This chapter provides theoretical support used to answer the questions of the thesis. A complete account of the theories is found in section 2.2 and 2.3 of the thesis. These theories are tied together with the results and analysis to fulfill the purpose of the thesis.
Connection between aim and theory
Theory 1 and theory 2 in this section provide a theoretical background to the two questions stated in the purpose of the report:
What is the cause for the leakage in the oil pump? How can the leakage be resolved?
Theory 1 provides a theoretical foundation for the possible cause of the leakage in the oil pump and the way the oil reacts to pressure.
Theory 2 contains a theoretical basis for stopping the leakage by explaining how fluids behave.
Viscosity is a quantitative measure of a fluid’s resistance to flow [5, p. 25]. Due to viscous flow, shear stress appears in fluids [6, p. 31]. But if the fluid is at rest, there is no shear stress [6, p. 31]. The fluid then has the same pressure regardless of direction, and the pressure varies according to depth [4, pp. 22-23].
Pressure is transmitted through fluids [3, p. 10]. If there is a volume change or increase of pressure somewhere inside the system, the fluid will distribute this increase equally throughout the entire system [3, p. 10]. Because of the fluids ability to transmit pressure, it can be assumed that if the pressure is increased in one point of the system the increase is the same at every other point in the system [3, p. 10] [4, p. 22].
The pressure of the fluid always acts perpendicular to the surface of the wall containing it [4, p. 22]. This pressure will increase with the depth of the fluid and act the same no matter what direction [3, p. 34]. This increase in pressure is linear and change according to the hydrostatic equation [3, p. 34] [4, p. 25]. Therefore, the minimum pressure always occurs at the maximum height of the system [3, p. 88]. The depth of the system then determines the pressure difference from the surface [3, pp. 164-165].
The pressure difference in the fluid may be converted from potential energy to kinetic energy and push the oil through the system [3, p. 165]. As the law of conversation of energy applies to all fluids, there is a relationship between the potential energy of the fluid level and the kinetic energy of the flow [4, pp. 56-57]. Increasing the pressure of the fluid can therefore attain sizeable kinetic energy [4, pp. 56-57]. The same way narrowing the flow channel decreases the pressure, and the velocity of the fluid is increased [4, p. 61].
Theory 2 provides a theoretical foundation that can be used in constructing a solution that minimizes the unintended oil leakage.
Liquids can be considered incompressible at low pressures, but at higher pressures, the liquids compressibility can affect the system [3, p. 11] [4, pp. 46-47] [6, p. 42]. Accordingly, the density of a liquid can generally be regarded as a constant, and the analysis of a problem involving liquids is thereby simplified [7, p. 21]. The flow of a liquid is also considered incompressible at lower pressures [6, p. 42]. Viscosity in liquids decreases as its temperature increase [3, p. 16] [4, p. 11]. As the temperature increase, the intermolecular forces pulling the molecules to each other weakens, allowing them to move more freely [3, p. 16] [4, p. 11].
There are two major causes why a fluid starts to move; resultant forces and friction [3, p. 62].
Resultant forces act on fluids when there is a difference in pressure or temperature [3, p. 62].
Some fluids resist motion more than others because they have a higher viscosity [6, pp. 32-33].
This chapter provides an understanding of the process used to fulfill the purpose and aim of the thesis. Described in the chapter is the method used to answer the questions of the thesis with supporting references for each methodology.
Connection between aim and method
To answer the first question of the thesis the cause of the leakage was determined through testing of the oil system and theoretical research. This is described in section 3.2 – Identification of cause.
Several possible solutions were generated to answer the second question of the thesis, and were tested in turn to determine their effectiveness and potential realization.
Stated in this chapter is the method divided into sections for each step of the process, from identification and definition of the problem to testing of different solutions. Each step of the process is tied back to the original questioning and ultimately leads to finding a solution for the problem.
Identification of cause
The identification of the cause is the initial research of the problem. The primary testing together with the theoretical research provides a fundamental understanding of why the leakage occurs.
Several functional tests were set up on the current design of the oil pump system to determine the cause of the leakage. The main objective of the tests is to analyze the current system and the individual function of each component. The purpose of the tests is to determine the disadvantages, deficiencies and improvement opportunities in the current design [8, p. 145].
Both test 1 and 2 are constructed to find out what happens in specific scenarios when leakage occurs. The results of each scenario point to the cause of the leakage and what need to be rectified in the current system [8, p. 149]. This method of analysis requires equipment to recreate realistic scenarios.
When analyzing the cause, it is necessary to have drafts anchored in theory. These theories have been collected through thorough research of scientific literature. When preparing for the research, a reflection is done over the purpose and questions of the thesis to determine the central theories and subjects. With these determined, the research is initiated, and several databases are used for finding relevant literature. The literature is then read through and compared to the questions of the thesis. All relevant information is collected and compiled in section 2 – Theoretical framework. Concluding the theoretical research is an evaluation of the material collected, to determine if the data is sufficient. [7, p. 44]
The same process is used when choosing a relevant method for the entire section 4 – Method.
Definition and clarification
Clarifying the task and gathering data on the problem offers the possibility to discuss and reflect over the problem situation [9, p. 223] [10, p. 58].
In this pre-study, the oil system is analyzed objectively to prepare an eventual development of an alternate design. Using the different analyzation methods described in detail below an internal requirement is drafted as a basis for potential design development. The specification determines the most functional requirements of what the product is designed to do [8, p. 116].
