Power stroke

Knock is caused by unwanted chemical reactions in the combustion chamber. These reactions are a function of the specific chemical species which make up the fuel and the environmental conditions to which the fuel is subjected during the compression and power stroke in the engine. Therefore, both the chemical makeup of the fuel and the engine design parameters must be considered when trying to understand knock. 

The uniflow design reduces cyhnder condensation and also allows greater expansion ratios per cyhnder (see Figs. 29-9 and 29-10). Steam is admitted during the start of the power stroke and after cutoff... 

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. 

The conformation change in the power stroke has been studied in two ways (1) cryoelectron microscopy together with computerized image analysis... 

N = number of power strokes per minute. For two cycle engines, N = engine rpm, for four-cycle engine,... 

F = length of piston stroke, ft N = number of power strokes per min n = number of poles for motor PF = power factor OR, = Fp P = power, or work, watts, or kW (kilowatts), also... 

Dynein sidearms interact with the walls of B-microtubules of adjacent doublets by means of a sliding-filament mechanism to produce ciliary movement. The process is energized by ATP hydrolysis. Movement of the cilium occurs in two stages, termed the power stroke and the recovery stroke. 

Dynein, kinesin, and myosin are motor proteins with ATPase activity that convert the chemical bond energy released by ATP hydrolysis into mechanical work. Each motor molecule reacts cyclically with a polymerized cytoskeletal filament in this chemomechanical transduction process. The motor protein first binds to the filament and then undergoes a conformational change that produces an increment of movement, known as the power stroke. The motor protein then releases its hold on the filament before reattaching at a new site to begin another cycle. Events in the mechanical cycle are believed to depend on intermediate steps in the ATPase cycle. Cytoplasmic dynein and kinesin walk (albeit in opposite... 

Formation of this complex promotes the release of Py which initiates the power stroke. This is followed by release of ADP and is accompanied by a large conformational change in the head of myosin in relation to its tail (Figure 49-7), pulling actin about 10 nm toward the center of the sarcomere. This is the power stroke. The myosin is now in a so-called low-energy state, indicated as actin-myosin. 

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