Safety Analysis of Flow Parameters in a Rotor-stator Cavity

AbstractIn order to ensure the safety of engine life limited parts (ELLP) according to airworthiness regulations, a numerical approach integrating one-way fluid structure interaction (FSI) and probabilistic risk assessment (PRA) is developed, by which the variation of flow parameters in a rotor-stator cavity on the safety of gas turbine disks is investigated. The results indicate that the flow parameters affect the probability of fracture of a gas turbine disk since they can change the distribution of stress and temperature of the disk. The failure probability of the disk rises with increasing rotation Reynolds number and Chebyshev number, but descends with increasing inlet Reynolds number. In addition, a sampling based sensitivity analysis with finite difference method is conducted to determine the sensitivities of the safety with respect to the flow parameters. The sensitivity estimates show that the rotation Reynolds number is the dominant variable in safety analysis of a rotor-stator cavity among the flow parameters

Transient analysis of volume packing effects on turbofan engine

AbstractAn integrated turbofan model, capable of coupling engine performance prediction with air-system calculation, is established. Efforts are focused on predicting volume packing effects on turbofan engine both in acceleration and in deceleration process. Results show that the volumes in secondary air-system exert more impacts on transient loads, compared with those in main gas path. Due to disk cavities in air-system, the percentages of coolant flow for the turbines are significantly reduced in acceleration manoeuvre, which result in potential adverse transient thermal load on the engine

Time-triggered State-machine Reliable Software Architecture for Micro Turbine Engine Control

AbstractTime-triggered (TT) embedded software pattern is well accepted in aerospace industry for its high reliability. Finite-state-machine (FSM) design method is widely used for its high efficiency and predictable behavior. In this paper, the time-triggered and state-machine combination software architecture is implemented for a 25 kg thrust micro turbine engine (MTE) used for unmanned aerial vehicle (UAV) system; also model-based-design development workflow for airworthiness software directive DO-178B is utilized. Experimental results show that time-triggered state-machine software architecture and development method could shorten the system development time, reduce the system test cost and make the turbine engine easily comply with the airworthiness rules

Leakage current simulations of Low Gain Avalanche Diode with improved Radiation Damage Modeling

We report precise TCAD simulations of IHEP-IME-v1 Low Gain Avalanche Diode (LGAD) calibrated by secondary ion mass spectroscopy (SIMS). Our setup allows us to evaluate the leakage current, capacitance, and breakdown voltage of LGAD, which agree with measurements' results before irradiation. And we propose an improved LGAD Radiation Damage Model (LRDM) which combines local acceptor removal with global deep energy levels. The LRDM is applied to the IHEP-IME-v1 LGAD and able to predict the leakage current well at -30 $^{\circ}$C after an irradiation fluence of $\Phi_{eq}=2.5 \times 10^{15} ~n_{eq}/cm^{2}$. The charge collection efficiency (CCE) is under development

NUMERICAL INVESTIGATION OF THE ROTATION ON THE FILM COOLING OVER A FLAT SURFACE

ABSTRACT A computational analysis was carried out to comprehend the mechanism of rotation on the film cooling which is important in understanding the mixing process between the film coolant and the hot stream air over the high pressure turbine blades. In this paper, a simple flat surface with a vertical film cooling hole was positioned parallel to the hot main stream and different rotating orientations were selected to simulate the blade pressure or suction sides. A polar coordinate frame was used with the center of the film cooling hole center as the origin point and three parameters S/D, the polar angle and either the adiabatic effectiveness or heat transfer coefficient could be chosen as the control parameters to produce a 2D graph of the effective film cooling areas. The rotation effects were clearly shown with the effective film cooling area graphs. The effective film cooling area was reduced with the rotating speed increasing. INTRODUCTION Film cooling is a cooling technique currently receiving wide application on the high temperature turbines. Although many parameters affecting film cooling have been intensively investigated, there are few studies on the rotation effects. Dring et al. (1980) were among the earliest to study film-cooling performance in a low-speed rotating facility. The rotating speed was about 405rpm. The existence of the radial component of the film coolant was found to have a strong impact on the nature of the effectiveness distribution. Abhari and Epstein (1994) presented the time-resolved measurements of heat transfer on a fully cooled transonic turbine stage in a short duration turbine test facility. Rotor speed was 6190rpm. The suction surface rotor heat transfer was lower than that measured in the cascade. High blowing ratios were shown to provide much less effective cooling than lower ones. Takeshi et al. (1991) used a heat-mass transfer analogy to measure the film cooling effectiveness on a low-speed stationary cascade and the rotating blade with the speed 6260rpm. A low level of effectiveness appeared on the pressure surface of the rotating blade compared to that on the stationary blade. Garg and co-workers (1997) performed the studies of the effect of blade rotation on the adiabati

FHA method for VBV position control function of FADEC system based on aero-engine dynamic model

AbstractTraditional Functional Hazard Assessment (FHA) method is hard to identify those engine effects which lack of visualization. In order to solve this problem, this paper develops a model-based FHA method for Variable Bleed Valve (VBV) position control function, performs two groups of simulations by using aero-engine dynamic model, and introduces an exemplary FHA for VBV position control function based upon simulation results. The application of this method shows that it is feasible and effective

