OTTO CYCLE/ENGINE(problem EXERCISES)

1. An ideal Otto cycle has a compression ratio of 8. At the beginning of compression, air is at 14.4 psia and 75oF. During constant-volume heat addition 480 Btu/lbm of heat is transferred. Calculate: (a) The maximum temperature using ITEM B1,

a. 4063.34oR b. 3500oRc. 3925.44oR d.4029.11oR

(b) same as (a) but using ITEM B2,a. 3456.87oR b. 3467.43oRc. 3546.78oR c. 3565.96oR

(c) etc using ITEM B1 and ITEM B2,a.56.47%, 51.48% b. 54.7%, 45.38%c.56.47%, 48.56% d. 54.7%, 57.56%

(d) Work net using ITEM B1 and ITEM B2,a. 280.45 and 276.45: Btu/lb b. 245.12 and 220.45: Btu/lbc. 271.06 and 246.12: Btu/lb d. none of the above

2. An engine equipped with a single cylinder having a bore of 12 cm and a stroke of 50 cm operates on an Otto cycle at 300 rpm. At the beginning of the compression stroke air is at 100 kPa, 25°C. The maximum temperature in the cycle is 1100°C. (a) If the clearance volume is 1500 cm3/s. Determine: Ideal thermal efficiency.

a. 71.45% b. 54.55%c. 80.45% d. 69.73%

(b) Work net,a. 7.45 KJ/s b.6.778 KJ/sc. 6.985 KJ/s d. 5.542 KJ/s

(c) mepa.239.723 KPa b. 240.542 KPac. 324.234 KPa d. 28.452 KPa

3. A six-cylinder engine with a volumetric efficiency of 90% and a thermal efficiency of 38% produces 200 kW of power at 3000 rpm. The cylinder bore and stroke are 100 mm and 200 mm respectively. If the condition of air in the intake manifold is 95 kPa and 300 K, Assume the heating value of the fuel to be 35 MJ/kg of fuel. Determine:(a) the mass flow rate of air in kg/s,

a. 0.5124 kg/s b. 0.4678 kg/sc. 0.2451 kg/s d. 0.6542 kg/s

(b) the fuel consumption rate in kg/s, and a. 0.01504 kg/s b. 0.0214 kg/sc. 0.06452 kg/s d. 0.0325 kg/s

(c) the specific fuel consumption in kg/kW.hr. a. 0.2545 kg/s b. 0.3451 kg/sc. 0.2707 kg/s d. 0.2012 kg/s

4. A four-cylinder four-stroke engine operates at 4000 rpm. The bore and stroke are 100 mm each, the MEP is measured as 0.6 MPa, and the thermal efficiency is 35%. Determine (a) the power produced by the engine in kW,

a. 54.24 kW b. 65.23 kW c. 62.83 kW d. 46.89 kW

(b) the waste heat in kW,a. 116.69 kW b. 125.45 kW c. 114.15 kW d. 215.10 kW

(c) torque develop if the indicated and mechanical engine efficiency are 89% and 80% respectively

a. 106.797 N-m b. 110.45 N-mc. 125.45 N-m d. 103.45 N-m

5. An ideal otto engine is used that burns 30 kg/hr of fuel with a lower heating value of 50000 kJ/kg in 400 kg/hr of air. Find the Worknet if the compression ratio is 15.

a. 275.62 kWb. 255.62 kWc. 265.62 kW

d. 245.62 kW

6. A 8-cylinder, 3.5 x 3.5 in. Automotive engine with rk = 8, develops 119 bhp at 3600 RPM. Determine the Bmep and the brake engine efficiency using k = 1.33 with 0.48 lb/bhp.hr of fuel consumption with a LHV of 18750 BTU/lb.a. 48.59 psi, 56.94% c. 40.59 psi, 56.94%b. 41.59 psi, 56.94% d. 42.59 psi, 56.94%

7. Determine the approximate cylinder dimension of a 6-cylinder, four stroke spark-ignition engine to deliver 200 Bhp at 3500 RPM. Diameter to stroke ratio is a.2 and from experiment, it is concluded that the brake mep = 150 psi.

a. 4 x 3.33 in. c. 4 x 4.44 in.b. 3 x 4.44 in. d. 3 x 3.33 in.

