The ideal efficiency of a Brayton cycle without regeneration, with increase in pressure ratio will

In a Brayton cycle without regeneration, the ideal efficiency increases with an increase in pressure ratio.

The efficiency of a Brayton cycle without regeneration is given by:
η = 1 - (1/rk-1)
where η is the cycle efficiency, r is the pressure ratio (p_max/p_min), and k is the specific heat ratio.

As the pressure ratio increases, the denominator term (1/r^k-1) decreases, resulting in a higher efficiency.

Therefore, the correct option is Increase.