The flame is composed of two sections, the outer section and the inner section called the mantle. The mantle should be very well defined and approx. one inch tall. From your pictures it appears that the burners themselves are stopped up hence not all openings along the burner are burning as noted by the open areas between the flames. If on natural gas you need to verify that the manifold gas pressure is set to 3.5" WC, but check the nameplate for proper setting, it could require 4"WC. Your unit heater is capable at full burn of approx 32K BTU/Hr output. Also if that is your drip/sediment trap right before the gas cock it is installed against code. The trap must be on the "Run" of the TEE, not the "Branch". More pictures of your setup would be helpful.