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| Illustration 1 | g00776843 |
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Diagram for a turbocharged air inlet and exhaust system with high pressure gas (1) Gas pressure regulator (2) Balance line (3) Carburetor (4) Air cleaner (5) Turbocharger (6) Gas supply (7) Governor (8) Aftercooler (9) Air inlet manifold (10) Cylinder (11) Regulator (12) Exhaust manifold | |
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| Illustration 2 | g00776844 |
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Diagram for a turbocharged air inlet and exhaust system with low pressure gas (AA) Exhaust gas (BB) Air and gas to cylinders (CC) Gas supply (DD) Low pressure gas (EE) Air inlet (1) Gas pressure regulator (2) Balance line (3) Carburetor (4) Air cleaner (5) Turbocharger (6) Gas supply (7) Governor (8) Aftercooler (9) Air inlet manifold (10) Cylinder (11) Regulator (12) Exhaust manifold | |
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| Illustration 3 | g00664642 |
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Low pressure gas, air inlet and exhaust system without turbocharger (1) Gas pressure regulator (2) Balance line (3) Carburetor (4) Air cleaner (6) Gas supply (7) Governor (9) Air inlet manifold (10) Cylinder (12) Exhaust manifold | |
Fuel from gas supply (6) flows to pressure regulator (1). After the gas is reduced to the desired pressure by the regulator, the gas flows to carburetor (3).
Inlet air is filtered by air cleaner (4).
On high pressure gas fuel systems, turbocharger (5) delivers compressed air to the carburetor. Boost pressure is delivered to the gas pressure regulator through balance line (2) in order for the regulator to maintain the differential pressure between the gas and the inlet air.
With low pressure gas, the air and the fuel are mixed in the carburetor and the mixture is compressed by the turbocharger.
Governor (7) controls the opening of the throttle. The air and fuel is cooled in aftercooler (8) before entering air inlet manifold (9) and cylinders (10).
Exhaust gas travels to exhaust manifold (12). Some of the exhaust gas drives turbocharger (5) before the exhaust gas exits through the exhaust outlet. If the boost pressure is excessive, some of the exhaust gas is diverted by regulator (11) (if equipped) to the exhaust outlet.
Note: On some turbocharged engines, a boost control valve diverts excessive compressed air away from the air inlet manifold in order to control the boost pressure.
Some systems have a gas shutoff valve in the supply line. This valve may be electrically operated from the ignition system. The valve can be operated manually in order to stop the engine. Manual resetting of the valve is needed in order to restart the engine.
Engine installations that use dual fuel systems have components that are similar to the components in the above illustrations. However, an engine that uses a dual fuel system requires two gas pressure regulators. When the gas is changed, adjustments must be made for differences in the BTU content of the gas. An engine that has a dual fuel system can change fuels automatically. The engine timing must be adjusted when the fuel is switched. This can be accomplished with a magneto that is equipped for dual timing.
The carburetor combines gas and air in order to establish a combustible mixture. The carburetor controls the flow of the mixture to the throttle. The carburetor also controls the exhaust emissions.
The jets and the valves are interchangeable on the carburetor for low pressure gas. A change in the jets and the valves will allow the carburetor to burn a variety of fuels. The system can burn the following fuels: propane gas, natural gas and fuels with low Btu. The jets and the valves can also be changed in order to be used with an air/fuel ratio control when a catalyst is used.
Carburetor (High Pressure Gas)
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| Illustration 4 | g00664696 |
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Cross section of the carburetor (1) Diaphragm (2) Sensing holes (3) Spring (4) Fuel valve (5) Chamber (6) Air horn (7) Ring (8) Outer chamber (9) Fuel outlet port (10) Inner chamber (11) Fuel inlet port (12) Idle adjustment (13) Load adjusting valve (14) Throttle plate (15) Connection for the balance line | |
Air flows into the carburetor through air horn (6). The air fills outer chamber (8). Air moves diaphragm (1) away from ring (7). The air then flows into inner chamber (10) (mixing chamber).
