汽车理论课后题目答案

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1、汽车理论大作业1.3、确定一轻型货车的动力性能（货车可装用4档或5档变速器，任选其中的一种进行整车性能计算）：1）绘制汽车驱动力与行驶阻力平衡图。2）求汽车的最高车速、最大爬坡度及克服该坡度时相应的附着率。3）绘制汽车行驶加速倒数曲线，用图解积分法求汽车有档起步加速行驶至70km/h的车速时间曲线，或者用计算机求汽车用档起步加速至70km/h的加速时间。 轻型货车的有关数据：汽油发动机使用外特性的Tqn曲线的拟合公式为 式中, Tq为发功机转矩(Nm)；n为发动机转速(rmin)。 发动机的最低转速nmin=600r/min ，最高转速nmax=4000 rmin 装载质量 2000kg 整车

2、整备质量 1800kg 总质量 3880 kg 车轮半径 0.367 m 传动系机械效率 0.85 波动阻力系数 f0.013 空气阻力系数迎风面积 CDA2.77 主减速器传动比 i05.83 飞轮转功惯量 If0.218kg 二前轮转动惯量 Iw11.798kg 四后轮转功惯量 Iw23.598kg变速器传动比 ig(数据如下表) 轴距L3.2m 质心至前铀距离(满载)1.947m质心高(满载)hg0.9m解答： 1）（取五档为例） 计算公式： 即 行驶阻力为： 2，原始数据=5.83、T =0.85、r=0.367m、CDA=2.77m2、G=38809.8=38024N、=0.013；

3、 3、计算结果ig=5.56n(r/min)Ua1(km/h)ft1(N)ig=2.769n(r/min)Ua2(km/h)ft2(N)6002.5610348004.5986005.1424153986.46210004.2683911077.0810008.5706925516.62317007.25626313005.17170014.570186476.85623009.81729613090.06230019.712596519.135278011.8661212875.55278023.826526412.3323013.786912561.34323027.683346255.8

4、21364015.5369412000.03364031.197325976.273400017.0735610996.33400034.282775476.411ig=1.644n(r/min)Ua3(km/h)ft3(N)ig=1.00n(r/min)Ua4(km/h)ft4(N)6008.6614042366.82760014.239351439.676100014.435673275.308100023.732251992.28170024.540643845.414170040.344822339.06230033.202053870.515230054.584172354.3282

5、78040.131173807.086278065.975652315.746323046.627223714.182323076.655162259.235364052.545853548.209364086.385382158.278400057.742693251.434400094.928991977.758ig=0.793n(r/min)Ua5(km/h)ft5(N)60017.95631141.663100029.927171579.878170050.876191854.874230068.832491866.982278083.197541836.386323096.66476

6、1791.5733640108.93491711.5154000119.70871568.362ig=0.793Ua5(km/h)Ff5Fw5Fw5+Ff50494.3120494.31210494.31213.09693507.408914494.31225.66998519.98217.9563494.31242.22827536.540329.92717494.312117.3007611.612750.87619494.312338.9991833.311168.83249494.312620.52091114.83383.19754494.312906.5471400.85996.6

7、6476494.3121223.7871718.099108.9349494.3121554.1882048.5119.7087494.3121876.8122371.1244、由数据做出图 2）最高车速： 有 分别代入和公式： 把的拟和公式也代入可得： n4000 而r/min Km/h 3）绘制汽车行驶加速倒数曲线： 时， 1.128 ig=5.56Ua1(km/h)ft1Ff1Fw1Fw1+Ff11/a12.5610348004.598494.3120.859014495.1710.7111744.2683911077.08494.3122.386149496.69810.5047567

8、.25626313005.17494.3126.89597501.2080.4271059.81729613090.06494.31212.62273506.93470.42441811.8661212875.55494.31218.44111512.75310.43198213.786912561.34494.31224.89445519.20650.44348515.5369412000.03494.31231.61552525.92750.4654417.0735610996.33494.31238.17838532.49040.510377ig=2.769Ua2(km/h)ft2(N)

9、Ff2Fw2Fw2+Ff21/a25.1424153986.462494.3123.463408497.77541.2192268.5706925516.623494.3129.620579503.93260.84854614.570186476.856494.31227.80347522.11550.71430419.712596519.135494.31250.89286545.20490.7120123.826526412.3494.31274.35168568.66370.72788527.683346255.821494.312100.3705594.68250.7513531.19

10、7325976.273494.312127.4688621.78080.79437934.282775476.411494.312153.9293648.24130.880975ig=1.00Ua4(km/h)ft4Ff4Fw4Fw4+Ff41/a414.239351439.676494.31226.5552520.86724.29004123.732251992.28494.31273.76445568.07652.76767140.344822339.06494.312213.1793707.49132.41591354.584172354.328494.312390.2139884.52

11、592.68180865.975652315.746494.312570.08121064.3933.14997376.655162259.235494.312769.57711263.8893.9601686.385382158.278494.312977.34951471.6615.74079694.928991977.758494.3121180.2311674.54312.9998ig=1.644Ua3(km/h)ft3Ff3Fw3Fw3+Ff31/a38.6614042366.827494.3129.825304504.13732.15889314.435673275.308494.

