Hot Combustion Gases Research Articles

Proof-of-Concept of a Thermal Barrier Coated Titanium Cooling Layer for an Inside-Out Ceramic Turbine

Abstract Increasing turbine inlet temperature (TIT) of recuperated gas turbines would lead to simultaneously high efficiency and power density, making them prime candidates for low-emission aeronautics applications, such as hybrid-electric aircraft. The inside-out ceramic turbine (ICT) architecture achieves high TIT by using compression-loaded monolithic ceramics. To resist inertial forces due to blade tip speed exceeding 450 m/s, the shroud of the ICT is made of carbon-polymer composite, wound around a metallic cooling ring. This paper demonstrates that it is beneficial to use a titanium alloy cooling ring with a thermal barrier coating (TBC), rather than nickel superalloys, for the interstitial cooling ring protecting the carbon-polymer from the hot combustion gases. A numerical design of experiments (DOE) analysis shows the design tradeoffs between the minimum safety factor and the required cooling power for multiple geometries. An optimized high-pressure first turbine stage of a 500 kW microturbine concept using ceramic blades and a titanium cooling ring in an ICT configuration is presented. Its structural performance (minimum safety factor of 1.4), as well as its cooling losses, (2% of turbine stage power) are evaluated. Finally, a 20 kW-scale prototype is tested at 300 m/s and a TIT of 1375 K during 4 h to demonstrate the viability of the concept. Experiments show that the polymer composite was kept below its maximum safe operating temperature and components show no early signs of degradation.

Visualization of Coolant Liquid Film Dynamics in Hypergolic Bipropellant Thruster

We conduct a high-speed visualization of coolant liquid film dynamics inside a 10N-class bipropellant thruster using monomethylhydrazine and a mixture of nitrogen tetroxide with approximately 3% nitric oxide as propellants at equivalent conditions with the flight model. The direct visualization of the liquid film inside a quartz glass chamber demonstrates the transient dynamics of film flow from ignition to cutoff for the first time. The scenario for the life of the film flow is found as follows: the coolant fuel jet impinges on the chamber wall being the liquid film; the friction force from the chamber wall rapidly decelerates the film as one-tenth of the injection velocity; next, the film moves sheared by the fast combustion gas downstream; and eventually the film completely evaporates by heat transfer from the hot combustion gas. The liquid film presents the typical ripple wave structure, covered by the velocity and thermal boundary layers. The effect of the mixture ratio is significant as the film flow rate increases at a small mixture ratio, leading to the longer film length.

The improved evaporation efficiency of a hot-bubble pilot plant (HBPP) caused by combustion gas for water treatment

HBPP uses hot dense bubbles as heat and mass carriers to evaporate the solution with improved evaporation efficiency, compared with the traditional thermal method. To develop an energy efficient water treatment process, we applied combustion gas as inlet gas within HBPP, for the first time to evaporate synthetic seawater. The advantage of using combustion gas is that the hot waste combustion gas from factories can be used at almost no energy cost, thereby reducing energy consumption. In this paper, the evaporation efficiency was determined by measuring the weight loss of column solution of HBPP in a 60 min run. Firstly, the ability of the HBPP to treat different types of wastewater, including 0.5 m NaCl solution or synthetic sewage, was tested by pumping air at the temperature of 80, 120 and 160 °C, respectively. The observed amount of evaporated water vapour was higher for the 0.5 m NaCl solution than for the synthetic sewage at inlet air temperatures of 80 °C and 120 °C but the same at a temperature of 160 °C. The HBPP shows the potential for water treatment regardless of wastewater type. Then, the evaporation efficiency was calculated for both combustion gas and air, at the inlet temperature of 120 °C to evaporate 0.5 m NaCl solution. The result showed an increment of 37% of evaporation efficiency achieved by sparging combustion gas. That is because the contained water vapour has a high capacity for efficient heat transfer to evaporate the solution. As a result, applying combustion gas within HBPP can provide an energy conservative method with improved evaporation efficiency for water treatment.

