The ignition delay period is also called the preparatory phase during which some fuel has already been admitted but has not yet ignited. This period is counted from the start of injection to the point where the pressure-time curve separates from the monitoring curve indicated as start of combustion.
What is delay period in engine?
Abstract The ignition delay in a diesel engine is defined as the time interval between the start of injection and the start of combustion. This delay period consists of (a) physical delay, wherein atomisation, vaporization and mixing of air fuel occur and (b) of chemical delay attributed to pre-combustion reactions.
What is delay period and what are factor affect it?
I C ENGINES – II Air Motion & Combustion •Factors Affecting the Delay Period : – Intake temperature and pressure : Increase in intake temp. increases compressed air temp. resulting in reduced delay period. Preheating may not be desirable as it reduces density of air affecting volumetric efficiency and power.
Is ignition lag and delay period same?
Ignition lag (the time lag between first ignition of fuel and the commencement of the main phase of combustion) is not a period of inactivity but is a chemical process. The ignition lag in terms of crank angles is 10° to 20° and in terms of time, 0.0015 seconds.
Is ignition delay good or bad?
The shorter ignition delay affects the combustion performance of an engine. Ignition delay of the CI engine fuel is inversely proportional to its cetane number. Hence, optimization of ignition delay will improve the performance of the engine.
Which is the best option to avoid knock in SI engine?
To prevent knock in SI engine the end gas should have low temperature, pressure and density, a long ignition delay and a non-reactive composition.
What causes ignition delay?
Rapid ignition of some premixed fuel and air occurs after the ignition delay period. … It also increases the evaporation rate of the remaining fuel. Atomization, vaporization, fuel vapor-air mixing, and combustion continue until all the injected fuel has combusted.
What is the importance of ignition delay?
The shorter the ignition delay time, the smoother is the jet engine start and softer is the diesel engine run. The reason for this is that at shorter ignition delay time the fuel burns near the injector and new portions of the fuel enter the mixture of air with the combustion products rather than the hot air zone.
Which factors increase knocking in SI?
Factors affecting Detonation or Knocking in SI engine:
- Compression ratio: The pressure and temperature at the end of compression increases with increase in compression ratio. …
- Supercharging: …
- Increasing inlet temperature: …
- Increase in load: …
- Advancing the spark: …
- Flame travel distance: …
- Spark plug location: …
- Engine size:
How can periods delay?
Missed or late periods happen for many reasons other than pregnancy. Common causes can range from hormonal imbalances to serious medical conditions. There are also two times in a woman’s life when it’s totally normal for her period to be irregular: when it first begins, and when menopause starts.
How do you reduce ignition delay?
Hence, if n 2 is somewhat increased prior to the fuel being exposed to oxygen, the observed ignition delay, τ, should decrease. According to the two energy level system, τ can be decreased simply by increasing the fuel temperature prior to injecting or exposing the fuel to oxygen.
How do you check ignition delay?
Ignition delay is calculated as the period from the start of injection to the start of combustion in terms of the crank angle. The ignition delay for diesel, B10, B20, and B100 were 14.94, 14.67, 14.44, and 13.54°CA, respectively, at the rated power output.
What is injection delay?
The injection delay (a) refers to the period between the start activate high volt to solenoid energizing (SOE) and the start of injection (SOI) where the negative value of injection rate returns to zero (Han et al., 2014).
What is ignition delay how it affects the combustion process in SI engine?
Ignition lag stage:
An ignition lag of 0.002 seconds corresponds to 35 deg crank rotation when the engine is running at 3000 RPM. Angle of advance increase with the speed. This is a chemical process depending upon the nature of fuel, temperature and pressure, proportions of exhaust gas and rate of oxidation or burning.
What is delay period in thermal engineering?
Explanation: Delay period is defined as the time immediately following injection of the fuel during which the ignition process is being initiated and the pressure does not rise beyond the value it would have due to compression of air.