This paper aims to evaluate the potential of heat recovery from the integrated heat exchanger within the exhaust stack silencer baffles in a simple cycle gas turbine. Heat transfer channels were ...incorporated into the upstream (nose) and downstream (tail) sections of the parallel silencer baffles in the exhaust stack. The gas turbine exhaust gas represents the hot side flow across the baffles' sections. The integrated heat exchanger system offered an advantage of extracting waste heat from the exhaust stream, while reducing pressure drop on the flow and improving acoustic attenuation.
In this work, a series of parametric studies were carried out across a range of internal and external heat transfer area configurations within the silencers to maximize the heat transfer. Further enhancement opportunities were introduced and discussed based on the conducted parametric studies and practical aspects borne out of common industry practice. The proposed heat recovery system was implemented to power the gas fuel performance heater which is used to enhance the gas turbine cycle performance through utilization of the extracted waste heat while keeping lower exhaust pressure drop in the stack.
The obtained results showed that the proposed integrated heat exchanger within the silencers has a potential of generating a 5.48 MW net gain from the gas turbine exhaust stacks which are normally lost to the atmosphere from the simple cycle exhaust stack. The proposed heat recovery system proved significant fuel savings that lead to economic benefits and reduction in CO2 emissions.
This article summarises the development and experience of the Formula Student race car engine from 2018. According to the technical rules of Formula Student after the change in 2017, this engine ...adopts a new design concept, employs a 690-mL single-cylinder engine as the base, and applies ‘response enhancement technology’ with supercharging as the core to achieve a high-power output, a wide high-torque range and an excellent response capability. During the development, various studies on the dynamic performance of the vehicle and the engine were conducted, including vehicle dynamics analysis and track simulation, parameter matching of the supercharger and the engine, control strategy design, and the intake and exhaust system design. This research builds a supercharger air flow and efficiency test bench and an engine performance test bench. Test results show that the developed engine can output 122% of the original power and 120% of the original torque with a 20-mm diameter intake restrictor. Compared with previous generation race cars with a turbocharged four-cylinder engine, the new race car‘s 0–100 km/h acceleration time is shortened by 0.2 s, the torque response time under typical condition is shortened by 80%, and the lap time of the integrated circuit is reduced by 7%.
Fig. 1. The graphical abstract of current work.
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•The exhaust flue pressure and air volume distribution were analyzed by full-scale tests.•The air leakage coefficient of the exhaust ...flue and the exhaust vent were established.•Two calculation methods for the applicable limit length of the ceiling centralized smoke exhaust system were established.
Based on the Jiangxinzhou Yangtze River Tunnel, this study investigated the air leakage of a ceiling-centralized smoke exhaust system through full-scale tests and theoretical analysis. The theoretical analysis established a functional relationship between the pressure of the exhaust vent and air leakage volume. The air leakage coefficient of the exhaust vent was defined. The exhaust vent air leakage coefficient, exhaust flue area, hydraulic diameter, resistance coefficient along the exhaust flue, and exhaust vent spacing were integrated to establish the exhaust flue air leakage coefficient. Through full-scale tests, the exhaust flue pressure and air volume distribution were analyzed under different opening schemes of the exhaust vent. A section-by-section calculation method was established for the applicable limit length and air leakage of the ceiling centralized smoke exhaust system. This study further established a simple calculation method for the applicable limit length of a ceiling centralized smoke exhaust system through theoretical analysis, which made the calculation simple and easy to perform and enabled the results to be calculated with a certain degree of accuracy.
Along with the diversification and sophisticated development of detection methods in modern warfare, helicopters are increasingly subject to unilateral or simultaneous threats from radar and infrared ...detectors. In order to improve the survivability and operational effectiveness of the helicopter, a comprehensive stealth approach based on Pareto solution is presented. Considering the geometric constraints and aerodynamic characteristics of the engine intake and exhaust system, the model of the system is established by the full factorial design, the internal, central and external flow fields are constructed, then the high-precision computational fluid dynamics method is used to simulate the total flow field under the rotor downwash airflow in hovering state. The radar cross section of the system is evaluated by the physical optics and physical theory of diffraction. Based on the Monte Carlo and ray tracking method, the infrared signature of the system is calculated and analyzed in detail. Under the comprehensive evaluation and selection of comprehensive stealth approach, the optimization model of the system is continuously established and updated. The ultimate design has achieved good results in both radar cross section reduction and infrared radiation suppression and the proposed method is effective and efficient for radar/infrared integrated stealth of helicopter engine intake and exhaust systems.
•Developed mathematical model for kitchen exhaust system.•Model accuracy improved for different opening rates.•Thermal pressure affects kitchen exhaust in high-rise buildings during winter.
In ...high-rise buildings with large indoor and outdoor temperature difference, neglecting the effect of stack effect in smoke exhaust shafts may cause calculation error of the fluid network model. In this paper, the mathematical model of kitchen smoke exhaust system considering the influence of stack effect was put forward and it can be inserted different range hood sub-models. Compared with the results of six working conditions of the model without considering the stack effect, the error of the proposed model were reduced by 7.6%, 4.3%, 4.1%, 2.8%, 2.4%, and 2.1%. While the indoor and outdoor temperature difference varies from −5 °C to 49 °C, the effect of stack effect on the pressure in the flue and the flow rate for each user was studied for six operating rates s. The results show that under the combined effect of stack effect and flue resistance, the static pressure of the kitchen smoke exhaust system showed a low-high-low distribution, and the maximum static pressure in the flue moved toward the bottom with the increase of temperature difference. User flow rates exhibit a low-high-low-high distribution, with an increased flow rate in the bottom users and the largest flow rate in the top users.
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•Field tests of static pressure and exhaust flow were conducted under different operating rates.•The effect of temperature differences and operating rates were studied by CFD.•The ...suggestions for improving exhaust shafts design and choosing suitable kitchen hoods were proposed.
With the increasement of worldwide population, high-rise buildings of multi-dwelling units have been widely used as a residential building, especially in China, United States and India etc. At present, most of cooking exhaust shafts in high-rise residential building takes the form of central exhaust system. However, the mal-distribution of exhaust flow in central exhaust system often leads to oil fumes reflux and odor migration, which decreasing the performance of kitchen hoods. This study is conducted in a 32-storey residential building which employed central exhaust system. Static pressure and velocity distribution were investigated in central exhaust shaft with uniform cross section. In addition, Computational Fluid Dynamics was adopted to analyze flow characteristics and validated by comparing the simulation results with experimental data. The emphasis of this study lies in the effects of temperature differences and equally spaced operating rates of kitchen hoods on flow characteristics in central exhaust shaft. The results showed that when the temperature difference varies from −12°C to 30°C, the locations of maximum static pressure gradually moved downwards and presented a low-high-low distribution. The maximum occurred in the middle-low storeys under different operating rates. This paper is valuable for HVAC engineers to improve the design of central cooking exhaust shafts in high-rise residential buildings, and solve the mal-distribution problems of exhaust flow in central exhaust systems.
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