Aerothermal Performance of Streamwise and Compound Angled Pulsating Film Cooling Jets

Abstract

The quantification of aerothermal loss is carried out for streamwise and compound angled film cooling jets with and without large scale pulsation. This paper reports on the simultaneous measurements of the unsteady pressure and temperature field of streamwise and a 60 deg compound angled film cooling jet, both with a 30 deg surface angle over a flat plate with no pressure gradients. Turbine representative nondimensionals in terms of the geometry and operating conditions are studied. The main flow is heated more than the injected flow to have a temperature difference and hence a density ratio of 1.3, while the blowing ratio is maintained at 2. The entropy change, derived from pressure and temperature measurements, is calculated by using modified reference conditions to better reflect the losses in both the jet and the freestream. The effects of the periodic unsteadiness associated with rotating machinery are simulated by pulsating the jets. These effects are documented through time-resolved entropy change contours. Mass-averaged entropy and kinetic energy loss coefficients seem to be apt quantities for comparing the aerothermal performance of streamwise and compound angled injections. It is observed that the mass-averaged entropy loss of a streamwise jet doubles when it is pulsated, whereas that of a compound angled jet increases by around 50%. It may be conjectured from the measurements shown in this study that streamwise oriented jets suffer most of their entropy losses at the hole exit due to separation, whereas in compound angled jets, downstream thermal mixing between the jet and the freestream is the dominant mechanism. Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-3 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-7 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery OCTOBER 2009, Vol. 131 / 041015-9 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms 041015-10 / Vol. 131, OCTOBER 2009 Transactions of the ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 06/08/2015 Terms of Use: http://asme.org/terms

Experimental and Numerical Investigations of Effects of Flow Control Devices Upon Flat-Plate Film Cooling Performance

“…The heat transfer coefficient was normalized by the value of the turbulence heat transfer coefficient on flat plate of x/d=0 calculated by Eq. (14).…”

“…(12) . In order to evaluate the aerodynamic loss generated from cooling holes, the approach of Aga et al [14] was used and reference pressure P t,ref was defined.…”

Influence of streamwise position of crescent-shaped block on flat-plate film cooling characteristics

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“…Traditionally, the total pressure loss coefficient is used to indicate the aerodynamic loss. Assuming the mainstream flow and the coolant flow is mixed ideally, the total pressure of the mixing flow p t,mix can be calculated as follow [22] where m c and m m are the mass flow rates of the coolant and the mainstream hot gas, respectively, p t,cin and p t,m are the…”

Investigations on the effect of different influencing factors on film cooling effectiveness under the injection of synthetic coolant

“…The results of Aga et al 9 showed that the pulsating jet had greater thermal mixing and changed the size of the jet. Due to the greater penetrating power near the hole and the effective blowing ratio change, the entropy loss of the jet pulsating along the flow was twice as large as the entropy loss of the stable jet.…”