Volume 37, Issue 4

To resolve the problem of low estimation accuracy of compressor characteristic parameters based on traditional Kriging model, an improved interpolation method of aircraft engine compressor characteristic parameters based on the Kriging algorithm is proposed. Considering the distribution feature of original data, a high dimensional model is built. By defining the relationship between input and output data, an unknown vector composed of characteristic parameters at a certain speed of nd$${n_d}$$ can be calculated based on the Kriging model. Furthermore, a sub-model is established by the calculated data and an unknown single target at the speed of nd$${n_d}$$ can be calculated. Adopt the compressor characteristic parameters of an engine to identify the feasibility of this method. Set the efficiency coefficients and flow coefficients as the unknown characteristic parameters. Simulation results illustrate that the proposed is effective and efficient.

The effect of conjugate heat transfer is investigated on a first stage nozzle guide vane (NGV) of a high pressure gas turbine which has both impingement and film cooling holes. The study is carried out computationally by considering a linear cascade domain, having two passages formed between the vanes, with a chord length of 228 mm and spacing of 200 mm. The effect of (i) coolant and mainstream Reynolds numbers, (ii) thermal conductivity (iii) temperature difference between the mainstream and coolant at the internal surface of the nozzle guide vane are investigated under conjugate thermal condition. The results show that, with increasing coolant Reynolds number the lower conducting material shows larger percentage decrease in surface temperature as compared to the higher conducting material. However, the internal surface temperature is nearly independent of mainstream Reynolds number variation but shows significant variation for higher conducting material. Further, the temperature gradient within the solid thickness of NGV is higher for the lower conductivity material.

In the present work, LBO limits for methane-air combustion stabilized by a V-Gutter have been predicted by a hybrid method using numerical simulation and empirical relations. The numerical simulations have been carried out to study the stable methane-air combustion and temperature gradients at exit and recirculation region in a model gas turbine afterburner with a planar V-Gutter as a bluff body for four inlet air pressure conditions and three V-Gutter angles. The calculated average exit gas temperature (AEGT) and the average gas temperature in recirculation region have been used for predicting the blowout conditions. An empirical method based on Feature Section Criterion has been used to determine Fuel-Air Ratio (FAR) at blowout conditions very accurately from the numerically calculated average temperature in the central recirculation zone (CRZ).The predicted Fuel-Air Ratio (FAR) at lean blowout conditions has been compared with the experimental results obtained for the same conditions and are found to be in good agreement.

Film cooling effectiveness downstream of one row of holes of 30 degree inclination angle was measured by using a steady-state thermochromic liquid crystal technique at blowing ratios of 0.5, 1.0, 1.5 and 2.0, respectively. Three kinds of dual-fanned holes which have the same expanded entrance width and the different expanded exit widths were tested. The configuration of only expanded entrance, but cylindrical exit hole, was tested to examine the effect of the expanded entrance on film cooling performance. The numerical simulation for the three expanded exit configurations was carried out explaining the mechanism of film cooling by the flow and thermal field. The only expanded entrance has a weak influence on film cooling effectiveness. The Wo=1.5d${W_o} = 1.5d$ configuration provides a lift of film cooling effectiveness compared to Wo=1.0d${W_o} = 1.0d$ configuration. Film cooling effectiveness is not sensitive to the change of configurations from Wo=1.5d${W_o} = 1.5d$ to Wo=2.0d${W_o} = 2.0d$. Film cooling effectiveness for Wo=2.5d${W_o} = 2.5d$ performs significantly better than the other configurations due to the presence of the anti-vortex. The effect of dual-fanned exit width on film cooling effectiveness is strongly dependent on the blowing ratios.

Performance seeking control benefits propfan engine by generating optimal performance in different flight status. It is based on engine model, control model and optimization model. The control scheme of propfan engine is different from those of turbofan engines, for the thrust of propfan engines is mainly produced by propfans. After analysing the control structure of propfan engines, a control scheme for the propfan engine is proposed. The control scheme works well in flight envelope and the simulation results show that the overshoot of power shaft rotation speed is less than 2 % and the settling time is less than 0.9s. Based on this, a control scheme in performance seeking mode is proposed. A Modified Cuckoo Search method, which modifies the search step size and abandonment rate, is applied in the control scheme in maximum thrust mode and minimum fuel flow mode. The control scheme in performance seeking mode can reduce 2 % fuel flow, compared with the control scheme in torque-compensation mode. Performance of the scheme is better than standard Cuckoo Search and Genetic Algorithm.

