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.     

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.     

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.     

SPSM and its application in cylindrical shells

In naval architectures, the structure of prismatic shell is used widely. But there is no suitable method to analyze this kind of structure. Stiffened prismatic shell method (SPSM) presented in this paper, is one of the harmonic semi-analytic methods. Theoretically, strong stiffened structure can be analyzed economically and accurately. SPSM is based on the analytical solution of the governing differential equations for orthotropic cylindrical shells. In these differential equations, the torsional stiffness, bending stiffness and the exact position of each stiffener are taken into account with the Heaviside singular function. An algorithm is introduced, in which the actions of stiffeners on shells are replaced by external loads at each stiffener position. Stiffened shells can be computed as non-stiffened shells. Eventually, the displacement solution of the equations is acquired by the introduction of Green function. The stresses in a corrugated transverse bulkhead without pier base of an oil tanker are computed by using SPSM.     

Theoretical and experimental analysis of a CNG cylinder rack connection to a bus roof

From our perspective, a global technology development should be focused on resolving the issues of environmental impact and conservation of available natural energy resources. New technological solutions and alternative fuels, such as Compressed Natural Gas (CNG), have increasingly more application for modern engines and vehicles. If we take into account the situation in city transport, where primarily vehicles with diesel engines are used, a strategic proposal is to begin by retrofitting these into bi-fuel or dedicated Natural Gas Vehicles (NGVs). This paper analyzes the retrofit of a diesel bus into dedicated NGV. To confirm the safety of the vehicle in city transport, we addressed the problem of mounting a gas rack with CNG cylinders on the roof of a retrofitted city bus, according to UN ECE Regulation No. 110. This assembly is the most critical part of the retrofitted bus because of the concentration of stress due to increased mass and the application of a specific installation for supply of CNG from the cylinders to the engine. These regulations must be met in all parts of the vehicle, but we only focused on those areas affected by the retrofit to NGV.     

船体表面矩形块优化敷设设计(英文)

Rectangular tiles can be laid on a ship’s hull for protection, but the sides of the tiles must be adjusted so adjacent tiles will conform to the curvature of the hull. A method for laying tiles along a reference line was proposed, and an allowable range of displacement for the four vertices of the tile was determined. Deformations of each tile on a specific reference line were then obtained. It was found that the least deformation was required when the tiles were laid parallel to a line with the least curvature. After calculating the mean curvature on the surface, the surface was divided into three layout areas. A set of discrete points following the least deformation of the principal curvatures was obtained. A NURBS interpolation curve was then plotted as the reference line for laying tiles. The optimum size of the tiles was obtained, given the allowable maximum deformation condition. This minimized the number of bolts and the amount of stuffing. A typical aft hull section was selected and divided into three layout areas based on the distribution of curvature. The optimum sizes of rectangular tiles were obtained for every layout area and they were then laid on the surface. In this way the layout of the rectangular tiles could be plotted.