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.
Why the higher efficiency of the Otto cycle compared to the Diesel cycle for the same compression ratio is not a result of practical importance?
In this case when the compression ratio is the same, more heat can be added in Otto cycle (at almost constant volume) than that of the Diesel (almost at constant pressure), the heat rejected to atmosphere is the same for both cycles , because of that Otto will have better efficiency than Diesel.
Why efficiency of Otto cycle is greater than diesel cycle?
Although for a given compression ratio the Otto cycle has higher efficiency, because the Diesel engine can be operated to higher compression ratio , the engine can actually have higher efficiency than an Otto cycle when both are operated at compression ratios that might be achieved in practice.
What is more efficient Diesel or Otto cycle?
In practice, Diesels are more efficient than Otto engines, because the latter must operate at lower compression ratios to avoid knocking (Section 3.6).
Which cycle efficiency is within Diesel and Otto cycle?
It is found that for a fixed temperature ratio that the efficiency increases with compression ratio for the Otto, Brayton and Diesel cycles until their efficiency is the same as that of the corresponding Carnot cycle . This occurs at the point where the heat input to the cycles is zero.
What is K in Otto cycle?
Thermal Efficiency Derivation
A typical value for an air/fuel mixture is k = 1.35 .
What is ideal Otto cycle?
In the ideal Otto cycle the fuel-air mixture is introduced during the induction stroke and compressed to a much lower compression ratio (around 8:1 ) and is then ignited by a spark. The combustion results in a sudden jump in pressure while the volume remains essentially constant.
Why is the compression ratio of an Otto cycle limited?
Autoignition – Limit for Compression Ratio
The unburned mixture may autoignite by detonating from pressure and heat alone , rather than ignite from the spark plug at exactly the right time. The engine knocking can be reduced by using high-octane fuel, which increases the gasoline’s resistance to autoignition.
What is the difference between Diesel cycle and Otto 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 compression ratio of Diesel cycle?
It operates on either a two-stroke or four-stroke cycle (see figure); however, unlike the spark-ignition gasoline engine, the diesel engine induces only air into the combustion chamber on its intake stroke. Diesel engines are typically constructed with compression ratios in the range 14:1 to 22:1 .
What is diesel cycle process?
The Diesel cycle is a combustion process of a reciprocating internal combustion engine . In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected.
Is a diesel engine a heat engine?
A diesel engine is a type of internal combustion heat engine , powered by diesel. These engines run small electric generators called diesel generators, often in remote areas as well as the engines of cars and trucks (both large and small).
Why diesel engine has higher thermal efficiency?
High Oxygen to Fuel Ratio
The second reason that diesel engines have a higher thermal efficiency than gasoline engines is that of the oxygen to fuel ratio. The greater the amount of air in an air-to-fuel ratio, the cleaner the fuel burns and the more energy it produces.
What is Otto cycle with diagram?
The idealized diagrams of a four-stroke Otto cycle Both diagrams: the intake (A) stroke is performed by an isobaric expansion, followed by an adiabatic compression (B) stroke. ... The cycle is closed by the exhaust (D) stroke, characterized by isochoric cooling and isobaric compression processes.
What is the efficiency of Carnot cycle?
It is well known that the Carnot cycle efficiency ( η thermal = 1 − T L T H ) is maximized with the highest possible heat source temperature T H and the lowest possible heat sink temperature T L .
