Search results

The combination with an engine combustion chamber of annual form having inner and outer peripheral walls, and an entrance at one end, of an annular arrangement of equispaced fuel nozzles in said entrance, air inlets corresponding in number to and respectively surrounding said fuel nozzles, air‐swirling means in said air inlets, means supporting said air inlets and fuel nozzles and shaped to provide a recess around each of said air inlets, additional air inlets at circumferentially spaced positions in said inner and outer peripheral walls adjacent to said entrance, and air nozzles leading from said additional air inlets and situated in pairs within said chamber with the nozzles of each pair inclined away from each other, the number of pairs of air nozzles leading from the inlets in the inner peripheral wall of said chamber being equal to the number of pairs of air nozzles leading from the inlets in the outer peripheral wall of said chamber, and also equal to the number of said fuel nozzles, and the inner ends of said air nozzles being arranged to direct jets of air towards the nearest fuel nozzles so that each individual fuel nozzle has directed towards it the air jets from one nozzle of each of four adjacent pairs, whereby the air jets serve in conjunction with the swirling air entering said chamber through the first mentioned air inlets to form swirling rings of air around the individual fuel jets emerging from said fuel nozzles.

The purpose of air-intake duct used in combat aircrafts is to decelerate the inlet flow and concurrently raise the static pressure recovery at the compressor inlet. Because of side-slip movement during sharp maneuvers of the aircrafts, the airflows ingested into twin air-intake ducts are not same and symmetric at its two inlets but are asymmetric in nature. The asymmetric inlet flow conditions at the twin air-intakes thus caused instabilities and deteriorated aerodynamic performance of aircraft components such as compressors and other downstream components. This study aims to investigate the flow control in a twin air-intake with asymmetric inflows.

The continuity and momentum equations are solved with second-order upwind scheme for computing finite-volume method-based unsteady computational fluid dynamics simulation.

Performance parameters are deteriorated with the increase of inflow asymmetry in the twin air-intake duct. Slotted synthetic jets are used to manage flow separation, thereby increasing aerodynamic performance of the air-intake. A variety of vortical structures are generated from the rectangular slots, convected downstream of the twin air-intake. The use of slotted synthetic jets increases static pressure recovery by 64 per cent whereas reducing total pressure loss coefficient by 63 per cent, distortion coefficient by 58 per cent and swirl coefficient by 55 per cent which is an indicative of better aerodynamic performance of twin air-intake.

The study stresses the need of robust flow control technique to improve the performance of combat air-intake system under extreme maneuvering conditions. The results can be useful in designing air-intake satisfying the stealth features for modern combat aircrafts.

The purpose of this paper is to analyze the phenomenon of makeup effect using numerical simulation and model experiments on seven different natural smoke extraction patterns of tall space. Airflow distribution and heat accumulation phenomenon in different cases are compared. The natural smoke exhaust system for tall spaces has many advantages, including low cost, no power and low maintenance cost. It is more advantageous than the mechanical type of exhaust. However, the internal air distribution is complicated since the large span spatial character. Effective and correct verification method is very important for the analysis of flow fields in tall spaces.

This study used fire dynamics simulator (FDS) software to simulate the fire scene. The model experiments are conducted to determine if the numerical simulation results are reasonable. A single-mirror Schlieren system, including an 838 (H) × 736 mm (W) square concave mirror, as well as the focal length of 3,100 mm was adopted to record the dynamic flow of hot gas. Six smokeless candles were burned in a 1/12.5 model in experiments to record the distribution of inflow, accumulation and outflow of airflow in the space. In addition, the thermocouple lines were mounted in the model for temperature measurement.

The results of numerical simulation and model experiments have proved that makeup air has a significant effect on the effectiveness of a natural smoke vent system. Larger areas of smoke vents will produce more heat accumulation phenomenon. In this study, the air inlet and vent installed on the same side have a better heat removal effect. Moreover, Schlieren photography technique is proved to be an accurate measurement method to record the dynamic flow of hot air immediately, directly and accurately. The dynamic flow behavior of hot gas in the model has been visualized in this paper.

At present, there is no examination method other than checking the smoke vent area to validate the effectiveness of a natural smoke vent system in Taiwan, as well as no requirements regarding the makeup inlet. The effect of makeup air in generating the effective push-pull phenomenon of airflow has been analyzed. In addition, the post-combustion hot gas distributions were visualized by using Schlieren photography technology in the model space, compared with the FDS simulation result and thermocouple recorded temperature. A verification method in the model experiments is established to determine if the numerical simulation results are reasonable.

This paper aims to predict the effect of combustor inlet area ratio (CIAR) on the lean blowout limit (LBO) of a swirl stabilized can-type micro gas turbine combustor having a thermal capacity of 3 kW.

