Which cycle is the most efficient of these for the same compression ratio?
Explanation: Otto cycle is more efficient than Diesel cycle for a given compression ratio. 6. For constant maximum pressure and heat input, the air standard efficiency of the gas power cycle is in the order.
How does the ideal diesel cycle differ from the ideal Otto cycle?
The most significant difference between the ideal Otto cycle and the ideal Diesel cycle is the method of igniting the fuel-air mixture. The fuel is then injected such that the ignition process occurs at a constant pressure.
How is the heat rejected in the diesel cycle?
Heat rejection process is isochoric process. Explanation: Diesel cycle consist of one isobaric process, one isochoric process and two adiabatic process. Heat rejection process is isobaric process. The thermal efficiency of diesel cycle having fixed cut-off ratio, with increase in compression ratio.
What are the air standard assumptions?
The following assumptions are commonly known as the air- standard assumptions: 1- The working fluid is air, which continuously circulates in a closed loop (cycle). Air is considered as ideal gas. 2- All the processes in (ideal) power cycles are internally reversible.
What is the difference between air standard assumptions and 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.
What are actual cycles?
The actual cycle experienced by internal combustion engines is an open cycle with changing composition, actual cycle efficiency is much lower than the air standard efficiency due to various losses occurring in the actual engine. Whereas, in actual cycle, burning is completed in a definite interval of time.
What is the difference between ideal and actual cycle?
The difference is that ideal is a plan where we want to approach or it is a direction towards which we have to move and actual is the observed when our engine is in working condition. the efficiency shown by ideal is 100% but the actual is less than it.
What is ideal cycle?
Ideal cycles are simplified thermodynamic closed cycles to analyze the compression, combustion, and expansion process in an engine with a focus on extraction of work from combustion of the fuel–air mixture.
What is ideal cycle efficiency?
Thus, the efficiency increases with the compression ratio. However the compression ratio of Otto cycle engines is limited by the need to prevent the uncontrolled combustion known as knocking. Modern engines have compression ratios in the range 8 to 11, resulting in ideal cycle efficiencies of 56% to 61%.
How do you increase the thermal efficiency of Brayton cycle?
In general, increasing the pressure ratio is the most direct way to increase the overall thermal efficiency of a Brayton cycle, because the cycle approaches the Carnot cycle. According to Carnot’s principle higher efficiencies can be attained by increasing the temperature of the gas.
What are the factors that affect thermal efficiency?
Factors analysis of thermal efficiency The key factors affecting the boiler heat loss and efficiency are superheating surface area, excess air coefficient, inlet gas and exhaust gas temperature, etc.
What are the factors of thermal efficiency?
The thermal efficiency of a heat engine is expressed as a product of the Carnot efficiency, the external irreversibility factor and the internal irreversibility factor, by which the three factors that affect the thermal efficiency can be clearly distinguished, and the influences of the external and internal …
Which engine has more thermal efficiency?
Real diesel engines are of course considered to be more efficient that Otto cycle engines; one reason being that diesel engines typically operate at higher compression ratio and the expansion ratio from even the later stages of heat release can still be considerably higher than that of most real Otto cycle engines.