Month: December 2022
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Conduction
Conduction is the heat transfer from one part of a substance to another part of the same substance, or from one substance to another in physical contact with it, without appreciable displacement of the molecules forming the substance. On the elementary particle level, the conduction is visualized as the exchange of kinetic energy between the…
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INTRODUCTION
This deals with different modes of heat transfer which are usually classified as conduction, convection and radiation. From the second law of thermodynamics, we know that the heat flows whenever there is existence of temperature difference or temperature gradient. Heat is a form of energy which is transferred from one body to another body at…
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ENGINE PERFORMANCE PARAMETERS
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).…
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DUAL CYCLE
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…
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DIESEL CYCLE
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…
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OTTO CYCLE
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…
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Valve Timing Diagram for Four Strokes CI Engine
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…
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Port Timing Diagram for Two Strokes SI Engines
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…
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VALVE TIMING DIAGRAMS
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,…
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Comparison Between Otto Cycle and Diesel Cycle
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,…