The blowout limits of the combustor were predicted predominantly from numerical simulations by using the average exit gas temperature (AEGT) method. In this method, the blowout limit is determined from characteristics of the average exit gas temperature of the combustion products for varying equivalence. The CIAR value considered in this study ranges from 0.2 to 0.4 and combustor inlet velocities range from 1.70 to 6.80 m/s.

The LBO equivalence ratio decreases gradually with an increase in inlet velocity. On the other hand, the LBO equivalence ratio decreases significantly especially at low inlet velocities with a decrease in CIAR. These results were backed by experimental results for a case of CIAR equal to 0.2.

Gas turbine combustors are vulnerable to operate on lean equivalence ratios at cruise flight to avoid high thermal stresses. A flame blowout is the main issue faced in lean operations. Based on literature and studies, the combustor lean blowout performance significantly depends on the primary zone mass flow rate. By incorporating variable area snout in the combustor will alter the primary zone mass flow rates by which the combustor will experience extended lean blowout limit characteristics.

This is a first effort to predict the lean blowout performance on the variation of combustor inlet area ratio on gas turbine combustor. This would help to extend the flame stability region for the gas turbine combustor.

Vertical gardens offer multiple benefits in urban environments, including passive cooling services. Previous research explored the use of “active vertical gardens” as potential evaporative air-cooling units by developing a mathematical model based on the FAO-56 Penman Monteith equation. Further research showed that active vertical gardens function best by creating an airflow in the cavity behind the garden such that air is cooled by flowing over the water-saturated garden substrate. The purpose of this paper is to improve the quantification of active vertical garden performance.

A building-incorporated vertical garden was built in Quito, Ecuador, with an air inlet at the top of the garden, an air cavity behind the garden and where air was expelled from the base. Measurements were made of air temperature, humidity and velocity at the air inlet and outlet.

The active vertical garden cooled the air by an average of 8.1 °C with an average cooling capacity of 682.8 W. Including the effects of pre-cooling at the garden inlet, the garden cooled the air by an average of 14.3 °C with an average cooling capacity of 1,203.2 W.

The results are promising and support the potential for active vertical gardens to be incorporated into building services and climate control.

A comprehensive investigation on the outlet air position effects on the thermal comfort and air quality has been achieved. In addition, airflow and temperature distributions in ventilated cavities filled with an air-CO₂ mixture with mixed convection are predicted. The airflow enters from the cavity through an opening in the lower side of the left vertical wall and exits through the opening in one wall of the cavity. This paper aims to investigate the outlet location effect, four different placement configurations of output ports are considered. Three of them are placed on the upper side and the fourth on top of the opposite side of the inlet opening. A uniform heat and CO₂ contaminant source are applied on the left vertical wall, while the remaining walls are impermeable and adiabatic to heat and solute. The cooling efficiency inside the enclosure and the average fluid temperature are computed for different Reynolds and Rayleigh numbers to find the most suitable fluid outlet position that ensures indoor comfortable conditions while effectively removing heat and the contaminant. This is demonstrated by three relevant indices, namely, the effectiveness for heat removal, the contaminant removal and the index of indoor air quality.

The simulations were performed via the finite-volume scSTREAM CFD solver V11. Three different values of CO₂ amount are considered, namely, 10³, 2 × 10³ and 3 × 10³ ppm, the Reynolds number being in the range 100 ≤ Re ≤ 800.

Based on the findings obtained, it is the configuration whose air outlet is placed near the heat source and the contaminant, which provides a better air distribution and a ventilation efficiency compared to the others ventilation strategies.

The studies on heat and mass transfers by natural and forced convection in ventilated cavities remain a fruitful research topic. Thereby, such a study deals with different ventilation strategies through cavities containing an air-CO₂ mixture subjected to a mixed regime. In particular, the air inlet velocity and contaminant sources’ effects on thermal comfort and air quality have been investigated.

The propulsion system integration of a turboprop aircraft, which has been developed for the basic trainer, was performed. The proper turboprop engine was selected among worldwide existing engines by the specific developed engine selection technique and trade‐off studies such as customer’s request for operational capability (ROC), propulsion system parameters, performance analysis with engine installed effects, future growth potential, integrated logistic support (ILS), maintainability, interfaces with the airframe, etc. The chin type air inlet with the plenum chamber was designed in consideration of the inclined configuration to minimize the propeller swirl effect, the inertial separation bypass device to reduce FOD, and the super‐ellipse and NACA‐1 profile lip to maximize the ram recovery. The air inlet was analyzed by a higher‐order source panel method considering propeller wake. The exhaust duct was designed through internal cross‐section area determination to maximize the cruising power as well as external configuration to maximize the effective power, to minimize the aerodynamic drag and to minimize the cockpit contamination by the exhaust gas. The proper oil cooler for the selected turboprop engine was determined with cooling requirements and the oil cooling inlet duct with NACA configuration was designed. The test of the propulsion system including the installation performance test with the effects of the air inlet, the exhaust duct, the propeller and the nose fuselage configuration was performed in the test cell.

