Tutorial 4 Internal Combustion Engines

The question marked with an asterisk (*) will be graded.

*1. A small truck has a 4-cylinder, 4 litre CI engine operating on the air-standard dual cycle as shown. The heat qm provided externally per cycle to each cylinder is from the combustion of 0.05g of light diesel fuel with LHV 42500 kJ/kg. The compression ratio of the engine is 15:1 and the cylinder bore is 100mm. At the start of the compression stroke, conditions in the cylinder are 600C and 100kPa. It can be assumed that half of the heat input from combustion is added at constant volume and half at constant pressure. Calculate:

(a) temperature and pressure at each characteristic state of the cycle (b) net work of the cycle (c) thermal (indicated) efficiency of the cycle

2. At the beginning of the compression process of an air-standard Diesel cycle operating with a compression ratio of 18, the temperature is 300K, the pressure is 0.1MPa and 1917cm3. The cutoff ratio for the cycle is 2. Determine

(a) the temperature and pressure at the end of each process of the cycle (b) the thermal efficiency and (c) the mean effective pressure, in MPa

Note: the cutoff ratio is defined as the ratio between the volume at the end of heat addition to the volume at the beginning of heat addition in the Diesel cycle

3. A gas engine working on the Otto cycle has a cylinder bore of 200mm and stroke length of 250mm. The clearance volume is 1570cc. The pressure and temperature at the beginning of compression are 1 bar and 270C respectively. The maximum temperature of the cycle is 14000C. Determine

(a) the pressure and temperature at the end of each process in the cycle, (b) the thermal efficiency, (c) the work done and (d) the mean effective pressure

Given Cv=0.718 kJ/kg.K, R= 0.287 kJ/kg.K

4.