The cycle which consists of two reversible isotherms and two reversible isochores is called as
Consider air standard Otto and Diesel cycles, both having the same state ofair at the start of compression. If the maximum pressure in both the cycles isthe same, then compression ratio 'r' and the efficiency 'η' are related by
Which one of the following cycles has the highest thermal efficiency for given maximum and minimum cycle temperatures?
Ans. (d) Don’t confuse with Diesel cycle. As stirling cycle’s efficiency is equal to Carnot cycle.
The data given in the table refers to an engine based on Carnot cycle, whereQ1 = Heat received (kJ/min), Q2 = Heat rejected (kJ/s), W = Work output (kW)
S. No. Q1 Q2 W
1. 1500 16.80 8.20
2. 1600 17.92 8.75
3. 1700 19.03 9.30
4. 1800 20.15 9.85
If heat received by the engine is 2000 kJ/minute the work output will be,nearly,
Which one of the following changes/sets of changes in the source and sink temperatures (T1 and T2 respectively) of a reversible engine will result in the maximum improvement in efficiency?
Ans. (c) For maximum improvement in efficiency source temperature should be raised and sink temperature lowered.
What does the reversed ideal Stirling cycle consist of?
Which one of the following parameters is significant to ascertain chemicalequilibrium of a system?
For maximum specific output of a constant volume cycle (Otto cycle)
For the same maximum pressure and heat input, the most efficient cycle is
Assertion (A): Power generated by a four stroke engine working on Otto cycle is higher than the power generated by a two stroke engine for the same swept volume, speed,temperature and pressure conditions.
Reason (R): In a four stroke engine one cycle is completed in two revolutions.
Match List I with II and select the correct answer using the code given below the
List I List II
(Prime Mover) (Air Standard Cycle)
A. High Speed diesel engine 1. Atkinson Cycle
B. IC engine having expansion 2. Dual combustion limited pressure ratio greater than compression Praagtieo of cycle
C. Pulse jet engine 3. Erickson Cycle
D. Gas turbine with multistage 4. Lenoir cycle compression and multistage expansion
Match List-I with List-II and select the correct answer using the codes given below the lists:
Assertion (A): In practice, the efficiency of diesel engines is higher than that of petrolengines.
Reason (R): For the same compression ratio, the efficiency of diesel cycle is higherthan that of Otto cycle.
Match List I (Cycles) with List II (Processes) and select the correct answer using the codes given below the Lists:
A gas turbine cycle with infinitely large number of stages during compressionand expansion approaches
In the case of a Diesel cycle, increasing the cut-off ratio will increase
Assertion (A): For a given compression ratio, the thermal efficiency of the Diesel cycle will be higher than that of the Otto cycle.
Reason(R): In the Diesel cycle, work is also delivered during heat addition.
Ans. (d) For same compression ratio Otto cycle has maximum efficiency.
The air standard efficiency of diesel cycle will be less than that of Otto cyclein the case of
Match List I with List II and select the correct answer using the codes given below the lists:
For the same compression ratio and the same heat input, the correctsequence of the increasing order of the thermal efficiencies of the givencycles is
Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because, in Otto cycle
Ans. (d) For same heat input and same compression ratio, in case of Otto cycle, efficiency in higher because the heat rejection is lower.
The correct sequence of the given four cycles on T-s plane in Figure (1), (2),(3), (4) is
Which one of the following hypothetical heat engine cycle represents maximum efficiency?
Work done by all cases is same =
= 800 units
Heat input for (a) and (c) is same = 700 x (5 - 1) = 280 units
Heat input for(b)is
= 1000 units
Heat input for(d)is
= 2000 units
∴ maximum when minimum heat input is case (b)
The correct sequence of the cycles given in the above T-S diagrams is
Stirling and Ericsson cycles are
In an air standard Otto cycle, r is the volume compression ratio and y is an adiabatic index (Cp/ Cv), the air standard p v efficiency is given by
Which one of the following p-T diagrams illustrates the Otto cycle of an ideal gas?
Thermodynamic cycle shown above on the temperature – entropy diagrampertains to which one of the following?
Ans. (a) 1-2 and 3-4 are isothermal process
2-3 and 4-1 may be isobaric or isochoric process
So this cycle may be Starling cycle of Ericsson cycle but steepness of the curve 2-3 and 1-4 is very high. Therefore we may say it is Starling cycle.
A cyclic heat engine does 50 kJ of work per cycle. If the efficiency of the heat engine is 75%, the heat rejected per cycle is
A solar energy based heat engine which receives 80 kJ of heat at 100 deg Cand rejects 70 kJ of heat to the ambient at 30 deg C is to be designed. The thermal efficiency of the heat engine is