tóm tắt tiếng anh: Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.

Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.Tự động điều chỉnh hệ số tương đương và góc đánh lửa sớm để nâng cao hiệu quả công tác của động cơ BiogasHydrogen.

THE UNIVERSITY OF DANANG UNIVERSITY OF SCIENCE AND TECHNOLOGY

BUI VAN HUNG

AUTOMATIC CONTROL OF EQUIVALENCE RATIO AND ADVANCE IGNITION ANGLE TO IMPROVE THE PERFORMANCE OF BIOGAS-HYDROGEN ENGINE

Major : Mechanical Powertrain Engineering

Code : 9520116

SUMMARY OF DOCTORAL THESIS

Danang, 2023

The thesis is completed at:

UNIVERSITY OF SCIENCE AND TECHNOLOGY

Science instructor : 1 Prof DSc Bui Van Ga

2 Assoc.Prof Dr Bui Thi Minh Tu

This thesis can be found at:

- National Library of Vietnam

- Learning Resources and Communication Center, University of

science and technology- The University of Danang

INTRODUCTION

1 RATIONALE OF THE STUDY

Raw biogas contains mainly methane (CH4) and impurities carbon dioxide (CO2), so its calorific value is lower than natural gas Although CO2 in biogas and syngas reduces pollutant emissions, this impurity tends to increase combustion delay time and reduce flame propagation speed, so it will reduce engine thermal efficiency Enrichment of biogas, with hydrogen (H2) is an effective solution to solve this problem However, H2 can cause undesirable results such as increased NOx emissions because of its high combustion temperature and reduced thermal efficiency due to heat loss Mixing a moderate ratio of H2 into biogas and will improve the performance of the engine while not increasing pollutant emissions

Most components are available on the market today for assembling a hybrid renewable energy system, with the exception of the internal combustion engine that pulls the generator in accordance with the requirements of the system Internal combustion engines are designed to work with a given fuel type and under defined operating conditions In a hybrid renewable energy system, the fuel composition changes frequently according to the input materials and the source of hydrogen provided by solar power On the other hand, the load mode

of the motor also changes frequently to provide a compensating load for the system Therefore, the engine must be flexibly adjusted to the operating parameters, especially the ignition advance angle and the equivalence ratio of the mixture Traditional stationary motors can hardly meet this requirement

The thesis focuses on dealing with two main problems of the

engine in the hybrid renewable energy system, that is, controlling the fuel supply process and adjusting the optimal advance ignition angle

2 RESEARCH OBJECTIVES

Converting a stationary engine supplying gasoline by a carburetor to a stationary engine that injects fuel and automatically adjusts the advance ignition angle according to the fuel composition and operating mode in the hybrid renewable energy system: biomass-solar energy

3 OBJECT AND SCOPE OF THE STUDY

Research object: Converting the traditional stationary engine

supplying gasoline by carburetor into a stationary engine that electronically controls the fuel injection process and the advance ignition angle according to the fuel composition and operating mode

in the hybrid renewable energy system: biomass-solar

Research scope:

- Renovating a gasoline engine using a traditional carburetor into an electronically controlled stationary engine with variable speed within a narrow range corresponding to the working conditions of the stationary engine

- Experimentally evaluate the technical performance and pollutant emission level of the engine at a certain number of points on the speed regulation curve with the specified fuel composition

- Simulation is performed in many working modes and many fuel components to expand the research results

4 RESEARCH METHODS

Combination of theoretical research, simulation and experiment

- Theoretical: focus on studying the basis of the entangled

combustion process of the gas-fuel mixture, the basis of pollutant formation, focusing on analyzing the influence of the biogas-hydrogen fuel mixture composition on the performance engine performance and pollutant emission level

- Simulation: Using ANSYS FLUENT software to simulate the fuel

supply and combustion process of engines running on hydrogen fuel mixture On the fuel supply process, the focus is on analyzing the effects of the pre-mixed biogas-hydrogen fuel supply technique and the separate (dual) biogas/hydrogen fuel supply Regarding the combustion process, focus on simulating the influence

biogas-of mixture composition and advance igntion angle on the technical features and pollution emission level of the engine

- Experimental: Implemented the improvement of stationary

gasoline engine, fueled by carburetor into a gas fuel injection and electronically controlled ignition engine, specifically building a fuel supply diagram biogas-hydrogen fuel on the speed regulation curve and design an electronic control circuit to perform the fuel supply and adjust the optimal advance igntion angle according to the engine's working mode Conduct experimental measurements of the engine's power and pollutant emissions in some specified working

modes and fuel compositions to evaluate simulation results

5 SCIENTIFIC AND PRACTICALITY SIGNIFICANCE OF THE THESIS

Scientific significance: Conventional stationary engines are

typically designed to use a specific type of fuel, so they are not suitable when operating under variable fuel conditions The study of flexibly

adjusting the fuel supply process and the advance ignition angle of the spark ignition stationary engine according to the fuel composition and operating conditions has scientific significance not only for the renewable energy system but also for the renewable energy system hybrid generation but also for the development of flexible gas-fueled engines

