Drive train

Industrial Type-Gas Turbines. These vary in range from about 2.5MW-15MW. This type of turbine is used extensively in many petroehemieal plants for eompressor drive trains. The effieieneies of these units is in the low 30s. 

Besides the inherent lateral natural frequency characteristic, compressors are also influenced by torsional natural frequencies. All torsionally flexible drive trains are subject to non-steady or oscillatory excitation torques during normal operation of the system. These excitation torques can be an inherent function of either the driver or the driven equipment and, when superimposed on the normal operating torque, may appear to be of negligible concern. However, when combined with the high inertia loads of many turbomachinery trains and a torsional resonant frequency of the system, these diminutive ripples can result in a tidal wave of problems. 

Minimum drive-end peak torques, reducing drive train torsional stresses. 

The drive losses are generally based on the use of the V-helt drives, because the use of these types of drives is quite popular see losses from Figure 12-139. The mechanical losses in the drive train, must be considered separately, because they cannot be predicted by Fan Laws. 

Fan input power, P, is the sum of the power input to the impeller and the mechanical losses of the drive train ... 

Mixers should be mounted on a rigid base that assures level alignment and prevents lateral movement of the mixer and its drive-train. While most mixers can be bolted directly to a base, care must be taken to ensure that it is rigid and has the structural capacity to stabilize the mixer. 

Note that it is important for final drive-train alignment to compensate for actual operating conditions because machines often move after start up. Such movement is generally the result of wear, thermal growth, dynamic loads, and support or stmctural shifts. These factors must be considered and compensated for during the alignment process. 

Peak tension is the dominant factor that determines belt drive performance and service life. It should be noted that only the working tension components, Tp and Ts, have a direct impact on the pulley, shafts, and bearings of the drive train. Bending and centrifugal tension affects the belt, but should not transmit tension to the drive-train system. 

Like all drive components, proper alignment is crucial to the smooth operation of a chain drive. If the sprockets are not parallel and in the same plane, the chain will lose contact with the sprocket teeth and drive-train failure will occur. 

This module discusses two important drive-train components couplings and clutches. Each of these components is used to connect a driver (i.e., power source) shaft to the shaft of the driven unit. Such a connection allows torsional force to be converted into work in the driven unit. Keys and keyways, which are required to prevent slippage and to guarantee positive power with such connections, are also discussed. 

The primary advantage of this type of clutch is its ability to transmit full torsional force without any possibility of slip. Its major disadvantage is that the two shafts are instantaneously coupled when the clutch engages. This results in abrupt starts, which may cause excessive torsional shock loads that damage drive-train components. Figure 59.21 shows a positive clutch. 

In 1992, Volvo built an aluminum-bodied hybrid Environmental Concept Car (ECC) to California emission mandates. It had the recyclable plastic panels and water-based paints that are used by Volvo. A series hybrid drive train was used where a diesel gas turbine drives a generator to charge a battery pack to power an electric motor. The system is complex, but the car achieves good performance with low emissions and a 400-mile range. 

A combined comparative WTW analysis of specific global emissions and fuel supply costs is typically presented in a pathway portfolio analysis. Portfolio analysis helps to identify rapidly those alternative fuels and drive trains, or combinations of these, which can lead to the highest specific GHG emission savings. 

Besides fuel-cell (electric) vehicles (FCV), there are other vehicle concepts under development, which are also based on electric drives ranked by increasing battery involvement in the propulsion system, and thus extended battery driving range, these are hybrid-electric vehicles (HEV), plug-in hybrid-electric vehicles (PHEV) - which both incorporate an ICE - and, finally, pure battery-electric vehicles (BEV), without an ICE. While electric mobility in its broadest sense refers to all electric-drive vehicles, that is, vehicles with an electric-drive motor powered by batteries, a fuel cell, or a hybrid drive train, the focus in this chapter is on (primarily) battery-driven vehicles, i.e., BEV and PHEV, simply referred to as electric vehicles in the following. 

Conventional fuels and drive trains today show some system-inherent disadvantages in real operation, such as unfavourable fuel consumption at partial load (e.g., during urban driving) for ICE or limited driving range of electric vehicles... 

Table 8.1. Comparison of hydrogen and conventional drive trains...

Assuming a theoretical efficiency of the fuel-cell system of around 60% and an electric-drive-train efficiency of 90%, the overall fuel-cell system efficiency is about 55%. The theoretical efficiencies for a fuel cell cannot be realised in practice. The efficiency of the system (including fuel treatment, air supply and others) is already lower than that of the pure fuel-cell stack on its own the overall efficiency of the FC drive train falls to less than 40% as a result of additional components, such as compressors, control electronics and others, see Fig. 13.6. 

Figure 13.6. Efficiencies of automobile drive trains with combustion engines and fuel cells (DLR, 1997).

Even though the usual catalytic converter of the exhaust of the standard drive train is omitted, there are also net increases in the chemical industry. The increased demand is for the expensive coating of the electrode-membrane unit (MEA) and the catalysts needed for gas preparation (reformer). 

In standard internal combustion engine drive trains, about 60% of the added value results from the vehicle industry. This share may be reduced to only 10% for fuel-cell drive trains if the outsourcing potential is fully exploited. This shift is because the components of the fuel-cell propulsion system are not suited to current production structures in the automobile industry. Therefore, it can initially be assumed that they will be manufactured by other sectors. However, if there is a breakthrough of fuel cells, it is possible that the automobile industry will start to manufacture many of the components that are assigned to other sectors in Figure 13.13. 

Whereas the drive train of the standard combustion engine comprises many individual, diverse components, these are reduced in fuel-cell propulsion systems to a few expensive components. The decision on the production location of the important system components (i.e., fuel-cell stack, hydrogen storage, reformer and electric motor) will, therefore, be vital for the regional supplier structure. 

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