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BITAC Assistant Engineer Mechanical Exam Questions and Solutions 2023

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In this exam there was total 40 questions. The questions and possible solutions are given below.  1. Draw stress strain diagram of mild steel 2. What are the factors that affects thermal comfort? Factors that affects thermal comfort: 1. Temperature: The ambient temperature plays a significant role. It should be within a range that suits individual preferences and the specific activity being performed. 2. Humidity: High humidity can make a space feel warmer, while low humidity can lead to dryness and discomfort. Maintaining optimal humidity levels is crucial. 3. Air Velocity: The speed of air movement can impact how we perceive temperature. Proper ventilation and air distribution help maintain comfort. 4. Clothing: The type and amount of clothing worn affect an individual's thermal comfort. Dress code and personal attire should align with the indoor climate. 5. Metabolic Rate: The level of physical activity influences how much heat our bodies generate. Spaces with varying activity l

Cutoff Ratio and Compression Ratio of Engines

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Cutoff ratio The term ' cut-off ratio'  applies specifically to diesel engines and does not pertain to petrol engines. In petrol engines, there is no cut-off. Cut-off refers to the cessation of fuel spray, which occurs in diesel engines but not in petrol engines. Therefore, this term is exclusive to diesel engines. Please note the PV diagram of the diesel cycle below. Air is isentropically compressed in process 1-2. Once the compression process is complete, the fuel spray initiates at point 2. With the onset of the fuel spray, combustion begins, leading to gas expansion. This spray and combustion phase continues until point 3, representing the gas expansion from point 2 to point 3. At this stage, V3/V2 equals the cutoff ratio, where V3 represents the volume at point 3, and V2 represents the volume at point 2. A potential question may arise: why does the fuel spray organize combustion? The answer lies in the fact that the compression of air during process 1-2 elevates its temper