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Herein, a non-boiling two-phase flow containing air and water through a downward flow in a vertical tube with helical corrugations has been investigated. In this simulation, various flow rates for air and water are considered, and three corrugation pitches 1, 1.5, and 2 cm are included. It can be seen in the results that the pressure drop values decrease with an increase in volume fraction. It should be noted that the reduction of pressure drop values with the reduction of volume fraction (VF) is based on the reduction of the water flow rate, which is visible. By comparing the pressure drop values for each corrugation pitch, it can be seen that as the pitch decreases, the pressure drop values increase significantly. The results for Nusselt number show that Nusselt number decreased with an increase in the volume fraction. By reducing the water flow rate, the intensity of the main flow is reduced the intensity of turbulence is also reduced and the heat transfer coefficient is reduced. Ultimately, the cost-benefit ratio has been utilized to show real results for each studied case.

This paper presents a numerical method to evaluate the system conditions in transient mode for a standing wave thermo-acoustic engine (STAE). This method focuses on increasing the accuracy of predictions and creating a better eyesight of the operating conditions of these devices. Combining the numerical solution of transient mode with the electrical circuit analogy of standing wave TAE, is the main idea of this work. Electrical circuit analogy of STAE is done by assuming each component of a STAE as a lumped element. The result of Combining the time-dependent numerical solution and the electrical circuit analogy is a code, which determines the condition of startup, steady periodic, and damping regime of the spontaneous oscillations in the STAE. Accordingly, a nonlinear temperature distribution is obtained along the hot core. The developed numerical approach is in line with the experimental results of a STAE. Based on this method, the temperature variations along the stack and the impact of stack material on startup time and onset temperature are numerically investigated. Additionally, the onset temperature profiles are calculated and presented comparatively for the numerical and experimental results. The startup time of spontaneous oscillations is calculated for the standing wave system. Consequently, the best geometry that quickly reaches the sustained oscillations can be selected using this model. Examining the temperature profile during the startup and damping process highlights a temperature difference between these two processes. Observations show that using a material with lower thermal conductivity in the stack section can reduce the onset-damping temperature difference. Also, with the help of this method the startup moment of spontaneous oscillations was calculated as second in the system. The data obtained from the experimental tests and the temperature profiles resulting from the numerical solution method, showed a good agreement with each other for the onset and damping process in the system. The novel approach described here shows potential in capturing the onset-damping behavior of thermoacoustic systems efficiently.

In this study, the effects of adding methylated homopolymer to gasoline on the performance of an internal combustion engine have been investigated. This additive increases the number of octane gasoline. In this research, these fuels which include ordinary gasoline and the other gasoline with the methylated homopolymer, were subjected to performance tests on the internal combustion engine. Also, the amount of exhaust emissions of the engine was measured. The results of experimental tests show that with the addition of additive to gasoline, the brake torque and braking power were increased by 4.28 % and 2.31 %, respectively, in the mean of average values (different engine operating speed). By combining gasoline and additive, carbon dioxide and nitrogen oxide contaminants increase by 7.41 % and 6.21 %, respectively. Also, contaminants of uncured hydrocarbons and carbon monoxide emissions from the engine are reduced by 18.17 % and 9.05 %, respectively, in the mean of average values.

The purpose of this study is to provide an efficient Multi-Objective Multidisciplinary Robust Design Optimization (MOMRDO) framework. To this end, Bi-Level Integrated System Synthesis (BLISS) framework is implemented as a fast Multi-disciplinary Design Optimization (MDO) framework. Progressive Latin Hypercube Sampling (PLHS) is developed as a Design of Experiment (DOE) of the Uncertainty Analysis (UA). This systematic approach leads to a fast, adaptive and efficient framework for Robust Design Optimization (RDO) of complex systems. The accuracy and performance of the proposed algorithm have been evaluated with various tests. Finally, the RDO of a hydrazine monopropellant thruster is defined as a case study. The results show that the proposed method is a fast and efficient method for the multi-objective optimization design of complex systems, and this approach can be used for other engineering applications as well.