8. An ideal otto with 8% clearance operates on 20 lb/min of air initially at 14.4 psia and 120 F . Determine, Vd and the mass drawn during suction for a volume efficiency of 80%.

a. 276.3 ft3 /min , 14. 816 lb/minb. 276.3 ft3 /min , 110. 816 lb/min c. 269.3 ft3 /min , 10. 816 lb/min d. 267.3 ft3 /min , 14. 816 lb/min

9. An air standard Otto Cycle, the state at the beginning of compression is 20 psia, 150 F, the compression ratio is ⁰rk=9. Find the clearance, P2, T2, if cold air is the working fluid respectively.

a) c=0.14, P2= 433.48 psia, T2 = 1469 R⁰b) c=0.125, P2 = 423.48 psia, T2 = 1469 R ⁰ c) c=0.125,P2 = 433.48 psia,T2 = 1469 R⁰

10. An air standard Otto cycle whose working fluid is hot air(k=1.31), the state at the beginning of compression is 20 psia, 150 F, the compression ratio is r⁰ k =9. Find the clearance, P2, T2.

a) c=0.14, P2= 355.70 psia, T2 = 1205.44 R ⁰b) c=0.125, P2 = 355.70 psia, T2 = 1205.44 R⁰ c) c=0.125,P2 = 355.70 psia,T2 = 1469 R⁰

11. An air standard Otto Cycle, the state at the beginning of compression is 20 psia, 150 F, the ⁰compression ratio is rk= 9. Find the clearance, P2,

T2 using ITEM B2.

a) c=0.125, P2= 415.73 psia, T2 = 1411.21 R ⁰b) c=0.125, P2 = 415.83 psia, T2 = 1411.21 R⁰ c) c=0.12, P2 = 415.73 psia, T2 = 1411.21 R⁰

12. What is the cycle efficiency in an air standard Otto Cycle, whose rk=9?

a) 0.585 b) 0.494 c) 0.594

13. For an ideal Otto engine with 18% clearance and an initial pressure of 95 kPaa, determine the pressure at the end of compression using ITEM B1.

a) P = 1325.46kPaab) P = 1324.46kPaac) P = 1324.46psia

14. For an ideal Otto engine operating on the air standard (ITEM B2), temperature at the end of expansion is 2490 F and at the end of isentropic compression is 860 F. ⁰ ⁰

Find the work and efficiency if rk =7.

a) W=427.94 BTU/lb, etc=0.478%b) W=427.94 BTU/kg, etc=0.478% c) W=427.94 kJ/kg, etc=0.478%

15. Sketch an otto cycle on PV and TS planes with point 1 being the beginning of the isentropic compression process. These data apply for the air standard cycles P1 = 101.4 kPaa, T1 = 333.3 K, V1 = 283 L, rk = 5 and T3 = 2000 K. Solve for m1. 

a. 0.3 kgm c. 0.6 kgmb. 0.8 kgm d. 0.9 kgm

16. From the previous problem 15, find V2.

 a.56.6 L c. 56.0 L

b. 60.8 L d. 65.6 L

17. From problem 15, find QA that have T2 = 634.5 K. 

a. 294.42 kJ c. 594.88 kJb. 394.35 kJ d. 600.35 kJ

18. Find also QR in problem 15 with T4 = 1050.6 K. 

a. 154.66 kJ c. 354.88 kJb. 254.77 kJ d. 545.99 kJ

19. Find the thermal efficiency of the otto engine in problem 15. 

a. 47.5 % c. 66.8%b. 57.9 % d. 37.5%

20. A four stroke Otto cycle engine has four cylinders with 10X10 cm in size. It has an ideal thermal efficiency of 52% running at 200 rpm. What is the volume before the compression if k=1.4.

a. 0.7475m3/min c. 1.003m3/min b. 0.8361 m3/min d. 0.5639 m3/min

21. What is the mass of air needed for an Otto cycle engine with a pressure of 101.3 Kpaa and a temperature of 29°C at the beginning of compression, and if the ideal thermal efficiency is 50% with two cylinder (9X10 cm) running at 500 rpm? (apply air standard cycle)

a. 1kg/min c. 0.903 kg/min b. 1.303 kg/min d. 0.822 kg/min

22. An Otto cycle with pressure and temperature of 101.3 Kpaa and 340 K respectively before the compression, and it has a compression ratio of 8. Find the pressure during the power stroke if its temperature is 1400K. Use k = 1.32.

a. 3336.92 Kpaa c. 2871.22 Kpaa

b. 4334.1 Kpaa d.1592.46Kpaa

23. What is the main effective pressure for a Otto cycle having a compression ratio of 10 and the heat added is 100 KW if volume displaced is 0.6 m3/min and k=1.4.

a. 6018.9 Kpaa c. 3429.12 Kpaa

b. 5392.3 Kpaa d.4932.75Kpaa

24. An ideal Otto Cycle operates an 0.5 lb/s of air and at the beginning of the compression is 14.1 psia, 140 F, and also has a clearance of 15%. The energy released during combustion is 500 Btu/s. Compute for a.) rk b.) P and T at each corner c.) etc

a.) rk = 9; T2= 1355.194; P2= 422.16; P3= 1295.36; P4= 74.5psia; 3183.09; etc=52.9%b.) rk = 7.667; T2= 1355.194; P2= 244.17; P3= 1295.36; P4= 74.8psia; 3183.09; etc=53.726%c.) rk = 9; T2= 1455.194; P2= 422.16; P3= 1295.36; P4= 74.5psia; 5113.09; etc=62.9%d.) none of the above

