柴油机放热规律在数值计算中的应用

柴油机缸内燃烧过程的模拟是柴油机工作过程模拟的基础,燃料燃烧放热规律决定了缸内压力变化和能量转换的过程,进而影响整个燃烧过程。笔者以TBD234V12增压中冷柴油机为母型机,根据热力学第一定律,利用MATLAB语言编制了柴油机实测示功图反算放热率的程序,计算出燃烧放热率,以此作为已知数据进行工作过程计算,为柴油机工作过程和燃烧过程的研究提供了更为真实准确的燃烧放热规律。同时,利用三韦伯曲线来模拟缸内的放热规律,在达到同样柴油机综合性能指标条件下,分析二者的共同点与不同点。     

柴油机燃烧放热规律数值计算方法研究

本文根据热力学第一定律建立的柴油机燃烧过程能量平衡方程，并假设燃烧产物为相似的理想气体混合物，求得工质的平均定容比热，从而导出计算柴油机燃烧放热规律的数学模型。并给出了数值计算方法。通过实例计算表明，该计算方法简单明了，计算方便，能近似反映柴油机的燃烧放热规律。     

汽油机燃烧过程的能量可用性和不要逆性变化率分析

以热力学第一定律数值模拟和Ｗｉｅｂｅ单燃烧函数为基础，应用热力学第二定律分析一台汽油机燃烧过程的热机械能量可用性、化学能量可用性和不可逆性变化率。计算了在不同当量燃空比和残余废气系数时热机械能量可用性、化学能量可用性和不可逆性变化率的变化情况，说明了在汽油机浓混合气运行时，燃烧过程能量可用性、化学能量可用性和不可逆性变化率的变化情况，说明了在汽油机浓混合气运行时，燃烧过程能量可用性的计算应该包括化     

汽油机燃烧过程的能量可用性和不可逆性变化率分析

以热力学第一定律数值模拟和Ｗｉｅｂｅ单燃烧函数为基础，应用热力学第二定律分析一台汽油机燃 烧过程的热机械能量可用性、化学能量可用性和不可逆性变化率。计算了在不同当量燃空比和残余废气 系数时热机械能量可用性、化学能量可用性和不可逆性变化率的变化情况，说明了在汽油机浓混合气运 行时，燃烧过程能量可用性的计算应该包括化学能量可用性的影响。     

直喷式柴油机燃烧过程模拟与分析(一)

利用KIVA-Ⅱ程序模拟计算直喷式柴油机燃用柴油时缸内的燃烧过程，如混合气形成过程、缸内温度场、主要有害物质NOx的生成浓度分布等。通过对直喷式柴油机燃用柴油时燃烧过程的模拟计算与分析，对模拟燃用绿色能源-二甲醚的燃烧过程提出了一些建议。     

直喷式柴油机燃烧过程模拟与分析(二)

利用IIVA-Ⅱ程序模拟计算直喷式柴油机燃用柴油时缸内的燃烧过程，如混合气形成过程、缸内温度场、主要有害物质NOx的生成浓度分布等。通过对直喷式柴油机燃用柴油时燃烧过程的模拟计算与分析，对模拟燃用绿色能源-二甲醚的燃烧过程提出了一些建议。     

柴油机燃料放热规律数值计算方法研究

本文根据热力学第一定律建立的柴油机燃料过程能量平衡方程，并假设燃料产物为相似的气体混合物，求得工质的平均定容比热，比侧导出计算柴油机燃料放热规律的数学模型。并给出了数值计算方法。通过实例计算表明，该计算的方法简单明了，计算方便，能近似反映柴油机的燃料放热规律。     

不同喷油提前角对缸内碳烟生成影响的计算与分析

应用计算流体动力学对某小型高速增压直喷式柴油机缸内燃烧过程进行了数值计算,得出了不同喷油提前角下增压直喷式柴油机缸内混合气、温度和碳烟的分布情况,分析了不同喷油提前角下,上止点前后的喷油量的比例对碳烟排放的影响,并通过实际工况下的碳烟排放试验进行了验证。为增压柴油机性能与排放优化提供了参考。     

直喷式柴油机排放的机内控制研究

不同的油气混合和缸内燃烧过程的组织．对直喷式柴油机污染物的排放有较明显的影响,从而找到了降低直喷式柴油机排放的方法．     

直喷式柴油机燃烧压力振荡特性及其对燃烧噪声影响的研究

本文报告了对直喷式柴油机燃烧压力振荡特性及压力振荡对燃烧噪声影响规律的研究，并从理论与试验上研究了燃烧压力振荡的多模态特性及多模态的叠加特性。研究结果表明，通过减小缸内压力振荡可降低直喷式柴油机的燃烧噪声。     

