A Shock Loss Model for Supersonic Compressor Cascades

Abstract

Loss models used in compression system performance prediction codes are often developed from the study of two-dimensional cascades. In this paper, compressible fluid mechanics has been applied to the changes in shock geometry that are known to occur with back pressure for unstarted operation of supersonic compressor cascades. This physics-based engineering shock loss model is applicable to cascades with arbitrary airfoil shapes. Predictions from the present method have been compared to measurements and Navier–Stokes analyses of the LO30-4 and L030-6 cascades, and very good agreement was demonstrated for unstarted operation. A clear improvement has been demonstrated over previously published shock loss models for unstarted operation, both in the accuracy of the predictions and in the range of applicability. The dramatic increase in overall loss with increasing inlet flow angle is shown to be primarily the result of increased shock loss, and much of this increase is caused by the detached bow shock. For a given Mach number, the viscous profile loss is nearly constant over the entire unstarted operating range of the cascade, unless a shock-induced boundary layer separation occurs near stall. Shock loss is much more sensitive to inlet Mach number than is viscous profile loss.

Performance prediction of transonic axial compressor based on streamline curvature method

“…Recent investigations (Konig et al [18,19], Bloch [20]) have shown that the efficiency characteristic of high ( 1)…”

Application of an Analytical Method to Locate a Mixing Plane in a Supersonic Compressor

“…Once again, the major drawbacks of this method are that it gives wrong predictions for lower Mach numbers and that the shock formulas which are used in it are very sensitive. This is maybe one of the reasons why Bloch et al [12] had to take into account an "effective" leading edge radius in their model dedicated to predict the shock loss through the lower branch of Moeckel's hyperbola, in supersonic compressor cascades operating in unstarted regime. Indeed, they increased the leading edge thickness until the analytical results matched the experimental ones.…”

“…[10,11], for example. Bloch, Copenhaver and O'Brien also give an interesting approach based on Moeckel's method [12], adapted to unstarted regime.…”

“…To compare properly the two curves families, it would be necessary to take from the Navier-Stokes simulations only the shock loss, as done in Ref. [12] by subtracting the friction loss from measurements.…”

An Improved Streamline Curvature Approach for Off-Design Analysis of Transonic Axial Compression Systems

“…The weekly luncheons, occasional "turoboguys' nite out," and other get-togethers provided welcome relief from academic woes. (Konig, et al, 1996) .... (Bloch, et al, 1999).......... (Billet, et al, 1988) (Hah, et al, 1998) (Miller, et al, 1961)....... Figure 3 -4 Contours of tip relative total pressure loss coefficient near rotor trailing edge (Lakshminarayana, et al, 1985). (NASA SP-36, 1965) ............................................................................................................…”