Large eddy simulation of two-phase reacting turbulent flow in a pilot-scale pulverized coal combustion furnace with flamelet model

A three-dimensional numerical simulation was performed to investigate the physics and combustion characteristics of a two-phase reacting turbulent flow in a pilot-scale pulverized coal combustion furnace. This included an elementary reaction mechanism using an extended flamelet/progress variable (EFPV) method. The simulation was validated via comparison with an experiment in terms of the gaseous temperature and distribution of the gas mole fraction. The EFPV method predicted the flame structure and combustion characteristics of the pulverized coal. In the main reaction zone where the released gas combustion was dominant, two separate combustion regions were observed, and they were attributed to hydrocarbons and CO combustion. Gas flow characteristics such as mixing of low temperature gas and hot burnt gas were well described in the inner recirculation zone. The CO2 conversion reaction to CO occurred slowly and decreased the gaseous temperature beyond the main reaction zone in the low and zero oxygen environments. The simulation predicted the unburned CO combustion correctly beyond the flame when staged air was injected; however, the combustion rate was overestimated due to the fundamental assumption of the EFPV method, attributable to the limitations of the steady state flamelet approach.

TDLAS measurements of temperature and water vapor concentration in a flameless MILD combustor

We performed non-intrusive tunable diode laser absorption spectroscopy measurements of the temperature (T) and water vapor concentration (X H2O) on a moderate or intense low-oxygen dilution combustion chamber. The combustor was operating in flameless mode by axially injecting fuel and air at high speeds through separate nozzles, thereby creating a recirculating flow of combusted gas. A pair of water vapor absorption lines near 7185.6 and 7444.36 cm−1 was used to acquire axial absorbance profiles along the height of the combustor. The axial profiles of T and X H2O were first derived using two-line thermometry measurements. Then the T profiles were estimated from each of the single absorption line measurements by assuming spatial uniformity of X H2O. Compared to a thermocouple temperature measured at the combustor outlet, the temperatures given by the two-line thermometry were under-estimated whereas the thermocouple temperature was in between the T range given by the single-line thermometry. Importantly, the measurement successfully revealed that the axial profiles of T and X H2O were mostly flat certainly due to the strong recirculation of the hot combustion gas; however, the different temperature values at a given height implied the existence of a radial temperature gradient in the combustor.

Effects of seal installation in the mid-passage gap between turbine blade platforms on film cooling

Hot combustion gas in gas turbines can be ingested into the mid-passage gap between the blade platforms, resulting potentially a catastrophic damage. To prevent the ingress of hot gas, the blade platform underneath cavity is pressurized with purge air. Seals are typically installed in the mid-passage gap to minimize the purge air requirement. Under inadequate back flow margin, ingress of the main flow can occur especially at the upstream region of the mid-passage gap due to the pressure distribution characteristics on the platform. Excessive leakage flow can significantly reduce the turbine performance. This study investigated the effect of a seal installed in the mid-passage gap on film cooling effectiveness and heat transfer on the platform. Experiments were conducted by varying the ratio of the leakage flow to the main flow by 0.2%, 0.4%, and 0.6%, in which the mid-passage gap was unblocked (no seal; Opening 100% case) and partially blocked (seal; opening 50% case). The film cooling effectiveness of the platform was measured using the pressure sensitive paint method, and the heat/mass transfer coefficient of the platform was obtained using the naphthalene sublimation method. The seal in the mid-passage gap reduced or prevented completely the ingress of main flow under the given conditions. Under a high blowing ratio, the seal had little effect on the platform film cooling effectiveness. At the same mass flow rate of leakage flow, the heat transfer distributions were similar, regardless of whether a seal was installed. However, the platform with a partial seal in the opening 50% case showed a peak in the heat transfer closer to the gap than the platform without the seal, as the leakage flow reattached closer to the gap.

