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# t-s diagram otto cycle

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## t-s diagram otto cycle Post Review

SI Engine:Working of 4 stroke SI Engine, Otto Cycle-Derivation,P-V & T-S Diagram

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P-V and T-S Diagram of otto cycle, Diesel cycle, Dual cycle (thermodynamics) by gate class mech: via @YouTube

## t-s diagram otto cycle Q&A Review

### Why is the slope of two constant volume cycle different in the Otto cycle?

In Otto cycle, heat addition and heat rejection processes are constant volume processes. So if you draw a P-V diagram of Otto cycle, it will look like, So from the above graph you can see that both constant volume processes are being parallel to vertical axis. So form the basic mathematics anyone can tell that the slope of these processes is ,Infinity. ,Edit:, As I was receiving comments that the questioner meant the slope of constant volume processes of T-S diagram. So I decided to edit this answer and answer the original question. First of let me include the T-S diagram for an Otto cycle: As you can observe from the above graph that both heat supplied and heat rejection processes aka constant volume processes vary with temperature and entropy. But both processes have different slopes this is because the total amount of heat supplied will never be equal to the total amount of heat rejected. This loss of energy causes the variation in slopes. This loss might be in friction,heat losses etc. So the slope of heat addition process is always higher compared to the slope of heat rejection process. The difference between the value of heat supplied and heat rejected is called ,work,. Akshay Thanks.

### Which cycle has maximum efficiency for the same maximum pressure among Rankine, Brayton, Otto, Diesel and Dual cycle? Can you please rate them from highest to lowest?

Maximum Pressure can be attained in an Air Standard cycle in two cases: Case 1: Same Maximum Pressure and Heat Input For same maximum pressure and heat input, the Otto cycle (1-2-3-4-1) and Diesel cycle (1-2'-3'-4'-1) are shown on the T-s diagram in the figure. It is evident from the figure that the heat rejection for Otto cycle (area 1-5-6-4 on T-s diagram) is more than the heat rejected in Diesel cycle (1-5-6'-4'). Hence Diesel cycle is more efficient than Otto cycle for the condition of same maximum pressure and heat input. One can make a note that with these conditions, the Diesel cycle has higher compression ratio than that of Otto cycle. One should also note that the cycle which is having higher efficiency allows maximum expansion. The Dual cycle efficiency will be between these two. Therefore, ranking the three cycles on the basis on efficiencies, Diesel Cycle > Dual Cycle > Otto Cycle Case 2: Same Maximum Pressure and Work Output The efficiency, η can be written as Refer to T-s diagram. For same work output the area 1-2-3-4 (work output of Otto cycle) and area 1-2'-3'-4' (work output of Diesel cycle) are same. To achieve this, the entropy at 3 should be greater than entropy at 3' .It is clear that the heat rejection for Otto cycle is more than that of diesel cycle. Hence, for these conditions, the Diesel cycle is more efficient than the Otto cycle. The efficiency of Dual cycle lies between the two cycles. Therefore, ranking the three cycles on the basis on efficiencies, Diesel Cycle > Dual Cycle > Otto Cycle Note: We cannot compare Rankine cycle with Gas Power cycles (Otto, Diesel Dual), since it is a steam cycle and the working medium for a steam cycle is water. Water in the steam cycle has a much lower temperature and pressure than air standard cycles and thus cannot be compared with them. Also, Brayton cycle is meant for much larger heat engines and cannot be compared to the much smaller Otto, Diesel and Dual Cycle Engines.

