Canard-controlled missiles are popular due to their compact size and high maneuverability. However, it is well known that these missiles suffer from adverse roll properties caused by tail-fin-induced ...roll during canard deflection in roll maneuvers. While auxiliary systems like a free-spinning tail section can mitigate these issues, they have concerns regarding system complexity. This research focuses on optimizing the aerodynamic design of canard-controlled missiles to minimize the adverse roll without introducing additional systems. A multi-objective genetic algorithm (MOGA) is employed as the optimizer, striking a balance between minimizing undesired roll, maintaining static stability, and ensuring maneuverability. Computational fluid dynamics (CFD), employing the Reynolds averaged Navier–Stokes solver, provides an accurate calculation of the rolling moment coefficient related to adverse roll characteristics. To offset the high computational demands of CFD, a surrogate model is used within an optimization framework that incorporates the design of experiments and the Kriging model, coupled with the MOGA optimizer, for a more efficient optimization process. This proposed framework offers a range of optimal Pareto solutions with superior aerodynamic performance, subject to multi-objective functions and constraints. Following optimization, data mining techniques are used to elucidate why these Pareto solutions performed better, identifying key geometric features influencing missile performance and the correlation between objective functions and design variables. The findings highlight that the optimal missile designs should feature a reduced exposed semi-span, a key factor in adverse roll properties, to minimize induced roll while still accounting for stability and maneuverability.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The objective of this study is to investigate the performance characteristics of an injection CO2 (carbon dioxide) HPWH (heat pump water heater) at various operating conditions. In the standard and ...standby heat loss test conditions, the performance of a two-stage CO2 HPWH adopting a SCVI (sub-cooler vapor injection HPWH) cycle was measured and analyzed by varying the compressor frequency, the water flow rate, and the injection ratio at various outdoor temperatures. In the standard tests at the outdoor temperature of −15 °C, the COP (coefficient of performance) of the optimized SCVI HPWH was 7.6% higher than that of the non-injection HPWH. During the standby loss tests at the water flow rate of 200 kg h−1, the COP of the optimized SCVI HPWH was 7.1% higher than that of the non-injection HPWH.
•A CO2 heat pump water heater adopting a vapor injection cycle is considered.•The performance of the SCVI HPWH is analyzed in standard and standby loss tests.•The optimum water flow rate and injection ratio are determined.•The performance comparison between the SCVI HPWH and air heating HP is conducted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A large amount of heat flux from aerodynamic heating acts on reusable spacecraft; thus, an accurate heat flux prediction around spacecraft reentry is essential for developing a high-performance ...reusable spacecraft. Although the approximate convective-heating equations can calculate the heat flux with high efficiency and sufficient fidelity, the heat flux should be evaluated over a thousand times for the entire trajectory in multidisciplinary analyses. For these reasons, it is necessary to develop an efficient method for calculating the heat flux for multidisciplinary analysis. In this paper, an efficient method for heat flux calculation that is adoptable by multidisciplinary analyses for hypersonic vehicles, such as spacecraft, is developed. Approximate convective-heating equations were adopted to relieve the computational cost of estimating the heat flux, and an adaptive time step method for heat flux calculations was developed to reduce the number of heat flux calculations required across the entire flight trajectory. A dynamic factor was introduced that adjusts the time step between each instance of the heat flux calculation. Since the time step using this factor could increase under low heat flux conditions, the number of heat flux calculations decreases by approximately one-tenth with over 90% accuracy. Therefore, the efficiency was improved with high accuracy using the adaptively-determined time step according to this dynamic factor.
