Hydrogen-compressed Natural Gas Research Articles

Effect of ignition timing retard strategy on NOx reduction in hydrogen-compressed natural gas blend engine with increased compression ratio

Hydrogen-compressed natural gas blend (HCNG) engines can extend the lean burn limit because of the wide flammability range of hydrogen. Lean combustion helps facilitate high efficiency and fundamentally reduces NOx emission. Increasing the compression ratio (CR) of an HCNG engine was reported to improve its thermal efficiency. However, the high risk of knock occurrence and the increase in NOx emission can hinder CR increase.To reduce NOx emission, an ignition timing retard strategy was considered for an HCNG engine with an increased CR. The thermal efficiency and emission characteristics at maximum power operation were investigated by retarding the ignition timing from minimum spark advance for best torque (MBT) timing. The results showed that the condition of HCNG30, a CR of 11.5, lambda of 1.8, and retarding the ignition timing by 10 CAD from the MBT timing could produce 2.0% higher thermal efficiency, 61.7% lower NOx emission, and 6.7% higher CH4 emission compared to the base CNG engine condition.

HCNG 엔진에서 압축비 변경에 따른 성능 및 노킹 특성 연구

온실가스인 CO₂ 배출을 줄이기 위한 연료로서 고효율 연소의 특성을 갖는 수소-천연가스 혼합연료(HCNG)가 유력한 미래 대체연료로서 주목받고 있다. 일반적으로 엔진에서의 압축비 상승은 효율 향상 및 이산화탄소 배출 저감을 위한 방법 중의 하나로서 HCNG 엔진에서도 고압축비의 적용이 효과적일 수 있으나, 수소의 높은 연소 속도 및 화염 온도로 인한 조기착화, 노킹 등의 이상연소는 엔진 부품의 파손 및 출력 저하를 초래할 수 있다. 본 연구는 HCNG 엔진에서 압축비를 변경하여 엔진 성능 및 노킹 특성을 분석하는데 목적이 있다. 기존의 CNG 엔진에 CNG 및 HCNG 연료를 적용하여 공기과잉률의 변화에 따른 연소 특성을 분석하고, 압축비 변경 후 엔진의 성능에 미치는 영향을 파악하였다.

Effect of mixer type on cylinder-to-cylinder variation and performance in hydrogen-natural gas blend fuel engine

Compressed natural gas (CNG) buses were adopted in urban areas as a promising alternative to diesel buses, which emitted plenty of harmful emissions. Although CNG can meet the current emission standards, satisfying the requirements of the next EURO-VI emission regulation without an additional peripheral device may be impossible. The use of a hydrogen-compressed natural gas (HCNG) blend can help achieve a reduction in automotive exhaust emissions as well as prepare for an upcoming hydrogen economy through the construction of hydrogen infrastructure. Moreover, an HCNG engine has higher thermal efficiency than a CNG engine, producing lesser harmful emissions.Cylinder-to-cylinder variation affects multicylinder engine operation and can considerably influence an HCNG engine because fuel composition and excess air ratio differences can contribute to cylinder-to-cylinder variations. In the present study, the effect of the mixer type on cylinder-to-cylinder variation and performance characteristics were investigated using an 11-L heavy-duty CNG engine fuelled with HCNG (CNG 70 vol%, hydrogen 30 vol%). A change in the mixer type does not affect the characteristics of cylinder-to-cylinder variation and the combustion stability of the HCNG engine. The efficiency of cylinders 1 and 6 is lower than that of the other cylinders because of the configuration of the cylinder in the in-line-type engine. The significant increase in the pressure drop under a wide open-throttle operating condition makes it difficult to satisfy the engine's specifications.

Hydrogen transportation in Delhi? Investigating the hydrogen-compressed natural gas (H-CNG) option

Given the success of Delhi’s CNG vehicle program, energy stakeholders are now investigating a transition to hydrogen-compressed natural gas (H-CNG) blends in the city. Past research has shown H-CNG can reduce tailpipe emissions of both criteria and greenhouse gas pollutants relative to diesel, CNG, and gasoline [1–3]. However, an unanswered question is how Delhi will satisfy the potential hydrogen demand in a sustainable manner. We conduct a techno-economic assessment of hydrogen production from gasification of the three most abundant agricultural residues near Delhi – rice straw, cotton stalk, mustard stalk – and find these residues could provide the city with up to 270,700 metric tons per year of hydrogen. This quantity far exceeds what is needed to run all existing CNG vehicles on 18%–82% H-CNG blends. The cost of each step of the biohydrogen supply chain is calculated and the total cost is estimated at 149.6 rupees ($3.39) per kg. Lastly, we show that the price of H-CNG at the pump would be roughly equivalent to CNG on a per mile basis.