Machine reciprocating

Compressors. There are two basic types of compressors centrifugal and reciprocating machines. The centrifugal compressor is usually used... 

Calculation of Actual Work of Compression For simplicity, the work of compression is calciilated by the equation for an ideal gas in a three-stage reciprocating machine with complete intercoohng and with isentropic compression in each stage. The work so calculated is assumed to represent 80 percent of the actual work. The following equation may be found in any number of textbooks on thermodynamics ... 

Many users consider rotaiy compressors, such as the Rootes -type blower, as turbomachines because their behavior in terms of the rotor dynamics is very close to centrifugal and axial flow machineiy. Unhke the reciprocating machines, the rotary machines do not have a veiy high vibration problem but, like the reciprocating machines, they are positive displacement machines. 

Reciprocating expansion engines have been used since the early twentieth century and are still used to some extent, especially for volumetric flows below 10 ft /min. Reciprocating machines often suffer from high maintenance, excessive size, valve problems, and tlie fact that liquid will damage the valves. For these reasons they have largely been replaced by turboexpanders, even down to sizes around 1 hp. 

Antivibration mounting A designed support placed between a rotating or reciprocating machine and the building structure to reduce the transmission of vibration. 

Simple cycle industrial gas turbines burn more fuel than comparable reciprocating machines. There are, however, several methods available to... 

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. 

The rotary compressor is adaptable to direct drive by the use of induction motors or multi-cylinder gasoline or diesel engines. These compressors are compact, relatively inexpensive, and require a minimum of operating attention and maintenance. They occupy a fraction of the space and weight of a reciprocating machine having equivalent capacity. 

Reciprocating linear-motion machines incorporate components that move linearly in a reciprocating fashion to perform work. Such reciprocating machines are bidirectional in that the linear movement reverses, returning to the initial position with each completed cycle of operation. Non-reciprocating linear-motion machines incorporate components that also generate work in a straight line, but do not reverse direction within one complete cycle of operation. 

Linear-motion machines generate vibration profiles similar to those of reciprocating machines. The major difference is the impact that occurs at the change of direction with reciprocating machines. Typically, linear-motion-only machines do not reverse direction during... 

Reciprocating compressors have unique operating dynamics that directly affect their vibration profiles. Unlike most centrifugal machinery, reciprocating machines combine rotating and linear motions that generate complex vibration signatures. 

Polytropic exponents are deduced from PV measurements on the machine in question. With reciprocating machines, the PV data are recorded directly with engine indicators. With rotary machines other kinds of instruments are used. Such test measurements usually are made with air. 

Volumetric Efficiency. For practical reasons, the gas is not completely discharged from a cylinder at each stroke of a reciprocating machine. The clearance of a cylinder is filled with compressed gas which reexpands isentropically on the return stroke. Accordingly, the gas handling capacity of the cylinder is less than the product of the cross section by the length of the stroke. The volumetric efficiency is... 

We further assume that the flow is steady in time. We make this assumption because most machines operate continuously, and even in reciprocating machines such as, for example, injection-molding machines, the flow can be viewed instantaneously as steady state. Finally, we assume that the fluid is incompressible and Newtonian, that the flow is fully developed, that is, dvz/dz 0, and that the gravitational forces are negligible compared to viscous forces. 

There are only a few centrifugal acid gas compressors installed in the world today (and note acid gas is the key word). Therefore, there is significantly less confidence in the prediction for centrifugal machines than for the reciprocating machines. 

Experience with reciprocating machines for other applications (sweet gas for example) indicates that the scaling factor is about 0.9. Thus, these machine do not quite scale directly with the required power. Table 12.1 lists an example centrifugal compressor. This is an estimate from one of the projects in my files. Using the scaling factor and this cost estimate gives ... 

Bio-oils have so far mainly been in the focus as an alternative fuel for internal combustion engines. The fuel obtained from fast pyrolysis, however, displays properties which do not lend themselves easily to this application. Intermittent combustion under high pressure in an reciprocating machine appears more demanding than continuous combustion under lower pressure in the combustion chamber of a gas turbine. This is the working assumption for the studies repotted below. 

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