Otto cycle problems pdf

Cycles that model external combustion engines include the brayton cycle, which models gas turbines, and the rankine cycle, which models steam turbines. The thermal efficiency of a cycle, also denoted by, is a measure of the ability to convert heat energy into work. The 18 liter lenoir engine was able to produce only 2. The entire modern petrol engine works on otto cycle. Chapter 9 gas power cycles universiti tenaga nasional.

An example on solving for the thermal efficiency of an ideal otto engine with constant specific heats. The myth of the highefficiency externalcombustion stirling. Carnot cycle carnot cycle is theoretical thermodynamic cycle. Otto cycle engine an overview sciencedirect topics.

Otto cycle is a gas power cycle that is used in sparkignition internal combustion engines modern petrol engines. The idealized diagrams of a fourstroke otto cycle both diagrams. A thermodynamic cycle comprises a series of operations carried out on the working substance ws during which heat is supplied, and after which the ws is returned to its original state for a more comprehensive introduction to thermodynamic cycles also see thermodynamic cycles an example of a thermodynamic cycle is the internal combustion engine. The otto engine was a large stationary singlecylinder internal combustion fourstroke engine designed by the german nicolaus otto. In otto cycle engines, the pressure in the cylinder at the end of the expansion power stroke is still 3 to 5 atm when the exhaust valve opens. But, instead of rapid combustion at constant volume, the diesel. Calculate key characteristics such as mass of intake air, pressures and mep.

The working fluid contained in the cylinder of the car engine forms a closed system. In an otto cycle, process 12 is an isentropic compression process. Prior to the isentropic compression process, the air is 100 kpa, 35c, and. Diesel cycle problem with solution pv diagram of an ideal diesel cycle. Jan 12, 2017 problem 1 based on otto cycle video lecture of gas power cycles chapter from thermodynamics subject for mechanical engineering students. What is otto cycle pv and ts diagram easiest explanation. The pressure and temperature at the beginning of compression of an airstandard diesel cycle are 95 kpa and 300 k, respectively. Effects of combustion efficiency on an otto cycle article pdf available in international journal of exergy 72 january 2010 with 2,670 reads how we measure reads. A closedcycle device is one that periodically returns to its initial conditions, repeating the same process over.

Let assume the otto cycle, which is the one of most common thermodynamic cycles that can be found in automobile engines. Nicolaus august otto as a young man was a traveling salesman for a grocery concern. The work times the rate of the cycle cycles per second cps is equal to the power p produced by the engine. Carnot cycle there are only two temperatures in the carnot cycle heat is added at t h heat is rejected at t l there are four temperatures in the otto cycle heat is added over a range of temperatures heat is rejected over a range of temperatures. Apply first law closed system to process 23, v constant. In his travels he encountered the internal combustion engine built in paris by belgian expatriate jean joseph etienne lenoir. Brayton cycle reading problems 98 910 978, 984, 9108 open cycle gas turbine engines after compression, air enters a combustion chamber into which fuel is injected the resulting products of combustion expand and drive the turbine combustion products are discharged to the atmosphere compressor power requirements vary from 4080% of the power output of the. A system undergoing carnot cycle is called carnot heat engine. An otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. The ratio of these volumes v 1 v 2 is known as the. Otto cycle calculationotto cycle calculation problem statement. Parabolic motion, work and kinetic energy, linear momentum, linear and angular motion problems and solutions. In ideal otto cycles, airstandard assumption is used. The otto cycle is an open cycle or noncyclic process since the fresh airfuel is mixture is inducted inside the engine during each cycle and the burnt mixture is released to the atmosphere.

Otto cycle problem with solution what is nuclear power. Sep 26, 20 an example on solving for the thermal efficiency of an ideal otto engine with constant specific heats. In 1860 lenoir succeeded in creating a doubleacting engine which ran on illuminating gas at 4% efficiency. Through the combustion of fuel, heat is added in a constant volume isochoric process process, followed by an adiabatic expansion process power c stroke. Otto cycle the otto cycle is named after nikolaus otto 18321891, german who is credited as the first creator of a petroleum fuel based internal combustion engine operating under a four stroke cycle. Differences between diesel cycle and otto cycle engineering. It has comparatively has higher thermal efficiency.

Chapter 8 gas power cycles 8 833 an ideal otto cycle with air as the working fluid has a compression ratio of 8. The otto cycle is a description of what happens to a mass of gas as it is subjected to changes of pressure, temperature, volume, addition of heat, and removal of heat. At the time of heat addition, the piston is at the top dead centre tdc. May 05, 2015 on this page we discuss the otto thermodynamic cycle which is used in all internal combustion engines. The pressure and temperature at the end of the heat addition process, the net work output, the thermal efficiency, and the mean effective pressure for the cycle are to. The first law of thermodynamics for closed systems d the airstandard otto cycle sparkignition engine. It was a lowrpm machine, and only fired every other stroke due to the otto cycle, also designed by otto. Efficiency is the proportion of the work and the supplied heat. The temperature at the end of the isentropic expansion process is 800 k. Using the engine stage numbering system, we begin at the lower left with stage 1 being the beginning of the intake stroke of the engine. At the beginning of the compression process of an airstandard otto cycle, p 1 1 bar, t 1 290 k, v 1 400 cm 3. Prior to the isentropic compression process, the air is at 100kpa, 35isentropic compression process, the air is at 100kpa, 35oc, and 600 cmc, and 600 cm3. Let assume the diesel cycle, which is the one of most common thermodynamic cycles that can be found in automobile engines. The maximum temperature in the cycle is 2200 k and the compression ratio is 8.

