Energy Balance For An Internal Combustion Engine Engineering Essay

Energy Balance For An Internal Combustion Engine Engineering Essay The main objective of the experiment is to measure the energy contributions to the diesel engine, which is treated as a thermodynamics system. The energy contributions that are not measured may then be estimated from an energy balance. There are two main, unmeasured energy contributions to identify:- An energy loss from incomplete combustion, in which some of the fuel is not burned completely. An energy loss by heat transfer to the air surrounding hot engine components. Introduction A Petter four stroke diesel engine will be used to investigate the efficiency of a diesel engine. Diesel engines are  internal combustion engines  designed to convert the chemical energy available in the fuel, into mechanical energy. This mechanical energy moves the pistons up and down inside cylinders. The pistons are connected to a crankshaft, and the up-and-down motion of the pistons, known as linear motion, creates the rotary motion needed to turn the wheels of a car forward. We are already aware of the fact that internal combustion engines have very low efficiencies, but the purpose of such experiment is to study where and how the energy is used and lost. This would help us to improve the efficiency of the internal combustion engines where ever possible. Theory Both diesel engines and petrol engines convert fuel into energy through a series of small explosions or combustions. The major difference between diesel and petrol engines is the way these explosions happen. In a petrol engine, fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, however, the air is compressed first, and then the fuel is injected, because as the air is compressed it heats up to around 400 °C, it is hot enough to ignite fuel. A four stroke diesel engine uses the following cycle (illustrated in Figure1): Intake stroke   The intake valve opens, and fresh air (containing no fuel), is drawn into the cylinder, moving the piston down. Compression stroke   As the piston rises, the air is compressed, causing its temperature to rise. At the end of the compression stroke, the air is hot enough to ignite fuel. Combustion stroke   As the piston reaches the top, fuel is injected at just the right moment and ignited, forcing the piston back down. Exhaust stroke   The piston moves back to the top, pushing out the exhaust created from the combustion out of the exhaust valve. Figure 1 24075-004-613c6f14.gif Eq1From the basic steady flow energy equation, using the air-cycle method, we may write:- The value of can be approximated, closely, to: , Cpe is taken as 1100J/KgK It is convenient to replace by in order to make an allowance for the possibility of incomplete combustion. *Where, FL, is the proportion of fuel energy that is not available because of incomplete combustion. Heat transfer, (Qr), is the sum of energy transferred to cooling water and energy lost to the surrounding from hot engine components, therefore we can write: Qr = -dot mw Cpw ( Tout Tin ) + Qrn Replacing all quantities in Eq1 we get: Symbols explained as follows: rate of heat energy transfer of system rate of the work done by the system (power) combustion air mass flow rate fuel mass rate specific enthalpy of products of combustion specific enthalpy of combustion air specific heat of water 4190 J/kgK Apparatus The Apparatus used in this experiment is mentioned as follows: Petter Diesel Engine: A four stroke, single cylinder, 659CC Petter Diesel Engine was used to conduct the experiment. Figure 2 shows the picture of Petter Diesel Engine used in the experiment. Ear Muffles: Ear muffles were used to protect the ears from the loud noise of the diesel engine; prolonged exposure to such loud noise without ear protection can lead to hearing impairment. Barometer: A Barometer was used to measure the atmospheric pressure at the time of experiment. Atmospheric pressure was needed to calculate the mass flow rate. The Barometer gives readings in mmHg. Figure 3 shows the picture of barometer used in the experiment. IMG_4763.JPGIMG_4767.JPG Figure 2 Figure 3 Experimental Procedure The purpose of this experiment was to investigate the efficiency of a diesel engine. To start with the experiment, all the gauges on the apparatus were pre set to default readings and as a safety precaution all students were provided with ear muffles. Each individual group member was assigned a task by the module lecturer. My assigned task was to measure the oil and at the same time, time the engine as it consumed the set amount of diesel. Similarly other students were given tasks, which they carried on doing as the experiment progressed. The engine was started and after waiting for the recommended time of ten minutes, all the readings were taken off gauges. A weight of 5kg was already placed onto the torque arm before starting the engine. Measurements such as fuel flow rate, cooling water flow-rate, spring balance, orifice plate pressure drop, speed gauge and electric thermometer were taken. Electric thermometer reading is divided into four parts, mentioned as follows: Exhaust temperature Cooling water inlet temperature Cooling water outlet temperature Air inlet temperature After taking all the readings, engine was shut down and ear muffles were removed. The readings taken off the gauges were then used to work out the energy balance for an internal combustion engine. Results MEASURED PROPERTY VALUE UNITS Atmospheric Pressure 764 mmHg Engine Speed 1500 rpm Spring balance reading 15 N Mass on torque arm 5 Kg Amount of Fuel measured 20 ml Time to consume fuel 97 Seconds Relative density of fuel 0.864 Orifice plate pressure drop 31 mmH2O Exhaust gas temperature 260 Degrees Celsius Cooling water inlet temperature 69 Degrees Celsius Cooling water outlet Temperature 75 Degrees Celsius Air inlet Temperature 18.5 Degrees Celsius Cooling water flow-rate 5 litres/minute Following readings were obtained from the gauges: 1. Shaft power output= torque* shaft rotational speed = W(kg load -dial reading)*rt*N(rpm)*2Ï€/60 = (5*9.81)-15*0.4*1500*2Ï€/60 = 2139.42 Watts = 6.13 10-3 kg/s 3. Fuel flow rate = = (20 10-3/1000) (864) = Kg/s 4. Heat transfer rate to the cooling water = {(l/min)/60} * 