Film cooling characteristics on blade platform with a leakage flow through mid-passage gap

Each turbine rotor assembly is composed of several blades, and there is a mid-passage gap between blade platforms. Purge air is supplied through the mid-passage gap to prevent the ingress of hot combustion gas which could lead to thermal damage to the blade platforms. The leakage flow (coolant) egested through the mid-passage gap affects the heat transfer of the blade platform and provides a cooling to the platform. This study investigated the effects of leakage flow on film cooling effectiveness and heat transfer on the platform with a mid-passage gap. The effects of main flow ingestion through the gap on the film cooling effectiveness and heat transfer on the platform were measured for different mass flow ratios (MFRs) of the leakage flow. The film cooling effectiveness was measured using the pressure sensitive paint method, and the heat/mass transfer was measured using the naphthalene sublimation method. The measured mass flow ratios of the leakage flow to the main flow were 0.2%, 0.4%, and 0.6%. At low mass flow ratios (MFR = 0.2%, 0.4%), the main flow ingested under the upstream region of the mid-passage gap and the leakage flow egested through the downstream region of the gap. The egested leakage flow provided a high film cooling effectiveness on the suction side downstream region. However, the leakage flow was egested from the gap with an injection angle of 90° and reattached to the surface, resulting in a high heat transfer in the suction side region near the gap. At a high mass flow ratio (MFR = 0.6%), the leakage flow egested through the entire mid-passage gap, but the leakage flow penetrated into the main flow resulted in a low film cooling effectiveness. As the leakage flow interacted with the main flow and formed a vortex, this resulted a region with film cooling effectiveness decrease and heat transfer increase.

Enhance the energy and exergy performance of hydrogen combustion by improving the micro-combustor outlet in thermofluidic systems

The main reason for the heat loss of micro-combustors is the hot exhaust gases. In this study, the exit part of the conventional micro-combustor has been improved to increase the heat transfer between the hot combustion gases and the walls of the micro-combustor. For this purpose, several approaches have been applied, including porous media, perforated fins, and 24 and 8 tube outlets for outlet replacement. In these improved micro-combustors, the thermal performances of the combustion of the hydrogen-air are numerically have been investigated. The results reveal that new micro-combustors by enhancing the velocity of the exhaust gases or increasing the surface area of heat transfer or transferring the hot gases to the walls, has led to a decrease in the temperature of the exhaust gases. However, the wall temperature and its uniformity have increased in the improved micro-combustors. Raising the wall temperature and reducing heat loss have increased radiation efficiency, and reducing entropy generation and energy loss in presented geometries diminish the exergy loss and enhance the exergy efficiency. Also, results showed that micro combustor with porous media has the best energy and exergy performance. Finally, the electrical power generation of micro-combustors has been investigated by photovoltaic cells.

Experimental investigation of a Jet-A1 fuelled peripheral vortex reverse flow combustor

Combustion characteristics of a novel peripheral vortex reverse flow (PVRF) combustor are investigated using Jet-A1 fuel. Previously, we have demonstrated the operation of PVRF combustor using LPG and ethanol fuels, and here we demonstrate and investigate the operation of PVRF combustor using Jet-A1 fuel. The combustor was operated at atmospheric pressure with preheated inlet air (300 °C) and high thermal intensity (25 MW/m3-atm at ø = 0.8) relevant to gas turbine combustors. Conventional swirler was not employed and the reactants were injected as jets. Combustion was primarily stabilized due to a dominant peripheral vortex of hot burned gases inside the combustor. In the non-premixed mode, the liquid fuel was injected coaxially w.r.t. the incoming air-jet and it was atomized due to strong shearing from the annular air jet. Shadowgraphy was used to investigate the atomization characteristics of the fuel. Electrochemical gas analyser was used to measure exhaust emissions (NOx, CO). The combustor demonstrated low emissions and stable operation over a wide range of equivalence ratios. CH* chemiluminescence was used to study the location and the dynamic behaviour of the reaction zone. The reaction zone was positioned further downstream in the non-premixed mode as compared to the prevaporized-premixed mode suggesting that atomization, evaporation and mixing of fuel in the non-premixed mode is causing a delay for the onset of the reactions. From shadowgraphy images, it was observed that retraction of the fuel jet considerably improved the fuel atomization.