Fuel flows into the carburetor through fuel inlet (11). The fuel then flows by load adjusting valve (13) into the center of the carburetor and into fuel outlet port (9). Fuel valve (4) is fastened to diaphragm (1). While the diaphragm is moved away from ring (7), the fuel flows through fuel valve (4) into inner chamber (10). The air/fuel mixture flows through throttle plate (14) into the inlet manifold.
When the engine is stopped, spring (3) holds diaphragm (1) against ring (7). This holds fuel valve (4) closed. No air or fuel can enter inner chamber (10). When the engine is started a vacuum in the cylinders is created by the intake strokes of the pistons. This creates low pressure in inner chamber (10). This low pressure is felt in chamber (5) behind the diaphragm through holes (2). This permits the pressure in chamber (5) to balance with the low pressure in the inner chamber. When the inlet pressure on diaphragm (1) becomes higher than the spring force, the diaphragm moves out.
Fuel valve (4) moves out. This allows the air/fuel mixture to go into the inner chamber. A small volume of air is also measured into the inner chamber (10). This small volume of air is entered through the opening for idle adjustment (12).
When the engine is operating at a constant load and speed, the position of the diaphragm is constant. The diaphragm only moves when the demand for fuel varies.
Operation of a carburetor with a single diaphragm is described below. Carburetors with more than one diaphragm operate in the same manner.
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| Illustration 5 | g00812091 |
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Flow of air and gas into the carburetor (1) Filtered air (2) Gas | |
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| Illustration 6 | g00742168 |
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Section view of the carburetor and the throttle The carburetor and the throttle plate are in the open position. (1) Filtered air (2) Gas (3) Spring (4) Valve (5) Jet (6) Diaphragm (7) Passage (8) Load control valve (9) Throttle body | |
When the engine is stopped, spring (3) presses valve (4) against jet (5). No air or fuel can enter the mixing chamber of the carburetor.
As the engine is started, the intake strokes of the pistons generate a vacuum in the cylinders. The vacuum draws filtered air (1) into the carburetor. A vacuum pulls through passage (7) so that the vacuum pulls on top of diaphragm (6). When the vacuum's pull on top of the diaphragm is greater than the force of spring (3), the diaphragm moves toward the cover of the carburetor and valve (4) moves away from jet (5). This allows filtered air and gas to enter the mixing chamber. The air/fuel mixture flows past the throttle plate in throttle body (9) into the air inlet manifold.
When the engine is operating at a constant load and speed, the position of the diaphragm is constant. The diaphragm only moves when the demand for fuel varies.
Load control valve (8) is used to adjust the air/fuel ratio at full load. The position of the valve determines the quantity of gas that enters the carburetor. The valve causes the air/fuel ratio to be rich or lean. The exhaust emissions are adjusted with this valve.
The turbocharger is installed at the rear of the exhaust manifold.
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| Illustration 7 | g00742139 |
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(1) Air inlet
(2) Compressor wheel (3) Lubrication inlet port (4) Turbine wheel (5) Thrust bearing (6) Shaft bearings (7) Connections for coolant lines (8) Exhaust outlet | |
The exhaust gas drives the blades of turbine wheel (4). This drives compressor wheel (2). The exhaust gas exits the turbocharger through outlet (8) to the exhaust stack.
On high pressure gas fuel systems, the compressor wheel pulls clean inlet air from the air cleaners through air inlet (1) of the compressor housing. The compressor wheel compresses the air. The turbocharger delivers compressed air to the carburetor. With low pressure gas, the air and the fuel are mixed in the carburetor and the mixture is compressed by the turbocharger.
The turbocharger bearings are lubricated with pressurized engine oil. The engine oil enters through port (3) into passages for lubrication of thrust bearing (5) and of shaft bearings (6). Engine oil leaves the turbocharger through an opening in the bottom of the center section. The engine oil returns to the engine oil pan.
