Scavenging

A 4-stroke cycle engine may or may not have a pressure boost (supercharger, turbocharger) in the intake system. Why must a 2-stroke cycle engine always have an intake pressure boost?

Explain the effect of delayed charging on IC engine volumetric efficiency.

A diesel engine operating on the 4-stroke cycle is to be designed to operate with the following characteristics where the mean conditions are: $1 \text{ bar}$ and $25^\circ\text{C}$, brake power $= 254 \text{ kW}$, volumetric efficiency $= 0.79$, brake specific fuel consumption $= 0.27 \text{ kg/kW.hr}$, air-fuel ratio $= 17:1$, speed $= 1525 \text{ rpm}$. Calculate the required engine capacity and brake mean effective pressure. Heat of combustion of diesel fuel $= 43000 \text{ kJ/kg}$, $R_a = 287 \text{ J/kg.K}$.

What is the difference between scavenging and supercharging?

Why actual cycle is different from fuel-air cycle?

Calculate the higher heating value of $\text{CH}_4$. Assume the fuel is fully vaporized and bomb calorimeter is used. Standard enthalpies of formation of $\text{CH}_4(\text{g})$, $\text{CO}_2(\text{g})$, $\text{H}_2\text{O}(\text{g})$ and $\text{H}_2\text{O}(\text{l})$ are -74.87 MJ/kmol, -393.52 MJ/kmol, -241.83 MJ/kmol and -285.84 MJ/kmol respectively. Datum temperature $= 25^{\circ}\text{C}$, $\bar{R} = 8314.3 \text{ J/kmol.K}$.

Why idling of SIE requires a rich mixture?

Why higher compression ratio is possible with gasoline direct injection system?

A two-stroke diesel engine of 13 cm bore, 15 cm stroke, compression ratio is 15 is running at 1800 rpm when the following measurements are made: Fuel flow = 7.3 kg/hr, inlet air temperature $= 21^{\circ}\text{C}$, exhaust pressure = 103 kPa, trapped air-fuel ratio = 0.04. Compute the scavenging efficiency.

What is scavenging? Explain the scavenging process with cylinder pressure vs. crank angle diagram.

Why larger engine is more efficient?

How mechanical supercharging process is different from turbocharging?

Why is diesel engine $\text{NO}$2/\text{NO}{\text{x}} decreases with the increase of load?

What is scavenging? How perfect mixing is different from complete short circuiting? When complete short circuiting could happen during the scavenging process?

How CO forms in SI engine combustion? According to Bangladesh vehicular emission standards what is standard value of CO emissions from petro/octane vehicles.

Estimate heat loss of 12 cylinders gasoline engine operating at 600 kW, fuel-air ratio = 0.08, inlet air temperature = 27°C, coolant temperature = 50°C, gas temperature = 400°C. The engine is of 146 mm bore and 146 mm stroke. Brake thermal efficiency = 0.23. Compute heat loss per unit piston area, ratio of heat loss to power, and ratio of heat loss to heat of combustion. Heat of combustion of gasoline fuel = 42 MJ/kg, $\mu_g = 32.5 \times 10^{-6}$ kg/m-sec, $k_g = 51.96 \times 10^{-6}$ kW/m-K.