A hybrid-scheduling method, consisting of packing algorithm, genetic algorithm and priority promotion algorithm, was proposed for time-triggered CAN in this paper. We divided the basic cycles (BC) into synchronous phase for transmitting time-triggered messages and asynchronous phase for transmitting event-triggered messages. At the each end of BC, fault-tolerant windows were designed to improve the fault-tolerance. The First Fit Increasing and the genetic algorithm scheduled and optimized the transmission of time-triggered messages in the synchronous phase, and the priority promotion algorithm optimized the transmission of event-triggered messages in the synchronous phase. For the communication application of a TTCAN-based turbofan distributed control system, the new scheduling method improved the bandwidth utilization and arbitrary windows utilization to 99% and 9.3%.

A numerical study on the performance of synthetic jet for flow separation control on a high-speed compressor stator vane is performed. Four control schemes including full-span and part-span configurations are investigated at both design and off-design conditions. Results indicate that both full-span and part-span schemes could effectively delay flow separation and reduce total pressure loss for the compressor stator vane, the adaptability of the flow control under off-design conditions is also validated. Within the investigated incidence range, the full-span configuration is able to gain the most significant performance improvement, by which a maximum loss reduction of 23.8 % is obtained at i =2 deg. The part-span configuration could reorganize the vortex structures more efficiently and cut off the interaction between the ring-like vortex and the passage vortex, thus improving its performance in the corner region. In terms of flow control efficiency, the part-span configurations turn out to be more superior, where the highest control efficiency of 614.0 % is achieved at i =0 deg with the total height of the actuator being 40 % H . The flow control efficiency for all the schemes is higher than 100 % within the whole operating range, demonstrating a promising prospect for the application of synthetic jet in axial compressors.

A new geometry parametric method of winglet-cavity tip has been introduced in the optimization procedure based on three-dimensional steady CFD numerical calculation and analysis. Firstly, the reliability of numerical method and grid independency are studied. Then an aerodynamic optimization is performed in an unshrouded axial high pressure turbine with winglet-cavity tip. The optimum winglet-cavity tip has higher turbine stage efficiency and smaller tip leakage mass flow rate than the cavity tip and flat tip. Compared with the results of cavity tip, the effects of the optimum winglet-cavity tip indicate that the stage efficiency is improved effectively by 0.41% with less reduction of tip leakage mass flow rate. The variation of turbine stage efficiency with tip gap states that the optimum winglet-cavity tip obtains the smallest efficiency change rate ∆η/(∆τ/H). For the optimum winglet-cavity tip, the endwall flow and blade tip leakage flow pattern are used to analysis the physical mechanical of losses. In addition, the effects of pressure-side winglet and suction-side winglet are analyzed respectively by the deformation of the optimum winglet-cavity tip. The numerical results show that the pressure-side winglet reduces the tip leakage flow effectively, and the suction-side winglet shows a great improvement on the turbine stage efficiency.

One of the main functions of gas turbine monitoring is to estimate important unmeasured variables, for instance, thrust and power. Existing methods are too complex for an online monitoring system. Moreover, they do not extract diagnostic features from the estimated variables, making them unusable for diagnostics. Two of our previous studies began to address the problem of “light” algorithms for online estimation of unmeasured variables. The first study deals with models for unmeasured thermal boundary conditions of a turbine blade. These models allow an enhanced prediction of blade lifetime and are sufficiently simple to be used online. The second study introduces unmeasured variable deviations and proves their applicability. However, the algorithms developed were dependent on a specific engine and a specific variable. The present paper proposes a universal algorithm to estimate and monitor any unmeasured gas turbine variables. This algorithm is based on simple data-driven models and can be used in online monitoring systems. It is evaluated on real data of two different engines affected by compressor fouling. The results prove that the estimates of unmeasured variables are sufficiently accurate, and the deviations of these variables are good diagnostic features. Thus, the algorithm is ready for practical implementation.