Journal of Engineering for Gas Turbines and Power

Journal Information
ISSN / EISSN : 0742-4795 / 1528-8919
Published by: ASME International (10.1115)
Total articles ≅ 6,468
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Zonghan Sun, Jie Tian, , Zhaohui Du, Hua Ouyang
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052429

Abstract:
A noise reduction method for axial flow fans using a short inlet duct is proposed. The pattern of noise reduction imposed by the short inlet duct on the axial flow cooling fan under variable working conditions was experimentally and numerically examined. A 2-cm inlet duct was found to reduce tonal noise. As the tip Mach number of the fan increased from 0.049 to 0.156, the reduction in the total average sound pressure level at 1 m from the fan increased from 0.8 dB(A) to 4.3 dB(A), and further achieved 4.8 dB(A) when a 1-cm inlet duct was used. The steady CFD showed that the inlet duct has little effect on the aerodynamic performance of the fan. The results of the unsteady calculation showed that the suction vortexes move upstream to weaken the interaction with the rotor blades, which significantly reduces the pulsating pressure on the blades. The SPL at the BPF contributed by the thrust force was calculated to reduce by 36 dB at a 135° observer angle, reflecting the rectification effect of the duct on the non-uniform inlet flow. The POD of the static pressure field on the blades verified that the main spatial mode is more uniformly distributed due to the duct, and energy owing to the rotor-inlet interaction decreases. A speed regulation strategy for the cooling fan with short inlet duct is proposed, which provides guidance for the application of this noise reduction method.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052428

Abstract:
Rolling-element bearings (REB) can develop severe damage due to skidding (slipping) between the rolling elements and bearing races. Skidding can be described as gross sliding between the bearing surfaces in relative motion and can result in significant surface distress such as smearing, especially at light loads and high rotational speeds. Under these conditions, skidding occurs between the rolling elements and the bearing races, leading to increased wear (higher friction coefficient), elevated bearing temperature, significant power losses and reduced service life of the bearing. The main objective of this study is to investigate the significance of various sensing technologies (induction, vibration, ultrasound, acoustic and optical) in detecting skidding in standard series roller bearings as well as custom-made roller bearings for aero engine applications. The bearings have a bore diameter of 60 mm and 90 mm, respectively. Jet and under race lubrication techniques have been used to supply oil to the bearings under test. The custom-made aero engine test bearing features special channels to allow under race lubrication of the rollers/races contacts as well as the cage land. The effect of radial load, rotational speed and oil flow on roller skidding have also been investigated and analyzed. Tests have been performed on a dedicated high speed experimental bearing facility and data was recorded using a commercially-available data acquisition system.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052427

Abstract:
Geometric mistuning models formulated from a component mode synthesis methods often require the calculation of component modes, particularly constraint and fixed interface normal modes, during substructuring. For Integrally Bladed Rotors, these calculations are required for each sector. This paper proposes methods that reuse information garnered from solving the constraint modes of a single sector on the remaining sectors to reduce memory requirements and solution times. A mesh metamorphosis tool is used to ensure finite element models match geometry obtained from a 3D optical scanner. This tool also produces a common mesh pattern from sector-to-sector. This is exploited to produce common permutation matrices and symbolic factorizations of sector stiffness matrices that are proposed for reuse in solving subsequent constraint modes. Furthermore, a drop tolerance is introduced to remove small values during constraint mode calculation to reduce memory requirements. It is proposed to reuse this dropping pattern produced from a single sector on the remaining sectors. Approaches are then extended to a parallel processing scheme to propose effective matrix partitioning methods. Finally, information gathered during the constraint mode calculations are reused during the solution of the fixed interface normal modes to improve solution time. Results show reusing permutation matrices and symbolic factorizations from sector-to-sector improves solution time and introduces no error. Using a drop tolerance is shown to reduce storage requirements of a constraint mode matrix, while reusing the dropping pattern introduces minimal error. Similarly, reusing constraint mode information in calculating normal modes greatly improves the performance.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052430

