Before you undertake the practice of Ujayi pranayama, you must have a good understanding of Udyana bandha.
For that reason, Ujayi breath should not be practiced before you can comfortably lengthen your breath in Visama Vritti pranayama.
In the Ujayi pranayama practice, Udyana bandha is held in during inhalation, so the abdomen is kept still and the breath goes up in the chest. This is somewhat similar to the Taoist practice of reverse abdominal breathing, but as Udyana bandha is also held tight on the exhalation, the abdomen doesn't moves out at any stage of the practice.
Ujayi breath is very energizing, and for this reason is often used in asana practice.