25. For an ideal otto engine, the overall value k=1.4, C= 15%, T4= 2840 F, V2= 0.5 ft3/s, T1= 120 F and 1 lbm/s. Find mep.

a. mep= 1005.9 psiab. mep= 509.8 psiac. mep= 950.8d. none of the above

 

26. A 4 stroke 4 cylinder gasoline engine to deliver 90 bhp at 1800 rpm w/ D=L= 5in; It has a bmep= 110 psi, the mechanical efficiency, nme= 80% and has specific fuel consumption of 0.5 lbmfuel / bhp-hr and LHV qin = 18000 Btu/ lbmfuel. Let rk= 7 and k=1.4. Calculate the a.) etb and imep b. QA and QB.

a. ) etb= 48.2%; imep= 126.05 psi; QA= 419.25hp; QR= 160.6 hpb.) etb= 28.27%; imep= 126.05 psi; QA= 318.92hp; QR= 150.556 hpc.) etb= 48.2%; imep= 126.05 psi; QA= 318.92hp; QR= 160.6 hpd.) none of the above

27. An ideal Otto Cycle operates 1 lbm of air and has a 13.8 psia at the suction and 140 F. It has a compression ratio of 7. a.) find P and T at the end of compression and the ideal thermal efficiency.

a.) P2= 210.386 psia; T2= 1306.744 R; etc= 54.08%b.) P2= 310.386 psia; T2= 1206.744 R; etc= 54.08%c.) P2= 310.386 psia; T2= 1306.744 R; etc= 54.08%d.) None of the above

28. An ideal Otto engine is operating in a 2 stroke gasoline to deliver 100 hp at 1500 rpm. The brake mean effective pressure should not exceed 110 psia and the mechanical efficiency is approximately 80%. Determine the cylinder dimensions if bore-to-stroke ratio is 1.

a. 15.89 cm c. 158.86 mmb. 17.25 cm d. 172.50 mm

29. An Otto cycle with an initial pressure, temperature and volume of 95 kPaa, 27 °C and 300 liters respectively has a compression ration of 7. If the system uses cold air as the working substance, determine the work done by the system. The highest temperature is ten times greater than the initial temperature at absolute temperature.

a. 298 kW c. 558 kWb. 302 kW d. 257 kW

30. What is the ideal thermal efficiency of an ideal Otto cycle if the mechanical efficiency, indicated engine efficiency, and the brake thermal efficiency are 85%, 70% and 30 % respectively?

a. 45.50% c. 50.42%b. 25% d. 85.75%

31. An ideal Otto engine with 10% clearance operates on 15 lbm/min of air initially at 1atm and 100 °F. Determine its volume displacement and the mass drawn in during suction for a volumetric efficiency of 80%.

a. 201.43 ft3/min; 10.91 lbm/minb. 192.43 ft3/min; 13.64 lbm/min c. 192.43 ft3/min; 10.91 lbm/mind. None of the above.

32. An otto cycle with a compression ratio of 8.5 operates from the suction conditions of 97.91 KPa, 30 C. Find the pressure and temperature at the end of compression. Solve for the ideal thermal efficiency.

a.) 1958.91 KPa; 57.52%b.) 1858.81 KPa; 57.52%c.) 2000.00 KPa; 57.52%d.) 1959.21 KPa; 57.52%

33.An ideal Otto engine with an ideal thermal effcy. Of 60% and V2=200 L. Calculate

A.) Compression ratio

a.) 16.882 c.) 12.882b.) 10.882 d.) 9.882

B.) volume displacement in m3

a.) 3.7764 m3 c.) 1.7764 m3

b.) 2.7764 m3 d.) 4.7764 m3

34. An ideal Otto engine having a volumetric effcy of 90% and V1=60 ft3 with heat rejected of 1032 KJ/s. Determine the heat added at the cycle if the mean effective pressure of 600KPa.

a.) 2243.6 KJ/s c.) 2323.6 KJ/sb.) 2553.6 KJ/s d.) 2263.6 KJ/s

35. A 4 cylinder, 6 ½ X 8 in., 4 stroke automobile engine having a work net and mean effective pressure of of 300 hp and 190 psia respectively operates at a certain speed. Determine the speed in rpm that operates the engine.

