Otto Definition and 56 Threads

A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol...

Hello, just wanted to ask regarding the otto cycle; if we were to find the entropy at the phase of isentropic compression and I was already able to derive the temperature 1 and 2 and the pressures at 1 and 2 and I also have the compression ratio of 10. How do I derive the entropy (s1 and s2)...

Hi, i have this question and don't understand it. can somebody explain what i have to do. i know a ideal engine is a engine running on carnot cycle i what the cycles are i don't know what relative efficiency is and what there looking for (Q) Review the relative efficiency of ideal heat engines...

Writing about Engines and just muddled up diagrams and confused now. Which PV diagrams is for Compression Ignition and which one for Compression Ignition. I think one on left is CI and right SI. Cheers

1-->2 (adiabatic) $$P_1V_1^γ=P_2V_2^γ$$ $$P_2=18,4.10^5Pa$$ $$T_1V_1^{1-\gamma}=T_2V_2^{1-\gamma}$$ $$T_2=429,32K$$ 2-->3 (isochoric) $$\frac{P_2}{T_2}=\frac{P_3}{T_3}$$ $$\frac{18,4.10^5}{429,32}=\frac{P_3}{T_3}$$ 3--> 4 (adiabatic) $$P_3V_3^{\gamma}=P_4V_4^{\gamma}$$...

So we know that every reversible engine working between the same temperatures will have the same efficiency(the same as Carnot engine). So let's consider for example reversible Otto cycle. So as you can see on the picture it is operating between ##T_1## and ##T_3##, so I was thinking that it...

Hello! I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle we see that while the pressure drops to near surrounding levels the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How...

Hello! I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle, we see that while the pressure drops to near surrounding levels, the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How...

Hello, I am looking for resources that show you how to design an simulate and engine from scratch. I want to design a complete engine using CAD. Afterwards I would like to analyze the engine using FEA and CFD (Heat transfer, fluid flow etc.) simulations. This is all for learning purposes. I...

In case of Otto cycle we consider that heat is immediately added to air fuel mixture(i.e constant volume heat addition) but in case of diesel cycle we consider heat addition at constant pressure and we also talk of cutoff ratios.why so??

Hello! In ideal Rankine cycle, we say that during the isobaric expansion, the heat provided to the system is Qin = h3 - h2 However, in my opinion, it is Qin - W = Δh -> Qin - PΔV = Δh. Which is correct? Secondly, In Otto cycle, let's say you have calculated Wnet in kJ/kg. In order to be able...

Hello guys, I am a bit confused. Is it that PV/T=constant for ALL the processes of ALL cycles, like Otto, Diesel, Rankine? I know that PV=mRT, so does that mean that PV/T=constant all the time? Secondly, I am a bit confused as I read that PV^γ=constant. What is that exactly? Where does it come...

One big coincidence of thermodynamics is that automobiles are usually powered by an Otto cycle This cycle consists of an adiabatic compression (the cylinder compresses), isochoric compression (the fuel ignites, increasing the temperature in too short a time for the piston to move), adiabatic...

I'm a mechanic who is currently doing a study automotive engineering. Being someone who worked on both diesel and petrol cars I know what a higher or lower air fuel ratio (AFR) will do for both engines. However I don't fully understand how the following is possible. "Adding fuel in a diesel...

I have been trying to determine the efficiency of an ideal Otto cycle based on the compression ratio of my car and the heat of combustion of gasoline and I think I'm not entierly wrong but there is something quite off. When trying to calculate the temperature of the combustion stage my result...

What is the key difference between Otto engine and Carnot engine? Other than it is reversible or not, it seems to me they are so similar. Thanks.

hey my fellow ME please help me with this problem I am stuck at. 1. Homework Statement An Otto engine has a clearance volume of 7%. It produces 300 kW of power. What is the amount of heat rejected in kW? Homework Equations Wnet=Qadded-Qrejected (v2=Vc)Clearance Volume = (c)Clearance% x...

Homework Statement What is the clearance of an ideal otto engine if the efficiency is 46.4% and k=1.3 Homework Equations efficiency = Worknet/Heat Added k=1.3 hot air T= 1900kThe Attempt at a Solution i don't know how to start

Homework Statement A four cylinder, four stroke internal combustion engine has a bore of 3.7 in and a stroke of 3.4 in. The clearance volume is 16% of the cylinder volume at bottom dead center and the crankshaft rotates at 2400 RPM. The processes within each cylinder are modeled as an air...

