Abstract
A rapid compression machine (RCM) test bench is developed in this study. The performance characterization and auto-ignition performance tests are conducted at an initial temperature of 293 K, a compression ratio of 9.5 to 16.5, a compressed temperature of 650 K to 850 K, a driving gas pressure range of 0.25 MPa to 0.7 MPa, an initial pressure of 0.04 MPa to 0.09 MPa, and a nitrogen dilution ratio of 35% to 65%. A new type of hydraulic piston is used to address the problem in which the hydraulic buffer adversely affects the rapid compression process. Auto-ignition performance tests of the RCM are then performed using a DME–O2–N2 mixture. The two-stage ignition delay and negative temperature coefficient (NTC) behavior of the mixture are observed. The effects of driving gas pressure, compression ratio, initial pressure, and nitrogen dilution ratio on the two-stage ignition delay are investigated. Results show that both the first-stage and overall ignition delays tend to increase with increasing driving gas pressure. The driving gas pressure within a certain range does not significantly influence the compressed pressure. With increasing compression ratio, the first-stage ignition delay is shortened, whereas the second-stage ignition delay is extended. With increasing initial pressure, both the first-stage and second-stage ignition delays are shortened. The second-stage ignition delay is shortened to a greater extent than that of the first-stage. With increasing nitrogen dilution ratio, the first-stage ignition delay is shortened, whereas the second-stage is extended. Thus, overall ignition delay presents different trends under various compression ratios and compressed pressure conditions.
Highlights
The increasingly serious energy crisis and environmental problems have lead to the pollution emissions of internal combustion (IC) engines to gain considerable attention
The slope and the hydraulic cylinder rear cover a sealed cavity when the hydraulic piston is at the bottom dead center (BDC), which results in a better starting effect when the piston and connecting rod assembly start to move forward
Dimethyl ether (DME)–O2–N2 mixture is provided to study the effects of the driving gas pressure, compression ratio, initial pressure, and nitrogen dilution ratio on the two-stage ignition delay
Summary
The increasingly serious energy crisis and environmental problems have lead to the pollution emissions of internal combustion (IC) engines to gain considerable attention. To gain a better understanding of the ignition and combustion characteristics of various types of fuels, scholars around the world have developed various experimental devices, such as a constant volume combustion bomb, shock tube, single cylinder test engine, and rapid compression machine (RCM). In the study of ignition delay time, RCM and shock tube are two of the most widely used facilities. As regards to the structural arrangement, RCM can be classified into the single axial compression type or opposed compression type [5,19]. The single axial compression RCM includes horizontal, vertical [13], and right-angled types [11,12,16]. For the study of chemical reaction kinetics, the experimental data obtained from RCM can facilitate the understanding of as well as verify and improve the detailed chemical reaction mechanism of fuels. By using auto-ignition performance tests, the influences of driving pressure, compression ratio (compressed temperature), and initial pressure (compressed pressure) on the two-stage ignition delay of the DME–O2–N2 mixture are investigated
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