### Why is the Thermal Efficiency of Diesel Engines higher than that of Petrol Engines?

If you compare only Otto and diesel cycle from graph for same compression ratio efficiency of Otto cycle(PETROL ENGINE) is more than efficiency of diesel cycle(DIESEL ENGINE). But in actual practice for same power engine the compression ratio of diesel engine is more than petrol engine. Efficiency of engine is based on the working conditions and limitation related to engine like there is limitation on maximum pressure , maximum temperature . There are certain criteria from which diesel and Otto cycle can be compared by considering some parameter constant. 1)For same maximum pressure and maximum temperature:- Otto cycle:-1–2–3–4 & Diesel cycle:-1–2′-3′-4 Heat supplied is given by area under 2–3 on T-S curve for Otto cycle Heat supplied is given by area under 2′–3 on T-S curve for Diesel cycle Heat rejected is given by area under 4–1 on T-S curve for Otto cycle Heat rejected is given by area under 4–1 on T-S curve for Diesel cycle Efficiency of cycle =1-(heat rejected/heat supplied) From the graph it is clear that heat supplied in case of diesel cycle is more and heat rejected in both cycles is same . Hence the efficiency of Diesel is greater than efficiency of Otto cycle in this case. 2)For same maximum pressure and heat input :- Otto cycle:-1–2–3–4 & Diesel cycle:-1–2′-3′-4′ Heat supplied is given by area under 2–3 on T-S curve for Otto cycle Heat supplied is given by area under 2′–3′ on T-S curve for Diesel cycle Heat rejected is given by area under 4–1 on T-S curve for Otto cycle Heat rejected is given by area under 4′–1 on T-S curve for Diesel cycle Efficiency of cycle =1-(heat rejected/heat supplied) In this case area under 4–1 is more than area under 4′-1 on T-S diagram .i.e.heat rejected in otto cycle is more than heat rejected in diesel cycle . Hence the efficiency of Diesel cycle is greater than efficiency of Otto cycle .

### What are the differences and similarities between otto cycle and Brayton cycle?

Look this image, You can analyse both of them with this P-V & T- S diagram of both. One similarity is, ,if compression ratio is then efficiency of Otto engine & Brayton engine is same., I hope you know the efficiency of both., ,You can see it in image. Applicationwise : In reciprocating engine, Otto cycle is more suitable than Brayton cycle. Because engine can not efficiently handle large volume of low pressure gas or if possible than engine size should be more, but it's not possible practically because we have limited space in reciprocating engine. In turbine power plant, Brayton cycle is more suitable than Otto cycle because in Otto cycle in IC engine exposed highest temperature only during power stroke but in steady flow device exposed highest during all operations. ( For material protection less temperature used in steady flow device). Also, in steady flow device, it's difficult to carry with constant volume than constant pressure. Hope, this helps.

### What is Otto engine?

Otto engine is an internal combustion engine,which is mainly powered by petrol and it's run on Otto cycle.Its also known as petrol engine or gasoline engine but named Otto engine because it's designed by Nikolaus Otto a German Engineer. For more information about Otto cycle: Otto Cycle - Processes with p-V and T-s Diagrams

### What is otto cycle? Describe the complete process involved in otto cycle with p-v and t-s diagram

The Otto cycle is a cycle of constant volume combustion. There is a theoretical and a real Otto cycle. In the theoretical Otto cycle, combustion is actually performed at V = const, which is a vertical line on the p - v diagram. In the case of actual constructions of reciprocating machines operating according to the Otto system (petrol engines with spark plugs), combustion cannot be performed at V = const because the piston is not stationary at that moment, ie the flame front has a certain length of travel that must be overcome. to realize instantaneously, but for a certain period of time other than zero. During that time, the crankshaft rotated by at least 3 degrees. That is why the real Otto cycle is always less efficient than the ideal. After forced ignition (spark plug), the working substance expands, which is equal to the degree of previous compression, ie compression = expansion. Exhaust is a classic heat dissipation.

### How can I understand T-S diagram of otto cycle?

The above diagram is the T-S diagram for an Otto cycle. Process 1–2 - This represents the isentropic compression process. It is carries out reversibly and adiabatically i.e. isentropically. So the entropy remains constant. The temperature changes according to the relation - T,_2, / T,_1, = (V,_1, / V,_2,),^{\gamma - 1} S,_1, = S,_2 Process 2–3 - This represents the constant volume heat addition. Since heat transfer occurs, both temperature and entropy change from 2 to 3. We have - TdS = dU + pdV Since it is a constant volume process, dV = 0, and dU = c,_v,dT dS = c,_v,dT/T So entropy changes in a logarithmic manner with temperature, giving process 2–3. Process 3–4 - This represents the isentropic expansion process. This is similar to 1–2, but undergoes expansion instead of compression. The same equations apply. Entropy remains constant. Process 4–1 - This represents the constant volume heat rejection. This is similar to 2–3, but has rejection of heat instead of addition of heat. As a result, both temperature and entropy fall. The same equations apply as process 2–3.

### In a four-stroke cycle, does the minimum temperature inside the engine cylinder occur at the beginning of the suction stroke or the end of the suction stroke?

Check out a T-s diagram: Here’s an fun little excel template for calculating P-v and T-s for Otto cycle engines ,http://www.faculty.virginia.edu/ribando/modules/xls/Thermodynamics/OttoTemplate.xlsm Good basic explanation of the theory here. ,What is Otto Cycle - P-V and T-S Diagram Easiest Explanation? - Mechanical Booster