4.196* (Tout Tin) = *4.196*(75-69) = 2.098 kJ/s 5. Heat transfer to exhaust gases = (6.24 = 1.70 kJ/s 6. Energy Balance: Fuel Energy Input = mf*LCV = (1.7810-4) x (43106) = +7654W Shaft Power Output= + 2139.42W Cooling Water Heat Transfer= +2098W Exhaust Heat Transfer = +1700W Energy Transfer =Qm-mf *FL = -7654+2139.42+2098+1700 = -1716.58W Efficiency = n=useful work output fuel energy input =2139.42 x 100 7654 =27.95% (Useful Work) Energy to surroundings = (Heat supplied in fuel Useful work done Energy to coolant Energy to exhaust) = 7.66 2.14 2.10 1.68 = 1.74KW Percentage energy to coolant = Energy to coolant 100 Heat supplied in fuel = x 100 = 27.41% Percentage to exhaust = Energy to exhaust 100 Heat supplied in fuel = x 100 = 21.93% Percentage loss to the surrounding = Energy to surroundings 100 Heat supplied in fuel = x 100 = 22.71% pie chart.jpg Figure 5 Figure 4 Discussion Engine efficiency refers to an engines ability to transform the available energy from its fuel into useful work. The modern petrol combustion engine operates at an average of roughly 20 to 30 percent engine efficiency. The remaining 70 to 80 percent of the energy is lost to the surroundings in form of exhaust heat, mechanical sound energy and friction. Diesel engines are a bit more efficient. The  diesel engine  uses high compression to ignite its fuel. This higher compression compensates for the engines heat losses and results in roughly 40 percent engine efficiency. This engine efficiency is only observed by direct injection diesel engines (discussed later). Rest 60 percent energy, like the petrol engine is lost to the surroundings. The Petter diesel engine which was the subject of this experiment showed a poor overall efficiency compared to an average diesel engine. The overall efficiency of the Petter diesel engine was only 27.95 percent. The reason for such poor efficiency was that most of the energy was lost to surrounding, but that doesnt mean that the engine cannot me made more efficient. See Figure 4 and 5 for the distribution of energy lost and utilised. There are many ways to improve the efficiency of a diesel engine, some are discussed below: Turbochargers: The purpose of a turbocharger is to compress the air flowing into the diesel engine, this lets the engine squeeze more air into a cylinder and more air means that more fuel can be added; basically a turbocharger converts waste energy from an engines exhaust gases into compressed air, which it pushes into the engine. This allows the engine to burn more fuel producing more power and improves the overall efficiency of the combustion process, hence making the engine more efficient. However, the only disadvantage of a turbocharger is that, if it is in a cars engine it would take a few second to respond as the driver presses the pedal, this phenomenon is known as lag. Turbocharger suffers from lag because it takes a few moments before the exhaust gases reach a velocity that is sufficient to drive the impeller/turbine. Direct Injection: With direct injection, the diesel fuel is directly injected into the cylinder i.e. fuel is mixed with air inside the cylinder, allowing for better control over the amount of fuel used, and varies depending on demand. This makes the engine more fuel efficient. Before direct injection, the fuel was mixed with air in the cars intake manifold. Variable Valve Timing: Valves open and close to allow air and fuel to enter cylinders and for the products of combustion to exit. Different valve timings produce different results (more power and or better fuel economy). Many modern engines can vary valve timing, allowing the default low RPM range of the engine to have more economical timing, and the higher RPM range to go for max power. Cylinder Deactivation: Internal Combustion Engines, with this feature can simply deactivate some cylinders when less power is required, temporarily reducing the total volume of the engine cylinders and so burning less fuel. This feature is mostly found on V6 and V8 engines. Super Charger: Superchargers increase the intake of air into the combustion chamber. This means, more air into the combustion chamber and with more air, more fuel can be added, and more fuel means a bigger explosion and greater  horsepower. Adding a supercharger is a good way to increase the power of a normal-sized engine and thus making it more efficient. Superchargers also create better fuel efficiency by increasing the amount of oxygen available to an engines combustion chambers, because superchargers increase the power of the engine by utilising more oxygen, they do not require a larger engine and therefore also increase fuel efficiency by allowing cars to be lighter. The biggest disadvantage of superchargers however, is that they steal some of the engines horsepower. A supercharger can consume as much as 20 percent of an engines total power output but also generates as much as 46 percent additional horsepower. Since, it generates more power than it requires, it is generally th ought to be good option to increase engines efficiency. Conclusion Diesel engines are a form of Internal Combustion Engines. They are very inefficient if working on their own. Generally about 25-30 percent energy is used in work and the rest is lost to surroundings. The efficiency of a diesel engine can be enhanced by at least 10-15 percent if combined with the modern technological devices, such as turbochargers and superchargers. Other clever techniques can also be used to improve the fuel efficiency and overall engine efficiency of the engine, such as direct injection, variable valve timing and cylinder deactivation. Unfortunately, from the very beginning the focus on an internal combustion engine has been on producing more power rather than providing a better fuel economy, but nowadays due to growing awareness of environment and rising oil prices, engineers have shifted their attention on to producing more fuel efficient engines. For example, BMW is researching on ways to increase the fuel efficiency of a conventional engine by 10-15 percent by looking to  recover and reuse heat energy  lost through the exhaust and that absorbed by the engine cooling system. With such initiatives we can see a future of more efficient and more environmentally friendly engines.

