Conceptual design and aerodynamic evaluation of hypersonic airplane with double flanking air inlets

To aim at design requirements of high lift-to-drag ratio as well as high volumetric efficiency of next generation hypersonic airplanes,a body-wing-blending configuration with double flanking air inlets layout is presented.Moreover,a novel forebody design methodology which by rotating and assembling two waverider-based surfaces is firstly introduced in this paper.Some typical configurations are designed and their aerodynamic performances are evaluated by computational fluid dynamics.The results for forebodies analysis show that large volumetric efficiency,high lift-to-drag ratio,and uniformly distributed flowfield at the inlet cross section can be assured simultaneously.Furthermore,results of numerical simulation of four integrated configurations with various leading edge shapes,including three power-law curves and a cosine curve clearly show the advantage of high lift-to-drag ratio.Besides,the high pressure generated by the side wall of the airframe can be partly captured by the reasonably designed wings in the condition of small flight attack angle.Then the order of lift-to-drag ratio of four configurations at 0 degree flight attack angle is completely different from the condition of 4-degree flight attack angle.This result demonstrates that the curve shape of the leading edge is very important for the lift-to-drag ratio of the aircraft,and it should be further optimized under the cruising attack angle in future work.

THREE-DIMENSIONAL REGULARITIES OF DISTRIBUTION OF AIR-INLET CHARACTERISTIC VELOCITY IN NATURAL-DRAFT WET COOLING TOWER

A model for heat and mass transfer in a natural-draft wet cooling tower was established. Numerical simulation with the κ-ε turbulent model was conducted. Distribution rules of air inlet aerodynamic field were studied. Field experiments were done in a cooling tower in power plant, and the test data was compared with the related results. The definition of characteristic air velocity was proposed and its influencing factors, such as the cross-wind velocity and circumferential angle, were quantitatively studied. It can be used to evaluate the performance of cooling tower and to calculate the ventilation quantity and resistance of air inlet. It is also a theoretical basis for cooling tower design and performance optimization.

Effects of supply air temperature and inlet location on particle dispersion in displacement ventilation rooms

The effects of supply temperature and vertical location of inlet air on particle dispersion in a displacement ventilated （DV） room were numerically modeled with validation by experimental data from the literature. The results indicate that the temperature and vertical location of inlet supply air did not greatly affect the air distribution in the upper parts of a DV room, but could significantly influence the airflow pattern in the lower parts of the room, thus affecting the indoor air quality with contaminant sources located at the lower level, such as particles from working activities in an office. The numerical results also show that the inlet location would slightly influence the relative ventilation efficiency for the same air supply volume, but particle concentration in the breathing zone would be slightly lower with a low horizontal wall slot than a rectangular diffuser. Comparison of the results for two different supply temperatures in a DV room shows that, although lower supply temperature means less incoming air volume, since the indoor flow is mainly driven by buoyancy, lower supply temperature air could more efficiently remove passive sources （such as particles released from work activities in an office）. However, in the breathing zone it gives higher concentration as compared to higher supply air temperature. To obtain good indoor air quality, low supply air temperature should be avoided because concentration in the breathing zone has a stronger and more direct impact on human health.

Numerical study on the propagation characteristics of forward smoldering in a cellulosic packed bed

Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented for the smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes include pyrolysis and oxidation degradation of fuel and oxidation of char. Heat transfer between solid and gas is taken into account, and the diffusion coefficient varies with the temperature. Radiative heat transfer is included by using the diffusion approximation. The effects of airflow velocity and oxygen concentration are simulated on the smoldering velocity and the averaged maximum temperature of smoldering fuel. The results indicate that the spread rate varies linearly with increasing airflow velocity, and the inlet air velocity has little effect on the maximum temperature. The evolutions of gas species and solid compositions are predicted. The effects of frequency factors （A1, A2 and A3） are analyzed. Simulations show that the smoldering spread rate increases with increasing A2 （fuel oxidation）, but decreases with A1 （fuel pyrolysis） and A3 （char oxidation）.