Direct numerical simulations and models for hot burnt gases jet ignition

This work uses multiple three-dimensional Direct Numerical Simulations (DNSs) to i) investigate the ignition process of a cold lean premixed mixture at atmospheric conditions by a jet of hot burnt gases that may be cooled before injection ii) evaluate models able to predict the outcome of such a scenario in terms of ignition. Understanding and being able to model ignition of cold premixed mixtures by hot burnt gases is essential to design systems like engines (to ensure ignition) and flameproof enclosures (to prevent ignition). Limited work has focused on the combined effects of the jet injection speed and temperature on ignition. This is difficult to do by using experiments only and DNS is a natural approach to gain knowledge on that point. By varying the hot jet injection speed and temperature, the three-dimensional, kinetically detailed, DNSs allow a parametric study of the impact of these parameters on the ignition process and provide data to build and test models. Simulations prove that jet injection speed and temperature (usually less than the adiabatic flame temperature because of cooling effects through the injection hole) directly govern ignition. Chemical Explosive Mode Analysis (CEMA) is used to characterize the reacting flow structure which is strongly impacted by the jet injection speed. Based on the DNSs conclusions, a zero-dimensional Lagrangian model where a small element of the jet burnt gases mixes at a certain rate with the fresh gases while it potentially ignites is found to be a good candidate to predict the outcome of an ignition sequence (success or failure).

Energy and Exergy Assessment of S-CO2 Brayton Cycle Coupled with a Solar Tower System

In this research, we performed energy and exergy assessments of a solar driven power plant. Supercritical carbon dioxide (S-CO2) Brayton cycle is used for the conversion of heat to work. The plant runs on solar energy from 8 a.m. to 4 p.m. and to account for the fluctuations in the solar energy, the plant is equipped with an auxiliary heater operating on hot combustion gases from the combustion chamber. The capital city of Saudi Arabia (Riyadh) is chosen in this study and the solar insolation levels for this location are calculated using the ASHRAE clear-sky model. The solar collector (central receiver) receives solar energy reflected by the heliostats; therefore, a radially staggered heliostat field is generated for this purpose. A suite of code is developed to calculate various parameters of the heliostat field, such as optical efficiencies, intercept factors, attenuation factors and heliostat characteristic angles. S-CO2 Brayton cycle is simulated in commercial software, Aspen HYSYS V9 (Aspen Technology, Inc., Bedford, MA, USA). The cycle is mainly powered by solar energy but assisted by an auxiliary heater to maintain a constant net power input of 80 MW to the cycle. The heliostat field generated, composed of 1207 rows, provides 475 watts per unit heliostat’s area to the central receiver. Heat losses from the central receiver due to natural convection and radiation are significant, with an average annual loss of 10 percent in the heat absorbed by the receiver. Heat collection rate at the central receiver reveals that the maximum support of auxiliary heat is needed in December, at nearly 13% of the net input energy. Exergy analysis shows that the highest exergy loss takes place in the heliostat field that is nearly 42.5% of incident solar exergy.

