基于GT-Power的增压柴油机进排气系统参数敏感性分析

为进一步明确增压柴油机进排气系统优化仿真过程中寻优变量的选择方向,采用一维性能分析软件GT-Power中自带的DOE功能,对影响发动机整机仿真结果 (动力性、燃油经济性和可靠性)的15个进排气系统特征参数进行了敏感性分析,并完成了各参数敏感度的排序和比较。分析结果表明,进排气系统阻力是进排气系统设计中的2个重要控制量。与进气管路结构参数相比,排气管路结构参数对各项指标的影响更敏感,而且其中的涡轮出口连接管直径、排气总管直径和长度是3个主要设计参数。     

16V190燃气发动机MPC排气系统设计优化

为提升增压器效率,实现降低排气温度的目标,在计算剖析颜巴赫排气系统的基础上,针对颜巴赫机型主要关注排气损失和功率要求,排气总管设计较粗的特点,对国产16V190燃气发动机模件式脉冲转换(modular pulse converter,MPC)排气系统进行设计优化;在满足16V190功率设计要求的前提下,主要从排气管管径设计及排气支管缩口设计对16V190排气管进行对比设计和计算分析,结果表明:优化获得了较低的排温,达到了设计优化的要求。     

提高发动机性能的多目标优化设计

运用AVL/BOOST对发动机性能进行了数值模拟,以进排气提前角、迟闭角和进排气管直径为设计变量,应用目前已成熟的多目标遗传算法对某四冲程发动机的性能进行了优化设计.结果显示,发动机的转矩、功率和燃油经济性都有不同程度的提高.     

BL12V190ZL柴油机的性能模拟计算

本文利用AVL Boost软件对BL12V190ZL型柴油机进行了基于一维气体动力特性的工作循环和气体交换过程仿真,对供油提前角、进排气门正时、增压系统、排气管直径做了优化计算,并对不同转速下发动机性能进行了预测。     

增压柴油机排气系统结构参数的仿真优化

运用GT—POWER软件建立了增压柴油机工作过程仿真模型,深入研究了排气系统结构参数（包括排气管直径、长度、截面变化）对柴油机性能的影响。并基于优化理论,以有效功率为优化目标,分别在标定工况和最大扭矩工况对排气管路结构参数进行了优化计算,为排气管的进一步优化设计提供了依据。     

不同结构因素下方形旋风分离器分离性能的实验研究

通过改变分离器进气形式、排气芯管形状、管径及布置方式，对方形分离器的分离性能进行了实验研究。结果表明：正切向进气形式优于斜切式；排气管直径是重要的结构参数，且方排气管的分离性能要优于同等排气面积的圆排气管。研究结果为方形分离器结构的优化设计提供了依据。图5表4参6     

船用低速柴油机贯入式排气管性能及损失机理研究

采用三维计算流体力学方法(CFD)对某型低速船用柴油机的贯入式排气管系统开展性能预测及流动损失机理研究。研究结果表明:支管相对贯入深度及其末端扩张角对管路系统压力损失系数有显著影响,损失随贯入深度增加逐渐降低,但存在损失最小的最佳扩张角;流场分析显示,支管内气流与总管壁面相互作用形成的涡结构是支管几何结构影响流动损失的主要原因。     

发动机进排气系统建模与仿真

进排气系统是内燃机的重要组成部分,进排气系统的性能直接影响进气和排放的质量。本文用MATLAB/SIMULINK软件对发动机进排气系统进行建模与仿真,通过改变管道直径、长度,研究进排气管结构参数对发动机进排气歧管的影响。并通过油门突变,得到排气歧管出口压力和温度的动态变化曲线,仿真结果对发动机进排气系统的设计具有一定的指导性作用。     

用不稳定流动研究汽油机进排气管的设计

本文分析了由一元不稳定流动为理论基础的管道计算程序(PMB程序)所计算的低压示功图,认为压力波对换气过程有重要影响,特别对排气管更是这样。文中指出:设计进气系统要求在进气门开启时产生一个正的压力波;设计排气系统要求排气时防止其他气缸正压力波的干扰,气门重叠时形成一个负压力波。文中提出用结构简单的容器式排气总管可达到所要求的目的。     