Abstract:
The paper presents measurements of performance conducted on a copper pads bearing (C-PB) and a steel-pads bearing (S-PB). Both bearings have the same geometry and differ on the pads' backing material, copper vs. steel. The journal diameter D=102 mm, and a bearing has five pads with length L=0.4D, nominal radial clearance 0.064 mm. The bearings operate at four shaft speeds ranging from 6 krpm to 14 krpm and under multiple specific loads ranging from 0.17 MPa to 2.1 MPa. At the highest load (on pad) and low speed, the S-PB static eccentricity is up to 37% higher than that for the C-PB. The oil exit temperature rise is similar for both bearings, the maximum difference reaches 6 °C. For all operating conditions, the pads' peak temperature rise, having a maximum difference of 5 °C to 16 °C, is larger for the S-PB. The S-PB produces a ~ 5% lower drag power loss than that in the C-PB. From dynamic load test results, the C-PB direct stiffness KYY (along the load direction) is up to 30% higher than the S-PB stiffness, while the difference in KXX between the C-PB and the S-PB ranges from 60% to 90%. Similar to the stiffness results, the C-PB produces larger direct damping coefficients; CYY and CXX are up to 25% and 40% larger than those for the S-PB.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052424

Abstract:
Aircraft operators rely on gas path analysis techniques for monitoring the performance and health of their gas turbine engine assets. This is accomplished by analyzing discernable shifts in measurement parameters acquired from the engine. This paper reviews the founding mathematical principles of gas path analysis, including conventional approaches applied for estimating engine performance deterioration. Considerations for extending the application of gas path analysis techniques to Electrified Aircraft Propulsion (EAP) systems is also discussed, and simulated results from their application to an EAP concept comprised of turbomachinery and electrical system hardware is provided. Results are provided comparing the parameter estimation accuracy offered by taking a whole-system approach towards the problem setup versus that offered by analyzing each subsystem individually. For the latter, the importance of having accurate direct or inferred measurements of external mechanical torque loads placed upon turbomachinery shafts is emphasized.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052426

Abstract:
The growth of renewable energy source requires reliable, durable and cheap storage technologies. In this field, the Pumped Thermal Energy Storage (PTES), is drawing some interest as it appears not to be affected by geographical limitations and use very cheap materials. PTES is less efficient than pumped hydro and batteries, but it could achieve satisfactory efficiencies, show better economic performance and be characterized by negligible environmental impacts. A PTES stores the electric energy as thermal exergy in solid packed beds, by operating two closed Brayton cycles, one for charging and the other one for discharging. Although PTES thermodynamical behavior is well understood, the interaction between the components is rarely investigated. This study investigates the impact of packed-bed behavior on turbomachines operating conditions. In this way, PTES off-design and part-load performance are estimated. A control strategy especially suited for closed Brayton cycles, i.e. the inventory control, is used to control the system. As it resulted, PTES is characterized by an excellent part-load performance, which might be a significant advantage over the competing technologies. However, the off-design operation induced by the packed-bed thermal behavior might significantly reduce the system performance and, in particular, that of the discharge phase.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052425

Abstract:
Acoustic pyrometry is a widely used technique for contactless temperature measurement. It may be used in several applications, especially when high temperatures and harsh environments are involved. For instance, it has been applied to measure the temperature distribution at gas turbine outlet. This technique is based on the measurement of the time of flight of an acoustic wave through a medium. If multiple emitter-receiver couples are used, by using a computational procedure a reconstruction of a temperature map is possible. On the other hand, a full assessment of the robustness of this technique to potential errors in time of flight estimation is still missing. In this study, the impact of an inaccuracy in time of flight estimation on the reconstruction of a correct temperature map is investigated by means of a statistical approach. As a general result, it was found that when the time of flight was measured without inaccuracies, temperature estimation errors may be lowered by simply increasing the number of cells in which the estimation is performed. However, when the estimation of the time of flight is affected by errors, an optimal configuration exists that minimize the temperature estimation errors.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052382

