It all depends on the molar ratio of HCl:K2CO3 and the order of the addition of reagents.
If HCl is less than 1 mol to 1 mol of K2CO3 then at good mixing no CO2 will evolve.
K2CO3 + HCl = KHCO3 + KCl.
At a molar ratio of HCl>1 to 2, potassium carbonate will decompose with the evolution of CO2.
KHCO3 + HCl = KCl + H2O + CO2
This explanation applies to the addition of acid to carbonate.
In the reverse order of the addition of the reagent, potassium carbonate will decompose with the evolution of carbon dioxide until the molar ratio of HCl:K2CO3 will reach 2:1 or until the acid runs out.
K2CO3 + 2HCl = 2KCl + H2O + CO2
With excess potassium carbonate in a sealed vessel, the following reaction will occur:
CO2 + K2CO3 + H2O = 2KHCO3
Even such a simple reaction can be so complicated.