Homework Statement An Engine works within Otto cycle where the compression ratio is 6, and 350 kJ of heat was added to it. Determine the efficiency of the cycle and the work done if Cp/Cv is 1.45Homework Equations Efficiency Otto = (1- r1-k) Efficiency (eff.) =Work (W) /Heat Transferred (Q)The...

why are heat addition and rejection processes in an otto cycle constant volume processes?similarily why does heat addition occurs at constant pressure in a diesel cycle?

I have 2 questions, which are related, and was hoping someone could help me clear things up. First question, isn't the Otto cycle reversible and usable as a refrigerator? Referring to the diagram above & let me go part by part. AD: Assume the corresponding part of the working substance is...

Why is the heat rejection process in an otto cycle is at constant volume. Let us say that the exhaust and intake stages in the actual cycle are the last two strokes of the cycle. In the ideal cycle, it seems to me that they merge those two stages into one stage which is heat rejection and...

Why do we want self-ignition in diesel engines but do not want it in otto engines or in other words why does self-ignition cause detonation in otto engines but do not cause in diesel engines?

Homework Statement "A car has a six-cylinder Otto-cycle engine with compression ratio r = 10.6. The diameter of each cylinder is 82.5 mm. The distance that the piston moves during the compression stroke (see fig. 1) is 86.4 mm. The initial pressure of the air-fuel mixture (at point a in...

Diesel, Otto , Joule TRICK? Hi Guys, I try to callculate the efficiency for a cycle Process. For Diesel, Otto and Joule Processes you can write the efficiency as a really small equation. I have seen that for example sometimes the adiabatic equation is used, but i don't understand in which...

I am attempting to improve a spreadsheet I created back in uni some 5-6 years ago, which models all the velocities and accelerations of the pistons and rods, as well calculating pressure, temperature and resulting torque. It is only a simple model so far, originally it started simply by...

Homework Statement Estimate the change in volume of carbon dioxide if 'r' is increased from 10 to 11 (10% increase). Assume 30 million cars, all use 1m^3 of fuel each year Homework Equations Efficiency of an Otto Cycle η=1-r^(1-gamma) The Attempt at a Solution Original...

Hello All! I am new to the forum and need help. I have looked at multiple sites an looked at 328 threads titles and about 20 actual threads today to find the info I was looking for...no luck. Here is my question: I have a 12.5KW natural gas generator and want to know much heat and I can...

Homework Statement p1, V1, T1 and ε (compression ratio) are known I need to find: p2, p3, p4 T2, T3, T4 V2, V3, V4 but I don't know how to find p3, p4, T3, T4 Homework Equations ε = V1 / V2 V1 = V4 V2 = V3 T1 * V1^(k - 1) = T2 * V2^(k - 1) T3 * V3^(k - 1) = T4 *...

Homework Statement attached as pdf (problem 1) (part b)Homework Equations w=p2v2-p1v1 / n-1 w=mR(T2-T1) / 1-nThe Attempt at a Solution I was able to determine the pressure and temperatures at all points, but to find the work i appear to need the volume, I also looked at w=h2-h1 but I am not...

Does anyone know any sources (i.e. car manufacturers) that provide the exhaust air flow parameters for the some specific car engines? I need stats on various otto & diesel cycle engines (small compact car engines, large semi truck engines, etc.). When I say exhaust air flow parameters, I need to...

Homework Statement Show that the net work done by the otto engine per cycle is Cv(Tc - Tb)(1 - Ta/Tb) PV diagram: [PLAIN]http://www.antonine-education.co.uk/physics_a2/options/module_7/topic_4/Otto_indic.gif Homework Equations Work done by a kmole of gas expanding irreversibly and...

Homework Statement What is the indicated thermal efficiency of an engine? Fuel used in total 42.61 cc/min @ 1730 rpm. Fuel used to get to 1730 rpm = 29.16 cc/min no load. Fuel left = 13.45 cc/min to do approx 4.335 kw at 1730 rpm approx 40.95 kph Fuel heat content 34.8 kj/l...

