Advanced Liquid Natural Gas Onboard Storage System

摘要

Cummins Westport Incorporated (CWI) has designed and developed a liquefied natural gas (LNG) vehicle fuel system that includes a reciprocating pump with the cold end submerged in LNG contained in a vacuum-jacketed tank. This system was tested and analyzed under the U.S. Department of Energy (DOE) Advanced LNG Onboard Storage System (ALOSS) program. The pumped LNG fuel system developed by CWI and tested under the ALOSS program is a high-pressure system designed for application on Class 8 trucks powered by CWI's ISX G engine, which employs high-pressure direct injection (HPDI) technology. A general ALOSS program objective was to demonstrate the feasibility and advantages of a pumped LNG fuel system relative to on-vehicle fuel systems that require the LNG to be ''conditioned'' to saturation pressures that exceeds the engine fuel pressure requirements. These advantages include the capability to store more fuel mass in given-size vehicle and station tanks, and simpler lower-cost LNG refueling stations that do not require conditioning equipment. Pumped LNG vehicle fuel systems are an alternative to conditioned LNG systems for spark-ignition natural gas and port-injection dual-fuel engines (which typically require about 100 psi), and they are required for HPDI engines (which require over 3,000 psi). The ALOSS program demonstrated the feasibility of a pumped LNG vehicle fuel system and the advantages of this design relative to systems that require conditioning the LNG to a saturation pressure exceeding the engine fuel pressure requirement. LNG tanks mounted on test carts and the CWI engineering truck were repeatedly filled with LNG saturated at 20 to 30 psig. More fuel mass was stored in the vehicle tanks as well as the station tank, and no conditioning equipment was required at the fueling station. The ALOSS program also demonstrated the general viability and specific performance of the CWI pumped LNG fuel system design. The system tested as part of this program is designed to be used on Class 8 trucks with CWI ISX G HPDI engines. Extensive test cart and engineering truck tests of the pump demonstrated good durability and the high-pressure performance needed for HPDI application. The LNG tanks manufactured by Taylor-Wharton passed SAE J2343 Recommended Practice drop tests and accelerated road-load vibration tests. NER and hold-time tests produced highly consistent results. Additional tests confirmed the design adequacy of the liquid level sensor, vaporizer, ullage volume, and other fuel system components. While the testing work performed under this program focused on a high-pressure pumped LNG fuel system design, the results also validate the feasibility of a low-pressure pumped fuel system. A low-pressure pumped fuel system could incorporate various design refinements including a simpler and lighter-weight pump, which would decrease costs somewhat relative to a high-pressure system.