Effect of high compression ratio on improving thermal efficiency and NOx formation in jet plume controlled direct-injection near-zero emission hydrogen engines |
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Affiliation: | Research Center for High Efficiency Hydrogen Engine and Engine Tribology, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya, Tokyo 158-8557, Japan |
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Abstract: | The Plume Ignition and Combustion Concept (PCC) developed by the authors significantly reduced nitrogen oxide (NOx) emissions in a direct-injection hydrogen engine under high-load operation. With PCC, a rich fuel plume is ignited immediately after completion of injection in the latter half of the compression stroke to reduce NOx formation. Simultaneously, high thermal efficiency was also achieved by mitigating cooling losses through optimization of the jet configuration in the combustion chamber. This basic combustion concept was applied to burn lean mixture in combination with the optimized hydrogen jet configuration and the application of supercharging to recover the power output decline due to the use of a diluted mixture. As a result, a near-zero-emission-level engine has been achieved that simultaneously provides high thermal efficiency, high power output and low NOx emissions at a single-digit ppm level [1]. In this study, a high compression ratio was applied to improve thermal efficiency further by taking advantage of the characteristics of hydrogen fuel, especially its diluted mixture with a high anti-knock property. As a result, NOx emissions at a single-digit ppm level and gross indicated thermal efficiency of 52.5% were achieved while suppressing knocking at a compression ratio of 20:1 by optimizing the excess air ratio and injection timing, and increasing power output by supercharging. |
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Keywords: | Spark-ignition engine Hydrogen Hydrogen engine Direct injection Thermal efficiency High compression ratio BPF" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040d" }," $$" :[{" #name" :" text" ," _" :" Band Pass Filter CA" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040f" }," $$" :[{" #name" :" text" ," _" :" Crank Angle CR" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040h" }," $$" :[{" #name" :" text" ," _" :" Compression Ratio CPO" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040j" }," $$" :[{" #name" :" text" ," _" :" In-cylinder Pressure Oscillations HRR" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040l" }," $$" :[{" #name" :" text" ," _" :" Heat Release Rates Ig. T" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040n" }," $$" :[{" #name" :" text" ," _" :" Ignition Timing LFM" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040t" }," $$" :[{" #name" :" text" ," _" :" Laminor Flow Meter LPF" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040v" }," $$" :[{" #name" :" text" ," _" :" Low Pass Filter MFM" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040x" }," $$" :[{" #name" :" text" ," _" :" Mass Flow Meter NA" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040z" }," $$" :[{" #name" :" text" ," _" :" Natural Aspiration NHRR" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040er" }," $$" :[{" #name" :" text" ," _" :" Normalized Heat Release Rates PCC" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040ui" }," $$" :[{" #name" :" text" ," _" :" Plume Ignition and Combustion Concept Indicated Mean Effective Pressure Gross Indicated Mean Effective Pressure P/R" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040xo" }," $$" :[{" #name" :" text" ," _" :" Pressure Regulator R/E" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040xw" }," $$" :[{" #name" :" text" ," _" :" Rotary Encoder SC" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040vb" }," $$" :[{" #name" :" text" ," _" :" Supercharging SOI" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040nm" }," $$" :[{" #name" :" text" ," _" :" Start of Injection S/T" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040mk" }," $$" :[{" #name" :" text" ," _" :" Surge Tank T/D" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040mg" }," $$" :[{" #name" :" text" ," _" :" Transducer λ" },{" #name" :" keyword" ," $" :{" id" :" kwrd0040md" }," $$" :[{" #name" :" text" ," _" :" Excess Air Ratio Indicated Thermal Efficiency Gross Indicated Thermal Efficiency |
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