Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Miniature gas turbines : numerical study of the effects of miniaturization on the performance of compressor

Micro Gas Turbines (MGT) are an attractive choice for Unmanned Aerial Vehicles (UAV) and small-scale power generation. Compared with other propulsion systems, MGT have several advantages including high power-to-weight ratio, availability for various fuels, endurance and others. However, the direct miniaturization of conventional gas turbines designed at large scales may induce performance loss. Therefore, the effects of miniaturization on gas turbines need to be investigated. In this research, an axial compressor in a gas turbine is studied, to understand the effects of the miniaturizing process. Using a numerical approach, parameter studies are conducted on three of the most important parameters during the miniaturizing process: the Reynolds number effect, the increased heat transfer and the tip clearance. The NASA Stage35 compressor is selected as the configuration in this study. Firstly, a thorough validation of the computational tools and methods is conducted, suggesting the suitability of the numerical methods for follow-up study. Then, the effect of Reynolds number is investigated, in the range of Re 2.14e5 to Re 8.54e5. Our results indicate a drop of performance with the decrease of Reynolds number, due to the increased viscous effect in boundary layer when compressor is miniaturized. Thereafter, the effect of heat transfer is investigated due to thermal conduction; adiabatic wall conditions, constant heat transfer coefficient conditions and isothermal conditions are applied, respectively. The results indicate that the increased heat transfer from internal flow to the ambient air will actually benefit compressor performance, but the heat transfer from the downstream combustor to the compressor has an adverse effect on compressor overall performance. Subsequently, the effect of tip clearance (TC) is investigated, with varying TC value and varying Reynolds number. Our results indicate that the existence of TC has an adverse effect on compressor performance, and the loss of performance amplifies during the miniaturization process.DOCTOR OF PHILOSOPHY (MAE

A numerical parametric and optimization study of an industrial air-slide conveyor system

A numerical investigation has been conducted to model the cement flow behaviour associated with a full-scale industrial air-slide conveyor (ASC) system. Steady-state simulations on the ASC were performed to predict its operational and the cement flow characteristics, and comparisons with actual operational data of the ASC demonstrate satisfactory agreement. Subsequently, hopper input loading, velocity as well as the suction fan pressure were varied and simulated to identify how cement conveying capacity by the ASC may be increased. Simulation results indicate that an increase in air chamber pressure leads to a corresponding increase in conveying capacity because of the enhanced capability of air chamber to sustain the cement flow, whereas increasing hopper input velocity and suction fan pressure both lead to lower demands in the air chamber pressure required to sustain existing conveying capacity. Detailed results associated with the cement and air flow mixture behaviour within the ASC reveal that, while the cement and air mixture flow is highly complex and three-dimensional, gross trends between the various operational parameters can be isolated successfully and may offer insights into how the existing ASC may be modified to increase conveying capacity.Accepted versio

Towards simulation of NASA35 axial compressor

Purpose – This paper aims to validate and analyse the NASA35 axial compressor performance based on a numerical approach. Design/methodology/approach – Knowledge about flow property change during compressor operation at high and relatively low speed is still limited. This work provides a numerical approach to address these problems. Validation of numerical methods is proposed to generate confidence the numerical approach adopted, and after that, analysis of compressor performance at different operation conditions is carried out. Findings – The numerical methods proposed are proved capable in predicting compressor performance. Changes of flow property during compressor operation are discussed and explained. Research limitations/implications – The current numerical work is carried out based on the first stage of the NASA35 axial compressor, where the interactive effects from adjacent stage are not counted in. Furthermore, the steady-state simulation enforces an averaging of flow at rotor-stator interface, where the transient rotor-stator interaction is removed. Practical implications – This work validates the numerical methods used in the prediction of NASA35 axial compressor performance, and a similar numerical approach can be used for other turbomachinery simulation cases. Originality/value – This work reinforces the understanding of axial compressor operation and provides reliable results for further investigation of a similar type of compressor. In addition, details of flow field within the NASA35 compressor during operation are given and explained which experiments still have difficult to achieve