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MS2230 TERMODINAMIKA TEKNIK II; SEM. II 2015/2016

TUGAS KELOMPOK KE 1

Dikumpulkan hari Jumat, 4 Maret 2016 (jam 15:00 di Lab Termo, khusus kelas pak

Nengah dikumpulkan di Lab. Fluida)

1. 

Udara memasuki mesin turbojet pada temperatur 240 K, tekanan 0,85 bar, dan kecepatanmasuk 1.100 km/h. Rasio tekanan pada kompresor adalah 8. Temperatur fluida memasuki

turbin adalah 1.200 K dan tekanan pada sisi keluar nosel adalah 0,8 bar. Kerja yang

dihasilkan turbin seluruhnya digunakan oleh kompresor. Difuser dan nosel bekerja secara

isentropik, sedangkan efisiensi isentropik kompresor dan turbin secara berurutan adalah

0,8 dan 0,9. Untuk kondisi tunak, hitunglah tekanan pada setiap tingkat keadaan [bar] dan

kecepatan fluida keluar dari nosel [m/s]. Gunakan asumsi yang diperlukan.

2.  A test on an open loop Brayton cycle combustion gas turbine produces the following

results:

 Net power output = 180.5 hp

Air mass flow rate = 20.0 x 103 lbm/hAir inlet temperature = 80oF

Inlet air pressure = 14.5 psia

Compressor exit pressure = 195 psia

Compressor isentropic efficiency = 85%

Combustion chamber heat addition = 4.00 x 106 Btu/h

Using a cold air standar analysis and assuming k = 1.4, determine

a)  The cycle thermal efficiency.

 b)  The turbine inlet temperature.

c)  The isentropic efficiency of the turbine.

d)  The back work ratio of the system.

3. 

An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The

minimum and maximum temperatures in the cycle are 540 and 2200 R. Accounting for

the variation of specific heats with temperature, determine:

(a)  the amount of heat transferred to the air during the heat addition process, in Btu/lbm

(b) the thermal efficiency, and

(c)  the thermal efficiency of a Carnot cycle operating between the same temperature

limits.

4.  An air-standard Diesel cycle has a compression ratio of 16 and a cutoff ratio of 2. At the

 beginning of the compression process, air is at 95 kPa and 27

o

C. Accounting for thevariation of specific heats with temperature, determine:

(a) 

the temperature after the heat-addition process, in K,

(b) the thermal efficiency, and

(c)  the mean effective pressure, in kPa.

5.  A four-cylinder 4.5-L diesel engine that operates on an ideal Diesel cycle has a

compression ratio of 17 and cutoff ratio of 2.2. Air is at 27oC and 97 kPa at the beginning

of the compression process. Using the cold-air standard assumptions, determine how

much power the engine will deliver at 1500 rpm.

6. 

A Bryton cycle with regeneration using air as the working fluid has a pressure ratio of 8.The minimum and maximum temperatures in the cycle are 310 and 1150 K. Assuming an

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isentropic efficiency of 75% for the compressor and 82% for the turbine and an

effectiveness of 65% for the regenerator, determine:

(a)  the air temperature at the turbine exit, in K,

(b) 

the net work output, in kJ/kg, and

(c)  the thermal efficiency, in %.

Selamat bekerja.