## THERMAL SCIENCE

International Scientific Journal

### EXPERIMENTAL INVESTIGATIONS OF FLOW THROUGH WIDE ANGLE CONICAL DIFFUSERS WITH UNIFORM FLOW AND SWIRL TYPE VELOCITY DISTORTIONS AT INLET

**ABSTRACT**

Swirl is a tangential velocity component of the fluid flow and is often present in the conical diffuser as a result of rotating machinery in the upstream section. The present experimental work is dedicated to study the effect of moderate swirl on wide angle conical diffuser performance and flow development. The experiments were performed in a low-speed open circuit wind tunnel. There are two different diffusers having a cone angle of 14° (with area ratio 3.0) and 20° (with area ratio 4.2) were selected for this investigation. The flow parameters have been measured using DANTEC DYNAMICS make constant temperature hot-wire anemometer (CTA). The results showed that the moderate swirl can significantly improve the stalled diffuser (20° cone angle) performance; however, it has a little effect on the diffuser (14°cone angle) having incipient turbulent boundary layer separation. It was confirmed that the introduction of moderate swirl reduces the chances of flow separation in wide angle conical diffusers.

**KEYWORDS**

PAPER SUBMITTED: 2017-08-17

PAPER REVISED: 2017-10-12

PAPER ACCEPTED: 2017-10-16

PUBLISHED ONLINE: 2017-11-18

**THERMAL SCIENCE** YEAR

**2018**, VOLUME

**22**, ISSUE

**Issue 6**, PAGES [2571 - 2581]

- McDonald, A.T., Fox, R.W., An experimental investigation of incompressible flow in conical diffusers, International Journal of Mechanical Sciences, 8(1966), 2, pp.125IN5131-130IN6139.
- Okwuobi, P.A.C., Azad, R.S., Turbulence in a conical diffuser with fully developed flow at entry, Journal of Fluid Mechanics, 57(1973), 3, pp.603-622.
- Klein, A., Effects of inlet conditions on conical-diffuser performance, Journal of Fluids Engineering, 103(1981), 2, pp.250-257.
- Azad, R.S., Turbulent flow in a conical diffuser: A review, Experimental Thermal and Fluid Science, 13(1996), 4, pp.318-337.
- Mahalakshmi, N.V., et al., Experimental investigations of flow through conical diffusers with and without wake type velocity distortions at inlet, Experimental Thermal and Fluid Science, 32(2007), 1, pp.133-157.
- VAN DEWOESTINE, R.V., et al., Effects of swirling inlet flow on pressure recovery in conical diffusers, AIAA JOURNAL, 9(1971), 10, pp. 2014-2018.
- Senoo, Y., et al., Swirl flow in conical diffusers, Bulletin of JSME, 21(1978), 151, pp.112-119.
- Okhio, C.B., et al., Effects of swirl on flow separation and performance of wide angle diffusers, International journal of heat and fluid flow, 4(1983), 4, pp.199-206.
- Clausen, P.D., et al., Measurements of a swirling turbulent boundary layer developing in a conical diffuser, Experimental Thermal and Fluid Science, 6(1993), 1, pp.39-48.
- Lai, Y.G., et al., Calculation of planar and conical diffuser flows, AIAA J, 27(1989), 5, pp.542-548.
- Jiang, G., He, Y., Shu, S. et al. Numerical prediction of inner turbulent flow in conical diffuser by using a new five-point scheme and DLR k-ɛ turbulence model, Journal of Central South University of Technology, (2008) 15(Supplement 1).
- Armfield, S.W., Fletcher, C.A.J., Numerical simulation of swirling flow in diffusers, International journal for numerical methods in fluids, 6(1986), 8, pp.541-556.
- Cho, N.H. and Fletcher, C.A.J., Computation of turbulent conical diffuser flows using a non-orthogonal grid system, Computers & Fluids, 19(1991), 3-4, pp.347-361.
- Okhio, C.B., et al., The calculation of turbulent swirling flow through wide angle conical diffusers and the associated dissipative losses. International journal of heat and fluid flow, 7(1986), 1, pp.37-48.
- From, C.S., et al., Turbulent dense gas flow characteristics in swirling conical diffuser, Computers & Fluids, 149 (2017), pp.100-118.
- Jorgenson, F., How to measure turbulence with hot wire anemometers, Dantec Dynamics, 2004.
- Bilen, K., et al., Heat transfer from a plate impinging swirl jet, International journal of energy research, 26(2002), 4, pp. 305-320.
- Lefebvre, A.H., Gas turbine combustion. CRC press, 1998.
- Jeyachandran, K., Ganesan, V., Numerical modelling of turbulent flow through conical diffusers with the uniform and wake velocity profiles at the inlet, Mathematical and Computer Modelling, 10(1988), 2, pp. 87-97
- Ganesan, V., Flow and boundary layer development in straight core annular diffusers, International Journal of Engineering Science, 18 (1980), 2, pp. 287-304. Paper submitted: 17. August 2017. Paper revised: 12.October 2017. Paper accepted: 16. October 2017.