Criteria S.I. Engine (Petrol or Spark Ignition Engine) C.I. Engine (Diesel or Compression Ignition Engine) Working Cycle Works on Otto Cycle or Constant Volume Cycle. Works on Diesel Cycle. Mixture During Suction Stroke Takes a mixture of air and petrol during the suction stroke. Takes only air during the suction stroke. Fuel Used Uses petrol as fuel. Uses diesel as fuel. Compression Ratio Has a compression ratio that varies from 6 to 10. Has a compression ratio that varies from 16 to 20. Engine Weight and Cost S.I. engines are lighter and cheaper. C.I. engines are heavier and costlier. Initial Cost Initial cost is lower compared to C.I. engines. Initial cost is high due to high compression ratio. Starting Starting is easy. Starting is difficult, especially in cold conditions. ...
| Water Tube Boiler | Fire Tube Boiler |
|---|---|
| The rate of steam generation is high, up to 450 tonnes/hr | The rate of steam generation is low, up to 9 tonnes/hr |
| It generates steam at high pressure up to 165 bar | It generates steam at low pressure, up to 24.5 bar |
| Its overall efficiency is 90% | Its overall efficiency is 70% |
| Less water is required for steam generation | More water is required for steam generation |
| It is suitable for load fluctuations | It is not suitable for load fluctuations |
| Water flows in tubes which are surrounded by fire | Fire flows in tubes which are surrounded by water |
| Operating cost is high | Operating cost is low |
| Wall thickness is less | Wall thickness is more |
| Cost of installation is high | Cost of installation is low |
| Examples: La-mont boiler, Benson boiler, Loeffler boiler, Babcock and Wilcox boiler, Stirling boiler, Yarrow boiler | Examples: Cochran boiler, Cornish boiler, Lancashire boiler, Locomotive boiler, Scotch Marine boiler, Nestler boiler, Velcon boiler |