Crank angle

After the forces are evaluated for each cylinder of a multistage compressor, all forces must be summed in the x and y direction. For the max imum shaking forces, the value of the crank angle, which contributes the maximum force, should be used. This involves taking the respective sine and cosine functions to their maximum. For example, a vertical cylinder will have the maximum component force at a crank angle of 0 and 180 . At this time, the horizontal components, primary and secondary, are zero. 

No. cylinders = 2, double-acting, 90° crank angle Cylinder diameter = 34 in. 

Top view of a piston engine at a crank angle of 10°. Cross-section colored by the reaction rate for four different cycles. (From Richard, S., Colin, O., Vermorel, O., Benkenida, A., Angelberger, C., and Veynante, D., Proc. Comb. Inst., 31,3059,2007.)... 

Mass fraction burnt (mfb) curves from each of the three engine concepts discussed in this chapter. Time is presented as crank-angle-degrees after ignition is initiated. 

Smith, J.D. and V. Sick, Crank-Angle Resolved Imaging of Fuel Distribution, Ignition and Combustion in a Spark-Ignition Direct-Injection Engine. SAE Paper 2005-01-3753,2005. 

Fajardo, C.M. and V. Sick, Flow field assessment in a fired spray-guided spark-ignition direct-injection engine based on UV particle image velocimetry with sub crank angle resolution. Proceedings of the Combustion Institute, 31(2) 3023-3031, 2007. 

The relative fluctuations in nitrogen density versus crank angle are indicated by the solid curve shown in Figure 5. Prior to ignition, the fluctuation level was quite low. The fluctua-... 

Figure 4. Relative mean nitrogen number density vs. crank angle...

NEAR MOST PROBABLE FLAME ARRIVAL CRANK ANGLE... 

Clearly these large fluctuations are due to cyclic variations not turbulent fluctuations. The dashed curve is an attempt to remove this cyclic variation effect by using the most probable density value as the mean value of a normal distribution. The standard deviation of the distribution is determined from fitting the data to the side of the new mean that has not been distorted by flame arrival. The reduction of the apparent fluctuations near the flame arrival crank angle is dramatic. Both curves of Figure 5 have had the Poisson statistical fluctuations subtracted. 

Figure 7.2. Snapshots of reaction rate in a simulation of piston engine at four successive cycles for the same crank angle. None of them is the same.

Spark timing, crank angle before tdc 13 14 to 26° (depends on CR)... 

By subtracting the heat release rate in a non-knocking cycle from that in a knocking cycle it is possible to estimate the heat released by autoignition as a function of crank angle [106]. The variations in heat release rates for three different knock intensities are shown in Fig. 7.13. The onset of knock is indicated by an asterisk and occurs at the maximum heat release rate, which is appreciable at the highest knock intensity. The unburned mass fraction is shown by the axis at the left and it shows that... 

Fig. 7.13. Net heat release rate, Q, and unburned mass fractions at different crank angles for knock intensities of (1) 1490, (2) 111 and (3) 6.5 kPa. Asterisks denote onset of knock. Fuel PRF, stoichiometric mixture. From [106].

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