Knapps Stage Model Essay

Dear John, the drama-filled romance movie, John Tyree, a young soldier, meets Savannah Curtis, a college student on spring break, and they quickly fall in love. The movie directed by Lasse Hallstrom, adapted from Nicolas Sparks’ novel of the same name. Dear John showcased many aspects of communications in its most simple forms. Including the ten stages of the Knapp Stage Model, which could actually be witnessed throughout the Dear John the movie and the book, as the two main characters, John and Savannah, developed their relationship and as they tried to maintain their relationship. In the Knapp’s Stage Model, Mark Knapp describes the progression and development of relationships as a series of ten stages in two phases: the ‘coming together’, initiation is followed by the experimenting , intensifying, integrating and bonding stages. In the ‘coming apart’, the differentiating, circumscribing, stagnating, avoiding and terminating stage occurs. The se stages are illustrated in the film Dear John. In the opening scene of Dear John, it was John’s and Savannah’s first time meeting, it was attraction at first sight. During the night scene at the beach, they conversed. I would still think it’s the initiating stage because the content of their conversation. They didn’t ask questions with the intention of knowing more of each other apart from that one question, ‘’When are you going back? † which was rather casual. That will sum up the initiating stage. In the later scene, John asked for a date and Savannah agreed. That means they have both passed each other’s test so there is an experimenting stage. By the way, John actually stayed at the Barbeque till the night when he mentioned that his dad cooked dinner. Why else would one blow off his dad if it isn’t because he likes the girl? Therefore, that supports my stand that they were already attracted to each other at the beach. At the dinner scene, they were started talking about something more personal. They were making small talk. The topic of family and John’s past came in. These topics usually w ouldn’t be brought up at the initiating stage because they’re too personal. I would also like to link to another concept with this scene which is relational needs of openness. If you notice, John wasn’t too comfortable with the talk to the point he asked â€Å"why do you want to know so much?† He would fall under the kind that closed off to other people. His answers were all one-liners, straight to the point with no further explanations. In the next scene, when they were walking towards the wooden house, that was another example of  getting to know each other through talking. This ends off the experimenting stage. They have a fight, but reconcile before John’s leave from the army is over. When john returns to the army, he and Savannah begin long distance relationship through handwritten letters. The first letter was very clear that Savannah loves John. Previously, John actually gave Savannah a note in which the content wasn’t disclosed to the audience till the very end of the movie. The note said â€Å"I love you† which was why Savannah wrote him, that letter was a reply. Those were disclosures of feelings to each other . In that scene, John said â€Å"I made you a promise, didn’t I?† and later, they both agreed to write to each other all the time. She was supposed to wait for him for a year while he was away in Germany. That was a sense of commitment to the relationship. This will summarize the intensifying stage. The fourth stage is integrating. This point is rather straightforward. It’s the turning point whereby the couple announces to their friends and family that they are a couple. In this case, you could see John being introduced to Savannah’s parents. Couples do not always follow strictly to the model. Steps could be jumped or revisited again. Sadly, there was no fifth stage (Bonding – marriage, engagement) for this pair in the movie. Conflicts arise because of different perceptions; it is also illustrated in this movie. There was a fighting scene at the patio and it was because John wanted to extend his tour with the army but Savannah did not want to wait for another two years. So after a long time apart, John and Savannah find themselves drifting apart and resigned to being apart from John, and Savannah sends a ‘Dear John’ letter telling him that she has bec ome engaged to someone else. John finally got a letter from Savannah which she initiated a break up. Break ups are due to many possible factors, in their case, changes, poor communication and unrealistic expectations. Changes referred to the huge changes they went through from the two weeks of summer break together to being thousand miles apart. Next, poor communication, I think this might be the least contributing factor. Even though, letters took weeks or months to reach each other, their letters were filled with words. They told each other everything about their lives so it wasn’t a case of drifting apart. Lastly, it is the factor I think contributed the most probably which is an unrealistic expectation. Long distance relationships are hard enough and a person can only take it for so long. The first year was fine but when  John added two more years onto the pile, it was too hard for Savannah to take. Although John’s and Savannah’s falling out they eventually came together as friends, es pecially when John’s father is on his death bed, John returns home and connects with his father, something he was not able to do before. John then sells his father’s coin collection to fund Savannah’s husband’s cancer treatment. In the last scene of the film, John sees Savannah on the street and they embrace. The movie may not showcase as much details; however it does show the importance of communication in a relationship. For example, Savannah chooses to write a letter to John to break the news of her engagement, instead of calling him, it shows that it is already a sign od avoiding the issue directly. A handwritten letter is a linear form of communication, as John is not given a chance to reply immediately. If you were in John’s position, and you received a similar letter about your partner’s engagement, would you go back home to fight for what you want, or would you be ‘John’, and just bury yourself with work? Hopefully, now you have a better understanding of the Knapp’s model and see how it fits into every relationship!