For a problem to be solved, it is essential to know the primary purpose of the system [8, pp. 31,53] [9, p. 181]. By not focusing too much on the issue from the beginning, only the solutions without limitations, creativity is not constrained [11, p. 42]. The purpose of the function analysis is to analyze the system, determine the functions required and set the system boundary of the new design [12, p. 56].
All functions are divided into three groups: primary, necessary and wanted. The primary function is the reason the component exists [9, p. 181]. The functions that the primary function does not work without are called necessary functions. As well there are the wanted functions, the primary function is not dependent on these, but they increase the overall value of the product. [11, p. 42]
The system analysis is constructed to avoid misunderstandings regarding the purpose of the different components of the system. The system analysis shows the existing system with components and functions [12, p. 121] [9, p. 188]. By showing the structure of the problem with the parts and their relationships, a deeper understanding of the whole is achieved [11, p. 46] [9, p. 179].
This section describes the method used to generate solutions and create concepts.
Concept study method
The concept study is carried out according to the set-based concurrent engineering method (SBCE), first published by Ward at MIT in 1994 [8, p. 260]. This method is designed to develop new product solutions. SBCE does not limit each step of the development process with only one solution to proceed with [8, p. 261]. The basis of the method is to keep as many solutions to the problem open as long as possible, until they are proven not feasible or compliant with the requirement specification [8, p. 261].
The first stage of the process is to generate as many ideas as possible to reach a solution. Instead of determining the most prominent idea and solely proceed with this, several ideas are developed and tested parallel to each other. In the process of developing, testing and discarding the ideas, more knowledge and understanding about the problem is found that can be tied into the final solution. [8, p. 261]
The basic concept of SBCE is relatively flexible regarding the specific steps of the process and can easily be tailored to the problem at hand [8, p. 261]. The method is based on these three steps:
1. Define reasonable delimitations and decide within these limits appropriate sets of solutions. The limitations include an extensive search for solutions, with a focus on meeting the requirements given for the project. [8, p. 262]
2. Interact different sets and identify the average of compatible independent solutions. In this step, it is essential to utilize the requirements and discard the ideas that do not fulfill these. This includes the ideas that are not compatible with each other as well. [8, p. 262]
3. Develop and refine the solutions within the set and successively discard non-viable ideas. Interacting solutions are developed more in detail, analyzed and tested. Step by step the requirements harden and solutions that do not fulfill them are discarded. [8, p. 262]
Following is the concept generating methods used in the thesis. The methods fulfill the structure described in the previous section, starting with a wide range of ideas and narrowing the list as the work progress.
To generate as many concepts as possible, the method of brainstorming is used [11, p. 190]. Brainstorming is part of the creative method family [8, p. 120] and is used to rapidly and effectively generate ideas [12, p. 27]. The goal is several solutions that meet the requirements of the problem [10, p. 85].
In the brainstorming session, two different variations of brainstorming are used. This to increase creativity and approach the problem from different angles. [8, p. 174]
Stop and go is a variation that allows the participants to write down as much as they can on a specific time interval. When the time is up, a break is taken for a few minutes before starting again. This way the group avoids running out of ideas. [13, p. 50]
Random input is a technique that enhances the creative thinking by circumventing the narrow boundaries that the mind can put up when looking at a problem. The exercise is to come up with a random word, and through association tie this word to the problem and through the association come up with new solutions. [14, p. 53]
Before the brainstorming session started, the basic rules of brainstorming are carefully read through and agreed upon. Following rules are taken from the book ‘Design i focus’ by Kenneth Österlin [13, p. 55]:
Criticism and assessment is forbidden during the session A large quantity of ideas is sought
Think outside the box
The ideas generated in the brainstorming session are compiled and divided in groups depending on how they are intended to work. The list of ideas is then assessed, and in consensus, the ideas that are not realizable are removed from the list [6, p. 179]. The ideas remaining can now be evaluated and ranked according to relevance and estimated effectiveness.
The solutions that progress through the selection process are compared through a criteria evaluation method. By inserting them in a matrix they can be scored against each function taken from the function analysis, see section 3.3.1 – Function analysis [6, p. 186]. Scoring is decided on a scale from 1 to 10, 1 being not acceptable, 5 being acceptable and 10 being excellent [6, p. 187]. The assessment of the different solutions results in a ranked list of the solutions, deciding the order of testing to find the final solution [6, p. 190].
1.2 PROBLEM DESCRIPTION
1.3 PURPOSE AND AIM
2 Theoretical framework
2.1 CONNECTION BETWEEN AIM AND THEORY
2.2 THEORY 1
2.3 THEORY 2
3.1 CONNECTION BETWEEN AIM AND METHOD
3.2 IDENTIFICATION OF CAUSE
3.3 DEFINITION AND CLARIFICATION
3.4 CONCEPT STUDY
4 Results and implementation
4.1 TEST FOR DETECTION OF LEAKAGE
4.2 DEFINITION RESULTS
4.3 RESULTS OF CONCEPT STUDY
5.1 ANALYSIS OF RESULTS OF AIM 1
5.2 ANALYSIS OF RESULTS OF AIM 2
5.3 ANALYSIS OF METHOD CHOICE
5.4 VALIDITY AND RELIABILITY
6 Discussion and conclusions
6.4 FURTHER WORK AND RESEARCH
GET THE COMPLETE PROJECT