Improvement of part-load performance of gas turbine by adjusting compressor inlet air temperature and IGV opening

A novel adjusting method for improving gas turbine(GT)efficiency and surge margin(SM)under partload conditions is proposed.This method adopts the inlet air heating technology,which uses the waste heat of lowgrade heat source and the inlet guide vane(IGV)opening adjustment.Moreover,the regulation rules of the compressor inlet air temperature and the IGV opening are studied comprehensively to optimize GT performance.A model and calculation method for an equilibrium running line is adopted based on the characteristic curves of the compressor and turbine.The equilibrium running lines calculated through the calculation method involve three part-load conditions and three IGVopenings with different inlet air temperatures.The results show that there is an optimal matching relationship between IGV opening and inlet air temperature.For the best GT performance of a given load,the IGV could be adjusted according to inlet air temperature.In addition,inlet air heating has a considerable potential for the improvement of part-load performance of GT due to the increase in compressor efficiency,combustion efficiency,and turbine efficiency as well as turbine inlet temperature,when inlet air temperature is lower than the optimal value with different IGV openings.Further,when the IGV is in a full opening state and an optimal inlet air temperature is achieved by using the inlet air heating technology,GT efficiency and SM can be obviously higher than other IGVopenings.The IGV can be left unadjusted,even when the load is as low as 50%.These findings indicate that inlet air heating has a great potential to replace the IGV to regulate load because GT efficiency and SM can be remarkably improved,which is different from the traditional viewpoints.

Gas Turbine Operation Offshore： Online Compressor Wash Operational Experience

Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load （T5.4-control）, hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field＇s production and economy. The performance and operational experience with on-line wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line wash are given. This work is based on long-term operation with on-line wash, where operational data are collected and performance analyzed, over a 4-5 year period. All engines are operated with four-month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load （i.e., normal operating load for the subject engine）. To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line wash. It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine＇s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed. Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.

Engineering Solutions towards Cost-Effective Sustainable Environment and Living

One important area where the development of economically viable products can improve the quality and comfort of human existence is natural ventilation inside a building. Despite the wide distribution of air pollutant sources, the concentration of indoor pollutants may be the dominant risk factor in relation to personal exposure, as most people spend an average of 87% and 6% of their time within enclosed rooms and vehicles, respectively. Under these circumstances, wind driven rotating ventilators, which use natural energy and are cheap to manufacture, install and maintain, can become very effective non-polluting means of alleviating the problems within enclosed spaces. The author has been pioneering design and performance studies of environment friendly products such as the rooftop ventilator for over a decade at the University of New South Wales in Australia. The purpose of this paper is to detail the basic working principles of this ventilator and the series of detailed experimental and numerical investigations that has been performed in the optimization of the rooftop ventilator in terms of performance with higher air mass extraction rate and improved safety in operation has been achieved. Findings from these studies have been incorporated in the design of ventilators that are now commercially produced and marketed throughout the world by CSR Edmonds Pry Ltd of Australia. The conduct and outcomes of these works form the basis of this keynote paper.

Virtual design and analysis with multi-dimension coupling for engineering machinery cooling system

A good cooling circle should ensure that the system can work at an appropriate temperature in the requirements of power increase,engine compartment constraint and working demands for modern engineering machinery,which asks for a thorough understanding of system thermal loads before practical production.However,traditional experiment method spends a long time,costs a huge resource but lacks efficiency,whereas virtual design can avoid the shortcomings of traditional method and can analyze operating states adequately with variable loads on engine,generator,drives,battery pack and HVAC systems.Therefore,this paper focuses on a new virtual design method based on multi-dimension coupled simulation adopting Flowmaster software for initial prediction and CFX tool for further optimization.The simulation results in different operating conditions are compared and validated with experiments.Orthogonal experiment and range analysis are used to explore key parameters of cooling system.The research will be helpful in guiding future design and optimization of engineering machinery.