直接甲醇燃料电池在汽车上的应用前景分析

介绍了直接甲醇燃料电池的结构、工作原理和特性,对影响其应用于汽车的两个主要因素———燃料转换效率和功率密度进行了详细地分析,对目前面临的主要技术难题和解决方法进行了阐述,如催化剂和甲醇渗透等,最后得出了一些相应的结论。     

Study of performance improvement in a direct methanol fuel cell

The direct methanol type system consists of simple and compact equipment, and is suited for automobile use. However this system possesses low power density and its internal resistance needs to be reduced. This research investigated characteristics of power output and thermal efficiency in a proton-exchange-membrane fuel cell directly fuelled with methanol solution. Some influences of catalyst amount and separator groove design on power output were also found.     

Cooling effect of methanol on an n-heptane HCCI engine using a dual fuel system

Homogeneous charge compression ignition (HCCI) engines have the potential to raise the efficiency of reciprocating engines during partial load operation. However, the performance of the HCCI engine at high loads is restricted by severe knocking, which can be observed by the excessive pressure rise rate. This is due to the rapid combustion process occurring inside the cylinder, which does not follow the flame propagation that is seen in conventional engines. In this study, a low compression ratio of 9.5:1 for a gasoline engine was converted to operate in HCCI mode with the goal being to expand the stable operating region at high loads. Initially, pure n-heptane was used as the fuel at equivalence ratios of 0.30 to 0.58 with elevated intake charge temperatures of 180 and 90 °C, respectively. The n-heptane HCCI engine could reach a maximum performance at an indicated mean effective pressure (IMEP) of 0.38 MPa, which was larger than the performance found in the literature. To reach an even higher performance, a dual-fuel system was exploited. Methanol, as an anti-detonant additive, was introduced into the intake stream with various amounts of n-heptane at fixed equivalence ratios in the range of 0.42 to 0.52. It was found that the methanol addition cooled the mixture down prior to combustion and resulted in an increased coefficient of variation (COV). In order to maintain stable combustion and keep the pressure rise rate below the limit, the intake charge temperature should be increased. Introduction of 90% and 95% (vol/vol) hydrous methanol showed a similar trend but a lower thermal conversion efficiency and IMEP value. Therefore, a dual fuel HCCI engine could maintain a high thermal conversion efficiency across a wide load and enhance a 5% larger load compared to a pure n-heptane-fuelled HCCI engine. The hydrocarbon (HC) and carbon monoxide (CO) emissions were lower than 800 ppm and 0.10%, respectively. They were less at higher loads. The nitrogen oxides (NO _x ) emissions were below 12 ppm and were found to increase sharply at higher loads to a maximum of 23 ppm.     

Performance of a methanol reforming system for a fuel cell powered vehicle and system evaluation of a PEFC system

The fuel cell is an environmentally-friendly power source due to high efficiency and cleanness. Considering safety, tractability and infrastructure, a methanol reformer is a candidate for the supply of hydrogen to fuel cell vehicles. However as CO generated by methanol reformers poisons the platinum catalysts of anodes, the operating conditions were studied in order to minimize the CO emissions from the reforming system. This study tested a methanol reforming system including a steam reformer and preferential oxidizer, established the chemical reaction rates of reforming and CO oxidation and calculated the dynamic changes in CO concentration from the reformer using a newly developed simulator.     

Numerical study to evaluate the characteristics Of HVAC-related Parameters to reduce CO<Subscript>2</Subscript> concentrations in cars

