A Fractographic Investigation of a Failed Precombustion Chamber Nozzle from a Large Marine Diesel Engine

From 1998 until 2001 a series of engine failures occurred in a fleet of large marine diesel engines due to the failure of precombustion nozzles. The nozzles are screwed into the head of the engines and are held in place by a tightening torque and a high temperature ceramic adhesive. The preliminary findings of an engineering investigation after one such failure concluded that cracking occurred in the nozzle at the time of the installation, due to poor installation technique, and that this cracking resulted in the loss of tightening torque causing the nozzle to become loose. However, the investigation also recommended that fractography be undertaken to verify the cause of failure since this would influence the engineering solution. The current paper focuses on the fractography that was conducted on the failed nozzle to determine its mode of failure and provides a reminder of the importance of fractography in failure analysis.

Precombustion Chamber Design and Performance Studies for a Large Bore Natural Gas Engine

Precombustion chamber (PCC) ignition is a common method for extending the lean limit and reducing combustion variability in large bore (36–56 cm) natural gas engines. An important component that commonly fails and requires regular replacement, besides the spark plug, is the checkvalve. The checkvalve meters fuel flow into the PCC. In this program the use of an electronic valve for monitoring fuel to the PCC instead of the checkvalve is investigated. Metering the fuel into the PCC with an electronic valve provides a number of different options for improving performance in addition to the benefit of extended valve life. PCC nozzle design is also evaluated as a means for improving PCC and engine performance. Additionally, emissions formation in the PCC is evaluated through the use of a separate pressure transducer in the PCC and a fast sample valve that extracts gas from the PCC.

Optimization of a Non-Fueled Prechamber Ignition System for a Lean-Burn, Industrial Natural Gas Engine

A non-fueled prechamber ignition system was developed to provide for controlled and stable combustion to best support the goals of both Waukesha Engine and the ARES program. This paper will provide details and results of efforts undertaken in optimization of the following design aspects: tangential angle of prechamber orifice channels in relation to head-induced cylinder swirl, prechamber orifice diameter, prechamber volume (spark plug recess in precombustion chamber), and recession of the entire precombustion chamber into the cylinder head. A number of important conclusions will be verified and presented based on the development work done on a laboratory engine.

Effects of Diesel / Water Emulsion on Heat Flow and Thermal Loading in a Precombustion Chamber Diesel Engine

An experimental investigation has been carried out to study the effects of using water / diesel emulsion fuel in an indirect injection diesel engine on the heat flux crossing liner and cylinder head, thermal loading and metal temperature distribution. A single cylinder precombustion chamber diesel engine has been used in the present work. The engine was instrumented for performance, metal temperature and heat flux measurements. The pure gas oil fuel and different ratios of water / diesel emulsion were used and their effects on the heat flux level and the injector tip temperature are studied. Two correlation were found for the heat flux crossing the liner and the cylinder head at various water / diesel emulsion ratios, fuelling rate and thermocouple probe locations. It was found that the addition of water to diesel fuel, to control the nitrogen oxides emissions, has great influence on reducing die heat flux, the metal temperatures and thermal loading of combustion chamber components.

Emission Reductions Through Precombustion Chamber Design in a Natural Gas, Lean Burn Engine

A study was conducted to evaluate the effects of various precombustion chamber design, operating, and control parameters on the exhaust emissions of a natural gas engine. Analysis of the results showed that engine-out total hydrocarbons and oxides of nitrogen (NOx) can be reduced, relative to conventional methods, through prechamber design. More specifically, a novel staged prechamber yielded significant reductions in NOx and total hydrocarbon emissions by promoting stable prechamber and main chamber ignition under fuel-lean conditions. Precise fuel control was also critical when balancing low emissions and engine efficiency (i.e., fuel economy). The purpose of this paper is to identify and explain positive and deleterious effects of natural gas prechamber design on exhaust emissions.