# Otto Cycle And Diesel Cycle Pdf

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## ME354 Thermodynamics 2

The Air Standard Otto cycle is the ideal cycle for Spark-Ignition SI internal combustion engines, first proposed by Nikolaus Otto over years ago, and which is currently used most motor vehicles.

The following link by the Kruse Technology Partnership presents a description of the four-stroke Otto cycle operation including a short history of Nikolaus Otto. Once again we have excellent animations produced by Matt Keveney presenting both the four-stroke and the two-stroke spark-ignition internal combustion engine engine operation. The analysis of the Otto cycle is very similar to that of the Diesel cycle which we analysed in the previous section.

We will use the ideal "air-standard" assumption in our analysis. Thus the working fluid is a fixed mass of air undergoing the complete cycle which is treated throughout as an ideal gas. All processes are ideal, combustion is replaced by heat addition to the air, and exhaust is replaced by a heat rejection process which restores the air to the initial state.

The most significant difference between the ideal Otto cycle and the ideal Diesel cycle is the method of igniting the fuel-air mixture. Recall that in the ideal Diesel cycle the extremely high compression ratio around allows the air to reach the ignition temperature of the fuel. The fuel is then injected such that the ignition process occurs at a constant pressure. In the ideal Otto cycle the fuel-air mixture is introduced during the induction stroke and compressed to a much lower compression ratio around and is then ignited by a spark.

The combustion results in a sudden jump in pressure while the volume remains essentially constant. The continuation of the cycle including the expansion and exhaust processes are essentially identical to that of the ideal Diesel cycle. We find it convenient to develop the analysis approach of the ideal Otto cycle through the following solved problem:.

Solved Problem 3. Neatly sketch the pressure-volume [ P-v ] diagram for this cycle, and using the specific heat values for air at a typical average cycle temperaure of K determine:. The first step is to draw the P-v diagram of the complete cycle, including all the relevant information. We notice that neither volume nor mass have been provided, hence the diagram and solution will be in terms of specific quantities. We assume that the fuel-air mixture is represented by pure air. The relevant equations of state, internal energy and adiabatic process for air follow:.

However they are all functions of temperature, and with the extremely high temperature range experienced in internal combustion engines one can obtain significant errors. In this problem we use a typical average cycle temperature of K taken from the table of Specific Heat Capacities of Air.

We now go through all four processes in order to determine the temperature and pressure at the end of each process, as well as the work done and heat transferred during each process. Note that the pressure P 4 as well as P 2 above could also be evaluated from the adiabatic process equation. We do so below as a vailidity check, however we find it more convenient to use the ideal gas equation of state wherever possible.

Either method is satisfactory. Notice that we have applied the energy equation to all four processes allowing us two alternative means of evaluating the "net work output per cycle" and the thermal efficiency, as follows:. Note that using constant specific heat values over the cycle we can determine the thermal efficiency directly from the ratio of specific heat capacities k with the following formula:.

Quick Quiz: Using the heat and work energy equations derived above, derive this relation. Problem 3.

## Thermodynamic Principles

Introduction to Internal Combustion Engines pp Cite as. This chapter provides criteria by which to judge the performance of internal combustion engines. Most important are the thermodynamic cycles based on ideal gases undergoing ideal processes. However, internal combustion engines follow a mechanical cycle, not a thermodynamic cycle. The start and end points are mechanically the same in the cycle for an internal combustion engine, whether it is a two-stroke or four-stroke mechanical cycle. Unable to display preview. Download preview PDF.

In this sequence of cycles many physical and chemical quantities change from cycle to cycle. For example, the combustion heat changes due to residual gases,​.

## Thermodynamic Principles

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. End of compression pressures shown in Figure D. However, combustion processes differ significantly in actual engines, compared to the idealized cycles.

### Difference Between Otto Cycle and Diesel Cycle [Notes & PDF]

Klein, S. October 1, Gas Turbines Power. October ; 4 : — Comparisons of the compression ratios, efficiencies, and work of the ideal Otto and Diesel cycles are presented at conditions that yield maximum work per cycle. The compression ratios that maximize the work of the Diesel cycle are found always to be higher than those for the Otto cycle at the same operating conditions, although the thermal efficiencies are nearly identical. The compression ratios that maximize the work of the Otto and Diesel cycles compare well with the compression ratios employed in corresponding production engines.

