发动机工程代写 Introducing The Spark Ignition Si
The phenomena of engine knock continues to provide a limit to the compression ratio and the cylinder pressure of spark ignition engines. Diesel engines have a reputation for sometimes operating nosily and this can be due to knock therefore there is substantial investigation in how to reduce the risk of knock. Generally, it is accepted that engine knock originates from a local, rapid pressure rise; for example, in spark ignition engines, such pressure rise is due to a spontaneous ignition of the unburned gas, or the end gas, ahead of the flame front (Kono, Shiga, Kumagia, Iinuma Year?). Knock is a very serious and sometimes destructive occurrence in the engine, resulting in reduction in engine performance and thermal efficiency. Under certain conditions, knock an cause severe permanent damage to some of the engine components controlling the combustion process (Xudhong Zhen, 2012). There are two generally accepted theories of knock, auto-ignition and detonation. Auto-ignition is the process of the so called end gas reaching its auto ignition point in temperature and pressure. This is caused by the compression by the cylinder head, the walls around it and the propagating burned gas. Detonation theory presumes that knock occurs from the propagating flame front. This acceleration causes a shockwave that reflects from one cylinder wall. The impact pressures have a large magnitude but are only in contact for a short but substantial time, long enough to cause knock to occur (Xudhong Zhen, 2012). A large number of studies have been carried out with respect to the conditions of occurrence of knock and its prevention; however none of them focus on knock intensity. In this area, Draper investigated knock phenomena and concluded his findings as follows:
“1. Knock is accompanied by pressure waves within the cylinder. These pressure waves form standing waves, i.e., resonance phenomena within the cylinder charge.
2. For the cases that the cylinder diameter was over three times the chamber height, the pressure record is due to transverse vibrations”(Kono, Shiga, Kumagia, Iinuma Year?).
From the research done to date it is clear that the two main culprits of engine knock are temperature and pressure within the cylinder.
Computer aided modelling of an engine
The computer modelling software that will be used in this project is from Gamma Technologies, in particular their GT-SUITE. GT-SUITE a virtual engine/power train modelling platform and is used by over 500 business customers worldwide and is the leading engine simulation software provider in the market. (http://www.gtisoft.com/ 13/12/12 15:58) From the GT-SUITE the software I will be using is GT-POWER and GT-POST. GT-POWER is essentially used to build and model any type of engine and then simulate the operation of that engine. The results from this simulation are then sent to the GT-POST program for post processing. The post processing presents all the results that were required from the model and then can place these results instantly in graph format.
Example showing a 4
cylinder, spark ignition
engine modelled in
Taken from Gamma
An example of the types of output graph from GT-POST using the model built and simulated in GT-POWER.
Taken from Gamma Technologies Website (http://www.gtisoft.com/applications/a_SiL_HiL_real_time.php)
Put some of my own graphs from GT POWER in here !!!!! And picture of working model engine my own!!!!!