Volume 37, Issue 2 -

A combined flow control method based on positively bowed blade and endwall vortex generator jet (VGJ) was performed to a compressor cascade under three kinds of inlet conditions. The results show that the endwall VGJ can further decrease the total losses in positively bowed cascades. At 0° incidence with zero inlet boundary layer, the separation type in the positively bowed blade is open, with the VGJ, the loss reduction is 2.7 %. As the inlet boundary layer thickens at 0° incidence, the separation region increases with the separation type keeping unchanged, the loss reduction increasing to 11.73 %. As the incidence rises to +7° with zero inlet boundary layer, the separation type converts into closed and the flow separation is the severest in the three cases, with the VGJ, however, the loss reduction is just 7.4 %, which means that the control effect of endwall VGJ not only depends on the size of separation region but also relies on the type of separation mode. If the separation type is open, as the size of separation region expands, the control effectiveness of endwall VGJ increases; if the separation type converts into closed with the further aggravation of flow field, that control effect will decrease.

A widely applicable and variable geometry 2-D rocket based combined cycle (RBCC) inlet characterized by the dual-duct design is conceptually put forward. The inlet operates as dual-duct status in the low Mach range (0~4), and transits to single-flowpath status in the following high Mach range (4~7). It accomplishes operational status transition through an 8.0-degree ramp rotation and a 4.0-degree cowl rotation at Mach 4. Through numerical simulations on typical flight Mach numbers, the observed starting Mach number is 2.2, which provides a sufficient operational window for a smooth ejector-to-ramjet mode transition. The RBCC inlet achieves comprehensive high mass capture coefficients in the overall wide flight range, especially in the low speed regimes. Suitable Mach numbers satisfying various combustion requirements in different modes together with high total pressure recovery coefficients are also obtained since the physical throat areas, compression angles, and the corresponding contraction ratios can be adjusted by a large margin through very limited rotations. The variable geometry scheme is not only feasible for practical realizations, but is also simple to arrange the dynamic sealing issues in a low-temperature environment in the RBCC engine.

The need of improved cooling effectiveness for hot components in jet engines has led to new designs of afterburner liners. In the present paper, experiments were performed to reveal the cooling characteristics and flow loss of various sinusoidal corrugated liners for an advanced afterburner. It is found that there are alternate high temperature and low temperature zones corresponding to the wave crests and troughs of the corrugated liner, respectively. Compared to the flat liner, the corrugated liner increases cooling effectiveness by 10 % at the blowing ratio of 0.5, by 4.5 % at the blowing ratio of 3.2. However, the difference in discharge coefficients for these two kinds of liners is only 4.3 %. The increased opening ratio of film holes from 1.42 % to 3.72 % for corrugated liners is able to improve the cooling effectiveness by 9.8 %. However, the discharge coefficient is decreased by 34.1 %. The augment of amplitude of liners can enhance the ram effect of cooling air, which has an advantage to increase the local blowing ratio, and to form good cooling film at the windward of wave troughs. The flow loss is bigger while the cooling effectiveness is enhanced due to the change of amplitude of the liner.

Fan blade is one of the key parts used in aircraft engine and its failure is mainly caused by fatigue fracture. This paper aims to predict fatigue life of fan blade during its service operation. First, the effective load and stress of fan blade are obtained by using finite element analysis and simulation. Second, the fatigue notch factor of fan blade is determined by using the nominal stress method. Then, the material properties of fan blade are used to correct and obtain the S−N$S - N$ curve of fan blade. Finally, according to the actual load spectrum of three working loading cycles in 900h, the Miner’s damage accumulation rule is employed to predict the fatigue life of fan blade.

