In this paper, the effects of injection parameters on combustion and particulate size distribution of partially premixed combustion (PPC) fuel with n-butanol were investigated experimentally. High concentrations of particle emission for the n-butanol PPC combustion are observed. The particle sizes are primarily concentrated within 64nm. With the advance of the start of injection (SOI) timing, more particles are formed and the particulate size distribution curve shifts towards right (larger size). In addition, the pilot-main injection strategy can effectively reduce the maximum pressure rise rate (MPRR). Furthermore, through adopting appropriate injection parameters, the MPRR and particle number can be reduced simultaneously, while still maintaining a comparable indicated thermal efficiency compared to the single injection strategy.
Ultra-high heat flux cooling has become a research hotspot owing to its wide application in thermal engineering fields. Only by exploring its internal physical mechanism and calculating the CHF (critical heat flux) of different surfaces, can the necessary theoretical basis be provided for the design and optimization of pool boiling heat exchange in engineering applications. Previous models cannot accurately predict CHF value due to the limitations of their physical models. In this paper, a new theoretical physical model was obtained to predict CHF value of pure liquid on a heated surface. The theoretical model proposed a new CHF trigger mechanism based on the bubble behavior near the heater surface. A three-dimensional force balance of a separated bubble was analyzed at CHF condition to derive the analytical correlation for CHF value. The correlation considers the effect of hydraulic pressure, surface tension, liquid properties as well as the contact angle of the heater surface. The predicted values of CHF value on heated surfaces obtained from the present model were found in agreement with existing experimental data within a wide range. It is shown that CHF is mainly affected by factors of adhesion force and hydraulic pressure.
The dynamic responses of Solid oxide fuel cell (SOFC) power system across multiple time scales from micro seconds to minutes due to the phenomena of different nature that governing. Mismatching the time scale differences may lead to fuel starving and thermal shock during the fast load following. In this paper, the singular perturbation (SP) theory was introduced for modeling the mutli-time scale system dynamics. The dynamic model of SOFC power system in the coordinates in which slow and fast variables were explicitly defined and exactly separated. The resulting multi-single time scale models facilitate a better understanding of system dynamics, key parameters and their interactions, such as temperature, mass flow rate, current and voltage. Effective SOFC power system controllers can be designed based on these results.
Hydro power production strictly depends on the geography and weather peculiarity of locations where power plants are settled. In this paper, we produce long term estimates of hydro power capacity factors for all European countries based on future climate scenarios. We use machine learning techniques for formalizing models able to capture the complex relation between climate variables and energy production on a European scale and use the results of regional and global climate models for future projections.
The combustion characteristics of biomass in the packed bed is investigated based on the CFD-discrete element method (DEM). During the combustion process, the biomass particle experienced drying, pyrolysis, combustion and cooling. The mass loss leads to the change of particle density and diameter, as the remnant composition is mainly ash. In this work, the shrinkage of packed biomass volume is modelled as the particle diameter is decreased based on DEM. The different effects of compositions in the particle on particle diameter are considered. The simulation results show good agreement with the experimental measurement.
The long‐term production of U.S. tight oil is forecast by using a composite model combining the Generalized Weng and Gompertz models. We show that U.S. tight oil production is likely to reach a peak within ten years, between 2019 and 2028, at a production rate between 7 and 13 million barrels per day (Mb/d), depending on the size of the ultimately recoverable resource (URR) estimate. Our most‐likely ‘medium‐case’ URR scenario suggests the peak year is probably around 2025, at a production rate of about 10 Mb/d. Comparing our results with those of the U.S. Energy Information Administration (EIA) suggests that the EIA is over‐optimistic in its long‐term production forecast of U.S. tight oil.
Aiming at the demand of comprehensive vulnerability assessment in shipboard power system security defense, the paper proposed a vulnerability status description model of shipboard power system. The structure and physical properties of shipboard power network were fully analyzed. The product space which was called shipboard power network comprehensive vulnerability index set was established by degrees, betweenness, maximum connection sub-diagram scale, reliability indexes. Secondly, the normalized index sets were compactness and thepnormon the compactness sets were continuous were proved in this paper. The norm of vulnerability index was vulnerability output equation of shipboard power system. Using the norm on the product space, multi-scale integrated shipboard power network vulnerability norm was proposed, and the comprehensive structure performance evaluation of the shipboard power system network was formed. The index describes the change tendency of the shipboard power network comprehensive vulnerability. Finally, the test on a certain type of shipboard power network demonstrates the validity of the model.
Microthrusters are special category of propulsion device used to propel micro sized satellites. It is designed as per the mission requirements. There are various kinds of propulsion requirements such as continuous mode operation for orbit transfer (from one planet to another), orbit shift or adjustment for asteroid mining, pulsed mode operation for attitude control of satellites, and gravitation or solar drag compensation in orbit. Continuous mode operation is a high propellant consuming operation and designed cautiously to reach the destination with onboard available propellant. While pulsed mode operation is widely used for LEO (Low earth orbit) applications, where gravitation drag, atmospheric drag and solar drags are dominating. This paper focuses on the pulsed mode operation of vaporization liquid microthruster in vacuum operating condition. The pulsed mode operation involves timely thrust generation for the fine tuning of the positioning of the microsatellites. The operational timing in this mode of operation ranges from milliseconds to a few seconds at maximum. The operating time is decided based on the adjustment requirement for the positioning of the microsatellites. Vaporizing liquid microthrusters use green propellant to produce thrust. Tests are conducted under vacuum condition to simulate the actual space conditions and corresponding results are plotted. Results has shown a maximum thrust value of 290 μN at 1 sec of valve operating time, 335 μN at 2 seconds, 413 μN at 3 seconds, 524 μN at 4 seconds and 590 μN at 5 seconds of valve operating time for 200°C of a constant VLM temperature respectively. The effect of the dibble volume has also been discussed for the vaporization liquid microthruster using di-ionized water as liquid propellant.
In this paper, the performance of the moving average and moving median load estimation techniques is investigated using aggregated measurements of domestic smart meters. The load estimation techniques were tested using forward and backward walk approaches. Forward walk aims to estimate future load measurements using past measurements while backward walk estimates missing past measurements of the load using more recent measurements. Simulation results show that the moving average combined with forward walk produces load estimates with higher accuracies than the moving median and backward walk.
Electricity thefts in connivance with employees of electricity distribution companies, remain the Achille’s heel of power sector, addressing which continue to be the holy grail. The lackluster performance of technological measures to curb electricity thefts highlights the need to investigate the human aspectstoo. That’s what this study aims at. The findings, grounded in the responses of the nineteen employees of the Indian electricity distribution companies, detail the factors that induce employees to collude with consumers in electricity theft.