How do men treat women in Porphyria’s lover

Also the poem shows how men are the leaders, because in the poem for them to meet up she was the one who had to travel o him in the freezing cold and pouring rain. As well as that it is as though he is embarrassed by her because he is meeting her in a deserted place. The theme of power over women is also explored in Porphyry's Lover by Robert Browning, where the poet makes the narrator of the poem(Porphyry's Lover) repeat the word â€Å"mine† to highlight his possession of her. In addition to this, it is the woman's physical body which is arranged, in such a powerless position which in a weird way represents the power which men hold over women.There is also objectification to women â€Å"And give herself to me reeve†, as though she were an object that cannot object doesn't have any emotions and admire him. Then Porphyry's Lover kills her, think because he wanted that to be the last moment with her as he felt true happiness, â€Å"made my heart swell, and still it grewà ¢â‚¬  think that he thought that she was so happy and content that she wouldn't mind dying there and then. â€Å"l am quite sure she felt no pain†, but she was human and did feel the pain but he didn't see her like that. â€Å"And yet God has not said a word! Because he feels he hasn't been punished by God yet, he feels as though killing her was the right thing to o. My Last Duchess is a poem that has many important themes, one of these themes being objectification to women. The women in this poem known as the last duchess was dismissed as though she were an uncared for object with no feelings. She wasn't allowed to have a life outside of her husband and this was very common in the Victorian era. However this poems showed how if women didn't follow their husbands rules they would be killed, so men may have cared about their wives but they cared more about how they were seen by society.Just because the last duchess blushed near a man and her hand as showing her husband assum ed she was flirting and thought it was necessary to murder her as he thought that because of her he was looking bad to society. â€Å"l gave commands† the speaker said, this phase suggesting how men dominate women. He also says â€Å"Who'd stoop to blame† the word ‘stoop' meaning go down, and society in the Victorian era did not support men to be dominated by women. Having by Carol Ann Duffy is a poem that shows how the loss of a man during the Victorian era could cause major heartache and eternal misery.In the first line she calls him a â€Å"sweetheart bastard† the ‘sweetheart' shows that he is still in love with him but at the same time she hates him we know this from the word ‘bastard'. This is an oxymoron used to emphasis her aggression. The phrase â€Å"wished him dead† shows her desperation and how with each day her anger grows. â€Å"ropes on the back of my hands† is a metaphor which could be representing her veins due to stress and anger or the clenching and unclench of her fist showing that she is still tied to him. â€Å"Spinster. † Is a one-word sentence meaning that she is strung up and outdated.

Henrys Law Definition

Henrys Law is a chemistry law which states that the mass of a gas which will dissolve into a solution is directly proportional to the partial pressure of that gas above the solution.