The lean blowout (LBO) limit of the combustor is one of the important performance parameters for any gas turbine combustor design. This study aims to predict the LBO limits of an in-house designed swirl stabilized 3kW can-type micro gas turbine combustor.

The experimental prediction of LBO limits was performed on 3kW swirl stabilized combustor fueled with methane for the combustor inlet velocity ranging from 1.70 m/s to 6.80 m/s. The numerical prediction of LBO limits of combustor was performed on two-dimensional axisymmetric model. The blowout limits of combustor were predicted through calculated average exit gas temperature (AEGT) method and compared with experimental predictions.

The results show that the predicted LBO equivalence ratio decreases gradually with an increase in combustor inlet velocity.

This LBO limits predictions will use to fix the operating boundary conditions of 3kW can-type micro gas turbine combustor. This methodology will be used in design stage as well as in the testing stage of the combustor.

This is a first effort to predict the LBO limits on micro gas turbine combustor through AEGT method. The maximum uncertainty in LBO limit prediction with AEGT is 6 % in comparison with experimental results.

A comprehensive series of tests have been made on an experimental single‐stage turbine to determine the cooling characteristics and the overall stage performance of a set of air‐cooled turbine blades. These blades, which arc described fully in Part I of this paper had, internally, a multiplicity of passages of small diameter along which cool air was passed through the whole length of the blade. Analysis of the test data indicated that, when a quantity of cooling air amounting to 2 per cent, by weight, of the total gas‐flow through the turbine is fed to the row of rotor blades, an increase in gas temperature of about 270 dcg. C. (518 deg. F.) should be permissible above the maximum allowable value for a row of uncoolcd blades made from the same material. The degree of cooling achieved throughout each blade was far from uniform and large thermal stresses must result. It appears, however, that the consequences of this are not highly detrimental to the performance of the present type of blading, it being demonstrated that the main effect of the induced thermal stress isapparently to transfer the major tensile stresses to the cooler (and hence stronger) regions of the blade. The results obtained from the present investigations do not represent a limit to the potentialities of internal air‐cooling, but form merely a first exploratory step. At the same time the practical feasibility of air cooling is made apparent, and advances up to the present arc undoubtedly encouraging.

Apricots are not only nutritionally-rich but also possess pharmacological significance owing to their high antioxidant activity, and they are rich in vitamins, fibers, bioactive phytochemicals and minerals. Because of its immense organoleptic characteristics, apricot juice (AJ) is well accepted; however, it has a limited shelf-life, thereby demanding it to be converted into other shelf-stable form. One of the approaches is converting this juice into dehydrated powder. Amongst the various dehydration techniques available, spray drying is usually preferred; however, it involves the use of several independent variables, which need to be optimized, thus prompting to optimize the process to obtain spray dried apricot powder (SDAP) with improved quality.

The spray-drying process of apricot juice was done using the response surface approach. The process variables included the inlet air temperature of 135–220°C, gum arabic concentration of 4–25%, feed flow rate of 124–730 mL/h, feed total soluble solids (TSS) of 10-30°Brix and atomization speed of 11,400–28,000 rpm. The dependent responses were powder yield, hygroscopicity, solubility, moisture content, carotenoids (CT), ascorbic acid (AA), radical scavenging activity (RSA), lightness, wettability, bulk density, particle density and porosity.

Amongst all independent variables, inlet air temperature had most predominant impact on all the investigated responses. The optimum processing conditions for development of apricot powder with optimum quality were 190°C inlet air temperature, 18.99% gum arabic, 300.05 mL/h feed flow rate, 24°Brix feed TSS and 17433.41 rpm atomization speed. The experimental values were found to be in agreement with the predicted values, indicating the suitability of models in predicting optimizing responses of apricot powder. Flowability as Carr's index (CI) (22.36 ± 1.01%) suggests fair flow of powder. Glass transition temperature of powder was 57.85 ± 2.03°C, which is much higher than that of ambient, suggesting its better shelf stability.

To the best of author's knowledge, very limited or very few studies have been carried out on the spray-drying process for the manufacture of SDAP. The results of this investigation will open up new horizons in the field of food industry in the Union Territory of Jammu and Kashmir, India or elsewhere in the apricot-growing areas of India.