Practical significance: Our country is in the tropics,

agricultural production should have great potential for biomass and solar energy The combination of using these two energy sources in a hybrid renewable energy system will overcome the shortcomings of using a single renewable energy source Static engines using biogas-hydrogen play an important role in hybrid renewable energy systems

It replaces complex and expensive energy storage equipment Therefore, the research and development of stationary engines using flexible gaseous fuels will create conditions for the widespread development of renewable energy applications It is one of the practical solutions contributing to the implementation of the Net Zero

strategic goals that our country has committed to the world

6 STRUCTURE OF RESEARCH CONTENTS

The thesis's table of contents, in addition to the introduction, conclusion and development direction of the thesis, the main content

is presented in 4 chapters with the following structure:

Chapter 1: Overview of the research problem

Chapter 2: Theoretical basis of the process of creating mixtures and combustion in the SI engine

Chapter 3: Simulation of mixture creation and combustion in the biogas-hydrogen injection engines

Chapter 4: Experimental research and evaluation of simulation results

7 NEW CONTRIBUTION OF THE THESIS

- Converting a spark ignition stationary engine fueled with gasoline into port injection biogas-hydrogen engine with an appropriate electronic control unit

- Determine the biogas-hydrogen hybrid fuel composition to achieve the harmonization of technical features and pollution emission level of the engine

- Construction fuel injection diagram and engine ignition diagram using biogas-hydrogen fuel

- Control the fuel injection process and the advance igntion angle according to the fuel composition and working mode of the engine

to improve the working efficiency of the biogas-hydrogen engine

- Design and manufacture of an ECU for flexible gas-fueled engine, contributing to the development of a biomass-solar hybrid renewable energy system

Chapter 1: OVERVIEW

1.1 Global energy structure in the "Net Zero" strategy

1.2 Hybrid renewable energy system

1.3 Hybrid renewable energy system biomass - solar energy 1.4 Effect of hydrogen on engine performance

1.5 Conclusion

- To limit the increase in atmosphere temperature, we must reduce emissions of greenhouse gases, especially CO2 emissions Gradually reducing the use of fossil fuels and replacing them with

renewable fuels helps us to keep the CO2 concentration in the atmosphere today, maintaining the habitat on the planet

- Renewable energy is generally unstable and depends a lot on weather and environmental conditions

- Biogas is produced from agricultural or livestock waste with the main components being CH4 and CO2 Syngas from biomass gasification contains CO, CH4, H2 and impurities CO2, N2 The presence of CO2, N2 in these fuels reduces the calorific value and combustion rate of the fuel, which affects the performance and emission of pollutants of the engine However, they have a high octane rating, so they can be used in sparking engines with high compression ratios

- Hydrogen can be produced from water through electrolysis by solar electricity Hydrogen is also present in syngas from biomass gasification Hydrogen has a burning speed 10 times higher than methane, so it is a very good additive to improve the combustion performance of biogas

- In a hybrid renewable energy system, the biogas/hydrogen fuel composition changes frequently The motor's load mode also changes to provide compensatory power to the system As a result, the advance ignition angle and fuel/air ratio also change Therefore, the engine control system must be flexible to ensure that the engine can work efficiently in a renewable energy system

From the above conclusions, this thesis focuses on researching solutions to adjust the advance ignition angle and equivalence coefficient of stationary engines running on poor gas fuel

supplemented with hydrogen

Chapter 2: THEORETICAL BASIS OF THE PROCESS OF CREATING MIXTURES AND COMBUSTION IN THE SI ENGINE

2.1 Basic system of equations

2.2 Model of turbulent

2.3 Model of the combustion

2.3.1 Calculation of quantities of combustion

2.3.1.1 Mixed ingredients

2.3.1.2 Probability Density Function (fdp)

2.3.1.3 Function of the dependent variable ϕ(f)

2.3.2 Determine the flame membrane

Combustion takes place in a thin flame film The flame film spread is modeled by solving the transport equation for the mean reaction evolution variable, denoted c:

2.3.3 Laminar flow rate

2.3.3.1 Analysis of flame film spreading rate components

Assume that the unburnt gas is subjected to adiabatic compression, u

u

p=C (p: pressure in the combustion chamber), the

basic combustion rate can be calculated in terms of pressure p:

b o b n

2.3.3.2 Experimental formulas for laminar melting rate

The basic combustion rate depends on temperature and pressure

as suggested by Meghalchi and Keck

S n = S n,o T (2.62)

