Chapter 13 Exhaust Systems 287 Copyright Goodheart-Willcox Co., Inc. Figure 13-13 shows the unit, whose major components include an electronically controlled mechanical mixing unit (about the size of a shoe box) situated between the fuel filters and the injection pump. The injection pump pro- duces a consistent and uniform emulsion of diesel fuel and water. The percentage of water in the emulsion can be preset from 5% to more than 30%. An electronic control module (ECM) maintains this percentage as a function of fuel flow. The emulsion is created by shear forces between the fuel and the water in a pear-shaped vortex chamber inside the mixing unit. The diesel fuel forms a skin around the water droplets. When the emulsion is injected into the combustion chamber, the water droplets expand or sponta- neously evaporate, rupturing the fuel skin and dispersing it into much smaller droplets. This causes a significant reduc- tion in exhaust emissions by improving combustion effi- ciency and fuel atomization. It also increases the fuel’s fluid momentum and cools the combustion chamber’s flame zone. Diesel/water emulsion fuel is also available in premixed form. Catalytic Converter/Silencer The industrial application of a combination catalytic converter/silencer is shown in Figure 13-14. It provides simultaneous reduction of exhaust emissions and exhaust noise of diesel engines. It also controls particulates, elimi- nates odor, reduces carbon monoxide, and changes exhaust to almost clear. The unit is cylindrical in configuration and is larger than a common catalytic converter. The design of some units features a “catalyst portal” which provides quick access to the catalyst module. The catalyst substrate is made of stainless steel with chevron-shaped corrugations that form the cell structure. The catalyst module is strategically located where the sealing and mechanical support structure provides a large safety factor against damage by engine backfire. Air-fuel ratio control ensures a continuous high conversion rate and minimizes fuel cost. An automatic air-fuel ratio con- troller governs system balance and follows load changes. Mufflers The muffler is the primary component responsible for minimizing the harsh sound waves created as combustion gases are forced out of the cylinders through the exhaust ports. Figure 13-13. The major mixing component of the diesel/water emulsion system. (Harrier Inc.) Combination catalytic converter/silencer Catalyst portal Cooler Engine Figure 13-14. A catalytic converter/silencer unit is often used with stationary diesel engines. This unit has a catalyst portal. (Houston Industrial Systems)