The turbine housing is cooled with coolant from lines that are attached to connections (7).
The boost control valve is used with some turbochargers.
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| Illustration 8 | g00660630 |
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Boost control valve (1) Opening to the carburetor (2) Valve (3) Vent hole (4) Spring (5) Opening from the turbocharger | |
The boost control valve is located in the air supply line to the carburetor. The housing has a spring loaded valve (2). The pressure of the spring (4) keeps valve (2) in an open position. This permits full air pressure from the turbocharger to go through the valve. When pressure from the turbocharger is increased, the air pressure is pushed against the cone-shaped face of valve (2). When the maximum pressure is reached, the valve is almost closed. The air is returned to the air cleaner via a tube that is attached to vent hole (3). The vent hole must always be open.
Regulator (Exhaust Bypass Valve)
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| Illustration 9 | g00809789 |
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Regulator | |
The regulator is used with some turbochargers. The regulator controls the amount of exhaust gas to the turbine wheel in order to maintain the desired boost pressure. The regulator limits the amount of inlet manifold air pressure (boost) in order to limit the engine's power output.
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| Illustration 10 | g00809791 |
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(1) Opening for the tube from the aftercooler
(2) Diaphragm (3) Spacer (4) Spring (5) Shim (6) Valve (7) Opening for the breather (8) Exhaust gas to the turbocharger (9) Exhaust gas to the exhaust stack | |
Valve (6) is activated directly by a pressure differential.
Atmospheric pressure is exerted through opening (7) for the breather on one side of diaphragm (2). Force from spring (4) is on the same side of the diaphragm. The force of the spring is adjusted with spacers (3) and with shims (5).
Boost pressure is exerted on the other side of the diaphragm through opening (1) for a tube from the aftercooler. On the same side of the diaphragm, exhaust gas exerts pressure on valve (6).
When the force of the spring plus the atmospheric pressure is overcome, valve (6) opens in order to divert some exhaust gas (8) from the turbocharger to exhaust stack (9). This prevents the turbocharger from providing too much boost pressure.
Excessive boost pressure can result in overloading of the engine, overheating, detonation, and turbocharger surge. The amount of exhaust gas to the turbine wheel is maintained in order to provide the correct boost pressure. The boost pressure determines the throttle angle at full load operation.
Under constant load conditions, the valve maintains a set position.
When the turbocharger compresses the inlet air, the temperature of the air rises. A water cooled aftercooler is located between the carburetor and the air inlet manifold. The aftercooler reduces the temperature of the air from the turbocharger. The cooler air is more dense and the cooler air provides more oxygen for combustion. More oxygen enables more fuel to be burned. This increases the engine power.
The gas pressure regulator controls the gas pressure to the carburetor relative to the air pressure to the carburetor.
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| Illustration 11 | g00742150 |
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Gas pressure regulator (1) Air chamber (2) Adjusting screw (3) Spring (4) Balance line (5) Outlet for gas (6) Diaphragm (7) Chamber for gas (8) Lever (9) Pivot pin (10) Valve stem (11) Valve (12) Inlet for gas | |
The fuel flow is determined by the pressure differential between the gas pressure and the air pressure. Usually, the pressure of the gas must be greater than the air pressure.
To maintain an accurate adjustment of the gas pressure to the carburetor, balance line (4) is connected to the air inlet of the carburetor. This causes the air pressure on the air side of diaphragm (6) to be equal to the air pressure in the carburetor.
Spring (3) and air pressure in air chamber (1) presses on diaphragm (6). The movement operates lever (8) at pivot pin (9). The lever moves valve stem (10) and valve (11). This allows gas from inlet (12) to enter chamber (7). The valve stops opening when the gas pressure in chamber (7) under the diaphragm is equal to the force from the spring and the air pressure in air chamber (1). The gas exits the regulator through outlet (5).
The pressure of the gas from the regulator is adjusted with screw (2). The pressure must be adjusted for the type of carburetor.
