18-04-2017, 11:29 AM
Miller cycle gas engine PPT presentation
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miller cycle gas engine ppt presentation
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Miller cycle gas engine PPT presentation
19-04-2017, 12:31 PM
The Miller cycle is an over-expanded cycle implemented with Early Intake (EIVC) or late valve closure (LIVC). Miller has been implemented in both diesel engines and gasoline engines. In diesel engines, the Miller cycle has been used primarily to control NOx emissions at high engine loads. In gasoline engines, Miller cycle benefits include reducing pumping losses to partial load and improving efficiency, as well as mitigating blows.
The Miller cycle was developed by Ralph Miller in the 1940s. With the introduction of turbocharging to 4-stroke diesel engines, the average effective pressure and therefore the power of 4-stroke engines increased by between 50 and 60%. However this was about the limit; If the inlet air pressure was increased further, then the charge air reached excessive compressive pressures and temperatures which caused combustion of the LO film and thermal stress.
Miller defied the thought of the day by closing the inlet valve before the piston reached the bottom dead center. This had the effect of lowering the cylinder pressure as the piston continued downward as well as the drop in air temperature (Boyles and Charles Act). Although the engine continues to work while the piston is descending in the inlet stroke, there is a labor saving during the compression stroke and the maximum air temperature and pressure are reduced to compression. The timing of the Miller engine inlet valve was governed by a mechanical link arrangement, and varied automatically with the engine load. The Miller engine doubled the engine MEP compared to a natural aspiration engine.
Advances in design and materials led to more efficient turbochargers, higher compression ratios and more efficient cooling of marine diesel engines. However, with the introduction of MARPOL VI, manufacturers had to look more closely at reducing NOx and smoke emissions.
One of the methods used is to reintroduce the Miller cycle with variable inlet closure, so that at full load, the maximum cylinder temperature is reduced. (NOx formation occurs at temperatures above 1200 ° C). This is combined with higher compression ratios and a slightly later fuel injection time.
Miller relied on mechanical methods to vary the time. Modern methods linked to a computer controlled engine management system use a hydraulic pusher.
The Miller cycle was developed by Ralph Miller in the 1940s. With the introduction of turbocharging to 4-stroke diesel engines, the average effective pressure and therefore the power of 4-stroke engines increased by between 50 and 60%. However this was about the limit; If the inlet air pressure was increased further, then the charge air reached excessive compressive pressures and temperatures which caused combustion of the LO film and thermal stress.
Miller defied the thought of the day by closing the inlet valve before the piston reached the bottom dead center. This had the effect of lowering the cylinder pressure as the piston continued downward as well as the drop in air temperature (Boyles and Charles Act). Although the engine continues to work while the piston is descending in the inlet stroke, there is a labor saving during the compression stroke and the maximum air temperature and pressure are reduced to compression. The timing of the Miller engine inlet valve was governed by a mechanical link arrangement, and varied automatically with the engine load. The Miller engine doubled the engine MEP compared to a natural aspiration engine.
Advances in design and materials led to more efficient turbochargers, higher compression ratios and more efficient cooling of marine diesel engines. However, with the introduction of MARPOL VI, manufacturers had to look more closely at reducing NOx and smoke emissions.
One of the methods used is to reintroduce the Miller cycle with variable inlet closure, so that at full load, the maximum cylinder temperature is reduced. (NOx formation occurs at temperatures above 1200 ° C). This is combined with higher compression ratios and a slightly later fuel injection time.
Miller relied on mechanical methods to vary the time. Modern methods linked to a computer controlled engine management system use a hydraulic pusher.
![[Image: VIC_1.gif]](http://www.marinediesels.info/2_stroke_engine_parts/Other_info/VIC_1.gif)
Low load operation: The throttle valve opens against a spring as the follower moves up the cam and oil moves under the piston of the push rod, opening the valve. When the follower detaches from the cam, the throttle valve closes and the oil can only flow through the throttle hole, delaying the closing of the intake valves.
![[Image: VIC_2.gif]](http://www.marinediesels.info/2_stroke_engine_parts/Other_info/VIC_2.gif)
In full load operation, an air signal opens the throttle valve. This means that as soon as the follower descends from the cam spout, the plunger piston moves downward, allowing the inlet valves to close.
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