Evaluation of the new energy-efficient hot bubble pilot plant (HBPP) for water sterilization from the livestock farming industry

Effluent and water management, in particular inactivating pathogens, have become more critical for the livestock farming industry, from both public health and business efficiency perspectives. The new hot bubble pilot plant (HBPP) uses hot air and hot combustion gases to produce hot bubbles that successfully inactivated Escherichia coli C-3000 (ATCC15597) in the lab, in different synthetic effluents and later at the farm using naturally occurring bacteria such as Salmonella, E.coli, Thermotolerant coliforms, and Cyanophyta and protozoa spores (oocysts and cysts) from Giardia and Cryptosporidium from piggery effluent.Many industries, such as pig farms, landfills, biogas power plants, and coal power plants, emit large amounts of hot combustion gases. The potential use of these hot combustion gases (waste) to produce hot bubbles in a bubble column reactor offers a new energy-efficient water sterilization process that fits within the circular economy principals by using waste gases as an input for the system. This new technology would then be able to compete with other water-disinfection technologies, such as UV irradiation, ozonation, and even chlorination, due to its low operating costs and high energy efficiency.

Suitability of Non-Reactive Flow Simulations in the Investigation of Mixing and Flameholding Capability of Supersonic Combustor Flameholder

ABSTRACT A comparative study is performed to investigate the effectiveness of non-reactive supersonic flow simulations in qualitatively predicting the mixing performance and flameholding capability of a pylon-cavity aided, sonic fuel injection flameholder under, reactive flow conditions. The performance parameters such as mixing and combustion efficiencies, and flammable plume area are taken into account for the study. A non-reactive, steady-state RANS simulation is solved using coupled, implicit, second-order upwind solver with a two-equation SST κ-ω turbulence model. The numerical scheme is validated experimentally using steady wall pressure data and 2-D velocity vector field. Similar steady-state modeling has been performed for a reactive flow simulation with an 18 step Jachimowski reaction scheme for -air reactants. The study consists of two distinct injection locations on the cavity floor. Inlet Mach number of 2.2 is maintained for all the cases. The study shows that the cavity vortex pair with recirculating hot burned gases plays a decisive role in accurately predicting the flame location within the configuration. Though the non-reactive flow simulations are helpful in understanding the fundamental mechanisms also relevant under reactive flow conditions, like fuel-air mixing for example, it fails in the accurate prediction of the ignition location and flame stabilization.

High-Momentum Jet Flames at Elevated Pressure, C: Statistical Distribution of Thermochemical States Obtained From Laser-Raman Measurements

Abstract A detailed investigation on flame structures and stabilization mechanisms of confined high momentum jet flames by one-dimensional (1D)-laser Raman measurements is presented. The flames were operated with natural gas (NG) at gas turbine relevant conditions in an optically accessible high-pressure test rig. The generic burner represents a full scale single nozzle of a high temperature FLOX® gas turbine combustor including a pilot stage. 1D-laser Raman measurements were performed on both an unpiloted and a piloted flame and evaluated on a single shot basis revealing the thermochemical states from unburned inflow conditions to burned hot gas in terms of average and statistical values of the major species concentrations, the mixture fraction and the temperature. The results show a distinct difference in the flame stabilization mechanism between the unpiloted and the piloted case. The former is apparently driven by strong mixing of fresh unburned gas and recirculated hot burned gas that eventually causes autoignition. The piloted flame is stabilized by the pilot stage followed by turbulent flame propagation. The findings help to understand the underlying combustion mechanisms and to further develop gas turbine burners following the FLOX concept.

Partially Premixed Flame Stabilization in the Presence of a Combined Swirl and Bluff Body Influenced Flowfield: An Experimental Investigation

