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“Gas-to-liquids” catalytic conversion technologies show promise for liberating stranded natural gas reserves and for achieving energy diversity worldwide. Some gas-to-liquids products are used as transportation fuels and as blendstocks for upgrading crude-derived fuels. Methylal (CH3-O-CH2-O-CH3), also known as dimethoxymethane or DMM, is a gas-to-liquid chemical that has been evaluated for use as a diesel fuel component. Methylal contains 42% oxygen by weight and is soluble in diesel fuel. The physical and chemical properties of neat methylal and for blends of methylal in conventional diesel fuel are presented. Methylal was found to be more volatile than diesel fuel, and special precautions for distribution and fuel tank storage are discussed. Steady state engine tests were also performed using an unmodified Cummins B5.9 turbocharged diesel engine to examine the effect of methylal blend concentration on performance and emissions.

Cylinder head cracking has been an engine development problem since the first high Performance diesels were designed and manufactured in the early 20th century. Valve bridge cracking is a common failure mode that is very dependent on engine application and operating conditions. Cracking failures cause increased engine maintenance and downtime, costly part replacement and in rare cases catastrophic engine failure. Cylinder head cracking continues to be problematic for modern diesel engines as peak firing pressures increase to meet exhaust emissions legislation and BMEPs increase for improved power density. The root cause of cylinder head cracking is often difficult to diagnose due to large number of design, manufacturing and engine operational variables involved. This paper summarizes the methods, results and conclusions of a study to determine the root cause of cracking in cylinder heads of large diesel engines used for standby power generation in nuclear plants.

The duration of piston durability tests is often shortened by increasing mechanical and thermal engine loads and loading frequency. Such durability tests are useful for assessing the structural integrity of new piston designs, but test results are generally not indicative of the expected service life. Furthermore, improper test procedures can introduce illegitimate failure modes which are not present in actual service. Two aluminum pistons were analyzed to gain a fundamental understanding of piston response due to accelerated test loads. The influence of engine speed, fuel/air ratio, intake manifold pressure and crankcase oil temperature on piston fatigue life was studied. Guidelines were established to aid in developing a more effective durability test procedure for natural gas engine pistons.