For a radial turbine with vaneless volute, the inflow of turbine rotor usually has a circumferential flow distortion due to the influence of the volute tongue. The rotating blades of the rotor are exposed to harmonic aerodynamic loads caused by the distortion, which may induce rotor resonance and lead to high cycle failures (HCF). To understand the forced response mechanism clearly, a numerical analysis was carried out based on a fluid structure interaction (FSI) method. The pressure functions were extracted from the results of a computational fluid dynamics (CFD) analysis by Fourier decomposition. The first three harmonic pressures were identified as the primary engine order (EO) excitations and imposed on the structural model for computational structural dynamics (CSD) simulation. The quantification and assessment of the rotor response were attained by mode superposition method. The simulation results are shown to be consistent with the predictions of Singh’s advanced frequency evaluation (SAFE) diagram.

Considering the asymmetry of the low pressure turbine blade (LPT) wake at a low Reynolds number, the influence of asymmetric wakes which are similar to LPT wakes on the boundary layer of downstream blade rows in the near field is studied in the present paper, in order to increase wake flow prediction accuracy of the downstream blade without increasing the difficulty of the experiment or calculation load. Packb high-lift LPT airfoil was studied with CFX software. Following the analysis of the similarities between the wake generated by the cylinder bar and the triangle bar and the LPT blade wake in the near-field, the boundary layer flow characteristics on the suction surface under the different wakes were compared. In this research, it was found that the wakes of biased triangle bar shared more similarities with the LPT blade wake in the near field than the cylinder bar. Furthermore, the biased triangle bar wake was asymmetrical in terms of its centerline, and the separation bubble was suppressed while the calming effect was reduced after the wake-induced transition due to the asymmetry. And the time-averaged momentum thickness decreased by 7 % compared to the cylinder wake.

This paper deals with the performance analyses of exergetic, exergoeconomic, sustainability and environmental damage cost for J85 turbojet engine at Idle (ID), Intermediate (INT), Military (MIL) and Afterburner (AB) operation modes. The exergetic efficiency of whole engine is calculated to be 0.24 % at ID, 18.67 % at INT, 29.81 % at MIL and 22.77 % at AB modes, respectively. The unit exergy cost of product is accounted to be 30,423.94 $/GJ at ID, 269.35 $/GJ at INT, 121.47 $/GJ at MIL and 133.47 $/GJ at AB modes. The sustainable cost index is found to be 30,350.92 $/GJ at ID, 224.45 $/GJ at INT, 85.26 $/GJ at MIL and 103.0 $/GJ at AB modes while the sustainability index is obtained to be 1.0 at ID, 1.2 at INT, 1.43 % at MIL and 1.3 at AB modes. On the other hand, the environmental damage cost rate of engine are calculated to be 180.22 $/h at ID, 271.34 $/h at INT, 657.95 $/h at MIL and 1992.55 $/h at AB modes while the total cost rates of engine are determined to be 974.07 $/h at ID, 1357.15 $/h at INT, 2641.76 $/h at MIL and 6573.04 $/h at AB modes, respectively. The results indicate that J85 engine operates the exergetic-efficiently and cost-effectively at MIL mode.

Increasing the blade loading of a low pressure turbine blade decreases the number of blades, thus improving the aero-engine performance in terms of the weight and manufacture cost. Many studies focused on the blade-to-blade flow field of ultra-high lift low pressure turbines. The secondary flows of ultra-high lift low pressure turbines received much less attention. This paper investigates the secondary flows in an ultra-high lift low pressure turbine cascade T106C by large eddy simulation at a Reynolds number of 100,000. Both time-averaged and instantaneous flow fields of this ultra-high lift low pressure turbine are presented. To understand the effects of the inlet angle, five incidences of ‒10°, ‒5°, 0, +5° and +10° are investigated. The case at the design incidence is analyzed first. Detailed data is used to illustrate the how the fluids in boundary layers develops into secondary flows. Then, the cases with different inlet incidences are discussed. The aerodynamic performances are compared. The effect of blade loading on the vortex structures is investigated. The horseshoe vortex, passage vortex and the suction side corner vortex are very sensitive to the loading of the front part of the blade.