Abstract:
Novel pressure gain combustion concepts invoke periodic flow disturbances in a gas turbine's last compressor stator row. This contribution presents studies of mitigation efforts on the effects of periodic disturbances on an annular compressor stator rig. The passages were equipped with pneumatic active flow control influencing the stator blade's suction side, and a rotating throttling disc downstream of the passages inducing periodic disturbances. For steady blowing, it is shown that with increasing actuation amplitudes $c_\mu$, a hub corner vortex's extension deteriorating the suction side flow can be reduced, resulting in an increased static pressure rise coefficient~$C_p$ of a passage. The effects of the induced periodic disturbances could not be addressed, by using steady blowing actuation. Considering a corrected total pressure loss coefficient $\zeta^*$, which includes the actuation effort, the stator row's efficiency decreases with higher $c_\mu$. Therefore, a closed-loop approach is presented to address the effects of the disturbances more specifically, thus lowering the actuation effort. For this, a Repetitive Model Predictive Control (RMPC) was applied, taking advantage of the disturbance's periodic nature. The presented RMPC formulation is restricted to a binary control domain to account for the used solenoid valves' switching character. An efficient implementation of the optimization within the RMPC is presented, which ensures real-time capability. As a result, $C_p$ increases in a similar magnitude but with a lower actuation mass flow of up to 66\,\%, resulting in a much lower~$\zeta^*$ for similar values of $c_\mu$.
Yuxuan Dong, ,
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052383

Abstract:
The exhaust diffuser with different struts was numerically calculated by solving three-dimensional Reynolds-Averaged Navier-Stokes (RANS). The flow process and flow loss mechanism in the diffuser were analyzed, the influence of two different structures of tapered struts on the aerodynamic performance of the exhaust diffuser under different inlet pre-swirls was explored, and the aerodynamic performance of the exhaust diffuser with tapered struts was compared with a conventional exhaust diffuser with linear struts. The results show that, compared with the conventional linear strut, under different inlet pre-swirls, two different tapered struts can both weaken the flow separation in the exhaust diffuser, thereby reducing the total pressure loss. When the inlet pre-swirl is greater than 0.35, the total pressure loss coefficient of the exhaust diffuser with structure-C tapered struts decreases by up to 0.07. The two types of tapered struts also change the flow structure at the exhaust diffuser outlet, which affects the uniformity of the outlet airflow, and then affect the static pressure recovery coefficient. Under different inlet pre-swirls, two types of tapered struts can be effective to increase the static pressure recovery coefficient of the exhaust diffuser, for the exhaust diffuser with structure-C tapered struts, the static pressure recovery coefficient can be increased by up to 0.065, relative increase of 20%. The research in this paper shows that the tapered structure can significantly improve the aerodynamic performance of the exhaust diffuser under different inlet pre-swirls.
Journal of Engineering for Gas Turbines and Power; https://doi.org/10.1115/1.4052385

Abstract:
The betterment of the turbine performance plays a prime role in all future transportation and energy production systems. Precise uncertainty quantification of experimental measurement of any performance differential is therefore essential for turbine development programs. In this paper, the uncertainty analysis of loss measurements in a high-pressure turbine vane are presented. Tests were performed on a stator geometry at engine representative conditions in a new annular turbine module called BRASTA (Big Rig for Annular Stationary Turbine Analysis) located within the Purdue Experimental Turbine Aerothermal Lab. The aerodynamic probes are described with emphasis on their calibration and uncertainty analysis, first considering single point measurement, followed by the spatial averaging implications. The change of operating conditions and flow blockage due to measurement probes are analyzed using CFD, and corrections are recommended on the measurement data. The test section and its characterization are presented, including calibration of the sonic valve. The sonic valve calibration is necessary to ensure a wide range of operation in Mach and Reynolds. Finally, the vane data are discussed, emphasizing their systematic and stochastic uncertainty.
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