Abstract Optical and laser diagnostic measurements in a nonpremixed model gas turbine (GT) burner have been performed to investigate the effect of an increase in thermal power on the flame stabilization. The model GT burner has a large bluff body base with an annular swirl region, leading to a convergent-divergent flow field at the burner exit. Under the investigated conditions, the flame stabilizes predominantly in the diverging section characterized by the swirl flow with a central recirculation zone. With increasing thermal power, the reverse flow of hot burned gases is strengthened, with the hydroxyl radical (OH) planar laser induced fluorescence (PLIF) images indicating an increase in the temperature of the burned gases. The preferred flame stabilization location coincides with the inner shear layer between the reactant inflow and the reverse flow of hot burned gases. At high thermal power, the flame seems to stabilize in regions of high fluid dynamic strain rate, highlighting the influence of the reverse flowing burned gases in the evolution of the flammable mixture upstream. However, simultaneous and time-resolved measurements of the flow-field and scalar field are needed for direct quantification of this. The results are in agreement with the flame stabilization theories based on partial fuel-air mixing and streamline divergence. The flow is seen to decelerate upstream of the flame front and the flame stabilizes in a region of low velocity, created as a result of heat release diverging the streamlines ahead of it.

Light Weight Aluminum Cartridge Case Design for IED’s Application - ANSYS

This paper describes the design analysis of the aluminum cartridge case, its testing, Analytical Simulation (ANSYS) and evaluation against Improvised Explosive Devices (IEDs) applications. Aluminum material is light in weight, non-corrosive and compatible with the propellant. Because of excellent properties, it is widely used in defence application sector. In the armament system, an effort is being made to reduce the cost, the weight of material from logistic point of view and its manufacturing process so as to meet the design requirements. Brass cartridge cases are being widely used in various types of ammunition for last 100 years e.g. armaments of small arm cartridges, artillery shell and power cartridges for fighter aircraft. Cartridges are made of either aluminum, steel or brass is filled with the propellants and pyrotechnic composition. With suitable means of ignition, the propellant generates the hot combustion gases at high pressure and temperature. These combustion gases are utilized to perform certain work on the system. The aluminum cartridge case for water disruptor applications plays a significant role in the destruction of the suspicious objects. This paper discusses the design aspects of the aluminum cartridge case for disruptor application of suspected IEDs. Performance evaluation parameters i.e. maximum pressure (Pmax) and time to reach maximum pressure (TPmax) of aluminum cartridge have been carried out in a Closed Vessel (CV) using a Data Acquisition System (DAS). The material properties of aluminum such as tensile strength, percentage elongation and yield strength are determined using a Universal Testing Machine (UTM). Using the data obtained by the above methods, an attempt has been made to determine stress, strain and deformation of the cartridge case theoretically and numerically using ANSYS software. The results obtained by both methods are compared. The results are in good agreement with each other. It is observed that the percentage error for von -Mises stresses is 10.2 % using numerical and theoretical approaches. The percentage error between numerical and theoretical values of the hoop and longitudinal stresses are 6.71 % and 6.78 %. The percentage error between numerical and theoretical values of the hoop and longitudinal strains are 1.36 % and 3.64 %. The errors between theoretical and numerical values for radial displacements are 2.83 %. The novelty in this research work is that the design analysis of aluminium cartridge case is carried out using ANSYS software simulating the real- world problem. The analytical results are compared with numerical results. The actual pressure experienced by the cartridge case generated by the propellant burning is taken into consideration. This pressure is measured by a pressure transducer fitted over a specially designed test rig using a DAS. The sample of aluminum case is tested for hardness and microstructure. The results show there is no significant difference before and after the hardness and microstructure of the material. The results of ANSYS for stress and strain are in good agreement with theoretically calculated results and numerical analysis as percentage error is less than 11. This draws the inference for validating numerical and theoretical results. It is seen that 57.352 % saving in weight using aluminum cartridge is achieved. Using ANSYS, hoop stress 382.7 MPa, Hoop strain 4.32x10-3, longitudinal strain 0.8602x10-3 and longitudinal stress 191.5 MPa are estimated. The main objective of this paper is to carry out design and analysis of aluminum cartridge case analytically as well as numerically.

