Chapter 14 - Engines

Abstract

Drives based on engines (either through electric generators or directly connected) should be considered for virtually every water, storm water, and wastewater pumping station installation. This chapter provides an introduction to engine drives and their needs. Engines useful in pumping stations could be categorized by ignition, cycle, and configuration, along with engine combustion type or air/fuel ratio (either rich-burn or lean-burn). Based on ignition, engines could be subdivided into those using spark ignition and those using compression ignition. With spark ignition, the fuel charge is ignited by a spark arcing between two direct-current electrodes and compression ignition engines employ the heat generated by the compression of the fuel-air mixture to ignite the fuel charge. Stationary engines are available in both two- and four-stroke cycle designs. Two-stroke engines require a separate scavenging blower (usually powered from the engine accessory train) to remove exhaust gases from the cylinder and introduce combustion air into the cylinder. Stationary engines are available in either in-line or vee-block configurations. Spark-ignition engines could either be rich-burn or lean-burn engines depending on their air-to-fuel ratio. For ideal or perfect stoichiometric combustion, a spark-ignition engine fueled with natural gas requires about 16 kg (35 lb) of air for every kg (2.2 lb) of fuel. Stationary engines might be started using one of the stored-energy systems that include compressed air, electricity, or hydraulic fluid.