Analysis of an Automatic Control System for Online Blending of Petrol With Corrosion Inhibitor in the Direct Continuous Electronic Fuel Injection Automobile Engine
Chapter One
OBJECTIVE OF THE WORK
Following the earlier discussion, the objective of this work is to design an automatic feedback control system which enables the blending of petrol with a specific quantity of corrosion inhibitor, in the direct, continuous electronic fuel injection automobile engine. In order to realise this objective, the control system shall ensure that the composition of the mixture of petrol and corrosion inhibitor remains constant, regardless of any variation in the flow velocity of the petrol which is supplied to the automobile engine.
CHAPTER TWO
LITERATURE REVIEW
Considering that the scope of this work encompasses different aspects of process control engineering, it is necessary to conceptualise some of the technical terms which are extensively used in this report.
PETROLEUM REFINING
Petroleum is the term used for a group of hydrocarbon-rich fluids that have accumulated in subterranean reservoirs as fossil fuel. It is a naturally occurring mixture of hydrocarbons, generally in a liquid state, which may also include metals and some compounds of sulphur, nitrogen, oxygen, among others. Petroleum, also known as crude oil, is widely varied in its composition and properties: with regard to the field and depth from which it is explored. It contains thousands of different compounds that vary in molecular weight, from 16 (for methane, CH4) to more than 200 (for diesel and lubricating oil).
In its raw form, crude oil has little value. Value is added to crude oil by a refining process. The refining of crude oil involves three main processes: product separation (by fractional distillation), product conversion (by cracking) and product finishing (by isomerisation and reforming). The major distillation fractions of crude oil are the light distillates (refinery gas, naphtha, petrol, aviation fuel, kerosene), the middle distillates (diesel fuel, fuel oil, mineral oil, lubricating oil), and the heavy distillates (grease, wax, asphalt and coke). However, among the different fractions of crude oil distillation, petrol and kerosene rank the greatest in volume of production and market share.
PETROL ADULTERATION
Adulteration is the introduction of illegal and unauthorized substance(s) into a product, with the result that the product does not conform to specified standards. According to Mathur (2014), when petrol is adulterated, the mixture/solution formed is not usually uniform. And, since the adulterated petrol contains a different composition of the fuel elements (carbon and hydrogen), the combustion process in the automobile engine will be incomplete. Incomplete combustion of petrol (and other fuels) lowers the adiabatic flame temperature of combustion reactions, which results in a reduction of the engine power output.
PETROL ADDITIVES
Petrol additives are chemical compounds which are added to petrol in order to improve the petrol quality. Petrol additives are of different types, depending on their functions. Typical examples of petrol additives are corrosion inhibitors, antioxidants (used as stabilisers), antiknock agents (such as tetramethyl lead, ferocene, iso-octane, toulene), lead scavengers (like dichloroethane, dibromoethane), fuel dyes (used for product differenciation), ethers (used as starting fluid for difficult-to-start engines), nitrous oxide (used as oxidiser for auto-racing), and picrate (used to improve engine combustion and increase fuel mileage).
AUTOMOBILE ENGINES
Automobile enginesare internal combustion engines which are designed to convert chemical energy (in fuels) to mechanical energy in moving vehicles. There are different classifications of automobile engines, based on:
- Fuel Type: petrol engines, diesel engines, kerosene engines
- Fuel-Supply System: carburettor engines, injector engines
- Engine Cylinder Arrangement: inline engines, vee engines, etc
- Number of Cylinders: two-, four-, six-, eight-, twelve-cylinder engines
- Engine Cylinder Capacity: 1.8-, 2.0-, 2.2-, 3.0-, 4.0-litre capacity engines, etc
- Engine Ignition System: Spark Ignition and Compression Ignition engines
Fuel Injection Systems
Fuel supply by injection is a process in which a measured quantity of fuel is forcibly sprayed into the cylinderof an automobile engine in order that thefuel is atomised, and proportionately mixed with the air which enters the engine cylinder. Fuel injection systems are classified as follows:
- Mechanical Fuel Injection (MFI) System
- Electronic Fuel Injection (EFI) System
- Indirect Injection System
- Direct Injection System
The MFI system uses both an engine-driven injector pump and an electric fuel pump. The electric fuel pump forces the petrol in the petrol tank, through a filter, into the injector pump. However, in the EFI system, there is no injector pump attached to the engine. The EFI relies entirely on the electric fuel pump in the petrol tank to provide the needed pressure in the fuel pipe line.
There are two types of the EFI system: continuous EFI system and discontinuous EFI system. Unlike the discontinuous electronic fuel injection system which supplies fuel to the engine in short pulses of varying duration (though the flow rate remains constant during each pulse); the continuous fuel injection system supplies fuel to the engine at all times, but with a varying flow rate. Both the continuous and the discontinuous EFI systems have electronic control units (ECUs). The ECU is a pre-programmed micro-processor which constantly receives signals from a number of sensors that help it to evaluate the engine fuel needs; adjust the injector pulse; and energise the fuel pumps.
In the direct injection system, fuel is injected directly into the combustion chamber of each of the engine cylinders through their respective intake valves. However, in the indirect injection system, fuel is first of all fed into a central port (or a multi-port subsystem as the case may be) upstream of the intake valve of each engine cylinder, before it is injected into the respective combustion chambers.