As the load increases, the governor opens the throttle plate further. This reduces the pressure on the gas side of the diaphragm. The spring force and the air pressure open the gas valve. The gas valve opens until the pressure under the diaphragm is balanced again with the forces of the spring and pressure from the balance line on top of the diaphragm.
The balance line is connected to the air inlet of the carburetor and to the air chamber in the gas regulator. The balance line helps to maintain the correct gas pressure to the carburetor regardless of the load.
On naturally aspirated engines, any restriction of the inlet air causes the balance line to create a corresponding vacuum in the air chamber of the gas pressure regulator. The vacuum pulls up on the diaphragm and the gas valve closes. This restricts the gas in order to ensure a consistent fuel flow regardless of the air restriction.
On turbocharged engines, the balance line delivers the boost pressure to the regulator's air chamber. The boost pressure on the diaphragm allows the regulator to provide more fuel. Again, a constant air/fuel ratio is maintained.
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| Illustration 12 | g06170382 |
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Timing gears (3304 Engine) (1) Drive gear for the magneto (2) Idler gear for the magneto drive gear (3) Camshaft gear (4) Crankshaft gear (5) Balancer shafts (6) Idler gear for the engine oil pump (7) Drive gear for the engine oil pump | |
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| Illustration 13 | g00660762 |
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Timing gears (3306 Engine) (1) Drive gear for the magneto (2) Idler gear for the magneto drive gear (3) Camshaft gear (4) Crankshaft gear (5) Idler gear for the engine oil pump (6) Drive gear for the engine oil pump | |
The timing gears are at the front of the cylinder block. The housing covers the timing gears. The timing gears keep the rotation of the crankshaft, of the camshaft, and of the magneto in the correct relation to each other. The timing gears are driven by the crankshaft gear.
The 3304 Engine has balancer shafts. The balancer for the right side of the engine is driven by the idler gear for the oil pump. The balancer for left side of the engine is driven by the drive gear for the oil pump.
The valves and the valve mechanism control the flow of air and the exhaust gases in the cylinder during engine operation.
As the camshaft rotates, the lobes of the camshaft move the valve lifters and pushrods upward. The pushrods move the rocker arms. The movement of the rocker arms opens the inlet valves and exhaust valves according to the firing order of the engine. As the camshaft continues to rotate, the lobes of the camshaft allow the pushrods and valve lifters to move downward. A valve spring for each valve closes the valves when pressure is removed from the rocker arms.
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| Illustration 14 | g00660982 |
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Mechanical Governor (1) Flyweights (2) Spring (3) Valve (4) Piston (5) Passage for engine oil (6) Sleeve (7) Spring seat (8) Outlet passage for engine oil (9) Cylinder (10) Inlet passage for engine oil (11) Shaft | |
When the engine is running, the centrifugal force of flyweights (1) and the force of spring (2) controls the movement of valve (3). The valve directs oil pressure to either side of piston (4). The position of valve (3) will cause piston (4) to move shaft (11). The movement of the shaft changes the volume of the fuel supply when the load on the engine changes.
Engine oil under pressure goes into passage (10) and into cylinder (9). The engine oil goes around sleeve (6) inside cylinder (9). The engine oil then goes through a passage in piston (4). The engine oil contacts valve (3).
When the engine load is increased, engine rpm is decreased and the rotation of flyweights (1) slows down. The flyweights move toward each other. This allows spring (2) to move valve (3) forward. As the valve moves, the passage around the valve is opened to pressurized engine oil. The engine oil goes through passage (5). This fills the chamber behind piston (4). The pressure of the engine oil forces the piston and the shaft forward. This increases the amount of fuel to the engine. The engine rpm is increased until the centrifugal force of flyweights (1) is balanced with the force of spring (2).