An improved model to calculate radiative heat transfer in hot combustion gases

Radiative heat transfer plays an important role in the chemical reactions in the combustor. The widely used WSGG model proposed by Smith is established for normal pressure, which shows inevitable computational errors when dealing with radiative heat transfer problems at reduced or elevated pressures. In this paper, an improved global model is established to calculate the radiant energy exchanges between combustion gases and combustor chamber walls. Compared with the Smith model, the new model shows better performance in a wide range of pressure regions. The model accuracy is examined by computing the emissivity, radiative heat flux as well as the radiative source of H2O–CO2 gas mixtures at different pressure values. Finally, the radiative heat transfer inside a 3D TBCC(turbine-based combined cycle) engine exhaust system where strong gradients of pressure and temperature exist, is also addressed. The computational results show that the developed model provides approximate results at much less computational costs than the high-precision MSMGFSK-c8 model, which makes it competitive in complicated combustion systems.

IMAGING DIAGNOSTICS OF COMBUSTION INSTABILITY IN PREMIXED SWIRLING COMBUSTION

An experimental study on combustion instability is presented with focus on propane-air premixed swirling flames. Swirling flames under self-excited oscillation are studied by imaging of visible light and OH* chemiluminescence filter under several typical conditions. The dynamical characteristics of swirling flames were analysed by Dynamic Mode Decomposition (DMD) method. Three types of unstable modes in the combustor system were observed, which correspond to typical acoustic resonant modes (LF mode, C1/4 mode and P1/2 mode) of the combustor system. The combustion instability is in the longitudinal mode. Furthermore, the structure of downstream hot burnt gas under stable combustion and unstable combustion is studied by imaging of visible light and near-infrared light. Results show that there is a significant difference in the downstream flow under stable combustion and unstable combustion. The DMD spectrum of the flame and the downstream hot burnt gas obtained is the same, which is close to the characteristic frequency of acoustic pressure captured by the microphone signal. The visible light and near-infrared light imaging observation method adopted in this paper provides a new imaging method for the investigation of thermo-acoustic instability.

원형홀 내부 거칠기 분포가 막냉각 효율에 미치는 영향

Film cooling had been widely applied to hot parts in gas turbines or propulsion systems in order to protect the components from the hot combustion gas. Conventional film cooling hole has cylindrical shape and the surface roughness of the hole depends on the manufacturing process. In this study, the effect of roughness distribution inside a cylindrical film cooling hole on the film cooling performance was experimentally studied. The test plate with film cooling holes was made by the additive manufacturing process, and the film cooling effectiveness was measured using the pressure sensitive paint technique. The diameter of the hole was 5 mm, the hole length to diameter ratio(L/D) was 6, and injection angle was 30 degrees. The density ratio was 1.5 and the blowing ratio varied from 0.5 to 2.0. The mainstream velocity and turbulence intensity were 20 m/s and 11%, respectively. Results showed that the hole roughness had effect on the film cooling effectiveness near the hole exit, but the effect was diminished toward the downstream region. Also, the effect of hole roughness was not significant for lower blowing ratio cases.

Parameter optimization for MSMGWB model used to calculate infrared remote sensing signals emitted by hot combustion gases of hydrocarbon fuel

A new wavenumber subinterval grouping strategy was deduced to fit multi-scale multi-group wide-band k-distribution model (MSMGWB) used to calculate remote infrared signal of 3–5-micron wave band emitted by hot combustion gas of hydrocarbon fuel. Further, to deal with influence of initialization on the grouping result and calculation accuracies of the MSMGWB model, an optimization platform was established to find best combination of grouping results and model's Gauss quadrature schemes. The optimization objective function was established based on weighted calculation errors of MSMGWB model in 18 0D cases, using calculation results of line-by-line model (LBL) as benchmark. Optimization result was evaluated using other 0D cases with and without influences of various kinds of aerosol in atmosphere. Further, evaluations were presented on calculation of remote sensing thermal images for a supersonic aircraft exhaust system and its hot jet. Results indicated that the optimized MSMGWB model has higher calculation accuracies, better compatibilities and lower computational cost compared with the previous one. Finally, the influence factors of optimization result were discussed.