1. The document details the design of a can-type combustion chamber for producer gas fuel for commercial use with the objectives of passive heat recovery and an engineering model for testing. 2. Design requirements include the chamber being less than 1m long and 500mm in diameter with the heat recovery technique ensuring a 200K-300K exhaust temperature rise. 3. Performance estimates show heat recovery with cross pattern fins can increase exhaust temperature by 44% to 1200K, improving efficiency.