When the engine load is decreased, engine rpm is increased and flyweights (1) rotate faster. The toes of the flyweights move valve (3) backward. This allows the engine oil behind piston (4) to go through passage (8). At the same time, the engine oil is under pressure between sleeve (6) and piston (4). The engine oil pressure forces the piston backward and the engine oil pressure forces shaft (11) backward in order to reduce the amount of fuel to the engine. Engine rpm is decreased until the rotation of flyweights (1) is balanced with the force of spring (2).
After the governor is lubricated with engine oil, the engine oil drains into the governor drive housing and into the timing gear housing.
Woodward Pressure Compensated Simple Governor (PSG)
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| Illustration 15 | g00332574 |
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Schematic of governor (1) Return spring (2) Output shaft (3) Output shaft lever (4) Strut assembly (5) Speeder spring (6) Power piston (7) Flyweights (8) Needle valve (9) Thrust bearing (10) Pilot valve compensation land (11) Buffer piston (12) Pilot valve (13) Pilot valve bushing (14) Control ports (A) Chamber (B) Chamber | |
The governor can operate as an isochronous governor. This governor uses engine lubrication oil that has been increased to a pressure of
The governor is driven by the governor drive unit. This unit turns pilot valve bushing (13). The bushing is turned in the clockwise direction when the bushing is viewed from the drive end of the governor. The pilot valve bushing is connected to a ballhead assembly that is driven by a spring. Flyweights (7) are fastened to the ballhead by pivot pins. Centrifugal force is created by the rotation of the pilot valve bushing. The flyweights pivot outward changing the centrifugal force to axial force. This force presses against speeder spring (5). Thrust bearing (9) is between the toes of the flyweights and the seat for the speeder spring. Pilot valve (12) is fastened to the seat for the speeder spring. Movement of the pilot valve is controlled by the action of the flyweights against the force of the speeder spring.
When the engine is at governed rpm, the axial force of the flyweights is equal to the force of compression in the speeder spring. The flyweights will be in the position that is shown. Control ports (14) will be closed by the pilot valve.
Increase In Fuel
When the operator desires an increase in rpm, the speeder spring will increase. If the load on the engine increases, the axial force of the flyweights decreases. The force of compression in the speeder spring may increase. The axial force of the flyweights may decrease. The pilot valve will always move in the direction of the drive unit. This opens control ports (14). Pressurized engine oil flows through a passage in the base to chamber (B). The increased pressure in chamber (B) causes power piston (6) to move. The power piston pushes strut assembly (4) and output shaft lever (3). The action of the output shaft lever causes counterclockwise rotation of output shaft (2). This moves the control linkage (15) for the carburetor. The control linkage moves in order to open the throttle.
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| Illustration 16 | g00917051 |
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Governor (2) Output shaft (15) Control linkage | |
As the power piston moves in the direction of return spring (1) the volume of chamber (A) increases. The pressure in chamber (A) decreases. This pulls the engine oil from the chamber inside the power piston. The engine oil continues above buffer piston (11) into chamber (A). The buffer piston moves upward in the bore of the power piston. Chamber (A) and chamber (B) are connected to the chambers that are above and below pilot valve compensation land (10). The pressure difference that is felt by the pilot valve compensation land adds to the axial force of the flyweights. This force moves the pilot valve upward. This action closes the control port. When the flow of pressurized engine oil to chamber (B) stops, the movement of the fuel control linkage also stops.
Decrease In Fuel
When the force of compression in the speeder spring decreases, or the axial force of the flyweights increases, the pilot valve moves in the direction of speeder spring (5). This opens control ports (14). Engine oil from chamber (B) and pressurized engine oil from the pump moves through the end of the pilot valve bushing. The decrease in pressure in chamber (B) allows the power piston to move in the direction of the drive unit. Return spring (1) pushes on strut assembly (4). This moves output shaft lever (3). The action of the output shaft lever causes the clockwise rotation of output shaft (2). This moves control linkage (15) for the carburetor toward the minimum fuel position.
