Category: Internal Combustion Engines

There are several parameters to indicate the performance of an IC engine, for example, indicated thermal efficiency (ηith), brake thermal efficiency (ηbth), mechanical efficiency (ηmech), volumetric efficiency (ηv), relative efficiency of efficiency ratio (ηrel), mean effective pressure (Pm), mean piston speed (Sp), specific power output (Ps), specific fuel consumption (sfc), and air fuel ratio (A/F).…

For same compression ratio, Otto cycle is more efficient but delivers less power than the diesel cycle. Therefore, in dual cycle partly heat is added at constant volume and partly at constant pressure as shown in Figure 6.17. Figure 6.17 ρ−V and T−s Diagrams for Dual Cycle   Example 6.6: An air standard dual cycle has a compression ratio of 18 and…

In a diesel cycle, heat is added at constant pressure and rejected at constant volume as shown in Figure 6.16. During heat addition, to maintain the constant pressure piston starts to move towards BDC. At point 3, injection is stopped which is known as cut-off point. Figure 6.16 Indicator Diagrams for Diesel Cycle Putting the value of T2, T3 and T4 in the…

In Figure 6.15, ideal P−V, actual P−V, and T−s diagrams are shown. There are some basic differences in ideal and actual indicator diagrams as valves do not open or close at sharp points practically. Valves start to open just before the point and close just after the points as shown in Figure 6.15b. The process 0−1 shows the suction of the charge…

Valve timing diagram for 4-s CI engine is shown in Figure 6.14 and timings are tabulated in Table 6.5. Figure 6.14 Valve Timing Diagram for Four Strokes CI Engines The timings for valves for 4-s CI engines is summarized in Table 6.5.   Table 6.5 Valve Timing for Four Strokes CI Engines Valve activity Theoretical timing Actual timing Inlet valve opens…

Port timing diagram for 2-s SI engines is shown in Figure 6.13. Figure 6.13 Port Timing Diagram for Two Strokes SI Engines The timings for ports for 2-s SI engines is summarized in Table 6.4.   Table 6.4 Port Timing for Two Strokes SI Engines Position Actual timing Inlet port opens 35° before BDC Inlet port closes 35° after…

Valve Timing Diagram for Four Strokes SI Engines Valve timing diagram is a graphical representation of valves opening and closing time with ignition time in terms of angle of crank revolution. Figure 6.12 shows the valve timing diagram for low speed four strokes SI engines. Practically valve cannot be opened or closed at any sharp points. Therefore,…

Comparison between Otto cycle and diesel cycle is summarized in Table 6.2b. Table 6.2b Comparison Between Otto Cycle and Diesel Cycle Otto cycle Diesel cycle In Otto cycle, heat added and rejected at constant volume.For same compression ratio, Otto cycle is more efficient than that of diesel cycle.Otto cycle is used in S.I engines. In diesel cycle,…

Comparison between SI and CI engines is summarized in Table 6.2a.   Table 6.2a Comparison Between SI and CI Engines SI engines CI engines It is based on Otto cycle or constant volume heat addition and rejection cycle.A high volatile, high self-ignition temperature fuel, gasoline is used.A gaseous mixture of fuel and air is inducted during suction…

The working of two strokes CI engine is very similar to two stroke SI engine. The main difference is that in CI engine supercharged air is used through the inlet port and in place of exhaust ports exhaust valves are used. Pressurized air is inducted through the inlet port which expels the combustion gases through…