Automotive operational modes

In this section we will discuss an example of recent laboratory work on the impact of sulfur on palladium catalysts formulations compared to other noble metal formulations. The laboratory studies discussed here have been performed using an apparatus which simulates the exhaust gas generated from a vehicle under several operating modes. The simulated exhaust gas is then heated to a controlled level and directed to a sample core taken from a commercial automotive converter. Quantitative analysis of pollutant and other gas species (CO, HC, NOx, COj and Oj) is performed using gas bench analyzers prior to and following the catalyst sample to determine the conversion efficiency for HC, CO and NOx. 

In the case of Ni-MH batteries, which can be cycled about 5000 times their nominal capacity at 80% DoD and more than 15,000 times their nominal capacity with shallow cycling [55,56,60-63], may be an appropriate choice. In the future, lithium-ion batteries may also enter the automotive market. Their high specific energy, which exceeds that of lead-acid systems by about a factor of three at medium discharge rates, would allow air-conditioning to be operated even in the engine-off mode. The calendar-life of lithium-ion batteries under automotive operating conditions, however, still needs to be improved, and there must be a reduction in cost to an acceptable level for such batteries. 

Lead—acid batteries are used in three main applications automotive (starting, lighting and ignition, SLI), for motive power and for standby (reserve) power. A fourth type of lead—acid batteries is trying to gain a market segment, too, i.e. batteries for hybrid eleetric vehicle applications. In view of the partieular battery funetion and the speeifieity of the operation mode in the above four applications, the amounts of the three expander eomponents should differ for the different battery types, depending on their effeet on the proeesses that oeeur in the battery. Boden [39] proposes typical expander formulations for the different battery applications as summarised in Table 7.3. 

In this section, the operational modes that fuel cell stacks are subjected to the 2015 performance, cost, and durability targets that fuel cell technology must achieve and recent advancements made by automotive companies toward achieving the targets for commercialization are discussed. 

The biggest difference between automotive and stationary fuel cell systems is in the electric subsystem—power conditioning. The architecture of the power conditioning system greatly depends on the system operating mode, as discussed in the section 9.4. Electrical Subsystem. An automotive system is practically a stand-alone system, a stationary fuel cell power system may operate as stand-alone, grid parallel, grid interactive, or as backup power. 

Three-way catalysts are used in most 1981 gasoline-fueled automobiles to lower the levels of NO, CO, and hydrocarbons in engine exhaust. These catalysts normally operate under dynamic conditions catalyst temperature increases rapidly after the engine starts (during catalyst "warmup"), and exhaust flowrate and composition fluctuate under most modes of operation. The warmup of automotive catalysts is reasonably well understood (1). The operation of three-way catalysts in the dynamic exhaust environment after warmup is complex and less well understood. 

Figure 99. Amount and composition of particulates in the exhaust gas of a heavy duty DI diesel engine at various engine operation conditions in the AVL-8-mode engine test cycle. Reprinted with permission from ref [68], 1991 Society of Automotive Engineers, Inc.

While the chemical kinetics of the thermal autoignition process are relatively well understood, means of controlling the ignition timing in the engine cycle when operating in the HCCI mode are still elusive. Chemists and chemical engineers will need to help overcome this obstacle if HCCI is to be executable in automotive practice. 

Within the last few decades the automobile industry has undergone a revolution in overall vehicle reliability. With the large number of components and the number of potential failure modes, it has become necessary for a component to provide six-sigma (99.9999%) reliabiUty over its operational life (now assumed to be ten years or 240,000 km/150,000 miles), in order to satisfy customer expectations. Current production automotive batteries do not perform to this standard of course, but it is expected that pressure will come to bear on the industry to perform to this level in years to come. In some respect this may be achievable experience with the first generation Ni-MH traction battery cells in severe electric vehicle (EV) usage has demonstrated less than 25 ppm failures after three years of serviee [2]. In order to achieve this level of performance, however, a close partnership is essential between vehicle sub-systems as the life of the battery is intrinsically entwined with the engine, climate control, and battery charge systems. 

Three-way automotive catalysts never operate under steady-state conditions catalyst temperature increases rapidly after engine starting, and the exhaust flow rate and composition fluctuate rapidly under all modes of operation. Numerous studies have shown that the performance of catalysts under dynamic conditions differs greatly from their performance under steady-state conditions (e.g., ref.1-4). Thus, it is manditory to evaluate and compare the performance of three-way catalysts on the basis of tests that involve dynamic conditions. 

Since their introduction to production vehicles in 1975, a great deal of research has been undertaken to try to understand the reactions occuring over, and the mode of operation of, tliree-way automotive exliaust catalysts [1-3]. Since, under real conditions, these catalysts never operate under steady-state conditions [4] one of the best ways to study the operation of these catalysts has been to use a system similar to that designed by Schlatter et al. [5,6], which facilitates the study of tliree-way responses to transient changes in gas composition. 

When used for automotive applications, fuel cells must respond to changes in the load. Changing the load alters the water production, changing the balance between water produced and water removed, resulting in a change of the membrane water content. The effect of the load resistance on the water activity can be seen in the polarization curves for the STR PEM fuel cell shown in Figure 3.9A [23]. The STR PEM fuel cell was operated in the autohumidification mode. The STR PEM fuel cell was equilibrated at 80C for 12 h with a fixed load resistance (either 0.2 or 20 fi). After equilibration, the polarization curve was obtained by sweeping the load resistance between 0.2 and 20 ft in 100 s. The relative humidity in the anode and cathode streams... 

Unlike residential and stationary fuel cells, automotive PEMFCs undergo the entire slew of aggressive variable loads and environmental conditions that are typically experienced by conventional ICEs. The modes of operation of an... 

A detailed application of the RAPP method based on the theoretical steps is explained within the automotive case study electric actuator in chapter 5. The main goal of step A is the detection of the failure mode related to the product life span variables and the statistical mapping and prognosis of the Failure Mode (EM). Base of operations is data out of the technical analysis of damaged components and field data (e.g. guarantee/goodwill database). 

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