Study on effect of heat transfer space non-uniformity of combustion chamber components on in-cylinder NOx emission formation in internal combustion engine

The components of combustion chamber (cylinder head-cylinder liner-piston assembly-oil film) were taken as a coupled body.Based on the three-dimensional heat transfer numerical simulation of the coupled body,a coupled three-dimensional calculation model for in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupled method,which implements the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components.The model was applied in the influence investigation of the space non-uniformity in heat transfer among combustion chamber components on the generation of in-cylinder emissions:NOx.The results showed that the heat transfer space non-uniformity of combustion chamber components directly influences the formation of in-cylinder NOx.The main area being influenced was the accessory area on the wall,while the influence on the generation of NOx in the central area couold be omitted.

A New Method for Computing Radiation Heat Flow of In-Cylinder Soot of Diesel Engines

A concise formula for computing radiation heat flow of in-cylinder soot is presented, based on the assumptions that in-cylinder heat transfer of diesel engines is a quasi-equilibrium process and in-cylinder soot particles are spherical. That in this formula there consist neither constants needing adjustments nor variables related to engine types or operating conditions makes it universal and easy to use. Also it can be seen from the formula that radiation heat transfer is proportional to the quotient of in-cylinder soot mass over the average radius of primary particles. Besides, with the help of different algorithms it can be used for predicting cylinders＇ global as well as local radiation heat flows. As a demonstrative application on its global facet, a three-dimension simulation study about the soot-radiation-related heat flow in the combustion chamber of a diesel engine is carried out. Results show that the range of the soot-radiation-related heat flow computed by this formula agrees well with other researcher＇s earlier theoretic reasoning and experimental measurements.

Effects of radiation heat transfer space non-uniformity of combustion chamber components on in-cylinder soot emission formation in diesel engine

Combustion chamber components (cylinder head-cylinder liner-piston assembly-fuel film) were treated as a coupled body. Based on the three-dimensional numerical simulation of heat transfer of the coupled body, the multi-dimensional simulation computation coupling flow and solid on working process and combustion chamber components of internal combustion engine was performed using Discrete Transfer Radiation Model (DTRM) radiation heat transfer model, zoning solution method and boundary coupling method. The simulation was applied to the influence investigation of the space non-uniformity in radiation heat transfer among combustion chamber components on the generation of in-cylinder soot emissions. The results show that the space non-uniformity in heat transfer among the combustion chamber components has great influence on the generation of in-cylinder NOx emissions. The difference value of total soot in cylinder when exhaust valves are opened is 1.3% (no radiation), 0.8% (radiation). So the effect of radiation heat transfer space non-uniformity of combustion chamber components on total soot production can be ignored. While in local area radiation heat transfer space non-uniformity has certain effect on soot production inside whole combustion chamber space, and has less effect on soot production in the area near the wall of combustion chamber components.

Cyclic moving average control approach to cylinder pressure and its experimental validation

Cyclic variability is a factor adversely affecting engine performance. In this paper a cyclic moving average regulation approach to cylinder pressure at top dead center （TDC） is proposed, where the ignition time is adopted as the control input. The dynamics from ignition time to the moving average index is described by ARMA model. With this model, a one-step ahead prediction-based minimum variance controller （MVC） is developed for regulation. The performance of the proposed controller is illustrated by experiments with a commercial car engine and experimental results show that the controller has a reliable effect on index regulation when the engine works under different fuel injection strategies, load changing and throttle opening disturbance.

Technologies and studies of gas exchange in two-stroke aircraft piston engine:A review

The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines,which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder flow characteristics.This paper reviews the development history and characteristics of gas exchange types,as well as the current state of theory and the validation methods of gas exchange technology,while also discusses the trends of cutting-edge technologies in the field.This paper provides a theoretical foundation for the optimization and engineering design of gas exchange systems and,more importantly,points out that the innovation of gas exchange types,the modification of theoretical models,and the technology of variable airflow organization are the key future research directions in this field.

Mutual information of cylinder pressure and combustion phase estimation in spark ignition engines

For the study of internal combustion engines,combustion control is an important method to achieve high efficiency and low emissions.Currently,in-cylinder pressure sensor-based closed-loop control strategies have become the preferred solution.However,their productional application in automotive industries is limited due to the cost of intensive pressure acquisition for a whole cycle and the calculation load of combustion phase indicators.This paper proposes a method of combustion phase estimation for spark ignition(SI)engines.In this method,the combustion phase is estimated only based on pressure measurements at several crank angles.Information entropy and mutual information are introduced to analyze the feasibility and accuracy of the combustion phase estimation,which shows that the pressure measurements at selected points contain most of the information for the estimation.As a result,only pressure measurements at 3 points and ELM estimation models are required to obtain the combustion phase,instead of intensive data acquisition and calculation.

Estimation and feedback control of air-fuel ratio for gasoline engines

In 4-stroke internal combustion engines, air-fuel ratio control is a challenging task due to the rapid changes of engine throttle,especially during transient operation. To improve the transient performance, managing the cycle-to-cycle transient behavior of the mass of the air, the fuel and the burnt gas is a key issue due to the imbalance of cyclic combustion process. This paper address the model-based estimation and control problem for cyclic air-fuel ratio of spark-ignition engines. A discrete-time model of air-fuel ratio is proposed, which represents the cycle-to-cycle transient behavior of in-cylinder state variables under the assumptions of cyclic measurability of the total in-cylinder charge mass, combustion efficiency and the residual gas fraction. With the model,a Kalman filter-based air-fuel ratio estimation algorithm is proposed that enable us to perform a feedback control of air-fuel ratio without using lambda sensor. Finally, experimental validation result is demonstrated to show the effectiveness of proposed estimation and control scheme that is conducted on a full-scaled gasoline engine test bench.

Simple adaptive air-fuel ratio control of a port injection SI engine with a cylinder pressure sensor

The problem of air-fuel ratio(AFR) control of the port injection spark ignition(SI) engine is still of considerable importance because of stringent demands on emission control. In this paper, the static AFR calculation model based on in-cylinder pressure data and on the adaptive AFR control strategy is presented. The model utilises the intake manifold pressure, engine speed, total heat release, and the rapid burn angle, as input variables for the AFR computation. The combustion parameters, total heat release,and rapid burn angle, are calculated from in-cylinder pressure data. This proposed AFR model can be applied to the virtual lambda sensor for the feedback control system. In practical applications, simple adaptive control(SAC) is applied in conjunction with the AFR model for port-injected fuel control. The experimental results show that the proposed model can estimate the AFR, and the accuracy of the estimated value is applicable to the feedback control system. Additionally, the adaptive controller with the AFR model can be applied to regulate the AFR of the port injection SI engine.