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| Illustration 17 | g00741780 |
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(1) Screw
(2) Linkage assembly (3) Speeder spring (4) Pilot valve | |
On governors that are not equipped with electric speed adjustment, speed can be adjusted with screw (1). When the screw is turned clockwise the screw pushes link assembly (2) against speeder spring (3). This causes an increase in the force of the speeder spring and pilot valve (4) moves toward the magneto and governor drive. Refer to "Pilot Valve Operation". The engine will increase speed until the engine reaches the desired rpm. When the screw is turned counterclockwise the link assembly moves away from the speeder spring. This causes a decrease in the force of the speeder spring and the pilot valve moves away from the magneto and governor drive. The engine will decrease speed until the desired rpm is reached.
Engines with nonelectric governors are also equipped with a governor control to allow easier speed adjustment.
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| Illustration 18 | g00741803 |
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(5) Positive lock lever
(6) Rod (7) Lever (8) Governor | |
As positive lock lever (5) is moved counterclockwise, the linkage causes lever (7) to move in the clockwise direction. Lever (7) is clamped to the shaft of linkage assembly (2). As the shaft turns, the linkage assembly pushes on speeder spring (3). This causes pilot valve (4) to move toward the magneto and governor drive. Refer to "Pilot Valve Operation". The engine will increase speed until the desired rpm is reached.
When lever (5) is moved clockwise, lever (7) moves in the opposite direction. This causes the link assembly to move away from the speeder spring. The pilot valve then moves away from the magneto and governor drive. Engine speed decreases until desired rpm is reached.
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| Illustration 19 | g00679845 |
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Electric PSG (1) Synchronizing motor (2) Clutch assembly (3) Link assembly | |
The speed adjustments are made by a 24 volt DC reversible synchronizing motor (1). This motor is controlled by a switch that can be put in a remote location.
The synchronizing motor drives clutch assembly (2). The clutch assembly protects the motor in case the motor is run against the adjustment stops.
When the clutch assembly is turned clockwise, linkage assembly (3) will push on the speeder spring. The force of compression in the speeder spring increases. This causes the pilot valve to move toward the magneto and governor drive. Refer to "Pilot Valve Operation". The engine will increase in speed until the engine reaches stability at the new desired rpm.
When the clutch assembly is turned counterclockwise, the link assembly moves away from the speeder spring. The force of compression in the speeder spring is decreased. This causes the pilot valve to move away from the magneto and governor drive. The engine will decrease in speed until the engine reaches stability at the new desired rpm.
Note: The clutch assembly can be turned manually if it is necessary.
Isochronous - The engine rpm remains constant from high idle at no load to full load operation. This is known as zero percent droop.
Droop - Droop represents a decrease in rpm from high idle at no load to full load operation.
Speed droop enables the load to be shared between two or more engines that drive generators that are connected in parallel. The speed droop also functions in the same manner with generators that are connected to a single shaft. The percentage of droop can be calculated according to the equation in Table 1.
| Equation for Calculating the Percent of Speed Droop | ||||||
| H − F | × | 100 | = | % Droop | ||
| F | ||||||
| H is the high idle rpm.
F is the full load rpm. |
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| Illustration 20 | g00741825 |
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PSG (1) Output shafts (2) Link assembly (3) Pivot pin (4) Adjusting bracket (5) Shaft assembly | |
Adjusting bracket (4) is outside of the governor. This bracket is connected to pivot pin (3) by link assembly (2) and shaft assembly (5). The bracket is used to adjust the speed droop.
Adjustment of the droop on the governor is made by the movement of pivot pin (3). When the pivot pin is aligned with output shafts (1), movement of the output shaft lever will not change the force of the speeder spring. When the force of the speeder spring is kept constant, the desired rpm will be kept constant. Refer to "Pilot Valve Operation".
When the pivot pin is moved out of alignment with the output shafts, movement of the output shaft lever changes the force of the speeder spring proportionally with the load on the engine. When the force of the speeder spring is changed, the desired rpm of the engine will change.