222.7 3200],
[-1350.7 -52779.2 23923.3 -24020.0 24870.2 67019.6 26365.2 34214.2 47057.1 44567.9 2489.4 -30794.6 3300],
[-456.2 -51262.4 24827.2 -22711.4 25761.6 67516.4 27335.5 35110.7 47960.2 45069.9 3386.6 -29364.5 3400],
[439.6 -49742.4 25736.0 -21396.7 26654.3 68013.2 28309.7 36010.6 48864.5 45571.9 4286.0 -27932.2 3500],
];

cnt = floor(temp/100)-25;
ic_out = I(cnt, comp) + (temp-(cnt+25)*100) * ((I(cnt+1, comp)-I(cnt, comp))/100);
ic_out = ic_out*4.184;

end

每千克推进剂产生的燃烧产物的总焓计算方法为\(I_c=\sum{n_iI_i}\)

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function sum_ic = cal_ic(t, p)

N = cal_n(t, p);
sum_ic = 0;
for i = 1:12
sum_ic = sum_ic + N(i) * ic(i, t);
end

end

绝热燃烧温度的计算

用上述程序计算压强\(50.66e5\ Pa\)\(T_{f1}=2600\ K\)\(T_{f2}=3499\ K\)时的燃烧产物总焓分别为\(-2073.66\ kJ/kg推进剂,-476.49\ kJ/kg推进剂\),那么显然绝热燃烧温度\(T_f\)在它们之间,可以线性插值计算得出结果。

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function out_tf = cal_tf(p)

t1 = 2600;t2 = 3499;
ip = -1593190;

i1 = cal_ic(t1, p);
i2 = cal_ic(t2, p);
out_tf = t1+(ip-i1)/(i2-i1)*(t2-t1);

end

\[ T_f=T_{f1}+\frac{I_p-I_{c1}}{I_{c2}-I_{c1}}(T_{f2}-T_{f1})=2870.44\ K \] 进行验证,得\(50.66e5\ Pa,2870.44\ K\)\(I_c=-1600.83\ kJ/kg推进剂\approx I_p\)成立。

绝热燃烧温度下燃烧产物的性质分析

燃烧产物的平衡组分

将压强和温度\(T_f\)代入前面的平衡常数法的燃烧产物组分计算程序,得此时组分为。(\(mol/kg推进剂\)

\(CO\) \(CO_2\) \(H_2\) \(H_2O\) \(N_2\) \(H\) \(O_2\) \(OH\) \(NO\) \(Cl\) \(HCl\) \(SO_2\) \(n_g\)
8.205 1.915 6.660 11.105 3.150 7.65e-4 1.91e-8 3.48e-4 2.53e-5 5e-4 6.299 2.42 39.756

燃烧产物的热力学性质

\(T_f=2870.44\ K\)时,各组分定压比热容为

\(c_{pi}\) \(CO\) \(CO_2\) \(H_2\) \(H_2O\) \(N_2\) \(H\) \(O_2\) \(OH\) \(NO\) \(Cl\) \(HCl\) \(SO_2\)
\(J\cdot K^{-1}\cdot mol^{-1}\) 37.14 62.72 36.77 53.69 36.98 20.79 39.70 36.76 37.49 21.08 37.03 59.38

燃烧室出口处,燃烧产物的平均比热为 \[ \begin{aligned} c_p &=\sum_{i=1}^{m}{x_ic_{pi}}=44.26\quad J\cdot K^{-1}\cdot mol^{-1} \\ c_v &=c_p-R_0=35.946\quad J\cdot K^{-1}\cdot mol^{-1} \\ k &= \frac{c_p}{c_v}=1.23 \\ \end{aligned} \] 平均摩尔质量为 \[ \bar{\mu}_g=\frac{1000}{n_g}=25.153\quad g/mol \] 平均气体常数为 \[ \bar{R}_g=\frac{R_0}{\bar{\mu}_g}=330.54\quad J\cdot kg^{-1}\cdot K^{-1} \]

燃烧室出口处的理论特征速度

\[ \begin{aligned} \Gamma &=\sqrt{k}\left(\frac{2}{k+1}\right)^{\frac{k+1}{2(k-1)}}=0.6543 \\ C_D &=\frac{\Gamma}{\sqrt{RT_c}}=6.717\times10^{-4}\quad s/m \\ c^* &=\frac{1}{C_D}=1488.72\quad m/s\\ \end{aligned} \]

喷管流动过程热力计算

喷管流动过程分析

由于出口处压强为\(1.0132e5\ Pa\),根据空气动力学可以进行流动过程分析 \[ \begin{aligned} \frac{p_e}{p_c} &=\pi(\lambda)=\left(1-\frac{k-1}{k+1}\lambda^2\right)^{\frac{k}{k-1}} \\ \Rightarrow \lambda &=2.2428,\quad M=3.062 \\ T_e &=T_c\tau(\lambda)=1381.19\quad K \\ \end{aligned} \] 可见,喷管出口处为超声速。

喷管出口截面处燃烧产物的平衡组分

用上面的平衡组分计算程序,得在出口截面处,组分为

\(CO\) \(CO_2\) \(H_2\) \(H_2O\) \(N_2\) \(H\) \(O_2\) \(OH\) \(NO\) \(Cl\) \(HCl\) \(SO_2\) \(n_g\)
6.621 3.497 8.244 9.521 3.150 0 0 0 0 0 6.300 2.420 39.755

喷管出口截面处燃烧产物的热力学性质

\(T_e=1381.19\ K\)时,各组分定压比热容为

\(c_{pi}\) \(CO\) \(CO_2\) \(H_2\) \(H_2O\) \(N_2\) \(H\) \(O_2\) \(OH\) \(NO\) \(Cl\) \(HCl\) \(SO_2\)
\(J\cdot K^{-1}\cdot mol^{-1}\) 34.87 57.79 31.78 45.45 34.46 20.79 36.24 32.43 35.50 21.76 33.58 56.61

与上面同理,可计算出此时气流的平均热力性质参数

\(c_p\) \(39.86\ J\cdot K^{-1}\cdot mol^{-1}\)
\(c_v\) \(31.546\ J\cdot K^{-1}\cdot mol^{-1}\)
\(k\) \(1.26\)
\(\bar{\mu}_g\) \(25.154\ g/mol\)
\(\bar{R}_g\) \(330.524\ J\cdot kg^{-1}\cdot K^{-1}\)
\(\Gamma\) \(0.660\)
\(C_D\) \(6.775\times10^{-4}\)
\(c^*\) \(1475.97\)

比热比\(k\)误差较大,其他参数与燃烧室出口处基本相同。

查表计算总焓,得\(I_{m,e}=-4157.36\ kJ/kg推进剂\)

发动机理论性能参数计算

发动机理论比冲计算

\[ \begin{aligned} u_e &=\sqrt{2(I_{m,c}-I_{m,e})}=2264.58\quad m/s \\ I_{sp} &=\left[u_e+\frac{A_e}{\dot{m}}(p_e-p_a)\right]/g=226.458\quad s \\ \end{aligned} \]

发动机理论推力系数计算

\[ C_F=\frac{I_{sp}}{c^*}=1.534 \]