The objective of this study is to investigate the effects of vapor injection techniques on the heating performance of a CO2 heat pump. The performances of the flash tank vapor injection (FTVI), ...sub-cooler vapor injection (SCVI) and FTVI with a suction line heat exchanger (FTSX) cycles were measured and analyzed with variations of the outdoor temperature, compressor frequency, and injection mass flow rate. At the outdoor temperature of −15 °C and compressor frequency of 55 Hz, the heating capacity and COP of the optimized SCVI cycle were 12.1% and 12.7% higher than those of the optimized FTVI cycle, respectively, because the total mass flow rate in the SCVI cycle was higher than that in the FTVI cycle by the large temperature and pressure differences in the sub-cooler of the SCVI cycle. In addition, the optimum injection flow rate ratios in the vapor injection CO2 cycles yielding the maximum COP were determined at various compressor frequencies.
•The effects of vapor injection techniques of a CO2 heat pump are investigated.•The heating performance of the SCVI cycle is the highest and the most stable.•The optimum injection ratios are determined at various compressor frequencies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The injection mass flow rate in a vapor injection CO2 cycle is an important design factor to improve the heating performance of a heat pump at low ambient temperatures. The intermediate pressure in a ...twin rotary compressor strongly affects the injection mass flow rate, and can be adjusted by the cylinder volume ratio of the second-stage to the first-stage. In this study, the heating performances of the vapor injection CO2 cycles including the flash tank vapor injection (FTVI) and sub-cooler vapor injection (SCVI) cycles were measured by varying the cylinder volume ratio of the twin rotary compressor at the ambient temperature of −15 °C. From the results, the optimum injection ratio yielding the maximum COP was determined for each cylinder volume ratio. In addition, in the FTVI and SCVI cycles, the optimum cylinder volume ratio was determined as 0.7 in order to achieve the maximum COP with the designed heating capacity.
•A CO2 heat pump applying vapor injection techniques is considered.•The effects of cylinder volume ratio of a twin rotary compressor are investigated.•The optimum injection ratio is determined for each cylinder volume ratio.•The optimum cylinder volume ratio for the maximum COP is determined as 0.7.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The objective of this study is to investigate the control methods of the gas-cooler pressure in a CO2 heat pump. The cooling performance of the CO2 heat pump was measured by varying the refrigerant ...charge amount, EEV opening, compressor frequency, and outdoor fan speed at various outdoor temperatures. The effects of the EEV opening and the outdoor fan speed on the gas-cooler pressure and the COP were analyzed by using the experimental data. In the standard cooling condition at the compressor frequency of 45 Hz, the optimum gas-cooler pressure and the maximum COP were 9200 kPa and 3.04, respectively, at the optimum EEV opening of 41% and outdoor fan speed of 500 rpm. As the compressor frequency increased from 45 Hz to 55 Hz at the standard cooling condition, the optimum outdoor fan speed increased from 500 rpm to 700 rpm.
► Optimum control of the gas-cooler pressure of a CO2 heat pump is investigated. ► Optimum EEV opening exists for proper control of the gas-cooler pressure. ► Optimum outdoor fan speed increases with the increase in the compressor frequency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this study, the design optimization of a low Reynolds number airfoil is performed for a Mars exploration airplane. To achieve this goal, a multi-objective genetic algorithm (MOGA) using the ...Kriging model is used for optimization and a γ–Reθ model is adopted to predict the laminar-turbulent transition point on the airfoil. Both PARSEC and NURBS representations are used to define the geometry of the airfoil in order to investigate its effect on the transition delay. The aerodynamic performances of the airfoils designed are compared with those of the ss1f airfoil, which was designed for the Mars exploration airplane during the ARES project. The objectives of optimization are to minimize the drag coefficient with a fixed lift coefficient and to minimize the moment sensitivity with respect to the angle of attack. Transition of the airfoil using the PARSEC representation occurs further downstream than that of the ss1f airfoil. Furthermore, the airfoil using the NURBS representation achieves fully laminar flow on the upper surface. The moment sensitivity of the optimized airfoils is also lower than that of the ss1f airfoil.
Purpose:
To design, construct, and commission a set of computer-controlled motorized jaws for a micro-CT/RT system to perform conformal image-guided small animal radiotherapy.