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. Diesel engines are used in aircraft , automobiles , power generation , diesel-electric locomotives , and both surface ships and submarines. This is an idealized mathematical model: real physical diesels do have an increase in pressure during this period, but it is less pronounced than in the Otto cycle.

Energy Resources and Systems pp Cite as. Energy sources such as coal, natural gas, or petroleum cannot be used directly to perform a work. These sources are burned to generate heat which is then converted to mechanical or electrical energy. These processes are governed by thermodynamic cycles and the efficiency of the overall process depends mainly on the choice or efficiency of the cycle. A number of thermodynamic cycles using various working fluids have been suggested. The description and analysis of these cycles are presented in this chapter.

#### Problem Set #6: IC Engines

The Otto cycle is a set of processes used by spark ignition internal combustion engines 2-stroke or 4-stroke cycles. These engines a ingest a mixture of fuel and air, b compress it, c cause it to react, thus effectively adding heat through converting chemical energy into thermal energy, d expand the combustion products, and then e eject the combustion products and replace them with a new charge of fuel and air. Compression stroke, , increase. Combustion spark , short time, essentially constant volume. Model: heat absorbed from a series of reservoirs at temperatures to.

The Air Standard Otto cycle is the ideal cycle for Spark-Ignition SI internal combustion engines, first proposed by Nikolaus Otto over years ago, and which is currently used most motor vehicles. The following link by the Kruse Technology Partnership presents a description of the four-stroke Otto cycle operation including a short history of Nikolaus Otto. Once again we have excellent animations produced by Matt Keveney presenting both the four-stroke and the two-stroke spark-ignition internal combustion engine engine operation. The analysis of the Otto cycle is very similar to that of the Diesel cycle which we analysed in the previous section. We will use the ideal "air-standard" assumption in our analysis.

Significant it is to discover the answer to this, as many of us still are unaware of what these terms mean. Otto cycle is used by petrol ignition whereas diesel engine uses the diesel cycle. The main difference that separates these two cycles is the way they supply heat to the engine to begin the ignition. Another noteworthy difference is that the Otto cycle heat occurs at constant volume, whereas the diesel cycle works on constant pressure. This could be the main difference between Otto cycle and diesel cycle. Besides, there are other differences as well, which we are going to explain here.

The main difference between Otto and Diesel cycle is that The otto cycle explosion process takes place at a constant volume process and the Diesel cycle explosion process takes place at a constant pressure process.

In general, engines using the Diesel cycle are usually more efficient, than engines using the Otto cycle. The diesel engine has the highest thermal efficiency of any practical combustion engine. The largest diesel engine in the world peaks at Since energy is conserved according to the first law of thermodynamics and energy cannot be be converted to work completely, the heat input, Q H , must equal the work done, W, plus the heat that must be dissipated as waste heat Q C into the environment. Therefore we can rewrite the formula for thermal efficiency as:.

Calculate the ideal air standard cycle efficiency based on the Otto cycle for a gas engine with a cylinder bore of 50 mm, a stroke of 75 mm and a clearance volume of An idealized air-standard diesel cycle has a compression ratio of

These facilities include utility scale power generation plants up to MW and as small as the Williamson Energy Island where our largest single generator is kW. The overall intention of the course is to show how heat energy is used to generate electricity and the various efficiencies of each type of heat engine. This is a rare opportunity to see the inner workings of so many power facilities in one course. Each of the four utility scale plants that will be toured dwarf the generating equipment at Williamson.

Пуля пролетела мимо в тот миг, когда маленький мотоцикл ожил и рванулся. Беккер изо всех сил цеплялся за жизнь.

Бринкерхофф стоял точно завороженный и, не в силах унять дрожь, стукался лбом о стекло. Затем, охваченный паникой, помчался к двери. - Директор.

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