Port cylinder

Regarding the expenditure for technical instruments as well as the investment costs, the principle of the port cylinder represents an attractive alternative for gas-liquid separation. 

It is to be inferred from the performance data described in Figure 3.18 that in the case of LRVPs with port cylinder, the suction capacity and the power consumption are affected only marginally by the water quantity conveyed. The port cylinder permits the conveyance of three to four times the liquid quantity compared to the... 

Figure 3.18 Influence of additional water on the performance data of a liquid ring vacuum pump with port cylinder.

Three-way valves contain a pressure port, cylinder port, and return or exhaust port (see Figure 9.11). The three-way directional control valve is designed to operate an actuating unit in one direction. It is returned to its original position either by a spring or the load on the actuating unit. 

I Figure 11 -2. The compressor frame is the rugged casting thot contains the rotating I ports and on which the cylinders and crossheods are mounted. [Courtesy of, Dresser-Rand Company,]... 

As the piston begins its leftward stroke from bottom dead center (BDC), both inlet and exhaust ports are uncovered and air from some external source is flowing through the cylinder. Directional control is provided through port and/or piston design to ensure the most complete cylinder scavenging possible. 

At Point 2, the air intake is closed, but compression does not begin until the exhaust port is covered also. Shortly after the exhaust port is closed and compression of the trapped air begins, fuel is injected at Point 3 into the cylinder through a high pressure fuel valve. At Point 4, just prior to completion of the compression stroke, a spark ignites the fucl/ iir mixture and the pressure rises rapidly through the remainder of the compression stroke and the beginning of the power stroke. 

Note in Figure 5 that with the piston near BDC, both intake and exhaust ports are open concurrently. This provides a pathway whereby some of the incoming charge can short-circuit the cycle and exit with the exhaust gas. If the engine uses an upstream carburetor to mix fuel into the air before the charge enters the crankcase, then a fraction of the fuel leaves with the exhaust gas. That penalizes fuel economy and iticreases exliaust emissions. This escape path for unburned fuel can be eliminated by injecting fuel directly into the cylinder after both ports are closed, hut at the cost of increased complexity. 

Such tight mixture control is beyond the capability of the traditional carburetor. Consequently, after sorting through a number of alternatives, industry has settled on closed-loop-controlled port-fuel injection. Typically, an electronically controlled fuel injector is mounted in the intake port to each cylinder. A sensor in the air intake system tells an onboard computer what the airdow rate is, and the computer tells the fuel injectors how much fuel to inject for a stoichiometric ratio. An oxygen sensor checks the oxygen content in the exliaust stream and tells the computer to make a correction if the air/fuel ratio has drifted outside the desired range. This closed-loop control avoids unnecessary use ot an inefficient rich mixture during vehicle cruise. 

This is the total volume remaining in the cylinder at the end of the piston stroke. This consists of the volume between the end of the piston and the cylinder head, in the valve ports and the volume in the suction valve guards and the discharge valve seats. See Figures 12-12,12-17A, and 12-17B. 

Pressure values along the top of each table are differential pressures across the two cylinder ports. This is the pressure to just balance the load and not the pressure that must be produced by the system pump. There will be circuit flow losses in pressure and return lines due to oil flow and these will require additional pressure. When designing a system, be sure to allow sufficient pump pressure, about 25 per cent to 30 per cent, to supply both the cylinder and to satisfy system flow losses. 

Bore Rod Effective Pressure differential across cylinder ports ... 

Bore diameter (in) Rod diameter (in) Effective area (in ) Pressure differential across cylinder ports ... 

In a two-cycle machine, all pistons complete a full cycle each time the crankshaft completes one revolution. Figure 44.9 illustrates the normal action of a two-cycle, or single-action, compressor. Inlet and discharge valves are located in the clearance space and connected through ports in the cylinder head to the inlet and discharge connections. 

A refrigeration system will be designed to have a maximum duty to balance a calculated maximum load, and for much of its life may work at some lower load. Such variations require capacity reduction devices, originally by speed control (when steam driven) or in the form of bypass ports in the cylinder walls. 

Smaller machines may have a valved bypass across the inlet and outlet ports in the cylinder head, or a variable clearance pocket in... 

The solution of the sample to be analysed (1-100 pL) is introduced by inserting the tip of a micropipette through a port in the outer (water) jacket, and into the gas inlet orifice in the centre of the graphite tube. The graphite cylinder is then heated by the passage of an electric current to a temperature... 

Non-return valves are essential in the operation of pumps. It is important to ensure that when the pump compresses the solvent, it leaves at the exit port and is completely arrested at the inlet port. Conversely when the pump draws fresh solvent into the cylinder, the non-retum valves must allow solvent to flow through the inlet valve, but flow-back from the other side of the exit valve must be... 

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