This paper studied an array impingement cooling with different temperature initial crossflow. Both the heat transfer and flow field of impingement cooling with four crossflow-to-jet temperature ratios (TR=1.0, 1.1, 1.2, 1.3) under four crossflow-to-jet mass flow ratios (CMFR=0.3, 0.5, 0.7, 0.9) and four jet Reynolds numbers (Rej=15,000, 25,000, 35,000, 45,000) are investigated. Results show that (1) as the Rej increases, the Nusselt number increases, but the friction loss coefficient decreases; (2) as the CMFR increases, Nusselt number and friction loss coefficient decrease; (3) as the TR increases, the Nusselt number always decreases, but the variation of friction loss coefficient is related to CMFR. To be specific, when the CMFR are 0.3 and 0.5, the friction loss coefficient decreases with the increase of TR, but when the CMFR are 0.7 and 0.9, it increases as the TR increases. The research results will clarify the effect mechanism of TR on impingement cooling.

View full abstract

In this study, an assessment of the performance of an industrial gas turbine during compressor fouling conditions is undertaken. The assessment is carried out through performance diagnostic and prognostic methods. The diagnostic technique identifies and isolates faults in the components of the gas turbine, and considers the health parameter of the compressor (efficiency). The remaining useful life of the compressor is estimated by a degradation model that also considers the compressor efficiency health index. Compressor efficiency is estimated using a gas turbine real-time executable digital-twin. The digital-twin is integrated within a gas turbine system operating in the field. Data processing of the compressor efficiency is required to obtain a meaningful trend of the compressor health index. Results demonstrate that the diagnostic and prognostic methods applied to the problem of compressor health parameter estimated by the digital-twin can be a powerful tool to initiate maintenance actions on associated axial compressors prior to significant performance deterioration.

View full abstract

Jet impingement is widely used in different cooling applications. The accumulation of crossflow as the spent air migrates downstream causes a decay in the overall cooling performance. This study aims to mitigate the undesirable crossflow effects by attaching the so-called-crossflow diverters. Cylindrical, rectangular, and ribbed diverter shapes are numerically studied within a 25-jet array for a range of Rej of up to 10,000. Diverter heights of 3 mm (QL), 6 mm (HL), and 9 mm (TQL), as a percentage of jet-to-target spacing (12 mm) are considered with a constant heat flux condition. Results show an increased Nu from 6.6% to 12%. However, the associated friction factor is also increased by 9.9% – 24.3% on average compared to the baseline model. Consequently, results show a net enhancement of up to 5.2%, 3.1%, and 3.8% for cylindrical, rectangular, and ribbed-type diverters, respectively according to the heat transfer performance parameter (η).

View full abstract

Under the realistic running conditions of gas turbines, the temperature at mainstream inlet is always non-uniform due to the effects of combustion process, and different types of hot streak (HS) could be found at the inlet. The existence of HS may result in some potential negative impacts on the cooling performances of vane leading edge (LE). Nowadays, the two configurations, i.e., traditional showerhead film cooling (SFC) and novel double wall cooling (DWC), have been widely used in LE designs of turbine vanes, but until now there is no comprehensive study to evaluate the two models considering HS effects. In this work, using the two cooling structures, four different temperature profiles are considered at the mainstream inlet of the cascade. The results reveal that: in both models, HS could cause a local high-temperature region on LE, and the thermal characteristics of this area are dependent on HS pattern. Compared to SFC, DWC shows a better cooling ability and a lower thermal stress on the vane surface. The cooling characteristics in DWC model are less sensitive to the HS pattern. However, the problem of the extremely high thermal stress within the pin-fins of DWC should be carefully considered.

View full abstract

Distributed propulsion configurations are a promising concept for future aircraft systems. The main objective of the presented experiment is to investigate propeller-wing interactions in detail. An understanding of the interactions is deducted from the experiment. Furthermore, a data basis for numerical studies is created. In the work presented, the interaction between adjacent propellers as well as the two-way interaction of wing and propellers is studied. The designed wind tunnel model features a two element wing c = 0.8 m with three co-rotating propulsion units with a diameter of DP = 0.6 m or DP = 0.4 m. They are mounted on a separate carrier, which is installed in the test section of the Propulsion Test Facility, TU Braunschweig. The outboard sections generate periodic boundary conditions, whereas the centre wing and propeller are subject of analysis. Both the centre wing and the centre propeller are instrumented for force and moment measurements. The flap of the wing is freely adjustable. The detached setup of wing and propeller allows a variable adjustment of the relative propeller position to the wing. This feature allows the propeller to be moved in all directions. In this work the position varies from horizontally −0.489 < x/c < −0.114, vertically −0.2 < z/c < 0 and spanwise 0.075 < y/c < 0.375 in small increments. The effect of the wings upstream flow field on the propeller is compared and analyzed for different positions. In addition to the relative position, three different propeller blades are investigated, which differ in size and design. While two blades were designed for minimum induced losses, a third set of blades was designed for homogeneous induced velocity. A comparison for the isolated propeller and the DP configuration is shown. The thrust level is varied by blade pitching.

View full abstract

To design a low-emission hydrogen-fired gas turbine combustor, prevention of flashback is one of key issues. However, the detailed measurement of flashback is difficult and expensive, especially at the actual operation condition. Therefore, the high-precision numerical simulation technology is important to study the mechanism and countermeasures of flashback. In this study, a large eddy simulation (LES) using a non-adiabatic flamelet-generated manifold (NA-FGM) approach, considering the effects of heat loss, is applied to simulate hydrogen-air premixed flame propagating in a rectangular channel. Then, the validity of predicting flashback limits is examined. The results show that the NA-FGM approach quantitatively well captures the flashback limits variation observed in the experiments. This indicates that accounting for the influence of heat loss is crucial in achieving precise prediction of the flashback in developing a low-emission hydrogen gas turbine combustor.

View full abstract

This work delves into the design and operation of a series/parallel partial hybrid-electric architecture for regional aircraft. Employing a comprehensive approach, this study leverages mission-level analysis to optimize a 19-passenger hybrid-electric aircraft. The conceptual design framework employed is based on the OpenConcept library, and a systematic computational scheme is developed to effectively investigate the concept’s performance, utilizing the supplied and shaft power ratios. Through the examination of three distinct mission ranges and consideration of two technological scenarios, this work offers valuable insights. For the longest mission, an aircraft design optimization problem is posed, and a 23% reduction in total energy consumption is achieved for the optimistic technological scenario. On the other hand, the focus shifts to optimize the power management for shorter missions, where a 26% and a 32% reduction in energy consumption are achieved for the typical and short missions. The results highlight the potential of hybrid-electric propulsion for regional aircraft.

View full abstract