Specific heat in for the Otto cycle

AI Thread Summary
The discussion revolves around modeling the Otto cycle using ideal gas properties, specifically focusing on approximating the specific heat input (qin). The approach involves calculating the calorific value of petrol, adjusting for density and the air-fuel ratio, leading to an initial value of approximately 980.35 J. However, this value does not effectively translate to specific heat when divided by mass. The project requires optimizing the process using Excel Solver, with the compression ratio and qin as variables, indicating that the initial approximation may not significantly impact the final results. Clarification is sought on the heat introduction process in the Otto cycle and alternative methods for approaching the problem.
dinoclaro
Messages
1
Reaction score
0
Thread moved from the technical forums to the schoolwork forums
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 in which I then get the specific calorific value. I then proceed to multiply this by the volume of fuel in the cylinder (Volume at BDC divided by the air to fuel ratio). At the end of this process I get a value of around 980.35 J and cannot think of any way of converting this to specific heat as dividing by the mass obviously just returns the initial calorific value.

We are required to optimize the process using excel solver where the compression ratio and qin are the variables. Therefore this initial approximation has no bearing on the final optimized value (qin = 400Kj/Kg) . Although we are required to give an explanation of our initial value.

I fear that I am not understanding the Otto cycle process of where heat is introduced. Is there another way I should approach this problem?
 
Physics news on Phys.org
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top