Fuel Property Effects on Liquid and Vapor Penetrations of Evaporating Sprays

The purpose of this study is to investigate the effect of fuel properties on liquid and vapor penetrations in evaporating spray systems. A recently developed model, which can simultaneously account for the finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing multi-component liquid fuel sprays, is utilized for the numerical predictions. Two different multi-component fuels with different boiling temperatures, densities and other thermal properties are implemented in the KIVA-3V computational fluid dynamics (CFD) code to study the evaporation behaviors. A six-component surrogate fuel is used to emulate the relevant volatility property of the real diesel fuel, and a second bi-component fuel is chosen to represent a low boiling-temperature fuel. The numerical results are compared with the experimental data, and the representative results are obtained. For a lower density and lower boiling temperature fuel, the liquid penetration length is shorter. However, the vapor penetration lengths are not affected by the fuel type in terms of fuel volatility. Available experimental data are used for validation and appraisal of the multi-component evaporation model.     

Flame propagation model for a rotary Atkinson cycle SI engine

The rotary Atkinson cycle engine includes two modes of combustion: combustion initiation and propagation in ignition chamber and then flame jet entrainment and propagation in expansion chamber. The turbulent flame propagation model is a predictive model for SI engines which could be developed for this type of combustion for the rotary Atkinson engine similar to the congenital engine with pre-chamber; in split combustion chamber SI engines, small amount of fuel is burned in pre-chamber while the fuel burned in ignition chamber of rotary Atkinson cycle is considerable. In this study a mathematical modeling of spherical flame propagation inside ignition chamber and new combined conical flame and spherical flame propagation model of a new two-stroke Atkinson cycle SI engine will be presented. The mathematical modeling is carried out using two-zone combustion analysis and the model also is validated against experimental tests and compared with previous study using non-predictive Weibe function model.     

The Value of a Spillover Fishery for Spiny Lobsters Around a Marine Reserve in Northern New Zealand

The contribution that Leigh Marine Reserve in northern New Zealand makes to the local spiny lobster fishery was examined by comparing the catch characteristics of Jasus edwardsii around the reserve boundary with those from Coastal Leigh, 0.3-2 km from the reserve, and Little Barrier Island, 22-30 km from the reserve. Seasonal trends were apparent in the reserve catch characteristics, consistent with lobster movements into and out of offshore fishing areas adjacent to the boundary. No significant difference was detected in catch per unit effort (kg.trap haul -1 ) among locations. However, the catch around the marine reserve consisted of fewer but larger lobsters than at Little Barrier Island, while the size and number of lobsters caught per trap haul at Coastal Leigh was intermediate between the other two locations. Catch rates around the reserve were more variable than at the other sites, but on average, the amount of money made per trap haul was similar to Little Barrier Island and Coastal Leigh.     

DC Motor Current Control Algorithm Using Proportional-Integral LQT with Disturbance Observer

This paper proposes a DC motor current control algorithm using a proportional-integral linear quadratic tracking (LQT) controller with a disturbance observer for the electronic stability control (ESC) brake system. Previously researched algorithms related to current control using disturbance rejection are robust control, adaptive control, LQT, or proportional-integral disturbance observer (PI-DOB); each of them has both advantages and disadvantages. The proposed algorithm uses a disturbance observer in order to improve disturbance rejection performance while avoiding the drawbacks of high gain property. Additionally, the proposed algorithm adds integral control in order to improve performance in the low frequency bands. In order to assess the performance of the proposed algorithm, simulations and experiments are performed in the time and frequency domains to compare the proposed algorithm with different algorithms which are actually implemented into the ESC. The proposed algorithm shows good characteristics near the cut-off frequency, which can be confirmed clearly by the time domain results.     

Electrically Assisted Internal Combustion Engines: A Comparative Analysis

An electrically assisted internal combustion engine is obtained by combining a conventional engine and one or more electrical motors of considerably smaller size. A key feature of such an innovative vehicle hybridization approach is that the torque generated by electric machines is not transmitted to the wheels. The electric motors are, in fact, intended only to assist the internal combustion engine in low efficiency, low performance, or high polluting working conditions. They however, draw extra power and energy from the battery. This paper presents a tool to evaluate different possible solutions in terms of energy balance, efficiency, battery stress and battery ageing. The method, which is based on suitable mathematical models and specific analysis criteria is also exploited to compare eight different configurations of a C-segment vehicle, pointing out limits and capabilities of traditional 12?14 V systems.     

