Standard Article International J of Engine Research 1–11 Ó IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1468087419871858 journals.sagepub.com/home/jer A novel air management system for a large bore two-stroke naturally aspirated gas engine to reduce emissions Sreenivasa Rao Gubba 1 , Bhaskar Tamma 1 , Pejman Kazempoor 2,3 , Thomas J Hurley 4 , Mark A Patterson 4 and Grant Hartman 2 Abstract The oil and gas industry operates by reciprocating natural gas engines which must comply with regulated emission stan- dards for hazardous air pollutants, including NOx, CO, and volatile organic compounds (VOCs). These pollutants are regulated by Environmental Protection Agency, and each engine is regularly tested for compliance with national emission standards. A general emissions control strategy in combustion engines is to control the air-to-fuel ratio. However, sta- tionary reciprocating engines, especially two-stroke engines, rarely have any mechanisms to control air and fuel para- meters at various operating conditions. This article discusses a novel air management system that is invented to control the air-to-fuel ratio for a large bore two-stroke naturally aspirated gas engine, that is, AJAX TM brand model number 2802. The method can also be used for other engines with the same working principle. This novel air management system has been developed through comprehensive computational analyses of the gas exchange process inside the engine and is presented here. Pilot tests have also been conducted to validate the computational model results. The results show that this air management system can significantly reduce the engine emissions to the standard level at various operating conditions, including partial loads and speeds. In the case of VOCs emissions, up to a 75% reduction is observed. Keywords Low-load operation, volatile organic compounds, stationary reciprocating engine, two-stroke, computational fluid dynamics, air to fuel ratio, air management Date received: 07 May 2019; accepted: 17 July 2019 Introduction With the advent of shale gas as a new source for natural gas development, regulatory scrutiny has intensified in all aspects of natural gas production. Currently, com- panies must overcome numerous challenges from was- tewater disposal to emission compliance to retain their operational and social licenses to operate. The US Environmental Protection Agency (EPA) 1 has also established standards, called ‘‘New Source Performance Standards,’’ that are designed to reduce emissions from stationary reciprocating internal combustion engines. Emission reduction from reciprocating engines is of high priority to regulatory agencies due to their signifi- cant contribution to overall pollutant emissions. Reciprocating engines are used in a variety of applica- tions, including gas compression, gas gathering, lique- fied natural gas (LNG) plants, power generation, irrigation, and inert gas production. 2 The primary criteria pollutants from natural gas-fired reciprocating engines are nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs), also known as methane, non-methane, non-ethane hydro- carbons (NMNEHCs). NOx formation is mainly asso- ciated with temperature in the engine combustion chamber. The CO and VOCs emissions are primarily the result of incomplete combustion. Various emission 1 GE Global Research Center, Bangalore, India 2 Energy Innovation Center, Baker Hughes, a GE company, Oklahoma City, OK, USA 3 School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, USA 4 Baker Hughes, a GE company, Houston, TX, USA Corresponding author: Pejman Kazempoor, Energy Innovation Center, Baker Hughes, a GE Company, 300 NE 9th St., Oklahoma City, OK 73104, USA. Email: Pejman.kazempoor@bhge.com; pkazempoor@ou.edu