利用文丘里管和VNT提高柴油机EGR率的研究

利用文丘里管和可变喷嘴增压器(VNT)提高柴油机的EGR率,旨在降低柴油机NOx的排放.采用试验的方法研究,对文丘里管喉口直径进行了优化,分析不同的喉口直径对发动机外特性参数的影响;对于VNT系统,分析VNT叶片开度对EGR系统的影响,并在最佳的EGR率下,进行了VNT与旁通增压器的柴油机性能对比.通过文丘里管喉口直径的合理选取和VNT喷嘴环叶片位置的调节,增加涡前与文丘里管喉口的压差及EGR率.结果表明,基于VNT的EGR系统,扩展了EGR率的范围,小负荷的EGR率能达到30%,在保证柴油机动力性、经济性不变的前提下,大大地降低了NOx的排放.     

Parametric study on the performance of the earth‐to‐air heat exchanger for cooling and heating applications

To reduce energy consumption, the earth‐to‐air heat exchanger (EAHE) is a suitable technique for cooling and heating buildings. This paper studies numerically the effect of some design parameters (pipe diameter, inlet condition, pipe length, and outlet condition) on the overall performance of the EAHE system. Four diameters of the EAHE pipe (2, 3, 4, and 6 in) are studied and this numerical study has been done for summer and winter seasons for Nasiriyah city in southern Iraq. First, the built numerical model was validated against the experimental model, and the results of comparison showed a good consensus. After the validation and by using computational fluid dynamics modeling, the overall performance of the EAHE system with all pipe diameters was analyzed with ranges of air velocity, DBT or inlet temperature, and a pipe length of 50 m. The simulated results showed that the EAHE system with 6 in pipe diameter has the best values of overall performance, but from the thermal performance point of view, the 2 in pipe diameter is more suitable.     

Study on the design of inlet and exhaust system of a stationary internal combustion engine

The design and operational variables of inlet and exhaust systems are decisive to determine overall engine performance. The best engine overall performance can be obtained by proper design of the engine inlet and exhaust systems and by matching the correct turbocharger to the engine. This paper presents the results of investigations to design the inlet and exhaust systems of a stationary natural gas engine family. To do this, a computational model is verified in which zero dimensional phenomena within the cylinder and one dimensional phenomena in the engine inlet and exhaust systems are used. Using this engine model, the effects of the parameters of the inlet and exhaust systems on the engine performance are obtained. In particular, the following parameters are chosen: valve timing, valve diameter, valve lift profiles, diameter of the exhaust manifold, inlet and exhaust pipe lengths, and geometry of pipe junctions. Proper sizing of the inlet and exhaust pipe systems is achieved very precisely by these investigations. Also, valve timing is tuned by using the results obtained in this study. In general, a very high improvement potential for the engines studied here is presented.     

叠压供水方式下支管管径对干管水锤影响

长距离输水工程的水锤防护目前多集中于干管研究,而对预留口分支管的研究涉及较少,尤其在不同类型支管对输水系统水锤影响方面还有待深入研究。为了研究叠压供水方式下不同管径支管对干管水锤影响,以某水利枢纽工程为例,结合水锤仿真模拟试验对不同工况条件下水锤进行分析。结果表明,当支管与干管管径比(简称支干管径比)大于1/6时支管对干管水锤影响较大,干管的水锤防护措施不再适用;而当支干管径比小于1/6时支管对干管水锤影响减弱,已有的措施能基本满足水锤防护要求。研究结果对于类似工程水锤防护及安全稳定运行具有重要的借鉴意义。     

Experimental investigation of natural convection from vertical and horizontal helicoidal pipes in HVAC applications

Natural convection from uniformly heated helicoidal pipes oriented vertically and horizontally is experimentally studied. Four helicoidal pipes of different parameters are presented. The effects of pitch to pipe diameter ratio, coil diameter to pipe diameter ratio and length to pipe diameter ratio on the average heat transfer coefficient are found. The experiments covered a range of Rayleigh number based on tube diameter from 1.5 × 10³ to 1.1 × 10⁵. The results showed that the overall average Nusselt number, Nu_m, increases with the increase in pitch to pipe diameter ratio, coil diameter to pipe diameter ratio and length to pipe diameter ratio for vertical helicoidal pipes. For horizontal helicoidal pipes, the overall average Nusselt number, Nu_m, increases with the increase in pitch to pipe diameter ratio and length to pipe diameter ratio, but it decreases with the increase in coil diameter to pipe diameter ratio. New correlations are presented, and they can be used in HVAC applications.     