Methods:
The authors ...designed and evaluated a system of custom-built motorized orthogonal jaws, which allows the delivery of off-axis rectangular fields on a GE eXplore CT 120 preclinical imaging system. The jaws in the x direction are independently driven, while the y-direction jaws are symmetric. All motors have backup encoders, verifying jaw positions. Mechanical performance of the jaws was characterized. Square beam profiles ranging from 2 × 2 to 60 × 60 mm2 were measured using EBT2 film in the center of a 70 × 70 × 22 mm3 solid water block. Similarly, absolute depth dose was measured in a solid water and EBT2 film stack 50 × 50 × 50 mm3. A calibrated Farmer ion chamber in a 70 × 70 × 20 mm3 solid water block was used to measure the output of three field sizes: 50 × 50, 40 × 40, and 30 × 30 mm2. Elliptical target plans were delivered to films to assess overall system performance. Respiratory-gated treatment was implemented on the system and initially proved using a simple sinusoidal motion phantom. All films were scanned on a flatbed scanner (Epson 1000XL) and converted to dose using a fitted calibration curve. A Monte Carlo beam model of the micro-CT with the jaws has been created using BEAMnrc for comparison with the measurements. An example image-guided partial lung irradiation in a rat is demonstrated.
Results:
The averaged random error of positioning each jaw is less than 0.1 mm. Relative output factors measured with the ion chamber agree with Monte Carlo simulations within 2%. Beam profiles and absolute depth dose curves measured from the films agree with simulations within measurement uncertainty. Respiratory-gated treatments applied to a phantom moving with a peak-to-peak amplitude of 5 mm showed improved beam penumbra (80%–20%) from 3.9 to 0.8 mm.
Conclusions:
A set of computer-controlled motorized jaws for a micro-CT/RT system were constructed with position reliably better than a tenth of a millimeter. The hardware system is ready for image-guided conformal radiotherapy for small animals with capability of respiratory-gated delivery.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Vapor injection heat pumps have been proposed for cabin heating in electric vehicles (EVs) to improve the performance and reliability under severe weather conditions. However, the geometric ...optimizations of the injection-port and internal heat exchanger (IHX) in vapor injection heat pumps designed for EVs have rarely been investigated. The objective of this study is to investigate the effects of the injection-port angle and IHX length in a vapor injection heat pump for use in EVs at various startup conditions. The heating performance of a vapor injection heat pump with R134a is measured by varying the IHX length from 100 to 400 mm and injection-port angle from 320° to 440° at various cabin temperatures. The effects of the IHX length and injection-port angle are analyzed in terms of coefficient of performance (COP) and heating capacity. The optimum IHX length and injection-port angle for the maximum COP are determined to be 300 mm and 400°, respectively.
•An IHX type vapor injection heat pump for EV is investigated.•Experiments are conducted under various startup conditions.•Effects of design parameters on the heating performance are analyzed.•The optimum injection-port angle and IHX length are suggested in terms of COP.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•A simulation model for an EV heat pump with vapor injection is developed and validated.•Geometries of the injection port are analyzed according to angle of the injection port.•Design of the ...injection port is determined to optimize COP and isentropic efficiency.•Performance of dual-injection ports is compared to that of the non-injection heat pump.
Heat pumps, which enable the cooling and heating of vehicular cabins, consume a significant portion of the total energy consumption in electric vehicles (EVs). The efficiency of the heat pump is typically degraded owing to cold-weather conditions, so the refrigerant-injection technique has been proposed for improving the system performance and compressor reliability. In this study, a simulation model for an R134a heat pump with vapor injection is developed and validated by performing thermodynamic analyses with geometrical information. The effects of the injection-port design are investigated using the developed numerical model. Single-injection and dual-injection ports are considered to optimize the coefficient of performance (COP) and isentropic efficiency by controlling the injection mass flow rate. The optimal angles of the single- and dual-injection ports are determined to be 440° and 535°/355° (for pocket A/B), respectively, while the corresponding COPs are improved by 7.5% and 9.8%, respectively, compared to the non-injection heat pump at an outdoor temperature of −10°C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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