Diesel engines medium-speed

Table 15.4 shows typical applications for the range of oil fuels for use with major prime movers. Medium/high-speed diesel engines generally use distillate fuel oils while medium/low-speed units generally bum residual fuels. The gas turbine, which normally operates on liquid distillate fuels, is capable of running on residual fuels, although examples of these are normally associated with crude production facilities. 

The diesel engine, being a reciprocating machine, is mechanically complex, and in arduous environments its wear rate can be high. Major overhauls on high-speed engines are usually stipulated at 15,000 running hours, which extends to 20,000 and 30,000 on medium- and low-speed machines, respectively. 

Winter grade diesel fuel oil is recommended for use in ambient temperature environments as low as -25.6°F (-32°C). It is intended for use in high-speed automotive-type diesel engines and nonaircraft-type turbine engines. This fuel may be used for medium-speed stationary engine applications. 

Regular grade diesel fuel oil is recommended for use in temperate ambient temperature environments. It is recommended for use in all automotive high-speed and medium-speed engine applications and nonaircraft turbine engines. 

Fuels used in marine applications are quite diverse in their properties. Low-viscosity distillate fuels and high-viscosity residual fuels can both be considered marine fuels. The applications, though, would differ and could include use in direct injected diesel engines, boilers, and gas turbines. Also, high-speed, medium-speed, and slow-speed engines can be found in marine applications. 

Marine diesel oil (MDO) Grades DMB and DMC Grade DMB is blended from gas oils and a trace amount of residual oil. It has a minimum cetane number of 35 and a maximum viscosity of 11 cSt 104°F (40°C). Grade DMC is blended from gas oil components and up to 10% residual oil. It has a minimum cetane number of 35 and a maximum viscosity of 14 cSt 104°F (40°C). Marine diesel oil is used in both high-speed and medium-speed engines. 

The medium-speed diesel (railroad locomotive, marine engines) appears to be another potential application for SRC-II coal liquids to displace petroleum fuels. Other applications being studied by potential users include the automotive turbine, reheat furnace fuel in the steel industry and reformer feedstock for fuel cells. All in all, the products to be derived from coal liquefaction processes like SRC-II can, over time, displace a portion of our requirements for imported petroleum in a variety of end uses. 

Figure 106. Conversion of carbon monoxide, gaseous hydrocarbons and sulfur dioxide reached over diesel oxidation catalysts as a function of the preeious metal formulation at equimolar loading (monolith catalyst with 62 cells cm - dedicated diesel washeoat formulations with platinum, palladium and rhodium at an equimolar loading of 8 mmol I, fresh model gas test at a gas temperature at catalyst inlet of 723 K a space velocity 50000Nil h model gas simulates the exhaust gas composition of an IDl passenger car diesel engine at medium load and speed and contains 100 vol. ppm SO2). Reprinted with permission from ref. [68], C 1991 Society of Automotive Engineers, Inc.

Figure 109. Conversion of carbon monoxide and gaseous hydrocarbons reached over a diesel oxidation catalyst at various settings of the exhaust gas temperature, for a model gas composition with and without SO2 (monolith catalyst with 62cells cm dedicated diesel washcoat formulations with platinum loading of 1.76gl" in the fresh state model gas light-off test at a space velocity of 50000Nir h model gas simulates the exhaust gas composition of an IDI passenger car diesel engine at medium load and speed).

Figure 116. Conversion of nitrogen oxides reached over a NO. reduction catalyst at three different settings of the exhaust gas temperature, as a function of the concentration of the nitrogen oxides in the exhaust gas (light-off test in a model gas reactor at a space velocity of 50000 Ml T h". Model gas composition based upon the composition of the exhaust gas of an IDI/NA passenger car diesel engine at medium speed and load, but modified by adding -hexadecane to reach a hydrocarbon concentration of 3200 vol.ppm Ci and by varying the concentration of NO). Reprinted from ref. [72] with kind permission of Elsevier Science.

Diesel engines are classified by their rpm, as shown in Table 13.1. The majority of marine propulsion engines are slow-speed, two-stroke engines and the remainder are mainly medium-speed engines. The principal characteristics of the two engine types are outlined in the following sections. 

Table 16.1 shows the reported contamination failure modes for medium speed railway diesel engines [2], From a fleet of 1200 mainline locomotives, an average of about 320 contamination-related failure modes are detected and corrected each year. 

Table 16.7 is an example of viscosity limits for a medium speed diesel engine selected from the culled sample population in Fig. 16.22. These limits will reliably indicate fuel dilution and oil oxidation problems for the specific lubricant and fuel used. 

Fig. 13.2 Rate of heat release of a medium-speed DI diesel engine at fiill load...

These equilibrium reactions are needed to generate the H, O, N, and OH radicals at high temperature, before the slower kinetic reactions can be initialized. The coefficients and activation temperatures used in (13.4) and (13.9) for a medium-speed DI diesel engine are summarized in a study by Tanner and Srinivasan [49]. 

G. Weisser. Modelling of combustion and nitric oxide formation for medium-speed DI diesel engines zero and three-dimensional approaches. Ph.D. thesis, Swiss Federal Institute of Technology (ETH), Diss. ETH Nr. 14465, 2001. 

Systems for low- or medium-speed diesel engines used as gendrive or for propulsion of ships with fixed propellers often work with look-up tables or a characteristic curve as input for an open-loop reductant dosing control (Fig. 2.31). As the engines only use a small band within the engine map (Fig. 2.32) the NOx-emission and thus the reductant dosing rate has a fixed correlation to either engine speed or load. 

Standard Practices for Law and Medium Speed Stationary Diesel and Gas Engines, Diesel Engine Manufacturers Assodation, Cleveland, Ohio, 1972. 

Power/Propulsion - Auxiliary power of fishing vessels is normally provided by two or more diesel-electric generator sets or possibly main engine driven alternators on smaller vessels. Power distribution is by series switchboards, distribution panels and cabling systems. Emergency power sources are normally battery based. Medium speed engines (via a reduction gearing system) normally provide the propulsion power. 

Distillation (or volatility) characteristics of a diesel fuel exert a great influence on its performance, particularly in medium- and high-speed engines. Distillation characteristics are measured with a procedure (ASTM D-86, IP 123) in which a sample of the fuel is distilled and the vapor temperatures are recorded for the percentages of evaporation or distillation throughout the range. Other procedures are also available that are applicable to kerosene (Chapter 7). 

A further differentiation is the fuel. Most high-speed engines are using high-quality standard diesel fuel like trucks or passenger cars. However, heavy fuel oil (HFO), which can contain a significant amount of sulfur (up to 5 %) [1], is the preferred fuel for medium- and low-speed engines. 

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