a.) 1274.74 rpm c.) 1174.74 rpmb.) 1184.74 rpm d.) 1344.74 rpm

36. An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, the air is at 100 kPa and C, and 800 kJ/kg of heat is tranferred to air during the constant-volume heat-addition process. Accounting for the variation of specific heats of air with temperature, determine (a) the maximum temperature and pressure that occur during the cycle, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle.

a. 1575.1 K, 4.345 Mpa, 418.17 kJ/kg, 52.3%, 574.4 kPa b. 1576.2 K, 3.476 Mpa, 417.45 kJ/kg, 53.3%, 575.2 kPac. 1574.3 K, 2.576 Mpa, 419.56 kJ/kg, 54.6%, 576.3 kPad. 1577.5 K, 5.387 Mpa, 416.35 kJ/kg, 55.6%, 577.2 kPa

37. An engine operating on the air-standard Otto cycle has a 15 percent clearance volume, a total displacement volume of 2.8 liters, and operates at 2500 rev/min. The heat added is 1400 kJ/kg. Determine the maximum temperature and pressure, the thermal efficiency, power and the available portion of the heat rejected. The inlet conditions are C and 100 kPa, and . Use the air table values.

a. 2211 K ; 5.65 MPa ; 49.85% ; 108.6 kW ; 78.5%b. 2144 K ; 6.35 Mpa ; 48.50% ; 135.5 kW; 74.75%c. 2356 K ; 7.33 Mpa ; 45.3% ; 146.84 kW ; 70.35%d. 2090 K ; 8.42 Mpa ; 40.42% ; 143.6 kW ; 70.93%

38. An ideal otto engine with 25% clearance operates on 1 lb. of air. psia, and Let . (a) , (b) and , (c) .

a. 12.26 cf. ; 480 ; 113.4 psia ; 627 psia ; 38.3%b. 13.59 cf. ; 470 ; 123.3 psia ; 693 psia ; 39.4%c. 11.46 cf. ; 460 ; 114.5 psia ; 692 psia ; 39.2%d. 19.35 cf. ; 490 ; 131.3 psia ; 642 psia ; 30.5%

39. An Otto cycle operates on 0.2 lb/s of air from 14 psia and 1400F at the beginning of compression. The temperature at the end of combustion is 50000R; compression ratio is 5.5; hot-air standard, k= 1.3.   Find V1, p2, t2, p3, V3, t4 and p4.

a. 3.18ft3/s ; 128.41psia ; 540.60F ; 641.67psia ; 0.578ft3/s ; 25380F & 69.95psiab. 3.18ft3/s ; 128.41psia ; 405.60F ; 641.67psia ; 0.578ft3/s ; 25380F & 69.95psiac. 3.18ft3/s ; 128.41psia ; 540.60F ; 641.67psia ; 0.875ft3/s ; 25380F & 69.95psiad. 3.18ft3/s ; 128.41psia ; 540.60F ; 146.76psia ; 0.578ft3/s ; 25380F & 69.95psia Compute QA, QR, W, ea. 183.54Btu/s ; 109.59Btu/s ; 73.95Btu/s & etc = 29.40%b. 183.54Btu/s ; 109.59Btu/s ; 73.95Btu/s & etc = 40.29%c. 183.54Btu/s ; 109.59Btu/s ; 553.95Btu/s & etc = 40.29%d. 183.54Btu/s ; 233.59Btu/s ; 73.95Btu/s & etc = 40.29%

40. The conditions at the start of compression in air standard Otto cycle are 14.7psia and 1000F. The heat supplied per pound of air is 900Btu. The compression ratio is 9. Determine:A. the minimum temperatureB. the minimum pressureC. the thermal efficiency D. the mep.  a.) T3 = 7599.490R ; p3 = 1559.3psia ; etc = 58.48% & mep = 226.79psiab.) T3 = 6599.490R ; p3 = 1559.3psia ; etc = 158.48% & mep = 226.79psiac.) T3 = 6599.490R ; p3 = 1559.3psia ; etc = 58.48% & mep = 326.79psiad.) T3 = 6599.490R ; p3 = 1559.3psia ; etc = 58.48% & mep = 226.79psia

41. The conditions at the beginning of compression in an Otto engine operating on hot-air standard with k=1.4, are 101.3kPa, 0.05m3 and 320C. The clearance is 12% and 13kJ are added per cycle. Determine: T4 and p4 , WNET , etc , mep   a.) T4 = 433.11K & p4 = 143.85kPa ; WNET = 7.68kJ ; etc = 59.08% ; mep = 172.04kPab.) T4 = 833.11K & p4 = 143.85kPa ; WNET = 7.68kJ ; etc = 59.08% ; mep = 12.04kPac.) T4 = 633.11K & p4 = 143.85kPa ; WNET = 9.68kJ ; etc = 59.08% ; mep = 172.04kPad.) T4 = 433.11K & p4 = 13.85kPa ; WNET = 7.68kJ ; etc = 5.08% ; mep = 172.04kPa