用多重网格法研究多缸内燃机的进气特性

论述了用多重网格法研究多缸内燃机的进气瞬态过程。利用非线性方程全近似格式的多重网格法并结合特征线法对进气管内的气流运动进行了数值计算,直观地描述了多缸内燃机进气管各歧管内气体流动的瞬态过程,分析了转速、进气系统长度和管径等参数对进气特性的影响     

Study on local resistance of non-Newtonian power law fluid in elbow pipes

This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved90° bend pipe with circular cross-sections,which are widely used in industrial applications.By employing numerical simulation and theoretical analysis the properties of the flow and local resistance of power law fluid under different working conditions are obtained.To explore the change rule the experiment is carried out by changing the Reynolds number,the wall roughness and different diameter ratio of elbow pipe.The variation of the local resistance coefficient with the Reynolds number,the diameter ratio and the wall roughness is presented comprehensively in the paper.The results show that the local resistance force coefficient hardly changes with Reynolds number of the power law fluid;the wall roughness has a significant impact on the local resistance coefficient.As the pipe wall roughness increasing,the coefficient of local resistance force will increase.The main reason of the influence of the roughness on the local resistance coefficient is the increase of the eddy current region in the power law fluid flow,which increases the kinetic energy dissipation of the main flow.This paper provides theoretical and numerical methods to understand the local resistance property of non-Newtonian power law fluid in elbow pipes.     

Energy and thermal performance of heat pipe/cooling coil systems in hot‐humid climates

The objective of this study is to evaluate the magnitude of reduction in cooling and reheat energy when a heat pipe system is incorporated with the cooling coil of an air‐conditioning system. The heat pipe/cooling coil (HP/CC) system performance is determined by several parameters that are related to both the air‐conditioner cooling coil and the heat pipe physical characteristics as well as the condition of the air entering and leaving the system. In order to appreciate the impact of these parameters and their relative influence on energy consumption and the required indoor air conditions, a simple mathematical model incorporating the parameters of HP/CC is formulated. The model describes the overall system performance at varying entering and leaving air conditions. The model is then applied to a case study as an example of an application to investigate these relationships for a better understanding of the system behaviour and the influencing design parameters. It is evident that due to the coupling nature of the heat pipe and the cooling coil actions, a unique system performance will be obtained for each combination of heat pipe effectiveness and cooling coil by‐pass factor. A proper selection of both the heat pipe and the cooling coil characteristics is found to be necessary for a satisfactory performance under the given operating conditions. Copyright © 2000 John Wiley & Sons, Ltd.     

电控单体泵燃油系统仿真研究

采用Hydsim软件建立电控单体泵系统仿真模型,并通过试验数据进行模型标定。采用该模型仿真分析了电控单体泵系统关键结构参数对其性能的影响。仿真结果表明:喷孔总流通面积与最大喷射压力成反比,与最大喷油速率成正比;高压油管长度对喷射压力和喷油速率影响很小,仅影响喷油提前角;高压油管直径对最大喷油速率影响很小,与最大喷射压力成反比。     

Effect of cross-flow on the performance of air-cooled heat exchanger fans

In large-scale applications such as arrays of axial fans in air-cooled heat exchanger systems, edge–proximity and wind-induced cross-flow may decrease the flow through some fans by causing the flow to enter them at off-axis angles. In this study, such off-axis inflows were introduced by inserting inlet pipe sections between the plenum chamber of a standard test facility and one of three different scale model test fans of 1542 mm diameter. Fan power consumption turned out to be completely independent of off-axis inflow angle up to 45°. Fan total-to-total pressure rise was found to be independent of off-axis inflow angle, and the decrement in fan pressure rise was equal to the dynamic pressure based on the cross-flow velocity component at the fan inlet. Analysis showed that for model fans to represent the cross-flow behaviour of their prototypes, they should have the same ratio of dynamic pressure to pressure rise, and the same dimensionless characteristic slope at their operating points. The performance of a row of fans operating at off-axis inflow conditions representing a cooling system was well predicted by a simple model assuming that the fans farther from the edges induce cross-flows over the fans closer to the edges.