An Investigation into the Flow of Rotating Orifices with Euler Angle and the Calculation Model of Discharge Coefficient Considering the Effect of Comprehensive Incidence Angle

As a typical flow element in an aero-engines, orifices play a vital role in the distribution and control of the mass flow rate within the secondary air system. In particular, rotating orifices with complex geometry (Euler angles) may significantly vary the discharge coefficients. Understanding the discharge coefficients of these orifices may guarantee a more reasonable distribution of the internal flow within the air system. This contributes to the safety, reliability, and structural integrity of the aero-engine under the all-inclusive line. In this paper, the flow state within the orifice and the discharge coefficient have been studied under the condition of different Euler angles (α0=0–30° and β0=0–30°) and rotational speeds (0–10,000 r/min). The comprehensive incidence angle is proposed to describe the combined effect of Euler angles and rotation. The correlation between the discharge coefficient and the comprehensive incidence angle is also given. At the same time, a general calculation model of the orifices is established considering the effect of the comprehensive incidence angle. The results indicate that the effects of the circumferential inclination angle, radial inclination angle, and rotation may be more clearly expressed by the comprehensive incidence angle. The larger discharge coefficient is obtained when the comprehensive incidence angle is close to 0, and under the fixed rotational speed and flow condition, the maximum discharge coefficient can be obtained by arranging the appropriate Euler angle for the orifice. Compared with the experimental results in the published literature, the calculation results of the model have an overall error of less than 6%. The calculation accuracy is high enough for the one-dimensional simulation of the secondary air system

Effect of Hot Streak on Aerothermal Performance of High Pressure Turbine Guide Vane under Different Swirl Intensities

In advanced civil aero-engine, the gas exiting combustor typically features hot streak (HS) and swirl that affect the aerothermal performances of the high pressure (HP) nozzle guide vane (NGV). The purpose of this paper is to study the influences of HS on HP NGV aerothermal behaviors under swirl with various intensities. The numerical investigations were conducted on the first NGV of GE-E3 HP turbine. Four swirl intensities (|SN| = 0, 0.25, 0.50, 0.75) and two swirl orientations (positive and negative) were considered. The result indicates that the relative strengths between the swirl and its induced radial pressure gradient dominate the flow patterns on vane surfaces. Thus, the diverse streamlines distributions appear on the surfaces and the dominated factor on each surface does not vary with swirl intensity. The swirl redistributes the cold and hot fluid and thus generates the relatively hot oblique strip and cold region at the upstream of vane. The heat load on the vane that is not directly impinged by HS is dictated by the radial migration of the fluids originating from the regions aforementioned at |SN| = 0.25 and 0.50. However, at |SN| = 0.75, the transverse movement of HS due to the intense swirl causes additional thermal load. The heat load on the vane that faces HS is mainly determined by the radial migration of HS. The swirl alters the heat transfer distribution on vane surfaces remarkably. With positive swirl, the heat transfer coefficients at the lower span of suction side and pressure side are enhanced and weakened respectively. As expected, the opposite trends are observed in the negative swirl case. Swirl also affects boundary layer transition, and then affecting heat transfer. Positive and negative swirls both advance the transition on the suction side of vane directly impinged by the swirl, and with the increase of swirl intensity, transition onset shifts toward upstream

A new approach to simulate the fluid network of unsteady flow

In this paper, a newly deduced numerical method is originally applied to solve the complicated transient fluid network in the engine and with that method a new program called UFSSP (Unsteady Fluid Network System Simulation) is developed. As a case study, the UFSSP has been applied to pressurization of a propellant tank, which has been provided a published correlation and numerically predicted by the advanced program in this field called General Fluid System Simulation Program (GFSSP) by NASA's Marshall Space Flight Center (MSFC). Comparisons among the numerical results of the UFSSP, those published data of the GFSSP and the results from the published correlation are presented. It is found that the numerical results of the UFSSP model are in better agreement with the results from the published correlation than those achieved from the GFSSP model. Furthermore, the proposed method leads to an improved computational algorithm and, as a consequence, a significant stability of the computation

Suitability of Three Different Two-equation Turbulent Models in Predicting Film Cooling Performance Over a Rotating Blade

The suitability of three different two-equation turbulence models in predicting film cooling effectiveness on a rotating blade was investigated and they are the commonly used standard k-ε model, the k-ω model and the shear stress transport k-ω model. To fulfill this target, both numerical simulation and the experimental investigation were carried out for a rotating blade having a flat test surface with a 4 mm diameter straight circular cooling hole in 30° inclined injection. The blade rotated at five different speeds of 0, 300, 500, 800 and 1000 rpm. The momentum ratio was set to be 0.285 and the Reynolds (ReD) number based on the mainstream velocity and hydraulic diameter of the mainstream channel is 1.45 × 105. The averaged density ratio was chosen to be 1.026 with air as both the coolant and the mainstream. Comparison between the numerical work and the experimental results indicated that (1) the rotating speed is the most critical parameter influencing the film cooling effectiveness distributions and the pressure surface could be remarkably different from the suction surface, (2) as for the algebraic averaged film cooling effectiveness, numerical predictions of the three turbulence models all overshoot compared with the experimental results, (3) among the three turbulence models, the standard k-ε model gave the poorest prediction