Engine medium speed

These are fuels for low and medium speed engines or as a feedstock for catalytic cracker refining... 

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. 

These engines operate at speeds of 500 to 1,000 RPM and can develop 100 to 200 hp per cylinder with cylinder bore diameters up to 12 inches. Small stationary and marine power plants can be medium-speed engines. Also, railroad engines can be of this type. 

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. 

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. 

Fig. 2.3 Example of a large medium-speed engine (Bergen B32 40) (Picture Bergen Engines AS)...

An important difference between high-speed and low- or medium-speed engines with respect to the exhaust system is the fuel. 

Medium-speed engines can run with lower-quality fuels than high-speed engines. Lower-grade distillates as well as residual fuels (HFO) are used. As described in Table 2.1, for the SCR technology, important fuel characteristics are the content of ash, sulfur and for residual fuels also vanadium. 

Fig. 2.18 a Catalyst housing and b urea dosing panel for a medium-speed engine ship... 

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. 

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. 

D High-viscosity fuel for use in medium- and low-speed engines utilized in sustained load, constant-speed applications... 

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. 

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. 

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. 

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). 

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.

Table 13.3 Characteristics of medium-speed tmnk piston engines...

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]. 

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