These assumptions are: (1)The working fluid is air, which continuously circulates in a closed loop and always behaves as an ideal gas. (2) All the processes are internally reversible . (3)The combustion process is replaced by a heat addition process. (4)The exhaust process is replaced by a heat rejection process.
What are the assumptions for air standard cycles?
- The working fluid is assumed to be a perfect gas.
- There is no change in the mass of the working medium.
- All the process that constitutes the cycle is reversible.
- Heat is assumed to be supplied from a constant high-temperature source and not from chemical reaction during the cycle.
What is cold standard?
Cold-Air-Standard Assumption – Used to simplify the analysis of gas cycles . Includes all of the air-standard assumptions in addition to the assumption that the working fluid (air) has constant specific heats.
Which of the following is NOT assumption of air standard cycle?
Which one of the following is NOT a necessary assumption for the air-standard Otto cycle? All processes are both internally as well as externally reversible. Intake and exhaust processes are constant volume heat rejection processes . The combustion process is a constant volume heat addition process.
What is the difference between air standard assumptions and the cold air standard assumptions?
♨Along with all the above assumptions, taking constant specific heats at room temperature, at 25 C for air, is called cold air standard assumptions. ✔ Assuming constant specific heats at room temperature 25 C for air is only the difference between air standard assumptions and cold-air standard assumptions.
Which is more efficient Otto or Diesel?
Explanation: Otto cycle is more efficient than Diesel cycle for a given compression ratio. ... For constant maximum pressure and heat input, the air standard efficiency of the gas power cycle is in the order.
Which is the wrong assumptions for calculation of air standard efficiency?
All processes are reversible. Specific heat remains constant at all temperatures . No account of the mechanism of heat transfer is considered. Gases dissociate at higher temperatures.
What is a standard efficiency?
Air standard efficiency is taken as the ideal efficiency of an internal combustion engine . ... (a) No transfer of heat between the working surfaces and the air (b) Instantaneous and complete combustion (C) No change in volume during the combustion (constant volume) (d) Specific heat capacity is assumed to be constant.
What are the air standard assumptions in thermodynamic heat engines?
9-6C The air standard assumptions are: (1) the working fluid is air which behaves as an ideal gas, (2) all the processes are internally reversible, (3) the combustion process is replaced by the heat addition process , and (4) the exhaust process is replaced by the heat rejection process which returns the working fluid ...
What is auto cycle and diesel cycle?
Otto cycle is used for petrol or spark ignition engine while diesel cycle is used for diesel or compression ignition engine . The main difference between Otto cycle and Diesel cycle is that in Otto cycle heat addition takes place at constant volume and in diesel cycle heat addition takes places at constant pressure.
What is the air standard cycle?
The air-standard cycle is an idealized cycle founded on the following approximations: (1) The working fluid throughout the cycle is only air; (2) the air acts as an ideal gas; (3) combustion processes are replaced by well-defined heat addition processes; and (4) the exhaust process is replaced by a heat rejection ...
Is a assumption made in Carnot cycle?
Assumptions of Carnot Cycle
While proposing the processes, Carnot made certain assumptions as given below: There is no friction at all between the piston and cylinder and other moving parts of the engine , thus there is no heat generated and lost due to friction.
What is back work ratio?
Back Work Ratio: the ratio of the compressor work to the turbine work . Open Cycle Gas Turbine Engines.
What is cut off in diesel cycle?
9-53C Cutoff ratio is the ratio of the cylinder volumes after and before the combustion process . As the cutoff ratio decreases, the efficiency of the diesel cycle increases. ... The cycle is to be shown on P-vand T-s diagrams, and the net work output and the thermal efficiency are to be determined.
What is the difference between Rankine cycle and Brayton cycle?
Rankine cycle is a steam engine, the water is boiled, evaporated, used for work and then condensed for re-use, thus making it a closed cycle. ... The working fluid undergoes a phase change in the Rankine cycle whereas in Brayton cycle there is no phase change the working fluid always remains in the gaseous phase.
What is diesel cycle efficiency?
A typical diesel automotive engine operates at around 30% to 35% of thermal efficiency . About 65-70% is rejected as waste heat without being converted into useful work, i.e. work delivered to wheels. In general, engines using the Diesel cycle are usually more efficient, than engines using the Otto cycle.