Today, as people are spending increasing amounts of time in their cars, they have come to recognize that the car should function as a “residential” space. An eco-friendly indoor environment that provides comfort in terms of visual, tactile, and auditory senses is needed for the driver and the passengers. The quality of the car’s indoor environment was evaluated on various factors, such as indoor thermal comfort, indoor air quality, smell, and noise. For the indoor air quality, the typical pollutants that degrade the air quality are CO₂, volatile organic compounds, and exhaust gases. Especially, CO₂ has a direct relationship with drowsy driving which leads to traffic accidents. There have been many experimental and analytical studies to reduce the level of CO₂ in a short time, but analyses of parameters that affect indoor CO₂ concentration are insufficient and comprehensive standards for evaluating the car indoor CO₂ concentration do not yet exist. In this study, several parameters were selected that can influence the reduction rate of CO₂ concentration, and a series of computational analyses were conducted to study the results of these parameters in CO₂ reduction. Based on this study, a prediction equation for CO₂ concentration was derived. For this, a general full factorial design was used to evaluate the CO₂ reduction characteristic based on various parameters (ventilation mode, boarding condition, vent angle, mass flow rate, and operation mode), and then their effects were analyzed to obtain an evaluation database of indoor air quality. From that, a prediction equation was derived to estimate the indoor air quality, enabling us to evaluate the CO₂ concentration quickly that actually influences the human body without carrying out time-consuming CFD analyses for CO₂ concentration. This study will be useful in designing HVAC systems and establishing the control logic for effective improvement of the car’s indoor air quality in the future.     

掺烧比对P50/甲醇双燃料发动机燃烧与排放的影响

燃料富氧重整和双燃料燃烧模式是改善燃烧过程和降低颗粒物排放的重要方法.在一台四缸增压中冷的高压共轨柴油机上,采用进气道喷射甲醇、缸内喷射P50(50％体积比例柴油与50％体积比例PODE)的双燃料模式,研究掺混比对P50/甲醇双燃料发动机燃烧与排放特性的影响.研究结果表明:相比于纯柴油模式,P50及P50/甲醇双燃料燃...     

Study of n-C<Subscript>12</Subscript>H<Subscript>26</Subscript> reforming over DFC catalyst in a simulated diesel exhaust

In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen, requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation (CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5–10% oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C₁₂H₂₆ was used as the feedstock for the reforming reaction. In the CPOx of n-C₁₂H₂₆, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than unity in the absence of water vapor. However, as the water concentration was increased to 2.5 and 5.0 vol. % in the n-C₁₂H₂₆ CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively. This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects, hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx reaction of n-C₁₂H₂₆ can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation.     

The critical hitch angle for jackknife avoidance during slow backing up of vehicle–trailer systems

We set out to answer the question: At what hitch angle does it become impossible for a vehicle and trailer to continue to backing up without getting into a jackknife? Jackknifing during backing up of trailers occurs when the hitch angle increases to a point such that the vehicle and trailer fold together about the hitch point like a jackknife. If the backward motion is continued, the jackknife effect progressively worsens, until the vehicle and trailer are in physical contact with each other. Jackknifing can result in traffic disruptions and wasted time, and can potentially cause damage or personal injury. Our goal is to analytically determine the ‘critical hitch angle’ (θ_cr), the hitch angle threshold beyond which a continued reverse motion causes an inescapable jackknifing. In this paper, we provide a formal definition of θ_cr for slow backing up of vehicle–trailer systems on a level solid surface, beyond which the vehicle must stop backing up and revert to forward motion in order to escape from jackknifing. The critical hitch angle is sub-categorised into Absolute (θ_cr, a) and Directional (θ_cr, d) critical hitch angles depending on the operating constraints and vehicle steering objectives. One solution for θ_cr is posed as a numerical solution to the steady-state conditions of the dynamic equations. The effects of such hitch angle limitations are demonstrated through simulation. Also, a warning system making use of the θ_cr is proposed. Such warning systems can assist drivers in avoiding jackknifing while backing up a vehicle–trailer system.     

Effect of direct in-cylinder CO2 injection on HCCI combustion and emission characteristics

Fuel injection during negative valve overlap period was used to realize diesel homogeneous charge compression ignition (HCCI) combustion. In order to control the combustion, CO₂ in-cylinder injection was used to simulate external EGR. Effects of CO₂ injection parameters (injection timing, quantity, pressure) on HCCI combustion and emission characteristics were investigated. Experimental results revealed that CO₂ in-cylinder injection can control the start of combustion and effectively reduce NO_x emission. Either advancing CO₂ injection timing or increasing CO₂ injection quantity can reduce peak cylinder pressure and mean gas temperature, delay the starts of low temperature reaction (LTR) and high temperature reaction (HTR), and lower pressure rise rate; NO_x emission was reduced, while smoke, HC, and CO emissions increased. Since the combustion phase was improved, the indicated thermal efficiency was also improved. Injection pressure determines the amount of disturbance introduced into the cylinder. Generally, with the same injection quantity, higher injection pressure results in higher momentum flux and total momentum. Larger momentum flux and momentum has a stronger disturbance to air-fuel mixture, resulting in a more homogeneous mixture; therefore, larger injection pressure leads to lower NO_x and smoke emissions.     

