Quanhong Xu

Injection of Supercritical Aviation kerosene fuel into quiescent atmospheric environment

*† ‡ § ** The injection of RP-3 aviation kerosene at conditions near and above the critical point into a quiescent atmospheric environment is experimentally studied, with special emphasis on the effects of fuel injection temperature and pressure on jet characteristics, shock structures, and phase transition. Visualization of the near-field jets and characterization of the shock/jet structures are performed using schlieren imaging. Flow visualization shows fuel condensation phenomenon when supercritical kerosene is injected at reduced temperatures near unity. For the supercritical kerosene injection conditions investigated, ideal gas-like expansion and internal shock structures are observed. The jet expansion angle as well as the axial location and the size of the Mach disk are noted to increase as the injection pressure is increased. Furthermore, while the injection temperature has little effect on the jet structure, it affects the phase transition processes, as demonstrated in the thermodynamic phase diagram calculated using a three-species kerosene surrogate.

Evaluation of Combustion Performance of a Coal-Derived Synthetic Jet Fuel

For application to aircraft turbines, the present work experimentally examines the physical and combustion-related properties of an F-T synthetic jet fuel relative to the Chinese standard jet fuel, RP-3. This fuel, derived from coal feedstock, is characterized in terms of its physical properties such as density, flash point, freezing point, surface tension, viscosity, and heating value in accordance with Chinese National Standard Testing Methods. Subsequently, several important characteristics relevant to its use in aircraft turbine engines are investigated using a single cup model combustor rig, including atomization, ignition, blowout, and exhaust emissions experiments are carried out. Preliminary results suggest that the use of coal-derived synthetic jet fuel will not result in adverse effects on the performance of an aircraft turbine combustor relative to conventional aviation kerosene. These initial results support the conclusion that full-scale engine testing is warranted to further investigate the performance of F-T synthetic jet fuels in practical systems, and to determine its ability to act as a “drop-in” replacement for traditional aviation fuel.Copyright

Injection of Subcritical and Supercritical Aviation Kerosene Into a High-Temperature and High-Pressure Crossflow

In the present experimental study, injection of subcritical and supercritical kerosene into a high-temperature and high-pressure subsonic crossflow was investigated. Visualization and characterization of the jet structures were performed using schlieren imaging, from which the jet penetration trajectory was determined. For the conditions tested, a correlation of jet penetration trajectory was developed, with momentum ratio as the primary parameter. An analysis based on one-dimensional isentropic flow was also conducted to calculate the flow parameter variations in the nozzle and along the jet trajectory. Using a three-component kerosene surrogate, the phase transition processes for supercritical and subcritical kerosene jets were illustrated in the thermodynamic phase diagram. Experimental and analytical results demonstrated that the behavior and penetration of supercritical kerosene injection into high temperature and high pressure crossflow were closer to those of the case with gas jet injecting into a gas crossflow than the case with liquid kerosene injection.© 2011 ASME

Effect of Impingement/Effusion Hole-Area Ratio on Discharge Coefficients of Double Cooling Wall

This paper presents the experimental investigations on the discharge coefficients of impingement/effusion double flat wall with the impingement/effusion hole-area ratios of 1, 0.64 and 0.28. The impingement and effusion walls researched have equal numbers of holes per unit surface area in diamond arrays. The impingement holes are normal to the wall surface, the effusion holes are 30 degree to the wall surface in the sreamwise direction of the main flow, and both the impingement and effusion holes are arranged in the staggered mode. The CFD code was also applied to investigate the flow field within the impingement/effusion wall in detail. The experimental results indicated the relationship of the discharge coefficients of the single impingement wall, effusion wall and double wall with the overall pressure parameter of double wall in different impingement/effusion hole-area ratios, and were explained in the CFD results.Copyright

Effect of Primary Zone Operating Condition for Dilution Mixing Behavior in a Gas Turbine

The exit temperature distribution had a great effect on reliability and security in a gas turbine. In this paper, the exit temperature distribution of a small engine reverse-flow combustor with three injectors test module was experimentally obtained to qualitatively analyze the influence of the primary zone operating condition by changing the fuel air ratio at the ambient pressure and temperature condition. Under the nearly identical air condition, there was no obvious difference on the mixing performance with different fuel flow rate. The hot zones occurred at the same position of the combustor exit section, and the temperature declined in the radial direction from the center. It could be seen that the radial temperature profiles in FAR of 0.022–0.03 were almost same. Malvern experimental results showed that the air fuel ratio of swirler cup ranges from 5 to 40 and the droplet distribution index n could not be increased or decreased by the ratio at different air pressure drop. The air fuel ratio of combustor swirl cup had reached more than 5 which fuel particle had been nearly stable and not got some variation by changing the fuel mass rate. As a result, the increase of fuel air ratio had no impact on fuel atomization uniformity in combustor dome. The fuel had been completely atomized when the combustor fuel air ratio ranged from 0.022 to 0.03, and its impact on the droplet size and uniformity of fuel could be neglected. With the uniform fuel spray, a numerical study of the whole combustor had been made to analyze the strong relation between swirl flow and jets of primary holes and dilution holes. The dilution jets had a strong effect on quenching flame and temperature dilution. Along the combustor flow direction, the temperature difference became less and less obvious, the addition of fuel would enhance the combustion intensity mainly in combustion zone, but with an effect of dilution jet, the temperature distributions had little deviation when increasing the fuel air ratio. And it showed a same phenomenon that different fuel air ratio would make the same exit temperature distribution which was found to be in line with the experimental results. In a word, for the primary zone operating condition in the combustor, it almost had no effect on the temperature distribution at the exit of the combustor by changing the fuel air ratio from 0.022 to 0.030 in primary zone at normal pressure and temperature condition.Copyright

