**Simulation of Combustion Process in Direct Injection Diesel Engine Based on Fuel Injection Characteristics**

Kazimierz Lejda and Paweł Woś *Rzeszów University of Technology Poland* 

## **1. Introduction**

66 Fuel Injection in Automotive Engineering

Xuelong,Miao; Xinqi,Qiao& Xianyong,Wang(2009). *Study on Ultramultihole Nozzle Fuel* 

Combustion engines are still the major propulsion devices for many mechanical equipment including mostly all automotive vehicles. Unfortunately, they negatively affects natural environment due to exhaust gas emission consisting of harmful compounds, like the carbon monoxide CO, unburned hydrocarbons HC, nitric oxides NO and NO2 (altogether marked as NOX), solid particles PM, and finally the carbon dioxide CO2, that is to blame for the global warming phenomenon. All of them may cause human health deterioration or unwanted changes in the atmosphere in a large scale. As the examples, formation of the photochemical smog where hydrocarbons and oxides of nitrogen play the main role, or destruction of the ozone protective layer with participation of nitric oxide can be pointed here. There are also many other compounds in the exhaust gases which, besides their ecotoxicity, show also a serious carcinogenic action against people and animals, e.g. some hydrocarbons and particulate matter fractions.

The prevention-natured, legislative limitations of vehicle exhaust emission stemmed from these threats, together with the current and prospective growth of road transportation intensity, calls for continuous effort to develop vehicle powertrains that must be done both in design and technology domains. Hence the combustion engine improvement works have been spreading out within the space of last decades, and now they consider more and more factors. They pursue a simultaneous decreasing of harmful exhaust emission (CO, HC, NOX, PM) and fuel consumption. Particularly, the thing is to cut down on CO2 emission by increasing engine total efficiency. Fulfilling all above tasks encounters many problems. They contradict each other, what originates from complex physical and chemical interactions during the working cycle of piston engines, especially at combustion stage, where many phenomena combine together in the same time and area. For example, in direct injection engines simultaneously occurs: injection, fuel atomization and vaporization, induction of ignition or autoignition, fuel burning and many other chemical processes. All it takes only a few milliseconds. That is why improving exhaust emission parameters usually claims resignation from good fuel efficiency, and vice versa, fuel consumption decreasing escalates harmful emission. Hence, it is necessary to perform a lot experimental research in order to find an optimal solution. Unfortunately, they are generally complicated and expensive, but they could be successfully supported by numerical simulation. By the way, computational

Simulation of Combustion Process



**3. Demonstration of combustion model** 

2. considering a number of recognized zones, we have:

more precise model should be worked out instead.

(Rychter & Teodorczyk, 1990):



1. considering dimensions, we have:

engine operation.


cylinder.

in Direct Injection Diesel Engine Based on Fuel Injection Characteristics 69

Presently, the pressure-accumulative fuel systems with electronically controlled injectors are widely used, e.g. Diesel common rail (CR) one. In such systems, the injection rate essentially depends on two parameters: the shape of electrical signals in the injector and the hydraulicmechanical characteristic of the injector. The change of pressure in the fuel storage is so small and affects fuel injection rate so little that it can be neglected in simulation works on

The fuel spray characteristics may be described by the following parameters:



Preparation of flammable mixture in a direct injection engine becomes involved not only with strategy of fuel delivery, but also with areal distribution of fuel in the cylinder space. It should be noticed that a lot of factors influencing the fuel injection rate also plays an important role in fuel atomization quality, resulting in fuel mixing with air inside the

All mathematical models of combustion engine working cycle can be sorted as follows

Above segmentation defines a model complexity and fidelity in representation of real processes in the model. It is also connected with complication in mathematical tools used for simulation. There are a lot of examples which combines the models according to the above segmentation (Khan et. al., 1973; Patterson, 1994, 1997; Rychter & Teodorczyk, 1990). The fundamental problem in choosing a proper type of the model is to find a compromise between accuracy and intellectual labor involved to describe all physical phenomena. A priority here is the goal of analysis. As a rule, for comparative and/or quantitative research, a simplified model can be used with receiving good results; for qualitative investigations

In a preliminary analysis toward model formulating, a number of physical and chemical processes that occur during the injection, combustion and exhaust pollutant formation were taken into consideration. The latest theoretical and experimental results were regarded. A great effort was made to include to the analysis all phenomena that have a major impact on the various processes modeled, so as their actual nature would be reproduced. Thanks to

methods allow boundary-free analyzing and may narrow the range of further experiments. They are also much more time and cost-efficient than test bed investigations.

Fuel injection in combustion engines belongs to the most important working processes. Particularly, in direct injection (DI) engines, both gasoline and diesel one, it truly triggers and controls combustion, influencing all output engine performances together with exhaust emissions. Thus, improving of combustion engines should always consider fuel injection optimization, before other kinds of engine processes are being tested. Techniques harnessing mathematical simulations are the good ways to do this in the first stage. Such approach will be shown further.