甲醇汽车甲醛排放测试方法

甲醛具有致癌性,可对人体健康造成危害,因此甲醇汽车的甲醛排放检测方法受到了人们的关注。文章利用常规排放的检测方法取得汽车尾气的稀释样气,从中抽取一定量的排气样气,由高效液相色谱仪分析甲醛的质量浓度。根据试验时测定的体积及试验循环行驶距离,得出与常规排放量纲完全一致的甲醛排放量。解决了甲醇汽车尾气排放中甲醛体积分数的测试问题。     

Investigation of soot formation in Diesel-GTL fuel blends under quiescent conditions

In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O₂ concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixing-controlled combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O₂ concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O₂ concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the formation of soot and NOx within a wide range of diesel engine loads.     

Development of active front wheel steering control system keeping stable region in driving phase diagram

This paper presents a new active steering control system based on driving phase diagram (β _fr ?δ _f diagram). In order to make state variables to follow those of nominal vehicle model that was developed under no consideration of disturbance, Quadratic Programming Problem (QPP) is formulated, where time varying objective function minimizes the differences between nominal and actual parameters. The steering characteristic in active steering control system changes when the vehicle faces disturbance such as crosswind and flat tire, and driver tries to counteract it after recognizing the change. The proposed method defines a stability region on β _fr ?δ _f diagram. In order to make β _fr and δ _f remain in the stability region, a new model predictive controller is proposed. While conventional controllers are restrictive to satisfy the β _fr ?δ _f diagram based stability condition, the proposed controller ensures solution space and also plays a direct role to minimize the evaluation function in the constrained optimal control problem.     

Air flow trajectory and surge avoidance of centrifugal compressor under variable pressure operation of automotive fuel cells

The compressor of an automotive proton exchange membrane fuel cell requires severe dynamic performance under normal driving patterns. Because the air flow demand of the automotive fuel cell requires steep increase/decrease, it is very important to understand the air flow trajectory of the centrifugal compressor to avoid the compressor surge. In this study, a simulation model of an automotive fuel cell system with a dynamic compressor was developed to investigate the proper trajectory of air flow rate on a performance map of an air compressor. The dynamic response of the compressor shows that the cathode inlet and exit valves have a significant effect on surge evolution. In particular, the results showed that a proper combination of valve opening areas is required to avoid compressor surge. In this study, the original two valve approach was reduced to a single cathode exit valve control with fixed cathode inlet orifice. A surge rejection algorithm was also developed, based on the comparison of surge protection envelope pressure with actual measured pressure. The results show that surge evolution is effectively avoided by controlling the cathode exit valve.     

硅胶吸附管采集甲醇汽车尾气排放中甲醇的方法研究

文章主要研究了利用硅胶吸附管采集甲醇汽车尾气排放中甲醇的方法,对硅胶吸附管的规格、待测样品的浓度、采样参数等进行了详细的讨论及验证。研究表明,利用硅胶吸附管采集甲醇的过程中,很容易发生甲醇的穿透。随着硅胶颗粒装填数目的增加,甲醇的穿透率降低,实际吸附甲醇的效率增加。在采样流量相同时,待测样品浓度越高,甲醇的穿透率越高。在待测样品浓度相同时,采集流量越高,甲醇的穿透率越高。将硅胶吸附管串联,可以有效减少甲醇的穿透,提高吸附效率。     

Deterioration in fuel cell performance resulting from hydrogen fuel containing impurities: poisoning effects by CO,CH4, HCHO and HCOOH

This paper covers our investigation into a decline in fuel cell (FC) performance resulting from hydrogen fuel containing impurities. This is a serious problem in case of adopting the methanol or gasoline reforming approach as a means of supplying fuel to FCs. The results are summarized as follows:(1) Components of the gas generated by the reformer adopting the steam reforming and auto thermal reforming approach were predicted and specific components and concentrations were identified;(2) Various experiments and analyses were conducted to determine the adverse effect of CO, CH₄, HCHO and HCOOH poisoning on the performance of FC.     