42. There is developed torque of 200 lb-ft by a 6-cylinder, 4stroke-cycle, a single- acting engine having an indicated mep of 120 psi when operating at 2900 rpm. Performance curve suggest a mechanical efficiency of 75% and a brake thermal efficiency of 25% at this speed. For the engine let the clearance c= 14%; the ratio L/\D = 1 and t1 =1700F; k=1.31. Compute: the bhpthe bore and strokethe compression ratiothe indicated engine efficiency a. WB = 110.43hp; D=L=2.15in ; rk = 8.14 & nI =79.73%b. WB = 110.43hp; D=L=3.15in ; rk = 8.14 & nI =69.73%c. WB = 900.43hp; D=L=3.15in ; rk = 8.14 & nI =59.73%d. WB = 1210.43hp; D=L=1.15in ; rk = 8.14 & nI =69.73%

43. In a spark-ignition engine that is completing 20,000 cycle/min, the mass of the fuel is 0.00022 lb/cycle with a lower heating value of 18,000 BTU/lb and its brake thermal efficiency is 30%. What is the work of the engine?

a. 506.82bhp c. 580.6 bhpb. 560.28 bhp d. 528.60 bhp

44. 69 bhp is the work required by a 4-cylinder, 4-stroke cycle, single acting, spark-ignition engine with a torque and brake mep of 122 ft-lbf and 80 psi, respectively. Find the bore and stroke (assume D/L = 1).

a. 4.831 x 4.831 in. c. 4.183 x 4.183 in.b. 4.008 x 4.008 in. d. 8.183 x 8.183 in.

45. For one hour operation of a gasoline engine, a Mechanical Engineer designer wants to use a fuel tank as a container of a minimum fuel supply of these engine (6-cylinder, 0.09 x 0.08 m) which at maximum output develops a brake torque of 200 N-m at 3500 rpm. The corresponding ideal engine showed a thermal efficiency of 65.6%, the brake engine efficiency is expected to be 63%. The lower heating value and the specific gravity of the fuel are 40,000 KJ/kg and 0.8, respectively.

a. 0.02 m3 per hour c. 0.0002 m3 per hourb. 0.002 m3 per hour d. 0.00002 m3 per hour

46. In an ideal otto engine with 22% clearance and an initial pressure of 100 kPaa, find the pressure at the end of compression using air-standard properties from Item B1. Also find the mep (in psi) if the pressure at the end of constant volume heating is 3500 kPaa.

a. 1100.18 kPaa; 655.389 kPaab. 1100.18 kPaa; 630.389 kPaac. 1100.18 kPaa; 680.389 kPaad. 1000.18 kPaa; 655.39 kPaa

47. An otto engine developed a torque of 200 ft-lbf by a 6 cylinder, 4-stroke-cycle, single acting having an indicated mep of 110 psi when operating at 3000 rpm. Performance curves suggest a mechanical efficiency of 80% speed. Assume that the ratio of bore and stroke must be 1. At the point of compression, p1 = 14.4 psia and t1 = 170 ۫F ; k = 1.32. what is D x L?

a. 4.17 x 4.17 in. c. 2.17 x 2.17 in.b. 3.17 x 3.17 in. d. 1.17 x 1.17 in.

48. An otto cycle with a compression ratio of 8.6 operates from the suction condition of 96.81 kPa, 24.9°C. Find the pressure and temperature at the end of the compression;If hot air (k = 1.32) is the working substance.a. t2 = 321.19 °C; P2 = 1658.63kPa b. t2 = 320.08 °C; P2 = 1657.52 kPa If cold air (k = 1.4) is the working substance.a. t2 = 431.48 °C P2 = 1968.87 kPa b. t2 = 432.59°C P2 = 19689.98 kPa Solve for the ideal thermal efficiency based upon the conditions given in A and B.a. etc = 58.82 %

b. etc = 57.71 %

49. These data apply for the air standard cycle. P1 = 102.5 kPa ; T1 = 444.4 K ; V1 = 394 L ; rk =6; T3 = 3000 KSolve for the following: m1 = ?a. m1 = 0.32 kg b. m1 = 0.43 kg P2 , T2 , V2

a. V2 = 66.78 L T2 = 910.88K P2 = 1268.45 kPa b. V2 = 65.67 L T2 = 909.99 K P2 = 1259.34 kPa 

P3 , rp

a. rp = 12.29 P3 = 4151.72 kPa b. rp = 13.38 P3 = 4152.83kPa P4 , T4 a. T4 = 1476.19 K P4 = 338.83 kPa b. T4 = 1465.08 K P4 = 337.92 kPa