Study of a Stirling engine used for domestic micro‐cogeneration. Thermodynamic analysis and experiment

One of the aims of this work is the study of the geometry of a micro‐cogenerator using a Stirling engine with four double effect pistons. The complex geometry of the heat exchangers was determined by optical measurements. Results of three thermodynamic models: Direct Method from Finite Speed Thermodynamics (FST), isothermal model (Schmidt), and adiabatic model (Finkelstein) are confronted to experimental ones. Direct Method consists of the study and the evaluation of the irreversibilities of thermal machines by analyzing the cycle, step by step, and directly integrating the equation of the First Law for processes with finite speed combined with Second Law of Thermodynamics, for each process of the cycle. The expression of efficiency and power, depending on the speed of the processes and geometric and functional parameters, is then obtained in a straightforward manner. The isothermal and adiabatic models are based on the division of Stirling engine in 3, respectively 5 control volumes, for which the ideal gas law and the equations of mass and energy balance are applied. Analysis of the process of heat transfer and flow of the working gas, taking place in the Stirling engine, is carried out taking into account instantaneous representation of the working fluid volume in the engine. A system of differential equations is solved by iteration using Matlab/Simulink software. The theoretical results are compared to experimental ones. This comparison allows to point out a good accuracy of the Direct Method and the Adiabatic Model, for the thermal operating parameters of the system, noting the different assumptions of each analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Availability analysis of a turbocharged diesel engine operating under transient load conditions

A computer analysis is developed for studying the energy and availability performance of a turbocharged diesel engine, operating under transient load conditions. The model incorporates many novel features for the simulation of transient operation, such as detailed analysis of mechanical friction, separate consideration for the processes of each cylinder during a cycle (“multi-cylinder” model) and mathematical modeling of the fuel pump. This model has been validated against experimental data taken from a turbocharged diesel engine, located at the authors’ laboratory and operated under transient conditions. The availability terms for the diesel engine and its subsystems are analyzed, i.e. cylinder for both the open and closed parts of the cycle, inlet and exhaust manifolds, turbocharger and aftercooler. The present analysis reveals, via multiple diagrams, how the availability properties of the diesel engine and its subsystems develop during the evolution of the engine cycles, assessing the importance of each property. In particular the irreversibilities term, which is absent from any analysis based solely on the first-law of thermodynamics, is given in detail as regards transient response as well as the rate and cumulative terms during a cycle, revealing the magnitude of contribution of all the subsystems to the total availability destruction.     

电辅助涡轮增压器对柴油机热效率调控规律的研究

针对一台配备有电辅助涡轮增压器(electrically assisted turbocharger,eTurbo)的6.7L柴油机,建立并试验校准了其GT-SUITE/Simulink联合仿真平台。通过调节eTurbo的电功率,在保持发动机动力性不变的前提下,改变发动机的运行状态,以获得发动机系统的电能平衡和最大热效率。基于该平台,首先在稳态工况下,研究了eTurbo的电功率与发动机热效率之间的相互影响关系,并在全工况内量化评估了发动机等效热效率的改善潜力。其次开展了US06城市工况及FTP-75市郊驾驶循环工况下的仿真分析,循环平均结果显示:随电辅助能量的增加,发动机热效率提高但回收的电能不断减小;在FTP-75循环下,要实现发动机节油就必须使用额外的发电手段,比如回收整车刹车能量;与FTP-75循环相比,US06循环发动机负荷更高,故可回收更多的电能,电能可以实现自平衡。     

燃用小桐子油柴油机怠速工况工作过程及循环波动

采用柴油、柴油-小桐子掺混油、小桐子油、高温小桐子油,在单缸水冷四冲程柴油机上进行了怠速工况试验,测录了多循环的瞬时气缸压力与高压油管燃油压力,对比分析了喷油与燃烧过程中各参数的循环波动。结果发现,怠速工况喷油过程中,喷油持续期的循环波动最明显,小桐子油的喷油始点滞后,喷油持续期长,喷油压力大,喷油过程的循环波动略大;怠速工况燃烧过程中,最大燃烧压力升高率和滞燃期的循环波动率最为明显,小桐子油滞燃期略短,燃烧压力升高率小,最高燃烧压力低,滞燃期和最大燃烧压力升高率的循环波动明显大于柴油;燃用小桐子油增大了原机的循环波动,怠速运转不如柴油稳定。     

Performance and emissions characteristics of a hydrogen enriched LPG internal combustion engine at 1400 rpm

Environmental concerns and depletion in petroleum resources have forced researchers to concentrate on finding renewable alternatives to conventional petroleum fuels. Hydrogen is thought to be a major energy resource of the future due to its clean burning nature and eventual availability from renewable sources. Hydrogen is widely regarded as a promising transportation fuel because it is clean and renewable.The authors manufactured a high accuracy heavy-duty variable compression ratio single cylinder engine to investigate its performance and emissions characteristics. The test engine was run at 1400 rpm with a compression ratio of 8. Spark timing was set to MBT (minimum spark advance for best torque). This paper investigates the effects of hydrogen enriched LPG fueled engine on exhaust emission, thermal efficiency and performance.     