12、31227.29251521.60451.46034224.540643845.414494.31278.87536573.18741.22893333.202053870.515494.312144.3774638.68941.24429640.131173807.086494.312210.9274705.23941.29643746.627223714.182494.312284.74779.0521.37007552.545853548.209494.312361.6149855.92691.49365857.742693251.434494.312436.6802930.99221.

13、73301ig=0.793Ua5(km/h)ft5Ff5Fw5Fw5+Ff51/a517.95631141.663494.31242.22827536.54036.50981429.927171579.878494.312117.3007611.61274.06834450.876191854.874494.312338.9991833.31113.85608768.832491866.982494.312620.52091114.8335.23730683.197541836.386494.312906.5471400.8599.04475296.664761791.573494.31212

14、23.7871718.09953.61389108.93491711.515494.3121554.1882048.5-11.6896119.70871568.362494.3121876.8122371.124-4.9071由以上关系可由计算机作出图为：用计算机求汽车用档起步加速至70km/h的加速时间。 （注：载货时汽车用档起步加速不能至70km/h）由运动学可知： 即加速时间可用计算机进行积分计算求出，且曲线下两速度间的面积就是通过此速度去件的加速时间。 经计算的时间为： 127.0495s2.7、习题图2是题1.3中货车装用汽油发动机的负荷特性与万有特性。负荷特性曲线的拟合公式为 式中

15、，b为燃油消耗率g(kw. h); Pe为发动机净功率(kw)。 拟合式中的系数为上面表格所示。怠速油耗 (怠速转速400r/min)。计算与绘制题1.3中货车的1)汽车功率平衡图。2)最高档与次高挡的等速百公里油耗曲线。或利用计算机求货车按JB335283规定的六工况循环行驶的百公路油耗。计算中确定燃油消耗率值b时，若发动机转速与负荷特性中给定的转速不相等，可由相邻转速的两根曲线用插值法求得。 答：1) （pg取等于8 ） 1.公式如下发动机输出功率： 2.原始数据：=5.83、T =0.85、r=0.367m、CDA=2.77m2、G=38809.8=38024N、=0.013；3.计算结

16、果如下所示ig=5.56ig=2.769n(r/min)Ua1(km/h)Pe1(kw)n(r/min)Ua2(km/h)Pe2(kw)8153.4787389.5669278156.9851149.56692712075.15194617.16573120710.3448317.1657316146.88918124.71768161413.833124.7176820128.58831.33407201217.2442331.33407260311.1106240.01802260322.3095140.01802300612.8307845.4013300625.763545.40133

17、40314.5253349.92812340329.1660749.92812380416.2369552.42529380432.6029152.42529400017.0735652.15181400034.2827752.15181ig=1.644ig=1.00n(r/min)Ua3(km/h)Pe3(kw)n(r/min)Ua4(km/h)Pe4(kw)81511.765079.56692781519.341789.566927120717.4238617.16573120728.6448217.16573161423.2991824.71768161438.3038524.71768

18、201229.0445731.33407201247.7492831.33407260337.5760640.01802260361.7750440.01802300643.3936345.4013300671.3391345.4013340349.124649.92812340380.7608449.92812380454.913352.42529380490.2774752.42529400057.7426952.15181400094.9289952.15181ig=0.793n(r/min)Ua5(km/h)Pe5(kw)81524.390649.566927120736.122117

19、.16573161448.3024524.71768201260.2134731.33407260377.9004340.01802300689.9610845.40133403101.842249.928123804113.84352.425294000119.708752.15181Ua5(km/h)Pw/kwPf/kw (Pf+Pw)/000040.0023280.5492360.648899100.036381.3730891.65819924.390640.5278823.3490524.56109936.12211.714694.9598857.85244248.302454.09

20、99126.63235612.626260.213477.9423288.26784519.0707977.9004317.1983410.6964232.8173689.9610826.4868812.3524645.69334101.842238.4281813.9838361.66119113.84353.6766515.6316581.53918119.708762.4085216.4370792.759514.用作图法作出汽车功率平衡图：2) （pg取等于8）1.计算公式：等速百公里油耗公式: (L/100Km) 由 2.原始数据： =5.83、T =0.85、r=0.367m，G=

21、38809.8=38024N、 =0.013；3. 计算结果：ig=0.973(最高档）n(r/min)Ua5(km/h)Qs5(L/100km)Pe5(kw) (Pf+Pw)/81524.390647.3760799.5669274.561099120736.12217.51157817.165737.852442161448.302459.05459124.7176812.6262201260.2134710.9138731.3340719.07079260377.9004314.5792340.0180232.81736300689.9610817.3280345.401345.6933

22、43403101.842221.5431249.9281261.661193804113.84327.2168452.4252981.53918ig=1.00(次高档）n(r/min)Ua4(km/h)Qs4(L/100km)Pe4(kw) (Pf+Pw)/81519.341787.0033239.5669273.434166120728.644826.79536217.165735.633254161438.303857.77077624.717688.592931201247.749288.92919631.3340712.37301260361.7750411.2430540.0180220.06904300671.3391312.9421345.401327.06342340380.7608415.6806849.9281235.5911380490.2774724.5784352.4252946.074384由数据，做图得，