The ideal otto cycle consists of two constant volume and two reversible adiabatic or isentropic processes as shown on pv and ts diagrams. On this page we have shown an ideal otto cycle in which there is no heat entering or leaving the gas during the compression and power strokes, no friction losses, and instantaneous burning occurring at constant volume. Pdf effects of combustion efficiency on an otto cycle. It is a gas power cycle that is used in spark ignition engine i. Before discussing these cycles, we first have to introduce the thermal efficiency of a cycle. Otto cycle, which models gasoline engines and the diesel cycle, which models diesel engines. Heat engines a heat engine is any closedcycle device that extracts heat from a hot reservoir, does useful work, and exhausts heat to a cold reservoir. Otto cycle the maximum efficiency of an ideal otto cycle engine, is given by 1. In an air standard otto cycle, the compression ratio is 7 and the compression begins at 35oc and 0. Today we will attempt to study it and understand what comprises of this otto cycle.

Let the engine cylinder contains m kg of air at point 1. Calculate the air standard efficiency and mean effective pressure for the cycle. Otto cycle is the theoretical thermodynamic cycle which describes the working of a spark ignition engine. In the otto cycle, heat addition takes place at constant volume. The pv and ts diagrams of an ideal otto cycle are shown on the left.

For a cyclic process, the change in the total internal energy of the gas during one cycle is zero. Ottos engine work during the eve of the industrial revolution was a critical development leading to the dawn of the automotive industry in the late 19th century. Solve problems based on the otto, diesel, stirling. What are carnot cycle, otto cycle, and diesel cycle. The pressure and temperature at the end of the heat addition process, the net work output, the thermal efficiency, and the mean effective pressure for the cycle are to be determined. Since process 12 is isentropic, t t v v t t v vr k k k 2 1 1 2 1 1 2 2 1 1 1 1 f hg i kj f hg i kj f hg i kj.

Force of gravity and gravitational field problems and solutions. O tto cycle is a gas power cycle that is used in sparkignition internal combustion engines modern petrol engines. At this point, let p1, t1, andv1 be the pressure, temperature and volume of air. The thermodynamics of the airstandard diesel engine can be analyzed like the otto cycle. Two isentropic reversible adiabatic processes two isochoric constant volume process. Me312 problems page 4 922 reconsider the otto cycle in prob. If the maximum temperature in the cycle is not to exceed 2200 k, determine a. The real open cycle is changed into a closed cycle by assuming that the gases being exhausted are fed back into the intake system. In an air standard otto cycle, the compression ratio is 7 and the compression. Carnot heat engine is a theoretical construct and carnot be built in practice. Chapter 3d the first law closed systems otto cycle. Prior to the isentropic compression process, the air is 100 kpa, 350c, and 600 cm the temperature at the end of the isentropic expansion process is 800 k. Internal combustion engine cycles machines thermodynamics.

In an otto cycle air at 1bar and 290k is compressed isentropic ally until the pressure is 15bar the heat is added at constant volume until the pressure rises to 40bar. The thermal efficiency of the cycle is so note that we could also rewrite this as. The compression ratio of an airstandard otto cycle is 9. Develop simplifying assumptions applicable to gas power cycles. It is the thermodynamic cycle most commonly found in automobile engines. Problem 1 based on otto cycle video lecture of gas power cycles chapter from thermodynamics subject for mechanical engineering students. If is too high, the mixture will ignite without a spark at the wrong location in the cycle. The british engineer james atkinson 18461914 realized that the efficiency of the otto cycle could be improved if the combustion gases could be expanded to near atmospheric pressure before being exhausted from the engine. If heat absorbed by the engine q 1 10,000 joule, what is the work done by the carnot engine. 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. In order to express the efficiency of the otto cycle, we need to evaluate the work performed by the gas during one cycle and the heat which the gas received during this cycle.

The ideal otto cycle consists of four internal reversible processes. The clockwise thermodynamic cycle indicated by the arrows shows that the cycle represents a heat engine. Determine a the closedsystem availability of the air at the end of isentropic expansion, in kjkg, if t 0 22 c and p 0 0. Otto s engine work during the eve of the industrial revolution was a critical development leading to the dawn of the automotive industry in the late 19th century. The mean effective pressure assume constant specific heats for air at room temperature. In an ideal spark ignition engine, there are four processes as follows. Otto cycle efficiency collection of solved problems. Otto cycle consists of two isoentropic and two isochoric processes, pressurevolume and temperatureentropy diagram of otto cycle are represented. Brayton cycle reading problems 98 910 978, 984, 9108 open cycle gas turbine engines after compression, air enters a combustion chamber into which fuel is injected the resulting products of combustion expand and drive the turbine combustion products are discharged to the atmosphere. It consist of four processes, two isentropic reversible adiabatic processes and two isochoric constant volume processes. As the compression ratio, increases, increases, but so does. Mar 04, 2018 what are the four processes of diesel cycle.

Carnot cycle problems and solutions solved problems in. The otto cycle is the ideal cycle for sparkignition engines, in honor of nikolaus otto, who invented it in 1867. The ideal otto cycle efficiency is shown as a function of the compression ratio in figure 3. Before the compression stroke of the cycle begins, the pressure is 0.

These processes can be easily understood if we understand pv pressurevolume and ts temperatureentropy. Applications of such cycles are the otto cycle, the joule cycle, and the diesel cycle. The area enclosed by the cycle on a pv diagram is proportional to the work produced by the cycle. It represents the ideal cycle for a spark ignition engine. One of key parameters of such engines is the change in volumes between top dead center tdc to bottom dead center bdc. Apr 03, 2016 otto cycle consists of two isoentropic and two isochoric processes, pressurevolume and temperatureentropy diagram of otto cycle are represented. Ottos engine work during the eve of the industrial revolution was a critical development leading to the dawn of the automotive industry in.