Coûts d’opportunité de construction des infrastructures routières et ferroviaires en Aquitaine pour la période 2007–2013 sous contrainte du Plan climat régional

The French Aquitaine region has implemented a climate plan to avoid 2,883 ktCO₂eq for 2007–2013. Although this region reduced its greenhouse gas (GHG) emissions by 1,119 ktCO₂eq between 1990 and 2005 (from 24,061 ktCO₂eq to 22,942 ktCO₂eq), GHG emissions of transports sector has increased by 762 ktCO₂eq. During the climate plan period, the region will implement projects of road and rail infrastructures construction in order to absorb the foreseen increase of traffic. These projects will contribute to economic development, but they also will provoke additional GHG emissions. But, the existence of a climate plan requires offsetting these GHG emissions. A maximum amount of budget will be determined in order to implement some projects to offset GHG emissions from road and rail projects. This budget will be equal to opportunity costs of road and rail projects. Input-output analysis will be used to carry out these calculations. Its interest is to incorporate the complexity of interindustrial trade with a detailed sectored study.     

Multi-objective control of a full-car model using linear-matrix-inequalities and fixed-order optimisation

This paper studies multi-objective control of a full-vehicle suspension excited by random road disturbances. The control problem is first formulated as a mixed ?₂/?_∞ synthesis problem and an output-feedback solution is obtained by using linear-matrix-inequalities. Next, the multi-objective control problem is re-formulated as a non-convex and non-smooth optimisation problem with controller order restricted to be less than the vehicle model order. For a range of orders, controllers are synthesised by using the HIFOO toolbox. The efficacy of the presented procedures are demonstrated by several design examples.     

Measurement of soot oxidation with No<Subscript>2</Subscript>-O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO₂-O₂-H₂O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO₂-O₂ oxidation, which was 60±3 kJ/mol. When NO₂ exists with O₂ and H₂O, the reaction rate increases in proportion to NO₂. It increases nonlinearly with O₂ or H₂O concentration when the other two oxidants are fixed.     

An H2 Formulation for the Design of a Passive Vibration-Isolation System for Cars

SUMMARY

Optimal design of an active suspension system for road vehicles can be solved using LQR techniques. Such a problem is equivalent, in the frequency domain, to determine the state feedback gain matrix that minimizes the H₂ norm of a suitable transfer matrix.

A passive suspension system can be seen as the physical realization of a suitable state feedback law whose gains are function of the system parameters. This law, and thus the characteristic elements of the passive suspension, can be determined as an approximation of the H₂ optimal solution. This methodology allows one to choose the best controller from a constrained subset (i.e., all possible passive suspensions of a particular form) of all possible controllers.     

Reliability of Nanofluid Concentration on the Heat Transfer Augmentation in Engine Radiator

Nanofluids, the fluid suspensions of nanomaterial, became a promising fluid that is invoked when heat transfer increase is required. Using of nanofluids as a coolant in the engine radiators is a crucial topic for the thermal engines manufactrers due to the expected enhancement in the cooling process. In this study, Two nanofluids (Al₂O₃/water and CuO/water) flowing in a flat tube of radiator are investigated numerically to evaluate thermal and flow performance. The resizing process for the radiator is performed by using nanofluid instead of water flow. A significant reduction in the radiator volume is achieved due to marked improvement in the heat transfer performance while, the required pumping power after this reduction in the volume is increased over that needed for base fluid. The normalized heat transfer (heat transfer to the pumping power) is found to be a function of both Reynolds number and nanofluid concentration ratio while the ratio of the normalized heat transfer is found to be dependent only on the nanofluid concentration ratio. These dependencies are formulated as general correlations.