Homework Statement The last (8 mark) part of this (also in attachment): http://img189.imageshack.us/i/imag0095l.jpg/ (very sorry for having to post an image, I spent a good hour trying to tex it in this, but there's something wrong with my parsing in the preview post. anyway...) Homework...

My team has recorded information on a single cylinder Otto cycle from a lab we have done. We are supposed to compare the theoretical efficiency of the cycle to the experimental efficiency. Using a given compression ratio of 3 and the ratio of specific heats for the fuels we used we were able to...

Homework Statement (a.) This was just a log-log plot of the otto cycle (b.) Derive an expression for the ratio of maximum to minimum temperature experienced by the cylinder head during the part of the cycle that contains only isochoric and and adiabatic transitions in terms of the compression...

Problem / Question 1)Study the engine cycles for the Otto cycle, Diesel cycle, the Carnot cycle and the standard air cycle. Explain the principles of how they work why they are different and the benefits and disadvantages of each of the systems. I have wrote about the otto cycle...

I've been trying to grasp it very thoroughly (excuse me for my english, I'm belgian) as I have a course of thermodynamics now in my first year of Physics. There is one last thing bothering me about entropy: Take the Otto-cycle (two adiabats, two ischores/isometrics). We know the cycle is even...

I have a general question about otto cycle. If we heat a gas with constant volume its temperature rise according to PV=mRT. However during Isentropic compression(delta Q and delta S is zero), the volume is becoming less and pressure is increasing but i don't know why the temperature should...

hey guys, just wanted to know, in the graph of the OTTO cycle in the link http://www.qrg.northwestern.edu/ther...Pv-diagram.gif are stage (2-3) and (1-4) adiabatic or not, if so why are they the reason i ask is that i have a graph showing that these stages are adiabatic, however...

hey guys, just wanted to know, in the graph of the OTTO cycle in the link http://www.qrg.northwestern.edu/thermo/design-library/otto/Otto-Pv-diagram.gif are stage (2-3) and (1-4) adiabatic or not, if so why are they the reason i ask is that i have a graph showing that these stages are...

Theoretically, we can have reversible isochoric expansion and isochoric compression. Is Otto Cycle reversible then? I read that the efficiency of all reversible engine between two heat reservoir would have the same efficiency. However, since the efficiency of an Otto Cycle is lower than...

Homework Statement Analyze an air-standard Otto cycle assuming it is a cold cycle with properties evaluated at 300 K. Air intake and exhaust are at 300 K, 1 bar. After the combustion (heat in) process, the temperature is 2500K. The compression ratio is 9. The volume at bottom dead center...

I want to compare the Ideal Diesel, Otto and Dual cycles with constant specific heats. I am interested in knowing the relationship between r (compression) and nth (efficiency). I am unable to determine the common inputs to all three which can give me the efficiency for all the cycles. r with...

The idealized cycle shown is known as the Otto cycle. (Intro 1 figure) Suppose an engine is executing this Otto cycle, using a gas (not necessarily ideal) as its working substance. From state A to state B, the gas is allowed to expand adiabatically. (An adiabatic process is one in which no...

Homework Statement Gasoline engines operate approximately on the Otto cycle, consisting of two adiabatic and two constant-volume segments. The Otto cycle for a particular engine is shown in figure below. see atchmt 1. Find the maximum temperature in terms of the minimum temperature T_min...

hi i just want to know the formula of the otto cycle for the folowwing parameter: compression ratio,cycle work,heat added,heat rejection,thermal efficiency and mean effective pressure. and also may i know the formula for getting the pressure (bar) and the volume(m3/kg) temperature(K) for...

I'm trying to estimate the temperature of combustion in an Otto Cycle engine, using a formula based on the First Law: T4 = T3 + fQ /cv Where T4 is the combustion temperature, T3 is the air temperature after compression, f is the fuel/air ratio, Q is the heat energy of the fuel, and cv is...

Homework Statement Considering Otto Wiener's experiment in monochromatic light of wavelength 550nm, if the film plane is angled at 1 degree to the reflecting surface, determine the number of bright bands per centimeter that will appear on it. Homework Equations dont know The...