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The purpose of this work is to improve flow-induced noise for the centrifugal fan with quarter-wave resonator by design scheme, mockup fabrication, and experimental test. At first, the cascade theory is utilized to generate the three-dimensional fan configuration which is fabricated for performance and acoustic tests later. Next, FFT is applied to measure the noise for comparison and evaluating the effect of quarter-wave resonator. To reduce the fan noise, a set of quarter-wave resonator of this centrifugal fan are designed and fabricated on the centrifugal fan. Consequently, the flow-induced-noise reduction due to the aerodynamics is examined and discussed in details. In conclusions, a comprehensive parametric study on quarter-wave resonator is carried out and summarized for attaining a design guideline for its application on centrifugal fan. The accomplishment of this study provides a systematic scheme of noise reduction for a centrifugal fan with the addition of quarter-wave resonator design.

Generally, most research attempts on the axial-flow fan focus on optimizing rotor blade and tip clearance to enhance its aerodynamic and acoustic performances. Few efforts aim at finding out the appropriate frame rib, which is a supporting and vital part within the air passage and thus has significant influence on the turbulent flow near the blade trailing edge. Therefore, this study intends to investigate the geometrical parameters of the frame rib systematically by using an integrated scheme, which consists of numerical simulation, mockup fabrication, and experimental verification. At first, a high-performance fan (90×90×38 mm3) is constructed to serve as the sample fan for this investigation. Then three geometrical sections (triangle, cylinder, and arc) of frame rib are examined systematically to provide a design guideline on utilizing the appropriate frame rib for enhancing the fan performance.

This study analyzes the flow flied and the guide vane associated with an in-line fan by an integrated numerical and experimental investigation. At first, the flow field associated with the fan is simulated by using a commercial CFD code Fluent with the finite volume method. In addition, the guiding vane profile is imposed and modified by examining characteristics of flow field. An appropriate guiding vane with high-performance and low-noise feature can be achieved after several design iterations. To manufacture the mock-up for experimental verification, the designed fan is expressed in the CAD/CAM format for the rapid-prototype technique. Moreover, a set of relations correlating the performance and noise of this fan prototype are executed with the aids of AMCA test chamber and semi-anechoic chamber, respectively. Consequently, the feasibility of design scheme and numerical system can be verified according to these experimental results. In summary, this work provides a systematic scheme for designing and analyzing the in-line fan.

As Taiwan is located in subtropical zone, it has a high temperature and high humidity climate, and the mean annual relative humidity is higher than 70%. Therefore, the air conditioning products are daily necessities. The split-type air conditioner was used extensive. However, as limited to its mechanical structure, most of split-type air conditioners lack the air change function, so that the air quality in the air conditioned space declines. At present, the split-type air conditioner with air change function has been developed and commercialized. This paper attempts to experiment tested the air conditioner in an office work environment, and measured the concentration of CO2 under different conditions, so as to validate the fitness of this equipment in office work environment. It is found that after two hours, the CO2 concentration have been over 2600 ppm in the office without outdoor air inlet. The split-type air conditioner with air change function can reduce the CO2 concentration and accumulate, the indoor CO2 concentration can maintain 500 ppm when one person within office environment.

AbstractThis study numerically investigated the flow return system performances of two-stage high pressure fans. The parameters include inflow angle, length, exit width of vaneless diffuser and the blade number of deswirl vane. This study used the tested impeller to verify the accuracy of numerical calculations, with good consistency. The analytic results showed that the overall pressure loss of impeller and flow return system is effectively reduced when the inflow angle of vaneless diffuser is 15° and tangential to wheel velocity ratio is 0.46. A vaneless diffuser was required and its length referred to the maximum outer diameter of the volute casing. The performance of a contracted-wall vaneless diffuser was not improved over that of a parallel-wall one. The suggested number of blades in a deswirl vane was 12. The downstream affects the upstream in several areas inside the flow return system, thus, the flow return system must be calculated integrally.

IMPORTANCE: Definitive chemoradiotherapy and upfront surgical treatment are both accepted as the standard of care for advanced-stage oropharyngeal squamous cell carcinoma. However, the optimal primary treatment modality remains unclear. OBJECTIVE: To evaluate the comparative effectiveness of definitive chemoradiotherapy and upfront surgical treatment for advanced-stage oropharyngeal cancer. DESIGN, SETTING, AND PARTICIPANTS: This retrospective comparative effectiveness analysis used data from the population-based Taiwan Cancer Registry. Included patients were diagnosed with clinical stage III or IV oropharyngeal squamous cell carcinoma from 2007 to 2015 and were identified from the registry. Patients with T4b or N3 disease were excluded. Data were analyzed from June 2019 through December 2020. INTERVENTIONS: Definitive chemoradiotherapy or upfront surgical treatment. MAIN OUTCOMES AND MEASURES: The primary outcome was overall survival, for which data were available through December 31, 2018. Secondary outcomes were progression-free survival, locoregional recurrence–free survival, and distant metastasis–free survival. RESULTS: Among 1180 patients, 694 patients (58.8%) were in the definitive chemoradiotherapy group and 486 patients (41.2%) were in the upfront surgical treatment group. The median (interquartile range) follow-up was 3.62 (1.63-5.47) years, and most patients were men (1052 [89.1%] men) with a primary tumor in the tonsils (712 patients [60.3%]), moderately differentiated histology (604 patients [51.2%]), clinical N2 disease (858 patients [72.7%]), and clinical stage IVA disease (938 patients [79.5%]). The mean (SD) age was 54.59 (10.35) years. Primary treatment with an upfront surgical procedure was associated with a decreased risk of death during the study period (hazard ratio [HR], 0.81; 95% CI, 0.69-0.97; P?=?.02). However, when adjusted for age, subsite, histological grade, and T and N classification, upfront surgical treatment was no longer associated with an increased risk of death during the study period (HR, 0.96; 95% CI, 0.80-1.16; P?=?.70). Progression-free survival was worse in the group receiving upfront surgical treatment than in the group receiving chemoradiotherapy (HR, 1.64; 95% CI, 1.09-2.46; P?=?.02), and this difference persisted after adjusting for other factors associated with prognosis (ie, age, tumor subsite, histological grade, and T and N classification) (HR, 1.72; 95% CI, 1.12-2.66; P?=?.01). CONCLUSIONS AND RELEVANCE: This study found that definitive chemoradiotherapy was associated with effectiveness that was comparable with that of upfront surgical treatment when adjusted for baseline factors associated with prognosis. These findings suggest that definitive chemoradiotherapy should be considered to avoid accumulating toxic effects associated with surgical treatment and chemoradiotherapy.