Question 5) The impeller eye tip diameter of a centrifugal compressor is 0.28m a

Question

Question 5) The impeller eye tip diameter of a centrifugal compressor is 0.28m and impeller eye hub diameter is 0.14m. The impeller tip diameter is 0.48m and rotates at 15,000rpm. The inlet stagnation temperature and pressure are 290K and 1bar. Air enters axially with velocity of 145m/s and mass flow rate of 10 kg/s. The slip factor is 0.89 and power input factor is 1.03.Find (a) The impeller blade angle at the eye tip and the eye hub. (b) Power input to the compressor. (c) The maximum Mach number at the eye of the impeller. [Answers: 33.4 and 52.83,1.303MW, 0.786

Explanation / Answer

(a)Inlet air velocity V =145 m/s

Impeller speed N = 15000 rpm

eye tip diameter = D1 = 0.28 m

Eye hub diameter = D2 = 0.14 m

Peripheral speed at the impeller eye tip radius C1=  (? D1 N) / 60 m/s

= 219.8 m/s

Impeller blade angle at eye tip = tan-1 ( V/ C1?) = tan-1(145/219.8) =33.4 degree

Peripheral speed at the impeller eye hub radius C2=  (? D?2 N) / 60 m/s

= 109.9 m/s

Impeller blade angle at hub = tan-1 ( V/ C2) = tan-1(145/109.9) =52.84 degree

(b) Impeller speed N = 15000 rpm

Impeller tip diameter D = 0.48m

U2 = Impeller speed at impeler tip

= (? D N) / 60 m/s

= 378.8 m/s

Work done per unit mass reqiured by compressor = slip factor * power input factor * U22

= 0.89 *1.03 * 378.82 J/kg

= 0.13153 MJ/kg

inlet mass flow rate m = 10 kg/s

power required for compressor = mass flow rate * Work done per unit mass reqiured by compressor

= 10 * 0.131 MW = 1.315MW

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.