a new look at High Compression Engines

Effect of compression ratio and spark timing on the power performance and combustion characteristics of an HCNG engine

“…7, the improvement in brake thermal efficiency at early ignition timing is not as significant as at late ignition timing. Caris and Nelson [15] show that mechanical efficiency is only a function of manifold absolute pressure (MAP) with higher MAPs giving higher mechanical efficiencies. With the same MAPs for different compression ratios, the mechanical efficiencies are the same.…”

Facts about Producer Gas Engine

“…The knock sensitivity identifies the Highest Useful Compression Ratio (HUCR) for most of the fuels having higher octane number. For higher-octane fuels, it has been experimentally established that the upper limit of CR is 17 beyond which there is a fall in efficiency (Caris & Nelson, 1959). The salient features of the diesel engine chosen for conversion to SI engine are shown in Table 2.…”

Occult parasitic energy loss in heat engines

“…Figure 9 illustrates this by showing a regional bifurcation to the upper and lower values of Equation (10). Equations (17) and (18) are also shown superimposed with internal combustion engine data extracted from Caris-Nelson (1959). These data, which apparently follow the lower branch of the bifurcation, are particularly important since the observed behaviour is anomalous to the standard fuel-air cycle model and to Equation (12) (theta-class) by exhibiting an unexpected efficiency peak at 17:1 compression ratio where monotonic behaviour is expected.…”

“…A representative example is shown in Figure 1 where theoretical predictions (solid and dashed traces) from Taylor (1985) and Angulo-Brown et al (1996) are presented with experimental measurements (discrete data points) from Kerley-Thurston (1962) and Caris-Nelson (1959) of Otto-cycle (spark ignition) engine efficiencies as functions of compression ratio. The disparity between theory and experiment is evident and substantial.…”