Iijima and Takedo [204] suggest the following general expression

𝑆𝑛 = 𝑆𝑛,𝑜𝑇𝛼(1 + 𝛽𝑙𝑜𝑔10𝑝) (2.65)

2.3.4 Turbulent flame speed

In FLUENT, the turbulent flame film speed is calculated based

on the model of the wrinkle as well as the flame film thickness [196]:

a series of chemical reactions

- In order to simplify the reaction problem in turbulent media, scientists have come up with suitable combustion models for the interaction between the fuel and the oxidant Two basic models are combustion of heterogeneous mixtures and combustion of homogeneous mixtures For engines using hybrid fuel, the locally homogeneous combustion model is suitable for the nature of the

fuel supply process

- The homogeneous combustion model is an intermediate model between the combustion of a heterogeneous mixture and the combustion of a homogeneous mixture The combustion process is represented through two conserved quantities, that is, the mixture composition f and the process of combustion c The position of the flame film and the characteristic parameters of the combustion process can be determined through these two parameters In calculating the combustion process of biogas-petrol hybrid fuel presented in the next chapter, we use the local homogeneous combustion model

- The basic parameter to calculate the combustion process of the mixed mixture is the laminar melting rate This parameter depends

pre-on the fuel compositipre-on as well as the pressure and temperature

conditions in the combustion chamber

Chapter 3: SIMULATION OF MIXTURE CREATION AND COMBUSTION IN THE BIOGAS-HYDROGEN INJECTION ENGINES

3.1 Model setting

3.1.1 Computing space and meshing

3.1.2 Simulation execution sequence

3.2 Simulation of the engine's mixing process

3.2.1 Progress of intake

3.2.2 Effect of nozzle diameter and injection pressure

Figure 3.17 shows the simulation results of the mixture formation process when injecting the M6C4-30H fuel mixture through

a nozzle with a diameter of dp=5.5mm, injection pressure of 0.5bar

With the same engine speed of 3600 rpm, to achieve the equivalence ratio =1, the injection time is 81°CA At the end of the intake stroke, most of the fuel is sucked into the cylinder The advantage of the 5.5mm diameter nozzle is that the injection pressure is only 0.5bar, which is convenient for the fuel supply process

Figure 3.17: The process of creating the mixture when injecting M6C4-30H fuel through the injector with, p p =0,5bar, φ p =81°TK,

n=3600rpm

3.2.3 Effect of hydrogen content

3.2.5 Effect of throttle opening

3.2.6 Diagram of fuel injection biogas-hydrogen

With biogas with a given CH4 content, the injection time increases very slightly with the hydrogen content in the fuel mixture (Figure 3.27) However, with a given hydrogen content in the fuel mixture, the injection time increases very quickly when the CH4

content in the biogas decreases Therefore, to simplify the control system, we only need to establish the relationship between injection time and CH4 composition in biogas

-0,4 0 0,4 0,8 1,2 1,6 2

-0,008 0 0,008 0,016 0,024 0,032 0,04



Figure 3.27: Diagram of injection of biogas-hydrogen fuel mixture (nozzle d p =5,5mm, p p =0,5 bar, a = 0°, n=3000 rpm)

3.3 Simulation of engine combustion and pollutant emissions

3.3.1 Effect of advance igntion angle

Figure 3.33: Comparison of the influence of advance ignition angle

on the characteristic parameters of the combustion process when the engine runs on biogas M7C3 (a) and M8C2-40H (b) at 3600rpm, =1

Figure 3.33a and Figure 3.33b compare and summarize the effects of advance ignition angle on the characteristic parameters of the combustion process when the engine runs on biogas M7C3 and M8C2-40H at 3600 rpm with similar coefficients equals =1 We see that the rule of influence of advance ignition angle on the characteristic quantities of the combustion process in the case of biogas-powered

50 4

t inj

engines as well as when running on biogas is similar With any fuel supply conditions, when increasing the advance ignition angle, the exhaust gas temperature tends to decrease slightly because the heat release rate increases, reducing the amount of combustible mixture on the expansion line; HC only increased very slightly while CO decreased

3.3.2 The effect of the equivalence ratio

Figure 3.36: Effect of mixture composition on the graph of work (a)

and combustion temperature (b)

Figure 3.37: Effect of equivalence ratio on CO (a)

and NO x (b) emissions (b)

Figure 3.36a introduces the effect of the equivalence ratio on the work graph of the engine when running on biogas M8C2 at 3000 rpm We see that the maximum area of work graph is achieved when

 is slightly larger than 1 Corresponding to that value of the equivalence coefficient, the maximum temperature and exhaust temperature also reach the highest values (Figure 3.36b) When the