Today's Human Life is Undeniably Dependent on Satellites that have being sent to Earth's Orbit by Launch vehicles. Delivery of any Kind of Cargo to Space must be carried out by Launchers, which are Designed and Optimized for the Best Energy Consumption Mood. Use of Porous Materials in the Engine Injector Plate culd be One of the Optimization Steps in this vehicles Engine. In this Paper, Applications that Utilize Porous Materials to Improve Combustion Efficiency have been Reviewed. In this Regard, the Results of Experiments Performed by Four Different Porous Injector Designs, were Studied. The First Design was a Porous Injector with Five Liquid Oxygen Injection Posts, which has been Undergone Cold and Hot Tests for Optical Researches.The Test Results of the Porous Injectors API68, API80-168 and the Improved API68 Injector, Using Two Subscale Combustion Chambers Designed and Built at the German Space Research Center, were Reviewed. Combustion Chamber Used for the Optical Tests, was Cooled by Water and Made Possibility of Taking Picture From Combustion Process. One of the Important Points, was the Reduction in Combustion Efficiency of the API80-168 Injector Head, due to Injector Head Correction, to Prevent Excess Oxygen Accumulation near the Combustion Chamber Wall. Another Important Point, was the Acoustic Damping Characteristic of the Porous Injector Plate, which Results in More Combustion Stability, Compared to the Coaxial Injector Head. However, During Some Reviewed Test Runs of API80- 168 Injector Head, Strong Oscillatory Instabilities were Observed which caused the Engine to Automatically Shut Down. Finally the Experimental Results of Four Different Porous Injector Heads with Oxidizer Transfer Tubes, Under Different Fluid Flow Regimes and Deep Throttling was Analyzed

In this study, effects of adding butene, homopolymer to gasoline on the performance of a four-stroke spark ignition (SI) engine and pollutant emissions have been investigated. This additive increases the octane number of gasoline. In this research, the additive was combined with a non-leaded gasoline. Also, in addition to fuel changes and the use of additives, engine spark plugs were replaced and three types of spark plugs were used for this study. These include single electrode spark plug, dual electrode spark plug and Platinum+4 spark plug. The results of experimental tests showed that with the addition of additive to gasoline, the brake torque and braking power were increased with the use of each of the three spark plug type. The results revealed that by combining gasoline and additive, carbon dioxide and nitrogen oxides emissions were increased. On the other hand, unburned hydrocarbons and carbon monoxide emissions from the engine were reduced. In addition, it was concluded that changing the spark plugs had slight effect on engine performance and pollutant emissions, and that the results of experimental tests using all three types of spark plugs were almost identical.

A two-dimensional numerical simulation of the spray flame has been carried out in a smooth counterflow configuration, and the region of formation of droplets group combustion by the flame index parameter for strain rate, equivalence ratio and the diameter of different droplets. n-decane (C10H22) is used as a liquid spray fuel, and a one-step global reaction is employed for the combustion reaction model. Fuel droplets are randomly injected using an UDF code in the air inlet and the droplet motion is calculated by Lagrange method. According to the results, in the ratio of high ratios, high strain rates and large droplet diameters, The temperature of the flame center decreases due to the suppression of the chemical reactions resulting from the reduction of oxidizing fractionation, and the dominant flame regime in these states is diffusion. The external group combustion of droplets occurs in the upper and lower layers of flame, and combustion of the internal group occurs at the center of the flame.

