Aanalysis of an ideal Brayton cycle with regeneration:

Cycle consists of processes:

• Adiabatic compression in compressor (H-K) (1-2);

• Isobaric heat addition to the system in regenerator (K-A);

• Isobaric heat addition to the system in combustion chamber (A-Г);

• Adiabatic expansion in turbine (Г-T) (3-4);

• Isobaric heat rejection in regenerator (T-B);

• Isobaric heat rejection (B-H);

Fig.10. Scheme of the engine with regeneration

1- filter; 2- compressor of low pressure; 3- compressor of high pressure; 4- combustion chamber; 5- turbine of high pressure; 6- turbine of low pressure; 7- pump; 8- cock; 9- regenerator

Fig.11. p-v and T-S diagrams of cycle with regeneration

Efficiency of regeneration :

Parameters at the points H,K,Г,T are the same as in the basic cycle. Find parameters at points A and B:

;

;

p_A=p_к;

p_B=p_н;

;

;

Thermal efficiency of the cycle:

or

.

Analysis of the Brayton Cycle with an intercooling:

Intercooling is complete, when gas is cooled to initial temperature T_н.

Fig.12. p-v and T-s diagrams of cycle with intercooling

Fig.13. Cycle with intercooling

1- filter; 2- compressor of low pressure; 3- compressor of high pressure; 4- combustion chamber;

5- turbine of high pressure; 6- turbine of low pressure; 7- pump; 8- cock; 9- intercooler

Determination of air parameters at points C, D and K:

; ;

T_D=T_н; р_D=р_с; ;

; ; ;

Determination of change in entropy, enthalpy in processes:

Determination of work and heat in the processes:

q₁=c_p(T_г- T_к);

=c_P(T_H- T_T); =(z_com-1)c_p(T_D-T_c);

q₂= + =c_P(T_н - T_т)+(z_com-1)c_p(T_D-T_с);

w_exp= w_Г-T = c_p(T_г- T_т); w_сom=z_comc_p(T_к-T_н),

where T_г and T_т are temperatures in basic cycle.

Determination of net work and thermal efficiency of the cycle:

;

w_cycle= w_exp- w_c.

Analysis of the cycle with reheating:

Scheme of the engine is shown on the Fig.14.

Fig.14. Scheme of engine with reheating

1- filter; 2- compressor of low pressure; 3- compressor of high pressure; 4- main combustion chamber; 5,6- turbine; 7,11- pump; 8,10- cock; 9-additional combustion chamber

Fig.15. p-v and T-s diagrams cycle with reheating

Value of T_н, T_г, and T_к are taken from calculation of basic cycle.

Determination parameters of working medium at points Г₁, T and T₁:

_{; ;}

_; ;

_; p_т=р_н;

Determination of change in entropy and enthalpy in processes:

.

Determination of work and heat in processes:

=c_p(T_г-T_к); =(z_exp-1) c_р(T_г-T_г1);

q₁= + = c_p(T_г-T_к) + (z_exp-1)c_p(T_г-T_т1);

q₂=c_р (T_н-T_т);

w_c=w_H-K= c_p (T_к –T_н);

w_exp.=z_exp c_p (T_г-T_т1);

Determination of net work and thermal efficiency of the cycle:

;

w_cycle= w_exp- w_com;