50. From the solved operating conditions in the previous problem, determine;QA

a. QA = 480.68 kJb. QA = 481.79kJ QR

a. QR = 233.78kJb. QR = 232.67kJ etca. etc = 51.6 %b. etc = 52.7 %

mep in psiga. mep = 95.98 psigb. mep = 94.89 psig

Ca. C= 20 %b. C= 21 % 

51. The air in an ideal otto engine is initially at 15.6 psia, 200 °F, at the end of isentropic compression, the pressure is P2=463 psia, at the end of combustion the pressure is P3=1200 psia. Based upon air-table values, find:

rk

a. rk = 12.88b. rk = 11.79 percentage clearance, Ca. C = 9.27%b. C = 9.38% t3

a. = 3847.53b. = 3846.42

52. From the solved operating conditions in the previous problem, determine the cycle thermal efficiency. Also, if the sink temperature is 100°F, compute for the percentage of the heat added utilized?

A. a. etc = 56.53 %b. etc = 57.64 %

 B. a. % Heat Available = 75 %

b. % Heat Available = 74 %

53. Determine the approximate cylinder dimensions of a four cylinder, four stroke gasoline engine to deliver 200 bhp at 3000 rpm; diameter/stroke ratio; D/L = 1. From experience it is expected that bmep = 140 psi; the mechanical efficiency nme = 85%, brake specific fuel consumption mfb = 0.66 lb/(bhp-hr) , lower heating value of fuel Qin = 18000BTU/lb.Let rk = 7.6 and use an average k = 1.32.D, La. D = L = 4.93 in.b. D = L = 5.84 in. calculate the expected etb and indicated engine efficiencya. etb = 22.53 % ni = 53.88 % b. etb = 21.42 % ni = 52.79 % the brake engine efficiencya. nb = 44.87%b. nb = 45.98%

54. From the solved operating conditions in the previous problem, determine;the heat added in BTU/min ;a. QA = 39 599.9 BTU/min b. QA = 39 588.8 BTU/min  the heat rejected in BTU/min;a. QR = 20 683.82 BTU/min b. QR = 20 694.91 BTU/min the mass of air needed in kg/hr ; rf/a = 20a. mair = 1 197.28 kgair /hr b. mair = 1 198.39 kgair /hr

55. An otto cycle with rk = 11 operates at 150 kpa at 27C. if cold air is used. What is the pressure at the end of compression and the etc?

a) 4315.2kpa, 61.70%b) 4310.5kpa, 61. 77%c) 4320.3kpa, 61.69%d) 4305.7kpa, 61. 7%

56. An otto cycle has this data:P1 = 167kpaT1 = 400kV1 = 350Lrk = 7P3 = 3000kpak = 1.32

Find Qa:

a) 103kJ c) 101kJb) 105kJ d) 109kJ

57. An otto cycle has a mass of 0.5kg at 38C and 240kpa, k =1.35, at the end of the compression P = 777kPa. The energy released during combustion is 450kJ. What is the work net?

a) 120kJ c) 118kJb) 150kJ d) 115kJ

58. A 0.1kg otto engine with 20% clearance has a pressure of 100kpa, a temperature of 10C and a volume of 0.3m3. Determine the Mep if the pressure at the end of the constant volume heating is 4000kPa.

a) 194kPa c) 189kPab) 190kPa d) 192kPa

59. The air in an otto engine is initially at 24psia, 140F and P2 = 460psia, using air tables. What is the percentage clearance?

a) 15% c) 13%b) 14% d) 12%

60. An Otto engine has a clearance volume of 7%. It produces 300 kW of power . What is the amount of heat rejected in kW?

a.) 170 c.) 152b.)160 d.) 145

61. In an air standard Otto cycle, the clearance volume is 18% of the displacement volume. Find the thermal efficiency.

a.) 0.52 c.) 0.53b.) 0.55 d.) 0.60

62. The compression ratio of an ideal Otto cycle is 6:1. Initial conditions are 101.3 kPa and 20°C. Find the pressure and temperature at the end of adiabatic compression.

a.) 1244.5 kPa, 599.96 K b.) 1244.5 kPa, 60°Cc.)1244.5 kPa, 60°C d.) 1244.5 kPa, 599.96°C

63. An engine operates on the air-standard Otto cycle. The cycle work is 1000 kj/kg. What is the compression ratio of the engine if the maximum cycle temperature is 3173 K and the temperature at the end of isentropic compression is 773 K.

a.) 6.85 c.) 7.85b.)8.85 d.) 9.85

64. The conditions at the beginning of compression in an Otto engine operating on hot-air standard with k=1.35 are 101.325 kPa, 0.05 m3 and 32°C. The clearance is 8% and 15 kJ are added per cycle. Determine the mean effective pressure.