Cooling Effectiveness of Impingement/Effusion Cooling With and Without Turbulence Promoter Ribs

In order to solve the cooling problem of aeroengine, a variety of highly efficient cooling methods came into application, such as effusion wall, impingement/effusion wall, etc. The impingement/effusion cooling methods with and without turbulence promoter ribs are introduced here. In the impingement/promoter ribs/effusion walls, turbulence promoter ribs are on the coolant side of effusion wall so as to enhance the internal cooling.Numerical and experimental approaches were taken to study cooling effectiveness of impingement/effusion liners cooling with and without turbulence promoter ribs. Cooling effectiveness of the two types cooling configurations were investigated on the same hot and cold air condition of inlet. Infrared camera was used to measure the temperature of effusion cooled surfaces on the side of hot main stream. The results showed double wall cooling with turbulence promoter ribs achieves higher cooling effectiveness than impingement/effusion cooling configurations.In addition, the two test configurations were investigated numerically to get clearer characterization of flow field in the double walls cooling configurations. High velocity vectors were found in the flow field within the gap of the double walls. A heat transfer enhancement was resulted in complex flows and increased area caused by the inclined holes and turbulence promoter ribs.Copyright

Experimental Characterization of Fuel-Air Mixing in a Multi-Hole Tube

This paper reports our recent research work on the mixing of fuel and air in a multi-hole tube. The multi-hole tube is an important component used for Lean Premixed Prevaporized (LPP), low emission combustion in a micro gas turbine. A baseline configuration of the multi-hole tube is investigated herein. Mixing characterization experiments are conducted by mapping the distribution of fuel-air ratios at the tube exit with a gas analyzer. Experimental results indicate that the matching of fuel atomization and flow field is the primary factor affecting fuel-air mixture uniformity. Based on the experimental results of the baseline configuration, a systematic and parametric configuration optimization can be then attempted. Experimental results with a modified configuration demonstrate improved mixing uniformity at the tube exit as compared to the baseline configuration, thereby signifying the importance of developing multi-hole tube design rules.Copyright

Investigation of Tangential Trapped Vortex Combustor

An innovative concept of Tangential Trapped Vortex Combustor (TTVC) applying a swirling flow to eliminate the guide vanes of the compressor and turbine in the future gas turbine engines is presented via theoretical analysis and experimental investigation. In TTVC, the airflow is mostly whirlblast, and the processes of evaporation, mixing, and chemical reaction for the liquid spray combustion take place along the tangential direction. It is shown that the TTVC operation has the potential of improving combustion efficiency, widening combustion stability range, and reducing emissions, mainly due to the effects of trapped vortex, high centrifugal force, and periodical mixing. Experimental results of the ignition and LBO limits in a small 4-cup annular TTVC operating at atmospheric pressure demonstrated that this innovative combustion technology has a good LBO limit performance to meet the requirements of advanced gas turbine engines.Copyright

Flow Field and Heat Transfer Characteristics in an Impingement/Effusion Cooling System for Combustor Liner

The present study is conducted to investigate the characteristics of the flow field and heat transfer in an impingement/effusion cooling scheme for gas turbine combustor liner. It is designed to provide an insight, through the study of the flow field, into the physical mechanisms responsible for the enhanced impingement heat transfer near the effusion hole entrance. In this impingement/effusion cooling scheme, the angle between the impingement hole and effusion hole and the wall surface are 90 deg and 30 deg respectively. The square arrays of impingement/effusion holes are used with equal numbers of holes offset half a pitch relative to each plate so that an impingement jet is located on the center of each four effusion holes and vice versa. The flow field of the double skin wall space is described by the way of Particle Image Velocimetry (PIV). Two kinds of target plates, with and without effusion holes, are used in the impingement heat transfer study. Through changing the impingement Reynolds and the impingement gap, the change of the impingement heat transfer coefficient on the target plates is investigated. The impingement heat transfer test results show that the impingement heat transfer is enhanced near the entrance of the effusion holes, which could fully explain the feature of the impingement heat transfer coefficient on the target plate.Copyright

Investigation of Combustion Performance of a Hybrid Airblast Atomizer Under Simulated Low Power Conditions

An aero gas turbine combustor has to meet requirements for both high and low power condition operation. Within the requirements for low power conditions, lean-blow-out (LBO) and combustion efficiency are the basic ones. A pure prefilming air blast atomizer may have difficulty meeting combustion requirements under low power conditions, such as, idle LBO, idle combustion efficiency, etc. Use of a hybrid airblast atomizer may offer a solution for such problems. A hybrid airblast atomizer is a single fuel injection unit that has both pilot and main fuel circuits. A simplex nozzle is often used for pilot fuel circuit and an airblast atomizer of the swirl cup type may be used for the main fuel circuit. For the main fuel circuit, fuel is injected from a number of plain jet holes. The fuel jets are injected towards a venturi, with the help of swirling air from another air swirler, and the main fuel is airblasted and well mixed with both swirler airflows. For low power conditions, the pilot fuel nozzle (simplex nozzle) works alone. Not all of the swirler air will mix with pilot nozzle fuel spray. With appropriate pilot nozzle pressure drop and with some airblast function, the pilot fuel is well atomized and does not fully mix with the swirler air nor with primary hole air. Thus, the low power condition combustion efficiency is improved. The investigation reported in the present paper has concentrated on hybrid atomizer combustion performance under simulated low power conditions, when only the pilot nozzle is operating. The study consists of the following parts: • Pilot nozzle drop size measurement; • Numerical simulation of combustor flow field; • Atmospheric ignition test; • Simulated idle condition LBO test; • Low power condition combustion efficiency test. Results are reported, and future work is defined.Copyright