Studying the combustor flow field helps identify effective fuel and air mixing areas. The purpose of this paper is to investigate the structure of cold flow in a single-element Lean Direct Injection combustor. In studying and modeling of a turbine engine combustor, it is important to identify the areas of swirling, reversal and symmetry of the flow inside the chamber due to its influence on the rate of fuel and air mixing and also to study the reaction flow accurately. In this paper, the effect of operating pressure on the turbulent flow is studied. Since computational fluid dynamics are very time-consuming to solve the reacting flow problems, it is necessary to select the appropriate turbulence model that saves time with good accuracy. Comparing the computational results of the k-ɛ Realizable and Reynolds stress turbulence models (RSTM) and computational errors analysis, the maximum error was obtained for the Reynolds stress model of 31% and for the k-ɛ Realizable model of 37% compared to the experimental data. The difference between numerical results of turbulence models showed that the low-cost k-ɛ Realizable model is acceptable for the studied studies and can be used to model the reacting flow of an LDI combustor with highly swirl flow.

Calibration of hot-wire and hot-film probes at low velocities is a difficult task because the dynamic pressure at these velocities is very low and may not be measured easily. To overcome this problem, substituent techniques have been presented in the literature that rely on other phenomena and utilize different hardware. This paper describes a simple and low-cost method which proposes to move the anemometer probe in quiescent air (here by means of a swinging arm) and track this motion with a camera. After processing of the images, velocity time history of the probe is found by numerical calculations. Calibration curve is then obtained without any predetermined relationship. Using a medium-speed video camera that is often found in laboratories would avoid the need to a position sensor and a complicated arm on which this sensor is mounted. This technique can be used not only for pendulums but also for other means of moving probes in quiescent medium.

One-dimensional modeling of aircraft piston engines is one of the methods for studying their behavior and performance in different environmental conditions. In this research, the Rotax 914, an aerial Spark Ignition (SI) turbocharged engine, was modeled one-dimensionally to predict its behavior at different altitudes. To address this issue, the one-dimensional model of all engine components including air filter, carburetor, air manifold, inlet and outlet valves, cylinder and piston along with crankshaft, exhaust manifold and turbocharger were created in GT-Power software.Then by validating the model with the data provided by the manufacturer and ensuring the accuracy, the significant performance parameters of engine and turbocharger performance curves were evaluated for different flight conditions up to 30,000 feet. According to the results, the turbocharger prevented a dramatic decline in engine performance parameters up to 18,000 feet. However above that altitude, due to the compressor reaching the choking region, it is not possible to charge the required air and avoid severe engine performance loss. It was also observed, by studying the effect of ambient temperature changes on engine performance, an increase of 40 °C in the ambient temperature caused a 10% reduction in the braking horse power, and consequently, performance loss during climb period. The effect of changes in ambient temperature and altitude on engine performance varies so that, until the engine reaches the compressor's choking region, the impact of the ambient temperature variations is more perceptible, after that, the height factor will have a greater influence on the engine performance.

The purpose of present paper is simulation a direct injection stratified charge natural gas engine. The KIVA-3V code was used for gaseous fuel injection simulation. Compression and expansion stroke of engine cycle is simulated using KIVA-3V code. In cylinder fuel equivalence ratio distribution criterion is used for studying mesh independency. The results show that 550000 cells number is sufficient. The amount of NO emission in the end of closed cycle simulation was found equal 674.875 ppm and In cylinder pressure versus engine crank angle degree was simulated that maximum value found in 366 oCA that equal to 27.3222 bar.

In this study, the effect of Methanol (M5, M7.5, M10, M12.5, M15) on the performance and combustion characteristics of a spark ignition engine (SI) were investigated. In the experiment, an engine with four-cylinder, four stroke, multipoint injection system (Ford, Zetec-E) was used. Performance tests were conducted for brake torque, brake power, brake thermal efficiency, volumetric efficiency, equivalence air-fuel ratio, and brake specific fuel consumption and exhaust emissions (CO, CO2, HC, NOx) were analyzed under wide open throttle operating conditions and variable engine speed ranging from 1500 to 5000 rpm. The experimental results showed that the performance of engine was improved with the use of methanol. It was also shown that CO and HC emissions were reduced with the increase of methanol content while CO2 and NOx were increased.