a.) 323.97 kPa c.) 223.97 kPab .) 423.97 kPa d.) 523.97 kPa

65. The compression ratio of an Otto cycle is 9. If the initial pressure is 150 kPa, determine the final pressure.

a.) 1251.10 kPa b.) 2251.10 kPac.) 4251.10 kPa d.) 3251.10 kPa

66. In an Otto cycle if the compression ratio is 5.5, what is the percent clearance?

a.) 22.22% b.) 19.64%c.) 31.11% d.) 25.34%

67. The efficiency of an Otto engine is 55% and the stroke volume is 35 liters. If the heat added at the beginning of the combustion is 12.6 kJ, calculate the mean effective pressure.

a.) 194 kPa c.) 198 kPab.) 188 kPa d.) 184 kPa

68. The air is compressed to 1/5 of its original volume in an Otto cycle. What is the final temperature of the air if the initial temperature is 25°C.

a.) 288.58°C b.) 255.66°Cc.) 288.58°C d.) 355.66°C

69. An Otto cycle operates 1 kg of air from 101.325 kPa and 25°C at the beginning of compression. If the clearance is 15%. Find the temperature at the end of compression.

a.) 300°C b.) 450.01°Cc.) 400°C d.) 350.01°C

 70. The efficiency of an ideal Otto cycle is 40%. What is the hot-air value o k, if the compression ratio is 6.2?

a.) 1.28 c.) 1.25b.) 1.38 d.) 1.35

71. What is the clearance of an ideal Otto cycle if the efficiency is 40% and k = 1.3?

a.) 20.24% c.) 10.24%b.) 22.27% d.) 12.27%

72. An Otto cycle operates a 0.5 lb/s of air from 15psia and 150°F. at the beginning of compression. The compression ratio is 4.3; hot air standard k = 1.3. Determine the volume at the of compression.

a.) 2.75 ft3/s c.) 3.75 ft3/sb.) 1.75 ft3/s d.) 4.75 ft3/s

73. In an air-standard Otto cycle, air enters 104.7 kPa and 27°C. The compression ratio is 7:1. If the net work of the cycle is 120 kJ/kg. Calculate the heat supplied in kJ/kg?

a.) 221.88 kJ/kg c.) 188.22 kJ/kgb.) 122.88 kJ/k d.) 288.12 kJ/kg

74. Calculate the thermal efficiency and compression ratio for an automobile working on Otto cycle. If the energy generated per cycle is thrice that of rejected during the exhaust. Consider working fluid as an ideal gas with k = 1.4.

a. 69.67%, 13.38   c. 66.67%, 15.38  b. 61.67%, 12.38   d. 56.67%, 11.38  

75. An engine of 250 mm bore and 375 mm stroke works on Otto cycle. The clearance volume is 0.00263 m3. The initial pressure and temperature are 1 bar and 50oC. If the maximum pressure is limited to 25 bar. Find:The air standard efficiency of the cycle & the mean effective pressure for the cycle.  a.. 46.57%, 9.87 bar c. 56.57%, 1.87 barb. 50.57%, 4.87 bar d. 59.57%, 8.87 bar 

76. In an Otto cycle, the air at the beginning of isentropic compression is at 1 bar and 15oc, The ratio of compression is 8. If the heat is added during the constant volume process is 1000 kJ/kg. Determine: (A)The maximum temperature in the cycle 2056 K(B)The air standard efficiency 56.5%(C)The work done per kg of air, and565 kJ/kg(D)The heat rejected 435 kJ/kg a. 2156 K, 56.5%, 555 kJ/kg, 465 kJ/kgb. 2256 K, 56.5%, 565 kJ/kg, 435 kJ/kgc. 2356 K, 56.5%, 575 kJ/kg, 435 kJ/kgd. 2056 K, 56.5%, 565 kJ/kg, 435 kJ/kg

77. The air at the beginning of compression in an ideal explosion cycle is at 14 psia, 110 °F. The engine with a clearance volume of 0.8 ft3 /sec operates on 0.5 lb/sec of air. Find the ideal thermal efficiency.

a. etc = 59.23%b. etc = 69.32%c. etc =79.23%d. etc = 49.32%

78. A man wishes to buy an Otto engine for his car. Engine A operates ideally on cold air with 15% clearance. Another engine, Engine B, operates ideally with 25% clearance and with specific heat ratio of 1.5. Which of two engines must he buy?

a. Engine Ab. Engine Bc. Bothd. Neither of the two

79. Given that in an ideal Otto engine, the specific heat ratio is 1.32 and the compression ratio is 19. It uses 16 lb of air per 1 lb of fuel with a lower heating value of 20 000 BTU per lb of fuel. Solve for the heat involved during the first constant volume process.