Development of hydrogen-compressed natural gas blend engine for heavy duty vehicles

Natural gas fuel, as an alternative energy source of transportation, has been used widely since it has an advantage of low emission levels. However, new technologies are required in order to meet the reinforced emission regulations. For this purpose, research into the development of hydrogen-compressed natural gas (HCNG) blend engine was carried out to evaluate its feasibility and emission characteristics. The Engine Research Department at the Korea Institute of Machinery and Materials carried out a large number of tests based on various parameter changes that could affect the performance and emission of HCNG engine in different operating conditions. An earlier stage of the research project focused on the lean combustion of a HCNG engine for heavy duty vehicles to meet the EURO-VI standards. An 11-L/6-cylinder CNG engine was used for the test. The effects of the excess air ratio change were assessed based on various content ratios of hydrogen in the natural gas fuel. In the later part of the HCNG research, a stoichiometric mixture operation was suggested to meet reinforced emission regulation without requiring a De-NOx system. Additionally, an exhaust gas recirculation (EGR) system was introduced for the purpose of improving thermal efficiency and durability. The optimal operating conditions were selected to achieve the best thermal efficiency to meet the required emission levels. In this paper, we demonstrate that a HCNG engine can achieve a significant decrease in NOx emissions, as compared to that of a CNG engine, while meeting the requirements of the EURO-VI standards during a transient mode cycle test. EGR can suppress the weakness of stoichiometric mixture combustion strategy, such as the deterioration of the durability and thermal efficiency, while the emission level can be lowered with the use of a three-way catalyst. The possibility of further reduction of emissions and CO2 with EGR was evaluated to access practical application of a HCNG engine in the field. From that evaluation, the HCNG engine with stoichiometric mixture operation for heavy duty vehicles was developed. The emission levels of HCNG engine were 50 % lower when compared to the EURO-VI standards with a greater than 10 % decrease in CO₂ compared to that of a natural gas engine.     

砂灰比和砂的级配对CA砂浆抗压强度和流动性的影响

通过调整砂与水泥的质量比和调整2种单级配砂的质量比，研究了砂灰比和砂的级配对CA砂浆的抗压强度和流动性的影响。结果表明：随着m（S）／m（C）的增大，低强和高强CA砂浆的流动性都变差，但低强CA砂浆流动性的变化幅度较小；随着m（S）／m（C）的增大，高强CA砂浆的抗压强度降低，而低强CA砂浆的抗压强度呈升高的趋势；使用两级配砂能够提高CA砂浆的抗压强度并改善其流动性，粒径为0．42-0．21mm的砂与粒径0．85-0．30mm的砂的最佳质量比为6：4。     

Grid convergence study in the resistance calculation of a trimaran

As a new type of hull form, trimaran has remarkable excellent performances and has drawn more and more attention. When the viscous CFD technology now available is applied to the research of resistance performance of trimaran, the spatial discretization would usually result in the grid error and uncertainty, and thus the considerable discrepancy between the numerical results and the experimental data. In order to ascertain how much the grid would affect the calculation, the grid convergence should be studied. A mathematical trimaran was chosen as an example, with the commercial code CFX for the simulation, VOF for surface treatment, and the grid study was carried out based on two different turbulence models. It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty, and indicating the direction of improving the credibility of the numerical calculation, and, in addition to grid errors and uncertainties, the turbulence modeling errors and uncertainties contribute to the simulation errors.     

Research on techniques to improve accuracy in SBL locating systems

Short baseline system （SBL）, which is a kind of underwater acoustic locating technology, has widely applicable value. In order to examine the capability of ship model design, the ship model experimentation should have high accuracy. This paper focuses on the key techniques of high accuracy locating system, including high accuracy sub-array position emendation, divisional locating, anti multi-path interference measure, etc. Experiments show that the SBL locating systems has received the satisfying effect owing to these key techniques proposed in this paper.