Comparative first- and second-law parametric study of transient diesel engine operation

A computer model is developed for studying the first- and second-law (availability) balances of a turbocharged diesel engine, operating under transient load conditions. Special attention is paid to the direct comparison between the results from the two laws, for various operating parameters of the engine. The model simulates the transient operation on a degree crank angle basis, using a detailed analysis of mechanical friction, a separate consideration for the processes of each cylinder during a cycle (“multi-cylinder” model) and a mathematical model of the fuel pump. Experimental data taken from a marine duty, turbocharged diesel engine, located at the authors’ laboratory, are used for the evaluation of the model's predictive capabilities. The first-law (e.g., engine speed, fuel pump rack position, engine load, etc.) and second-law (e.g., irreversibilities, heat loss and exhaust gases) terms for the diesel engine cylinder are both computed and depicted in comparison, using detailed diagrams, for various engine operating parameters. It is revealed that, at least for the specific engine type and operation, a thermodynamic, dynamic or design parameter can have a conflicting impact on the engine transient response as regards energy and availability properties, implying that both a first- and second-law optimization is needed for best performance evaluation.     

LPG点燃式发动机冷起动首循环进气富氧试验研究

基于循环控制,详细研究了LPG点燃式发动机冷起动首循环进气富氧的燃烧及排放特性。试验在一台电控LPG进气喷射单缸风冷四冲程125 mL发动机上进行,采用膜式富氧方法实现富氧进气燃烧。研究表明:当过量空气系数大于0．7时,富氧进气燃烧缸压峰值与空气相比增加不显著,此后随混合气加浓,富氧进气燃烧缸压峰值开始明显大于常规空气进气燃烧;过量空气系数在0．4～0．876时,富氧进气燃烧与常规空气进气燃烧相比,HC排放没有较大降低,在此范围之外,富氧显著降低HC排放;过量空气系数在0．4～0．7,富氧与空气相比CO显著降低;富氧进气燃烧,使得首循环NO排放大幅增加;计算放热率发现,富氧燃烧速度比常规空气进气燃烧更快,放热更集中。     

Performance analysis of a heavy duty combined cycle power plant burning various syngas fuels

This paper presents a performance analysis of state of the art combined cycles power plants burning a number of syngas fuels. The first part of the analysis focuses on the effect of gas composition on the rated performance of the plant drawing two main conclusions. First, higher pressure ratio and lower firing temperature are found at turbine inlet. Second, the pressure at which fuel is supplied to the gas turbine plays an essential role in the power capacity of the engine. With respect to the steam cycle, no major effects are appreciated except for very low LHV fuels. In the second part of the work, the annual performance of the engine subjected to a typical load profile and real ambient and market conditions is studied. Differences in total incomes are appreciated depending on fuel composition and the concern about carbon emissions is highlighted.     

Generation of combustion irreversibilities in a spark ignition engine under biogas–hydrogen mixtures fueling

Availability analysis is applied to the cylinder of a spark ignition engine during the closed part of the engine cycle when biogas–hydrogen blends, with volumetric fractions of hydrogen up to 15%, are used as fuel. The focal point is on the demonstration of the spatial distribution inside the burned gas of the combustion-generated irreversibilities for the various hydrogen concentration cases examined, which constitute one of the major sources for the defective exploitation of fuel into useful mechanical work that cannot be identified by the traditional first-law analysis. For this reason, an experimentally validated closed cycle simulation code is used, based on a multi-zone thermodynamic model of the cylinder content, applied in conjunction with a quasi-dimensional combustion model for burn rate predictions. After presenting global availability-balance-related results, pointing out the increase in the second-law efficiency of engine operation with the hydrogen enrichment of biogas, detailed information is provided regarding the spatial development of the combustion irreversibilities throughout the thermodynamically inhomogeneous burned gas, along with their link with the developed temperature field, as determined during combustion at each hydrogen fraction. It is revealed that the addition of increasing amounts of hydrogen in biogas promotes the degree of reversibility of the burning process mainly during the combustion of the later burning gas, due to the incurred increase in its combustion temperatures. On the contrary, the contribution of the early burning gas to the decrease in combustion irreversibilities with hydrogen addition seems to be less prominent.