CHAPTER THREE
METHODOLOGY
The direct, continuous electronic injection of fuel into the automobile engine is a special technology in the design of engine fuel supply systems. The primary factors that determine the quantity of petrol required by an automobile engine are the amount (by weight) of air that is supplied to the engine and the amount of power output desired by the driver (which is expressed in terms of the engine load). Whereas the amount of air supplied to the engine is monitored by a mass airflow (MAF) sensor; a throttle valve position sensor (TPS) monitors the amount of power output desired by the driver. Both the mass airflow sensor and the throttle valve position sensor are remotely controlled by the vehicle electronic control unit (ECU). The function of the ECU is to, among other things; interpret data from the MAF sensor and the TPS, in order to calculate the exact amount of petrol that must be injected into the engine.
From the illustration in Fig. 3.1, above; at engine start-up highly pressurised petrol is supplied to the engine at a steady flow velocity. As a result, the engine revs at a base speed of 850rpm, say. The base rpm is just enough to move the car against a certain minimum resistance, assuming the vehicle transmission systems were engaged.
Beyond engine start-up (i.e., at time, when the accelerator is pedaled),the petrol pump is signalled by the vehicle ECU to increase the velocity of the inlet petrol which it supplies to the engine. As more petrol is supplied to the engine; the engine burns the petrol to increase its speed and power. The direct relationship between engine speed and the flow velocity of the petrol which is supplied to the engine is justified by Nam and Giannelli (2005), in the equation:
CHAPTER FOUR
RESULTS AND DISCUSSION
RESENTATION OF RESULTS
The result of the simulation of the automatic control system for the blending of petrol with corrosion inhibitor is as shown in Fig. 4.3b. However, it is necessary to mention that:
- Figs. 4.1a and 4.3a show the Simulink Models for Figs. 3.4 and 3.7, respectively; while Figs. 4.1b and 4.3b show the results of the MATLAB simulation of Figs. 3.4 and 3.7.
- Figs. 4.2a and 4.4a are variants of the Simulink Models of Figs. 4.1a and 4.3a, respectively.
- Figs. The essence of Figs. 4.2a and 4.4a is to probe the results of the MATLAB simulations shown in Figs. 4.1b and 4.3b, respectively.
- Figs. 4.2b and 4.4b are the plots derived from probing the results of the MATLAB simulations of Figs. 4.1b and 4.3b, respectively.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
CONCLUSION
The design of an automatic feedback control system which enables the online blending of petrol has been carried out in this work. The results obtained from the analysis of the design suggest that the risk of over-blending petrol with corrosion inhibitor can be eliminated. A general expression for evaluating the forcing function which governs the disturbance in the process was also derived. The response of the automatic control system to the process disturbance was analysed with the aid of block diagrams. However, the stability of the control loop was determined by proxy, because of the complexity of the functions which modelled the behaviour of the automatic control system.
Despite this, it might be concluded that the automatic control system will be able to ensure that the composition of the petrol-additive mixture remains constant, regardless of any variations in the flow velocity of the petrol that is supplied to the automobile engine.
RECOMMENDATIONS FOR FUTURE WORK
Despite the limitations of this work, it is remarkable that the analysis presented in the work is intended to initiate groundwork research in the blending of petrol with additive in automobile engines, in the following areas:
- Investigation of the effect of dead time in the stability of the process control loop.
- Investigation of the effect of the control loop parameters in the ultimate gain and ultimate period of the automatic control system.
- Evaluation of the tuning characteristics of the process controllers (i.e., adaptation of the proportional-integral controllers in the automatic control system to the dynamics of the blending process).
- Production of the automatic control system for the online blending of petrol with corrosion inhibitor in the direct, continuous electronic fuel injection automobile engine.
REFERENCES
- Archer. M, and G. Bell. (2001). Advanced Electronic Fuel Injection Systems – An Emissions Solution for both 2- and 4-Stroke Small Vehicle Engines. A Publication by Synerject Systems Integration, Balcatta, Australia.
- Elonka, S. M. and A. R. Parsons. (1962). Standard Instrumentation Questions and Answers for Production-Process Control. Vol.1: Measuring Systems. McGraw-Hill Book Company, Inc. New York.
- Lee, S. H; R. J. Howlett and S. D. Walters. (2004). Engine Fuel Injection Control using Fuzzy Logic. Intelligent Systems and Signal Processing Laboratories. Engineering Research Centre, University of Brighton, UK.
- Mastanaiah, M. (2013). Performance of Electronic Fuel Injection Systems using Compressor and Controller.International Journal of Advance Engineering Research and Studies. Vol. II. Issue III. E-ISSN2249-8974. Pp 57-59.
- Mathur, H. B. (2014).What Adulterarion does to Vehicles, and the Air.http://www.downtoearth.org.in/node/13666#.VKnUAMXgHa8
- Nam, E. K and R. Giannelli. (2005). Fuel Consumption Modelling of Conventional and Advanced Technology Vehicles in the Physical Emission Rate Estimator (PERE).Assessment and Standards Division. Office of Transport and Air Quality. United States Environmental Protection Agency. EPA-420-P-05-001.
- Osueke, C. O. and I. O. Ofondu. (2011). Fuel Adulteration in Nigeria and its Consequences.International Journal of Mechanical and Mechatronics Engineering (IJMME-IJENS). Vol. 11. No. 04. P.43. http://www.ijens.org/vol_11_i_04/118004-7373-ijmme-ijens.pdf
- Passarini, L. C and M. Pinotti (Jnr). (2003). A New Model for Fast-acting Electromagnetic Fuel Injector Analysis and Design. Journal of Brazilian Society of Mechanical Sciences and Engineering. Vol. 25. No. 1. Rio de Janeiro.
- www.scielo.br/scielo.php?script=sci_arttext&pid=S1678-58782003000100014
