Application of the Schlieren Optical Visualization to Experimental Design of a Test Rig for Diesel Engine Combustion Analysis

Engine power and exhaust emissions result from the in-cylinder's fuel combustion process. The test rig for combustion visualization is one of the modern and specialized systems with high precision requirements. This research aims to design and fabricate a Constant Volume Combustion Chamber (CVCC) to investigate the combustion characteristics under various operating conditions such as fuel injection pressures, ambient pressures, ERG ratios, etc. This design concept depends on the diesel engine operating conditions with compression ratios of up to 26, fuel injection pressure in the range of 1600 bar; be the ability to combine the Z-type Schlieren optical method and high-speed camera to collect images of the combustion process. The strength of the structure was analyzed by ANSYS software with conditions of combustion pressure at 100 bar and 200 bar. This design was fabricated and experimented with the combustion conditions at ambient pressure of 42 bar, oxygen concentration of 21% after the pre-combustion phase, and fuel injection pressure of 800 bar, 1000 bar, and 1200 bar, respectively. The results revealed that the combustion chamber satisfied the durable requirement criteria, with the safety factor of 8.6 and 4.3 respectively under the mentioned simulating conditions. The leakage rate is negligible with 0.01% at an applied compression pressure of 80 bar in CVCC, approximately. The CVCC system can perform and record combustion process parameters at conditions similar to operating the diesel engine.