a. QA = 1250 BTU/lba

b. QA = 1938 BTU/lba

c. QA = 1630 BTU/lba

d. QA = 1563 BTU/lba

80. From the previous problem, Solve for the heat involved during the last constant volume process.

a. QR = 582.51 BTU/lba

b. QR = 764.98 BTU/lba

c. QR = 392.67 BTU/lba

d. QR = 487.20 BTU/lba

81. An ideal explosion cycle that uses 0.75 lb/sec of air operates from the suction condition of 567 °R. The pressure and compression ratio are 1.6 and 16, respectively. Using the air properties in item B1, determine the total work developed in horsepower.

a. WNET = 125.687 hpb. WNET = 215.786 hpc. WNET = 512.687 hpd. WNET = 152.786 hp

82. An ideal Otto cycle operates with rk = 14 and rp = 1.75. It uses 60 lb/min of air and has a total work of 146 kW. Using item B1, find the temperature at the beginning of isentropic compression.

a. T1 = 583.51 °Rb. T1 = 385.51 °Rc. T1 = 511.51 °Rd. T1 = 574.51 °R

83. For an Explosion cycle with a clearance of 14%, the air has a suction condition of P1 = 98 kPaa and t1 = 110°F. What is the compression ratio of the cycle?

a. rk = 7.14b. rk = 6.14c. rk = 8.14d. rk = 9.14

84. From the given data of the previous problem, the volume of displacement is 6.14 ft3/s. Find the clearance volume.

a. V2 = 0.86 ft3 /sb. V2 = 0.68 ft3 /s c. V2 = 0.76 ft3 /s d. V2 = 0.67 ft3 /s

85. What is the suction volume from the previous problem?

a. V2 = 6 ft3 /s b. V2 = 7 ft3 /s c. V2 = 9 ft3 /s d. V2 = 8 ft3 /s

86. Find the mass of air needed to operate the system of the previous problem.

a. ma = 0.741 lba /sb. ma = 0.571 lba /s c. ma = 0.471 lba /s d. ma = 0.715 lba /s

87. Based on the previous problem what is the ideal thermal efficiency of the given cycle?

a. etc = 77.53 %b. etc = 56.77 %c. etc = 58.99 %d. etc = 67.35 %

88. If the engine uses 2.02 lb/min of fuel, solve for the air-fuel ratio. a. rf/a = 13.99 lba/lbf

b. rf/a = 15.99 lba/lbf

c. rf/a = 16.99 lba/lbf d. rf/a = 12.99 lba/lbf

89. The fuel used has a lower heating value of 21 500 BTU per lb of fuel. A. What is the heat (in BTU/min) involved during the first constant volume process?a. QA = 45 467.768 BTU/min b. QA = 76 746.828 BTU/min c. QA = 63 478.893 BTU/min d. QA = 43 430.307 BTU/min

B. What is the total work produced?a. Wnet = 52 478.837 BTU/min b. Wnet = 24 655.385 BTU/min c. Wnet = 73 246.787 BTU/min d. Wnet = 20 425.879 BTU/min

90. A single acting, two – cylinder, two – stroke gasoline engine has cylinder dimensions of 10.25 x 11.21 cm. What is the volume of displacement if the engine developed 1106 kW at 300 rpm?

a. VD = 0.925 m3/sb. VD = 0.529 m3/s c. VD = 0.725 m3/s d. VD = 0.585 m3/s

91. If the indicated mean effective pressure of the given gasoline engine is 765 kPa, solve for the indicated work.

a. Wi = 567.432 kWb. Wi = 707.625 kWc. Wi = 983.432 kWd. Wi = 586.625 kW

92. What is the volume at the beginning of the isentropic expansion considering a clearance of 16%?

a. V3 = 0.272 m3/s b. V3 = 0.148 m3/s c. V3 = 0.346 m3/s d. V3 = 0.777 m3/s

93. State 1 of the problem above is defined as 96 kPa and 38 °C. What is the volume at this point?

a. V1 = 0.777 m3/s b. V1 = 0.555 m3/s c. V1 = 0.888 m3/s d. V1 = 0.676 m3/s

94. Find the mass of air needed to operate this engine.

a. ma = 0.953 kg/sb. ma = 0.929 kg/s c. ma = 0.835 kg/s d. ma =0.879 kg/s

95. If the brake thermal efficiency of the cycle above is 38.605%, solve for the heat added during constant volume process.

a. QA = 6474.96 kWb. QA = 8954.45 kWc. QA = 2864.91 kWd. QA = 3682.55 kW

 96. For a specific heat ratio of 1.33, what is the ideal thermal efficiency of the engine mentioned above?

a. etC = 72.653 %b. etC = 30.636 %c. etC = 89.952 %d. etC = 42.144 %